Synthesis of adenine-modified reduced graphene oxide nanosheets.

PubMed

Cao, Huaqiang; Wu, Xiaoming; Yin, Gui; Warner, Jamie H

2012-03-05

We report here a facile strategy to synthesize the nanocomposite of adenine-modified reduced graphene oxide (AMG) via reaction between adenine and GOCl which is generated from SOCl(2) reacted with graphite oxide (GO). The as-synthesized AMG was characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), UV-vis absorption spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and galvanostatic discharge analysis. The AMG owns about one adenine group per 53 carbon atoms on a graphene sheet, which improves electronic conductivity compared with reduced graphene oxide (RGO). The AMG displays enhanced supercapacitor performance compared with RGO accompanying good stability and good cycling behavior in the supercapacitor.

Adsorption of dodecylamine hydrochloride on graphene oxide in water

NASA Astrophysics Data System (ADS)

Chen, Peng; Li, Hongqiang; Song, Shaoxian; Weng, Xiaoqing; He, Dongsheng; Zhao, Yunliang

Cationic surfactants in water are difficult to be degraded, leading to serious water pollution. In this work, graphene oxide (GO) was used as an adsorbent for removing Dodecylamine Hydrochloride (DACl), a representative cationic surfactant. X-ray diffraction (XRD), FT-IR spectroscopy and atomic force microscope (AFM) were used to characterize the prepared GO. The adsorption of DACl on GO have been investigated through measurements of adsorption capacity, zeta potential, FTIR, and X-ray photoelectron spectroscopy (XPS). The experimental results have shown that the adsorption kinetics could be described as a rate-limiting pseudo second-order process, and the adsorption isotherm agreed well with the Freundlich model. GO was a good adsorbent for DACl removal, compared with coal fly ash and powdered activated carbon. The adsorption process was endothermic, and could be attributed to electrostatic interaction and hydrogen bonding between DACl and GO.

FT-IR, FT-Raman and UV-visible spectra of potassium 3-furoyltrifluoroborate salt

NASA Astrophysics Data System (ADS)

Iramain, Maximiliano A.; Davies, Lilian; Brandán, Silvia Antonia

2018-04-01

The potassium 3-furoyltrifluoroborate salt has been experimentally characterized by means of FT-IR, FT-Raman and UV-Visible spectroscopies. Here, the predicted FT-IR, FT-Raman and UV-visible spectra by using theoretical B3LYP/6-31G* and 6-311++G** calculations show very good correlations with the corresponding experimental ones. The solvation energies were predicted by using both levels of calculations. The NBO analyses reveal the high stability of the salt by using the B3LYP/6-31G* level of theory while the AIM studies evidence the ionic characteristics of the salt in both media. The strong blue colour observed on the K atom by using the molecular electrostatic potential mapped suggests that this region act as typical electrophilic site. The gap values have revealed that the salt in gas phase is more reactive than in solution, as was reported in the literature while, the F13⋯H6 interaction together with the Ksbnd O bond observed by the studies of their charges could probably modulate the reactivities of this salt in aqueous solution. The force fields were computed with the SQMFF methodology and the Molvib program to perform the complete vibrational analysis. Then, the 39 vibration normal modes classified as 26 A'+ 13 A″ were completely assigned and their force constants are also reported.

Evaluation of the structural, electronic, topological and vibrational properties of N-(3,4-dimethoxybenzyl)-hexadecanamide isolated from Maca (Lepidium meyenii) using different spectroscopic techniques

NASA Astrophysics Data System (ADS)

Chain, Fernando; Iramain, Maximiliano Alberto; Grau, Alfredo; Catalán, César A. N.; Brandán, Silvia Antonia

2017-01-01

N-(3,4-dimethoxybenzyl)-hexadecanamide (DMH) was characterized by using Fourier Transform infrared (FT-IR) and Raman (FT-Raman), Ultraviolet- Visible (UV-Visible) and Hydrogen and Carbon Nuclear Magnetic Resonance (1H and 13C NMR) spectroscopies. The structural, electronic, topological and vibrational properties were evaluated in gas phase and in n-hexane employing ONIOM and self-consistent force field (SCRF) calculations. The atomic charges, molecular electrostatic potentials, stabilization energies and topological properties of DMH were analyzed and compared with those calculated for N-(3,4-dimethoxybenzyl)-acetamide (DMA) in order to evaluate the effect of the side chain on the properties of DMH. The reactivity and behavior of this alkamide were predicted by using the gap energies and some descriptors. Force fields and the corresponding force constants were reported for DMA only in gas phase and n-hexane due to the high number of vibration normal modes showed by DMH, while the complete vibrational assignments are presented for DMA and both forms of DMH. The comparisons between the experimental FTIR, FT-Raman, UV-Visible and 1H and 13C NMR spectra with the corresponding theoretical ones showed a reasonable concordance.

Nanoscale investigation of the interaction of colistin with model phospholipid membranes by Langmuir technique, and combined infrared and force spectroscopies.

PubMed

Freudenthal, Oona; Quilès, Fabienne; Francius, Grégory; Wojszko, Kamila; Gorczyca, Marcelina; Korchowiec, Beata; Rogalska, Ewa

2016-11-01

Colistin (Polymyxin E), an antimicrobial peptide, is increasingly put forward as salvage for severe multidrug-resistant infections. Unfortunately, colistin is potentially toxic to mammalian cells. A better understanding of the interaction with specific components of the cell membranes may be helpful in controlling the factors that may enhance toxicity. Here, we report a physico-chemical study of model phospholipid (PL) mono- and bilayers exposed to colistin at different concentrations by Langmuir technique, atomic force microscopy (AFM) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). The effect of colistin on chosen PL monolayers was examined. Insights into the topographical and elastic changes in the PL bilayers within time after peptide injection are presented via AFM imaging and force spectra. Finally, changes in the PL bilayers' ATR-FTIR spectra as a function of time within three bilayer compositions, and the influence of colistin on their spectral fingerprint are examined together with the time-evolution of the Amide II and νCO band integrated intensity ratios. Our study reveals a great importance in the role of the PL composition as well as the peptide concentration on the action of colistin on PL model membranes. Copyright © 2016 Elsevier B.V. All rights reserved.

Spectroscopic (FT-IR and FT-Raman) investigation, first order hyperpolarizability, NBO, HOMO-LUMO and MEP analysis of 6-nitrochromone by ab initio and density functional theory calculations

NASA Astrophysics Data System (ADS)

Senthil kumar, J.; Jeyavijayan, S.; Arivazhagan, M.

2015-02-01

The vibrational spectral analysis is carried out using FT-Raman and FT-IR spectroscopy in the range 3500-50 cm-1 and 4000-400 cm-1, respectively, for 6-nitrochromone (6NC). The molecular structure, fundamental vibrational frequencies and intensity of the vibrational bands are interpreted with the aid of structure optimization and normal coordinates force field calculation based on ab initio HF and DFT gradient calculations employing the HF/6-311++G(d,p) and B3LYP/6-311++G(d,p) basis set. Stability of the molecule has been analyzed using NBO analysis. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Thermodynamic properties like entropy, heat capacity, zero-point energy and Mulliken's charge analysis have been calculated for the 6NC. The complete assignments were performed on the basis of total energy distribution (TED) of the vibrational modes with scaled quantum mechanical (SQM) method. The MEP map shows the negative potential sites are on oxygen atoms as well as the positive potential sites are around the hydrogen atoms.

Synthesis and characterization of poly(3-sulfopropylmethacrylate) brushes for potential antibacterial applications.

PubMed

Ramstedt, Madeleine; Cheng, Nan; Azzaroni, Omar; Mossialos, Dimitris; Mathieu, Hans Jörg; Huck, Wilhelm T S

2007-03-13

This article describes the aqueous atom transfer radical polymerization synthesis of poly(3-sulfopropylmethacrylate) brushes onto gold and Si/SiO2 surfaces in a controlled manner. The effect of Cu(I)/Cu(II) ratio was examined, and a quartz crystal microbalance was used to study the kinetics of the brush synthesis. The synthesized brushes displayed a thickness from a few nanometers to several hundred nanometers and were characterized using atomic force microscopy, ellipsometry, Fourier transform infrared spectroscopy (FTIR), contact angle measurements, and X-ray photoelectron spectroscopy (XPS). The as-synthesized sulfonate brushes had very good ion-exchange properties for the ions tested in this study, i.e., Na+, K+, Cu2+, and Ag+. FTIR and XPS show that the metal ions are coordinating to sulfonate moieties inside the brushes. The brushes were easily loaded with silver ions, and the effect of silver ion concentration on silver loading of the brush was examined. The silver-loaded brushes were shown to be antibacterial toward both gram negative and gram positive bacteria. The silver leaching was studied through leaching experiments into water, NaNO3, and NaCl (physiological medium). The results from these leaching experiments are compared and discussed in the article.

Enhanced electrical properties in sub-10-nm WO3 nanoflakes prepared via a two-step sol-gel-exfoliation method

PubMed Central

2014-01-01

The morphology and electrical properties of orthorhombic β-WO3 nanoflakes with thickness of ~7 to 9 nm were investigated at the nanoscale with a combination of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), current sensing force spectroscopy atomic force microscopy (CSFS-AFM, or PeakForce TUNA™), Fourier transform infra-red absorption spectroscopy (FTIR), linear sweep voltammetry (LSV) and Raman spectroscopy techniques. CSFS-AFM analysis established good correlation between the topography of the developed nanostructures and various features of WO3 nanoflakes synthesized via a two-step sol-gel-exfoliation method. It was determined that β-WO3 nanoflakes annealed at 550°C possess distinguished and exceptional thickness-dependent properties in comparison with the bulk, micro and nanostructured WO3 synthesized at alternative temperatures. PMID:25221453

Nanomaterials from bacterial cellulose for antimicrobial wound dressing

NASA Astrophysics Data System (ADS)

Liyaskina, E.; Revin, V.; Paramonova, E.; Nazarkina, M.; Pestov, N.; Revina, N.; Kolesnikova, S.

2017-01-01

Bacterial nanocellulose (BNC) is widely used in biomedical applications. BNC has attracted increasing attention as a novel wound dressing material, but it has no antimicrobial activity. To get over this problem in the present study the BNC was saturated with antibiotic fusidic acid (FA). The subject of the experiment was BNC, produced by bacteria Gluconacetobacter sucrofermentans B-11267. The resulting biocomposites have high antibiotic activity against Staphylococcus aureus and can be used in medicine as a wound dressing. The structure of BNC was analyzed by atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR).

Vertical Alignment of Single-Walled Carbon Nanotubes on Nanostructure Fabricated by Atomic Force Microscope

DTIC Science & Technology

2007-05-01

SWNTs by blending them with liquid crystal,7 assem- bling SWNT films by Langmuir - Blodgett methods,8 and chemical assembly of SWNTs on a large substrate...Ulman, A. An Introduction to Ultrathin Organic Films from Langmuir - Blodgett to Self-Assembly. Academic: New York, (1991). [10] Moon, J.H., Shin, J.W...Fang, J. Langmuir , 16, 2651, (2000). [8] FT-IR data (Bruker IFS48, KBr Pellet): 1720 cm-1 (νC=O, SWNT-COOH) and 1770 cm-1 (νC=O, SWNT- COCl). [9

Application of argon atmospheric cold plasma for indium tin oxide (ITO) based diodes

NASA Astrophysics Data System (ADS)

Akbari Nia, S.; Jalili, Y. Seyed; Salar Elahi, A.

2017-09-01

Transparent Conductive Oxide (TCO) layers due to transparency, high conductivity and hole injection capability have attracted a lot of attention. One of these layers is Indium Tin Oxide (ITO). ITO due to low resistance, transparency in the visible spectrum and its proper work function is widely used in the manufacture of organic light emitting diodes and solar cells. One way for improving the ITO surface is plasma treatment. In this paper, changes in surface morphology, by applying argon atmospheric pressure cold plasma, was studied through Atomic Force Microscopic (AFM) image analysis and Fourier Transform Infrared Spectroscopy (FTIR) analysis. FTIR analysis showed functional groups were not added or removed, but chemical bond angle and bonds strength on the surface were changed and also AFM images showed that surface roughness was increased. These factors lead to the production of diodes with enhanced Ohmic contact and injection mechanism which are more appropriate in industrial applications.

Spectroscopic and microscopic characterization of silver nanoparticles synthesized using Justicia adhatoda flower

NASA Astrophysics Data System (ADS)

Singh, Tej; Shekhawat, Dharmender Singh; Jyoti, Kumari

2018-05-01

The synthesis of silver nanoparticles (SNPs) by chemical and physical methods produce harmful products which may cause various environmental problems, thus, there is an increasing demand to use ecofriendly methods. Therefore, biosynthesis of SNPs using Justicia adhatoda flower extract is demonstrated in the present study. The biosynthesized SNPs were characterized by UV-visible spectroscopy, Fourier transform-infrared spectroscopy (FTIR), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and atomic force microscopy (AFM) analysis. The result of UV-visible spectroscopy peaked at 417 nm corresponding to the plasmon absorbance of SNPs. The TEM and SAED result reveals the crystalline nature of SNPs. FTIR spectroscopy used to identify the possible biomolecules responsible for the conversion of silver ions to SNPs. The study concluded that Justicia adhatoda flower extract act as an excellent reducing agent and the green synthesized SNPs are safer to the environment.

Investigation on the adsorption characteristics of sodium benzoate and taurine on gold nanoparticle film by ATR-FTIR spectroscopy

NASA Astrophysics Data System (ADS)

Kumar, Naveen; Thomas, S.; Tokas, R. B.; Kshirsagar, R. J.

2014-01-01

Fourier transform infrared (FTIR) spectroscopic studies of sodium benzoate and taurine adsorbed on gold nanoparticle (AuNp) film on silanised glass slides have been studied by attenuated total reflection technique (ATR). The surface morphology of the AuNp films has been measured by Atomic Force Microscopy. The ATR spectra of sodium benzoate and taurine deposited on AuNp film are compared with ATR spectra of their powdered bulk samples. A new red-shifted band appeared along with the symmetric and asymmetric stretches of carboxylate group of sodium benzoate leading to a broadening of the above peaks. Similar behavior is also seen in the case of symmetric and asymmetric stretches of sulphonate group of taurine. The results indicate presence of both chemisorbed and physisorbed layers of both sodium benzoate and taurine on the AuNp film with bottom layer chemically bound to AuNp through carboxylate and sulphonate groups respectively.

Biosynthesis of palladium nanoparticles using Saccharomyces cerevisiae extract and its photocatalytic degradation behaviour

NASA Astrophysics Data System (ADS)

Sriramulu, Mohana; Sumathi, Shanmugam

2018-06-01

In this article, we have discussed the biosynthesis of palladium nanoparticles (PdNPs) using aqueous Saccharomyces cerevisiae extract and its photocatalytic application. The biosynthesised PdNPs were characterised by UV-Vis spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX) and Atomic force microscopy (AFM). The formation of PdNPs was confirmed from the disappearance of the peak at 405 nm in the UV-Vis spectrum. Agglomerated and hexagonal shaped PdNPs were noted by SEM. FTIR was performed to identify the biomolecules responsible for the synthesis of PdNPs. Bioactive compounds in the yeast extract acted as secondary metabolites which facilitated the formation of PdNPs. The yeast synthesised PdNPs degraded 98% of direct blue 71 dye photochemically within 60 min under UV light.

Selective depression of titanaugite in the ilmenite flotation with carboxymethyl starch

NASA Astrophysics Data System (ADS)

Meng, Qingyou; Yuan, Zhitao; Yu, Li; Xu, Yuankai; Du, Yusheng; Zhang, Chen

2018-05-01

In order to intensify the flotation separation of ilmenite from titanaugite, surface modification of mineral particles was carried out using carboxymethyl starch (CMS) by microflotation experiments, zeta potential measurements, Fourier transform infrared (FTIR) and atomic force microscopy (AFM) analysis. Microflotation results showed that CMS was a selective depressant, and it effectively enhanced the floatability difference between ilmenite and titanaugite in the pH range from 6.0 to 10.0. As it was revealed by the zeta potential, FTIR and AFM analysis, the CMS adsorption occurred onto mineral surfaces through chemisorption and hydrogen bonding, while CMS exhibited a stronger interaction with titanaugite than ilmenite. After that, the CMS adsorption impeded the adsorption of sodium oleate collector on titanaugite surfaces, giving rise to a concomitant decrease in the floatability of titanaugite. These findings exhibit great potential for CMS application in the selective flotation of ilmenite.

Interactions at the mild steel acid solution interface in the presence of O-fumaryl-chitosan: Electrochemical and surface studies.

PubMed

Sangeetha, Y; Meenakshi, S; Sundaram, C Sairam

2016-01-20

The performance of synthesised O-fumaryl-chitosan (OFC) as corrosion inhibitor for mild steel in 1M HCl has been evaluated through various studies. The initial screening by weight loss method revealed the good inhibition efficiency by the inhibitor. Thermodynamic and kinetic parameters have been calculated and discussed. The mode of adsorption is physical in nature and it follows Langmuir adsorption isotherm. Electrochemical measurements supported the inhibition of mild steel by the fumaryl derivative of chitosan. Polarisation studies provided the information that the inhibition is of mixed type. The formation of inhibitor film is assured by surface morphological studies with Scanning electron microscopy (SEM) and Atomic force microscopy (AFM). The mechanism of inhibition is derived from the Fourier-transform infrared (FTIR) spectroscopy and zero charge potential measurement. The adsorbed film is characterised using FTIR and X-ray diffraction studies (XRD). Copyright © 2015 Elsevier Ltd. All rights reserved.

Surface grafting of Corchorus olitorius fibre: a green approach for the development of activated bioadsorbent.

PubMed

Roy, Aparna; Chakraborty, Sumit; Kundu, Sarada Prasad; Majumder, Subhasish Basu; Adhikari, Basudam

2013-02-15

The present work is an endeavor to prepare lignocellulosic biomass based adsorbent, suitable for removal of organic and inorganic pollutants from industrial effluents. Lignocellulosic Corchorus olitorius fibre (jute fibre) surface was grafted with naturally available polyphenol, tannin, preceded by the epoxy-activation of fibre surface with epichlorohydrin under mild condition in an aqueous suspension. The reaction parameters for the modification, viz., concentration of epichlorohydrin and tannin, time, and temperature were optimized. The successful occurrence of surface modification of jute fibre (JF) was characterized and estimated from weight gain percent, elemental analysis, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, scanning electron and atomic force microscopy, and thermogravimetric analysis. An extensive analysis of deconvoluted FTIR spectra using the Voigt model was utilized to ensure the surface grafting. The microbiological susceptibility study revealed high persistency of JF towards biodegradation after efficient grafting with tannin. Copyright © 2012 Elsevier Ltd. All rights reserved.

Hydration induced material transfer in membranes of osmotic pump tablets measured by synchrotron radiation based FTIR.

PubMed

Wu, Li; Yin, Xianzhen; Guo, Zhen; Tong, Yajun; Feng, Jing; York, Peter; Xiao, Tiqiao; Chen, Min; Gu, Jingkai; Zhang, Jiwen

2016-03-10

Osmotic pump tablets are reliable oral controlled drug delivery systems based on their semipermeable membrane coating. This research used synchrotron radiation-based Fourier transform infrared (SR-FTIR) microspectroscopy and imaging to investigate the hydration induced material transfer in the membranes of osmotic pump tablets. SR-FTIR was applied to record and map the chemical information of a micro-region of the membranes, composed of cellulose acetate (CA, as the water insoluble matrix) and polyethylene glycol (PEG, as the soluble pore forming agent and plasticizing agent). The microstructure and chemical change of membranes hydrated for 0, 5, 10 and 30min were measured using SR-FTIR, combined with scanning electronic microscopy and atom force microscopy. The SR-FTIR microspectroscopy results indicated that there was a major change at the absorption range of 2700-3100cm(-1) in the membranes after different periods of hydration time. The absorption bands at 2870-2880cm(-1) and 2950-2960cm(-1) were assigned to represent CA and PEG, respectively. The chemical group signal distribution illustrated by the ratio of PEG to CA demonstrated that the trigger of drug release in the preliminary stage was due to the rapid transfer of PEG into liquid medium with a sharp decrease of PEG in the membranes. The SR-FTIR mapping results have demonstrated the hydration induced material transfer in the membranes of osmotic pump tablets and enabled reassessment of the drug release mechanism of membrane controlled osmotic pump systems. Copyright © 2016 Elsevier B.V. All rights reserved.

Effect of cation-anion interactions on the structural and vibrational properties of 1-buthyl-3-methyl imidazolium nitrate ionic liquid

NASA Astrophysics Data System (ADS)

Kausteklis, Jonas; Aleksa, Valdemaras; Iramain, Maximiliano A.; Brandán, Silvia Antonia

2018-07-01

The cation-anion interactions present in the 1-butyl-3-methylimidazolium nitrate ionic liquid [BMIm][NO3] were studied by using density functional theory (DFT) calculations and the experimental FT-Raman spectrum in liquid phase and its available FT-IR spectrum. For the three most stable conformers found in the potential energy surface and their 1-butyl-3-methylimidazolium [BMIm] cation, the atomic charges, molecular electrostatic potentials, stabilization energies, bond orders and topological properties were computed by using NBO and AIM calculations and the hybrid B3LYP level of theory with the 6-31G* and 6-311++G** basis sets. The force fields, force constants and complete vibrational assignments were also reported for those species by using their internal coordinates and the scaled quantum mechanical force field (SQMFF) approach. The dimeric species of [BMIm][NO3] were also considered because their presence could probably explain the most intense bands observed at 1344 and 1042 cm-1 in both experimental FT-IR and FT-Raman spectra, respectively. The geometrical parameters suggest monodentate cation-anion coordination while the studies by charges, NBO and AIM calculations support bidentate coordinations between those two species. Additionally several quantum chemical descriptors were also calculated in order to interpret various molecular properties such as electronic structure, reactivity of those species and predict their gas phase behaviours.

Thiolated poly(ɛ-caprolactone) macroligand with vacant coordination sites on gold substrate: Synthesis and surface characterization

NASA Astrophysics Data System (ADS)

Farah, Abdiaziz A.; Zheng, Susan H.; Morin, Sylvie; Bensebaa, Farid; Pietro, William J.

2007-04-01

Surface-confined telechelic poly(ɛ-caprolactone) macroligand with two distinct functional groups per polymeric chain has been synthesized and characterized. The molecular microstructure of the macroligand with regard to the properties of the end-capped functionalities and with those on surface substrate has been studied by solution and surface analytical methods (i.e., X-ray photoelectron spectroscopy (XPS), grazing angle reflectance-Fourier transform IR spectroscopy (GA-FTIR), water contact angle measurements, and atomic force microscopy (AFM)) to elucidate the structure and properties of such multifunctional polymer on gold (1 1 1) substrate.

Diamond-coated ATR prism for infrared absorption spectroscopy of surface-modified diamond nanoparticles

NASA Astrophysics Data System (ADS)

Remes, Z.; Kozak, H.; Rezek, B.; Ukraintsev, E.; Babchenko, O.; Kromka, A.; Girard, H. A.; Arnault, J.-C.; Bergonzo, P.

2013-04-01

Linear antenna microwave chemical vapor deposition process was used to homogeneously coat a 7 cm long silicon prism by 85 nm thin nanocrystalline diamond (NCD) layer. To show the advantages of the NCD-coated prism for attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) of nanoparticles, we apply diamond nanoparticles (DNPs) of 5 nm nominal size with various surface modifications by a drop-casting of their methanol dispersions. ATR-FTIR spectra of as-received, air-annealed, plasma-oxidized, and plasma-hydrogenated DNPs were measured in the 4000-1500 cm-1 spectral range. The spectra show high spectral resolution, high sensitivity to specific DNP surface moieties, and repeatability. The NCD coating provides mechanical protection against scratching and chemical stability of the surface. Moreover, unlike on bare Si surface, NCD hydrophilic properties enable optically homogeneous coverage by DNPs with some aggregation on submicron scale as evidenced by scanning electron microscopy and atomic force microscopy. Compared to transmission FTIR regime with KBr pellets, direct and uniform deposition of DNPs on NCD-ATR prism significantly simplifies and speeds up the analysis (from days to minutes). We discuss prospects for in situ monitoring of surface modifications and molecular grafting.

Structure of Co-Doped Alq3 thin films investigated by grazing incidence X-ray absorption fine structure and Fourier transform infrared spectroscopy.

PubMed

Lin, Liang; Pang, Zhiyong; Fang, Shaojie; Wang, Fenggong; Song, Shumei; Huang, Yuying; Wei, Xiangjun; Yu, Haisheng; Han, Shenghao

2011-02-10

The structural properties of Co-doped tris(8-hydroxyquinoline)aluminum (Alq(3)) have been studied by grazing incidence X-ray absorption fine structure (GIXAFS) and Fourier transform infrared spectroscopy (FTIR). GIXAFS analysis suggests that there are multivalent Co-Alq(3) complexes and the doped Co atoms tend to locate at the attraction center with respect to N and O atoms and bond with them. The FTIR spectra indicate that the Co atoms interact with the meridional (mer) isomer of Alq(3) rather than forming inorganic compounds.

Structural characterization of Papilio kotzebuea (Eschscholtz 1821) butterfly wings

NASA Astrophysics Data System (ADS)

Sackey, J.; Nuru, Z. Y.; Berthier, S.; Maaza, M.

2018-05-01

The `plain black' forewings and black with `red spot' hindwings of the Papilio kotzebuea (Eschscholtz, 1821) were characterized by Scanning Electron Microscopy (SEM), Energy-Dispersive x-ray Spectroscopy (EDS), Atomic Force Microscopy (AFM), Fourier transform Infrared spectroscopy (FT-IR), UV-Vis spectrophometer and NIRQuest spectrometer. SEM images showed that the two sections of wings have different structures. The black with `red spot' hindwings have `hair-like' structures attached to the ridges and connected to the lamellae. On the contrary, the `plain black' forewings have holes that separate the ridges. AFM analysis unveiled that the `plain black' forewings have higher average surfaces roughness values as compared with the black with `red spot' hindwing. EDS and FT-IR results confirmed the presence of naturally hydrophobic materials on the wings. The `plain black' forewing exhibited strong absorptance (97%) throughout the solar spectrum range, which is attributed to the high melanin concentration as well as to the presence of holes in the scales. Biomimicking this wing could serves as equivalent solar absorber material.

Characterization of lignin during oxidative and hydrothermal pre-treatment processes of wheat straw and corn stover.

PubMed

Kaparaju, Prasad; Felby, Claus

2010-05-01

The objective of the study was to characterize and map changes in lignin during hydrothermal and wet explosion pre-treatments of wheat straw and corn stover. Chemical composition, microscopic (atomic force microscopy and scanning electron microscopy) and spectroscopic (attenuated total reflectance Fourier transform infrared spectroscopy, ATR-FTIR) analyses were performed. Results showed that both pre-treatments improved the cellulose and lignin content with substantial removal of hemicellulose in the pre-treated biomasses. These values were slightly higher for hydrothermal compared to wet explosion pre-treatment. ATR-FTIR analyses also confirmed these results. Microscopic analysis showed that pre-treatments affected the biomass by partial difibration. Lignin deposition on the surface of the hydrothermally pre-treated fibre was very distinct while severe loss of fibril integrity was noticed with wet exploded fibre. The present study thus revealed that the lignin cannot be removed by the studied pre-treatments. However, both pre-treatments improved the accessibility of the biomass towards enzymatic hydrolysis. Copyright 2009 Elsevier Ltd. All rights reserved.

C sbnd H…F hydrogen bonds as the organising force in F-substituted α-phenyl cinnamic acid aggregates studied by the combination of FTIR spectroscopy and computations

NASA Astrophysics Data System (ADS)

Tolnai, B.; Kiss, J. T.; Felföldi, K.; Pálinkó, I.

2009-04-01

Various F-substituted E-2,3-diphenyl propenoic acid molecules were synthesised and their aggregation behaviour was studied by experimental (FT-IR spectroscopy) and computational (semiempirical and DFT) methods. Experimental approach embraced the identification of potential hydrogen bonding sites through finding the relevant IR bands and monitoring their shifts upon increasing the acid concentration and on going to the solid state. It was found that fluorine engaged in C sbnd H…F hydrogen bonding easily, where the carbon atom could be of any kind available in the molecule (aromatic, aliphatic or olefinic). Shifts were found even in moderately concentrated solutions and in the solid state too. Hydrogen bonding sites could be assigned and relevant aggregate models could be built. Molecular modelling allowed obtaining good estimates for hydrogen bond lengths and angles and visualisation of the geometric arrangements even of extended networks also became feasible.

Investigation on the adsorption characteristics of sodium benzoate and taurine on gold nanoparticle film by ATR-FTIR spectroscopy.

PubMed

Kumar, Naveen; Thomas, S; Tokas, R B; Kshirsagar, R J

2014-01-24

Fourier transform infrared (FTIR) spectroscopic studies of sodium benzoate and taurine adsorbed on gold nanoparticle (AuNp) film on silanised glass slides have been studied by attenuated total reflection technique (ATR). The surface morphology of the AuNp films has been measured by Atomic Force Microscopy. The ATR spectra of sodium benzoate and taurine deposited on AuNp film are compared with ATR spectra of their powdered bulk samples. A new red-shifted band appeared along with the symmetric and asymmetric stretches of carboxylate group of sodium benzoate leading to a broadening of the above peaks. Similar behavior is also seen in the case of symmetric and asymmetric stretches of sulphonate group of taurine. The results indicate presence of both chemisorbed and physisorbed layers of both sodium benzoate and taurine on the AuNp film with bottom layer chemically bound to AuNp through carboxylate and sulphonate groups respectively. Copyright © 2013 Elsevier B.V. All rights reserved.

Structural changes of a-CNx thin films induced by thermal annealing

NASA Astrophysics Data System (ADS)

Aziz, Siti Aisyah Abd; Awang, Rozidawati

2018-04-01

In this work, amorphous carbon nitride (a-CNx) thin films were deposited by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) technique at different RF powers of 60, 70, 80, 90 and 100 W for 30 min. These films were prepared using a mixture of acetylene (C2H2) at 20 sccm and nitrogen (N2) gases at 50 sccm. The films were then annealed at 400 °C in a quartz tube furnace in argon (Ar) gas. The chemical bondings of the film were analyzed by Fourier Transform Infra-red Spectroscopy (FTIR) while surface morphology and film roughness were determined by Atomic Force Microscopy (AFM). The FTIR analysis reveals that annealing resulted in the loss of C-H and C-N bonds and formation of graphitic sp2C cluster with the dissociation of N and C in the films. AFM indicates that the film surface becomes less rough which effectually enhances structural modifications and the rearrangement of the microstructure of the films after annealing.

Synthesis of gold nanoparticles with graphene oxide.

PubMed

Wang, Wenshuo; He, Dawei; Zhang, Xiqing; Duan, Jiahua; Wu, Hongpeng; Xu, Haiteng; Wang, Yongsheng

2014-05-01

Single sheets of functionalized graphene oxide are derived through chemical exfoliation of natural flake graphite. We present an effective synthetic method of graphene-gold nanoparticles hybrid nanocomposites. AFM (Atomic Force Microscope) was used to measure the thickness of the individual GO nanosheet. FTIR (Fourier transform infrared) spectroscopy was used to verify the attachment of oxygen functionalities on the surface of graphene oxide. TEM (Transmission Electron Microscope) data revealed the average diameters of the gold colloids and characterized the composite particles situation. Absorption spectroscopy showed that before and after synthesis the gold particle size did not change. Our studies indicate that the hybrid is potential substrates for catalysts and biosensors.

Preparation and performance of broadband antireflective sub-wavelength structures on Ge substrate

NASA Astrophysics Data System (ADS)

Shen, Xiang-Wei; Liu, Zheng-Tang; Li, Yang-Ping; Lu, Hong-Cheng; Xu, Qi-Yuan; Liu, Wen-Ting

2009-01-01

Sub-wavelength structures (SWS) were prepared on Ge substrates through photolithography and reactive ion etching (RIE) technology for broadband antireflective purposes in the long wave infrared (LWIR) waveband of 8-12 μm. Topography of the etched patterns was observed using high resolution optical microscope and atomic force microscope (AFM). Infrared transmission performance of the SWS was investigated by Fourier transform infrared (FTIR) spectrometer. Results show that the etched patterns were of high uniformity and fidelity, the SWS exhibited a good broadband antireflective performance with the increment of the average transmittance which is over 8-12 μm up to 8%.

Nanostructure and Dynamics of Ionic and Non-Ionic PEO-Containing Polyureas

NASA Astrophysics Data System (ADS)

Chuayprakong, Sunanta; Runt, James

2013-03-01

A series of polyethylene oxide (PEO) - based diamines with molecular weights ranging from 250 - 6000 g/mol were polymerized in solution with 4,4'-methylene diphenyl diisocyanate (MDI). In addition, PEO soft segment diamines where modified to incorporate ionomeric species and also polymerized with MDI. The role of PEO soft segment molecular weight and the presence of ionic species on nanoscale segregation and cation conductivity were explored. The former was investigated using small-angle X-ray scattering and atomic force microscopy. Dielectric relaxation spectroscopy was used to investigate polymer and ion dynamics. Local environment and hydrogen bonding were identified by using FTIR spectroscopy.

Insights into the relation between adhesion force and chalcopyrite-bioleaching by Acidithiobacillus ferrooxidans.

PubMed

Zhu, Jianyu; Wang, Qianfen; Zhou, Shuang; Li, Qian; Gan, Min; Jiang, Hao; Qin, Wenqing; Liu, Xueduan; Hu, Yuehua; Qiu, Guanzhou

2015-02-01

This paper presents a study on the relation between bacterial adhesion force and bioleaching rate of chalcopyrite, which sheds light on the influence of interfacial interaction on bioleaching behavior. In our research, Acidithiobacillus ferrooxidans (A. ferrooxidans) were adapted to grow with FeSO4 · 7H2O, element sulfur or chalcopyrite. Then, surface properties of Acidithiobacillus ferrooxidans and chalcopyrite were analyzed by contact angle, zeta potential and Fourier transform infrared spectroscopy (FTIR). Adhesion force between bacteria and chalcopyrite was measured by atomic force microscopy (AFM). Attachment and bioleaching behaviors were also monitored. The results showed that A. ferrooxidans adapted with chalcopyrite exhibited the strongest adhesion force to chalcopyrite and the highest bioleaching rate. Culture adapted with sulfur bacteria took second place and FeSO4 · 7H2O-adapted bacteria were the lowest. Bioleaching rate and bacterial attachment capacity were positively related to bacterial adhesion force, which is affected by the nature of energy source. According to this work, the attachment of bacteria to chalcopyrite surface is one of the most important aspects that influence the bioleaching process of chalcopyrite. Copyright © 2014 Elsevier B.V. All rights reserved.

A Study of the Applicability of Atomic Emission Spectroscopy (AES), Fourier Transform Infrared (FT-IR) Spectroscopy, Direct Reading and Analytical Ferrography on High Performance Aircraft Engine Lubricating Oils

DTIC Science & Technology

1998-01-01

Ferrography on High Performance Aircraft Engine Lubricating Oils Allison M. Toms, Sharon 0. Hem, Tim Yarborough Joint Oil Analysis Program Technical...turbine engines by spectroscopy (AES and FT-IR) and direct reading and analytical ferrography . A statistical analysis of the data collected is...presented. Key Words: Analytical ferrography ; atomic emission spectroscopy; condition monitoring; direct reading ferrography ; Fourier transform infrared

Preparation of polystyrene brush film by radical chain-transfer polymerization and micromechanical properties

NASA Astrophysics Data System (ADS)

Zhao, Jing; Chen, Miao; An, Yanqing; Liu, Jianxi; Yan, Fengyuan

2008-12-01

A radical chain-transfer polymerization technique has been applied to graft-polymerize brushes of polystyrene (PSt) on single-crystal silicon substrates. 3-Mercapto-propyltrimethoxysilane (MPTMS), as a chain-transfer agent for grafting, was immobilized on the silicon surface by a self-assembling process. The structure and morphology of the graft-functionalized silicon surfaces were characterized by the means of contact-angle measurement, ellipsometric thickness measurement, Fourier transformation infrared (FTIR) spectroscopy, and atomic force microscopy (AFM). The nanotribological and micromechanical properties of the as-prepared polymer brush films were investigated by frictional force microscopy (FFM), force-volume analysis and scratch test. The results indicate that the friction properties of the grafted polymer films can be improved significantly by the treatment of toluene, and the chemically bonded polystyrene film exhibits superior scratch resistance behavior compared with the spin-coated polystyrene film. The resultant polystyrene brush film is expected to develop as a potential lubrication coating for microelectromechanical systems (MEMS).

Optimized Model Surfaces for Advanced Atomic Force Microscopy Studies of Surface Nanobubbles.

PubMed

Song, Bo; Zhou, Yi; Schönherr, Holger

2016-11-01

The formation of self-assembled monolayers (SAMs) of binary mixtures of 16-mercaptohexadecanoic acid (MHDA) and 1-octadecanethiol (ODT) on ultraflat template-stripped gold (TSG) surfaces was systematically investigated to clarify the assembly behavior, composition, and degree of possible phase segregation in light of atomic force microscopy (AFM) studies of surface nanobubbles on these substrates. The data for SAMs on TSG were compared to those obtained by adsorption on rough evaporated gold, as reported in a previous study. Quartz crystal microbalance and surface plasmon resonance data acquired in situ on TSG indicate that similar to SAM formation on conventional evaporated gold substrates ODT and MHDA form monolayers and bilayers, respectively. The second layer on MHDA, whose formation is attributed to hydrogen bonding, can be easily removed by adequate rinsing with water. The favorable agreement of the grazing incidence reflection Fourier transform infrared (GIR FTIR) spectroscopy and contact angle data analyzed with the Israelachvili-Gee model suggests that the binary SAMs do not segregate laterally. This conclusion is fully validated by high-resolution friction force AFM observations down to a length scale of 8-10 nm, which is much smaller than the typical observed surface nanobubble radii. Finally, correspondingly functionalized TSG substrates are shown to be valuable supports for studying surface nanobubbles by AFM in water and for addressing the relation between surface functionality and nanobubble formation and properties.

Aggregation of trypsin and trypsin inhibitor by Al cation.

PubMed

Chanphai, P; Kreplak, L; Tajmir-Riahi, H A

2017-04-01

Al cation may trigger protein structural changes such as aggregation and fibrillation, causing neurodegenerative diseases. We report the effect of Al cation on the solution structures of trypsin (try) and trypsin inhibitor (tryi), using thermodynamic analysis, UV-Visible, Fourier transform infrared (FTIR) spectroscopic methods and atomic force microscopy (AFM). Thermodynamic parameters showed Al-protein bindings occur via H-bonding and van der Waals contacts for trypsin and trypsin inhibitor. AFM showed that Al cations are able to force trypsin into larger or more robust aggregates than trypsin inhibitor, with trypsin 5±1 SE (n=52) proteins per aggregate and for trypsin inhibitor 8.3±0.7 SE (n=118). Thioflavin T test showed no major protein fibrillation in the presence of Al cation. Al complexation induced more alterations of trypsin inhibitor conformation than trypsin. Copyright © 2017 Elsevier B.V. All rights reserved.

Evidence-Based Nanoscopic and Molecular Framework for Excipient Functionality in Compressed Orally Disintegrating Tablets

PubMed Central

Al-khattawi, Ali; Alyami, Hamad; Townsend, Bill; Ma, Xianghong; Mohammed, Afzal R.

2014-01-01

The work investigates the adhesive/cohesive molecular and physical interactions together with nanoscopic features of commonly used orally disintegrating tablet (ODT) excipients microcrystalline cellulose (MCC) and D-mannitol. This helps to elucidate the underlying physico-chemical and mechanical mechanisms responsible for powder densification and optimum product functionality. Atomic force microscopy (AFM) contact mode analysis was performed to measure nano-adhesion forces and surface energies between excipient-drug particles (6-10 different particles per each pair). Moreover, surface topography images (100 nm2–10 µm2) and roughness data were acquired from AFM tapping mode. AFM data were related to ODT macro/microscopic properties obtained from SEM, FTIR, XRD, thermal analysis using DSC and TGA, disintegration testing, Heckel and tabletability profiles. The study results showed a good association between the adhesive molecular and physical forces of paired particles and the resultant densification mechanisms responsible for mechanical strength of tablets. MCC micro roughness was 3 times that of D-mannitol which explains the high hardness of MCC ODTs due to mechanical interlocking. Hydrogen bonding between MCC particles could not be established from both AFM and FTIR solid state investigation. On the contrary, D-mannitol produced fragile ODTs due to fragmentation of surface crystallites during compression attained from its weak crystal structure. Furthermore, AFM analysis has shown the presence of extensive micro fibril structures inhabiting nano pores which further supports the use of MCC as a disintegrant. Overall, excipients (and model drugs) showed mechanistic behaviour on the nano/micro scale that could be related to the functionality of materials on the macro scale. PMID:25025427

Microstructural Organization of Elastomeric Polyurethanes with Siloxane-Containing Soft Segments

NASA Astrophysics Data System (ADS)

Choi, Taeyi; Weklser, Jadwiga; Padsalgikar, Ajay; Runt, James

2011-03-01

In the present study, we investigate the microstructure of two series of segmented polyurethanes (PUs) containing siloxane-based soft segments and the same hard segments, the latter synthesized from diphenylmethane diisocyanate and butanediol. The first series is synthesized using a hydroxy-terminated polydimethylsiloxane macrodiol and varying hard segment contents. The second series are derived from an oligomeric diol containing both siloxane and aliphatic carbonate species. Hard domain morphologies were characterized using tapping mode atomic force microscopy and quantitative analysis of hard/soft segment demixing was conducted using small-angle X-ray scattering. The phase transitions of all materials were investigated using DSC and dynamic mechanical analysis, and hydrogen bonding by FTIR spectroscopy.

Influence of high energy ion irradiation on fullerene derivative (PCBM) thin films

NASA Astrophysics Data System (ADS)

Sharma, Trupti; Singhal, Rahul; Vishnoi, Ritu; Lakshmi, G. B. V. S.; Biswas, S. K.

2017-04-01

The modifications produced by 55 MeV Si4+ swift heavy ion irradiation on the phenyl C61 butyric acid methyl ester (PCBM) thin films (thickness ∼ 100 nm) has been enlightened. The PCBM thin films were irradiated at 1 × 1010, 1 × 1011 and 1 × 1012 ions/cm2 fluences. After ion irradiation, the decreased optical band gap and FTIR band intensities were observed. The Raman spectroscopy reveals the damage produced by energetic ions. The morphological variation were investigated by atomic force microscopy and contact angle measurements and observed to be influenced by incident ion fluences. After 1011 ions/cm2 fluence, the overlapping of ion tracks starts and produced overlapping effects.

IR and electrochemical synthesis and characterization of thin films of PEDOT grown on platinum single crystal electrodes in [EMMIM]Tf2N ionic liquid.

PubMed

Sandoval, Andrea P; Suárez-Herrera, Marco F; Feliu, Juan M

2015-01-01

Thin films of PEDOT synthesized on platinum single electrodes in contact with the ionic liquid 1-ethyl-2,3-dimethylimidazolium triflimide ([EMMIM]Tf2N) were studied by cyclic voltammetry, chronoamperometry, infrared spectroscopy and atomic force microscopy. It was found that the polymer grows faster on Pt(111) than on Pt(110) or Pt(100) and that the redox reactions associated with the PEDOT p-doping process are much more reversible in [EMMIM]Tf2N than in acetonitrile. Finally, the ion exchange and charge carriers' formation during the p-doping reaction of PEDOT were studied using in situ FTIR spectroscopy.

Atomic force measurements of 16-mercaptohexadecanoic acid and its salt with CH 3, OH, and CONHCH 3 functionalized self-assembled monolayers

NASA Astrophysics Data System (ADS)

Morales-Cruz, Angel L.; Tremont, Rolando; Martínez, Ramón; Romañach, Rodolfo; Cabrera, Carlos R.

2005-03-01

Chemical and mechanical properties of different compounds can be elucidated by measuring fundamental forces such as adhesion, attraction and repulsion, between modified surfaces by means of atomic force microscopy (AFM) in force mode calibration. This work presents a combination of AFM, self-assembled monolayers (SAMs), and crystallization techniques to study the forces of interaction between excipients and active ingredients used in pharmaceutical formulations. SAMs of 16-mercaptohexadecanoate, which represent magnesium stereate, were used to modify the probe tip, whereas CH3-, OH- and CONHCH3-functional SAMs were formed on a gold-coated mica substrate, and used as examples of the surfaces of lactose and theophylline. The crystals of lactose and theophylline were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The modification of gold surfaces with 16-mercaptohexadecanoate, 10-mercapto-1-decanol (OH-functional SAM), 1-decanethiol (CH3-functional) and N-methyl-11-mercaptoundecanamide (CONHCH3-functional SAM) was studied by X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and Fourier transform-infrared spectroscopy (FT-IR) in specular reflectance mode. XPS and AES results of the modified surfaces showed the presence of sulfur binding, and kinetic energies that correspond to the presence of 10-mercapto-1-decanol, 1-decanethiol, N-methyl-11-mercaptoundecanamide and the salt of 16-mercaptohexadecanoic acid. The absorption bands in the IR spectra further confirm the modification of the gold-coated substrates with these compounds. Force versus distance measurements were performed between the modified tip and the modified gold-coated mica substrates. The mean adhesion forces between the COO-Ca2+ functionalized tip and the CH3-, OH-, and CONHCH3-modified substrates were determined to be 4.5, 8.9 and 6.3 nN, respectively. The magnitude of the adhesion force (ion-dipole) interaction between the modified tip and substrate decreases in the following order: COO-Ca2+/OH > COO-Ca2+/CONHCH3 > COO-Ca2+/CH3.

Study on the interaction of triadimenol with calf thymus DNA by multispectroscopic methods and molecular modeling

NASA Astrophysics Data System (ADS)

Zhang, Yepeng; Zhang, Guowen; Fu, Peng; Ma, Yadi; Zhou, Jia

2012-10-01

The binding mechanism of triadimenol (NOL) to calf thymus DNA (ctDNA) in physiological buffer (pH 7.4) was investigated by multispectroscopic methods including UV-vis absorption, fluorescence, circular dichroism (CD), Fourier transform infrared (FT-IR), and nuclear magnetic resonance (1H NMR) spectroscopy, coupled with viscosity measurements and atomic force microscopy (AFM) technique. The results suggested that NOL interacted with ctDNA by intercalation mode. CD and AFM assays showed that NOL can damage the base stacking of ctDNA and result in regional cleavage of the two DNA strands. FT-IR and 1H NMR spectra coupled with molecular docking revealed that a specific binding mainly exists between NOL and G-C base pairs of the ctDNA where two hydrogen bonds form. Moreover, the association constants of NOL with DNA at three different temperatures were determined to be in the 103 L mol-1 range. The calculated thermodynamic parameters suggested that the binding of NOL to ctDNA was driven mainly by hydrogen bond and van der Waals.

Broadband near-field infrared spectromicroscopy using photothermal probes and synchrotron radiation.

PubMed

Donaldson, Paul M; Kelley, Chris S; Frogley, Mark D; Filik, Jacob; Wehbe, Katia; Cinque, Gianfelice

2016-02-08

In this paper, we experimentally demonstrate the use of infrared synchrotron radiation (IR-SR) as a broadband source for photothermal near-field infrared spectroscopy. We assess two methods of signal transduction; cantilever resonant thermal expansion and scanning thermal microscopy. By means of rapid mechanical chopping (50-150 kHz), we modulate the IR-SR at rates matching the contact resonance frequencies of atomic force microscope (AFM) cantilevers, allowing us to record interferograms yielding Fourier transform infrared (FT-IR) photothermal absorption spectra of polystyrene and cyanoacrylate films. Complementary offline measurements using a mechanically chopped CW IR laser confirmed that the resonant thermal expansion IR-SR measurements were below the diffraction limit, with a spatial resolution better than 500 nm achieved at a wavelength of 6 μm, i.e. λ/12 for the samples studied. Despite achieving the highest signal to noise so far for a scanning thermal microscopy measurement under conditions approaching near-field (dictated by thermal diffusion), the IR-SR resonant photothermal expansion FT-IR spectra measured were significantly higher in signal to noise in comparison with the scanning thermal data.

Antimicrobial activity of biopolymeric thin films containing flavonoid natural compounds and silver nanoparticles fabricated by MAPLE: A comparative study

NASA Astrophysics Data System (ADS)

Cristescu, R.; Visan, A.; Socol, G.; Surdu, A. V.; Oprea, A. E.; Grumezescu, A. M.; Chifiriuc, M. C.; Boehm, R. D.; Yamaleyeva, D.; Taylor, M.; Narayan, R. J.; Chrisey, D. B.

2016-06-01

The purpose of this study was to investigate the interactions between microorganisms, including the planktonic and adherent organisms, and biopolymer (polyvinylpyrrolidone), flavonoid (quercetin dihydrate and resveratrol)-biopolymer, and silver nanoparticles-biopolymer composite thin films that were deposited using matrix assisted pulsed laser evaporation (MAPLE). A pulsed KrF* excimer laser source was used to deposit the aforementioned composite thin films, which were characterized using Fourier transform infrared spectroscopy (FT-IR), infrared microscopy (IRM), scanning electron microscopy (SEM), Grazing incidence X-ray diffraction (GIXRD) and atomic force microscopy (AFM). The antimicrobial activity of thin films was quantified using an adapted disk diffusion assay against Gram-positive and Gram-negative bacteria strains. FT-IR, AFM and SEM studies confirmed that MAPLE may be used to fabricate thin films with chemical properties corresponding to the input materials as well as surface properties that are appropriate for medical use. The silver nanoparticles and flavonoid-containing films exhibited an antimicrobial activity both against Gram-positive and Gram-negative bacterial strains demonstrating the potential use of these hybrid systems for the development of novel antimicrobial strategies.

Synthesis, structural characterisation and antibacterial activity of Ag+-doped fluorapatite nanomaterials prepared by neutralization method

NASA Astrophysics Data System (ADS)

Stanić, Vojislav; Radosavljević-Mihajlović, Ana S.; Živković-Radovanović, Vukosava; Nastasijević, Branislav; Marinović-Cincović, Milena; Marković, Jelena P.; Budimir, Milica D.

2015-05-01

Silver doped fluorapatite nanopowders were synthesised by neutralization method, which consists of dissolving Ag2O in solution of HF and H3PO4 and addition to suspension of Ca(OH)2. The powder XRD, SEM and FTIR studies indicated the formation of a fluorapatite nanomaterials with average length of the particles is about 80 nm and a width of about 15 nm. The FTIR studies show that carbonate content in samples is very small and carbonte ions substitute both phosphate and hydroxyl groups in the crystal structure of samples, forming AB-type fluorapatite. Antibacterial studies have demonstrated that all Ag+-doped fluorapatite samples exhibit bactericidal effect against pathogens: Staphylococcus aureus, Micrococcus luteus and Kllebsiela pneumoniae. Antibacterial activity increased with the increase of Ag+ in the samples. The atomic force microscopy studies revealed extensive damage to the bacterial cell envelops in the presence of Ag+-doped fluorapatite particles which may lead to their death. The synthesized Ag+-doped fluorapatite nanomaterials are promising as antibacterial biomaterials in orthopedics and dentistry.

Functionalization of Carbon Nanotubes using Atomic Hydrogen

NASA Technical Reports Server (NTRS)

Khare, Bishun N.; Cassell, Alan M.; Nguyen, Cattien V.; Meyyappan, M.; Han, Jie; Arnold, Jim (Technical Monitor)

2001-01-01

We have investigated the irradiation of multi walled and single walled carbon nanotubes (SWNTs) with atomic hydrogen. After irradiating the SWNT sample, a band at 2940/cm (3.4 microns) that is characteristic of the C-H stretching mode is observed using Fourier transform infrared (FTIR) spectroscopy. Additional confirmation of SWNT functionalization is tested by irradiating with atomic deuterium. A weak band in the region 1940/cm (5.2 micron) to 2450/cm (4.1 micron) corresponding to C-D stretching mode is also observed in the FTIR spectrum. This technique provides a clean gas phase process for the functionalization of SWNTs, which could lead to further chemical manipulation and/or the tuning of the electronic properties of SWNTs for nanodevice applications.

In Situ Infrared Spectroscopic Studies of Molecular Layer Deposition and Atomic Layer Etching Processes

NASA Astrophysics Data System (ADS)

DuMont, Jaime Willadean

In this thesis, in situ Fourier transform infrared (FTIR) spectroscopy was used to study: i) the growth and pyrolysis of molecular layer deposition (MLD) films. ii) the surface chemistry of atomic layer etching (ALE) processes. Atomic layer processes such as molecular layer deposition (MLD) and atomic layer etching (ALE) are techniques that can add or remove material with atomic level precision using sequential, self-limiting surface reactions. Deposition and removal processes at the atomic scale are powerful tools for many industrial and research applications such as energy storage and semiconductor nanofabrication. The first section of this thesis describes the chemistry of reactions leading to the MLD of aluminum and tin alkoxide polymer films known as "alucone" and "tincone", respectively. The subsequent pyrolysis of these films to produce metal oxide/carbon composites was also investigated. In situ FTIR spectroscopy was conducted to monitor surface species during MLD film growth and to monitor the films background infrared absorbance versus pyrolysis temperature. Ex situ techniques such as transmission electron microscopy (TEM), four-point probe and X-ray diffraction (XRD) were utilized to study the properties of the films post-pyrolysis. TEM confirmed that the pyrolyzed films maintained conformality during post-processing. Four-point probe monitored film resistivity versus pyrolysis temperature and XRD determined the film crystallinity. The second section of this thesis focuses on the surface chemistry of Al2O3 and SiO2 ALE processes, respectively. Thermal ALE processes have been recently developed which utilize sequential fluorination and ligand exchange reactions. An intimate knowledge of the surface chemistry is important in understanding the ALE process. In this section, the competition between the Al2O3 etching and AlF 3 growth that occur during sequential HF (fluorinating agent) and TMA (ligand exchange) exposures is investigated using in situ FTIR spectroscopy. Also included in this section is the first demonstration of thermal ALE for SiO2. In situ FTIR spectroscopy was conducted to monitor the loss of bulk Si-O vibrational modes corresponding to the removal of SiO2. FTIR was also used to monitor surface species during each ALE half cycle and to verify self-limiting behavior. X-ray reflectivity experiments were conducted to establish etch rates on thermal oxide silicon wafers.

AFM combined to ATR-FTIR reveals Candida cell wall changes under caspofungin treatment.

PubMed

Quilès, Fabienne; Accoceberry, Isabelle; Couzigou, Célia; Francius, Grégory; Noël, Thierry; El-Kirat-Chatel, Sofiane

2017-09-21

Fungal pathogens from Candida genus are responsible for severe life-threatening infections and the antifungal arsenal is still limited. Caspofungin, an antifungal drug used for human therapy, acts as a blocking agent of the cell wall synthesis by inhibiting the β-1,3-glucan-synthase encoded by FKS genes. Despite its efficiency, the number of genetic mutants that are resistant to caspofungin is increasing. An important challenge to improve antifungal therapy is to understand cellular phenomenon that are associated with drug resistance. Here we used atomic force microscopy (AFM) combined to Fourier transform infrared spectroscopy in attenuated total reflection mode (ATR-FTIR) to decipher the effect of low and high drug concentration on the morphology, mechanics and cell wall composition of two Candida strains, one susceptible and one resistant to caspofungin. Our results confirm that caspofungin induces a dramatic cell wall remodelling via activation of stress responses, even at high drug concentration. Additionally, we highlighted unexpected changes related to drug resistance, suggesting that caspofungin resistance associated with FKS gene mutations comes from a combination of effects: (i) an overall remodelling of yeast cell wall composition; and (ii) cell wall stiffening through chitin synthesis. This work demonstrates that AFM combined to ATR-FTIR is a valuable approach to understand at the molecular scale the biological mechanisms associated with drug resistance.

One-Step Electrochemical Preparation of Multilayer Graphene Functionalized with Nitrogen

NASA Astrophysics Data System (ADS)

Ustavytska, Olena; Kurys, Yaroslav; Koshechko, Vyacheslav; Pokhodenko, Vitaly

2017-03-01

A new environmentally friendly one-step method for producing multilayer (preferably 7-9 layers) nitrogen-doped graphene (N-MLG) with a slight amount of oxygen-containing defects was developed. The approach is based on the electrochemical exfoliation of graphite electrode in the presence of azide ions under the conditions of electrolysis with pulse changing of the electrode polarization potential. It was found that usage of azide anions lead not only to the exfoliation of graphite but also to the simultaneous functionalization of graphene sheets by nitrogen atoms (as a result of electrochemical decomposition of azide anions with ammonia evolution). Composition, morphology, structure, and electrochemical properties of N-MLG were characterized by C,H,N analysis, transmission electron microscopy, atomic force microscopy, FTIR, UV-Vis, and Raman spectroscopy, as well as cyclic voltammetry. The perspective of using N-MLG as oxygen reduction reaction electrocatalyst and for the electrochemical analysis of biomarkers (dopamine, ascorbic acid, and uric acid) in their mixtures was shown.

A simple structural hydrazide-based gelator as a fluoride ion colorimetric sensor.

PubMed

Bai, Binglian; Ma, Jie; Wei, Jue; Song, Jianxi; Wang, Haitao; Li, Min

2014-06-07

A 4-nitrobenzohydrazide derivative, N-(3,4,5-octyloxybenzoyl)-N'-(4'-nitrobenzoyl)hydrazine (C8), was synthesized. It could form stable gels in some of the tested organic solvents. The wide-angle X-ray diffraction analysis showed that the xerogels exhibited a layered structure. SEM images revealed that the molecules self-assembled into fibrous aggregates in the xerogels. FT-IR studies confirmed that the intermolecular hydrogen bonding between C=O and N-H groups was the major driving force for the formation of self-assembling gel processes. The gel is utilized for a 'naked eye' detection of fluoride ions, through a reversible gel-sol transition, which is associated with a color change from colorless to red. An extended conjugated system formed through the phenyl group and a five-membered ring based on intramolecular hydrogen bonding between the oxygen atom near the deprotonation nitrogen atom and the other NH, which is responsible for the dramatic color change upon addition of fluoride ions.

Synthesis, crystal growth, characterization and theoretical studies of 4-aminobenzophenonium picrate

NASA Astrophysics Data System (ADS)

Aditya Prasad, A.; Muthu, K.; Rajasekar, M.; Meenatchi, V.; Meenakshisundaram, S. P.

2015-01-01

Single crystals of 4-aminobenzophenonium picrate (4ABPP) were grown by slow evaporation of a mixed solvent system methanol-acetone (1:1,v/v) containing equimolar quantities of picric acid and 4-aminobenzophenone. The proton and carbon signals are confirmed by nuclear magnetic resonance spectroscopy. The various functional groups present in the molecule are identified by FT-IR analysis. Optimized geometry, first-order molecular hyperpolarizability (β), polarizability (α), bond length, bond angles and excited state energy from theoretical UV were derived by Hartree-Fock calculations. The complete assignment of the vibrational modes for 4-aminobenzophenonium picrate was performed by the scaled quantum mechanics force field (SQMFF) methodology using potential energy distribution. Natural bond orbital (NBO) calculations were employed to study the stabilities arising from charge delocalization and intermolecular interactions of 4ABPP. The atomic charge distributions of the various atoms present in 4ABPP are obtained by Mulliken charge population analysis. The as-grown crystal is further characterized by thermal and optical absorbance studies.

Inhibitory effect of phloretin on α-glucosidase: Kinetics, interaction mechanism and molecular docking.

PubMed

Han, Lin; Fang, Chun; Zhu, Ruixue; Peng, Qiang; Li, Ding; Wang, Min

2017-02-01

As the aglycone of phloridzin, phloretin belongs to dihydrochalcone with antioxidant, anti-inflammatory and antimicrobial activities. In this study, multispectroscopic techniques and molecular docking analysis were used to investigate the inhibitory activity and mechanisms of phloretin on α-glucosidase. The results showed that phloretin reversibly inhibited α-glucosidase in a mixed-type manner and the value of IC 50 was 31.26μgL -1 . The intrinsic fluorescence of α-glucosidase was quenched by the interactions with phloretin through a static quenching mechanism and spontaneously formed phloretin-α-glucosidase complex by the driving forces of van der Waals force and hydrogen bond. Atomic force microscope (AFM) studies and FT-IR measurements suggested that the interactions could change the micro-environments and conformation of the enzymes and the molecular docking analysis displayed the exact binding site of phloretin on α-glucosidase. These results indicated that phloretin is a strong α-glucosidase inhibitor, thus could be contribute to the improvement of diabetes mellitus. Copyright © 2016 Elsevier B.V. All rights reserved.

Binding affinity and adhesion force of organophosphate hydrolase enzyme with soil particles related to the isoelectric point of the enzyme.

PubMed

Islam, Shah Md Asraful; Yeasmin, Shabina; Islam, Md Saiful; Islam, Md Shariful

2017-07-01

The binding affinity of organophosphate hydrolase enzyme (OphB) with soil particles in relation to the isoelectric point (pI) was studied. Immobilization of OphB with soil particles was observed by confocal microscopy, Fourier transform infrared spectroscopy (FT-IR), and Atomic force microscopy (AFM). The calculated pI of OphB enzyme was increased from 8.69 to 8.89, 9.04 and 9.16 by the single, double and triple mutant of OphB enzyme, respectively through the replacement of negatively charged aspartate with positively charged histidine. Practically, the binding affinity was increased to 5.30%, 11.50%, and 16.80% for single, double and triple mutants, respectively. In contrast, enzyme activity of OphB did not change by the mutation of the enzyme. On the other hand, adhesion forces were gradually increased for wild type OphB enzyme (90 pN) to 96, 100 and 104 pN for single, double and triple mutants of OphB enzyme, respectively. There was an increasing trend of binding affinity and adhesion force by the increase of isoelectric point (pI) of OphB enzyme. Copyright © 2017 Elsevier Inc. All rights reserved.

FTIR, FT-RAMAN, NMR, spectra, normal co-ordinate analysis, NBO, NLO and DFT calculation of N,N-diethyl-4-methylpiperazine-1-carboxamide molecule

NASA Astrophysics Data System (ADS)

Muthu, S.; Elamurugu Porchelvi, E.

2013-11-01

The Fourier Transform Infrared (FT-IR) and FT-Raman of N,N-diethyl-4-methylpiperazine-1-carboxamide (NND4MC) have been recorded and analyzed. The structure of the compound was optimized and the structural characteristics were determined by density functional theory (DFT) using B3LYP method with 6-31G(d,p) and 6-311G(d,p) basis sets. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. The theoretically predicted FT-IR and FT-Raman spectra of the title molecule have been constructed. The detailed interpretation of the vibrational spectra has been carried out with aid of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The results show that electron density (ED) in the σ* and π* antibonding orbitals and second order delocalization energies (E2) confirm the occurrence of intramolecular charge transfer (ICT) within the molecule. The electronic dipole moment (μD) and the first hyperpolarizability (βtot) values of the investigated molecule were computed using Density Functional Theory (DFT/B3LYP) with 6-31G(d,p) and 6-311G(d,p) basis sets. The calculated results also show that the NND4MC molecule may have microscopy nonlinear optical (NLO) behavior with non zero values. Mulliken atomic charges of NND4MC were calculated. The 13C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by the gauge independent atomic orbital (GIAO) method and compared with experimental results. The UV-Vis spectrum of the compound was recorded. The theoretical electronic absorption spectra have been calculated by using CIS, TD-DFT methods. A study on the electronic properties, such as HOMO and LUMO energies, molecular electrostatic potential (MEP) were also performed.

Mirrorlike pulsed laser deposited tungsten thin film.

PubMed

Mostako, A T T; Rao, C V S; Khare, Alika

2011-01-01

Mirrorlike tungsten thin films on stainless steel substrate deposited via pulsed laser deposition technique in vacuum (10(-5) Torr) is reported, which may find direct application as first mirror in fusion devices. The crystal structure of tungsten film is analyzed using x-ray diffraction pattern, surface morphology of the tungsten films is studied with scanning electron microscope and atomic force microscope. The film composition is identified using energy dispersive x-ray. The specular and diffuse reflectivities with respect to stainless steel substrate of the tungsten films are recorded with FTIR spectra. The thickness and the optical quality of pulsed laser deposition deposited films are tested via interferometric technique. The reflectivity is approaching about that of the bulk for the tungsten film of thickness ∼782 nm.

Tribology study of reduced graphene oxide sheets on silicon substrate synthesized via covalent assembly.

PubMed

Ou, Junfei; Wang, Jinqing; Liu, Sheng; Mu, Bo; Ren, Junfang; Wang, Honggang; Yang, Shengrong

2010-10-19

Reduced graphene oxide (RGO) sheets were covalently assembled onto silicon wafers via a multistep route based on the chemical adsorption and thermal reduction of graphene oxide (GO). The formation and microstructure of RGO were analyzed by X-ray photoelectron spectroscopy (XPS), attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, Raman spectroscopy, and water contact angle (WCA) measurements. Characterization by atomic force microscopy (AFM) was performed to evaluate the morphology and microtribological behaviors of the samples. Macrotribological performance was tested on a ball-on-plate tribometer. Results show that the assembled RGO possesses good friction reduction and antiwear ability, properties ascribed to its intrinsic structure, that is, the covalent bonding to the substrate and self-lubricating property of RGO.

IR and electrochemical synthesis and characterization of thin films of PEDOT grown on platinum single crystal electrodes in [EMMIM]Tf2N ionic liquid

PubMed Central

Sandoval, Andrea P; Suárez-Herrera, Marco F

2015-01-01

Summary Thin films of PEDOT synthesized on platinum single electrodes in contact with the ionic liquid 1-ethyl-2,3-dimethylimidazolium triflimide ([EMMIM]Tf2N) were studied by cyclic voltammetry, chronoamperometry, infrared spectroscopy and atomic force microscopy. It was found that the polymer grows faster on Pt(111) than on Pt(110) or Pt(100) and that the redox reactions associated with the PEDOT p-doping process are much more reversible in [EMMIM]Tf2N than in acetonitrile. Finally, the ion exchange and charge carriers’ formation during the p-doping reaction of PEDOT were studied using in situ FTIR spectroscopy. PMID:25815089

Morphological and spectroscopic analysis of cellulose nanocrystals extracted from oil palm empty fruit bunch fiber

NASA Astrophysics Data System (ADS)

Dasan, Y. K.; Bhat, A. H.; Faiz, A.

2015-07-01

This work evaluates the use of oil palm empty fruit bunch (OPEFB) fiber as a source of cellulose to obtain nanocrystalline cellulose (CNC) by acid hydrolysis reaction. The raw OPEFB fibers were pretreated with aqueous Sodium hydroxide at 80°C followed by bleaching treatment and further hydrolyzed with Sulphuric acid at 45°C with limited range of hydrolysis time and acid concentration. The resulting CNC's were characterized for spectroscopic, crystallographic and morphological properties using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffractometer (XRD), Transmission Electron Microscope (TEM) and Atomic Force Microscopy (AFM). Finding of this study shows that the properties of CNC's are strongly dependent on the hydrolysis time and acid concentration.

The Addition of Graphene to Polymer Coatings for Improved Weathering

DOE PAGES

Nuraje, Nurxat; Khan, Shifath I.; Misak, Heath; ...

2013-01-01

Graphene nanoflakes in different weight percentages were added to polyurethane top coatings, and the coatings were evaluated relative to exposure to two different experimental conditions: one a QUV accelerated weathering cabinet, while the other a corrosion test carried out in a salt spray chamber. After the exposure tests, the surface morphology and chemical structure of the coatings were investigated via atomic force microscopy (AFM) and Fourier transform infrared (FTIR) imaging. Our results show that the addition of graphene does in fact improve the resistance of the coatings against ultraviolet (UV) degradation and corrosion. It is believed that this process willmore » improve the properties of the polyurethane top coating used in many industries against environmental factors.« less

Characterization of the modified nickel-zinc ferrite nanoparticles coated with APTES by salinization reaction

NASA Astrophysics Data System (ADS)

Zainal, Israa G.; Al-Shammari, Ahmed Majeed; Kachi, Wjeah

2018-05-01

Surface functionalization of magnetic iron oxide nanoparticles (NPs) is a kind of functional materials, which have been widely used in the biotechnology and catalysis. In this study, Nickel-Zinc ferrite nanoparticles was functionalized with amino propyl triethoxy silane (APTES) by silanization reaction and both non coated and organosilane-coated magnetite characterized by energy-dispersive X-ray spectroscopy (EDX), X-ray diffractometry, Fourier transformed infrared spectroscopy (FTIR) and atomic force microscopy. Basic groups of amino anchored on the external surface of the coated magnetite were observed. Our study procedure nanoparticles which have surface with free - NH2 groups which can carry out ionic interaction with carboxylic groups and act as a carrier of biological molecules, drugs and metals.

Fourier transform infrared spectroscopic study of intact cells of the nitrogen-fixing bacterium Azospirillum brasilense

NASA Astrophysics Data System (ADS)

Kamnev, A. A.; Ristić, M.; Antonyuk, L. P.; Chernyshev, A. V.; Ignatov, V. V.

1997-06-01

The data of Fourier transform infrared (FTIR) spectroscopic measurements performed on intact cells of the soil nitrogen-fixing bacterium Azospirillum brasilense grown in a standard medium and under the conditions of an increased metal uptake are compared and discussed. The structural FTIR information obtained is considered together with atomic absorption spectrometry (AAS) data on the content of metal cations in the bacterial cells. Some methodological aspects concerning preparation of bacterial cell samples for FTIR measurements are also discussed.

Komagataeibacter rhaeticus as an alternative bacteria for cellulose production.

PubMed

Machado, Rachel T A; Gutierrez, Junkal; Tercjak, Agnieszka; Trovatti, Eliane; Uahib, Fernanda G M; Moreno, Gabriela de Padua; Nascimento, Andresa P; Berreta, Andresa A; Ribeiro, Sidney J L; Barud, Hernane S

2016-11-05

A strain isolated from Kombucha tea was isolated and used as an alternative bacterium for the biosynthesis of bacterial cellulose (BC). In this study, BC generated by this novel bacterium was compared to Gluconacetobacter xylinus biosynthesized BC. Kinetic studies reveal that Komagataeibacter rhaeticus was a viable bacterium to produce BC according to yield, thickness and water holding capacity data. Physicochemical properties of BC membranes were investigated by UV-vis and Fourier transform infrared spectroscopies (FTIR), thermogravimetrical analysis (TGA) and X-ray diffraction (XRD). Additionally, scanning electron microscopy (SEM) and atomic force microscopy (AFM) were also used for morphological characterization. Mechanical properties at nano and macroscale were studied employing PeakForce quantitative nanomechanical property mapping (QNM) and dynamic mechanical analyzer (DMA), respectively. Results confirmed that BC membrane biosynthesized by Komagataeibacter rhaeticus had similar physicochemical, morphological and mechanical properties than BC membrane produced by Gluconacetobacter xylinus and can be widely used for the same applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

Molecular structure, spectroscopic (FTIR, FT-Raman, 13C and 1H NMR, UV), polarizability and first-order hyperpolarizability, HOMO-LUMO analysis of 2,4-difluoroacetophenone

NASA Astrophysics Data System (ADS)

Jeyavijayan, S.

2015-02-01

The FTIR and FT-Raman spectra of 2,4-difluoroacetophenone (DFAP) have been recorded in the regions 4000-400 cm-1 and 3500-50 cm-1, respectively. Utilizing the observed FTIR and FT-Raman data, a complete vibrational assignment and analysis of the fundamental modes of the compound were carried out. The optimum molecular geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities, were calculated by density functional theory (DFT/B3LYP) method with 6-31+G(d,p) and 6-311++G(d,p) basis sets. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. A detailed interpretation of the infrared and Raman spectra of DFAP is also reported based on total energy distribution (TED). Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital (NBO) analysis. The MEP map shows the negative potential sites are on oxygen atom as well as the positive potential sites are around the hydrogen atoms. The UV-Vis spectral analysis of DFAP has also been done which confirms the charge transfer of DFAP. The chemical shifts of H atoms and C atoms were calculated using NMR analysis. Furthermore, the polarizability, the first hyperpolarizability and total dipole moment of the molecule have been calculated.

FTIR cryospectroscopic and ab initio studies of desflurane-dimethyl ether H-bonded complexes.

PubMed

Melikova, S M; Rutkowski, K S; Rospenk, M

2017-09-05

The IR spectra of mixtures of desflurane and dimethyl ether are studied with the help of FTIR cryospectroscopy in liquefied Kr at T~118-158K. Comparative analysis of the experimental data and results of ab initio calculations show that either of the two C-H groups of desflurane is involved in heterodimer formation of comparable strengths. The blue frequency shift is found for stretching vibrations of those C-H donors which directly participate in H-bond formation. Additionally the complexes are stabilized by weaker contacts between hydrogen atoms of dimethyl ether and fluorine atoms of desflurane. Copyright © 2017 Elsevier B.V. All rights reserved.

Soft X-Ray Microscopy Radiation Damage On Fixed Cells Investigated With Synchrotron Radiation FTIR Microscopy.

PubMed

Gianoncelli, A; Vaccari, L; Kourousias, G; Cassese, D; Bedolla, D E; Kenig, S; Storici, P; Lazzarino, M; Kiskinova, M

2015-05-14

Radiation damage of biological samples remains a limiting factor in high resolution X-ray microscopy (XRM). Several studies have attempted to evaluate the extent and the effects of radiation damage, proposing strategies to minimise or prevent it. The present work aims to assess the impact of soft X-rays on formalin fixed cells on a systematic manner. The novelty of this approach resides on investigating the radiation damage not only with XRM, as often reported in relevant literature on the topic, but by coupling it with two additional independent non-destructive microscopy methods: Atomic Force Microscopy (AFM) and FTIR Microscopy (FTIRM). Human Embryonic Kidney 293 cells were exposed to different radiation doses at 1 keV. In order to reveal possible morphological and biochemical changes, the irradiated cells were systematically analysed with AFM and FTIRM before and after. Results reveal that while cell morphology is not substantially affected, cellular biochemical profile changes significantly and progressively when increasing dose, resulting in a severe breakdown of the covalent bonding network. This information impacts most soft XRM studies on fixed cells and adds an in-depth understanding of the radiation damage for developing better prevention strategies.

Soft X-Ray Microscopy Radiation Damage On Fixed Cells Investigated With Synchrotron Radiation FTIR Microscopy

PubMed Central

Gianoncelli, A.; Vaccari, L.; Kourousias, G.; Cassese, D.; Bedolla, D. E.; Kenig, S.; Storici, P.; Lazzarino, M.; Kiskinova, M.

2015-01-01

Radiation damage of biological samples remains a limiting factor in high resolution X-ray microscopy (XRM). Several studies have attempted to evaluate the extent and the effects of radiation damage, proposing strategies to minimise or prevent it. The present work aims to assess the impact of soft X-rays on formalin fixed cells on a systematic manner. The novelty of this approach resides on investigating the radiation damage not only with XRM, as often reported in relevant literature on the topic, but by coupling it with two additional independent non-destructive microscopy methods: Atomic Force Microscopy (AFM) and FTIR Microscopy (FTIRM). Human Embryonic Kidney 293 cells were exposed to different radiation doses at 1 keV. In order to reveal possible morphological and biochemical changes, the irradiated cells were systematically analysed with AFM and FTIRM before and after. Results reveal that while cell morphology is not substantially affected, cellular biochemical profile changes significantly and progressively when increasing dose, resulting in a severe breakdown of the covalent bonding network. This information impacts most soft XRM studies on fixed cells and adds an in-depth understanding of the radiation damage for developing better prevention strategies. PMID:25974639

Green synthesis and characterization of graphene nanosheets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tavakoli, Farnosh; Salavati-Niasari, Masoud, E-mail: salavati@kashanu.ac.ir; Department of Inorganic Chemistry, Faculty of Chemistry, University of Kashan, Kashan, P. O. Box. 87317-51167, Islamic Republic of Iran

Highlights: • For the first time, we have synthesized graphene nanosheets in the presence of pomegranate juice. • Here pomegranate juice was used not only as reductant but also as capping agent. • FT-IR, XRD, SEM, EDS and TEM were used to characterize the samples. • According to TEM image, graphene nanosheet is individually exfoliated after stirring for 24 h. • As shown in the TEM image, graphene monolayer is obtained. - Abstract: For the first time, we have successfully synthesized graphene nanosheets in the presence of pomegranate juice. In this approach, pomegranate juice was used not only as reductantmore » but also as capping agent to form graphene nanosheets. At first, the improved Hummer method to oxidize graphite for the synthesis of graphene oxide (GO) was applied, and then the as-produced graphene oxide was reduced by pomegranate juice to form graphene nanosheets. Fourier transformed infrared (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), high resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM) and raman were used to characterize the samples. The results obtained from the characterization techniques proved high purity of the final products.« less

Structural, electronic, topological and vibrational properties of a series of N-benzylamides derived from Maca (Lepidium meyenii) combining spectroscopic studies with ONION calculations

NASA Astrophysics Data System (ADS)

Chain, Fernando E.; Ladetto, María Florencia; Grau, Alfredo; Catalán, César A. N.; Brandán, Silvia Antonia

2016-02-01

In the present work, the structural, topological and vibrational properties of four members of the N-benzylamides series derived from Maca (Lepidium meyenii) whose names are, N-benzylpentadecanamide, N-benzylhexadecanamide, N-benzylheptadecanamide and N-benzyloctadecanamide, were studied combining the FTIR, FT-Raman and 1H and 13C-NMR spectroscopies with density functional theory (DFT) and ONION calculations. Furthermore, the N-benzylacetamide, N-benzylpropilamide and N-benzyl hexanamide derivatives were also studied in order to compare their properties with those computed for the four macamides. These seven N-benzylamides series have a common structure, C8H8NO-R, being R the side chain [-(CH2)n-CH3] with a variable n number of CH2 groups. Here, the atomic charges, molecular electrostatic potentials, stabilization energies, topological properties of those macamides were analyzed as a function of the number of C atoms of the side chain while the frontier orbitals were used to compute the gap energies and some descriptors in order to predict their reactivities and behaviors in function of the longitude of the side chain. Here, the force fields, the complete vibrational assignments and the corresponding force constants were only reported for N-benzylacetamide, N-benzyl hexanamide and N-benzylpentadecanamide due to the high number of vibration normal modes that present the remains macamides.

Revelation of susceptibility differences due to Hg(II) accumulation in Streptococcus pyogenes against CX-AgNPs and Cefixime by atomic force microscopy.

PubMed

Rasheed, Wasia; Shah, Muhammad Raza; Perveen, Samina; Ahmed, Shakil; Uzzaman, Sami

2018-01-01

Solution based method for the formation of chemically modified silver nanoparticles (CX-AgNPs) using Cefixime as stabilizing and reducing agent was developed. The CX-AgNPs were characterized by AFM, UV-visible, FT-IR and MALDI-TOF MS. Bactericidal efficiency of CX-AgNPs and Cefixime against Streptococcus pyogenes was evaluated. Afterwards, susceptibility differences of Streptococcus pyogenes due to accumulation of Hg(II) against CX-AgNPs and Cefixime were estimated and validated through Atomic force microscopy. Selectivity and sensitivity of CX-AgNPs against Hg(II) was evaluated in a systematic manner. The CX-AgNPs was titrated against optically silent Hg(II) which induced enhancement in the SPR band of CX-AgNPs. The increase in intensity of SPR band of CX-AgNPs was determined to be proportionate to the concentration of Hg(II) in the range of 33.3-700µM obeying linear regression equation of y = 0.125x + 8.962 with the detection limit of 0.10µM and the coefficient of determination equals to 0.985 (n = 3). The association constant Ka of CX-AgNPs-Hg(II) was found to be 386.0095mol -1 dm 3 by using the Benesi Hildebrand plot. Copyright © 2017 Elsevier Inc. All rights reserved.

Failure Mechanisms of the Coating/Metal Interface in Waterborne Coatings: The Effect of Bonding

PubMed Central

Wan, Hongxia; Song, Dongdong; Li, Xiaogang; Zhang, Dawei; Gao, Jin; Du, Cuiwei

2017-01-01

Waterborne coating is the most popular type of coating, and improving its performance is a key point of research. Cathodic delamination is one of the major modes of failure for organic coatings. It refers to the weakening or loss of adhesion between the coating and substrate. Physical and chemical characteristics of coatings have been studied via scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle measurements, Fourier transform infrared spectroscopy (FTIR), and secondary ion mass spectrometry (SIMS). Early heterogeneous swelling at the metal-coating interface in non-defective coated metals was elucidated using frequency-dependent alternating-current scanning electrochemical microscopy. Two types of coatings (styrene-acrylic coating and terpolymer coating) were compared. The effects of thickness, surface roughness, and chemical bonding on cathodic delamination were investigated. PMID:28772757

Chitin-natural clay nanotubes hybrid hydrogel.

PubMed

Liu, Mingxian; Zhang, Yun; Li, Jingjing; Zhou, Changren

2013-07-01

Novel hybrid hydrogel was synthesized from chitin NaOH/urea aqueous solution in presence of halloysite nanotubes (HNTs) via crosslinking with epichlorohydrin. Fourier transform infrared (FT-IR) spectra and atomic force microscopy (AFM) results confirmed the interfacial interactions in the chitin-HNTs hybrid hydrogel. The compressive strength and shear modulus of chitin hydrogel were significantly increased by HNTs as shown in the static compressive experiment and rheology measurement. The hybrid hydrogels showed highly porous microstructures by scanning electron microscopy (SEM). The swelling ratio of chitin hydrogel decreased because of the addition of HNTs. The malachite green's absorption experiment result showed that the hybrid hydrogel exhibited much higher absorption rate than the pure chitin hydrogel. The prepared hybrid hydrogel had potential applications in waste treatment and biomedical areas. Copyright © 2013 Elsevier B.V. All rights reserved.

Morphological and spectroscopic analysis of cellulose nanocrystals extracted from oil palm empty fruit bunch fiber

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dasan, Y. K., E-mail: aamir.bhat@petronas.com.my; Bhat, A. H., E-mail: aamir.bhat@petronas.com.my; Faiz, A., E-mail: faizahmad@petronas.com.my

2015-07-22

This work evaluates the use of oil palm empty fruit bunch (OPEFB) fiber as a source of cellulose to obtain nanocrystalline cellulose (CNC) by acid hydrolysis reaction. The raw OPEFB fibers were pretreated with aqueous Sodium hydroxide at 80°C followed by bleaching treatment and further hydrolyzed with Sulphuric acid at 45°C with limited range of hydrolysis time and acid concentration. The resulting CNC’s were characterized for spectroscopic, crystallographic and morphological properties using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffractometer (XRD), Transmission Electron Microscope (TEM) and Atomic Force Microscopy (AFM). Finding of this study shows that the properties of CNC’s aremore » strongly dependent on the hydrolysis time and acid concentration.« less

A molecular imprinted SPR biosensor for sensitive determination of citrinin in red yeast rice.

PubMed

Atar, Necip; Eren, Tanju; Yola, Mehmet Lütfi

2015-10-01

A novel and sensitive molecular imprinted surface plasmon resonance (SPR) biosensor was developed for selective determination of citrinin (CIT) in red yeast rice. Firstly, the gold surface of SPR chip was modified with allyl mercaptane. Then, CIT-imprinted poly(2-hydroxyethyl methacrylate-methacryloylamidoglutamic acid) (p(HEMA-MAGA)) film was generated on the gold surface modified with allyl mercaptane. The unmodified and imprinted surfaces were characterized by Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM) and contact angle measurements. The linearity range and the detection limit were obtained as 0.005-1.0 ng/mL and 0.0017 ng/mL, respectively. The SPR biosensor was applied to determination of CIT in red yeast rice sample. Copyright © 2015 Elsevier Ltd. All rights reserved.

AFM study of the morphologic change of HDPE surface photografted with glycidyl methacrylate.

PubMed

Wang, Huiliang; Han, Jianmei

2009-05-01

The UV-induced grafting of glycidyl methacrylate (GMA) onto high-density polyethylene (HDPE) and the atomic force microscopy (AFM) study of the morphologic change of the grafted surface are reported. The grafting was carried out in GMA acetone solutions with different monomer concentrations. Grafting was much faster in a solution with a higher monomer concentration. FTIR analyses proved that GMA had been successfully grafted onto HDPE. The morphologies of grafted HDPE surfaces changed with UV irradiation time. The monomer concentration had a significant effect on the morphologies of the grafted HDPE surfaces. The HDPE surface grafted in a solution with a higher monomer concentration was much rougher than that grafted in a solution with a lower monomer concentration. The growth models of the grafted granules or clusters are also proposed.

Host-guest inclusion system of ferulic acid with p-Sulfonatocalix[n]arenes: Preparation, characterization and antioxidant activity

NASA Astrophysics Data System (ADS)

Chao, Jianbin; Wang, Huijuan; Song, Kailun; Wang, Yongzhao; Zuo, Ying; Zhang, Liwei; Zhang, Bingtai

2017-02-01

The inclusion complexes of ferulic acid (FA) with p-Sulfonatocalix[n]arenes (SCXn, n = 4, 6, 8) were prepared and characterized both in the solid state and in solution using fluorescence spectroscopy, 1H nuclear magnetic resonance (1H NMR), attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR), atomic force microscopy (AFM) and differential scanning calorimetry (DSC). The results show that FA is able to form inclusion complexes with SCXn in a molar ratio of 1:1, causing a significant decrease in the fluorescence intensity of FA. The association constant of the inclusion complexes was calculated from the fluorescence titration data. 1H NMR spectroscopy analysis demonstrates that the aromatic ring and methoxy group of FA are partially covered by SCXn.

Adsorption and inhibitive properties of sildenafil (Viagra) for zinc in hydrochloric acid solution

NASA Astrophysics Data System (ADS)

Fouda, A. S.; Ibrahim, H.; Atef, M.

Sildenafil (Viagra) was investigated as corrosion inhibitor for Zn in 1 M HCl solution using chemical and electrochemical methods at 25 °C. Electrochemical results showed that this drug is efficient inhibitor for Zn in HCl and the inhibition efficiency (IE) reached to 91% at 300 ppm. The IE increases with the drug concentration and decreases with increasing temperature. The adsorption of this drug on Zn surface follows Langmuir adsorption isotherm. The polarization plots revealed that Sildenafil acts as a mixed-type inhibitor. The thermodynamic parameters of activation and adsorption were calculated and discussed. The surface morphology of the Zn specimens was evaluated using scanning electron microscope (SEM), energy dispersive X-ray (EDX), atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR) techniques.

PEM Anchorage on Titanium Using Catechol Grafting

PubMed Central

Marie, Hélène; Barrere, Amélie; Schoentstein, Frédérique; Chavanne, Marie-Hélène; Grosgogeat, Brigitte; Mora, Laurence

2012-01-01

Background This study deals with the anchorage of polyelectrolyte films onto titanium surfaces via a cathecol-based linker for biomedical applications. Methodology The following study uses a molecule functionalized with a catechol and a carboxylic acid: 3-(3,4-dihydroxyphenyl)propanoic acid. This molecule is anchored to the TiO2 substrate via the catechol while the carboxylic acid reacts with polymers bearing amine groups. By providing a film anchorage of chemisorption type, it makes possible to deposit polyelectrolytes on the surface of titanium. Principal Findings Infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), contact angle and atomic force microscopy (AFM) measurements show that the different steps of grafting have been successfully performed. Conclusions This method based on catechol anchorage of polyelectrolytes open a window towards large possibilities of clinical applications. PMID:23226262

Atomically Dispersed Pd–O Species on CeO 2(111) as Highly Active Sites for Low-Temperature CO Oxidation

DOE PAGES

Spezzati, Giulia; Su, Yaqiong; Hofmann, Jan P.; ...

2017-09-07

Ceria-supported Pd is a promising heterogeneous catalyst for CO oxidation relevant to environmental cleanup reactions. Pd loaded onto a nanorod form of ceria exposing predominantly (111) facets is already active at 50 °C. Here we report a combination of CO-FTIR spectroscopy and theoretical calculations that allows assigning different forms of Pd on the CeO 2(111) surface during reaction conditions. Single Pd atoms stabilized in the form of PdO and PdO 2 in a CO/O 2 atmosphere participate in a catalytic cycle involving very low activation barriers for CO oxidation. In conclusion, the presence of single Pd atoms on the Pd/CeOmore » 2-nanorod, corroborated by aberration-corrected TEM and CO-FTIR spectroscopy, is considered pivotal to its high CO oxidation activity.« less

Atomically Dispersed Pd–O Species on CeO 2(111) as Highly Active Sites for Low-Temperature CO Oxidation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spezzati, Giulia; Su, Yaqiong; Hofmann, Jan P.

Ceria-supported Pd is a promising heterogeneous catalyst for CO oxidation relevant to environmental cleanup reactions. Pd loaded onto a nanorod form of ceria exposing predominantly (111) facets is already active at 50 °C. Here we report a combination of CO-FTIR spectroscopy and theoretical calculations that allows assigning different forms of Pd on the CeO 2(111) surface during reaction conditions. Single Pd atoms stabilized in the form of PdO and PdO 2 in a CO/O 2 atmosphere participate in a catalytic cycle involving very low activation barriers for CO oxidation. In conclusion, the presence of single Pd atoms on the Pd/CeOmore » 2-nanorod, corroborated by aberration-corrected TEM and CO-FTIR spectroscopy, is considered pivotal to its high CO oxidation activity.« less

Plasma enhanced ultrastable self-powered visible-blind deep ultraviolet photodetector based on atomically thin boron nitride sheets

NASA Astrophysics Data System (ADS)

Feng, Peter Xianping; Rivera, Manuel; Velazquez, Rafael; Aldalbahi, Ali

We extend our work on the use of digitally controlled plasma deposition technique to synthesize high quality boron nitride nanosheets (BNNSs). The nanoscale morphologies and layered growth characteristics of the BNNSs were characterized using scanning electron microscope, transmission electron microscopy, and atomic force microscopy. The experimental data indicated each sample consists of multiple atomically thin, highly transparent BNNSs that overlap one another with certain orientations. Purity and structural properties were characterized by Raman scattering, XRD, FTIR and XPS. Based on these characterizations, 2D BNNSs based self-powered, visible blind deep UV detectors were designed, fabricated, and tested. The bias, temperature, and humidity effects on the photocurrent strength were investigated. A significant increase of signal-to-noise ratio after plasma treatment was observed. The fabricated photodetectors presented exceptional properties: a very stable baseline and a high sensitivity to weak intensities of radiation in both UVC and UVB range while remaining visible-blind, a high signal-to-noise ratio, and excellent repeatability even when the operating temperature was up to 400 0C. The shift in cutoff wavelength was also observed. This work is supported by the Army Research Office/DoD Grant (62826-RT-REP) and the ISPP#0058 at King Saud University.

Chelant Enhanced Solution Processing for Wafer Scale Synthesis of Transition Metal Dichalcogenide Thin Films.

PubMed

Ionescu, Robert; Campbell, Brennan; Wu, Ryan; Aytan, Ece; Patalano, Andrew; Ruiz, Isaac; Howell, Stephen W; McDonald, Anthony E; Beechem, Thomas E; Mkhoyan, K Andre; Ozkan, Mihrimah; Ozkan, Cengiz S

2017-07-25

It is of paramount importance to improve the control over large area growth of high quality molybdenum disulfide (MoS 2 ) and other types of 2D dichalcogenides. Such atomically thin materials have great potential for use in electronics, and are thought to make possible the first real applications of spintronics. Here in, a facile and reproducible method of producing wafer scale atomically thin MoS 2 layers has been developed using the incorporation of a chelating agent in a common organic solvent, dimethyl sulfoxide (DMSO). Previously, solution processing of a MoS 2 precursor, ammonium tetrathiomolybdate ((NH 4 ) 2 MoS 4 ), and subsequent thermolysis was used to produce large area MoS 2 layers. Our work here shows that the use of ethylenediaminetetraacetic acid (EDTA) in DMSO exerts superior control over wafer coverage and film thickness, and the results demonstrate that the chelating action and dispersing effect of EDTA is critical in growing uniform films. Raman spectroscopy, photoluminescence (PL), x-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and high-resolution scanning transmission electron microscopy (HR-STEM) indicate the formation of homogenous few layer MoS 2 films at the wafer scale, resulting from the novel chelant-in-solution method.

Reaction of Methyl Fluoroformyl Peroxycarbonate (FC(O)OOC(O)OCH3) with Cl Atoms: Formation of Hydro-ChloroFluoro-Peroxides.

PubMed

Berasategui, Matias; Argüello, Gustavo A; Burgos Paci, Maxi A

2017-10-12

The products following Cl atom initiated reactions of FC(O)OOC(O)OCH 3 in 50-760 Torr of N 2 at 296 K were investigated using FTIR. Reaction of Cl atoms with methyl fluoroformyl peroxycarbonate proceeds mainly via attack at the methyl group, forming FC(O)OOC(O)OCH 2 • radicals. Further reaction of this kind of radical with Cl 2 forms three new compounds: FC(O)OOC(O)OCH 2 Cl, FC(O)OOC(O)OCHCl 2 , and FC(O)OOC(O)OCCl 3 , whose existence was characterized experimentally by FTIR spectroscopy assisted by ab initio calculations at the B3LYP/6-31++G(d,p) level. Relative rate techniques were used to measure k (Cl+FC(O)OOC(O)OCH3) = (4.0 ± 0.4) × 10 -14 cm 3 molecule -1 s -1 and k (Cl+FC(O)OOC(O)OCH2Cl) = (3.2 ± 0.3) × 10 -14 cm 3 molecule -1 s -1 . When the reaction is run in the presence of oxygen, the paths giving chlorinated peroxide formation are suppressed, and oxidation to (mainly) CO 2 and HCl takes place through highly oxidized intermediates with lifetimes long enough to be detected by FTIR spectroscopy.

Hydrogen Adsorption on Ga2O3 Surface: A Combined Experimental and Computational Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, Yun-xiang; Mei, Donghai; Liu, Chang-jun

In the present work, hydrogen adsorption on the Ga2O3 surfaces was investigated using Fourier transform infrared spectroscopy (FTIR) measurements and periodic density functional theory (DFT) calculations. Both the FTIR and DFT studies suggest that H2 dissociates on the Ga2O3 surfaces, producing OH and GaH species. The FTIR bands at 3730, 3700, 3630 and 3600 cm-1 are attributed to the vibration of the OH species whereas those at 2070 and 1990 cm-1 to the GaH species. The structures of the species detected in experiments are established through a comparison with the DFT calculated stretching frequencies. The O atom of the experimentallymore » detected OH species is believed to originate from the surface O3c atom. On the other hand, the H atom that binds the coordinately unsaturated Ga atom results in the experimentally detected GaH species. Dissociation of H2 on the perfect Ga2O3 surface, with the formation of both OH and GaH species, is endothermic and has an energy barrier of 0.90 eV. In contrast, H2 dissociation on the defective Ga2O3 surface with oxygen vacancies, which mainly produces GaH species, is exothermic, with an energy barrier of 0.61 eV. Accordingly, presence of the oxygen vacancies promotes H2 dissociation and production of GaH species on the Ga2O3 surfaces. Higher temperatures are expected to favor oxygen vacancy creation on the Ga2O3 surfaces, and thereby benefit the production of GaH species. This analysis is consistent with the FTIR results that the bands assigned to GaH species become stronger at higher temperatures. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.« less

Atomic Forces for Geometry-Dependent Point Multipole and Gaussian Multipole Models

PubMed Central

Elking, Dennis M.; Perera, Lalith; Duke, Robert; Darden, Thomas; Pedersen, Lee G.

2010-01-01

In standard treatments of atomic multipole models, interaction energies, total molecular forces, and total molecular torques are given for multipolar interactions between rigid molecules. However, if the molecules are assumed to be flexible, two additional multipolar atomic forces arise due to 1) the transfer of torque between neighboring atoms, and 2) the dependence of multipole moment on internal geometry (bond lengths, bond angles, etc.) for geometry-dependent multipole models. In the current study, atomic force expressions for geometry-dependent multipoles are presented for use in simulations of flexible molecules. The atomic forces are derived by first proposing a new general expression for Wigner function derivatives ∂Dlm′m/∂Ω. The force equations can be applied to electrostatic models based on atomic point multipoles or Gaussian multipole charge density. Hydrogen bonded dimers are used to test the inter-molecular electrostatic energies and atomic forces calculated by geometry-dependent multipoles fit to the ab initio electrostatic potential (ESP). The electrostatic energies and forces are compared to their reference ab initio values. It is shown that both static and geometry-dependent multipole models are able to reproduce total molecular forces and torques with respect to ab initio, while geometry-dependent multipoles are needed to reproduce ab initio atomic forces. The expressions for atomic force can be used in simulations of flexible molecules with atomic multipoles. In addition, the results presented in this work should lead to further development of next generation force fields composed of geometry-dependent multipole models. PMID:20839297

FTIR, FT-RAMAN, NMR, spectra, normal co-ordinate analysis, NBO, NLO and DFT calculation of N,N-diethyl-4-methylpiperazine-1-carboxamide molecule.

PubMed

Muthu, S; Elamurugu Porchelvi, E

2013-11-01

The Fourier Transform Infrared (FT-IR) and FT-Raman of N,N-diethyl-4-methylpiperazine-1-carboxamide (NND4MC) have been recorded and analyzed. The structure of the compound was optimized and the structural characteristics were determined by density functional theory (DFT) using B3LYP method with 6-31G(d,p) and 6-311G(d,p) basis sets. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. The theoretically predicted FT-IR and FT-Raman spectra of the title molecule have been constructed. The detailed interpretation of the vibrational spectra has been carried out with aid of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The results show that electron density (ED) in the σ(*) and π(*) antibonding orbitals and second order delocalization energies (E2) confirm the occurrence of intramolecular charge transfer (ICT) within the molecule. The electronic dipole moment (μD) and the first hyperpolarizability (βtot) values of the investigated molecule were computed using Density Functional Theory (DFT/B3LYP) with 6-31G(d,p) and 6-311G(d,p) basis sets. The calculated results also show that the NND4MC molecule may have microscopy nonlinear optical (NLO) behavior with non zero values. Mulliken atomic charges of NND4MC were calculated. The (13)C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by the gauge independent atomic orbital (GIAO) method and compared with experimental results. The UV-Vis spectrum of the compound was recorded. The theoretical electronic absorption spectra have been calculated by using CIS, TD-DFT methods. A study on the electronic properties, such as HOMO and LUMO energies, molecular electrostatic potential (MEP) were also performed. Copyright © 2013 Elsevier B.V. All rights reserved.

How do silanes affect the lubricating properties of cationic double chain surfactant on silica surfaces?

PubMed

Beauvais, Muriel; Serreau, Laurence; Heitz, Caroline; Barthel, Etienne

2009-03-01

The effect of an aminosilane on the lubricant properties of a C(18) double-chained cationic surfactant has been investigated in the context of glass fiber forming process. The surfactant adsorption was studied on silica by Fourier transform infrared (FT-IR) spectroscopy in the attenuated total reflexion (ATR) mode as a function of the aminosilane concentration in an organic water based formulation (sizing) used to coat the glass fibers during the process. A reciprocating ball-on-plate tribometer was used to compare friction properties of silica in contact with the aminosilane-surfactant mixture and in presence of each component of the sizing. Surface forces were measured between silica and an atomic force microscope (AFM) silicon nitride tip in the sizing and in the pure cationic surfactant solution. The aminosilane on its own has no lubricant property and reduces or even suppresses the cationic surfactant adsorption on silica. However, the silica-silica contact is lubricated even if the infrared spectroscopy does not detect any surfactant adsorption. The repeated contacts and shear due to the friction experiment itself induce accumulation, organization and compactness of surfactant bilayers.

Effects and mechanism of dual-frequency power ultrasound on the molecular weight distribution of corn gluten meal hydrolysates.

PubMed

Jin, Jian; Ma, Haile; Wang, Bei; Yagoub, Abu El-Gasim A; Wang, Kai; He, Ronghai; Zhou, Cunshan

2016-05-01

The impact of dual-frequency power ultrasound (DPU) on the molecular weight distribution (MWD) of corn gluten meal (CGM) hydrolysates and its mechanism were investigated in the present study. The mechanism was studied from aspects of structural and nano-mechanical characteristics of the major protein fractions of CGM, viz. zein and glutelin. The results of molecular weight distribution indicated that DPU pretreatment of CGM was beneficial to the preparation of peptides with molecular weights of 200-1000Da. Moreover, FTIR spectral analysis and atomic force microscopy characterization showed that the DPU pretreatment changed the contents of secondary structure of proteins, decreased the particle height and surface roughness of glutelin, reduced the Young's modulus and stiffness of zein while increased its adhesion force. In conclusion, DPU pretreatment of proteins before proteolysis is an efficient alternative method to produce short-chain peptides because of its positive effects originating from acoustic cavitation on the molecular conformation, nano-structures and nano-mechanical properties of proteins as well. Copyright © 2015 Elsevier B.V. All rights reserved.

Magnetic nanocomposites based on phosphorus-containing polymers—structural characterization and thermal analysis

NASA Astrophysics Data System (ADS)

Alosmanov, R. M.; Szuwarzyński, M.; Schnelle-Kreis, J.; Matuschek, G.; Magerramov, A. M.; Azizov, A. A.; Zimmermann, R.; Zapotoczny, S.

2018-04-01

Fabrication of magnetic nanocomposites containing iron oxide nanoparticles formed in situ within a phosphorus-containing polymer matrix as well as its structural characterization and its thermal degradation is reported here. Comparative structural studies of the parent polymer and nanocomposites were performed using FTIR spectroscopy, x-ray diffraction, and atomic force microscopy. The results confirmed the presence of dispersed iron oxide magnetic nanoparticles in the polymer matrix. The formed composite combines the properties of porous polymer carriers and magnetic particles enabling easy separation and reapplication of such polymeric carriers used in, for example, catalysis or environmental remediation. Studies on thermal degradation of the composites revealed that the process proceeds in three stages while a significant influence of the embedded magnetic particles on that process was observed in the first two stages. Magnetic force microscopy studies revealed that nanocomposites and its calcinated form have strong magnetic properties. The obtained results provide a comprehensive characterization of magnetic nanocomposites and the products of their calcination that are important for their possible applications as sorbents (regeneration conditions, processing temperature, disposal, etc).

Substituted copper phthalocyanine/multiwalled carbon nanotubes hybrid material for Cl{sub 2} sensing application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Anshul Kumar, E-mail: dramanmahajan@yahoo.co.in; Saini, Rajan, E-mail: dramanmahajan@yahoo.co.in; Singh, Rajinder, E-mail: dramanmahajan@yahoo.co.in

2014-04-24

In this work, hybrid of soluble copper phthalocyanine (CuPcOC{sub 8}) and functionalized multi-walled carbon nanotubes (MWCNTs) has been synthesized. The formation of CuPcOC{sub 8}-MWCNTs hybrid is confirmed by atomic force microscopy, UV-Visible and FTIR spectroscopy. Subsequently, a chemi-resistive sensor is fabricated by drop casting CuPcOC{sub 8}-MWCNTs hybrid onto glass substrate. It has been demonstrated that CuPcOC{sub 8}-MWCNTs hybrid is highly selective towards Cl{sub 2} gas with minimum detection limit of 100 ppb. The response of sensor increases linearly with increase in the concentration of Cl{sub 2} gas. For 2000 ppb of Cl{sub 2}, CuPcOC{sub 8}-MWCNTs hybrid gives a response asmore » large as 53% in 40 seconds.« less

Investigation on single walled carbon nanotube thin films deposited by Langmuir Blodgett method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vishalli,, E-mail: vishalli-2008@yahoo.com; Dharamvir, Keya; Kaur, Ramneek

2015-05-15

Langmuir Blodgett is a technique to deposit a homogeneous film with a fine control over thickness and molecular organization. Thin films of functionalized SWCNTs have been prepared by Langmuir Blodgett method. The good surface spreading properties of SWCNTs at air/water interface are indicated by surface pressure-area isotherm and the monolayer formed on water surface is transferred onto the quartz substrate by vertical dipping. A multilayer film is thus obtained in a layer by layer manner. The film is characterized by Atomic Force Microscope (AFM), UV-Vis-NIR spectroscopy and FTIR.AFM shows the surface morphology of the deposited film. UV-Vis-NIR spectroscopy shows themore » characteristic peaks of semiconducting SWCNTs. The uniformity of LB film can be used further in understanding the optical and electrical behavior of these materials.« less

Synthesis, physicochemical and optical properties of bis-thiosemicarbazone functionalized graphene oxide

NASA Astrophysics Data System (ADS)

Kumar, Santosh; Wani, Mohmmad Y.; Arranja, Claudia T.; Castro, Ricardo A. E.; Paixão, José A.; Sobral, Abilio J. F. N.

2018-01-01

Fluorescent materials are important for low-cost opto-electronic and biomedical sensor devices. In this study we present the synthesis and characterization of graphene modified with bis-thiosemicarbazone (BTS). This new material was characterized using Fourier transform infrared spectroscopy (FT-IR), Ultraviolet-visible (UV-Vis) and Raman spectroscopy techniques. Further evaluation by X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and atomic-force microscopy (AFM) allowed us to fully characterize the morphology of the fabricated material. The average height of the BTSGO sheet is around 10 nm. Optical properties of BTSGO evaluated by photoluminescence (PL) spectroscopy showed red shift at different excitation wavelength compared to graphene oxide or bisthiosemicarbazide alone. These results strongly suggest that BTSGO material could find potential applications in graphene based optoelectronic devices.

Biocidal action of ozone-treated polystyrene surfaces on vegetative and sporulated bacteria

NASA Astrophysics Data System (ADS)

Mahfoudh, Ahlem; Barbeau, Jean; Moisan, Michel; Leduc, Annie; Séguin, Jacynthe

2010-03-01

Surfaces of materials can be modified to ensure specific interaction features with microorganisms. The current work discloses biocidal properties of polystyrene (PS) Petri-dish surfaces that have been exposed to a dry gaseous-ozone flow. Such treated PS surfaces are able to inactivate various species of vegetative and sporulated bacteria on a relatively short contact time. Denaturation of proteins seems likely based on a significant loss of enzymatic activity of the lysozyme protein. Characterization of these surfaces by atomic-force microscopy (AFM), Fourier-transform infra-red (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) reveals specific structural and chemical modifications as compared to untreated PS. Persistence of the biocidal properties of these treated surfaces is observed. This ozone-induced process is technically simple to achieve and does not require active precursors as in grafting.

Optimization and characterization of biomolecule immobilization on silicon substrates using (3-aminopropyl)triethoxysilane (APTES) and glutaraldehyde linker

NASA Astrophysics Data System (ADS)

Gunda, Naga Siva Kumar; Singh, Minashree; Norman, Lana; Kaur, Kamaljit; Mitra, Sushanta K.

2014-06-01

In the present work, we developed and optimized a technique to produce a thin, stable silane layer on silicon substrate in a controlled environment using (3-aminopropyl)triethoxysilane (APTES). The effect of APTES concentration and silanization time on the formation of silane layer is studied using spectroscopic ellipsometry and Fourier transform infrared spectroscopy (FTIR). Biomolecules of interest are immobilized on optimized silane layer formed silicon substrates using glutaraldehyde linker. Surface analytical techniques such as ellipsometry, FTIR, contact angle measurement system, and atomic force microscopy are employed to characterize the bio-chemically modified silicon surfaces at each step of the biomolecule immobilization process. It is observed that a uniform, homogenous and highly dense layer of biomolecules are immobilized with optimized silane layer on the silicon substrate. The developed immobilization method is successfully implemented on different silicon substrates (flat and pillar). Also, different types of biomolecules such as anti-human IgG (rabbit monoclonal to human IgG), Listeria monocytogenes, myoglobin and dengue capture antibodies were successfully immobilized. Further, standard sandwich immunoassay (antibody-antigen-antibody) is employed on respective capture antibody coated silicon substrates. Fluorescence microscopy is used to detect the respective FITC tagged detection antibodies bound to the surface after immunoassay.

Green synthesis of silver nanoparticles using Mentha pulegium and investigation of their antibacterial, antifungal and anticancer activity.

PubMed

Kelkawi, Ali Hamad Abd; Abbasi Kajani, Abolghasem; Bordbar, Abdol-Khalegh

2017-06-01

A simple and eco-friendly method for efficient synthesis of stable colloidal silver nanoparticles (AgNPs) using Mentha pulegium extracts is described. A series of reactions was conducted using different types and concentrations of plant extract as well as metal ions to optimize the reaction conditions. AgNPs were characterized by using UV-vis spectroscopy, transmission electron microscopy, atomic force microscopy, dynamic light scattering, zetasizer, energy-dispersive X-ray spectroscopy (EDAX) and Fourier transform infrared spectroscopy (FTIR). At the optimized conditions, plate shaped AgNPs with zeta potential value of -15.7 and plasmon absorption maximum at 450 nm were obtained using high concentration of aqueous extract. Efficient adsorption of organic compounds on the nanoparticles was confirmed by FTIR and EDAX. The biogenic AgNPs displayed promising antibacterial activity on Escherichia coli , Staphylococcus aureus , and Streptococcus pyogenes . The highest antibacterial activity of 25 µg mL-1 was obtained for all the strains using aqueous extract synthesized AgNPs. The aqueous extract synthesised AgNPs also showed considerable antifungal activity against fluconazole resistant Candida albicans . The cytotoxicity assay revealed considerable anticancer activity of AgNPs on HeLa and MCF-7 cancer cells. Overall results indicated high potential of M. pulegium extract to synthesis high quality AgNPs for biomedical applications.

Permeability and selectivity of reverse osmosis membranes: correlation to swelling revisited.

PubMed

Dražević, Emil; Košutić, Krešimir; Freger, Viatcheslav

2014-02-01

Membrane swelling governs both rejection of solutes and permeability of polymeric membranes, however very few data have been available on swelling in water of salt-rejecting reverse osmosis (RO) membranes. This study assesses swelling, thickness and their relation to water permeability for four commercial polyamide (PA) RO membranes (SWC4+, ESPA1, XLE and BW30) using atomic force microscopy (AFM) and attenuated total reflection Fourier transform IR spectroscopy (ATR-FTIR). ATR-FTIR offered a significantly improved estimate of the actual barrier thickness of PA, given AFM is biased by porosity ("fluffy parts") or wiggling of the active layer or presence of a coating layer. Thus obtained intrinsic permeability (permeability times thickness) and selectivity of aromatic polyamides plotted versus swelling falls well on a general trend, along with previously reported data on several common materials showing RO and NF selectivity. The observed general trend may be rationalized by viewing the polymers as a random composite medium containing molecularly small pores. The results suggest that the combination of a rigid low dielectric matrix, limiting the pore size, with multiple hydrophilic H-bonding sites may be a common feature of RO/NF membranes, allowing both high permeability and selectivity. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

Property of filler-loaded magnetic ferrite from plastic waste bottle used to treat municipal domestic sewage.

PubMed

Zhao, Ru-Jin; Gong, Li-Ying; Zhu, Hai-Dong; Liu, Qiao; Xu, Li-Xia; Lu, Lu; Yang, Qi-Zhi

2018-06-01

The present work investigates the properties of self-made magnetic filler from plastic waste bottle and explores a new technology approach of waste plastic resource utilization. The magnetic filler was prepared by air plasma modification and loading magnetic ferrite on the plastic strip from waste plastic bottle. The surface properties of magnetic filler were characterized by Atomic Force Microscope (AFM), contact angle system and Fourier Transform Infrared (FTIR). AFM images of original and modified plastic strip showed that low-temperature plasma treatment markedly increased the surface roughness of plastic strip. The mean roughness (Ra) of plastic strip rose from 1.116 to 5.024 nm. FTIR spectra indicated that a lot of polar oxygenic groups were introduced onto the surface of plastic by plasma modification. Modification by low-temperature plasma increased the hydrophilicity of plastic strip surface. When treatment time is 40 s, water contact angle of plastic strip surface reduced from 78.2° of original plastic strip to 25.3°. When used in bioreactor, magnetic filler had very favorable microenvironment for microorganism growth. Magnetic filler was more efficient for removing chemical oxygen demand (COD) and [Formula: see text] in sewage than nonmagnetic filler. The resource utilization of plastic wastes will become reality if the magnetic filler is applied widely.

Direct synthesis of nitrogen-containing carbon nanotubes on carbon paper for fuel cell electrode

NASA Astrophysics Data System (ADS)

Yin, Wong Wai; Daud, Wan Ramli Wan; Mohamad, Abu Bakar; Kadhum, Abdul Amir Hassan; Majlan, Edy Herianto; Shyuan, Loh Kee

2012-06-01

Organic catalyst has recently been identified as the potential substitution for expensive platinum electrocatalyst for fuel cell application. Numerous studies have shown that the nitrogen-containing carbon nanotubes (N-CNT) can be synthesized through spray pyrolysis or floating chemical vapor deposition (CVD) technique using various type of organometallic as precursors. This paper presents the method of synthesis and the initial findings of the growth of N-CNT directly on carbon paper using a modified CVD technique. In this research, nickel (II) phthalocyanines (Ni-Pc) as precursor was dissolved in ethanol solvent, stirred and sonicated to become homogenized. The solution was poured into a bubbler and heated up to allow the mixture to vaporize. Subsequently, the solution vapor was flowed into the tubical reactor maintained at 900°C. Carbon paper sputtered with nickel nanoparticles was used as the substrate. The synthesized sample was examined through Field Emission Scanning Electron Microscopy (FESEM), Atomic Force Microscopy (AFM) and Fourier Transform Infra-Red (FTIR). Long, entangled and compartmentalized nanotubes with tube diameter ranging 23-27 nm were found covered the carbon paper surface with approximate of 5.5-6.0 μm in thickness. EDX analysis has successfully showed the presence of nitrogen in the carbon nanotube. FTIR analysis showed the presence of the C-N bond on CNT.

Protein-resistant polymer coatings obtained by matrix assisted pulsed laser evaporation

NASA Astrophysics Data System (ADS)

Rusen, L.; Mustaciosu, C.; Mitu, B.; Filipescu, M.; Dinescu, M.; Dinca, V.

2013-08-01

Adsorption of proteins and polysaccharides is known to facilitate microbial attachment and subsequent formation of biofilm on surfaces that ultimately results in its biofouling. Therefore, protein repellent modified surfaces are necessary to block the irreversible attachment of microorganisms. Within this context, the feasibility of using the Poly(ethylene glycol)-block-poly(ɛ-caprolactone) methyl ether (PEG-block-PCL Me) copolymer as potential protein-resistant coating was explored in this work. The films were deposited using Matrix Assisted Pulsed Laser Evaporation (MAPLE), a technique that allows good control of composition, thickness and homogeneity. The chemical and morphological characteristics of the films were examined using Fourier Transform Infrared Spectroscopy (FTIR), contact angle measurements and Atomic Force Microscopy (AFM). The FTIR data demonstrates that the functional groups in the MAPLE-deposited films remain intact, especially for fluences below 0.5 J cm-2. Optical Microscopy and AFM images show that the homogeneity and the roughness of the coatings are related to both laser parameters (fluence, number of pulses) and target composition. Protein adsorption tests were performed on the PEG-block-PCL Me copolymer coated glass and on bare glass surface as a control. The results show that the presence of copolymer as coating significantly reduces the adsorption of proteins.

Bio-functionalization of electro-synthesized polypyrrole surface by heme enzyme using a mixture of Nafion and glutaraldehyde as synergetic immobilization matrix: Conformational characterization and electrocatalytic studies

NASA Astrophysics Data System (ADS)

ElKaoutit, Mohammed; Naranjo-Rodriguez, Ignacio; Domínguez, Manuel; Hidalgo-Hidalgo-de-Cisneros, José Luis

2011-10-01

Use of a mixture of Nafion and glutaraldehyde as new immobilization matrix was described. The percentage of Nafion was optimized to prevent denaturation of horseradish peroxidase enzyme after its crosslinkage with glutaraldehyde on electro-synthesized polypyrrole surface. Topographic study by Atomic Force Microscopy (AFM) shows that the enzyme seems to have been introduced inside the ionic cluster of Nafion. The characterization of the resulting bio-interfaces by UV-vis and FT-IR shows that the intra-crosslinkage phenomena caused by the use of glutaraldehyde can be eliminated by the optimization of the concentration of Nafion additive. The secondary structure contents of native and immobilized enzyme were analyzed by a Gaussian curve fitting of the respective FT-IR spectra in the amide I region. Immobilized enzyme presented notable increasing percentages of globular and short helical structure compared with native enzyme. This indicates that immobilized enzyme was folded which is in accordance with AFM studies and supports the enzyme entrance inside ionic clutter of Nafion. Thanks to synergic effects of the polypyrrole conducting polymer and the perfluorosulfonic acid polymer Nafion, HRP enzyme was immobilized in its "native" state, the resulting biosensor was able to sense peroxide without any chemical mediator and can be categorized as third generation.

Tomato GDSL1 Is Required for Cutin Deposition in the Fruit Cuticle[C][W

PubMed Central

Girard, Anne-Laure; Mounet, Fabien; Lemaire-Chamley, Martine; Gaillard, Cédric; Elmorjani, Khalil; Vivancos, Julien; Runavot, Jean-Luc; Quemener, Bernard; Petit, Johann; Germain, Véronique; Rothan, Christophe; Marion, Didier; Bakan, Bénédicte

2012-01-01

The plant cuticle consists of cutin, a polyester of glycerol, hydroxyl, and epoxy fatty acids, covered and filled by waxes. While the biosynthesis of cutin building blocks is well documented, the mechanisms underlining their extracellular deposition remain unknown. Among the proteins extracted from dewaxed tomato (Solanum lycopersicum) peels, we identified GDSL1, a member of the GDSL esterase/acylhydrolase family of plant proteins. GDSL1 is strongly expressed in the epidermis of growing fruit. In GDSL1-silenced tomato lines, we observed a significant reduction in fruit cuticle thickness and a decrease in cutin monomer content proportional to the level of GDSL1 silencing. A significant decrease of wax load was observed only for cuticles of the severely silenced transgenic line. Fourier transform infrared (FTIR) analysis of isolated cutins revealed a reduction in cutin density in silenced lines. Indeed, FTIR-attenuated total reflectance spectroscopy and atomic force microscopy imaging showed that drastic GDSL1 silencing leads to a reduction in ester bond cross-links and to the appearance of nanopores in tomato cutins. Furthermore, immunolabeling experiments attested that GDSL1 is essentially entrapped in the cuticle proper and cuticle layer. These results suggest that GDSL1 is specifically involved in the extracellular deposition of the cutin polyester in the tomato fruit cuticle. PMID:22805434

Tomato GDSL1 is required for cutin deposition in the fruit cuticle.

PubMed

Girard, Anne-Laure; Mounet, Fabien; Lemaire-Chamley, Martine; Gaillard, Cédric; Elmorjani, Khalil; Vivancos, Julien; Runavot, Jean-Luc; Quemener, Bernard; Petit, Johann; Germain, Véronique; Rothan, Christophe; Marion, Didier; Bakan, Bénédicte

2012-07-01

The plant cuticle consists of cutin, a polyester of glycerol, hydroxyl, and epoxy fatty acids, covered and filled by waxes. While the biosynthesis of cutin building blocks is well documented, the mechanisms underlining their extracellular deposition remain unknown. Among the proteins extracted from dewaxed tomato (Solanum lycopersicum) peels, we identified GDSL1, a member of the GDSL esterase/acylhydrolase family of plant proteins. GDSL1 is strongly expressed in the epidermis of growing fruit. In GDSL1-silenced tomato lines, we observed a significant reduction in fruit cuticle thickness and a decrease in cutin monomer content proportional to the level of GDSL1 silencing. A significant decrease of wax load was observed only for cuticles of the severely silenced transgenic line. Fourier transform infrared (FTIR) analysis of isolated cutins revealed a reduction in cutin density in silenced lines. Indeed, FTIR-attenuated total reflectance spectroscopy and atomic force microscopy imaging showed that drastic GDSL1 silencing leads to a reduction in ester bond cross-links and to the appearance of nanopores in tomato cutins. Furthermore, immunolabeling experiments attested that GDSL1 is essentially entrapped in the cuticle proper and cuticle layer. These results suggest that GDSL1 is specifically involved in the extracellular deposition of the cutin polyester in the tomato fruit cuticle.

FTIR Monitoring Of Curing Of Composites

NASA Technical Reports Server (NTRS)

Druy, Mark A.; Stevenson, William A.; Young, Philip R.

1990-01-01

Infrared-sensing optical fiber system developed to monitor principal infrared absorption bands resulting from vibrations of atoms and molecules as chemical bonds form when resin cured. System monitors resin chemistry more directly. Used to obtain Fourier transform infrared (FTIR) spectrum from graphite fiber/polyimide matrix resin prepreg. Embedded fiber optic FTIR sensor used to indicate state of cure of thermosetting composite material. Developed primarily to improve quality of advanced composites, many additional potential applications exist because principal of operation applicable to all organic materials and most inorganic gases. Includes monitoring integrities of composite materials in service, remote sensing of hazardous materials, and examination of processes in industrial reactors and furnaces.

Interplay between Switching Driven by the Tunneling Current and Atomic Force of a Bistable Four-Atom Si Quantum Dot.

PubMed

Yamazaki, Shiro; Maeda, Keisuke; Sugimoto, Yoshiaki; Abe, Masayuki; Zobač, Vladimír; Pou, Pablo; Rodrigo, Lucia; Mutombo, Pingo; Pérez, Ruben; Jelínek, Pavel; Morita, Seizo

2015-07-08

We assemble bistable silicon quantum dots consisting of four buckled atoms (Si4-QD) using atom manipulation. We demonstrate two competing atom switching mechanisms, downward switching induced by tunneling current of scanning tunneling microscopy (STM) and opposite upward switching induced by atomic force of atomic force microscopy (AFM). Simultaneous application of competing current and force allows us to tune switching direction continuously. Assembly of the few-atom Si-QDs and controlling their states using versatile combined AFM/STM will contribute to further miniaturization of nanodevices.

Spectroscopic (FTIR, FT-Raman), molecular electrostatic potential, NBO and HOMO-LUMO analysis of P-bromobenzene sulfonyl chloride based on DFT calculations

NASA Astrophysics Data System (ADS)

Jeyavijayan, S.

2015-02-01

The FTIR and FT-Raman spectra of P-bromobenzene sulfonyl chloride (P-BBSC) have been recorded in the regions 4000-400 cm-1 and 3500-50 cm-1, respectively. Utilizing the observed FTIR and FT-Raman data, a complete vibrational assignment and analysis of the fundamental modes of the compound were carried out. The optimum molecular geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities, were calculated by density functional theory (DFT/B3LYP) method. A good agreement between experimental and calculated normal modes of vibrations has been observed. A detailed interpretation of the infrared and Raman spectra of P-BBSC is also reported based on total energy distribution (TED). Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital (NBO) analysis. The MEP map shows the negative potential sites are on oxygen atoms as well as the positive potential sites are around the hydrogen atoms. The UV-vis spectral analysis of P-BBSC has also been done which confirms the charge transfer of the molecule.

Vibrational and structural study of onopordopicrin based on the FTIR spectrum and DFT calculations.

PubMed

Chain, Fernando E; Romano, Elida; Leyton, Patricio; Paipa, Carolina; Catalán, César A N; Fortuna, Mario; Brandán, Silvia Antonia

2015-01-01

In the present work, the structural and vibrational properties of the sesquiterpene lactone onopordopicrin (OP) were studied by using infrared spectroscopy and density functional theory (DFT) calculations together with the 6-31G(∗) basis set. The harmonic vibrational wavenumbers for the optimized geometry were calculated at the same level of theory. The complete assignment of the observed bands in the infrared spectrum was performed by combining the DFT calculations with Pulay's scaled quantum mechanical force field (SQMFF) methodology. The comparison between the theoretical and experimental infrared spectrum demonstrated good agreement. Then, the results were used to predict the Raman spectrum. Additionally, the structural properties of OP, such as atomic charges, bond orders, molecular electrostatic potentials, characteristics of electronic delocalization and topological properties of the electronic charge density were evaluated by natural bond orbital (NBO), atoms in molecules (AIM) and frontier orbitals studies. The calculated energy band gap and the chemical potential (μ), electronegativity (χ), global hardness (η), global softness (S) and global electrophilicity index (ω) descriptors predicted for OP low reactivity, higher stability and lower electrophilicity index as compared with the sesquiterpene lactone cnicin containing similar rings. Copyright © 2015 Elsevier B.V. All rights reserved.

Photochemistry of formaldoxime−nitrous acid complexes in an argon matrix: identification of formaldoxime nitrite.

PubMed

Golec, Barbara; Bil, Andrzej; Mielke, Zofia

2009-08-27

We have studied the structure and photochemistry of the formaldoxime−nitrous acid system (CH2NOH−HONO) by help of FTIR matrix isolation spectroscopy and ab initio methods. The MP2/6-311++G(2d,2p) calculations show stability of six isomeric CH2NOH···HONO complexes. The FTIR spectra evidence formation of two hydrogen bonded complexes in an argon matrix whose structures are determined by comparison of the experimental spectra with the calculated ones for the six stable complexes. In the matrix there is present the most stable cyclic complex with two O−H···N bonds; a strong bond is formed between the OH group of HONO and the N atom of CH2NOH and the weaker one between the OH group of CH2NOH and the N atom of HONO. In the other complex present in the matrix the OH group of formaldoxime is attached to the OH group of HONO forming an O−H···O bond. The irradiation of the CH2NOH···HONO complexes with the filtered output of the mercury lamp (λ > 345 nm) leads to the formation of formaldoxime nitrite, CH2NONO, and its two isomeric complexes with water. The main product is the CH2NONO···H2O complex in which water is hydrogen bonded to the N atom of the C═N group. The identity of the photoproducts is confirmed by both FTIR spectroscopy and MP2 or QCISD(full) calculations with the 6-311++G(2d,2p) basis set. The intermediate in this reaction is iminoxyl radical that is formed by abstraction of hydrogen atom from formaldoxime OH group by an OH radical originating from HONO photolysis.

Characterization of MAPLE deposited WO3 thin films for electrochromic applications

NASA Astrophysics Data System (ADS)

Boyadjiev, S. I.; Stefan, N.; Szilágyi, I. M.; Mihailescu, N.; Visan, A.; Mihailescu, I. N.; Stan, G. E.; Besleaga, C.; Iliev, M. T.; Gesheva, K. A.

2017-01-01

Tungsten trioxide (WO3) is a widely studied material for electrochromic applications. The structure, morphology and optical properties of WO3 thin films, grown by matrix assisted pulsed laser evaporation (MAPLE) from monoclinic WO3 nano-sized particles, were investigated for their possible application as electrochromic layers. A KrF* excimer (λ=248 nm, ζFWHM=25 ns) laser source was used in all experiments. The MAPLE deposited WO3 thin films were studied by atomic force microscopy (AFM), grazing incidence X-ray diffraction (GIXRD) and Fourier transform infrared spectroscopy (FTIR). Cyclic voltammetry measurements were also performed, and the coloring and bleaching were observed. The morpho-structural investigations disclosed the synthesis of single-phase monoclinic WO3 films consisting of crystalline nano-grains embedded in an amorphous matrix. All thin films showed good electrochromic properties, thus validating application of the MAPLE deposition technique for the further development of electrochromic devices.

Studies of Reduced Graphene Oxide and Graphite Oxide in the Aspect of Their Possible Application in Gas Sensors

PubMed Central

Drewniak, Sabina; Muzyka, Roksana; Stolarczyk, Agnieszka; Pustelny, Tadeusz; Kotyczka-Morańska, Michalina; Setkiewicz, Maciej

2016-01-01

The paper presents the results of investigations on resistance structures based on graphite oxide (GRO) and graphene oxide (rGO). The subject matter of the investigations was thaw the sensitivity of the tested structures was affected by hydrogen, nitrogen dioxide and carbon dioxide. The experiments were performed at a temperature range from 30 °C to 150 °C in two carrier gases: nitrogen and synthetic air. The measurements were also aimed at characterization of the graphite oxide and graphene oxide. In our measurements we used (among others) techniques such as: Atomic Force Microscopy (AFM); Scanning Electron Microscopy (SEM); Raman Spectroscopy (RS); Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Microscopy (XPS). The data resulting from the characterizations of graphite oxide and graphene oxide have made it possible to interpret the obtained results from the point of view of physicochemical changes occurring in these structures. PMID:26784198

Studies of Reduced Graphene Oxide and Graphite Oxide in the Aspect of Their Possible Application in Gas Sensors.

PubMed

Drewniak, Sabina; Muzyka, Roksana; Stolarczyk, Agnieszka; Pustelny, Tadeusz; Kotyczka-Morańska, Michalina; Setkiewicz, Maciej

2016-01-15

The paper presents the results of investigations on resistance structures based on graphite oxide (GRO) and graphene oxide (rGO). The subject matter of the investigations was thaw the sensitivity of the tested structures was affected by hydrogen, nitrogen dioxide and carbon dioxide. The experiments were performed at a temperature range from 30 °C to 150 °C in two carrier gases: nitrogen and synthetic air. The measurements were also aimed at characterization of the graphite oxide and graphene oxide. In our measurements we used (among others) techniques such as: Atomic Force Microscopy (AFM); Scanning Electron Microscopy (SEM); Raman Spectroscopy (RS); Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Microscopy (XPS). The data resulting from the characterizations of graphite oxide and graphene oxide have made it possible to interpret the obtained results from the point of view of physicochemical changes occurring in these structures.

Nitrated graphene oxide and its catalytic activity in thermal decomposition of ammonium perchlorate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Wenwen; Luo, Qingping; Duan, Xiaohui

2014-02-01

Highlights: • The NGO was synthesized by nitrifying homemade GO. • The N content of resulted NGO is up to 1.45 wt.%. • The NGO can facilitate the decomposition of AP and release much heat. - Abstract: Nitrated graphene oxide (NGO) was synthesized by nitrifying homemade GO with nitro-sulfuric acid. Fourier transform infrared spectroscopy (FTIR), laser Raman spectroscopy, CP/MAS {sup 13}C NMR spectra and X-ray photoelectron spectroscopy (XPS) were used to characterize the structure of NGO. The thickness and the compositions of GO and NGO were analyzed by atomic force microscopy (AFM) and elemental analysis (EA), respectively. The catalytic effectmore » of the NGO for the thermal decomposition of ammonium perchlorate (AP) was investigated by differential scanning calorimetry (DSC). Adding 10% of NGO to AP decreases the decomposition temperature by 106 °C and increases the apparent decomposition heat from 875 to 3236 J/g.« less

The fabrication of visible light responsive Ag-SiO2 co-doped TiO2 thin films by the sol-gel method

NASA Astrophysics Data System (ADS)

Dam Le, Duy; Dung Dang, Thi My; Thang Chau, Vinh; Chien Dang, Mau

2010-03-01

In this study we have successfully deposited Ag-SiO2 co-doped TiO2 thin films on glass substrates by the sol-gel method. After being coated by a dip coating method, the film was transparent, smooth and had strong adhesion on the glass surface. The deposited film was characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-Vis), a scanning electron microscope (SEM) and atomic force microscope (AFM) to investigate its crystallization, transmittance and surface structure. The antifogging ability is explained by the contact angle of water on the surface of the glass substrates under visible-light. The obtained results show that Ag-SiO2 co-doped TiO2 film has potential applications for self cleaning and anti-bacterial ceramic tiles.

Cytotoxic and antimicrobial effect of biosynthesized silver nanoparticles using the fruit extract of Ribes nigrum

NASA Astrophysics Data System (ADS)

Dobrucka, Renata; Kaczmarek, Mariusz; Dlugaszewska, Jolanta

2018-06-01

The present study reveals the efficiency of the fruit extract of Ribes nigrum in the green synthesis of silver nanoparticles (Ag-NPs). Biosynthesized Ag-NPs were characterized by UV-vis, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The nanoparticles were found to be 5–10 nm. In some places, the particles were agglomerated. The nanoparticles showed strong bactericidal activity and fungicidal activity against dermatophytes Trichophyton rubrum ATCC 28188. Moreover, the A549 and CCD39Lu cells under the influence of the highest concentration of nanoparticles synthesized using the fruit extract of Ribes nigrum showed the maximum mortality. Also, the results indicate that Ag-NPs synthesized using the fruit extract of Ribes nigrum exhibit efficiency in therapy of human non-small cell lung cancer A549.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Padmaja, S.; Jayakumar, S., E-mail: s_jayakumar_99@yahoo.com; Balaji, R.

Cadmium Sulphide (CdS) nanoparticles were reinforced in Poly(ethylene Oxide) (PEO) and Poly(methyl methacrylate) (PMMA) matrices by in situ technique. The presence of CdS in PEO and PMMA matrix was confirmed using X-ray photoelectron spectroscopy (XPS). Fourier Transform Infrared spectroscopy (FTIR) analysis disclosed the co-ordination of CdS in the matrices. Thermal analysis of the nanocomposites was carried out using Differential Scanning calorimetric studies (DSC). The optical studies using UV–vis spectroscopy were carried out to find the band gap of the materials and the absorption onset. The CdS particle size in the matrices was found by Effective Mass Approximation (EMA) model usingmore » the band gap values and was confirmed by TEM studies. The surface trapped emissions of the nanocomposites were observed from the photoluminescence (PL) spectra. The distribution of CdS particles in the polymer matrices were presented by Atomic force microscopic studies (AFM).« less

Effect of Aspergillus versicolor strain JASS1 on low density polyethylene degradation

NASA Astrophysics Data System (ADS)

Gajendiran, A.; Subramani, S.; Abraham, J.

2017-11-01

Low density polyethylene (LDPE) waste disposal remains one of the major environmental concerns faced by the world today. In past decades, major focus has been given to enhance the biodegradation of LDPE by microbial species. In this present study, Aspergillus versicolor with the ability to degrade LDPE was isolated from municipal landfill area using enrichment technique. Based on 18S rRNA gene sequencing confirmed its identity as Aspergillus versicolor. The biodegradation study was carried out for 90 d in M1 medium. The degradation behaviour of LDPE films by Aspergillus versicolor strain JASS1 were confirmed by weight loss, CO2 evolution, Scanning electron microscopy (SEM) analysis, Atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR) technique. From current investigation, it can be concluded that our isolated strain JASS1 had the potential to degrade LDPE films and it can be useful in solving the problem caused by polyethylene in the environment.

Cleaning efficacy of hydroxypropyl-beta-cyclodextrin for biofouling reduction on reverse osmosis membranes.

PubMed

Alayande, Abayomi Babatunde; Kim, Lan Hee; Kim, In S

2016-01-01

In this study, an environmentally friendly compound, hydroxypropyl-beta-cyclodextrin (HP-β-CD) was applied to clean reverse osmosis (RO) membranes fouled by microorganisms. The cleaning with HP-β-CD removed the biofilm and resulted in a flux recovery ratio (FRR) of 102%. As cleaning efficiency is sometimes difficult to determine using flux recovery data alone, attached bacterial cells and extracellular polymeric substances (EPS) were quantified after cleaning the biofouled membrane with HP-β-CD. Membrane surface characterization using scanning electron microscopy (SEM), attenuated total reflectance Fourier transform infrared (ATR-FTIR) and atomic force microscopy (AFM) confirmed the effectiveness of HP-β-CD in removal of biofilm from the RO membrane surface. Finally, a comparative study was performed to investigate the competitiveness of HP-β-CD with other known cleaning agents such as sodium dodecyl sulfate (SDS), ethylenediaminetetraacetic acid (EDTA), Tween 20, rhamnolipid, nisin, and surfactin. In all cases, HP-β-CD was superior.

Experimental and Theoretical Investigation of Thiazolyl Blue as a Corrosion Inhibitor for Copper in Neutral Sodium Chloride Solution.

PubMed

Feng, Li; Zhang, Shengtao; Qiang, Yujie; Xu, Yue; Guo, Lei; Madkour, Loutfy H; Chen, Shijin

2018-06-19

The anticorrosion effect of thiazolyl blue (MTT) for copper in 3% NaCl at 298 K was researched by electrochemical methods, scanning electron-microscopy (SEM), and atomic force microscopy (AFM). The results reveal that MTT can protect copper efficiently, with a maximum efficiency of 95.7%. The corrosion inhibition mechanism was investigated by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectral (FT-IR), and theoretical calculation. The results suggest that the MTT molecules are adsorbed on metal surface forming a hydrophobic protective film to prevent copper corrosion. It also indicates that the MTT and copper form covalent bonds. The molecular dynamic simulation further gives the evidence for adsorption. The adsorption isotherm studies demonstrate that a spontaneous, mixed physical and chemical adsorption occurs, which obeys Langmuir adsorption isotherm. The present research can help us better understand the corrosion inhibition process and improve it.

Enhancement of porous silicon photoluminescence property by lithium chloride treatment

NASA Astrophysics Data System (ADS)

Azaiez, Khawla; Zaghouani, Rabia Benabderrahmane; Khamlich, Saleh; Meddeb, Hosny; Dimassi, Wissem

2018-05-01

Porous silicon (PS) decorated by several nanostructured metal elements has still aroused interests as promising composites in many industrial applications. With the focus mainly on the synthesis, the aspect of stability against optical irradiation of such materials has so far not been thoroughly addressed. This work focuses primarily on the influence of lithium chloride solution (LiCl) treatment on the physical properties of PS. Variations in the structural and optoelectronic properties of PS were observed after immersion in (LiCl), as revealed by the obtained analyses. Moreover, enhanced photoluminescence (PL) property of the PS after passivation by lithium particles was clearly shown, and their presence on the surface of the microporous silicon was confirmed by FTIR spectroscopy and atomic force microscopy. An improvement of the minority carrier lifetime was also obtained, which was attributed to the decrease of the surface recombination velocity after LiCl treatment.

The effect of gamma irradiation on chemical, morphology and optical properties of polystyrene nanosphere at various exposure time

NASA Astrophysics Data System (ADS)

Alhaji Yabagi, Jibrin; Isah Kimpa, Mohammed; Nmayaya Muhammad, Muhammad; Rashid, Saiful Bin; Zaidi, Embong; Arif Agam, Mohd

2018-01-01

Irradiation of polymers causes structural, chemical and the optical properties changes. Polystyrene nanosphere was drop coated to substrates and the gamma irradiation was carried out in a Cesium-137 (Cs-137) source chamber at different time (1-5 hours) with constant dose of 30 kGy. Fourier transformation infrared spectroscopy (FTIR) and Raman spectroscopy were employed to characterize the chemical properties of irradiated polystyrene while Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) were used to study the surface morphological changes of the samples. The optical energy band gaps of the thin films were investigated and studied using transmittance and absorbance measurements. The results obtained revealed that as irradiation time increases the optical properties changes and polystyrene gradually undergoes crystal to carbonaceous from its amorphous state. The average particles diameter and roughness of the samples decreases with increasing irradiation time.

Effects of the ultra-high pressure on structure and α-glucosidase inhibition of polysaccharide from Astragalus.

PubMed

Zhu, Zhen-Yuan; Luo, You; Dong, Guo-Ling; Ren, Yuan-Yuan; Chen, Li-Jing; Guo, Ming-Zhu; Wang, Xiao-Ting; Yang, Xue-Ying; Zhang, Yongmin

2016-06-01

A novel homogeneous polysaccharide fraction (APS) was extracted from Astragalus by hot water and purified by Sephadex G-100 and G-75 column. Its molecular weight was 693kDa. APS and APS with ultra-high pressure treatment exhibited significant inhibitory abilities on a-glucosidase, inhibition rate from high to low in order was 400MPa-APS, 300MPa-APS, 500MPa-APS and APS. The inhibition ​percentage of 400MPa-APS (1.5mg/mL) was 49% (max.). This suggested that the inhibitory activity of APS on a-glucosidase was improved by ultra-high pressure treatment. FT-IR, SEM, CD spectra, atomic force microscope and Congo red test analysis of APS and 400MPa-APS showed ultra-high pressure treatment didn't change the preliminary structure but had an effect on its advanced structure. Copyright © 2016 Elsevier B.V. All rights reserved.

Comprehensive characterization of chitosan/PEO/levan ternary blend films.

PubMed

Bostan, Muge Sennaroglu; Mutlu, Esra Cansever; Kazak, Hande; Sinan Keskin, S; Oner, Ebru Toksoy; Eroglu, Mehmet S

2014-02-15

Ternary blend films of chitosan, PEO (300,000) and levan were prepared by solution casting method and their phase behavior, miscibility, thermal and mechanical properties as well as their surface energy and morphology were characterized by different techniques. FT-IR analyses of blend films indicated intermolecular hydrogen bonding between blend components. Thermal and XRD analysis showed that chitosan and levan suppressed the crystallinity of PEO up to nearly 25% of PEO content in the blend, which resulted in more amorphous film structures at higher PEO/(chitosan+levan) ratios. At more than 30% of PEO concentration, contact angle (CA) measurements showed a surface enrichment of PEO whereas at lower PEO concentrations, chitosan and levan were enriched on the surfaces leading to more amorphous and homogenous surfaces. This result was further confirmed by atomic force microscopy (AFM) images. Cell proliferation and viability assay established the high biocompatibility of the blend films. Copyright © 2013 Elsevier Ltd. All rights reserved.

Removal of caffeine from industrial wastewater using Trichosporon asahii.

PubMed

Lakshmi, V; Das, Nilanjana

2013-07-01

Caffeine (1,3,7-trimethylxanthine), a natural alkaloid present mainly in tea and coffee products has been suggested as an environmental pollutant. Decaffeination is an important process for the removal of caffeine from coffee industrial wastes. In the present study, caffeine removal (through degradation) by yeast isolate, Trichosporon asahii immobilized on various conventional matrices (sodium alginate, carboxymethyl cellulose, chitosan, agar and agarose) was investigated using the method of entrapment. The biofilm forming ability of T. asahii was monitored by atomic force microscopy and scanning electron microscopy. Exopolysaccharide produced by T asahii biofilm was characterized by FT-IR spectroscopy and HPLC analysis. Caffeine removal from coffee processing industrial effluent was found to be 75 and 80 % by alginate immobilized yeast and yeast biofilm formed on gravels over a period of 48 hr in batch mode. Effectiveness of the process was also tested involving the continuous--flow column studies.

Microstructure-related properties of magnesium fluoride films at 193nm by oblique-angle deposition.

PubMed

Guo, Chun; Kong, Mingdong; Lin, Dawei; Liu, Cunding; Li, Bincheng

2013-01-14

Magnesium fluoride (MgF2) films deposited by resistive heating evaporation with oblique-angle deposition have been investigated in details. The optical and micro-structural properties of single-layer MgF2 films were characterized by UV-VIS and FTIR spectrophotometers, scanning electron microscope (SEM), atomic force microscope (AFM), and x-ray diffraction (XRD), respectively. The dependences of the optical and micro-structural parameters of the thin films on the deposition angle were analyzed. It was found that the MgF2 film in a columnar microstructure was negatively inhomogeneous of refractive index and polycrystalline. As the deposition angle increased, the optical loss, extinction coefficient, root-mean-square (rms) roughness, dislocation density and columnar angle of the MgF2 films increased, while the refractive index, packing density and grain size decreased. Furthermore, IR absorption of the MgF2 films depended on the columnar structured growth.

Effects of Solvent Diols on the Synthesis of ZnFe2O4 Particles and Their Use as Heterogeneous Photo-Fenton Catalysts

PubMed Central

Anchieta, Chayene Gonçalves; Cancelier, Adriano; Mazutti, Marcio Antonio; Jahn, Sérgio Luiz; Kuhn, Raquel Cristine; Gündel, Andre; Chiavone-Filho, Osvaldo; Foletto, Edson Luiz

2014-01-01

A solvothermal method was used to prepare zinc ferrite spinel oxide (ZnFe2O4) using ethylene glycol and 1,4 butanediol as solvent diols, and the influence of diols on the physical properties of ZnFe2O4 particles was investigated. The produced particles were characterized by X-ray powder diffraction (XRD), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR) and nitrogen adsorption isotherms, and the catalytic activity for the organic pollutant decomposition by heterogeneous photo-Fenton reaction was investigated. Both solvents produced particles with cubic spinel structure. Microporous and mesoporous structures were obtained when ethylene glycol and 1,4 butanediol were used as diols, respectively. A higher pore volume and surface area, as well as a higher catalytic activity for the pollutant degradation were found when 1,4 butanediol was used as solvent. PMID:28788191

Modification of polycarbonate surface in oxidizing plasma

NASA Astrophysics Data System (ADS)

Ovtsyn, A. A.; Smirnov, S. A.; Shikova, T. G.; Kholodkov, I. V.

2017-11-01

The properties of the surface of the film polycarbonate Lexan 8010 were experimentally studied after treatment in a DC discharge plasma in oxygen and air at pressures of 50-300 Pa and a discharge current of 80 mA. The contact angles of wetting and surface energies are measured. The topography of the surface was investigated by atomic force microscopy. The chemical composition of the surface was determined from the FT-IR spectroscopy data in the variant of total internal reflection, as well as X-ray photoelectron spectroscopy. Treatment in the oxidizing plasma leads to a change in morphology (average roughness increases), an increase in the surface energy, and the concentration of oxygen-containing groups (hydroxyl groups, carbonyl groups in ketones or aldehydes and in oxyketones) on the surface of the polymer. Possible reasons for the difference in surface properties of polymer under the action of oxygen and air plasma on it are discussed.

Influence of gamma irradiation on polymerization of pyrrole and glucose oxidase immobilization onto poly (pyrrole)/poly (vinyl alcohol) matrix

NASA Astrophysics Data System (ADS)

Idris, Sarada; A. Bakar, Ahmad Ashrif; Thevy Ratnam, Chantara; Kamaruddin, Nur Hasiba; Shaari, Sahbudin

2017-04-01

This paper describes the immobilization of glucose oxidase, GOx onto polymer matrix comprising of poly(pyrrole), PPy and poly(vinyl alcohol), PVA using gamma irradiation technique. Py/PVA-GOx film was prepared by spreading PVA:GOx, 1:1 solution onto dried pyrrole film and exposed to gamma irradiation from cobalt 60 source at doses ranging from 0 to 60 kGy. The films were subjected to structural and morphological analyses by using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Scanning electron microscope (SEM), Field emission scanning electron microscope (FESEM) and Atomic-force microscopy (AFM) techniques. Similar studies were also made on pristine pyrrole film which served as control. The SEM and FTIR spectra of Py/PVA-GOx film revealed that pyrrole has been successfully polymerized through irradiation-induced reactions. The results on the morphological properties of the samples characterize using FESEM, SEM and AFM further confirmed the occurrence of radiation-induced modification of Py/PVA-GOx film. The FTIR spectra showed the existence of intermolecular interaction between polymer matrix and GOx indicating that GOx had been successfully immobilized onto Ppy/PVA matrix by radiation-induced reactions. Results revealed that radiation induced reactions such as polymerization of pyrrole, crosslinking of PVA, grafting between the adjacent PVA and pyrrole molecules as well as immobilization of GOx onto Ppy/PVA matrix occurred simultaneously upon gamma irradiation. The optimum dose for GOx immobilization in the polymer matrix found to be 40 kGy. Therefore it is clear that this irradiation technique offered a simple single process to produce Py/PVA-GOx film without additional crosslinking and polymerization agents.

Structure and magnetic properties of SiO{sub 2}/PCL novel sol–gel organic–inorganic hybrid materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Catauro, Michelina, E-mail: michelina.catauro@unina2.it; Bollino, Flavia; Cristina Mozzati, Maria

2013-07-15

Organic–inorganic nanocomposite materials have been synthesized via sol–gel. They consist of an inorganic SiO{sub 2} matrix, in which different percentages of poly(ε-caprolactone) (PCL) have been incorporated. The formation of H-bonds among the carbonyl groups of the polymer chains and Si–OH group of the inorganic matrix has been proved by means of Fourier transform infrared spectroscopy (FT-IR) analysis and has been confirmed by solid-state nuclear magnetic resonance (NMR). X-Ray diffraction (XRD) analysis highlighted the amorphous nature of the synthesized materials. Scanning electron microscope (SEM) micrograph and atomic force microscope (AFM) topography showed their homogeneous morphology and nanostructure nature. Considering the opportunitymore » to synthesize these hybrid materials under microgravity conditions by means of magnetic levitation, superconducting quantum interference device (SQUID) magnetometry has been used to quantify their magnetic susceptibility. This measure has shown that the SiO{sub 2}/PCL hybrid materials are diamagnetic and that their diamagnetic susceptibility is independent of temperature and increases with the PCL amount. - Graphical abstract: Characterization and magnetic properties of SiO{sub 2}/PCL organic–inorganic hybrid materials synthesized via sol–gel. FT-IR, Fourier transform infrared spectroscopy; solid-state NMR: solid-state nuclear magnetic resonance; SQUID: superconducting quantum interference device. - Highlights: • Sol–gel synthesis of SiO{sub 2}/PCL amorphous class I organic–inorganic hybrid materials. • FT-IR and NMR analyses show the hydrogen bonds formation between SiO{sub 2} and PCL. • AFM and SEM analyses confirm that the SiO{sub 2}/PCL are homogenous hybrid materials. • The SQUID measures show that the simples are diamagnetic. • Diamagnetic susceptibility of SiO{sub 2}/PCL materials increases with the PCL amount.« less

A Comparison of Classical Force-Fields for Molecular Dynamics Simulations of Lubricants

PubMed Central

Ewen, James P.; Gattinoni, Chiara; Thakkar, Foram M.; Morgan, Neal; Spikes, Hugh A.; Dini, Daniele

2016-01-01

For the successful development and application of lubricants, a full understanding of their complex nanoscale behavior under a wide range of external conditions is required, but this is difficult to obtain experimentally. Nonequilibrium molecular dynamics (NEMD) simulations can be used to yield unique insights into the atomic-scale structure and friction of lubricants and additives; however, the accuracy of the results depend on the chosen force-field. In this study, we demonstrate that the use of an accurate, all-atom force-field is critical in order to; (i) accurately predict important properties of long-chain, linear molecules; and (ii) reproduce experimental friction behavior of multi-component tribological systems. In particular, we focus on n-hexadecane, an important model lubricant with a wide range of industrial applications. Moreover, simulating conditions common in tribological systems, i.e., high temperatures and pressures (HTHP), allows the limits of the selected force-fields to be tested. In the first section, a large number of united-atom and all-atom force-fields are benchmarked in terms of their density and viscosity prediction accuracy of n-hexadecane using equilibrium molecular dynamics (EMD) simulations at ambient and HTHP conditions. Whilst united-atom force-fields accurately reproduce experimental density, the viscosity is significantly under-predicted compared to all-atom force-fields and experiments. Moreover, some all-atom force-fields yield elevated melting points, leading to significant overestimation of both the density and viscosity. In the second section, the most accurate united-atom and all-atom force-field are compared in confined NEMD simulations which probe the structure and friction of stearic acid adsorbed on iron oxide and separated by a thin layer of n-hexadecane. The united-atom force-field provides an accurate representation of the structure of the confined stearic acid film; however, friction coefficients are consistently under-predicted and the friction-coverage and friction-velocity behavior deviates from that observed using all-atom force-fields and experimentally. This has important implications regarding force-field selection for NEMD simulations of systems containing long-chain, linear molecules; specifically, it is recommended that accurate all-atom potentials, such as L-OPLS-AA, are employed. PMID:28773773

A Comparison of Classical Force-Fields for Molecular Dynamics Simulations of Lubricants.

PubMed

Ewen, James P; Gattinoni, Chiara; Thakkar, Foram M; Morgan, Neal; Spikes, Hugh A; Dini, Daniele

2016-08-02

For the successful development and application of lubricants, a full understanding of their complex nanoscale behavior under a wide range of external conditions is required, but this is difficult to obtain experimentally. Nonequilibrium molecular dynamics (NEMD) simulations can be used to yield unique insights into the atomic-scale structure and friction of lubricants and additives; however, the accuracy of the results depend on the chosen force-field. In this study, we demonstrate that the use of an accurate, all-atom force-field is critical in order to; (i) accurately predict important properties of long-chain, linear molecules; and (ii) reproduce experimental friction behavior of multi-component tribological systems. In particular, we focus on n -hexadecane, an important model lubricant with a wide range of industrial applications. Moreover, simulating conditions common in tribological systems, i.e., high temperatures and pressures (HTHP), allows the limits of the selected force-fields to be tested. In the first section, a large number of united-atom and all-atom force-fields are benchmarked in terms of their density and viscosity prediction accuracy of n -hexadecane using equilibrium molecular dynamics (EMD) simulations at ambient and HTHP conditions. Whilst united-atom force-fields accurately reproduce experimental density, the viscosity is significantly under-predicted compared to all-atom force-fields and experiments. Moreover, some all-atom force-fields yield elevated melting points, leading to significant overestimation of both the density and viscosity. In the second section, the most accurate united-atom and all-atom force-field are compared in confined NEMD simulations which probe the structure and friction of stearic acid adsorbed on iron oxide and separated by a thin layer of n -hexadecane. The united-atom force-field provides an accurate representation of the structure of the confined stearic acid film; however, friction coefficients are consistently under-predicted and the friction-coverage and friction-velocity behavior deviates from that observed using all-atom force-fields and experimentally. This has important implications regarding force-field selection for NEMD simulations of systems containing long-chain, linear molecules; specifically, it is recommended that accurate all-atom potentials, such as L-OPLS-AA, are employed.

Crystalline TiO 2 grafted with poly(2-methacryloyloxyethyl phosphorylcholine) via surface-initiated atom-transfer radical polymerization

NASA Astrophysics Data System (ADS)

Zhao, Yuancong; Tu, Qiufen; Wang, Jin; Huang, Qiongjian; Huang, Nan

2010-12-01

Crystalline TiO 2 films were prepared by unbalanced magnetron sputtering and the structure was confirmed by XRD. An organic layer of 11-hydroxyundecylphosphonic acid (HUPA) was prepared on the TiO 2 films by self-assembling, and the HUPA on TiO 2 films was confirmed by FTIR analysis. Simultaneously, hydroxyl groups were introduced in the phosphonic acid molecules to provide a functionality for further chemical modification. 2-Methacryloyloxyethyl phosphorylcholine (MPC), a biomimetic monomer, was chemically grafted on the HUPA surfaces at room temperature by surface-initiated atom-transfer radical polymerization. The surface characters of TiO 2 films modified by poly-MPC were confirmed by FTIR, XPS and SEM analysis. Platelet adhesion experiment revealed that poly-MPC modified surface was effective to inhibit platelet adhesion in vitro.

Spectroscopic Study of the Thermal Degradation of PVP-capped Rh and Pt Nanoparticles in H2 and O2 Environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borodko, Yuri; Lee, Hyun Sook; Joo, Sang Hoon

2009-09-15

Poly(N-vinylpyrrolidone) (PVP) capped platinum and rhodium nanoparticles (7-12 nm) have been studied with UV-VIS, FTIR and Raman spectroscopy. The absorption bands in the region 190-900 nm are shown to be sensitive to the electronic structure of surface Rh and Pt atoms as well as to the aggregation of the nanoparticles. In-situ FTIR-DRIFT spectroscopy of the thermal decay of PVP stabilized Rh and Pt nanoparticles in H{sub 2} and O{sub 2} atmospheres in temperatures ranging from 30 C-350 C reveal that decomposition of PVP above 200 C, PVP transforms into a 'polyamidpolyene' - like material that is in turn converted intomore » a thin layer of amorphous carbon above 300 C. Adsorbed carbon monoxide was used as a probing molecule to monitor changes of electronic structure of surface Rh and Pt atoms and accessible surface area. The behavior of surface Rh and Pt atoms with ligated CO and amide groups of pyrrolidones resemble that of surface coordination compounds.« less

Subatomic Features on the Silicon (111)-(7x7) Surface Observed by Atomic Force Microscopy.

PubMed

Giessibl; Hembacher; Bielefeldt; Mannhart

2000-07-21

The atomic force microscope images surfaces by sensing the forces between a sharp tip and a sample. If the tip-sample interaction is dominated by short-range forces due to the formation of covalent bonds, the image of an individual atom should reflect the angular symmetry of the interaction. Here, we report on a distinct substructure in the images of individual adatoms on silicon (111)-(7x7), two crescents with a spherical envelope. The crescents are interpreted as images of two atomic orbitals of the front atom of the tip. Key for the observation of these subatomic features is a force-detection scheme with superior noise performance and enhanced sensitivity to short-range forces.

Photoacid generator study for chemically amplified negative resists for high-resolution lithography

NASA Astrophysics Data System (ADS)

Dentinger, Paul M.; Knapp, Kurtis G.; Reynolds, Geoffrey W.; Taylor, James W.; Fedynyshyn, Theodore H.; Richardson, Todd A.

1998-06-01

The effect of photoacid generator and photogenerated acid molecular structures on a negative-tone chemically-amplified resist was tested using two different sets of acid generators, each set with one formulation creating a 'volatile' acid, and the other formulation creating a 'non- volatile' acid when exposed to x-rays. The acids from one set were generated from a derivative of iodonium salt and the acids from the other set were generated from a covalently bound photoacid generator. Both sets were compared to Shipley SAL 605 resist. In this study of five formulations, normalized remaining thickness (NRT) curves, SEM images of printed lines, spectrophotometric titration of the photogenerated acid, real-time curves, SEM images of printed lines, spectrophotometric titration of the photogenerated acid, real-time FTIR for kinetics of the PEB reaction, dissolution rate measurements, and atomic force microscopy for surface roughness were employed. RT-FTIR suggested that both the proposed 'volatile' and 'non- volatile' acids were retained to approximately the same extent within the films cast from these formulations. A mechanism is suggested where the type of photogenerated acid has an effect on the kinetics of the reaction and the photogenerated acid or photoacid effect on the kinetics of the reaction and the photogenerated acid or photoacid generator has a large effect on the ability of the aqueous developer to penetrate or dissolve the film.

Quantum mechanical study and spectroscopic (FT-IR, FT-Raman, 13C, 1H) study, first order hyperpolarizability, NBO analysis, HOMO and LUMO analysis of 2-acetoxybenzoic acid by density functional methods

NASA Astrophysics Data System (ADS)

Bhavani, K.; Renuga, S.; Muthu, S.; Sankara narayanan, K.

2015-02-01

In this work, colorless crystals of 2-acetoxybenzoic acid were grown by slow evaporation method and the FT-IR and FT-Raman spectra of the sample were recorded in the region 4000-500 cm-1 and 4000-100 cm-1 respectively. Molecular structure is optimized with the help of density functional theory method (B3LYP) with 6-31+G(d,p), 6-311++G(d,p) basis sets. Stability of the molecule arising from hyperconjugation and charge delocalization is confirmed by the natural bond orbital analysis (NBO). The results show that electron density (ED) in the σ∗ antibonding orbitals and E(2) energies confirms the occurrence of intramolecular charge transfer (ICT) within the molecule. The assignments of the vibrational spectra have been carried out with the help of normal coordinate analysis following the scaled quantum mechanical force field (SQMFF) methodology. The results of the calculations were applied to simulated spectra of the title compound, which show excellent agreement with observed spectra. The 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by GIAO method. Mulliken population analysis on atomic charges is also calculated. The calculated HOMO and LUMO energy gap shows that charge transfer occurs within the molecule.

Osteoconductive Potential of Barrier NanoSiO2 PLGA Membranes Functionalized by Plasma Enhanced Chemical Vapour Deposition

PubMed Central

Terriza, Antonia; Vilches-Pérez, Jose I.; de la Orden, Emilio; Yubero, Francisco; Gonzalez-Caballero, Juan L.; González-Elipe, Agustin R.; Vilches, José; Salido, Mercedes

2014-01-01

The possibility of tailoring membrane surfaces with osteoconductive potential, in particular in biodegradable devices, to create modified biomaterials that stimulate osteoblast response should make them more suitable for clinical use, hopefully enhancing bone regeneration. Bioactive inorganic materials, such as silica, have been suggested to improve the bioactivity of synthetic biopolymers. An in vitro study on HOB human osteoblasts was performed to assess biocompatibility and bioactivity of SiO2 functionalized poly(lactide-co-glycolide) (PLGA) membranes, prior to clinical use. A 15 nm SiO2 layer was deposited by plasma enhanced chemical vapour deposition (PECVD), onto a resorbable PLGA membrane. Samples were characterized by X-ray photoelectron spectroscopy, atomic force microscopy, scanning electron microscopy, and infrared spectroscopy (FT-IR). HOB cells were seeded on sterilized test surfaces where cell morphology, spreading, actin cytoskeletal organization, and focal adhesion expression were assessed. As proved by the FT-IR analysis of samples, the deposition by PECVD of the SiO2 onto the PLGA membrane did not alter the composition and other characteristics of the organic membrane. A temporal and spatial reorganization of cytoskeleton and focal adhesions and morphological changes in response to SiO2 nanolayer were identified in our model. The novedous SiO2 deposition method is compatible with the standard sterilization protocols and reveals as a valuable tool to increase bioactivity of resorbable PLGA membranes. PMID:24883304

Effect of silver ion-induced disorder on morphological, chemical and optical properties of poly (methyl methacrylate)

NASA Astrophysics Data System (ADS)

Arif, Shafaq; Saleemi, Farhat; Rafique, M. Shahid; Naab, Fabian; Toader, Ovidiu; Mahmood, Arshad; Aziz, Uzma

2016-11-01

Ion implantation is a versatile technique to tailor the surface properties of polymers in a controlled manner. In the present study, samples of poly (methyl methacrylate) (PMMA) have been implanted with 400 keV silver (Ag+) ion beam to various ion fluences ranging from 5 × 1013 to 5 × 1015 ions/cm2. The effect of Ag+ ion-induced disorder on morphological, chemical and optical properties of PMMA is analyzed using Atomic Force Microscope (AFM), Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible (UV-Vis) spectroscopy. Furthermore, the electrical conductivity of pristine and implanted PMMA is measured using four probe apparatus. The AFM images revealed the growth of nano-sized grainy structures and hillocks above the surface of implanted PMMA. The FTIR spectra confirmed the modifications in chemical structure of PMMA along with the formation of sbnd Cdbnd Csbnd carbon contents. The refractive index, extinction coefficient and photoconductivity of implanted PMMA have been found to increase as a function of ion fluence. Simultaneously, indirect optical band gap is reduced from 3.13 to 0.81 eV at a relatively high fluence (5 × 1015 ions/cm2). A linear correlation has been established between the band gap and Urbach energies. Moreover, the electrical conductivity of Ag+ implanted PMMA has increased from 2.14 × 10-10 (pristine) to 9.6 × 10-6 S/cm.

Molecular structure, vibrational, electronic and thermal properties of 4-vinylcyclohexene by quantum chemical calculations

NASA Astrophysics Data System (ADS)

Nagabalasubramanian, P. B.; Periandy, S.; Karabacak, Mehmet; Govindarajan, M.

2015-06-01

The solid phase FT-IR and FT-Raman spectra of 4-vinylcyclohexene (abbreviated as 4-VCH) have been recorded in the region 4000-100 cm-1. The optimized molecular geometry and vibrational frequencies of the fundamental modes of 4-VCH have been precisely assigned and analyzed with the aid of structure optimizations and normal coordinate force field calculations based on density functional theory (DFT) method at 6-311++G(d,p) level basis set. The theoretical frequencies were properly scaled and compared with experimentally obtained FT-IR and FT-Raman spectra. Also, the effect due the substitution of vinyl group on the ring vibrational frequencies was analyzed and a detailed interpretation of the vibrational spectra of this compound has been made on the basis of the calculated total energy distribution (TED). The time dependent DFT (TD-DFT) method was employed to predict its electronic properties, such as electronic transitions by UV-Visible analysis, HOMO and LUMO energies, molecular electrostatic potential (MEP) and various global reactivity and selectivity descriptors (chemical hardness, chemical potential, softness, electrophilicity index). Stability of the molecule arising from hyper conjugative interaction, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. Atomic charges obtained by Mulliken population analysis and NBO analysis are compared. Thermodynamic properties (heat capacity, entropy and enthalpy) of the title compound at different temperatures are also calculated.

Galleria mellonella apolipophorin III - an apolipoprotein with anti-Legionella pneumophila activity.

PubMed

Zdybicka-Barabas, Agnieszka; Palusińska-Szysz, Marta; Gruszecki, Wiesław I; Mak, Paweł; Cytryńska, Małgorzata

2014-10-01

The greater wax moth Galleria mellonella has been exploited worldwide as an alternative model host for studying pathogenicity and virulence factors of different pathogens, including Legionella pneumophila, a causative agent of a severe form of pneumonia called Legionnaires' disease. An important role in the insect immune response against invading pathogens is played by apolipophorin III (apoLp-III), a lipid- and pathogen associated molecular pattern-binding protein able to inhibit growth of some Gram-negative bacteria, including Legionella dumoffii. In the present study, anti-L. pneumophila activity of G. mellonella apoLp-III and the effects of the interaction of this protein with L. pneumophila cells are demonstrated. Alterations in the bacteria cell surface occurring upon apoLp-III treatment, revealed by Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy, are also documented. ApoLp-III interactions with purified L. pneumophila LPS, an essential virulence factor of the bacteria, were analysed using electrophoresis and immunoblotting with anti-apoLp-III antibodies. Moreover, FTIR spectroscopy was used to gain detailed information on the type of conformational changes in L. pneumophila LPS and G. mellonella apoLp-III induced by their mutual interactions. The results indicate that apoLp-III binding to components of bacterial cell envelope, including LPS, may be responsible for anti-L. pneumophila activity of G. mellonella apoLp-III. Copyright © 2014 Elsevier B.V. All rights reserved.

Green synthesis of nano sized transition metal complexes containing heterocyclic Schiff base: Structural and morphology characterization and bioactivity study

NASA Astrophysics Data System (ADS)

Jawoor, Shailaja S.; Patil, Sangamesh A.; Kumbar, Mahantesh; Ramawadgi, Prashant B.

2018-07-01

In the current involvement of our research work in coordination chemistry, novel transition metal complexes were synthesized from regular reflux method and hydrothermal method using Schiff base prepared via condensation of ethyl 2-amino-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylate with 8-carbaldehyde-7-hydroxy-4-methylcoumarin. All the synthesized compounds were interpreted using different analytical, physicochemical and spectral methods such as magnetic moment measurement, FT-IR, 1H and 13C NMR, GCMS/ESI-MS, UV/Vis spectroscopy and TGA. The size and morphology of the nano metal complexes were determined using atomic force microscope (AFM), field emission scanning electron spectroscopy (FE-SEM) and X-ray powder diffraction (PXRD). The non-electrolytic nature of the metal complexes was confirmed by molar conductance studies. The obtained FT-IR data supports the binding of metal ion to Schiff base. Elemental analysis study suggests [ML2(H2O)2] stoichiometry, here M = Co(II), Ni(II) and Cu(II), L = deprotonated ligand. Electronic spectral results reveal six-coordinated geometry for the synthesized metal complexes. All the tested compounds show good DNA cleavage (Calf Thymus DNA) and in vitro anticancer activity (PA-I cell line), the activity results for the tested compounds are prominent and compound 9 exhibited a little enhanced activity than the other tested compounds.

Dielectrophoretic immobilization of proteins: Quantification by atomic force microscopy.

PubMed

Laux, Eva-Maria; Knigge, Xenia; Bier, Frank F; Wenger, Christian; Hölzel, Ralph

2015-09-01

The combination of alternating electric fields with nanometer-sized electrodes allows the permanent immobilization of proteins by dielectrophoretic force. Here, atomic force microscopy is introduced as a quantification method, and results are compared with fluorescence microscopy. Experimental parameters, for example the applied voltage and duration of field application, are varied systematically, and the influence on the amount of immobilized proteins is investigated. A linear correlation to the duration of field application was found by atomic force microscopy, and both microscopical methods yield a square dependence of the amount of immobilized proteins on the applied voltage. While fluorescence microscopy allows real-time imaging, atomic force microscopy reveals immobilized proteins obscured in fluorescence images due to low S/N. Furthermore, the higher spatial resolution of the atomic force microscope enables the visualization of the protein distribution on single nanoelectrodes. The electric field distribution is calculated and compared to experimental results with very good agreement to atomic force microscopy measurements. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermal Casimir-Polder forces on a V-type three-level atom

NASA Astrophysics Data System (ADS)

Xu, Chen-Ran; Xu, Jing-Ping; Al-amri, M.; Zhu, Cheng-Jie; Xie, Shuang-Yuan; Yang, Ya-Ping

2017-09-01

We study the thermal Casimir-Polder (CP) forces on a V-type three-level atom. The competition between the thermal effect and the quantum interference of the two transition dipoles on the force is investigated. To shed light onto the role of the quantum interference, we analyze two kinds of initial states of the atom, i.e., the superradiant state and the subradiant state. Considering the atom being in the thermal reservoir, the resonant CP force arising from the real photon emission dominates in the evolution of the CP force. Under the zero-temperature condition, the quantum interference can effectively modify the amplitude and the evolution of the force, leading to a long-time force or even the cancellation of the force. Our results reveal that in the finite-temperature case, the thermal photons can enhance the amplitude of all force elements, but have no influence on the net resonant CP force in the steady state, which means that the second law of thermodynamics still works. For the ideal degenerate V-type atom with parallel dipoles under the initial subradiant state, the robust destructive quantum interference overrides the thermal fluctuations, leading to the trapping of the atom in the subradiant state and the disappearance of the CP force. However, in terms of a realistic Zeeman atom, the thermal photons play a significant role during the evolution of the CP force. The thermal fluctuations can enhance the amplitude of the initial CP force by increasing the temperature, and weaken the influence of the quantum interference on the evolution of the CP force from the initial superradiant (subradiant) state to the steady state.

Automation of the CHARMM General Force Field (CGenFF) I: bond perception and atom typing

PubMed Central

Vanommeslaeghe, K.; MacKerell, A. D.

2012-01-01

Molecular mechanics force fields are widely used in computer-aided drug design for the study of drug-like molecules alone or interacting with biological systems. In simulations involving biological macromolecules, the biological part is typically represented by a specialized biomolecular force field, while the drug is represented by a matching general (organic) force field. In order to apply these general force fields to an arbitrary drug-like molecule, functionality for assignment of atom types, parameters and charges is required. In the present article, which is part I of a series of two, we present the algorithms for bond perception and atom typing for the CHARMM General Force Field (CGenFF). The CGenFF atom typer first associates attributes to the atoms and bonds in a molecule, such as valence, bond order, and ring membership among others. Of note are a number of features that are specifically required for CGenFF. This information is then used by the atom typing routine to assign CGenFF atom types based on a programmable decision tree. This allows for straightforward implementation of CGenFF’s complicated atom typing rules and for equally straightforward updating of the atom typing scheme as the force field grows. The presented atom typer was validated by assigning correct atom types on 477 model compounds including in the training set as well as 126 test-set molecules that were constructed to specifically verify its different components. The program may be utilized via an online implementation at https://www.paramchem.org/. PMID:23146088

Automation of the CHARMM General Force Field (CGenFF) I: bond perception and atom typing.

PubMed

Vanommeslaeghe, K; MacKerell, A D

2012-12-21

Molecular mechanics force fields are widely used in computer-aided drug design for the study of drug-like molecules alone or interacting with biological systems. In simulations involving biological macromolecules, the biological part is typically represented by a specialized biomolecular force field, while the drug is represented by a matching general (organic) force field. In order to apply these general force fields to an arbitrary drug-like molecule, functionality for assignment of atom types, parameters, and charges is required. In the present article, which is part I of a series of two, we present the algorithms for bond perception and atom typing for the CHARMM General Force Field (CGenFF). The CGenFF atom typer first associates attributes to the atoms and bonds in a molecule, such as valence, bond order, and ring membership among others. Of note are a number of features that are specifically required for CGenFF. This information is then used by the atom typing routine to assign CGenFF atom types based on a programmable decision tree. This allows for straightforward implementation of CGenFF's complicated atom typing rules and for equally straightforward updating of the atom typing scheme as the force field grows. The presented atom typer was validated by assigning correct atom types on 477 model compounds including in the training set as well as 126 test-set molecules that were constructed to specifically verify its different components. The program may be utilized via an online implementation at https://www.paramchem.org/ .

Photocatalytic C60-amorphous TiO2 composites prepared by atomic layer deposition

NASA Astrophysics Data System (ADS)

Justh, Nóra; Firkala, Tamás; László, Krisztina; Lábár, János; Szilágyi, Imre Miklós

2017-10-01

Nanocomposites of TiO2 and single fullerene (C60) molecule are prepared by atomic layer deposition (ALD). To create nucleation sites for the ALD reaction, the bare fullerene is functionalized by H2SO4/HNO3 treatment, which results in C60-SO3H. After a NaOH washing step the intermediate hydrolyzes into C60sbnd OH. This process and the consecutive ALD growth of TiO2 are monitored with FTIR, TG/DTA-MS, EDX, Raman, FTIR, XRD, and TEM measurements. Although the TiO2 grown by ALD at 80 and 160 °C onto fullerol is amorphous it enhances the decomposition of methyl orange under UV exposure. This study proves that amorphous TiO2 grown by low temperature ALD has photocatalytic activity, and it can be used e.g. as self-cleaning coatings also on heat sensitive substrates.

Red/blue shifting hydrogen bonds in acetonitrile-dimethyl sulphoxide solutions: FTIR and theoretical studies

NASA Astrophysics Data System (ADS)

Kannan, P. P.; Karthick, N. K.; Mahendraprabu, A.; Shanmugam, R.; Elangovan, A.; Arivazhagan, G.

2017-07-01

FTIR spectra of neat acetonitrile (AN), dimethyl sulphoxide (DMSO) and their binary solutions at various mole fractions have been recorded at room temperature. Theoretical calculations have also been carried out on acetonitrile (monomer, dimer), dimethyl sulphoxide (monomer, dimer) and AN - DMSO complex molecules. 1:2 (AN:DMSO) and 2:1 complexation through the red shifting (AN) C - H ⋯ O = S(DMSO) and blue shifting (DMSO) C - H ⋯ N ≡ C(AN) hydrogen bonds has been identified. The experimental and theoretical studies favour the presence of both the monomer and dimer in liquid AN, but only closed dimers in DMSO. The dipole-dipole interactions existed in AN and DMSO dimers disappear in the complex molecules. Partial π bond between S and O atoms, and three lone pair of electrons on oxygen atom of DMSO have been noticed theoretically.

Low-Temperature Reduction of Graphene Oxide: Electrical Conductance and Scanning Kelvin Probe Force Microscopy

NASA Astrophysics Data System (ADS)

Slobodian, Oleksandr M.; Lytvyn, Peter M.; Nikolenko, Andrii S.; Naseka, Victor M.; Khyzhun, Oleg Yu.; Vasin, Andrey V.; Sevostianov, Stanislav V.; Nazarov, Alexei N.

2018-05-01

Graphene oxide (GO) films were formed by drop-casting method and were studied by FTIR spectroscopy, micro-Raman spectroscopy (mRS), X-ray photoelectron spectroscopy (XPS), four-points probe method, atomic force microscopy (AFM), and scanning Kelvin probe force (SKPFM) microscopy after low-temperature annealing at ambient conditions. It was shown that in temperature range from 50 to 250 °C the electrical resistivity of the GO films decreases by seven orders of magnitude and is governed by two processes with activation energies of 6.22 and 1.65 eV, respectively. It was shown that the first process is mainly associated with water and OH groups desorption reducing the thickness of the film by 35% and causing the resistivity decrease by five orders of magnitude. The corresponding activation energy is the effective value determined by desorption and electrical connection of GO flakes from different layers. The second process is mainly associated with desorption of oxygen epoxy and alkoxy groups connected with carbon located in the basal plane of GO. AFM and SKPFM methods showed that during the second process, first, the surface of GO plane is destroyed forming nanostructured surface with low work function and then at higher temperature a flat carbon plane is formed that results in an increase of the work function of reduced GO.

Acid-Base Interactions of Polystyrene Sulfonic Acid in Amorphous Solid Dispersions Using a Combined UV/FTIR/XPS/ssNMR Study.

PubMed

Song, Yang; Zemlyanov, Dmitry; Chen, Xin; Nie, Haichen; Su, Ziyang; Fang, Ke; Yang, Xinghao; Smith, Daniel; Byrn, Stephen; Lubach, Joseph W

2016-02-01

This study investigates the potential drug-excipient interactions of polystyrene sulfonic acid (PSSA) and two weakly basic anticancer drugs, lapatinib (LB) and gefitinib (GB), in amorphous solid dispersions. Based on the strong acidity of the sulfonic acid functional group, PSSA was hypothesized to exhibit specific intermolecular acid-base interactions with both model basic drugs. Ultraviolet (UV) spectroscopy identified red shifts, which correlated well with the color change observed in lapatinib-PSSA solutions. Fourier transform infrared (FTIR) spectra suggest the protonation of the quinazoline nitrogen atom in both model compounds, which agrees well with data from the crystalline ditosylate salt of lapatinib. X-ray photoelectron spectroscopy (XPS) detected increases in binding energy of the basic nitrogen atoms in both lapatinib and gefitinib, strongly indicating protonation of these nitrogen atoms. (15)N solid-state NMR spectroscopy provided direct spectroscopic evidence for protonation of the quinazoline nitrogen atoms in both LB and GB, as well as the secondary amine nitrogen atom in LB and the tertiary amine nitrogen atom in GB. The observed chemical shifts in the LB-PSSA (15)N spectrum also agree very well with the lapatinib ditosylate salt where proton transfer is known. Additionally, the dissolution and physical stability behaviors of both amorphous solid dispersions were examined. PSSA was found to significantly improve the dissolution of LB and GB and effectively inhibit the crystallization of LB and GB under accelerated storage conditions due to the beneficial strong intermolecular acid-base interaction between the sulfonic acid groups and basic nitrogen centers.

Structural studies of lead lithium borate glasses doped with silver oxide.

PubMed

Coelho, João; Freire, Cristina; Hussain, N Sooraj

2012-02-01

Silver oxide doped lead lithium borate (LLB) glasses have been prepared and characterized. Structural and composition characterization were accessed by XRD, FTIR, Raman, SEM and EDS. Results from FTIR and Raman spectra indicate that Ag(2)O acts as a network modifier even at small quantities by converting three coordinated to four coordinated boron atoms. Other physical properties, such as density, molar volume and optical basicity are also evaluated. Furthermore, they are also affected by the silver oxide composition. Copyright © 2011 Elsevier B.V. All rights reserved.

Biosynthesis of zinc oxide nanoparticles using leaf extract of Calotropis gigantea: characterization and its evaluation on tree seedling growth in nursery stage

NASA Astrophysics Data System (ADS)

Chaudhuri, Sadhan Kumar; Malodia, Lalit

2017-11-01

Green synthesis of zinc oxide nanoparticles was carried out using Calotropis leaf extract with zinc acetate salt in the presence of 2 M NaOH. The combination of 200 mM zinc acetate salt and 15 ml of leaf extract was ideal for the synthesis of less than 20 nm size of highly monodisperse crystalline nanoparticles. Synthesized nanoparticles were characterized through UV-Vis spectroscopy, dynamic light scattering (DLS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), EDX (energy dispersive X-ray), and AFM (atomic force microscopy). Effects of biogenic zinc oxide (ZnO) nanoparticles on growth and development of tree seedlings in nursery stage were studied in open-air trenches. The UV-Vis absorption maxima showed peak near 350 nm, which is characteristic of ZnO nanoparticles. DLS data showed that single peak is at 11 nm (100%) and Polydispersity Index is 0.245. XRD analysis showed that these are highly crystalline ZnO nanoparticles having an average size of 10 nm. FTIR spectra were recorded to identify the biomolecules involved in the synthesis process, which showed absorption bands at 4307, 3390, 2825, 871, 439, and 420 cm-1. SEM images showed that the particles were spherical in nature. The presence of zinc and oxygen was confirmed by EDX and the atomic % of zinc and oxygen were 33.31 and 68.69, respectively. 2D and 3D images of ZnO nanoparticles were obtained by AFM studies, which indicated that these are monodisperse having size ranges between 1.5 and 8.5 nm. Significant enhancement of growth was observed in Neem ( Azadirachta indica), Karanj ( Pongamia pinnata), and Milkwood-pine ( Alstonia scholaris) seedlings in foliar spraying ZnO nanoparticles to nursery stage of tree seedlings. Out of the three treated saplings, Alstonia scholaris showed maximum height development.

Spontaneous lateral atomic recoil force close to a photonic topological material

NASA Astrophysics Data System (ADS)

Hassani Gangaraj, S. Ali; Hanson, George W.; Antezza, Mauro; Silveirinha, Mário G.

2018-05-01

We investigate the quantum recoil force acting on an excited atom close to the surface of a nonreciprocal photonic topological insulator (PTI). The main atomic emission channel is the unidirectional surface plasmon propagating at the PTI-vacuum interface, and we show that it enables a spontaneous lateral recoil force that scales at short distances as 1 /d4 , where d is the atom-PTI separation. Remarkably, the sign of the recoil force is polarization and orientation independent, and it occurs in a translation-invariant homogeneous system in thermal equilibrium. Surprisingly, the recoil force persists for very small values of the gyration pseudovector, which, for a biased plasma, corresponds to very low cyclotron frequencies. The ultrastrong recoil force is rooted in the quasihyperbolic dispersion of the surface plasmons. We consider both an initially excited atom and a continuous pump scenario, the latter giving rise to a steady lateral force whose direction can be changed at will by simply varying the orientation of the biasing magnetic field. Our predictions may be tested in experiments with cold Rydberg atoms and superconducting qubits.

Quantitative force measurements using frequency modulation atomic force microscopy—theoretical foundations

NASA Astrophysics Data System (ADS)

Sader, John E.; Uchihashi, Takayuki; Higgins, Michael J.; Farrell, Alan; Nakayama, Yoshikazu; Jarvis, Suzanne P.

2005-03-01

Use of the atomic force microscope (AFM) in quantitative force measurements inherently requires a theoretical framework enabling conversion of the observed deflection properties of the cantilever to an interaction force. In this paper, the theoretical foundations of using frequency modulation atomic force microscopy (FM-AFM) in quantitative force measurements are examined and rigorously elucidated, with consideration being given to both 'conservative' and 'dissipative' interactions. This includes a detailed discussion of the underlying assumptions involved in such quantitative force measurements, the presentation of globally valid explicit formulae for evaluation of so-called 'conservative' and 'dissipative' forces, discussion of the origin of these forces, and analysis of the applicability of FM-AFM to quantitative force measurements in liquid.

Structural analysis of the industrial grade calcite

NASA Astrophysics Data System (ADS)

Shah, Rajiv P.; Raval, Kamlesh G.

2017-05-01

The chemical, optical and structural characterization of the industrial grade Calcite by EDAX, FT-IR and XRD. EDAX is a widely used technique to analyze the chemical components in a material, FT-IR stands for Fourier Transform Infra-Red, the preferred method of infrared spectroscopy. The resultant spectrum represents the molecular absorption and transmission, creating a molecular fingerprint of the sample, The atomic planes of a crystal cause an incident beam of X-rays to interfere with one another as they leave the crystal. The phenomenon is called X ray diffraction.(XRD). Data analysis of EDAX, FT-IR and XRD has been carried out with help of various instruments and software and find out the results of the these industrial grade materials which are mostly used in ceramics industries

AtomicJ: An open source software for analysis of force curves

NASA Astrophysics Data System (ADS)

Hermanowicz, Paweł; Sarna, Michał; Burda, Kvetoslava; Gabryś, Halina

2014-06-01

We present an open source Java application for analysis of force curves and images recorded with the Atomic Force Microscope. AtomicJ supports a wide range of contact mechanics models and implements procedures that reduce the influence of deviations from the contact model. It generates maps of mechanical properties, including maps of Young's modulus, adhesion force, and sample height. It can also calculate stacks, which reveal how sample's response to deformation changes with indentation depth. AtomicJ analyzes force curves concurrently on multiple threads, which allows for high speed of analysis. It runs on all popular operating systems, including Windows, Linux, and Macintosh.

Surface Chemistry and Interface Evolution during the Atomic Layer Deposition of High-k Metal Oxides on InAs(100) and GaAs(100) Surfaces

NASA Astrophysics Data System (ADS)

Henegar, Alex J.

Device scaling has been key for creating faster and more powerful electronic devices. Integral circuit components like the metal-oxide semiconductor field-effect transistor (MOSFET) now rely on material deposition techniques, like atomic layer deposition (ALD), that possess atomic-scale thickness precision. At the heart of the archetypal MOSFET is a SiO2/Si interface which can be formed to near perfection. However when the thickness of the SiO 2 layer is shrunk down to a few nanometers several complications arise like unacceptably high leakage current and power consumption. Replacing Si with III-V semiconductors and SiO2 with high-k dielectric materials is appealing but comes with its own set of challenges. While SiO2 is practically defect-free, the native oxides of III-Vs are poor dielectrics. In this dissertation, the surface chemistry and interface evolution during the ALD of high-k metal oxides on Si(100), GaAs(100) and InAs(100) was studied. In particular, the surface chemistry and crystallization of TiO2 films grown on Si(100) was investigated using transmission Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Large, stable, and highly reactive anatase TiO2 grains were found to form during a post-deposition heat treatment after the ALD at 100 °C. The remainder of this work was focused on the evolution of the interfacial oxides during the deposition of TiO2 and Al2O3 on InAs(100) and GaAs(100) and during the deposition of Ta2O 5 on InAs(100). In summary the ALD precursor type, deposited film, and substrate had an influence in the evolution of the native oxides. Alkyl amine precursors fared better at removing the native oxides but the deposited films (TiO2 and Ta2O5) were susceptible to significant native oxide diffusion. The alkyl precursor used for the growth of Al 2O3 was relatively ineffective at removing the oxides but was a good diffusion barrier. In all cases the native oxides were more stable on GaAs compared to InAs. This project utilized a new methodology for the detection of arsenic oxide diffusion using transmission FTIR, and expanded the knowledge of the complexities of the high-k/III-V interface.

A new tridentate Schiff base Cu(II) complex: synthesis, experimental and theoretical studies on its crystal structure, FT-IR and UV-Visible spectra.

PubMed

Saheb, Vahid; Sheikhshoaie, Iran; Setoodeh, Nasim; Rudbari, Hadi Amiri; Bruno, Giuseppe

2013-06-01

A new Cu(II) complex [Cu(L)(NCS)] has been synthesized, using 1-(N-salicylideneimino)-2-(N,N-methyl)-aminoethane as tridentate ONN donor Schiff base ligand (HL). The dark green crystals of the compound are used for single-crystal X-ray analysis and measuring Fourier Transform Infrared (FT-IR) and UV-Visible spectra. Electronic structure calculations at the B3LYP and MP2 levels of theory are performed to optimize the molecular geometry and to calculate the UV-Visible and FT-IR spectra of the compound. Vibrational assignments and analysis of the fundamental modes of the compound are performed. Time-dependent density functional theory (TD-DFT) method is used to calculate the electronic transitions of the complex. A scaling factor of 1.015 is obtained for vibrational frequencies computed at the B3LYP level using basis sets 6-311G(d,p). It is found that solvent has a profound effect on the electronic absorption spectrum. The UV-Visible spectrum of the complex recorded in DMSO and DMF solution can be correctly predicted by a model in which DMSO and DMF molecules are coordinated to the central Cu atom via their oxygen atoms. Copyright © 2013 Elsevier B.V. All rights reserved.

Novel laser gain and time-resolved FTIR studies of photochemistry

NASA Technical Reports Server (NTRS)

Leone, Stephen R.

1990-01-01

Several techniques are discussed which can be used to explore laboratory photochemical processes and kinetics relevant to planetary atmospheres; these include time-resolved laser gain-versus-absorption spectroscopy and time-resolved Fourier transform infrared (FTIR) emission studies. The laser gain-versus-absorption method employed tunable diode and F-center lasers to determine the yields of excited photofragments and their kinetics. The time-resolved FTIR technique synchronizes the sweep of a commercial FTIR with a pulsed source of light to obtain emission spectra of novel transient species in the infrared. These methods are presently being employed to investigate molecular photodissociation, the yields of excited states of fragments, their subsequent reaction kinetics, Doppler velocity distributions, and velocity-changing collisions of translationally fast atoms. Such techniques may be employed in future investigations of planetary atmospheres, for example to study polycyclic aromatic hydrocarbons related to cometary emissions, to analyze acetylene decomposition products and reactions, and to determine spectral features in the near infrared and infrared wavelength regions for planetary molecules and clusters.

Computational model for noncontact atomic force microscopy: energy dissipation of cantilever.

PubMed

Senda, Yasuhiro; Blomqvist, Janne; Nieminen, Risto M

2016-09-21

We propose a computational model for noncontact atomic force microscopy (AFM) in which the atomic force between the cantilever tip and the surface is calculated using a molecular dynamics method, and the macroscopic motion of the cantilever is modeled by an oscillating spring. The movement of atoms in the tip and surface is connected with the oscillating spring using a recently developed coupling method. In this computational model, the oscillation energy is dissipated, as observed in AFM experiments. We attribute this dissipation to the hysteresis and nonconservative properties of the interatomic force that acts between the atoms in the tip and sample surface. The dissipation rate strongly depends on the parameters used in the computational model.

Core-shell carbon nanosphere-TiO2 composite and hollow TiO2 nanospheres prepared by atomic layer deposition

NASA Astrophysics Data System (ADS)

Bakos, L. P.; Justh, N.; Hernádi, K.; Kiss, G.; Réti, B.; Erdélyi, Z.; Parditka, B.; Szilágyi, I. M.

2016-10-01

Core-shell carbon-TiO2 composite and hollow TiO2 nanospheres were prepared using carbon nanospheres as hard-templates, coating them with TiO2 using atomic layer deposition, and subsequent burning out of the carbon cores. The bare carbon, the composite carbon-TiO2 and the hollow TiO2 nanospheres were characterized with TG/DTA-MS, FTIR, XRD and SEM-EDX.

Atomic Layer Deposition of L-Alanine Polypeptide

DOE PAGES

Fu, Yaqin; Li, Binsong; Jiang, Ying-Bing; ...

2014-10-30

L-Alanine polypeptide thin films were synthesized via atomic layer deposition (ALD). Rather, instead of using an amino acid monomer as the precursor, an L-alanine amino acid derivatized with a protecting group was used to prevent self-polymerization, increase the vapor pressure, and allow linear cycle-by-cycle growth emblematic of ALD. Moreover, the successful deposition of a conformal polypeptide film has been confirmed by FTIR, TEM, and Mass Spectrometry, and the ALD process has been extended to polyvaline.

Structure of 1:1 complex of 1-naphthylmethyl ester of monensin A with sodium perchlorate studied by X-ray, FT-IR and ab initio methods

NASA Astrophysics Data System (ADS)

Huczyński, Adam; Janczak, Jan; Brzezinski, Bogumil

2012-12-01

A new crystalline complex formed between 1-naphthylmethyl ester of the naturally occurring antibiotic - monensin A (MON8) with sodium perchlorate has been obtained and studied using X-ray crystallography and FT-IR spectroscopy. The X-ray data of the complex show that MON8 forms a pseudo-cyclic structure stabilised by one weak intramolecular hydrogen bond and the sodium cation co-ordinated by two oxygen atoms of hydroxyl groups and four etheric oxygen atoms in the hydrophilic sphere. Within this structure the oxygen atoms of the ester groups are not involved in the coordination of sodium cation. In contrast to the solid state structure of the complex, in acetonitrile solution an equilibrium between two structures, in which the oxygen atom of the carbonyl ester group is either involved or not involved in the complexation of the sodium cation, is found. In acetonitrile this equilibrium is shifted towards the latter structure i.e. the structure existing in the solid state. The gas-phase structure of [MON8sbnd Na]+ cation as shown the ab initio MO calculations is comparable with the crystal one. Three-dimensional molecular electrostatic potential calculated for the neutral MON8 and [MON8sbnd Na]+ molecules is helpful for understanding the structural aspects of the sodium complex formation.

Multiloop atom interferometer measurements of chameleon dark energy in microgravity

NASA Astrophysics Data System (ADS)

Chiow, Sheng-wey; Yu, Nan

2018-02-01

Chameleon field is one of the promising candidates of dark energy scalar fields. As in all viable candidate field theories, a screening mechanism is implemented to be consistent with all existing tests of general relativity. The screening effect in the chameleon theory manifests its influence limited only to the thin outer layer of a bulk object, thus producing extra forces orders of magnitude weaker than that of the gravitational force of the bulk. For pointlike particles such as atoms, the depth of screening is larger than the size of the particle, such that the screening mechanism is ineffective and the chameleon force is fully expressed on the atomic test particles. Extra force measurements using atom interferometry are thus much more sensitive than bulk mass based measurements, and indeed have placed the most stringent constraints on the parameters characterizing chameleon field. In this paper, we present a conceptual measurement approach for chameleon force detection using atom interferometry in microgravity, in which multiloop atom interferometers exploit specially designed periodic modulation of chameleon fields. We show that major systematics of the dark energy force measurements, i.e., effects of gravitational forces and their gradients, can be suppressed below all hypothetical chameleon signals in the parameter space of interest.

Nonmonotonic velocity dependence of atomic friction.

PubMed

Reimann, Peter; Evstigneev, Mykhaylo

2004-12-03

We propose a theoretical model for friction force microscopy experiments with special emphasis on the realistic description of dissipation and inertia effects. Its main prediction is a nonmonotonic dependence of the friction force upon the sliding velocity of the atomic force microscope tip relative to an atomically flat surface. The region around the force maximum can be approximately described by a universal scaling law and should be observable under experimentally realistic conditions.

Development of a force sensor using atom interferometry to constrain theories on dark matter and dark energy

NASA Astrophysics Data System (ADS)

Schlupf, Chandler; Niederriter, Robert; Bohr, Eliot; Khamis, Sami; Park, Youna; Szwed, Erik; Hamilton, Paul

2017-04-01

Atom interferometry has been used in many precision measurements such as Newton's gravitational constant, the fine structure constant, and tests of the equivalence principle. We will perform atom interferometry in an optical lattice to measure the force felt by an atom due to a test mass in search of new forces suggested by dark matter and dark energy theories. We will be developing a new apparatus using laser-cooled ytterbium to continuously measure this force by observing their Bloch oscillations. Interfering atoms in an optical lattice allows continuous measurements in a small volume over a long period of time, enabling our device to be sensitive to time-varying forces while minimizing vibrational noise. We present the details of this experiment and the progress on it thus far.

Concept for room temperature single-spin tunneling force microscopy with atomic spatial resolution

NASA Astrophysics Data System (ADS)

Payne, Adam

A study of a force detected single-spin magnetic resonance measurement concept with atomic spatial resolution is presented. The method is based upon electrostatic force detection of spin-selection rule controlled single electron tunneling between two electrically isolated paramagnetic states. Single-spin magnetic resonance detection is possible by measuring the force detected tunneling charge noise on and off spin resonance. Simulation results of this charge noise, based upon physical models of the tunneling and spin physics, are directly compared to measured atomic force microscopy (AFM) system noise. The results show that the approach could provide single-spin measurement of electrically isolated defect states with atomic spatial resolution at room temperature.

Atomic-resolution single-spin magnetic resonance detection concept based on tunneling force microscopy

NASA Astrophysics Data System (ADS)

Payne, A.; Ambal, K.; Boehme, C.; Williams, C. C.

2015-05-01

A study of a force detected single-spin magnetic resonance measurement concept with atomic spatial resolution is presented. The method is based upon electrostatic force detection of spin-selection rule controlled single-electron tunneling between two electrically isolated paramagnetic states. Single-spin magnetic resonance detection is possible by measuring the force detected tunneling charge noise on and off spin resonance. Simulation results of this charge noise, based upon physical models of the tunneling and spin physics, are directly compared to measured atomic force microscopy system noise. The results show that the approach could provide single-spin measurement of electrically isolated qubit states with atomic spatial resolution at room temperature.

Surface Biology of DNA by Atomic Force Microscopy

NASA Astrophysics Data System (ADS)

Hansma, Helen G.

2001-10-01

The atomic force microscope operates on surfaces. Since surfaces occupy much of the space in living organisms, surface biology is a valid and valuable form of biology that has been difficult to investigate in the past owing to a lack of good technology. Atomic force microscopy (AFM) of DNA has been used to investigate DNA condensation for gene therapy, DNA mapping and sizing, and a few applications to cancer research and to nanotechnology. Some of the most exciting new applications for atomic force microscopy of DNA involve pulling on single DNA molecules to obtain measurements of single-molecule mechanics and thermodynamics.

Evidence for non-conservative current-induced forces in the breaking of Au and Pt atomic chains.

PubMed

Sabater, Carlos; Untiedt, Carlos; van Ruitenbeek, Jan M

2015-01-01

This experimental work aims at probing current-induced forces at the atomic scale. Specifically it addresses predictions in recent work regarding the appearance of run-away modes as a result of a combined effect of the non-conservative wind force and a 'Berry force'. The systems we consider here are atomic chains of Au and Pt atoms, for which we investigate the distribution of break down voltage values. We observe two distinct modes of breaking for Au atomic chains. The breaking at high voltage appears to behave as expected for regular break down by thermal excitation due to Joule heating. However, there is a low-voltage breaking mode that has characteristics expected for the mechanism of current-induced forces. Although a full comparison would require more detailed information on the individual atomic configurations, the systems we consider are very similar to those considered in recent model calculations and the comparison between experiment and theory is very encouraging for the interpretation we propose.

Phase modulation atomic force microscope with true atomic resolution

NASA Astrophysics Data System (ADS)

Fukuma, Takeshi; Kilpatrick, Jason I.; Jarvis, Suzanne P.

2006-12-01

We have developed a dynamic force microscope (DFM) working in a novel operation mode which is referred to as phase modulation atomic force microscopy (PM-AFM). PM-AFM utilizes a fixed-frequency excitation signal to drive a cantilever, which ensures stable imaging even with occasional tip crash and adhesion to the surface. The tip-sample interaction force is detected as a change of the phase difference between the cantilever deflection and excitation signals and hence the time response is not influenced by the Q factor of the cantilever. These features make PM-AFM more suitable for high-speed imaging than existing DFM techniques such as amplitude modulation and frequency modulation atomic force microscopies. Here we present the basic principle of PM-AFM and the theoretical limit of its performance. The design of the developed PM-AFM is described and its theoretically limited noise performance is demonstrated. Finally, we demonstrate the true atomic resolution imaging capability of the developed PM-AFM by imaging atomic-scale features of mica in water.

Atmospheric-pressure DBD plasma-assisted surface modification of polymethyl methacrylate: A study on cell growth/proliferation and antibacterial properties

NASA Astrophysics Data System (ADS)

Rezaei, Fatemeh; Shokri, Babak; Sharifian, M.

2016-01-01

This paper reports polymethyl methacrylate (PMMA) surface modification by atmospheric-pressure oxygen dielectric barrier discharge (DBD) plasma to improve its biocompatibility and antibacterial effects. The role of plasma system parameters, such as electrode gap, treatment time and applied voltage, on the surface characteristics and biological responses was studied. The surface characteristics of PMMA films before and after the plasma treatments were analyzed by water contact angle (WCA) goniometry, atomic force microscopy (AFM) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Also, acid-base approach was used for evaluation of surface free energy (SFE) and its components. Stability of plasma treatment or aging effect was examined by repeating water contact angle measurements in a period of 9 days after treatment. Moreover, the antibacterial properties of samples were investigated by bacterial adhesion assay against Escherichia coli. Additionally, all samples were tested for the biocompatibility by cell viability assay of mouse embryonic fibroblast. WCA measurements indicated that the surface wettability of PMMA films was improved by increasing surface free energy via oxygen DBD plasma treatments. AFM measurement revealed that surface roughness was slightly increased after treatments, and ATR-FTIR analysis showed that more polar groups were introduced on the plasma-treated PMMA film surface. The results also demonstrated an enhancement of antibacterial performance of the modified surfaces. Furthermore, it was observed that plasma-treated samples exhibited significantly better biocompatibility, comparing to the pristine one.

Molecular structure, vibrational spectroscopic (FT-IR, FT-Raman), UV-vis spectra, first order hyperpolarizability, NBO analysis, HOMO and LUMO analysis, thermodynamic properties of benzophenone 2,4-dicarboxylic acid by ab initio HF and density functional method

NASA Astrophysics Data System (ADS)

Chaitanya, K.

2012-02-01

The FT-IR (4000-450 cm -1) and FT-Raman spectra (3500-100 cm -1) of benzophenone 2,4-dicarboxylic acid (2,4-BDA) have been recorded in the condensed state. Density functional theory calculation with B3LYP/6-31G(d,p) basis set have been used to determine ground state molecular geometries (bond lengths and bond angles), harmonic vibrational frequencies, infrared intensities, Raman activities and bonding features of the title compounds. The assignments of the vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA) following the scaled quantum mechanical force field (SQMFF) methodology. The first order hyperpolarizability ( β0) and related properties ( β, α0 and Δ α) of 2,4-BDA is calculated using HF/6-31G(d,p) method on the finite-field approach. The stability of molecule has been analyzed by using NBO analysis. The calculated first hyperpolarizability shows that the molecule is an attractive molecule for future applications in non-linear optics. The calculated HOMO and LUMO energies show that charge transfer occurs within these molecules. Mulliken population analysis on atomic charges is also calculated. Because of vibrational analyses, the thermodynamic properties of the title compound at different temperatures have been calculated. Finally, the UV-vis spectra and electronic absorption properties were explained and illustrated from the frontier molecular orbitals.

Poly(dimethyl siloxane) surface modification with biosurfactants isolated from probiotic strains.

PubMed

Pinto, S; Alves, P; Santos, A C; Matos, C M; Oliveiros, B; Gonçalves, S; Gudiña, E; Rodrigues, L R; Teixeira, J A; Gil, M H

2011-09-15

Depending on the final application envisaged for a given biomaterial, many surfaces must be modified before use. The material performance in a biological environment is mainly mediated by its surface properties that can be improved using suitable modification methods. The aim of this work was to coat poly(dimethyl siloxane) (PDMS) surfaces with biosurfactants (BSs) and to evaluate how these compounds affect the PDMS surface properties. BSs isolated from four probiotic strains (Lactococcus lactis, Lactobacillus paracasei, Streptococcus thermophilus A, and Streptococcus thermophilus B) were used. Bare PDMS and PDMS coated with BSs were characterized by contact angle measurements, infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The influence of the surface modifications on the materials blood compatibility was studied through thrombosis and hemolysis assays. The cytotoxicity of these materials was tested against rat peritoneal macrophages. AFM results demonstrated the successful coating of the surfaces. Also, by contact angle measurements, an increase of the coated surfaces hydrophilicity was seen. Furthermore, XPS analysis indicated a decrease of the silicon content at the surface, and ATR-FTIR results showed the presence of BS characteristic groups as a consequence of the modification. All the studied materials revealed no toxicity and were found to be nonhemolytic. The proposed approach for the modification of PDMS surfaces was found to be effective and opens new possibilities for the application of these surfaces in the biomedical field. Copyright © 2011 Wiley Periodicals, Inc.

Improving Corrosion Resistance of 316L Austenitic Stainless Steel Using ZrO2 Sol-Gel Coating in Nitric Acid Solution

NASA Astrophysics Data System (ADS)

Kazazi, Mahdi; Haghighi, Milad; Yarali, Davood; Zaynolabedini, Masoomeh H.

2018-03-01

In this study, thin-film coating of zirconium oxide (ZrO2) was prepared by sol-gel method and subsequent heat treatment process. The sol was prepared by controlled hydrolysis of zirconium tetrapropoxide using acetic acid and ethanol/acetylacetone mixture as catalyst and chelating agent, respectively, and finally deposited onto the 316L austenitic stainless steel (316L SS) using dip coating method in order to improve its corrosion resistance in nitric acid medium. The composition, structure, and morphology of the coated surface were investigated by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The obtained results from XRD and FTIR state the formation of tetragonal and monoclinic ZrO2 phase. Also, the obtained results from surface morphology investigation by SEM and AFM indicate the formation of smooth, homogeneous and uniform coatings on the steel substrate. Then, the corrosion behavior of stainless steel was investigated in a 1 and 10 M nitric acid solutions using electrochemical impedance spectroscopy and linear polarization test. The obtained results from these tests for ZrO2-coated specimens indicated a considerable improvement in the corrosion resistance of 316L stainless steel by an increase in corrosion potential and transpassive potential, and a decrease in passive current density and corrosion current density. The decrease in passive current density in both the concentration of solutions was two orders of magnitude from bare to coated specimens.

Formation and Characterization of Self-Assembled Phenylboronic Acid Derivative Monolayers toward Developing Monosaccharide Sensing-Interface

PubMed Central

Chen, Hongxia; Lee, Minsu; Lee, Jaebeom; Kim, Jae-Ho; Gal, Yeong-Soon; Hwang, Yoon-Hwae; An, Won Gun; Koh, Kwangnak

2007-01-01

We designed and synthesized phenylboronic acid as a molecular recognition model system for saccharide detection. The phenylboronic acid derivatives that have boronic acid moiety are well known to interact with saccharides in aqueous solution; thus, they can be applied to a functional interface of saccharide sensing through the formation of self-assembled monolayer (SAM). In this study, self-assembled phenylboronic acid derivative monolayers were formed on Au surface and carefully characterized by atomic force microscopy (AFM), Fourier transform infrared reflection absorption spectroscopy (FTIR-RAS), surface enhanced Raman spectroscopy (SERS), and surface electrochemical measurements. The saccharide sensing application was investigated using surface plasmon resonance (SPR) spectroscopy. The phenylboronic acid monolayers showed good sensitivity of monosaccharide sensing even at the low concentration range (1.0 × 10−12 M). The SPR angle shift derived from interaction between phenylboronic acid and monosaccharide was increased with increasing the alkyl spacer length of synthesized phenylboronic acid derivatives.

One-dimensional nanoferroic rods; synthesis and characterization

NASA Astrophysics Data System (ADS)

Ahmed, M. A.; Seddik, U.; Okasha, N.; Imam, N. G.

2015-11-01

One-dimensional nanoferroic rods of BaTiO3 were synthesized by improved citrate auto-combustion technology using tetrabutyl titanate. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), transmission electron microscopy (TEM), atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR) have been used to characterize the prepared sample. The results indicated that the crystal structure of BaTiO3 is tetragonal phase with an average crystallite size of 47 nm. SEM image gives a cauliflower-like morphology of the agglomerated nanorods. The stoichiometry of the chemical composition of the BaTiO3 ceramic was confirmed by EDX. TEM micrograph exhibited that BaTiO3 nanoparticles have rod-like shape with an average length of 120 nm and width of 43 nm. AFM was used to investigate the surface topography and its roughness. The topography image in 3D showed that the BaTiO3 particles have a rod shape with an average particle size of 116 nm which in agreement with 3D TEM result.

Conformational changes and metastable states induced in proteins by green light

NASA Astrophysics Data System (ADS)

Comorosan, Sorin; Popescu, Irinel; Polosan, Silviu; Pirvu, Cristian; Ionescu, Elena; Paslaru, Liliana; Apostol, Marian

2015-01-01

In this paper we report conformational changes recorded on a protein molecule (α-amylase) under green light irradiation. In order to explain the experimental results we advanced the hypothesis that green light induces electric dipoles in the protein, which interact with each other, generating conformational modifications toward a more compact design, with different physical properties. The experiments were carried out with un-polarized light (λ = 520 nm) from a light-emitting-diode (1000 lm, 20 W, 105 mW on the target). In view of the character of our hypothesis, and corroborated with all our experimental results, we suggest that this phenomenon may be more extended and general, specific for a larger class of proteins, occurring on the protein macromolecules under the green light. The effects of α-amylase protein irradiation were revealed by circular dichroism, fluorescence, Raman and FTIR-spectroscopies, zeta potential, cyclic voltammetry, electric impedance spectroscopy and atomic force microscopy. Tentatively, we term the novel conformations as P∗ (polarized) proteins.

Surface modification and characterization of basalt fibers as potential reinforcement of concretes

NASA Astrophysics Data System (ADS)

Iorio, M.; Santarelli, M. L.; González-Gaitano, G.; González-Benito, J.

2018-01-01

Basalt fibers were surface treated with silane coupling agents as a method to enhance the adhesion and durability of fiber-matrix interfaces in concrete based composite materials. In particular, this work has been focused on the study of basalt fibers chemical coatings with aminosilanes and their subsequent characterization. Surface treatments were carried out after removing the original sizing applied by manufacturer and pretreating them with an activation process of surface silanol regeneration. Different samples were considered to make convenient comparisons: as received fibers (commercial), calcinated fibers (without commercial sizing), activated samples (calcinated fibers subjected to an acid process for hydroxyl regeneration), and silanized fibers with γ-aminopropiltriethoxysilane, γ-aminopropilmethyldiethoxysilane and a mixture of 50% by weight of both silanes. A deep characterization was carried out in terms of structure using X-ray diffraction, XRD, and Fourier transform infrared spectroscopy, FTIR, thermal properties by thermogravimetric analysis, TGA, coupled with single differential thermal analysis, SDTA, and morphology by scanning electron microscopy, SEM, and atomic force microscopy, AFM.

Green synthesis of silver nanoparticles using Terminalia chebula extract at room temperature and their antimicrobial studies

NASA Astrophysics Data System (ADS)

Mohan Kumar, Kesarla; Sinha, Madhulika; Mandal, Badal Kumar; Ghosh, Asit Ranjan; Siva Kumar, Koppala; Sreedhara Reddy, Pamanji

2012-06-01

A green rapid biogenic synthesis of silver nanoparticles (Ag NPs) using Terminalia chebula (T. chebula) aqueous extract was demonstrated in this present study. The formation of silver nanoparticles was confirmed by Surface Plasmon Resonance (SPR) at 452 nm using UV-visible spectrophotometer. The reduction of silver ions to silver nanoparticles by T. chebula extract was completed within 20 min which was evidenced potentiometrically. Synthesised nanoparticles were characterised using UV-vis spectroscopy, Fourier transformed infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The hydrolysable tannins such as di/tri-galloyl-glucose present in the extract were hydrolyzed to gallic acid and glucose that served as reductant while oxidised polyphenols acted as stabilizers. In addition, it showed good antimicrobial activity towards both Gram-positive bacteria (S. aureus ATCC 25923) and Gram-negative bacteria (E. coli ATCC 25922). Industrially it may be a smart option for the preparation of silver nanoparticles.

Quaternization enhances the transgene expression efficacy of aminoglycoside-derived polymers.

PubMed

Miryala, Bhavani; Feng, Yunpeng; Omer, Ala; Potta, Thrimoorthy; Rege, Kaushal

2015-07-15

The objective of the present study was to synthesize and investigate the transgene expression efficacy of quaternized derivatives of aminoglycoside polymers in different cancer cell lines. A series of glycidyltrimethylammonium chloride (GTMAC) derivatives of aminoglycoside polymers (GTMAC-AM polymers), containing varying degrees of quaternization (13-45%), were synthesized. The structures and properties of GTMAC-AM polymers were investigated using FT-IR and (1)H NMR spectroscopy. Physicochemical factors that influence transgene expression efficacy including DNA binding, hydrodynamic size, zeta potential and cytotoxicity, were determined. Formation of polymer-plasmid DNA complexes was also visualized using atomic force microscopy. GTMAC-AM polymers demonstrated higher transgene expression efficacies compared to their parent polymers, 25 kDa poly(ethyleneimine), as well as Lipofectamine-3000. Our results indicate that quaternization enhances the transgene expression efficacy and reduces the cytotoxicity of aminoglycoside-derived polymers, making it an attractive strategy for nucleic acid delivery with these new materials. Copyright © 2015 Elsevier B.V. All rights reserved.

A Surface Plasmon Resonance-Based Optical Fiber Probe Fabricated with Electropolymerized Molecular Imprinting Film for Melamine Detection

PubMed Central

Zheng, Yongping; Zhang, Tingwei; Wu, Songjie; Zhang, Jue; Fang, Jing

2018-01-01

Molecularly imprinted polymer (MIP) films prepared by bulk polymerization suffer from numerous deficiencies, including poor mass transfer ability and difficulty in controlling reaction rate and film thickness, which usually result in poor repeatability. However, polymer film synthesized by electropolymerization methods benefit from high reproducibility, simplicity and rapidity of preparation. In the present study, an Au film served as the refractive index-sensitive metal film to couple with the light leaked out from optical fiber core and the electrode for electropolymerizing MIP film simultaneously. The manufactured probe exhibited satisfactory sensitivity and specificity. Furthermore, the surface morphology and functional groups of the synthesized MIP film were characterized by Atomic Force Microscopy (AFM) and Fourier transform infrared microspectroscopy (FTIR) for further insights into the adsorption and desorption processes. Given the low cost, label-free test, simple preparation process and fast response, this method has a potential application to monitor substances in complicated real samples for out-of-lab test in the future. PMID:29522472

Feasibility study of the natural derived chitosan dialdehyde for chemical modification of collagen.

PubMed

Liu, Xinhua; Dan, Nianhua; Dan, Weihua; Gong, Juxia

2016-01-01

The aim of this study is to evaluate the chemical crosslinking effects of the natural derived chitosan dialdehyde (OCS) on collagen. Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC) and circular dichroism (CD) measurements suggest that introducing OCS might not destroy the natural triple helix conformation of collagen but enhance the thermal-stability of collagen. Meanwhile, a denser fibrous network of cross-linked collagen is observed by atomic force microscopy. Further, scanning electron microscopy (SEM) and aggregation kinetics analysis confirm that the fibrillation process of collagen advances successfully and OCS could lengthen the completion time of collagen fibrillogenesis but raise the reconstitution rate of collagen fibrils or microfibrils. Besides, the cytocompatibility analysis implies that when the dosage of OCS is less than 15%, introducing OCS into collagen might be favorable for the cell's adhesion, growth and proliferation. Taken as a whole, the present study demonstrates that OCS might be an ideal crosslinker for the chemical fixation of collagen. Copyright © 2015 Elsevier B.V. All rights reserved.

Excimer UV lamp irradiation induced grafting on synthetic polymers

NASA Astrophysics Data System (ADS)

Praschak, D.; Bahners, T.; Schollmeyer, E.

Surface modifications on polyethyleneterephthalate (PET) films following excimer UV lamp irradiation induced grafting were studied. Characteristics of the modifications depending on the conditions during the irradiation were analysed using contact-angle measurements, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR). Depending on the conditions during the irradiation different surface modifications were obtained, which can generally be classified regarding the hydrophilic or hydrophobic characteristics of the resulting surface. It is shown that not every substance that meets the general demands will be grafted on synthetic polymers using excimer UV radiation. Examples of agents that can simply be grafted onto polymer surfaces and those that undergo further crosslinking, building up thin films are listed. Agents used for grafting on polymers are 1,5-hexadiene, perfluoro-4-methyl-pent-2-ene, polyethyleneglycol 200, monosilane and polyethylene. The transferability of the effects achieved to substrates such as polyparaphenylene terephthalamide or polymetaphenylene isophthalamide is shown.

Biosynthesis of silver nanoparticles using lemon leaves extract and its application for antimicrobial finish on fabric

NASA Astrophysics Data System (ADS)

Vankar, Padma S.; Shukla, Dhara

2012-06-01

Preparation of silver nanoparticles have been carried out using aqueous extract of lemon leaves ( Citrus limon) which acts as reducing agent and encapsulating cage for the silver nanoparticles. These silver nanoparticles have been used for durable textile finish on cotton and silk fabrics. Remarkable antifungal activity has been observed in the treated fabrics. The antimicrobial activity of silver nanoparticles derived from lemon leaves showed enhancement in activity due to synergistic effect of silver and essential oil components of lemon leaves. The present investigation shows the extracellular synthesis of highly stable silver nanoparticles by biotransformation using the extract of lemon leaves by controlled reduction of the Ag+ ion to Ag0. Further the silver nanoparticles were used for antifungal treatment of fabrics which was tested by antifungal activity assessment of textile material by Agar diffusion method against Fusarium oxysporum and Alternaria brassicicola. Formation of the metallic nanoparticles was established by FT-IR, UV-Visible spectroscopy, transmission electron microscopy, scanning electron microscopy, atomic force microscopy.

Protein Adsorption Alters Hydrophobic Surfaces Used for Suspension Culture of Pluripotent Stem Cells.

PubMed

Jonas, Steven J; Stieg, Adam Z; Richardson, Wade; Guo, Shuling; Powers, David N; Wohlschlegel, James; Dunn, Bruce

2015-02-05

This Letter examines the physical and chemical changes that occur at the interface of methyl-terminated alkanethiol self-assembled monolayers (SAMs) after exposure to cell culture media used to derive embryoid bodies (EBs) from pluripotent stem cells. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy analysis of the SAMs indicates that protein components within the EB cell culture medium preferentially adsorb at the hydrophobic interface. In addition, we examined the adsorption process using surface plasmon resonance and atomic force microscopy. These studies identify the formation of a porous, mat-like adsorbed protein film with an approximate thickness of 2.5 nm. Captive bubble contact angle analysis reveals a shift toward superhydrophilic wetting behavior at the cell culture interface due to adsorption of these proteins. These results show how EBs are able to remain in suspension when derived on hydrophobic materials, which carries implications for the rational design of suspension culture interfaces for lineage specific stem-cell differentiation.

Complexation of amyloid fibrils with charged conjugated polymers.

PubMed

Ghosh, Dhiman; Dutta, Paulami; Chakraborty, Chanchal; Singh, Pradeep K; Anoop, A; Jha, Narendra Nath; Jacob, Reeba S; Mondal, Mrityunjoy; Mankar, Shruti; Das, Subhadeep; Malik, Sudip; Maji, Samir K

2014-04-08

It has been suggested that conjugated charged polymers are amyloid imaging agents and promising therapeutic candidates for neurological disorders. However, very less is known about their efficacy in modulating the amyloid aggregation pathway. Here, we studied the modulation of Parkinson's disease associated α-synuclein (AS) amyloid assembly kinetics using conjugated polyfluorene polymers (PF, cationic; PFS, anionic). We also explored the complexation of these charged polymers with the various AS aggregated species including amyloid fibrils and oligomers using multidisciplinary biophysical techniques. Our data suggests that both polymers irrespective of their different charges in the side chains increase the fibrilization kinetics of AS and also remarkably change the morphology of the resultant amyloid fibrils. Both polymers were incorporated/aligned onto the AS amyloid fibrils as evident from electron microscopy (EM) and atomic force microscopy (AFM), and the resultant complexes were structurally distinct from their pristine form of both polymers and AS supported by FTIR study. Additionally, we observed that the mechanism of interactions between the polymers with different species of AS aggregates were markedly different.

Copper Phthalocyanine Functionalized Single-Walled Carbon Nanotubes: Thin Films for Optical Detection.

PubMed

Banimuslem, Hikmat; Hassan, Aseel; Basova, Tamara; Durmuş, Mahmut; Tuncel, Sinem; Esenpinar, Aliye Asli; Gürek, Ayşe Gül; Ahsen, Vefa

2015-03-01

Thin films of non-covalently hybridized single-walled carbon nanotubes (SWCNT) and tetra-substituted copper phthalocyanine (CuPcR4) molecules have been produced from their solutions in dimethylformamide (DMF). FTIR spectra revealed the 7π-7π interaction between SWCNTs and CuPcR4 molecules. DC conductivity of films of acid-treated SWCNT/CuPcR4 hybrid has increased by more than three orders of.magnitude in comparison with conductivity of CuPcR4 films. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements have shown that films obtained from the acid-treated SWCNTs/CuPcR4 hybrids demonstrated more homogenous surface which is ascribed to the highly improved solubility of the hybrid powder in DMF Using total internal reflection ellipsometry spectroscopy (TIRE), thin films of the new hybrid have been examined as an optical sensing membrane for the detection of benzo[a]pyrene in water to demonstrate the sensing properties of the hybrid.

Utilization of Corn Cob and TiO2 Photocatalyst Thin Films for Dyes Removal.

PubMed

Gan, Hui-Yee; Leow, Li-Eau; Ong, Siew-Teng

2017-01-01

The effectiveness of using TiO2 and corn cob films to remove Malachite Green oxalate (MG) and Acid Yellow 17 (AY 17) from binary dye solution was studied. The immobilization method in this study can avoid the filtration step which is not suited for practical applications. Batch studies were performed under different experimental conditions and the parameters studied involved initial pH of dye solution, initial dye concentration and contact time and reusability. The equilibrium data of MG and AY 17 conform to Freundlich and Langmuir isotherm model, respectively. The percentage removal of MG remained high after four sorption cycles, however for AY 17, a greater reduction was observed. The removal of both dyes were optimized and modeled via Plackett- Burman design (PB) and Response Surface Methodology (RSM). IR spectrum and surface conditions analyses were carried out using fourier-transform infrared spectrophotometer (FTIR), scanning electron microscope (SEM) and atomic force microscope (AFM), respectively.

Nanostructured zinc oxide thin film for application to surface plasmon resonance based cholesterol biosensor

NASA Astrophysics Data System (ADS)

Kaur, Gurpreet; Tomar, Monika; Gupta, Vinay

2015-11-01

ZnO thin film was deposited on gold coated glass prism by RF sputtering technique in glancing angle deposition (GLAD) configuration. The structural, morphological and optical properties of the deposited film were investigated using X-ray diffraction (XRD), Atomic Force Microscopy (AFM) and Fourier Transform Infrared (FTIR) Spectroscopy. ZnO coated Au prisms (ZnO/Au/prism) were used to excite surface plasmons in Kretschmann configuration at the Au- ZnO interface on a laboratory assembled Surface Plasmon Resonance (SPR) measurement setup. Cholesterol oxidase (ChOx) enzyme was immobilized on the ZnO/Au/prism structure by physical adsorption technique. Polydimethylsiloxane (PDMS) microchannels were fabricated over ChOx/ZnO/Au/prism system and various concentrations of cholesterol were passed over the sensor surface. The concentration of cholesterol was varied from 0.12 to 10.23 mM and the SPR reflectance curves were recorded in both static as well as dynamic modes demonstrating a high sensitivity of 0.36° mM-1.

Polyethylene Oxide Films Polymerized by Radio Frequency Plasma-Enhanced Chemical Vapour Phase Deposition and Its Adsorption Behaviour of Platelet-Rich Plasma

NASA Astrophysics Data System (ADS)

Hu, Wen-Juan; Xie, Fen-Yan; Chen, Qiang; Weng, Jing

2008-10-01

We present polyethylene oxide (PEO) functional films polymerized by rf plasma-enhanced vapour chemical deposition (rf-PECVD) on p-Si (100) surface with precursor ethylene glycol dimethyl ether (EGDME) and diluted Ar in pulsed plasma mode. The influences of discharge parameters on the film properties and compounds are investigated. The film structure is analysed by Fourier transform infrared (FTIR) spectroscopy. The water contact angle measurement and atomic force microscope (AFM) are employed to examine the surface polarity and to detect surface morphology, respectively. It is concluded that the smaller duty cycle in pulsed plasma mode contributes to the rich C-O-C (EO) group on the surfaces. As an application, the adsorption behaviour of platelet-rich plasma on plasma polymerization films performed in-vitro is explored. The shapes of attached cells are studied in detail by an optic invert microscope, which clarifies that high-density C-O-C groups on surfaces are responsible for non-fouling adsorption behaviour of the PEO films.

Nutraceutically inspired pectin-Mg(OH)₂ nanocomposites for bioactive packaging applications.

PubMed

Moreira, Francys K V; De Camargo, Lais A; Marconcini, José M; Mattoso, Luiz H C

2013-07-24

This paper reports on the development of bioactive edible films based on pectin as a dietary matrix and magnesium hydroxide (Mg(OH)2) nanoplates as a reinforcing filler. Nanocomposites of high-methoxyl (HM) and low-methoxyl (LM) pectins were prepared using the casting method at concentrations of Mg(OH)2 ranging from 0.5 to 5 wt %. Atomic force microscopy and FTIR spectroscopy were employed to characterize the nanocomposite structure. The tensile properties and thermal stability of the nanocomposites were also examined to ascertain the effect of Mg(OH)2 inclusion and degree of methoxylation. The results provided evidence that the Mg(OH)2 nanoplates were uniformly dispersed and interacted strongly with the film matrix. The mechanical and thermal properties were significantly improved in the nanocomposite films compared to the control. Mg(OH)2 nanoplates were more effective in improving properties of LM pectin. Preliminary migration studies using arugula leaves confirmed that pectin-Mg(OH)2 nanocomposites can release magnesium hydroxide by contact, demonstrating their potential for magnesium supplementation in bioactive packaging.

Vibrational spectroscopic investigation and normal coordinate analysis of the fibrate hypolipidemic agent 5-(2,5-dimethylphenoxy)-2,2-dimethyl pentanoic acid (Gemfibrozil)

NASA Astrophysics Data System (ADS)

Priya, M. Siva; Benitta, T. Asenath; James, C.

2011-03-01

Colorless crystals of 5-(2,5-dimethylphenoxy)-2,2-dimethyl pentanoic acid were grown by slow evaporation method and the FT-IR and FT-Raman spectra of the sample were recorded in the region 4000-450 cm -1 and 4000-50 cm -1 respectively. Molecular structure is optimized with the help of B3LYP/6-31G (d) density functional theory method. Stability of the molecule arising from hyperconjugation and charge delocalization is confirmed by the natural bond orbital analysis (NBO). The results show that electron density (ED) in the σ ∗ antibonding orbitals and E (2) energies confirms the occurrence of intra-molecular charge transfer (ICT) within the molecule. The assignments of the vibrational spectra have been carried out with the help of Normal coordinate analysis following the scaled quantum mechanical force field (SQMFF) methodology. Mulliken population analysis on atomic charges is also calculated. The calculated HOMO and LUMO energy gap shows that charge transfer occurs within the molecule.

Nano CaCO₃ imprinted starch hybrid polyethylhexylacrylate\\polyvinylalcohol nanocomposite thin films.

PubMed

Prusty, Kalyani; Swain, Sarat K

2016-03-30

Starch hybrid polyethylhexylacrylate (PEHA)/polyvinylalcohol (PVA) nanocomposite thin films are prepared by different composition of nano CaCO3 in aqueous medium. The chemical interaction of nano CaCO3 with PEHA in presence of starch and PVA is investigated by Fourier transforms infrared spectroscopy (FTIR). X-ray diffraction (XRD) is used in order to study the change in crystallite size and d-spacing during the formation of nanocomposite thin film. The surface morphology of nanofilms is studied by scanning electron microscope (SEM). The topology and surface roughness of the films is noticed by atomic force microscope (AFM). The tensile strength, thermal stability and thermal conductivity of films are increased with increase in concentrations of CaCO3 nanopowder. The chemical resistance and biodegradable properties of the nanocomposite thin films are also investigated. The growth of bacteria and fungi in starch hybrid PEHA film is reduced substantially with imprint of nano CaCO3. Copyright © 2015 Elsevier Ltd. All rights reserved.

Lactoferrin-Immobilized Surfaces onto Functionalized PLA Assisted by the Gamma-Rays and Nitrogen Plasma to Create Materials with Multifunctional Properties.

PubMed

Stoleru, Elena; Zaharescu, Traian; Hitruc, Elena Gabriela; Vesel, Alenka; Ioanid, Emil G; Coroaba, Adina; Safrany, Agnes; Pricope, Gina; Lungu, Maria; Schick, Christoph; Vasile, Cornelia

2016-11-23

Both cold nitrogen radiofrequency plasma and gamma irradiation have been applied to activate and functionalize the polylactic acid (PLA) surface and the subsequent lactoferrin immobilization. Modified films were comparatively characterized with respect to the procedure of activation and also with unmodified sample by water contact angle measurements, mass loss, X-ray photoelectron spectroscopy (XPS), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), atomic force microscopy (AFM), and chemiluminescence measurements. All modified samples exhibit enhanced surface properties mainly those concerning biocompatibility, antimicrobial, and antioxidant properties, and furthermore, they are biodegradable and environmentally friendly. Lactoferrin deposited layer by covalent coupling using carbodiimide chemistry showed a good stability. It was found that the lactoferrin-modified PLA materials present significantly increased oxidative stability. Gamma-irradiated samples and lactoferrin-functionalized samples show higher antioxidant, antimicrobial, and cell proliferation activity than plasma-activated and lactoferrin-functionalized ones. The multifunctional materials thus obtained could find application as biomaterials or as bioactive packaging films.

Facile approach to the fabrication of a micropattern possessing nanoscale substructure.

PubMed

Ji, Qiang; Jiang, Xuesong; Yin, Jie

2007-12-04

On the basis of the combined technologies of photolithography and reaction-induced phase separation (RIPS), a facile approach has been successfully developed for the fabrication of a micropattern possessing nanoscale substructure on the thin film surface. This approach involves three steps. In the first step, a thin film was prepared by spin coating from a solution of a commercial random copolymer, polystyrene-r-poly(methyl methacrylate) (PS-r-PMMA) and a commercial crosslinker, trimethylolpropane triacrylate (TMPTA). In the second step, photolithograph was performed with the thin film using a 250 W high-pressure mercury lamp to produce the micropattern. Finally, the resulting micropattern was annealed at 200 degrees C for a certain time, and reaction-induced phase separation occurred. After soaking in chloroform for 4 h, nanoscale substructure was obtained. The whole processes were traced by atomic force microscopy (AFM), X-ray photoelectron spectrometry (XPS), and Fourier transform infrared (FTIR) spectroscopy, and the results supported the proposed structure.

Poly(ethylene oxide) surfactant polymers.

PubMed

Vacheethasanee, Katanchalee; Wang, Shuwu; Qiu, Yongxing; Marchant, Roger E

2004-01-01

We report on a series of structurally well-defined surfactant polymers that undergo surface-induced self-assembly on hydrophobic biomaterial surfaces. The surfactant polymers consist of a poly(vinyl amine) backbone with poly(ethylene oxide) and hexanal pendant groups. The poly(vinyl amine) (PVAm) was synthesized by hydrolysis of poly(N-vinyl formamide) following free radical polymerization of N-vinyl formamide. Hexanal and aldehyde-terminated poly(ethylene oxide) (PEO) were simultaneously attached to PVAm via reductive amination. Surfactant polymers with different PEO:hexanal ratios and hydrophilic/hydrophobic balances were prepared, and characterized by FT-IR, 1H-NMR and XPS spectroscopies. Surface active properties at the air/water interface were determined by surface tension measurements. Surface activity at a solid surface/water interface was demonstrated by atomic force microscopy, showing epitaxially molecular alignment for surfactant polymers adsorbed on highly oriented pyrolytic graphite. The surfactant polymers described in this report can be adapted for simple non-covalent surface modification of biomaterials and hydrophobic surfaces to provide highly hydrated interfaces.

Modified corrosion protection coatings for Concrete tower of Transmission line

NASA Astrophysics Data System (ADS)

Guo, Kai; Jing, Xiangyang; Wang, Hongli; Yue, Zengwu; Wu, Yaping; Mi, Xuchun; Li, Xingeng; Chen, Suhong; Fan, Zhibin

2017-12-01

By adding nano SiO2 particles, an enhanced K-PRTV anti-pollution flashover coating had been prepared. Optical profile meter (GT-K), atomic force microscopy (AFM) and infrared spectrometer (FT-IR) characterization were carried out on the coating surface analysis. With the use of modified epoxy resin as the base material, the supplemented by phosphate as a corrosion stabilizer, to achieve a corrosion of steel and galvanized steel with rust coating. Paint with excellent adhesion, more than 10MPa (1), resistant to neutral salt spray 1000h does not appear rust point. At the same time coating a large amount of ultra-fine zinc powder can be added for the tower galvanized layer zinc repair function, while the paint in the zinc powder for the tower to provide sacrificial anode protection, to achieve self-repair function of the coating. Compared to the market with a significant reduction in the cost of rust paint, enhance the anti-corrosion properties.

Studies on surface morphology and electrical conductivity of PEDOT:PSS thin films in presence of gold nanoparticles

NASA Astrophysics Data System (ADS)

Bhowal, Ashim Chandra; Kundu, Sarathi

2018-04-01

PEDOT:PSS is a water soluble conducting polymer consists of positively charged PEDOT and negatively charged PSS. However, this polymer suffers low conductivity problem which restrict its use. In this paper, electrical conductivity of PEDOT:PSS thin films is improved by using charged gold nanoparticles. The nanoparticles used are synthesized using lysozyme protein. The nanoparticles coated with lysozyme protein possess positive zeta potential. In the presence of gold nanoparticles due to electrostatic interaction between positively charged nanoparticles and negatively charged PSS chains, modification takes place in the surface morphology and electrical behaviors of PEDOT:PSS thin films. The changes in the polymer matrix conformations in the presence of nanoparticles are studied by Fourier transformed Infra-red (FTIR) spectroscopy, whereas the surface morphology of prepared thin films before and after interaction with nanoparticles is investigated through atomic force microscopy (AFM). Four probe method is used to measure the variation of electrical conductivity from I-V characteristics curves.

Immobilization of bacterial S-layer proteins from Caulobacter crescentus on iron oxide-based nanocomposite: synthesis and spectroscopic characterization of zincite-coated Fe₂O₃ nanoparticles.

PubMed

Habibi, Neda

2014-05-05

Zinc oxide was coated on Fe2O3 nanoparticles using sol-gel spin-coating. Caulobacter crescentus have a crystalline surface layer (S-layer), which consist of one protein or glycoprotein species. The immobilization of bacterial S-layers obtained from C. crescentus on zincite-coated nanoparticles of iron oxide was investigated. The SDS PAGE results of S-layers isolated from C. crescentus showed the weight of 50 KDa. Nanoparticles of the Fe2O3 and zinc oxide were synthesized by a sol-gel technique. Fe2O3 nanoparticles with an average size of 50 nm were successfully prepared by the proper deposition of zinc oxide onto iron oxide nanoparticles surface annealed at 450 °C. The samples were characterized by field-emission scanning electron microscope (FESEM), atomic force microscopy (AFM), powder X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR). Copyright © 2014 Elsevier B.V. All rights reserved.

Normal co-ordinate analysis of 1, 8-dibromooctane

NASA Astrophysics Data System (ADS)

Singh, Devinder; Jaggi, Neena; Singh, Nafa

2010-02-01

The organic compound 1,8-dibromooctane (1,8-DBO) exists in liquid phase at ambient temperatures and has versatile synthetic applications. In its liquid phase 1,8-DBO has been expected to exist in four most probable conformations, with all its carbon atoms in the same plane, having symmetries C 2h , C i , C 2 and C 1 . In the present study a detailed vibrational analysis in terms of assignment of Fourier transform infrared (FT-IR) and Raman bands of this molecule using normal co-ordinate calculations has been done. A systematic set of symmetry co-ordinates has been constructed for this molecule and normal co-ordinate analysis is carried out using the computer program MOLVIB. The force-field transferred from already studied lower chain bromo-alkanes is subjected to refinement so as to fit the observed infrared and Raman frequencies with those of calculated ones. The potential energy distribution (PED) has also been calculated for each mode of vibration of the molecule for the assumed conformations.

PEG and mPEG-anthracene induce DNA condensation and particle formation.

PubMed

Froehlich, E; Mandeville, J S; Arnold, D; Kreplak, L; Tajmir-Riahi, H A

2011-08-18

In this study, we investigated the binding of DNA with poly(ethylene glycol) (PEG) of different sizes and compositions such as PEG 3350, PEG 6000, and mPEG-anthracene in aqueous solution at physiological conditions. The effects of size and composition on DNA aggregation and condensation as well as conformation were determined using Fourier transform infrared (FTIR), UV-visible, CD, fluorescence spectroscopic methods and atomic force microscopy (AFM). Structural analysis showed moderate complex formation for PEG 3350 and PEG 6000 and weaker interaction for mPE-anthracene-DNA adducts with both hydrophilic and hydrophobic contacts. The order of ± stability of the complexes formed is K(PEG 6000) = 1.5 (±0.4) × 10(4) M(-1) > K(PEG 3350) = 7.9 (±1) × 10(3) M(-1) > K(m(PEG-anthracene))= 3.6 (±0.8) × 10(3) M(-1) with nearly 1 bound PEG molecule per DNA. No B-DNA conformational changes were observed, while DNA condensation and particle formation occurred at high PEG concentration.

Effects of ZnO Nanoparticle on the Gas Separation Performance of Polyurethane Mixed Matrix Membrane

PubMed Central

Soltani, Banafsheh

2017-01-01

Polyurethane (PU)-ZnO mixed matrix membranes (MMM) were fabricated and characterized for gas separation. A thermogravimetric analysis (TGA), a scanning electron microscope (SEM) test and an atomic-force microscopy (AFM) revealed that the physical properties and thermal stability of the membranes were improved through filler loading. Hydrogen Bonding Index, obtained from the Fourier transform infrared spectroscopy (FTIR), demonstrate that the degree of phase separation in PU-ZnO 0.5 wt % MMM was more than the neat PU, while in PU-ZnO 1.0 wt % MMM, the phase mixing had increased. Compared to the neat membrane, the CO2 permeability of the MMMs increased by 31% for PU-ZnO 0.5 wt % MMM and decreased by 34% for 1.0 wt % ZnO MMM. The CO2/CH4 and CO2/N2 selectivities of PU-ZnO 0.5 wt % were 18.75 and 64.75, respectively. PMID:28800109

Single-molecule force spectroscopy: optical tweezers, magnetic tweezers and atomic force microscopy

PubMed Central

Neuman, Keir C.; Nagy, Attila

2012-01-01

Single-molecule force spectroscopy has emerged as a powerful tool to investigate the forces and motions associated with biological molecules and enzymatic activity. The most common force spectroscopy techniques are optical tweezers, magnetic tweezers and atomic force microscopy. These techniques are described and illustrated with examples highlighting current capabilities and limitations. PMID:18511917

Spectroscopic (FT-IR, FT-Raman, FT-NMR and UV-Vis) investigation on benzil dioxime using quantum computational methods

NASA Astrophysics Data System (ADS)

Bakkiyaraj, D.; Periandy, S.; Xavier, S.

2016-03-01

The spectral analysis of benzil dioxime is carried out using the FTIR, FT Raman, FT NMR and UV-Vis spectra of the compound with the help of quantum computations by density functional theories. The FT-IR (4000 - 400 cm-1) and FT-Raman (4000-100 cm-1) spectra are recorded in solid phase, the 1H and 13C NMR spectra in DMSO phase and the UV spectrum (200-400 nm) in ethanol phase. The different conformers of the compound and their minimum energies are studied by potential energy surface scan, using semi-empirical method PM6. The computed wavenumbers from different methods are scaled so as to agree with the experimental values and the scaling factors are reported. All the fundamental modes have been assigned based on the potential energy distribution (PED) values and the structure the molecule is analyzed interms of parameters like bond length, bond angle and dihedral angles predicted byB3LYP and CAM-B3LYP methods with cc-pVDZ basis sets. The values of dipole moment (μ), polarizability (α) and hyperpolarizability (β) of the molecule are reported, using which the non -linear optical property of the molecule is discussed. The HOMO-LUMO mappings are reported which reveals the different charge transfer possibilities within the molecule. The isotropic chemical shifts predicted for 1H and 13C atoms using gauge invariant atomic orbital (GIAO) theory show good agreement with experimental shifts and the same is discussed in comparison with atomic charges, predicted by Mullikan and APT charge analysis. NBO analysis is carried out to picture the probable electronic transitions in the molecule.

Optimization of classical nonpolarizable force fields for OH(-) and H3O(+).

PubMed

Bonthuis, Douwe Jan; Mamatkulov, Shavkat I; Netz, Roland R

2016-03-14

We optimize force fields for H3O(+) and OH(-) that reproduce the experimental solvation free energies and the activities of H3O(+) Cl(-) and Na(+) OH(-) solutions up to concentrations of 1.5 mol/l. The force fields are optimized with respect to the partial charge on the hydrogen atoms and the Lennard-Jones parameters of the oxygen atoms. Remarkably, the partial charge on the hydrogen atom of the optimized H3O(+) force field is 0.8 ± 0.1|e|--significantly higher than the value typically used for nonpolarizable water models and H3O(+) force fields. In contrast, the optimal partial charge on the hydrogen atom of OH(-) turns out to be zero. Standard combination rules can be used for H3O(+) Cl(-) solutions, while for Na(+) OH(-) solutions, we need to significantly increase the effective anion-cation Lennard-Jones radius. While highlighting the importance of intramolecular electrostatics, our results show that it is possible to generate thermodynamically consistent force fields without using atomic polarizability.

[Studies on organic protective coatings for anti-atomic oxygen effects by spectrum analysis].

PubMed

Zhang, Lei

2004-11-01

This paper describes organic protective coatings on space material for anti-AO effects and the experiments to assess properties of the coatings. Organic protection was analyzed after exposures to ground state fast atomic (AO) radiation in the atomic oxygen beam facility for ground simulation experiments. The tests results have been analyzed with advanced FTIR, XPS and SEM. The test indicated that epoxy, alkyd and urethane organic coatings were highly reactive to AO with a strong degradation and changed in morphology of the surface layer. It is evident that siloxane coatings have excellent properties for anti-AO effects. The erosion product has SiO2 left on the surface, thus providing protection from further attack by the energetic oxygen atoms.

Graphene nanosheets preparation using magnetic nanoparticle assisted liquid phase exfoliation of graphite: The coupled effect of ultrasound and wedging nanoparticles.

PubMed

Hadi, Alireza; Zahirifar, Jafar; Karimi-Sabet, Javad; Dastbaz, Abolfazl

2018-06-01

This study aims to investigate a novel technique to improve the yield of liquid phase exfoliation of graphite to graphene sheets. The method is based on the utilization of magnetic Fe 3 O 4 nanoparticles as "particle wedge" to facilitate delamination of graphitic layers. Strong shear forces resulted from the collision of Fe 3 O 4 particles with graphite particles, and intense ultrasonic waves lead to enhanced exfoliation of graphite. High quality of graphene sheets along with the ease of Fe 3 O 4 particle separation from graphene solution which arises from the magnetic nature of Fe 3 O 4 nanoparticles are the unique features of this approach. Initial graphite flakes and produced graphene sheets were characterized by various methods including field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Raman spectroscopy, atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Zeta potential analysis. Moreover, the effect of process factors comprising initial graphite concentration, Fe 3 O 4 nanoparticles concentration, sonication time, and sonication power were investigated. Results revealed that graphene preparation yield and the number of layers could be manipulated by the presence of magnetic nanoparticles. Copyright © 2018 Elsevier B.V. All rights reserved.

A series of binuclear lanthanide(III) complexes: Crystallography, antimicrobial activity and thermochemistry properties studies

NASA Astrophysics Data System (ADS)

Zhang, Ying-Ying; Ren, Ning; Xu, Su-Ling; Zhang, Jian-Jun; Zhang, Da-Hai

2015-02-01

A series of novel lanthanide complexes with the general formula [Ln(3,4-DClBA)3phen]2 (Ln = Ho(1), Nd(2), Sm(3), Dy(4), Eu(5), Tb(6), Yb(7) and Er(8), 3,4-DClBA = 3,4-dichlorobenzoate, phen = 1,10-phenanthroline) were prepared at room temperature and characterized. The crystal structures of complexes 1-8 have been determined by single crystal X-ray diffraction. These complexes are isomorphous and lanthanide ions are all eight-coordinated to oxygen atoms and nitrogen atoms with distorted square-antiprism geometry. The thermal decomposition mechanism and TG-FTIR spectra of gaseous products of thermal decomposition processes for complexes 1-8 were acquired through TG/DSC-FTIR system. The heat capacities of complexes 1-8 were measured using DSC technology and fitted to a polynomial equation by the least-squares method. Complexes 3-6 display characteristic lanthanide emission bands in the visible region. Meanwhile, these complexes exhibit in good antimicrobial activity against Candida albicans, Escherichia coli, and Staphylococcus aureu.

Synthesis and characterization of core-shell gold nanoparticles with poly(vinyl pyrrolidone) from a new precursor salt

NASA Astrophysics Data System (ADS)

Behera, M.; Ram, S.

2013-02-01

In this article, we report a facile one-step chemical synthesis of gold (Au) nanoparticles (GNPs) from a new precursor salt i.e., gold hydroxide in the presence of poly(vinyl pyrrolidone) (PVP) polymer. The non-aqueous dispersion of GNPs was comprehensively characterized by UV-Visible, FTIR, zeta potential, and transmission electron microscope (TEM). A strong surface plasmon resonance band at 529 nm in the UV-Visible spectrum confirms the formation of GNPs in the Au colloid. The FTIR spectroscopic results showed that PVP molecules get chemisorbed onto the surface of GNP via O-atom of carbonyl group. A negative zeta potential of (-)16 mV reveals accumulation of nonbonding electrons of O-atom of carbonyl group of PVP molecules on the nanosurface of GNP. TEM images demonstrate a core-shell nanostructure with an Au-crystalline core covered by a thin amorphous PVP-shell. PVP-capped GNPs could be a potential candidate for bio-sensing, catalysis, and other applications.

Spectroscopic, Homo-Lumo and NLO studies of tetra fluoro phthalate doped Coumarin crystals using DFT method

NASA Astrophysics Data System (ADS)

Latha, B.; Kumaresan, P.; Nithiyanantham, S.; Sampathkumar, K.

2017-08-01

In the present examination, a methodical study has been done on the development of unadulterated and Coumarin doped Tetrafluoro Phthalate precious stones. Powder X-beam diffraction studies were done and the cross section parameters were computed by minimum square technique in pure and doped crystals. FT-IR, UV-Vis, Thermal, Micro-hardness and Dielectric studies were additionally done for the pure and doped crystals. The tentatively watched FT-IR and FT-Raman groups were allotted to various ordinary methods of the atom. The steadiness and charge delocalization of the particle were likewise concentrations were done by characteristic security orbital (NBO) examination. The HOMO-LUMO energies depict the charge exchange happens inside the particle. Atomic electrostatic potential has been broken down the electronic properties such as excitation energies, oscillator quality, wavelengths and HOMO-LUMO energies were acquired by time-subordinate DFT (TD-DFT) approach. The SHG of pure and doped TFP stones were examined through Nd:YAG Q-exchanged laser.

Spectroscopic, semiempirical studies and antibacterial activity of new urethane derivatives of natural polyether antibiotic - Monensin A

NASA Astrophysics Data System (ADS)

Huczyński, Adam; Stefańska, Joanna; Piśmienny, Mieszko; Brzezinski, Bogumil

2013-02-01

A series of new Monensin A dimers linked by diurethane moiety were synthesised and their molecular structures were studied using ESI-MS, FT-IR, 1H and 13C NMR and PM5 methods. The results showed that the compounds form a pseudo-cyclic structure stabilized by three intramolecular hydrogen bonds and the sodium cation was coordinated by five oxygen atoms of polyether skeleton of Monensin moiety. The NMR and FT-IR data of complexes of Monensin urethane sodium salts demonstrated that within the pseudo-cyclic structure the carbonyl oxygen atom of the urethane group did not coordinate the sodium cation. Monensin urethanes were tested in vitro for the activity against Gram-positive and Gram-negative bacteria and fungi as well as against a series of clinical isolates of Staphylococcus: methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S. aureus (MSSA). The most active compound against MRSA and MSSA was 1,4-phenylene diurethane of Monensin with MIC 10.4-41.4 μmol/L).

Hierarchical atom type definitions and extensible all-atom force fields.

PubMed

Jin, Zhao; Yang, Chunwei; Cao, Fenglei; Li, Feng; Jing, Zhifeng; Chen, Long; Shen, Zhe; Xin, Liang; Tong, Sijia; Sun, Huai

2016-03-15

The extensibility of force field is a key to solve the missing parameter problem commonly found in force field applications. The extensibility of conventional force fields is traditionally managed in the parameterization procedure, which becomes impractical as the coverage of the force field increases above a threshold. A hierarchical atom-type definition (HAD) scheme is proposed to make extensible atom type definitions, which ensures that the force field developed based on the definitions are extensible. To demonstrate how HAD works and to prepare a foundation for future developments, two general force fields based on AMBER and DFF functional forms are parameterized for common organic molecules. The force field parameters are derived from the same set of quantum mechanical data and experimental liquid data using an automated parameterization tool, and validated by calculating molecular and liquid properties. The hydration free energies are calculated successfully by introducing a polarization scaling factor to the dispersion term between the solvent and solute molecules. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Subatomic-scale force vector mapping above a Ge(001) dimer using bimodal atomic force microscopy

NASA Astrophysics Data System (ADS)

Naitoh, Yoshitaka; Turanský, Robert; Brndiar, Ján; Li, Yan Jun; Štich, Ivan; Sugawara, Yasuhiro

2017-07-01

Probing physical quantities on the nanoscale that have directionality, such as magnetic moments, electric dipoles, or the force response of a surface, is essential for characterizing functionalized materials for nanotechnological device applications. Currently, such physical quantities are usually experimentally obtained as scalars. To investigate the physical properties of a surface on the nanoscale in depth, these properties must be measured as vectors. Here we demonstrate a three-force-component detection method, based on multi-frequency atomic force microscopy on the subatomic scale and apply it to a Ge(001)-c(4 × 2) surface. We probed the surface-normal and surface-parallel force components above the surface and their direction-dependent anisotropy and expressed them as a three-dimensional force vector distribution. Access to the atomic-scale force distribution on the surface will enable better understanding of nanoscale surface morphologies, chemical composition and reactions, probing nanostructures via atomic or molecular manipulation, and provide insights into the behaviour of nano-machines on substrates.

Van der Waals interactions and the limits of isolated atom models at interfaces

PubMed Central

Kawai, Shigeki; Foster, Adam S.; Björkman, Torbjörn; Nowakowska, Sylwia; Björk, Jonas; Canova, Filippo Federici; Gade, Lutz H.; Jung, Thomas A.; Meyer, Ernst

2016-01-01

Van der Waals forces are among the weakest, yet most decisive interactions governing condensation and aggregation processes and the phase behaviour of atomic and molecular matter. Understanding the resulting structural motifs and patterns has become increasingly important in studies of the nanoscale regime. Here we measure the paradigmatic van der Waals interactions represented by the noble gas atom pairs Ar–Xe, Kr–Xe and Xe–Xe with a Xe-functionalized tip of an atomic force microscope at low temperature. Individual rare gas atoms were fixed at node sites of a surface-confined two-dimensional metal–organic framework. We found that the magnitude of the measured force increased with the atomic radius, yet detailed simulation by density functional theory revealed that the adsorption induced charge redistribution strengthened the van der Waals forces by a factor of up to two, thus demonstrating the limits of a purely atomic description of the interaction in these representative systems. PMID:27174162

Taking Nanomedicine Teaching into Practice with Atomic Force Microscopy and Force Spectroscopy

ERIC Educational Resources Information Center

Carvalho, Filomena A.; Freitas, Teresa; Santos, Nuno C.

2015-01-01

Atomic force microscopy (AFM) is a useful and powerful tool to study molecular interactions applied to nanomedicine. The aim of the present study was to implement a hands-on atomic AFM course for graduated biosciences and medical students. The course comprises two distinct practical sessions, where students get in touch with the use of an atomic…

Synchrotron macro ATR-FTIR microspectroscopic analysis of silica nanoparticle-embedded polyester coated steel surfaces subjected to prolonged UV and humidity exposure

PubMed Central

Vongsvivut, Jitraporn; Truong, Vi Khanh; Al Kobaisi, Mohammad; Maclaughlin, Shane; Tobin, Mark J.; Crawford, Russell J.

2017-01-01

Surface modification of polymers and paints is a popular and effective way to enhance the properties of these materials. This can be achieved by introducing a thin coating that preserves the bulk properties of the material, while protecting it from environmental exposure. Suitable materials for such coating technologies are inorganic oxides, such as alumina, titania and silica; however, the fate of these materials during long-term environmental exposure is an open question. In this study, polymer coatings that had been enhanced with the addition of silica nanoparticles (SiO2NPs) and subsequently subjected to environmental exposure, were characterized both before and after the exposure to determine any structural changes resulting from the exposure. High-resolution synchrotron macro ATR-FTIR microspectroscopy and surface topographic techniques, including optical profilometry and atomic force microscopy (AFM), were used to determine the long-term effect of the environment on these dual protection layers after 3 years of exposure to tropical and sub-tropical climates in Singapore and Queensland (Australia). Principal component analysis (PCA) based on the synchrotron macro ATR-FTIR spectral data revealed that, for the 9% (w/w) SiO2NP/polymer coating, a clear discrimination was observed between the control group (no environmental exposure) and those samples subjected to three years of environmental exposure in both Singapore and Queensland. The PCA loading plots indicated that, over the three year exposure period, a major change occurred in the triazine ring vibration in the melamine resins. This can be attributed to the triazine ring being very sensitive to hydrolysis under the high humidity conditions in tropical/sub-tropical environments. This work provides the first direct molecular evidence, acquired using a high-resolution mapping technique, of the climate-induced chemical evolution of a polyester coating. The observed changes in the surface topography of the coating are consistent with the changes in chemical composition. PMID:29253012

Synchrotron macro ATR-FTIR microspectroscopic analysis of silica nanoparticle-embedded polyester coated steel surfaces subjected to prolonged UV and humidity exposure.

PubMed

Vongsvivut, Jitraporn; Truong, Vi Khanh; Al Kobaisi, Mohammad; Maclaughlin, Shane; Tobin, Mark J; Crawford, Russell J; Ivanova, Elena P

2017-01-01

Surface modification of polymers and paints is a popular and effective way to enhance the properties of these materials. This can be achieved by introducing a thin coating that preserves the bulk properties of the material, while protecting it from environmental exposure. Suitable materials for such coating technologies are inorganic oxides, such as alumina, titania and silica; however, the fate of these materials during long-term environmental exposure is an open question. In this study, polymer coatings that had been enhanced with the addition of silica nanoparticles (SiO2NPs) and subsequently subjected to environmental exposure, were characterized both before and after the exposure to determine any structural changes resulting from the exposure. High-resolution synchrotron macro ATR-FTIR microspectroscopy and surface topographic techniques, including optical profilometry and atomic force microscopy (AFM), were used to determine the long-term effect of the environment on these dual protection layers after 3 years of exposure to tropical and sub-tropical climates in Singapore and Queensland (Australia). Principal component analysis (PCA) based on the synchrotron macro ATR-FTIR spectral data revealed that, for the 9% (w/w) SiO2NP/polymer coating, a clear discrimination was observed between the control group (no environmental exposure) and those samples subjected to three years of environmental exposure in both Singapore and Queensland. The PCA loading plots indicated that, over the three year exposure period, a major change occurred in the triazine ring vibration in the melamine resins. This can be attributed to the triazine ring being very sensitive to hydrolysis under the high humidity conditions in tropical/sub-tropical environments. This work provides the first direct molecular evidence, acquired using a high-resolution mapping technique, of the climate-induced chemical evolution of a polyester coating. The observed changes in the surface topography of the coating are consistent with the changes in chemical composition.

Compositional and surface characterization of HULIS by UV-Vis, FTIR, NMR and XPS: Wintertime study in Northern India

NASA Astrophysics Data System (ADS)

Kumar, Varun; Goel, Anubha; Rajput, Prashant

2017-09-01

This study (first attempt) characterizes HULIS (Humic Like Substances) in wintertime aerosols (n = 12 during day and nighttime each) from Indo-Gangetic Plain (IGP, at Kanpur) by using various state-of-the art techniques such as UV-VIS, FTIR, 1H NMR and XPS. Based on UV-Vis analysis the absorption coefficient at 365 nm (babs-365) of HULIS was found to average at 13.6 and 28.8 Mm-1 during day and nighttime, respectively. Relatively high babs-365 of HULIS during the nighttime is attributed to influence of fog-processing. However, the power fit of UV-Vis spectrum provided near similar AAE (absorption Angstrom exponent) value of HULIS centering at 4.9 ± 1.4 and 5.1 ± 1.3 during daytime and nighttime, respectively. FTIR spectra and its double derivative revealed the presence of various functional groups viz. alcohols, ketones aldehydes, carboxylic acids as well as unsaturated and saturated carbon bonds. 1H NMR spectroscopy was applied to quantify relative percentage of various types of hydrogen atoms contained in HULIS, whereas XPS technique provided information on surface composition and oxidation states of various elements present. A significantly high abundance of H‒C‒O group has been observed in HULIS (based on 1H NMR); 41.4± 2.7% and 30.9± 2.4% in day and nighttime, respectively. However, aromatic protons (Ar-H) were higher in nighttime samples (19.3± 1.8%) as compared to that in daytime samples (7.5 ± 1.9). XPS studies revealed presence of various species on the surface of HULIS samples. Carbon existed in 7 different chemical states while total nitrogen and sulfur exhibited 3 and 2 different oxidation states (respectively) on the surface of HULIS. This study reports structural information and absorption properties of HULIS which has implications to their role as cloud condensation nuclei and atmospheric direct radiative forcing.

Densification and Devitrification of Fused Silica Induced by Ballistic Impact: A Computational Investigation

DTIC Science & Technology

2015-03-25

lime glass, the polyhedron -center atoms are all silicon and each silicon atom is surrounded by four oxygen atoms (while each oxygen atom is connected...of metallic force-field functions (in the pure metallic environment) within the force-field function database used in the present work. Consequently

Quantitative force measurements in liquid using frequency modulation atomic force microscopy

NASA Astrophysics Data System (ADS)

Uchihashi, Takayuki; Higgins, Michael J.; Yasuda, Satoshi; Jarvis, Suzanne P.; Akita, Seiji; Nakayama, Yoshikazu; Sader, John E.

2004-10-01

The measurement of short-range forces with the atomic force microscope (AFM) typically requires implementation of dynamic techniques to maintain sensitivity and stability. While frequency modulation atomic force microscopy (FM-AFM) is used widely for high-resolution imaging and quantitative force measurements in vacuum, quantitative force measurements using FM-AFM in liquids have proven elusive. Here we demonstrate that the formalism derived for operation in vacuum can also be used in liquids, provided certain modifications are implemented. To facilitate comparison with previous measurements taken using surface forces apparatus, we choose a model system (octamethylcyclotetrasiloxane) that is known to exhibit short-ranged structural ordering when confined between two surfaces. Force measurements obtained are found to be in excellent agreement with previously reported results. This study therefore establishes FM-AFM as a powerful tool for the quantitative measurement of forces in liquid.

Energy profile, spectroscopic (FT-IR, FT-Raman and FT-NMR) and DFT studies of 4-bromoisophthalic acid

NASA Astrophysics Data System (ADS)

Arjunan, V.; Thirunarayanan, S.; Mohan, S.

2018-04-01

The stable conformer of 4-bromoisophthalic acid (BIPA) has been identified by potential energy profile analysis. All the structural parameters of 4-bromoisophthalic acid are determined by B3LYP method with 6-311++G**, 6-31G** and cc-pVTZ basis sets. The fundamental vibrations are analysed with the use of FT-IR (4000-400 cm-1) and FT-Raman (4000-100 cm-1) spectra. The harmonic vibrational frequencies are theoretically calculated and compared with experimental FTIR and FT-Raman frequencies. The 1H and 13C NMR spectra have been analysed and compared with theoretical 1H and 13C NMR chemical shifts calculated by gauge independent atomic orbital (GIAO) method. The electronic properties, such as HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) energies are determined by B3LYP/cc-pVTZ method. The electron density distribution and site of chemical reactivity of BIPA molecule have been obtained by mapping electron density isosurface with molecular electrostatic potential (MEP). Stability of the molecules arising from hyperconjugative interactions, charge delocalizations have been analysed by using natural bond orbital (NBO) analysis. The thermodynamic properties and atomic natural charges of the compound are analysed and the reactive sites of the molecule are identified. The global and local reactivity descriptors are evaluated to analyse the chemical reactivity and site selectivity of molecule through Fukui functions.

Mechanistic study of atomic layer deposition of Al{sub x}Si{sub y}O thin film via in-situ FTIR spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cho, Jea; Kim, Taeseung; Seegmiller, Trevor

2015-09-15

A study of surface reaction mechanism on atomic layer deposition (ALD) of aluminum silicate (Al{sub x}Si{sub y}O) was conducted with trimethylaluminum (TMA) and tetraethoxysilane (TEOS) as precursors and H{sub 2}O as the oxidant. In-situ Fourier transform infrared spectroscopy (FTIR) was utilized to elucidate the underlying surface mechanism that enables the deposition of Al{sub x}Si{sub y}O by ALD. In-situ FTIR study revealed that ineffective hydroxylation of the surface ethoxy (–OCH{sub 2}CH{sub 3}) groups prohibits ALD of SiO{sub 2} by TEOS/H{sub 2}O. In contrast, effective desorption of the surface ethoxy group was observed in TEOS/H{sub 2}O/TMA/H{sub 2}O chemistry. The presence of Al-OH*more » group in vicinity of partially hydroxylated ethoxy (–OCH{sub 2}CH{sub 3}) group was found to propagate disproportionation reaction, which results in ALD of Al{sub x}Si{sub y}O. The maximum thickness from incorporation of SiO{sub x} from alternating exposures of TEOS/H{sub 2}O chemistry in Al{sub x}Si{sub y}O was found to be ∼2 Å, confirmed by high resolution transmission electron microscopy measurements.« less

Line-averaging measurement methods to estimate the gap in the CO2 balance closure - possibilities, challenges, and uncertainties

NASA Astrophysics Data System (ADS)

Ziemann, Astrid; Starke, Manuela; Schütze, Claudia

2017-11-01

An imbalance of surface energy fluxes using the eddy covariance (EC) method is observed in global measurement networks although all necessary corrections and conversions are applied to the raw data. Mainly during nighttime, advection can occur, resulting in a closing gap that consequently should also affect the CO2 balances. There is the crucial need for representative concentration and wind data to measure advective fluxes. Ground-based remote sensing techniques are an ideal tool as they provide the spatially representative CO2 concentration together with wind components within the same voxel structure. For this purpose, the presented SQuAd (Spatially resolved Quantification of the Advection influence on the balance closure of greenhouse gases) approach applies an integrated method combination of acoustic and optical remote sensing. The innovative combination of acoustic travel-time tomography (A-TOM) and open-path Fourier-transform infrared spectroscopy (OP-FTIR) will enable an upscaling and enhancement of EC measurements. OP-FTIR instrumentation offers the significant advantage of real-time simultaneous measurements of line-averaged concentrations for CO2 and other greenhouse gases (GHGs). A-TOM is a scalable method to remotely resolve 3-D wind and temperature fields. The paper will give an overview about the proposed SQuAd approach and first results of experimental tests at the FLUXNET site Grillenburg in Germany. Preliminary results of the comprehensive experiments reveal a mean nighttime horizontal advection of CO2 of about 10 µmol m-2 s-1 estimated by the spatially integrating and representative SQuAd method. Additionally, uncertainties in determining CO2 concentrations using passive OP-FTIR and wind speed applying A-TOM are systematically quantified. The maximum uncertainty for CO2 concentration was estimated due to environmental parameters, instrumental characteristics, and retrieval procedure with a total amount of approximately 30 % for a single measurement. Instantaneous wind components can be derived with a maximum uncertainty of 0.3 m s-1 depending on sampling, signal analysis, and environmental influences on sound propagation. Averaging over a period of 30 min, the standard error of the mean values can be decreased by a factor of at least 0.5 for OP-FTIR and 0.1 for A-TOM depending on the required spatial resolution. The presented validation of the joint application of the two independent, nonintrusive methods is in the focus of attention concerning their ability to quantify advective fluxes.

Direct Writing of Graphene-based Nanoelectronics via Atomic Force Microscopy

DTIC Science & Technology

2012-05-07

To) 07-05-2012 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Direct Writing of Graphene -based Nanoelectronics via Atomic Force Microscopy 5b. GRANT...ABSTRACT This project employs direct writing with an atomic force microscope (AFM) to fabricate simple graphene -based electronic components like resistors...and transistors at nanometer-length scales. The goal is to explore their electrical properties for graphene -based electronics. Conducting

Radical Chemistry and Charge Manipulation with an Atomic Force Microscope

NASA Astrophysics Data System (ADS)

Gross, Leo

The fuctionalization of tips by atomic manipulation dramatically increased the resolution of atomic force microscopy (AFM). The combination of high-resolution AFM with atomic manipulation now offers the unprecedented possibility to custom-design individual molecules by making and breaking bonds with the tip of the microscope and directly characterizing the products on the atomic scale. We recently applied this technique to generate and study reaction intermediates and to investigate chemical reactions trigged by atomic manipulation. We formed diradicals by dissociating halogen atoms and then reversibly triggered ring-opening and -closing reactions via atomic manipulation, allowing us to switch and control the molecule's reactivity, magnetic and optical properties. Additional information about charge states and charge distributions can be obtained by Kelvin probe force spectroscopy. On multilayer insulating films we investigated single-electron attachment, detachment and transfer between individual molecules. EU ERC AMSEL (682144), EU project PAMS (610446).

MATCH: An Atom- Typing Toolset for Molecular Mechanics Force Fields

PubMed Central

Yesselman, Joseph D.; Price, Daniel J.; Knight, Jennifer L.; Brooks, Charles L.

2011-01-01

We introduce a toolset of program libraries collectively titled MATCH (Multipurpose Atom-Typer for CHARMM) for the automated assignment of atom types and force field parameters for molecular mechanics simulation of organic molecules. The toolset includes utilities for the conversion from multiple chemical structure file formats into a molecular graph. A general chemical pattern-matching engine using this graph has been implemented whereby assignment of molecular mechanics atom types, charges and force field parameters is achieved by comparison against a customizable list of chemical fragments. While initially designed to complement the CHARMM simulation package and force fields by generating the necessary input topology and atom-type data files, MATCH can be expanded to any force field and program, and has core functionality that makes it extendable to other applications such as fragment-based property prediction. In the present work, we demonstrate the accurate construction of atomic parameters of molecules within each force field included in CHARMM36 through exhaustive cross validation studies illustrating that bond increment rules derived from one force field can be transferred to another. In addition, using leave-one-out substitution it is shown that it is also possible to substitute missing intra and intermolecular parameters with ones included in a force field to complete the parameterization of novel molecules. Finally, to demonstrate the robustness of MATCH and the coverage of chemical space offered by the recent CHARMM CGENFF force field (Vanommeslaeghe, et al., JCC., 2010, 31, 671–690), one million molecules from the PubChem database of small molecules are typed, parameterized and minimized. PMID:22042689

Molecular structure, vibrational spectral assignments (FT-IR and FT-RAMAN), NMR, NBO, HOMO-LUMO and NLO properties of O-methoxybenzaldehyde based on DFT calculations

NASA Astrophysics Data System (ADS)

Vennila, P.; Govindaraju, M.; Venkatesh, G.; Kamal, C.

2016-05-01

Fourier transform - Infra red (FT-IR) and Fourier transform - Raman (FT-Raman) spectroscopic techniques have been carried out to analyze O-methoxy benzaldehyde (OMB) molecule. The fundamental vibrational frequencies and intensity of vibrational bands were evaluated using density functional theory (DFT). The vibrational analysis of stable isomer of OMB has been carried out by FT-IR and FT-Raman in combination with theoretical method simultaneously. The first-order hyperpolarizability and the anisotropy polarizability invariant were computed by DFT method. The atomic charges, hardness, softness, ionization potential, electronegativity, HOMO-LUMO energies, and electrophilicity index have been calculated. The 13C and 1H Nuclear magnetic resonance (NMR) have also been obtained by GIAO method. Molecular electronic potential (MEP) has been calculated by the DFT calculation method. Electronic excitation energies, oscillator strength and excited states characteristics were computed by the closed-shell singlet calculation method.

Experimental and theoretical studies of the structure of tellurate-borate glasses network.

PubMed

Rada, Simona; Culea, Eugen; Neumann, Manfred

2010-08-01

The structural properties of the xTeO(2) x (1-x)B(2)O(3) glasses (x = 0.6; 0.7) were investigated by FT-IR spectroscopy. From the analysis of the FTIR spectra, it is reasonable to assume that by the increasing of boron ions content, the tetrahedral [BO(4)] units are gradually replaced by the trigonal [BO(3)] units. The increase in the number of non-bridging oxygen atoms would decrease the connectivity of the glass network and will yield the depolymerization of the borate chains. The molecular structure and vibrational frequencies of the proposed structural models have been studied by exploring the density functional theory (DFT) calculations. The FTIR spectra of the xTeO(2) x (1-x)B(2)O(3) vitreous systems were compared with the calculated spectrum. This procedure allowed us to assign most of the observed IR bands.

Quantum Chemical Topology: Knowledgeable atoms in peptides

NASA Astrophysics Data System (ADS)

Popelier, Paul L. A.

2012-06-01

The need to improve atomistic biomolecular force fields remains acute. Fortunately, the abundance of contemporary computing power enables an overhaul of the architecture of current force fields, which typically base their electrostatics on fixed atomic partial charges. We discuss the principles behind the electrostatics of a more realistic force field under construction, called QCTFF. At the heart of QCTFF lies the so-called topological atom, which is a malleable box, whose shape and electrostatics changes in response to a changing environment. This response is captured by a machine learning method called Kriging. Kriging directly predicts each multipole moment of a given atom (i.e. the output) from the coordinates of the nuclei surrounding this atom (i.e. the input). This procedure yields accurate interatomic electrostatic energies, which form the basis for future-proof progress in force field design.

Atomic force microscopy as a tool for the investigation of living cells.

PubMed

Morkvėnaitė-Vilkončienė, Inga; Ramanavičienė, Almira; Ramanavičius, Arūnas

2013-01-01

Atomic force microscopy is a valuable and useful tool for the imaging and investigation of living cells in their natural environment at high resolution. Procedures applied to living cell preparation before measurements should be adapted individually for different kinds of cells and for the desired measurement technique. Different ways of cell immobilization, such as chemical fixation on the surface, entrapment in the pores of a membrane, or growing them directly on glass cover slips or on plastic substrates, result in the distortion or appearance of artifacts in atomic force microscopy images. Cell fixation allows the multiple use of samples and storage for a prolonged period; it also increases the resolution of imaging. Different atomic force microscopy modes are used for the imaging and analysis of living cells. The contact mode is the best for cell imaging because of high resolution, but it is usually based on the following: (i) image formation at low interaction force, (ii) low scanning speed, and (iii) usage of "soft," low resolution cantilevers. The tapping mode allows a cell to behave like a very solid material, and destructive shear forces are minimized, but imaging in liquid is difficult. The force spectroscopy mode is used for measuring the mechanical properties of cells; however, obtained results strongly depend on the cell fixation method. In this paper, the application of 3 atomic force microscopy modes including (i) contact, (ii) tapping, and (iii) force spectroscopy for the investigation of cells is described. The possibilities of cell preparation for the measurements, imaging, and determination of mechanical properties of cells are provided. The applicability of atomic force microscopy to diagnostics and other biomedical purposes is discussed.

Structural study of Cu(II) complexes with benzo[b]furancarboxylic acids

NASA Astrophysics Data System (ADS)

Kalinowska, Diana; Klepka, Marcin T.; Wolska, Anna; Drzewiecka-Antonik, Aleksandra; Ostrowska, Kinga; Struga, Marta

2017-11-01

Four Cu(II) complexes with 2- and 3-benzo[b]furancarboxylic acids have been synthesized and characterized using combination of two spectroscopic techniques. These techniques were: (i) FTIR and (ii) XAFS. FTIR analysis confirmed that complexes were formed and gave insight into identification of possible coordinating groups to the metallic center. XANES analysis indicated that the oxidation state of Cu is +2. EXAFS analysis allowed to identify that the first coordination sphere is formed by 4-5 oxygen atoms with the Cu-O distances around 2 Å. Combining these techniques it was possible to structurally describe novel Cu(II) complexes with benzo[b]furancarboxylic acids.

Elemental Identification by Combining Atomic Force Microscopy and Kelvin Probe Force Microscopy.

PubMed

Schulz, Fabian; Ritala, Juha; Krejčí, Ondrej; Seitsonen, Ari Paavo; Foster, Adam S; Liljeroth, Peter

2018-06-01

There are currently no experimental techniques that combine atomic-resolution imaging with elemental sensitivity and chemical fingerprinting on single molecules. The advent of using molecular-modified tips in noncontact atomic force microscopy (nc-AFM) has made it possible to image (planar) molecules with atomic resolution. However, the mechanisms responsible for elemental contrast with passivated tips are not fully understood. Here, we investigate elemental contrast by carrying out both nc-AFM and Kelvin probe force microscopy (KPFM) experiments on epitaxial monolayer hexagonal boron nitride (hBN) on Ir(111). The hBN overlayer is inert, and the in-plane bonds connecting nearest-neighbor boron and nitrogen atoms possess strong covalent character and a bond length of only ∼1.45 Å. Nevertheless, constant-height maps of both the frequency shift Δ f and the local contact potential difference exhibit striking sublattice asymmetry. We match the different atomic sites with the observed contrast by comparison with nc-AFM image simulations based on the density functional theory optimized hBN/Ir(111) geometry, which yields detailed information on the origin of the atomic-scale contrast.

Interpretation of frequency modulation atomic force microscopy in terms of fractional calculus

NASA Astrophysics Data System (ADS)

Sader, John E.; Jarvis, Suzanne P.

2004-07-01

It is widely recognized that small amplitude frequency modulation atomic force microscopy probes the derivative of the interaction force between tip and sample. For large amplitudes, however, such a physical connection is currently lacking, although it has been observed that the frequency shift presents a quantity intermediate to the interaction force and energy for certain force laws. Here we prove that these observations are a universal property of large amplitude frequency modulation atomic force microscopy, by establishing that the frequency shift is proportional to the half-fractional integral of the force, regardless of the force law. This finding indicates that frequency modulation atomic force microscopy can be interpreted as a fractional differential operator, where the order of the derivative/integral is dictated by the oscillation amplitude. We also establish that the measured frequency shift varies systematically from a probe of the force gradient for small oscillation amplitudes, through to the measurement of a quantity intermediate to the force and energy (the half-fractional integral of the force) for large oscillation amplitudes. This has significant implications to measurement sensitivity, since integrating the force will smooth its behavior, while differentiating it will enhance variations. This highlights the importance in choice of oscillation amplitude when wishing to optimize the sensitivity of force spectroscopy measurements to short-range interactions and consequently imaging with the highest possible resolution.

Evidence for non-conservative current-induced forces in the breaking of Au and Pt atomic chains

PubMed Central

Sabater, Carlos; Untiedt, Carlos

2015-01-01

Summary This experimental work aims at probing current-induced forces at the atomic scale. Specifically it addresses predictions in recent work regarding the appearance of run-away modes as a result of a combined effect of the non-conservative wind force and a ‘Berry force’. The systems we consider here are atomic chains of Au and Pt atoms, for which we investigate the distribution of break down voltage values. We observe two distinct modes of breaking for Au atomic chains. The breaking at high voltage appears to behave as expected for regular break down by thermal excitation due to Joule heating. However, there is a low-voltage breaking mode that has characteristics expected for the mechanism of current-induced forces. Although a full comparison would require more detailed information on the individual atomic configurations, the systems we consider are very similar to those considered in recent model calculations and the comparison between experiment and theory is very encouraging for the interpretation we propose. PMID:26734525

Polarizable atomic multipole-based force field for DOPC and POPE membrane lipids

NASA Astrophysics Data System (ADS)

Chu, Huiying; Peng, Xiangda; Li, Yan; Zhang, Yuebin; Min, Hanyi; Li, Guohui

2018-04-01

A polarizable atomic multipole-based force field for the membrane bilayer models 1,2-dioleoyl-phosphocholine (DOPC) and 1-palmitoyl-2-oleoyl-phosphatidylethanolamine (POPE) has been developed. The force field adopts the same framework as the Atomic Multipole Optimized Energetics for Biomolecular Applications (AMOEBA) model, in which the charge distribution of each atom is represented by the permanent atomic monopole, dipole and quadrupole moments. Many-body polarization including the inter- and intra-molecular polarization is modelled in a consistent manner with distributed atomic polarizabilities. The van der Waals parameters were first transferred from existing AMOEBA parameters for small organic molecules and then optimised by fitting to ab initio intermolecular interaction energies between models and a water molecule. Molecular dynamics simulations of the two aqueous DOPC and POPE membrane bilayer systems, consisting of 72 model molecules, were then carried out to validate the force field parameters. Membrane width, area per lipid, volume per lipid, deuterium order parameters, electron density profile, etc. were consistent with experimental values.

Friction and Wear on the Atomic Scale

NASA Astrophysics Data System (ADS)

Gnecco, Enrico; Bennewitz, Roland; Pfeiffer, Oliver; Socoliuc, Anisoara; Meyer, Ernst

Friction has long been the subject of research: the empirical da Vinci-Amontons friction laws have been common knowledge for centuries. Macroscopic experiments performed by the school of Bowden and Tabor revealed that macroscopic friction can be related to the collective action of small asperities. Over the last 15 years, experiments performed with the atomic force microscope have provided new insights into the physics of single asperities sliding over surfaces. This development, together with the results from complementary experiments using surface force apparatus and the quartz microbalance, have led to the new field of nanotribology. At the same time, increasing computing power has permitted the simulation of processes that occur during sliding contact involving several hundreds of atoms. It has become clear that atomic processes cannot be neglected when interpreting nanotribology experiments. Even on well-defined surfaces, experiments have revealed that atomic structure is directly linked to friction force. This chapter will describe friction force microscopy experiments that reveal, more or less directly, atomic processes during sliding contact.

MEAM interatomic force calculation subroutine for LAMMPS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stukowski, A.

2010-10-25

Interatomic force and energy calculation subroutine tobe used with the molecular dynamics simulation code LAMMPS (Ref a.). The code evaluates the total energy and atomic forces (energy gradient) according to cubic spine-based variant (Ref b.) of the Modified Embedded Atom Method (MEAM).

Isolating and moving single atoms using silicon nanocrystals

DOEpatents

Carroll, Malcolm S.

2010-09-07

A method is disclosed for isolating single atoms of an atomic species of interest by locating the atoms within silicon nanocrystals. This can be done by implanting, on the average, a single atom of the atomic species of interest into each nanocrystal, and then measuring an electrical charge distribution on the nanocrystals with scanning capacitance microscopy (SCM) or electrostatic force microscopy (EFM) to identify and select those nanocrystals having exactly one atom of the atomic species of interest therein. The nanocrystals with the single atom of the atomic species of interest therein can be sorted and moved using an atomic force microscope (AFM) tip. The method is useful for forming nanoscale electronic and optical devices including quantum computers and single-photon light sources.

Photocatalytic hollow TiO2 and ZnO nanospheres prepared by atomic layer deposition.

PubMed

Justh, Nóra; Bakos, László Péter; Hernádi, Klára; Kiss, Gabriella; Réti, Balázs; Erdélyi, Zoltán; Parditka, Bence; Szilágyi, Imre Miklós

2017-06-28

Carbon nanospheres (CNSs) were prepared by hydrothermal synthesis, and coated with TiO 2 and ZnO nanofilms by atomic layer deposition. Subsequently, through burning out the carbon core templates hollow metal oxide nanospheres were obtained. The substrates, the carbon-metal oxide composites and the hollow nanospheres were characterized with TG/DTA-MS, FTIR, Raman, XRD, SEM-EDX, TEM-SAED and their photocatalytic activity was also investigated. The results indicate that CNSs are not beneficial for photocatalysis, but the crystalline hollow metal oxide nanospheres have considerable photocatalytic activity.

Final Technical Report for Award DESC0011912, "Trimodal Tapping Mode Atomic Force Microscopy: Simultaneous 4D Mapping of Conservative and Dissipative Probe-Sample Interactions of Energy-Relevant Materials”

DOE Office of Scientific and Technical Information (OSTI.GOV)

Solares, Santiago D.

The final project report covering the period 7/1/14-6/30/17 provides an overview of the technical accomplishments in the areas of (i) fundamental viscoelasticity, (ii) multifrequency atomic force microscopy, and (iii) characterization of energy-relevant materials with atomic force microscopy. A list of publications supported by the project is also provided.

Microwave ac Zeeman force for ultracold atoms

NASA Astrophysics Data System (ADS)

Fancher, C. T.; Pyle, A. J.; Rotunno, A. P.; Aubin, S.

2018-04-01

We measure the ac Zeeman force on an ultracold gas of 87Rb due to a microwave magnetic field targeted to the 6.8 GHz hyperfine splitting of these atoms. An atom chip produces a microwave near field with a strong amplitude gradient, and we observe a force over three times the strength of gravity. Our measurements are consistent with a simple two-level theory for the ac Zeeman effect and demonstrate its resonant, bipolar, and spin-dependent nature. We observe that the dressed-atom eigenstates gradually mix over time and have mapped out this behavior as a function of magnetic field and detuning. We demonstrate the practical spin selectivity of the force by pushing or pulling a specific spin state while leaving other spin states unmoved.

Adaptive local basis set for Kohn–Sham density functional theory in a discontinuous Galerkin framework II: Force, vibration, and molecular dynamics calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Gaigong; Lin, Lin, E-mail: linlin@math.berkeley.edu; Computational Research Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720

Recently, we have proposed the adaptive local basis set for electronic structure calculations based on Kohn–Sham density functional theory in a pseudopotential framework. The adaptive local basis set is efficient and systematically improvable for total energy calculations. In this paper, we present the calculation of atomic forces, which can be used for a range of applications such as geometry optimization and molecular dynamics simulation. We demonstrate that, under mild assumptions, the computation of atomic forces can scale nearly linearly with the number of atoms in the system using the adaptive local basis set. We quantify the accuracy of the Hellmann–Feynmanmore » forces for a range of physical systems, benchmarked against converged planewave calculations, and find that the adaptive local basis set is efficient for both force and energy calculations, requiring at most a few tens of basis functions per atom to attain accuracies required in practice. Since the adaptive local basis set has implicit dependence on atomic positions, Pulay forces are in general nonzero. However, we find that the Pulay force is numerically small and systematically decreasing with increasing basis completeness, so that the Hellmann–Feynman force is sufficient for basis sizes of a few tens of basis functions per atom. We verify the accuracy of the computed forces in static calculations of quasi-1D and 3D disordered Si systems, vibration calculation of a quasi-1D Si system, and molecular dynamics calculations of H{sub 2} and liquid Al–Si alloy systems, where we show systematic convergence to benchmark planewave results and results from the literature.« less

Adaptive local basis set for Kohn–Sham density functional theory in a discontinuous Galerkin framework II: Force, vibration, and molecular dynamics calculations

DOE PAGES

Zhang, Gaigong; Lin, Lin; Hu, Wei; ...

2017-01-27

Recently, we have proposed the adaptive local basis set for electronic structure calculations based on Kohn–Sham density functional theory in a pseudopotential framework. The adaptive local basis set is efficient and systematically improvable for total energy calculations. In this paper, we present the calculation of atomic forces, which can be used for a range of applications such as geometry optimization and molecular dynamics simulation. We demonstrate that, under mild assumptions, the computation of atomic forces can scale nearly linearly with the number of atoms in the system using the adaptive local basis set. We quantify the accuracy of the Hellmann–Feynmanmore » forces for a range of physical systems, benchmarked against converged planewave calculations, and find that the adaptive local basis set is efficient for both force and energy calculations, requiring at most a few tens of basis functions per atom to attain accuracies required in practice. Sin ce the adaptive local basis set has implicit dependence on atomic positions, Pulay forces are in general nonzero. However, we find that the Pulay force is numerically small and systematically decreasing with increasing basis completeness, so that the Hellmann–Feynman force is sufficient for basis sizes of a few tens of basis functions per atom. We verify the accuracy of the computed forces in static calculations of quasi-1D and 3D disordered Si systems, vibration calculation of a quasi-1D Si system, and molecular dynamics calculations of H 2 and liquid Al–Si alloy systems, where we show systematic convergence to benchmark planewave results and results from the literature.« less

Adaptive local basis set for Kohn–Sham density functional theory in a discontinuous Galerkin framework II: Force, vibration, and molecular dynamics calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Gaigong; Lin, Lin; Hu, Wei

Recently, we have proposed the adaptive local basis set for electronic structure calculations based on Kohn–Sham density functional theory in a pseudopotential framework. The adaptive local basis set is efficient and systematically improvable for total energy calculations. In this paper, we present the calculation of atomic forces, which can be used for a range of applications such as geometry optimization and molecular dynamics simulation. We demonstrate that, under mild assumptions, the computation of atomic forces can scale nearly linearly with the number of atoms in the system using the adaptive local basis set. We quantify the accuracy of the Hellmann–Feynmanmore » forces for a range of physical systems, benchmarked against converged planewave calculations, and find that the adaptive local basis set is efficient for both force and energy calculations, requiring at most a few tens of basis functions per atom to attain accuracies required in practice. Sin ce the adaptive local basis set has implicit dependence on atomic positions, Pulay forces are in general nonzero. However, we find that the Pulay force is numerically small and systematically decreasing with increasing basis completeness, so that the Hellmann–Feynman force is sufficient for basis sizes of a few tens of basis functions per atom. We verify the accuracy of the computed forces in static calculations of quasi-1D and 3D disordered Si systems, vibration calculation of a quasi-1D Si system, and molecular dynamics calculations of H 2 and liquid Al–Si alloy systems, where we show systematic convergence to benchmark planewave results and results from the literature.« less

Adaptive local basis set for Kohn-Sham density functional theory in a discontinuous Galerkin framework II: Force, vibration, and molecular dynamics calculations

NASA Astrophysics Data System (ADS)

Zhang, Gaigong; Lin, Lin; Hu, Wei; Yang, Chao; Pask, John E.

2017-04-01

Recently, we have proposed the adaptive local basis set for electronic structure calculations based on Kohn-Sham density functional theory in a pseudopotential framework. The adaptive local basis set is efficient and systematically improvable for total energy calculations. In this paper, we present the calculation of atomic forces, which can be used for a range of applications such as geometry optimization and molecular dynamics simulation. We demonstrate that, under mild assumptions, the computation of atomic forces can scale nearly linearly with the number of atoms in the system using the adaptive local basis set. We quantify the accuracy of the Hellmann-Feynman forces for a range of physical systems, benchmarked against converged planewave calculations, and find that the adaptive local basis set is efficient for both force and energy calculations, requiring at most a few tens of basis functions per atom to attain accuracies required in practice. Since the adaptive local basis set has implicit dependence on atomic positions, Pulay forces are in general nonzero. However, we find that the Pulay force is numerically small and systematically decreasing with increasing basis completeness, so that the Hellmann-Feynman force is sufficient for basis sizes of a few tens of basis functions per atom. We verify the accuracy of the computed forces in static calculations of quasi-1D and 3D disordered Si systems, vibration calculation of a quasi-1D Si system, and molecular dynamics calculations of H2 and liquid Al-Si alloy systems, where we show systematic convergence to benchmark planewave results and results from the literature.

Dynamical Casimir-Polder force on a partially dressed atom near a conducting wall

DOE Office of Scientific and Technical Information (OSTI.GOV)

Messina, Riccardo; Vasile, Ruggero; Passante, Roberto

2010-12-15

We study the time evolution of the Casimir-Polder force acting on a neutral atom in front of a perfectly conducting plate, when the system starts its unitary evolution from a partially dressed state. We solve the Heisenberg equations for both atomic and field quantum operators, exploiting a series expansion with respect to the electric charge and an iterative technique. After discussing the behavior of the time-dependent force on an initially partially dressed atom, we analyze a possible experimental scheme to prepare the partially dressed state and the observability of this new dynamical effect.

Motion of Cesium Atoms in the One-Dimensional Magneto-Optical Trap

NASA Technical Reports Server (NTRS)

Li, Yimin; Chen, Xuzong; Wang, Qingji; Wang, Yiqiu

1996-01-01

The force to which Cs atoms are subjected in the one-dimensional magneto-optical trap (lD-MOT) is calculated, and properties of this force are discussed. Several methods to increase the number of Cs atoms in the lD-MOT are presented on the basis of the analysis of the capture and escape of Cs atoms in the ID-MOT.

A universal strategy for the creation of machine learning-based atomistic force fields

NASA Astrophysics Data System (ADS)

Huan, Tran Doan; Batra, Rohit; Chapman, James; Krishnan, Sridevi; Chen, Lihua; Ramprasad, Rampi

2017-09-01

Emerging machine learning (ML)-based approaches provide powerful and novel tools to study a variety of physical and chemical problems. In this contribution, we outline a universal strategy to create ML-based atomistic force fields, which can be used to perform high-fidelity molecular dynamics simulations. This scheme involves (1) preparing a big reference dataset of atomic environments and forces with sufficiently low noise, e.g., using density functional theory or higher-level methods, (2) utilizing a generalizable class of structural fingerprints for representing atomic environments, (3) optimally selecting diverse and non-redundant training datasets from the reference data, and (4) proposing various learning approaches to predict atomic forces directly (and rapidly) from atomic configurations. From the atomistic forces, accurate potential energies can then be obtained by appropriate integration along a reaction coordinate or along a molecular dynamics trajectory. Based on this strategy, we have created model ML force fields for six elemental bulk solids, including Al, Cu, Ti, W, Si, and C, and show that all of them can reach chemical accuracy. The proposed procedure is general and universal, in that it can potentially be used to generate ML force fields for any material using the same unified workflow with little human intervention. Moreover, the force fields can be systematically improved by adding new training data progressively to represent atomic environments not encountered previously.

The Chemical Structure and Acid Deterioration of Paper.

ERIC Educational Resources Information Center

Hollinger, William K., Jr.

1984-01-01

Describes the chemical structure of paper, including subatomic particles, atoms and molecules, and the forces that bond atoms into molecules, molecules into chains, chains into sheets, and sheets into layers. Acid is defined, and the deleterious role of acid in breaking the forces that bond atoms into molecules is detailed. (EJS)

Dynamic-force spectroscopy measurement with precise force control using atomic-force microscopy probe

NASA Astrophysics Data System (ADS)

Takeuchi, Osamu; Miyakoshi, Takaaki; Taninaka, Atsushi; Tanaka, Katsunori; Cho, Daichi; Fujita, Machiko; Yasuda, Satoshi; Jarvis, Suzanne P.; Shigekawa, Hidemi

2006-10-01

The accuracy of dynamic-force spectroscopy (DFS), a promising technique of analyzing the energy landscape of noncovalent molecular bonds, was reconsidered in order to justify the use of an atomic-force microscopy (AFM) cantilever as a DFS force probe. The advantages and disadvantages caused, for example, by the force-probe hardness were clarified, revealing the pivotal role of the molecular linkage between the force probe and the molecular bonds. It was shown that the feedback control of the loading rate of tensile force enables us a precise DFS measurement using an AFM cantilever as the force probe.

Experimental Demonstration of a Synthetic Lorentz Force by Using Radiation Pressure.

PubMed

Šantić, N; Dubček, T; Aumiler, D; Buljan, H; Ban, T

2015-09-02

Synthetic magnetism in cold atomic gases opened the doors to many exciting novel physical systems and phenomena. Ubiquitous are the methods used for the creation of synthetic magnetic fields. They include rapidly rotating Bose-Einstein condensates employing the analogy between the Coriolis and the Lorentz force, and laser-atom interactions employing the analogy between the Berry phase and the Aharonov-Bohm phase. Interestingly, radiation pressure - being one of the most common forces induced by light - has not yet been used for synthetic magnetism. We experimentally demonstrate a synthetic Lorentz force, based on the radiation pressure and the Doppler effect, by observing the centre-of-mass motion of a cold atomic cloud. The force is perpendicular to the velocity of the cold atomic cloud, and zero for the cloud at rest. Our novel concept is straightforward to implement in a large volume, for a broad range of velocities, and can be extended to different geometries.

Note: Effect of the parasitic forced vibration in an atom gravimeter

NASA Astrophysics Data System (ADS)

Chen, Le-Le; Luo, Qin; Zhang, Heng; Duan, Xiao-Chun; Zhou, Min-Kang; Hu, Zhong-Kun

2018-06-01

The vibration isolator usually plays an important role in atom interferometry gravimeters to improve their sensitivity. We show that the parasitic forced vibration of the Raman mirror, which is induced by external forces acting on the vibration isolator, can cause a bias in atom gravimeters. The mechanism of how this effect induces an additional phase shift in our interferometer is analyzed. Moreover, modulation experiments are performed to measure the dominant part of this effect, which is caused by the magnetic force between the passive vibration isolator and the coil of the magneto-optic trap. In our current apparatus, this forced vibration contributes a systematic error of -2.3(2) × 10-7 m/s2 when the vibration isolator works in the passive isolation mode. Even suppressed with an active vibration isolator, this effect can still contribute -6(1) × 10-8 m/s2; thus, it should be carefully considered in precision atom gravimeters.

Analytical Model of the Nonlinear Dynamics of Cantilever Tip-Sample Surface Interactions for Various Acoustic-Atomic Force Microscopies

NASA Technical Reports Server (NTRS)

Cantrell, John H., Jr.; Cantrell, Sean A.

2008-01-01

A comprehensive analytical model of the interaction of the cantilever tip of the atomic force microscope (AFM) with the sample surface is developed that accounts for the nonlinearity of the tip-surface interaction force. The interaction is modeled as a nonlinear spring coupled at opposite ends to linear springs representing cantilever and sample surface oscillators. The model leads to a pair of coupled nonlinear differential equations that are solved analytically using a standard iteration procedure. Solutions are obtained for the phase and amplitude signals generated by various acoustic-atomic force microscope (A-AFM) techniques including force modulation microscopy, atomic force acoustic microscopy, ultrasonic force microscopy, heterodyne force microscopy, resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM), and the commonly used intermittent contact mode (TappingMode) generally available on AFMs. The solutions are used to obtain a quantitative measure of image contrast resulting from variations in the Young modulus of the sample for the amplitude and phase images generated by the A-AFM techniques. Application of the model to RDF-AFUM and intermittent soft contact phase images of LaRC-cp2 polyimide polymer is discussed. The model predicts variations in the Young modulus of the material of 24 percent from the RDF-AFUM image and 18 percent from the intermittent soft contact image. Both predictions are in good agreement with the literature value of 21 percent obtained from independent, macroscopic measurements of sheet polymer material.

Evaluating structures, properties and vibrational and electronic spectra of the potassium 2-isonicotinoyltrifluoroborate salt

NASA Astrophysics Data System (ADS)

Iramain, Maximiliano A.; Davies, Lilian; Brandán, Silvia Antonia

2018-07-01

The potassium 2-isonicotinoyltrifluorborate salt has been characterized by using FT-IR, FT-Raman and UV-Visible spectroscopies while its structural properties were studied by using B3LYP/6-31G* and B3LYP/6-311++G** calculations in gas and aqueous solution phases. Four conformers with CS and C1 symmetries were found in the potential energy surfaces but only one of them presents the minimum energy. Two dimeric species of this salt were also optimized in accordance to the layered architectures suggested for trifluoroborate potassium salts in the solid phase. Here, the experimental Raman bands at 796, 748 and 676 cm-1 clearly support the presence of both dimers. On the other hand, the 2-isonicotinoyltrifluorborate anion was optimized because its presence is expected in solution. Reasonable correlations were observed between the predicted FTIR, Raman and UV-visible spectra with the corresponding experimental ones. The solvation energies for the salt in aqueous solution were predicted by using both methods. Here, it is observed that the change of furane by pyridine ring generates an increase in the solvation energies of the potassium 2-isonicotinoyltrifluorborate salt in relation to potassium 3-furoyltrifluoroborate salt. The study of the charges has revealed that there is an effect of the size of the basis set on the Mulliken charges while the AIM analyses suggest that the F⋯H and O⋯K interactions are also strongly dependent of the medium and the size of the basis sets. The bond orders for the F and K atoms evidence their higher ionic characteristics in solution with both basis sets. The NBO and AIM results clearly support the higher stability of this salt in both media. The studies by using the frontier orbitals indicate that the change of furane by pyridine ring decreases the reactivity of this salt by using 6-31G* basis set but increases when the other one is employed. Another effect of change of furane by pyridine ring is observed in the increase of the f(νCdbnd O) and f(νBF3) force constants. In addition, the force fields for the salt in both media were reported together to their complete vibrational assignments and force constants by using both levels of theory.

Quantum mechanical study of the structure and spectroscopic (FT-IR, FT-Raman, 13C, 1H and UV), first order hyperpolarizabilities, NBO and TD-DFT analysis of the 4-methyl-2-cyanobiphenyl

NASA Astrophysics Data System (ADS)

Sebastian, S.; Sundaraganesan, N.; Karthikeiyan, B.; Srinivasan, V.

2011-02-01

The Fourier transform infrared (FT-IR) and FT-Raman of 4-methyl-2-cyanobiphenyl (4M2CBP) have been recorded and analyzed. The equilibrium geometry, bonding features and harmonic vibrational frequencies have been investigated with the help of density functional theory (DFT) method. The assignments of the vibrational spectra have been carried out with the help of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology (SQMFF). The 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by the Gauge including atomic orbital (GIAO) method. The first order hyperpolarizability ( β0) of this novel molecular system and related properties ( β, α0 and Δ α) of 4M2CBP are calculated using HF/6-311G(d,p) method on the finite-field approach. Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital (NBO) analysis. The results show that charge in electron density (ED) in the σ* and π* antibonding orbitals and second order delocalization energies ( E2) confirms the occurrence of intramolecular charge transfer (ICT) within the molecule. UV-vis spectrum of the compound was recorded and the electronic properties, such as HOMO and LUMO energies, were performed by time-dependent density functional theory (TD-DFT) approach. Finally the calculations results were applied to simulated infrared and Raman spectra of the title compound which show good agreement with observed spectra.

Studies on Electrical and Magnetic Properties of Mg-Substituted Nickel Ferrites

NASA Astrophysics Data System (ADS)

Chavan, Pradeep; Naik, L. R.; Belavi, P. B.; Chavan, Geeta; Ramesha, C. K.; Kotnala, R. K.

2017-01-01

The semiconducting polycrystalline ferrite materials with the general formula Ni1- x Mg x Fe2O4 were synthesized by using the solid state reaction method. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrographs, and atomic force microscopy techniques were utilized to study the structural parameters. XRD confirms the formation of single phase cubic spinel structure of the ferrites. The crystallite sizes of ferrites determined using the Debye-Scherer formula ranges from 0.963 μm to 1.069 μm. The cation distribution of ferrite shows that Mg2+ ions occupy a tetrahedral site ( A-site) and the Ni2+ ion occupy an octahedral site ( B-site) whereas Fe3+ ions occupies an octahedral as well as a tetrahedral site. The study of elastic parameters such as the longitudinal modulus, rigidity modulus, Young's modulus, bulk modulus, and Debye temperature were estimated using the FTIR technique. The decrease of direct current (DC) resistivity with increase in temperature indicates the semiconducting nature of ferrites. The dielectric constant as well as loss tangent decreases with increase in frequency, and at still higher frequencies, they are almost constant. This shows usual dielectric dispersion behavior attributed to the Maxwell-Wagner type of interfacial polarization and is in accordance with Koop's phenomenological theory. The linear increase of alternating current conductivity with increase of frequency shows the small polaron hopping type of conduction mechanism in all the ferrites. The magnetic properties such as saturation magnetization ( M s ), magnetic moment, coercivity, remnant magnetization ( M r ), and the ratio of M r /M s was estimated using the M-H loop.

Biosynthesis of silver nanoparticles from Cavendish banana peel extract and its antibacterial and free radical scavenging assay: a novel biological approach

NASA Astrophysics Data System (ADS)

Kokila, T.; Ramesh, P. S.; Geetha, D.

2015-12-01

Biosynthesis of metallic silver nanoparticles has now become an alternative to physical and chemical approaches. In the present study, silver nanoparticles (AgNPs) were synthesized from Cavendish banana peel extract (CBPE) and characterized by UV-visible spectroscopy, X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Atomic force microscopy (AFM), Field emission scanning electronic microscope (FESEM), Dynamic light scattering (DLS) and zeta potential (ZP). The AgNPs formation was confirmed by UV-visible spectroscopy through color conversion due to surface plasma resonance band at 430 nm. The effect of pH on nanoparticle synthesis was determined by adjusting the various pH of the reaction mixtures. The crystalline nature of nanoparticles was confirmed from the XRD pattern, and the grain size was found to be around 34 nm. To identify the compounds responsible for the bioreduction of Ag+ ion and the stabilization of AgNPs produced, the functional group present in Cavendish banana peel extract was investigated using FTIR. AFM has proved to be very helpful in determining morphological features and the diameter of AgNPs in the range of 23-30 nm was confirmed by FESEM. DLS studies revealed that the average size of AgNPs was found to be around 297 nm. Zeta potential value for AgNPs obtained was -11 mV indicating the moderate stability of synthesized nanoparticles. The antibacterial activity of the nanoparticles was studied against Gram-positive and Gram-negative bacteria. Biosynthesized AgNPs showed a strong DPPH radical and ABTS scavengers compared to the aqueous peel extract of Cavendish banana.

Synthesis of silver nanoparticles from stem bark of Cochlospermum religiosum (L.) Alston: an important medicinal plant and evaluation of their antimicrobial efficacy

NASA Astrophysics Data System (ADS)

Sasikala, A.; Linga Rao, M.; Savithramma, N.; Prasad, T. N. V. K. V.

2015-10-01

The use of different parts of plants for the synthesis of nanoparticles is considered as a green technology as it does not involve any harmful chemicals. Herein, we report on rapid biosynthesis of silver nanoparticles (SNPs) from aqueous stem bark extract of Cochlospermum religiosum a medicinal plant. The reduced silver nanoparticles were characterized by using UV-Visible spectroscopy (UV-Vis), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis, atomic force microscopy, and Fourier transform infrared (FT-IR). The UV-Visible spectrum of the aqueous medium containing silver nanoparticles showed an absorption peak at around 445 nm, XRD showed that the particles are crystalline in nature, with a face-centered cubic structure and the SEM images showed that the spherical-shaped silver nanoparticles were observed and the size range was found to be 20-35 nm. FT-IR spectroscopy analysis revealed that carbohydrate, polyphenols, and protein molecules were involved in the synthesis and capping of silver nanoparticles. These phytosynthesized SNPs were tested for their antimicrobial activity and it analyzed by measuring the inhibitory zone. Cochlospermum religiosum aqueous stem bark extract of SNPs showed highest toxicity to Staphylococcus followed by Pseudomonas, Escherichia coli and Bacillus and lowest toxicity towards Proteus. Whereas in fungal species highest inhibition zone against Aspergillus flavus followed by Rhizopus, Fusarium, and Curvularia, and minimum inhibition zone was observed against Aspergillus niger species. The outcome of this study could be useful for the development of value added products from indigenous medicinal plants of India for nanotechnology-based biomedical applications.

Mulberry leaf extract mediated synthesis of gold nanoparticles and its anti-bacterial activity against human pathogens

NASA Astrophysics Data System (ADS)

Adavallan, K.; Krishnakumar, N.

2014-06-01

Gold nanoparticles (Au-NPs) were synthesized at room temperature using Morus alba (mulberry) leaf extract as reducing and stabilizing agent. The development of plant mediated synthesis of nanoparticles is gaining importance due to its simplicity, low cost, non-toxicity, eco-friendliness, long term stability and reproducible aqueous synthesis method to obtain a self-assembly of nearly monodispersed Au-NPs. The formation and morphology of biosynthesized nanoparticles are investigated with the help of UV-Vis spectroscopy, dynamic light scattering (DLS), transmission electron microscopy (TEM), atomic force microscopy (AFM), x-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR) techniques. Au-NPs formation was screened by UV-Vis spectroscopy through color conversion due to surface plasmon resonance band at 538 nm for Au-NPs. DLS studies revealed that the average size of Au-NPs was 50 nm. TEM studies showed the particles to be nearly spherical with few irregular shapes and particle size ranges 15-53 nm. The AFM image clearly shows the surface morphology of the well-dispersed Au-NPs with less than 50 nm. The high crystallinity of nanoparticles is evident from bright circular spots in the selected area electron diffraction (SAED) pattern. X-ray diffraction pattern showed high purity and face-centered cubic structure of Au-NPs. The FT-IR results indicate the presence of different functional groups present in the biomolecule capping the nanoparticles. Further, biosynthesized Au-NPs show strong zone of inhibition against Vibrio cholera (gram-negative) and Staphylococcus aureus (gram-positive) whereas, chemically synthesized Au-NPs and mulberry leaf extract exhibit a fair zone of inhibition.

Peptide conjugated polymeric nanoparticles as a carrier for targeted delivery of docetaxel.

PubMed

Kulhari, Hitesh; Pooja, Deep; Shrivastava, Shweta; V G M, Naidu; Sistla, Ramakrishna

2014-05-01

The aim of this research work was to develop Bombesin peptide (BBN) conjugated, docetaxel loaded nanocarrier for the treatment of breast cancer. Docetaxel loaded nanoparticles (DNP) were prepared by solvent evaporation method using sodium cholate as surfactant. BBN was conjugated to DNP surface through covalent bonding. Both DNP and BBN conjugated DNP (BDNP) were characterized by various techniques such as dynamic light scattering, Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC) and thermogravimetric analysis. The particle diameter and zeta potential of BDNP were 136±3.95 nm and -10.8±2.7 mV, respectively. The change in surface charge and FTIR studies confirmed the formation of amide linkage between BBN and DNP. AFM analysis showed that nanoparticles were spherical in shapes. In nanoparticles, docetaxel was present in its amorphous form as confirmed by DSC and PXRD analysis and was stable during the thermal studies. The formulations showed the sustained release of DTX over the period of 120 h. During cellular toxicity assay in gastrin releasing peptide receptor positive breast cancer cells (MDA-MB-231), BDNP were found to be 12 times more toxic than pure DTX and Taxotere. The IC50 value for DTX, Taxotere, DNP and BDNP was >375, >375, 142.23 and 35.53 ng/ml, respectively. The above studies showed that Bombesin conjugated nanocarrier system could be a promising carrier for active targeting of anticancer drugs in GRP receptor over expressing cancer cells. Copyright © 2014 Elsevier B.V. All rights reserved.

Influence of 400 keV carbon ion implantation on structural, optical and electrical properties of PMMA

NASA Astrophysics Data System (ADS)

Arif, Shafaq; Rafique, M. Shahid; Saleemi, Farhat; Sagheer, Riffat; Naab, Fabian; Toader, Ovidiu; Mahmood, Arshad; Rashid, Rashad; Mahmood, Mazhar

2015-09-01

Ion implantation is a useful technique to modify surface properties of polymers without altering their bulk properties. The objective of this work is to explore the 400 keV C+ ion implantation effects on PMMA at different fluences ranging from 5 × 1013 to 5 × 1015 ions/cm2. The surface topographical examination of irradiated samples has been performed using Atomic Force Microscope (AFM). The structural and chemical modifications in implanted PMMA are examined by Raman and Fourier Infrared Spectroscopy (FTIR) respectively. The effects of carbon ion implantation on optical properties of PMMA are investigated by UV-Visible spectroscopy. The modifications in electrical conductivity have been measured using a four point probe technique. AFM images reveal a decrease in surface roughness of PMMA with an increase in ion fluence from 5 × 1014 to 5 × 1015 ions/cm2. The existence of amorphization and sp2-carbon clusterization has been confirmed by Raman and FTIR spectroscopic analysis. The UV-Visible data shows a prominent red shift in absorption edge as a function of ion fluence. This shift displays a continuous reduction in optical band gap (from 3.13 to 0.66 eV) due to formation of carbon clusters. Moreover, size of carbon clusters and photoconductivity are found to increase with increasing ion fluence. The ion-induced carbonaceous clusters are believed to be responsible for an increase in electrical conductivity of PMMA from (2.14 ± 0.06) × 10-10 (Ω-cm)-1 (pristine) to (0.32 ± 0.01) × 10-5 (Ω-cm)-1 (irradiated sample).

Structural and optical studies of 100 MeV Au irradiated thin films of tin oxide

NASA Astrophysics Data System (ADS)

Jaiswal, Manoj Kumar; Kanjilal, D.; Kumar, Rajesh

2013-11-01

Thin films of tin(IV) oxide (SnO2) of 100 nm thickness were grown on silicon (1 0 0) matrices by electron beam evaporation deposition technique under high vacuum. The thicknesses of these films were monitored by piezo-sensor attached to the deposition chamber. Nanocrystallinity is achieved in these thin films by 100 MeV Au8+ using 1 pnA current at normal incidence with ion fluences varying from 1 × 1011 ions/cm2 to 5 × 1013 ions/cm2. Swift Heavy Ion beam irradiation was carried out by using 15 UD Pelletron Accelerator at IUAC, New Delhi, India. Optical studies of pristine and ion irradiated thin films were characterized by UV-Visible spectroscopy and Fourier Transform Infrared (FTIR) spectroscopy. Prominent peak at 610 cm-1 in FTIR spectrum confirmed the O-Sn-O bonding of tin(IV) oxide. For Surface topographical studies and grain size calculations, these films were characterized by Atomic Force Microscope (AFM) using Nanoscope III-A. Crystallinity and phase transformation due to irradiation of pristine and irradiated films were characterized by Glancing Angle X-ray Diffraction (GAXRD) using Brucker-D8 advance model. GAXRD results show improvement in crystallinity and phase transformation due to swift heavy ion irradiation. Grain size distribution was verified by AFM and GAXRD results. Swift heavy ion induced modifications in thin films of SnO2 were confirmed by the presence of prominent peaks at 2θ values of 30.65°, 32.045°, 43.94°, 44.96° and 52.36° in GAXRD spectrum.

Conformational stability, spectroscopic (FT-IR, FT-Raman and UV-Vis) analysis, NLO, NBO, FMO and Fukui function analysis of 4-hexylacetophenone by density functional theory.

PubMed

Saravanan, S; Balachandran, V

2015-03-05

The experimental and theoretical study on the structures and vibrations of 4-hexylacetophenone (abbreviated as 4HAP) are presented. The FT-IR and FT-Raman spectra of the title compound have been recorded in the region 4000-400cm(-1) and 3500-100cm(-1) respectively. The molecular structures, vibrational wavenumbers, infrared intensities and Raman activities were calculated using DFT (B3LYP and LSDA) method with 6-311++G(d,p) basis set. The most stable conformer of 4HAP is identified from the computational results. The assignments of the vibrational spectra have been carried out with the aid of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology (SQMEF). The linear polarizability (α) and the first hyperpolarizability (βtot) values of the investigated molecule have been computed using B3LYP and LSDA with 6-311++G(d,p) basis set. Stability of the molecule arising from hyper conjugative interaction and charge transfer delocalization has been analyzed using natural bond orbital (NBO) analysis. The molecule orbital contributions are studied by density of energy states (DOSs). UV-Vis spectrum and effects of solvents have been discussed effects of solvents have been discussed and the electronic properties such as HOMO and LUMO energies were determined by time-dependent TD-DFT approach. Fukui function and Mulliken analysis on atomic charges of the title compound have been calculated. Finally, electrophilic and nucleophilic descriptors of the title molecule have been calculated. Copyright © 2014 Elsevier B.V. All rights reserved.

Green biosynthesis of silver nanoparticles using leaves extract of Artemisia vulgaris and their potential biomedical applications.

PubMed

Rasheed, Tahir; Bilal, Muhammad; Iqbal, Hafiz M N; Li, Chuanlong

2017-10-01

Biosynthesis of nanoparticles from plant extracts is receiving enormous interest due to their abundant availability and a broad spectrum of bioactive reducing metabolites. In this study, the reducing potential of Artemisia vulgaris leaves extract (AVLE) was investigated for synthesizing silver nanoparticles without the addition of any external reducing or capping agent. The appearance of blackish brown color evidenced the complete synthesis of nanoparticles. The synthesized silver nanoparticles were characterized by UV-vis spectroscopy, scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscope (TEM), atomic force microscopy (AFM) and Fourier transforms infrared spectroscopy (FT-IR) analysis. UV-vis absorption profile of the bio-reduced sample elucidated the main peak around 420nm, which correspond to the surface plasmon resonance of silver nanoparticles. SEM and AFM analyses confirmed the morphology of the synthesized nanoparticles. Similarly, particles with a distinctive peak of silver were examined with EDX. The average diameter of silver nanoparticles was about 25nm from Transmission Electron Microscopy (TEM). FTIR spectroscopy scrutinized the involvement of various functional groups during nanoparticle synthesis. The green synthesized nanoparticles presented effective antibacterial activity against pathogenic bacteria than AVLE alone. In-vitro antioxidant assays revealed that silver nanoparticles (AV-AgNPs) exhibited promising antioxidant properties. The nanoparticles also displayed a potent cytotoxic effect against HeLa and MCF-7 cell lines. In conclusion, the results supported the advantages of employing a bio-green approach for developing silver nanoparticles with antimicrobial, antioxidant, and antiproliferative activities in a simple and cost- competitive manner. Copyright © 2017 Elsevier B.V. All rights reserved.

Controlling Casimir force via coherent driving field

NASA Astrophysics Data System (ADS)

Ahmad, Rashid; Abbas, Muqaddar; Ahmad, Iftikhar; Qamar, Sajid

2016-04-01

A four level atom-field configuration is used to investigate the coherent control of Casimir force between two identical plates made up of chiral atomic media and separated by vacuum of width d. The electromagnetic chirality-induced negative refraction is obtained via atomic coherence. The behavior of Casimir force is investigated using Casimir-Lifshitz formula. It is noticed that Casimir force can be switched from repulsive to attractive and vice versa via coherent control of the driving field. This switching feature provides new possibilities of using the repulsive Casimir force in the development of new emerging technologies, such as, micro-electro-mechanical and nano-electro-mechanical systems, i.e., MEMS and NEMS, respectively.

Kinetics of new thermal donors (NTDs) in CZ-silicon based on FTIR analysis

NASA Astrophysics Data System (ADS)

Singh, Rajeev; Singh, Shyam; Yadav, Bal Chandra

2018-05-01

Oxygen is quite friendly to silicon and is interstitially positioned well guarded by neighbouring silicon atoms on regular sites, provides mechanical strength to the silicon wafers and helps in internal gettering. Oxygen dimers are a fast diffusing species. Presence of trimers provides a wider platform for interconversion of dimer-trimer and V-O interaction. Oxygen atoms in isomeric positions really play a trick in the formation of TDD0 - TDD16. Other members of the donor species are likely due to the addition of dimers/trimers. FTIR analysis of boron-doped CZ-silicon annealed at 495 °C revealed a unique feature that the nature of 999 cm-1 absorption peak corresponding to TDD3 is contrary to 1107 cm-1 absorption peak corresponding to interstitial oxygen in silicon. Isothermal annealing at different temperatures also indicates slow disappearance of one donor species and emergence of other donor species. Thermal acceptors and recombination centers intrinsically present in the as grown silicon crystal and/or generated as a result of annealing do contribute to lower the donor concentration.

Synthesis, spectroscopic investigations (FT-IR, NMR, UV-Vis, and TD-DFT), and molecular docking of (E)-1-(benzo[d][1, 3]dioxol-6-yl)-3-(6-methoxynaphthalen-2-yl)prop-2-en-1-one

NASA Astrophysics Data System (ADS)

Therasa Alphonsa, A.; Loganathan, C.; Athavan Alias Anand, S.; Kabilan, S.

2017-02-01

The compound (E)-1-(benzo [d] [1, 3] dioxol-6-yl)-3-(6-methoxy naphthalen-2-yl) prop-2-en-1-one (AKN) was synthesized and characterized by FT-IR, NMR, and UV-Vis spectrometer. The optimized molecular geometry, bond lengths, bond angles, atomic charges, harmonic vibrational wave numbers and intensities of vibrational bonds of the title compound have been investigated by Time dependent- Density Functional Theory (TD-DFT) using a standard B3LYP method with 6-31 G (d, p) basis set available in the Gaussian 09W package. 1H and 13C NMR chemical shifts of the molecule were calculated using Gauge-independent atomic orbital method (GIAO). Experimental excitation energies of the molecules were matched with the theoretically calculated energies. The atomic charge distributions of the various atoms present in the AKN were obtained by Mulliken charge population analysis. The Molecular Electrostatic Potential (MEP) analysis reveals the sites for electrophilic attack and nucleophilic reactions in the molecule. The difference between the observed and scaled frequencies was small. The HOMO to LUMO transition implies an electron density transfer. The intramolecular contacts have been interpreted using Natural Bond Orbital (NBO) analysis. The calculation results were applied to simulate spectra of the title compound, which show excellent agreement with observed spectra. To provide information about the interactions between human cytochrome protein and the novel compound theoretically, docking studies were carried out using Schrödinger software.

The Analog Atomic Force Microscope: Measuring, Modeling, and Graphing for Middle School

ERIC Educational Resources Information Center

Goss, Valerie; Brandt, Sharon; Lieberman, Marya

2013-01-01

using an analog atomic force microscope (A-AFM) made from a cardboard box and mailing tubes. Varying numbers of ping pong balls inside the tubes mimic atoms on a surface. Students use a dowel to make macroscale measurements similar to those of a nanoscale AFM tip as it…

Uncertainties in forces extracted from non-contact atomic force microscopy measurements by fitting of long-range background forces.

PubMed

Sweetman, Adam; Stannard, Andrew

2014-01-01

In principle, non-contact atomic force microscopy (NC-AFM) now readily allows for the measurement of forces with sub-nanonewton precision on the atomic scale. In practice, however, the extraction of the often desired 'short-range' force from the experimental observable (frequency shift) is often far from trivial. In most cases there is a significant contribution to the total tip-sample force due to non-site-specific van der Waals and electrostatic forces. Typically, the contribution from these forces must be removed before the results of the experiment can be successfully interpreted, often by comparison to density functional theory calculations. In this paper we compare the 'on-minus-off' method for extracting site-specific forces to a commonly used extrapolation method modelling the long-range forces using a simple power law. By examining the behaviour of the fitting method in the case of two radically different interaction potentials we show that significant uncertainties in the final extracted forces may result from use of the extrapolation method.

Structural phase transition of as-synthesized Sr-Mn nanoferrites by annealing temperature

NASA Astrophysics Data System (ADS)

Amer, M. A.; Meaz, T. M.; Attalah, S. S.; Ghoneim, A. I.

2015-11-01

The Sr0.2Mn0.8Fe2O4 nanoparticle ferrites were synthesized by the co-precipitation method and annealed at different temperatures T. XRD, TEM, FT-IR, VSM and Mössbauer techniques were used to characterize the samples. This study proved that the structural phase of nanoferrites was transformed from cubic spinel for T≤500 °C to Z-type hexagonal for T≥700 °C. The structural transformation was attributed to Jahn-Teller effect of the Mn3+ ions and/or atomic disorder existed in the crystal lattice. The obtained spectra and parameters for the samples were affected by the transformation process. The lattice constant a showed a splitting to a and c for T>500 °C. The lattice constant c, grain and crystallite size R, strain, octahedral B-site band position and force constant, Debye temperature, coercivity Hc, remnant magnetization, squareness and magnetic moment, spontaneous magnetization and hyperfine magnetic fields showed increase against T. The lattice constant a, distortion and dislocation parameters, specific surface area, tetrahedral A-site band position and force constant, threshold frequency, Young's and bulk moduli, saturation magnetization Ms, area ratio of B-/A-sites, A-site line width were decreased with T. Experimental and theoretical densities, porosity, Poison ratio, stiffness constants, rigidity modulus, B-site line width and spontaneous magnetization showed dependence on T, whereas Ms and Hc proved dependence on R.

Syntheses, spectroscopic and thermal analyses of cyanide bridged heteronuclear polymeric complexes: [M(L)2Ni(CN)4]n (Ldbnd N-methylethylenediamine or N-ethylethylenediamine; Mdbnd Ni(II), Cu(II), Zn(II) or Cd(II))

NASA Astrophysics Data System (ADS)

Karaağaç, Dursun; Kürkçüoğlu, Güneş Süheyla

2016-02-01

Polymeric tetracyanonickelate(II) complexes of the type [M(L)2Ni(CN)4]n (Ldbnd N-methylethylenediamine (men) or N-ethylethylenediamine (neen); Mdbnd Ni(II), Cu(II), Zn(II) or Cd(II)) have been prepared and characterized by FT-IR, Raman spectroscopy, thermal and elemental analysis techniques. Additionally, FT-IR and Raman spectral analyses of men and neen have experimentally and theoretically investigated in the range of 4000-250 cm-1. The corresponding vibration assignments of men and neen are performed by using B3LYP density functional theory (DFT) method together with 6-31 G(d) basis set. The spectral features of the complexes suggest that the coordination environment of the M(II) ions are surrounded by the two symmetry related men and neen ligands and the two symmetry related N atom of cyanide groups, whereas the Ni(II) atoms are coordinated with a square-planar to four C atoms of the cyanide groups. Polymeric structures of the complexes consist of one dimensional alternative chains of [M(L)2]2+ and [Ni(CN)4]2- moieties. The thermal decompositions in the temperature range 30-700 °C of the complexes were investigated in the static air atmosphere.

Characterization of Akiyama probe applied to dual-probes atomic force microscope

NASA Astrophysics Data System (ADS)

Wang, Hequn; Gao, Sitian; Li, Wei; Shi, Yushu; Li, Qi; Li, Shi; Zhu, Zhendong

2016-10-01

The measurement of nano-scale line-width has always been important and difficult in the field of nanometer measurements, while the rapid development of integrated circuit greatly raises the demand again. As one kind of scanning probe microscope (SPM), atomic force microscope (AFM) can realize quasi three-dimensional measurement, which is widely used in nanometer scale line-width measurement. Our team researched a dual-probes atomic force microscope, which can eliminate the prevalent effect of probe width on measurement results. In dual-probes AFM system, a novel head are newly designed. A kind of self-sensing and self-exciting probes which is Nanosensors cooperation's patented probe—Akiyama probe, is used in this novel head. The Akiyama probe applied to dual-probe atomic force microscope is one of the most important issues. The characterization of Akiyama probe would affect performance and accuracy of the whole system. The fundamental features of the Akiyama probe are electrically and optically characterized in "approach-withdraw" experiments. Further investigations include the frequency response of an Akiyama probe to small mechanical vibrations externally applied to the tip and the effective loading force yielding between the tip and the sample during the periodic contact. We hope that the characterization of the Akiyama probe described in this paper will guide application for dual-probe atomic force microscope.

Resonant difference-frequency atomic force ultrasonic microscope

NASA Technical Reports Server (NTRS)

Cantrell, John H. (Inventor); Cantrell, Sean A. (Inventor)

2010-01-01

A scanning probe microscope and methodology called resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM), employs an ultrasonic wave launched from the bottom of a sample while the cantilever of an atomic force microscope, driven at a frequency differing from the ultrasonic frequency by one of the contact resonance frequencies of the cantilever, engages the sample top surface. The nonlinear mixing of the oscillating cantilever and the ultrasonic wave in the region defined by the cantilever tip-sample surface interaction force generates difference-frequency oscillations at the cantilever contact resonance. The resonance-enhanced difference-frequency signals are used to create images of nanoscale near-surface and subsurface features.

Characterization of PLD grown WO3 thin films for gas sensing

NASA Astrophysics Data System (ADS)

Boyadjiev, Stefan I.; Georgieva, Velichka; Stefan, Nicolaie; Stan, George E.; Mihailescu, Natalia; Visan, Anita; Mihailescu, Ion N.; Besleaga, Cristina; Szilágyi, Imre M.

2017-09-01

Tungsten trioxide (WO3) thin films were grown by pulsed laser deposition (PLD) with the aim to be applied in gas sensors. The films were studied by atomic force microscopy (AFM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and profilometry. To study the gas sensing behavior of these WO3 films, they were deposited on quartz resonators and the quartz crystal microbalance (QCM) method was applied to analyze their gas sensitivity. Synthesis of tetragonal-WO3 films starting from a target with predominantly monoclinic WO3 phase was observed. The films deposited at 300 °C presented a surface topology favorable for the sorption properties, consisting of a film matrix with protruding craters/cavities. QCM prototype sensors with such films were tested for NO2 sensing. The PLD grown WO3 thin films show good sensitivity and fast reaction at room temperature, even in as-deposited state. With the presented technology, the manufacturing of QCM gas sensors is simple, fast and cost-effective, and it is also suitable for energy-effective portable equipment for on-line monitoring of environmental changes.

Molecularly imprinted membranes (MIMs) for selective removal of polychlorinated biphenyls (PCBs) in environmental waters: fabrication and characterization.

PubMed

Mkhize, Dennis S; Nyoni, Hlengilizwe; Quinn, Laura P; Mamba, Bhekie B; Msagati, Titus A M

2017-04-01

Molecularly imprinted membranes (MIMs) with selective removal properties for polychlorinated biphenyls (PCBs) were prepared through the phase inversion technique. The MIMs were obtained from casting the viscous solutions of molecularly imprinted polymers (MIPs), polysulfone (PSf), and N-methyl-2-pyrrolidone (NMP) as the casting solvent. Different membranes were prepared at different concentration of MIPs and PSf. The resulting MIMs were characterized by atomic force microscope (AFM), scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR). Moreover, the performance of the membranes was evaluated by determining and interpreting the rejection (%), flux (F), permeability coefficient (P), permselectivity factor ( α ' PCB/DDT or anthracene ), and enrichment factors of PCBs, dichlorodiphenyltrichloroethane (p,p'-DDT), and anthracene from model contaminated water using the dead-end filtration cell. Molecularly imprinted membrane prepared with 18 wt% PSf and 20 wt% MIP 4 exhibited a well-defined porous structure, which was accompanied by enhanced PCB enrichment. Furthermore, molecularly imprinted membrane showed good enrichment factors for PCBs even from spiked natural water samples of Hartbeespoort dam.

Graphene quantum dot synthesis using nanosecond laser pulses and its comparison to Methylene Blue

NASA Astrophysics Data System (ADS)

Kholikov, Khomidkhodza; Thomas, Zachary; Seyitliyev, Dovletgeldi; Smith, Skylar

A biocompatible photodynamic therapy agent that generates a high amount of singlet oxygen with high water dispersibility and excellent photostability is desirable. In this work, a graphene based biomaterial which is a promising alternative to a standard photosensitizers was produced. Methylene blue was used as a reference photosensitizer. Bacteria deactivation by methylene blue was shown to be inhibited inside human blood due to protein binding. Graphene quantum dots (GQD) were synthesized by irradiating benzene and nickel oxide mixture using nanosecond laser pulses. High resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy, and nuclear magnetic resonance (NMR) were used for characterization of GQDs. Initial results show graphene quantum dots whose size less than 5 nm were successfully obtained. UV-VIS spectra shows absorption peak around 310 nm. The results of these studies can potentially be used to develop therapies for the eradication of pathogens in open wounds, burns, or skin cancers. New therapies for these conditions are particularly needed when antibiotic-resistant infections are present. NIH KBRIN.

Preparation and characterization of iron oxide magnetic nanoparticles functionalized by nisin.

PubMed

Gruskiene, Ruta; Krivorotova, Tatjana; Staneviciene, Ramune; Ratautas, Dalius; Serviene, Elena; Sereikaite, Jolanta

2018-05-08

Nisin is a known bacteriocin approved as a food additive for food preservation. It exhibits a wide spectrum antimicrobial activity against Gram-positive bacteria. Iron oxide magnetic nanoparticles were synthesized and characterized by X-ray diffraction method. A main part of iron oxide nanoparticles was found to be maghemite though a small quantity of magnetite could also be present. Magnetic nanoparticles were stabilized by citric, ascorbic, gallic or glucuronic acid coating. Stable iron oxide magnetic nanoparticles were functionalized by nisin using a simple and low cost adsorption method. Nisin loading was confirmed by FT-IR spectra, thermogravimetric analysis, dynamic light scattering and atomic force microscopy methods. Nisin-loaded iron oxide magnetic nanoparticles were stable at least six weeks as judged by the measurements of zeta-potential and hydrodynamic diameter. The antimicrobial activity of nisin-loaded iron oxide magnetic nanoparticles was demonstrated toward Gram-positive bacteria. Functionalized nanoparticles could therefore find the application as antimicrobials in innovative and emerging technologies based on the magnetic field. Copyright © 2018 Elsevier B.V. All rights reserved.

Bark extract mediated green synthesis of silver nanoparticles: Evaluation of antimicrobial activity and antiproliferative response against osteosarcoma.

PubMed

Nayak, Debasis; Ashe, Sarbani; Rauta, Pradipta Ranjan; Kumari, Manisha; Nayak, Bismita

2016-01-01

In the current investigation we report the biosynthesis potentials of bark extracts of Ficus benghalensis and Azadirachta indica for production of silver nanoparticle without use of any external reducing or capping agent. The appearance of dark brown color indicated the complete nanoparticle synthesis which was further validated by absorbance peak by UV-vis spectroscopy. The morphology of the synthesized particles was characterized by Field emission- scanning electron microscopy (Fe-SEM) and atomic force microscopy (AFM). The X-ray diffraction (XRD) patterns clearly illustrated the crystalline phase of the synthesized nanoparticles. ATR-Fourier Transform Infrared (ATR-FTIR) spectroscopy was performed to identify the role of various functional groups in the nanoparticle synthesis. The synthesized nanoparticles showed promising antimicrobial activity against Gram negative (Escherichia coli, Pseudomonas aeruginosa and Vibrio cholerae) and Gram positive (Bacillus subtilis) bacteria. The synthesized nano Ag also showed antiproliferative activity against MG-63 osteosarcoma cell line in a dose dependent manner. Thus, these synthesized Ag nanoparticles can be used as a broad spectrum therapeutic agent against osteosarcoma and microorganisms. Copyright © 2015 Elsevier B.V. All rights reserved.

Changes of the surface structure of corn stalk in the cooking process with active oxygen and MgO-based solid alkali as a pretreatment of its biomass conversion.

PubMed

Pang, Chunsheng; Xie, Tujun; Lin, Lu; Zhuang, Junping; Liu, Ying; Shi, Jianbin; Yang, Qiulin

2012-01-01

This study presents a novel, efficient and environmentally friendly process for the cooking of corn stalk that uses active oxygen (O2 and H2O2) and a recoverable solid alkali (MgO). The structural changes on the surface of corn stalk before and after cooking were characterized by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) techniques. The results showed that lignin and extractives were effectively removed, especially those on the surface of corn stalk. Additionally, the changes included becoming fibrillar, the exposure of cellulose and hemi-cellulose and the pitting corrosion on the surface, etc. The results also showed that the removal reaction is from outside to inside, but the main reaction is possibly on the surface. Furthermore, the results of active oxygen cooking with a solid alkali are compared with those of alkaline cooking in the paper. Copyright © 2011 Elsevier Ltd. All rights reserved.

Decoration of gold nanoparticles on thin multiwall carbon nanotubes and their use as a glucose sensor

NASA Astrophysics Data System (ADS)

Gangwar, Rajesh K.; Dhumale, Vinayak A.; Date, Kalyani S.; Alegaonkar, Prashant; Sharma, Rishi B.; Datar, Suwarna

2016-03-01

Thin multiwall carbon nanotubes (MWCNTs) have been decorated with gold nanoparticles (Au NPs) with polyaniline (PANI) as an inter-linker by a simple wet chemical method. The synthesized AuNPs:MWCNT:PANI composite was studied with UV-vis, FTIR, Raman spectroscopy, x-ray diffractometer, transmission electron microscopy (TEM) and atomic force microscopy (AFM). Conducting AFM (C-AFM) images of the composite reveal the role played by the two components in electrochemical reactions. The size of the Au NPs was found to be 13 ± 2 nm in the composite as observed from TEM. The synthesized AuNPs:MWCNT:PANI composite was further drop casted onto a glassy carbon electrode (GCE) for electrocatalytic study. The resulting composite exhibits good electrocatalytic activity towards reduction of H2O2 and O2. A glucose biosensor was developed by immobilizing glucose oxidase into AuNPs:MWCNT:PANI composite film on GCE. The fabricated sensor demonstrates good linear response to glucose (i.e. R = 0.9975) in the range of 2 to 12 mM.

Rheological and structural characterisation of film-forming solutions and biodegradable edible film made from kefiran as affected by various plasticizer types.

PubMed

Ghasemlou, Mehran; Khodaiyan, Faramarz; Oromiehie, Abdulrasoul

2011-11-01

The rheological properties of kefiran film-forming solutions, as well as the structural characterisation of the resulting films, were investigated as a function of various plasticizer types. The behaviours of the storage (G') and loss (G″) moduli as a function of frequency were typical of gel-like material, with the G' higher than the G″. Kefiran-based films, which may find application as edible films, were prepared by a casting and solvent-evaporation method. Possible interaction between the adjacent chains in the kefiran polymer and various plasticizers was proven by Fourier-transform infrared spectroscopy (FT-IR). The crystallinity of plasticized kefiran film was also analysed using X-ray diffraction (XRD); this revealed an amorphous-crystalline structure. These results were explained by the film's microstructure, which was analysed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The present study has helped determine possible interactions of kefiran, plasticizer and water molecules in determining film properties. Copyright © 2011 Elsevier B.V. All rights reserved.

Tribological properties of epoxy composite coatings reinforced with functionalized C-BN and H-BN nanofillers

NASA Astrophysics Data System (ADS)

Yu, Jingjing; Zhao, Wenjie; Wu, Yinghao; Wang, Deliang; Feng, Ruotao

2018-03-01

A series of epoxy resin (EP) composite coatings reinforced with functionalized cubic boron nitride (FC-BN) and functionalized hexagonal boron nitride (FH-BN) were fabricated successfully on 316L stainless steel by hand lay-up technique. The structure properties were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The morphologies were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Moreover, UMT-3 tribometer and surface profiler were used to investigate tribological behaviors of as-prepared composite coatings under dry friction and seawater conditions respectively. The results demonstrated that the presence of FC-BN or FH-BN fillers could greatly decrease the friction coefficient (COF) and wear rate of epoxy, in addition, composite coatings possess better tribological properties under seawater condition which was attributed to the lubricating effect of seawater. Moreover, FC-BN endows the composite coatings the highest wear resistance, and FH-BN /EP composite coatings exhibited the best friction reduction performance which is attributed to the self-lubricating performance of lamella structure for FH-BN sheet.

Evaluations of imidazolium ionic liquids as novel skin permeation enhancers for drug transdermal delivery.

PubMed

Zhang, Ding; Wang, Huai-Ji; Cui, Xiu-Ming; Wang, Cheng-Xiao

2017-06-01

In this work, imidazolium ionic liquids (imidazolium ILs) were employed as the novel chemical permeation enhancers (CPEs) and their performances and mechanisms of action were deeply investigated. Testosterone was used as a model drug to investigate the transdermal delivery enhancement of twenty imdidazolium ILs. The results suggested that the promotion activity connected to the structure and composition of the ILs. The quantitative structure-activity relationship (QSAR) model revealed a good linearity between the electronic properties of ILs and their enhancements. Furthermore, the transepidermal water loss (TEWL) and scanning laser confocal microscope (CLSM) examinations showed the strong improvement of ILs on skin barrier permeability, which were well correlated with the drug penetration profiles. The total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and atomic force microscope (AFM) evaluations of skins indicated that the ILs can disrupt the regular and compact arrangements of the corneocytes, change the surface properties of stratum corneum, and make the skin structure more permeable. Our work demonstrated the significant skin permeation promotion profiles of the imidazolium ILs, which are of great potential in transdermal drug delivery systems.

Preparation and performance evaluation of novel alkaline stable anion exchange membranes

NASA Astrophysics Data System (ADS)

Irfan, Muhammad; Bakangura, Erigene; Afsar, Noor Ul; Hossain, Md. Masem; Ran, Jin; Xu, Tongwen

2017-07-01

Novel alkaline stable anion exchange membranes are prepared from various amounts of N-methyl dipicolylamine (MDPA) and brominated poly (2,6-dimethyl-1,4-phenylene oxide) (BPPO). The dipicolylamine and MDPA are synthesized through condensation reaction and confirmed by 1H NMR spectroscopy. The morphologies of prepared membranes are investigated by atomic force microscopy (AFM), fourier transform infrared spectroscopy (FTIR), 1H NMR spectroscopy and scanning electron microscopy (SEM). The electrochemical and physical properties of AEMs are tested comprising water uptake (WU), ion exchange capacity (IEC), alkaline stability, linear expansion ratio (LER), thermal stability and mechanical stability. The obtained hydroxide conductivity of MDPA-4 is 66.5 mS/cm at 80 °C. The MDPA-4 membrane shows good alkaline stability, high hydroxide conductivity, low methanol permeability (3.43 × 10-7 cm2/s), higher selectivity (8.26 × 107 mS s/cm3), less water uptake (41.1%) and lower linear expansion (11.1%) despite of high IEC value (1.62 mmol/g). The results prove that MDPA membranes have great potential application in anion exchange membrane fuel cell.

Intensifying radiation induced grafting of 4-vinylpyridine/glycidyl methacrylate mixtures onto poly(ethylene-co-tetrafluoroethylene) films using ultrasound

NASA Astrophysics Data System (ADS)

Nasef, Mohamed Mahmoud; Sithambaranathan, Paveswari; Ahmad, Arshad; Abouzari-lotf, Ebrahim

2017-05-01

A new ultrasound-aided method was used to enhance grafting of 4-vinylpyridine (4-VP) and glycidyl methacrylate (GMA) monomers mixtures onto electron beam (EB) irradiated poly(ethylene-co-tetrafluoroethylene) (ETFE) film for the first time. The effects of reaction parameters such as absorbed dose, monomer concentration, reaction time on both of degree of grafting (DG) and grafting efficiency (GE) were investigated under sonication and conventional grafting at similar temperatures. Fourier transform infrared (FTIR) and atomic force microscopy (AFM) were used to monitor the impact of the applied ultrasound on composition and surfaces of the grafted films whereas 1H-NMR was used to investigate composition of the grafting residues. The ultrasound-aided grafting of 4-VP/GMA was found to enhance both of DG% and GE remarkably. Moreover, it produced grafted ETFE films having smoother surfaces without homopolymer contamination compared to grafted films obtained from conventional grafting. The results of this study suggest that the use of ultrasound is a promising way for intensifying grafting process and improving its economy.

Characterization of Bonding Between Poly(dimethylsiloxane) and Cyclic Olefin Coplymer Using Corona Discharge Induced Grafting Polymerization

PubMed Central

Liu, Ke; Gu, Pan; Hamaker, Kiri; Fan, Z. Hugh

2011-01-01

Thermoplastics have been increasingly used for fabricating microfluidic devices because of their low cost, mechanical/biocompatible attributes, and well-established manufacturing processes. However, there is sometimes a need to integrate such a device with components made from other materials such as polydimethylsiloxane (PDMS). Bonding thermoplastics with PDMS to produce hybrid devices is not straightforward. We have reported our method to modify the surface property of a cyclic olefin copolymer (COC) substrate by using corona discharge and grafting polymerization of 3-(trimethoxysilyl)propyl methacrylate; the modified surface enabled strong bonding of COC with PDMS. In this paper, we report our studies on the surface modification mechanism using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and contact angle measurement. Using this bonding method, we fabricated a three-layer (COC/PDMS/COC) hybrid device consisting of elastomer-based valve arrays. The microvalve operation was confirmed through the displacement of a dye solution in a fluidic channel when the elastomer membrane was pneumatically actuated. Valve-enabled microfluidic handling was demonstrated. PMID:21962541

Effect of nitrogen doping on structural, morphological, optical and electrical properties of radio frequency magnetron sputtered zinc oxide thin films

NASA Astrophysics Data System (ADS)

Perumal, R.; Hassan, Z.

2016-06-01

Zinc oxide receives remarkable attention due to its several attractive physical properties. Zinc oxide thin films doped with nitrogen were grown by employing RF magnetron sputtering method at room temperature. Doping was accomplished in gaseous medium by mixing high purity nitrogen gas along with argon sputtering gas. Structural studies confirmed the high crystalline nature with c-axis oriented growth of the nitrogen doped zinc oxide thin films. The tensile strain was developed due to the incorporation of the nitrogen into the ZnO crystal lattice. Surface roughness of the grown films was found to be decreased with increasing doping level was identified through atomic force microscope analysis. The presenting phonon modes of each film were confirmed through FTIR spectral analysis. The increasing doping level leads towards red-shifting of the cut-off wavelength due to decrement of the band gap was identified through UV-vis spectroscopy. All the doped films exhibited p-type conductivity was ascertained using Hall measurements and the obtained results were presented.

The Barrier Properties of PET Coated DLC Film Deposited by Microwave Surface-Wave PECVD

NASA Astrophysics Data System (ADS)

Yin, Lianhua; Chen, Qiang

2017-12-01

In this paper we report the investigation of diamond-like carbon (DLC) deposited by microwave surface-wave plasma enhanced chemical vapor deposition (PECVD) on the polyethylene terephthalate (PET) web for the purpose of the barrier property improvement. In order to characterize the properties of DLC coatings, we used several substrates, silicon wafer, glass, and PET web and KBr tablet. The deposition rate was obtained by surface profiler based on the DLC deposited on glass substrates; Fourier transform infrared spectroscope (FTIR) was carried out on KBr tablets to investigate chemical composition and bonding structure; the morphology of the DLC coating was analyzed by atomic force microscope (AFM) on Si substrates. For the barrier properties of PET webs, we measured the oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) after coated with DLC films. We addressed the film barrier property related to process parameters, such as microwave power and pulse parameter in this work. The results show that the DLC coatings can greatly improve the barrier properties of PET webs.

Incorporation of bentonite clay in cassava starch films for the reduction of water vapor permeability.

PubMed

Monteiro, M K S; Oliveira, V R L; Santos, F K G; Barros Neto, E L; Leite, R H L; Aroucha, E M M; Silva, R R; Silva, K N O

2018-03-01

Complete factorial planning 2 3 was applied to identify the influence of the cassava starch(A), glycerol(B) and modified clay(C) content on the water vapor permeability(WVP) of the cassava starch films with the addition of bentonite clay as a filler, its surface was modified by ion exchange from cetyltrimethyl ammonium bromide. The films were characterized by X-ray diffraction(XRD), fourier transform by infrared radiation(FTIR), atomic force microscopy(AFM) and scanning electron microscopy(SEM). The factorial analysis suggested a mathematical model thats predicting the optimal condition of the minimization of WVP. The influence of each individual factor and interaction in the WVP was investigated by Pareto graph, response surface and the optimization was established by the desirability function. The sequence of the degree of statistical significance of the investigated effects on the WVP observed in the Pareto graph was C>B>A>BC>AC. Interactions AB, BC and AC showed that the modified clay was the factor of greater significance. Copyright © 2017 Elsevier Ltd. All rights reserved.

N/Fe-TiO2 doped nanoparticles loaded on bentonite for increased photocatalytic activity for the degradation of organic pollutants

NASA Astrophysics Data System (ADS)

Espenilla, Mel Bryan L.; Magyaya, Ryan Carl S.; Conato, Marlon T.

2018-05-01

Photocatalyst materials based on Philippine bentonite-titanium oxide composites and their ability to degrade organic pollutants is reported. Nanosized-titanium dioxide (TiO2) was synthesized by sol-gel method from titanium tetraisopropoxide. This was then incorporated in the Philippine bentonite via hydrothermal methods. In order to shift the absorbance of the TiO2 to the visible region doping was done using iron and nitrogen ions. The hydrodynamic radius of the synthesized TiO2 was analyzed using a zeta-sizer and was found to be around 70 nm. The photocatalytic efficiency of the TiO2/bentonite, N-TiO2/bentonite, Fe-TiO2/bentonite and N-Fe-TiO2/bentonite was evaluated using a photocatalytic reactor. It was found out that the N-Fe-TiO2/bentonite to be the most efficient with 22% degradation of the model pollutant after 80 minutes. FT-IR analysis was done to determine the bonding of the different components. Scanning electron microscopy and atomic force microscopy analysis was also performed to characterize the products.

Effect of various pH values, ionic strength, and temperature on papain hydrolysis of salivary film.

PubMed

Yao, Jiang-Wu; Xiao, Yin; Lin, Feng

2012-04-01

Stimulated human whole saliva (WS) was used to study the dynamics of papain hydrolysis at defined pH, ionic strength, and temperature with the view of reducing an acquired pellicle. A quartz crystal microbalance with dissipation (QCM-D) was used to monitor the changes in frequency caused by enzyme hydrolysis of WS films, and the hydrolytic parameters were calculated using an empirical model. The morphological and conformational changes of the salivary films before and after enzymatic hydrolysis were characterized by atomic force microscopy (AFM) imaging and grazing-angle Fourier transform infrared (GA-FTIR ) spectra, respectively. The characteristics of papain hydrolysis of WS films were pH-, ionic strength-, and temperature-dependent. The WS films were partially removed by the action of papain, resulting in thinner and smoother surfaces. The infrared data suggested that hydrolysis-induced deformation did not occur on the remnants of salivary films. The processes of papain hydrolysis of WS films can be controlled by properly regulating pH, ionic strength, and temperature. © 2012 Eur J Oral Sci.

Novel amphiphilic poly(dimethylsiloxane) based polyurethane networks tethered with carboxybetaine and their combined antibacterial and anti-adhesive property

NASA Astrophysics Data System (ADS)

Jiang, Jingxian; Fu, Yuchen; Zhang, Qinghua; Zhan, Xiaoli; Chen, Fengqiu

2017-08-01

The traditional nonfouling materials are powerless against bacterial cells attachment, while the hydrophobic bactericidal surfaces always suffer from nonspecific protein adsorption and dead bacterial cells accumulation. Here, amphiphilic polyurethane (PU) networks modified with poly(dimethylsiloxane) (PDMS) and cationic carboxybetaine diol through simple crosslinking reaction were developed, which had an antibacterial efficiency of 97.7%. Thereafter, the hydrolysis of carboxybetaine ester into zwitterionic groups brought about anti-adhesive properties against bacteria and proteins. The surface chemical composition and wettability performance of the PU network surfaces were investigated by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and contact angle analysis. The surface distribution of PDMS and zwitterionic segments produced an obvious amphiphilic heterogeneous surface, which was demonstrated by atomic force microscopy (AFM). Enzyme-linked immunosorbent assays (ELISA) were used to test the nonspecific protein adsorption behaviors. With the advantages of the transition from excellent bactericidal performance to anti-adhesion and the combination of fouling resistance and fouling release property, the designed PDMS-based amphiphilic PU network shows great application potential in biomedical devices and marine facilities.

Use of green chemistry methods in the extraction of dietary fibers from cactus rackets (Opuntia ficus indica): Structural and microstructural studies.

PubMed

Cheikh Rouhou, Marwa; Abdelmoumen, Souhir; Thomas, Sabu; Attia, Hamadi; Ghorbel, Dorra

2018-05-23

This work aims to compare the development of three green chemistry methods in the extraction of cactus (Opuntia ficus indica) dietary fibers. The influence of extraction conditions (solvent nature: water, lemon juice and ethanol; extraction process: maceration and steam explosion; extraction time: 30 min, 1 h, 3 h, 5 h) on the chemical and structural composition was studied. Fourier Transform Infrared (FTIR) spectroscopy proved that all treatments do not affect the cellulose structure and could induce the reduction of hemicelluloses and lignin content. The steam treatment with lemon juice was the best treatment in term of quality of the fibers extracted. Through X-ray Diffraction (XRD) analysis, it was demonstrated that this treatment contributed to the destruction of the amorphous phase with preservation of the crystalline phase. Scanning electron microscopy (SEM) showed that the microstructure of the sample surface was uniform and contains arranged fibers. Atomic Force Microscopy (AFM) revealed fibers with 80 nm of diameter. Copyright © 2018. Published by Elsevier B.V.

Intercalated chitosan/hydroxyapatite nanocomposites: Promising materials for bone tissue engineering applications.

PubMed

Nazeer, Muhammad Anwaar; Yilgör, Emel; Yilgör, Iskender

2017-11-01

Preparation and characterization of chitosan/hydroxyapatite (CS/HA) nanocomposites displaying an intercalated structure is reported. Hydroxyapatite was synthesized through sol-gel process. Formic acid was introduced as a new solvent to obtain stable dispersions of nano-sized HA particles in polymer solution. CS/HA dispersions with HA contents of 5, 10 and 20% by weight were prepared. Self-assembling of HA nanoparticles during the drying of the solvent cast films led to the formation of homogeneous CS/HA nanocomposites. Composite films were analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-rays (EDX) analysis, Fourier transform infrared (FTIR) spectroscopy, X-rays diffraction (XRD) analysis and thermogravimetric analysis (TGA). SEM and AFM confirmed the presence of uniformly distributed HA nanoparticles on the chitosan matrix surface. XRD patterns and cross-sectional SEM images showed the formation of layered nanocomposites. Complete degradation of chitosan matrix in TGA experiments, led to the formation of nanoporous 3D scaffolds containing hydroxyapatite, β-tricalcium phosphate and calcium pyrophosphate. CS/HA composites can be considered as promising materials for bone tissue engineering applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

Structural characterization of a novel glucan from Achatina fulica and its antioxidant activity.

PubMed

Liao, Ningbo; Chen, Shiguo; Ye, Xingqian; Zhong, Jianjun; Ye, Xuan; Yin, Xinzi; Tian, Jenny; Liu, Donghong

2014-03-19

A novel glucan designated AFPS-IB was purified from Achatina fulica (China white jade snail) by anion-exchange and gel-permeation chromatography. Chemical composition analysis indicated AFPS-IB was composed of glucose, fucose, rhamnose, mannose, and galactose in a molar ratio of 189:2:1:1:2 and with an average molecular weight of 128 kDa. Its structural characteristics were investigated by Fourier transform infrared spectroscopy (FTIR), high performance liquid chromatography (HPLC), gas chromatography mass spectrometry (GC-MS), methylation analysis, nuclear magnetic resonance (NMR) spectroscopy ((1)H,( 13)C, H-H COSY, HSQC, TOCSY, and NOESY), and atomic force microscopy (AFM). The glucan mainly consisted of a backbone of repeating (1→4)-α-d-glucose residues with (1→6)-β-d glucosyl branches at random points on the backbone glucose. Antioxidant studies revealed AFPS-IB showed significant DPPH (2,2-diphenyl-1-picrylhydrazyl) radical, superoxide anion (O2(-)) scavenging activities and high reduction potential. This study suggested that AFPS-IB could be a new source of dietary antioxidants.

Excimer laser assisted very fast exfoliation and reduction of graphite oxide at room temperature under air ambient for Supercapacitors electrode

NASA Astrophysics Data System (ADS)

Malek Hosseini, S. M. B.; Baizaee, S. M.; Naderi, Hamid Reza; Dare Kordi, Ali

2018-01-01

Excimer laser was used for reduction and exfoliation of graphite oxide (GO) at room temperature under air ambient. The prepared excimer laser reduced graphite oxide (XLRGO) is characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), nitrogen adsorption/desorption (BET method), X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and UV-vis absorption techniques for surface, structural functional groups and band gap analysis. Electrochemical properties are investigated using cyclic voltammetry, galvanostatic charge-discharge, electrochemical impedance spectroscopy (EIS) and continues cyclic voltammetry (CCV) in 0.5 M Na2SO4 as electrolyte. Electrochemical investigations revealed that XLRGO electrode has enhanced supercapacitive performance including specific capacitance of 299 F/g at a scan rate of 2 mV/s. Furthermore, CCV measurement showed that XLRGO electrode kept 97.8% of its initial capacitance/capacity after 4000 cycles. The obtained results from electrochemical investigations confirm that the reduction of GO by using an excimer laser produces high-quality graphene for supercapacitor applications without the need for additional operations.

A novel passivation process of silicon nanowires by a low-cost PECVD technique for deposition of hydrogenated silicon nitride using SiH4 and N2 as precursor gases

NASA Astrophysics Data System (ADS)

Bouaziz, Lamia; Dridi, Donia; Karyaoui, Mokhtar; Angelova, Todora; Sanchez Plaza, Guillermo; Chtourou, Radhouane

2017-03-01

In this work, a different SiNx passivation process of silicon nanowires has been opted for the deposition of a hydrogenated silicon nitride (SiNx:H) by a low-cost plasma enhanced chemical vapor deposition (PECVD) using silane ( SiH4 and nitrogen ( N2 as reactive gases. This study is focused on the effect of the gas flow ratio on chemical composition, morphological, optical and optoelectronic properties of silicon nanowires. The existence of Si-N and Si-H bonds was proven by the Fourier transmission infrared (FTIR) spectrum. Morphological structures were shown by scanning electron microscopy (SEM), and the roughness was investigated by atomic force microscopy (AFM). A low reflectivity less than 6% in the wavelength range 250-1200nm has been shown by UV-visible spectroscopy. Furthermore, the thickness and the refractive index of the passivation layer is determined by ellipsometry measurements. As a result, an improvement in minority carrier lifetime has been obtained by reducing surface recombination of silicon nanowires.

Gum tragacanth stabilized green gold nanoparticles as cargos for Naringin loading: A morphological investigation through AFM.

PubMed

Rao, Komal; Imran, Muhammad; Jabri, Tooba; Ali, Imdad; Perveen, Samina; Shafiullah; Ahmed, Shakil; Shah, Muhammad Raza

2017-10-15

Gold nanoparticles (AuNPs) have attracted greater scientific interests for the construction of drugs loading cargos due to their biocompatibility, safety and facile surface modifications. This study deals with the fabrication of gum tragacanth (GT) green AuNPs as carrier for Naringin, a less water soluble therapeutic molecule. The optimized AuNPs were characterized through UV-vis spectroscopy, FT-IR and atomic force microscope (AFM). Naringin loaded nanoparticles were investigated for their bactericidal potentials using Tetrazolium Microplate assay. Morphological studies conducted via AFM revealed spherical shape for AuNPs with nano-range size and stabilized by GT multi-functional groups. The AuNPs acted as carrier for increased amount of Naringin. Upon loading in AuNPs, Naringin An increased in the bactericidal potentials of Naringin was observed after loading on AuNPs against various tested bacterial strains. This was further authenticated by the surface morphological analysis, showing enhanced membrane destabilizing effects of loaded Naringin. The results suggest that GT stabilized green AuNPs can act as effective delivery vehicles for enhancing bactericidal potentials of Naringin. Copyright © 2017 Elsevier Ltd. All rights reserved.

Preparation and characterization of PVP-PVA–ZnO blend polymer nano composite films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Divya, S., E-mail: divi.fysics@gmail.com; Saipriya, G.; Hemalatha, J., E-mail: hemalatha@nitt.edu

Flexible self-standing films of PVP-PVA blend composites are prepared by using ZnO as a nano filler at different concentrations. The structural, compositional, morphological and optical studies made with the help of X-ray diffraction (XRD), Fourier Transform Infra-Red spectroscopy (FTIR), Scanning electron microscope (SEM), Atomic Force Microscopy (AFM), Ultraviolet-visible spectroscopy (UV-vis) and Photoluminescence (PL) spectra are presented in this paper. The results of XRD indicate that ZnO nanoparticles are formed with hexagonal phase in the polymeric matrix. SEM images show the dispersion of ZnO nano filler in the polymer matrix. UV–vis spectra reveal that the absorption peak is centered around 235more » nm and 370 nm for the nano composite films. The blue shift is observed with decrease in the concentration of the nano filler. PL spectra shows the excitation wavelength is given at 320 nm.The emission peaks were observed at 383 nm ascribing to the electronic transitions between valence band and conduction band and the peak at 430 nm.« less

Graphene oxide nanoplatforms to enhance catalytic performance of iron phthalocyanine for oxygen reduction reaction in bioelectrochemical systems

NASA Astrophysics Data System (ADS)

Costa de Oliveira, Maida Aysla; Mecheri, Barbara; D'Epifanio, Alessandra; Placidi, Ernesto; Arciprete, Fabrizio; Valentini, Federica; Perandini, Alessando; Valentini, Veronica; Licoccia, Silvia

2017-07-01

We report the development of electrocatalysts based on iron phthalocyanine (FePc) supported on graphene oxide (GO), obtained by electrochemical oxidation of graphite in aqueous solution of LiCl, LiClO4, and NaClO4. Structure, surface chemistry, morphology, and thermal stability of the prepared materials were investigated by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, atomic force microscopy (AFM), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The catalytic activity toward oxygen reduction reaction (ORR) at neutral pH was evaluated by cyclic voltammetry. The experimental results demonstrate that the oxidation degree of GO supports affects the overall catalytic activity of FePc/GO, due to a modulation effect of the interaction between FePc and the basal plane of GO. On the basis of electrochemical, spectroscopic, and morphological investigations, FePc/GO_LiCl was selected to be assembled at the cathode side of a microbial fuel cell prototype, demonstrating a good electrochemical performance in terms of voltage and power generation.

Thermally induced alkylation of diamond.

PubMed

Hoeb, Marco; Auernhammer, Marianne; Schoell, Sebastian J; Brandt, Martin S; Garrido, Jose A; Stutzmann, Martin; Sharp, Ian D

2010-12-21

We present an approach for the thermally activated formation of alkene-derived self-assembled monolayers on oxygen-terminated single and polycrystalline diamond surfaces. Chemical modification of the oxygen and hydrogen plasma-treated samples was achieved by heating in 1-octadecene. The resulting layers were characterized using X-ray photoelectron spectroscopy, thermal desorption spectroscopy, atomic force microscopy, Fourier transform infrared spectroscopy, and water contact angle measurements. This investigation reveals that alkenes selectively attach to the oxygen-terminated sites via covalent C-O-C bonds. The hydrophilic oxygen-terminated diamond is rendered strongly hydrophobic following this reaction. The nature of the process limits the organic layer growth to a single monolayer, and FTIR measurements reveal that such monolayers are dense and well ordered. In contrast, hydrogen-terminated diamond sites remain unaffected by this process. This method is thus complementary to the UV-initiated reaction of alkenes with diamond, which exhibits the opposite reactivity contrast. Thermal alkylation increases the range of available diamond functionalization strategies and provides a means of straightforwardly forming single organic layers in order to engineer the surface properties of diamond.

Crosslinkable coatings from phosphorylcholine-based polymers.

PubMed

Lewis, A L; Cumming, Z L; Goreish, H H; Kirkwood, L C; Tolhurst, L A; Stratford, P W

2001-01-01

2-Methacryloyloxyethyl phosphorylcholine (MPC) was synthesised and then used in the preparation of crosslinked polymer membranes with lauryl methacrylate, hydroxypropyl methacrylate and trimethoxysilylpropyl methacrylate (crosslinker) comonomers. Some physical aspects of the membrane properties were evaluated in order to establish the basis for the synthesis of a series of post-crosslinkable polymers. These materials were made by copolymerisation of the constituent monomers via a free radical method, and characterised using NMR, FT-IR, viscometry and elemental analysis. The optimum crosslink density and conditions required for curing coatings of these polymers were investigated using atomic force microscopy (AFM) and showed the inclusion of 5 mol% silyl crosslinking agent to be ideal. A nanoindentation technique was employed to determine if the coating developed elasticity upon crosslinking. The biological properties of the coatings were evaluated using a variety of protein adsorption assays and blood contacting experiments, and an enzyme immunoassay was developed to detect E. coli in order to assess the level of bacterial adhesion to these biomaterials. Polymers of this type were shown to be very useful as coating materials for improving the biocompatibility of, or reducing the levels of adherent bacteria to medical devices.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teka, S.; Gaied, A.; Jaballah, N.

Highlights: • Microwave-assisted synthesis of rotaxane based on anthracene and β-cyclodextrin. • Morphological and optical characterization of thin solid film. • Elaboration of impedimetric gold/rotaxane sensor. • Investigation of the membrane sensitivity towards Hg{sup 2+}, Cu{sup 2+} and Pb{sup 2+} cations. - Abstract: An impedimetric sensor based on a new semi-conducting rotaxane has been described for detection of toxic cations. The rotaxane, consists on a π-conjugated material encapsulated into β-cyclodextrin (β-CD); it has been synthesized via the Williamson reaction under microwaves irradiation. The supramolecular structure of the compound was confirmed by NMR and FT-IR spectroscopies. A thin solid film ofmore » the rotaxane was deposited by spin-coating to develop a new electrochemical sensor. The morphological properties of the organic membrane were evaluated using contact angle measurements and atomic force microscopy. The gold/rotaxane/solution interfaces were investigated by electrochemical impedance spectroscopy and the obtained data were fitted using an equivalent electrical circuit. The response of the gold/rotaxane membrane towards Hg{sup 2+}, Cu{sup 2+} and Pb{sup 2+} cations was studied and the results showed a good sensitivity to the mercury cations.« less

Device level optimization of poly(vinylidene fluoride-trifluoroethylene)–zinc oxide polymer nanocomposite thin films for ferroelectric applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

C K, Subash, E-mail: cksubash08@gmail.com; Valiyaneerilakkal, Uvais; Varghese, Soney

Polymer nanocomposite was prepared using poly(vinylidene fluoride-trifluoroethylene) and zinc oxide (ZnO) nanopowder, which are ferroelectric in nature. Nanocomposite was prepared in various concentrations(0.2, 0.4, 0.8, and 1 wt. %) using probe ultra-sonication, followed by spin coating and annealing at 120 °C for 2 h to improve the formation of β-phase. Metal-ferroelectric-metal capacitor was fabricated using this optimized thin film as a ferroelectric layer. Device level optimization was carried out by polarization-electric field (P-E) hysteresis studies of this film, which shows polarization enhancement of composite. Various characterization techniques like atomic force microscopy, Fourier transform infra-red spectroscopy (FT-IR), Differential scanning calorimetry, and X-ray diffractionmore » were used to study the β-phase formation of nancomposite. The capacitance–voltage (C-V) and current-voltage (I-V) characteristics were studied through varying frequency and temperature. C-V measurements show an increase of 79% in the capacitance of polymer nanocomposite, which can be used for the fabrication of ferroelectric devices.« less

Gold nanoparticle incorporated polymer/bioactive glass composite for controlled drug delivery application.

PubMed

Jayalekshmi, A C; Sharma, Chandra P

2015-02-01

The present study discusses the development of a biodegradable polymer encapsulated-nanogold incorporated-bioactive glass composite (AuPBG) by a low-temperature method. The composite was analyzed by atomic force microscopy (AFM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetry (TG), fluorescence and dissolution analysis. The composite exhibited aggregation behaviour in solid and solution states and exhibited negative zeta potential (-13.3 ± 1.4 mV). The composite exhibited fast degradation starting from the 5(th) day onwards in phosphate buffered saline (PBS) for a period of 14 days. The composite showed fluorescence quenching effect at pH 7 and the fluorescence recovered at pH 5. The composite has been found to be suitable for the release of doxorubicin at high rates at acidic pH (∼ 5) which is the intracellular pH of tumour cells. The drug loading ratio is also high and it exhibited a controlled release for a period of 8 days in PBS. The system serves as a promising material for targeted drug delivery applications. Copyright © 2014 Elsevier B.V. All rights reserved.

Deposition of Zinc Oxide on Different Polymer Textiles and Their Antibacterial Properties.

PubMed

Fiedot-Toboła, Marta; Ciesielska, Magdalena; Maliszewska, Irena; Rac-Rumijowska, Olga; Suchorska-Woźniak, Patrycja; Teterycz, Helena; Bryjak, Marek

2018-04-30

A surface modification of polyamide 6 (PA), polyethylene terephthalate (PET) and polypropylene (PP) textiles was performed using zinc oxide to obtain antibacterial layer. ZnO microrods were synthesized on ZnO nanoparticles (NPs) as a nucleus centers by chemical bath deposition (CBD) process. Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) indicated that wurzite ZnO microrods were obtained on every sample. Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), Atomic Force Microscopy (AFM) and Liquid Absorption Capacity (LAC) analysis indicate that the amount and structure of antibacterial layer is dependent on roughness and wettability of textile surface. The rougher and more hydrophilic is the material, the more ZnO were deposited. All studied textiles show significant bactericidal activity against Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus ). A possible mechanism and difference in sensitivity between Gram-negative and Gram-positive bacteria to ZnO is discussed. Considering that antibacterial activity of ZnO is caused by Reactive Oxygen Species (ROS) generation, an influence of surface to volume ratio and crystalline parameters is also discussed.

Nonlinear Dynamics of Cantilever-Sample Interactions in Atomic Force Microscopy

NASA Technical Reports Server (NTRS)

Cantrell, John H.; Cantrell, Sean A.

2010-01-01

The interaction of the cantilever tip of an atomic force microscope (AFM) with the sample surface is obtained by treating the cantilever and sample as independent systems coupled by a nonlinear force acting between the cantilever tip and a volume element of the sample surface. The volume element is subjected to a restoring force from the remainder of the sample that provides dynamical equilibrium for the combined systems. The model accounts for the positions on the cantilever of the cantilever tip, laser probe, and excitation force (if any) via a basis set of set of orthogonal functions that may be generalized to account for arbitrary cantilever shapes. The basis set is extended to include nonlinear cantilever modes. The model leads to a pair of coupled nonlinear differential equations that are solved analytically using a matrix iteration procedure. The effects of oscillatory excitation forces applied either to the cantilever or to the sample surface (or to both) are obtained from the solution set and applied to the to the assessment of phase and amplitude signals generated by various acoustic-atomic force microscope (A-AFM) modalities. The influence of bistable cantilever modes of on AFM signal generation is discussed. The effects on the cantilever-sample surface dynamics of subsurface features embedded in the sample that are perturbed by surface-generated oscillatory excitation forces and carried to the cantilever via wave propagation are accounted by the Bolef-Miller propagating wave model. Expressions pertaining to signal generation and image contrast in A-AFM are obtained and applied to amplitude modulation (intermittent contact) atomic force microscopy and resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM). The influence of phase accumulation in A-AFM on image contrast is discussed, as is the effect of hard contact and maximum nonlinearity regimes of A-AFM operation.

Van der Waals forces in pNRQED

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shtabovenko, Vladyslav

2016-01-22

We report on the calculation of electromagnetic van der Waals forces [1] between two hydrogen atoms using non-relativistic effective field theories (EFTs) of QED for large and small momentum transfers with respect to the intrinsic energy scale of the hydrogen atom. Our results reproduce the well known London and Casimir-Polder forces.

Reconciling Structural and Thermodynamic Predictions Using All-Atom and Coarse-Grain Force Fields: The Case of Charged Oligo-Arginine Translocation into DMPC Bilayers

PubMed Central

2015-01-01

Using the translocation of short, charged cationic oligo-arginine peptides (mono-, di-, and triarginine) from bulk aqueous solution into model DMPC bilayers, we explore the question of the similarity of thermodynamic and structural predictions obtained from molecular dynamics simulations using all-atom and Martini coarse-grain force fields. Specifically, we estimate potentials of mean force associated with translocation using standard all-atom (CHARMM36 lipid) and polarizable and nonpolarizable Martini force fields, as well as a series of modified Martini-based parameter sets. We find that we are able to reproduce qualitative features of potentials of mean force of single amino acid side chain analogues into model bilayers. In particular, modifications of peptide–water and peptide–membrane interactions allow prediction of free energy minima at the bilayer–water interface as obtained with all-atom force fields. In the case of oligo-arginine peptides, the modified parameter sets predict interfacial free energy minima as well as free energy barriers in almost quantitative agreement with all-atom force field based simulations. Interfacial free energy minima predicted by a modified coarse-grained parameter set are −2.51, −4.28, and −5.42 for mono-, di-, and triarginine; corresponding values from all-atom simulations are −0.83, −3.33, and −3.29, respectively, all in units of kcal/mol. We found that a stronger interaction between oligo-arginine and the membrane components and a weaker interaction between oligo-arginine and water are crucial for producing such minima in PMFs using the polarizable CG model. The difference between bulk aqueous and bilayer center states predicted by the modified coarse-grain force field are 11.71, 14.14, and 16.53 kcal/mol, and those by the all-atom model are 6.94, 8.64, and 12.80 kcal/mol; those are of almost the same order of magnitude. Our simulations also demonstrate a remarkable similarity in the structural aspects of the ensemble of configurations generated using the all-atom and coarse-grain force fields. Both resolutions show that oligo-arginine peptides adopt preferential orientations as they translocate into the bilayer. The guiding theme centers on charged groups maintaining coordination with polar and charged bilayer components as well as local water. We also observe similar behaviors related with membrane deformations. PMID:25290376

Reconciling structural and thermodynamic predictions using all-atom and coarse-grain force fields: the case of charged oligo-arginine translocation into DMPC bilayers.

PubMed

Hu, Yuan; Sinha, Sudipta Kumar; Patel, Sandeep

2014-10-16

Using the translocation of short, charged cationic oligo-arginine peptides (mono-, di-, and triarginine) from bulk aqueous solution into model DMPC bilayers, we explore the question of the similarity of thermodynamic and structural predictions obtained from molecular dynamics simulations using all-atom and Martini coarse-grain force fields. Specifically, we estimate potentials of mean force associated with translocation using standard all-atom (CHARMM36 lipid) and polarizable and nonpolarizable Martini force fields, as well as a series of modified Martini-based parameter sets. We find that we are able to reproduce qualitative features of potentials of mean force of single amino acid side chain analogues into model bilayers. In particular, modifications of peptide-water and peptide-membrane interactions allow prediction of free energy minima at the bilayer-water interface as obtained with all-atom force fields. In the case of oligo-arginine peptides, the modified parameter sets predict interfacial free energy minima as well as free energy barriers in almost quantitative agreement with all-atom force field based simulations. Interfacial free energy minima predicted by a modified coarse-grained parameter set are -2.51, -4.28, and -5.42 for mono-, di-, and triarginine; corresponding values from all-atom simulations are -0.83, -3.33, and -3.29, respectively, all in units of kcal/mol. We found that a stronger interaction between oligo-arginine and the membrane components and a weaker interaction between oligo-arginine and water are crucial for producing such minima in PMFs using the polarizable CG model. The difference between bulk aqueous and bilayer center states predicted by the modified coarse-grain force field are 11.71, 14.14, and 16.53 kcal/mol, and those by the all-atom model are 6.94, 8.64, and 12.80 kcal/mol; those are of almost the same order of magnitude. Our simulations also demonstrate a remarkable similarity in the structural aspects of the ensemble of configurations generated using the all-atom and coarse-grain force fields. Both resolutions show that oligo-arginine peptides adopt preferential orientations as they translocate into the bilayer. The guiding theme centers on charged groups maintaining coordination with polar and charged bilayer components as well as local water. We also observe similar behaviors related with membrane deformations.

Synthesis and characterization of designed BMHP1-derived self-assembling peptides for tissue engineering applications

NASA Astrophysics Data System (ADS)

Silva, Diego; Natalello, Antonino; Sanii, Babak; Vasita, Rajesh; Saracino, Gloria; Zuckermann, Ronald N.; Doglia, Silvia Maria; Gelain, Fabrizio

2012-12-01

The importance of self-assembling peptides (SAPs) in regenerative medicine is becoming increasingly recognized. The propensity of SAPs to form nanostructured fibers is governed by multiple forces including hydrogen bonds, hydrophobic interactions and π-π aromatic interactions among side chains of the amino acids. Single residue modifications in SAP sequences can significantly affect these forces. BMHP1-derived SAPs is a class of biotinylated oligopeptides, which self-assemble in β-structured fibers to form a self-healing hydrogel. In the current study, selected modifications in previously described BMHP1-derived SAPs were designed in order to investigate the influence of modified residues on self-assembly kinetics and scaffold formation properties. The Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis demonstrated the secondary structure (β-sheet) formation in all modified SAP sequences, whereas atomic force microscopy (AFM) analysis further confirmed the presence of nanofibers. Furthermore, the fiber shape and dimension analysis by AFM showed flattened and twisted fiber morphology ranging from ~8 nm to ~70 nm. The mechanical properties of the pre-assembled and post assembled solution were investigated by rheometry. The shear-thinning behavior and rapid re-healing properties of the pre-assembled solutions make them a preferable choice for injectable scaffolds. The wide range of stiffnesses (G') -from ~1000 to ~27 000 Pa - exhibited by the post-assembled scaffolds demonstrated their potential for a variety of tissue engineering applications. The extra cellular matrix (ECM) mimicking (physically and chemically) properties of SAP scaffolds enhanced cell adhesion and proliferation. The capability of the scaffold to facilitate murine neural stem cell (mNSC) proliferation was evaluated in vitro: the increased mNSCs adhesion and proliferation demonstrated the potential of newly synthesized SAPs for regenerative medicine approaches.The importance of self-assembling peptides (SAPs) in regenerative medicine is becoming increasingly recognized. The propensity of SAPs to form nanostructured fibers is governed by multiple forces including hydrogen bonds, hydrophobic interactions and π-π aromatic interactions among side chains of the amino acids. Single residue modifications in SAP sequences can significantly affect these forces. BMHP1-derived SAPs is a class of biotinylated oligopeptides, which self-assemble in β-structured fibers to form a self-healing hydrogel. In the current study, selected modifications in previously described BMHP1-derived SAPs were designed in order to investigate the influence of modified residues on self-assembly kinetics and scaffold formation properties. The Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis demonstrated the secondary structure (β-sheet) formation in all modified SAP sequences, whereas atomic force microscopy (AFM) analysis further confirmed the presence of nanofibers. Furthermore, the fiber shape and dimension analysis by AFM showed flattened and twisted fiber morphology ranging from ~8 nm to ~70 nm. The mechanical properties of the pre-assembled and post assembled solution were investigated by rheometry. The shear-thinning behavior and rapid re-healing properties of the pre-assembled solutions make them a preferable choice for injectable scaffolds. The wide range of stiffnesses (G') -from ~1000 to ~27 000 Pa - exhibited by the post-assembled scaffolds demonstrated their potential for a variety of tissue engineering applications. The extra cellular matrix (ECM) mimicking (physically and chemically) properties of SAP scaffolds enhanced cell adhesion and proliferation. The capability of the scaffold to facilitate murine neural stem cell (mNSC) proliferation was evaluated in vitro: the increased mNSCs adhesion and proliferation demonstrated the potential of newly synthesized SAPs for regenerative medicine approaches. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr32656f

The Indeterminate Case of Classical Static Friction When Coupled with Tension

NASA Astrophysics Data System (ADS)

Hahn, Kenneth D.; Russell, Jacob M.

2018-02-01

It has been noted that the static friction force poses challenges for students and, at times, even their instructors. Unlike the gravitational force, which has a precise and unambiguous magnitude (FG = mg), the magnitude and direction of the static friction force depend on other forces at play. Friction can be understood rather well in terms of complicated atomic-scale interactions between surfaces. Ringlein and Robbins survey aspects of the atomic origins of friction, and Folkerts explores factors that affect the value of static friction. However, what students typically encounter in an introductory course ignores the atomic origins of friction (beyond perhaps a brief overview of the atomic model). The rules of dry friction (i.e., non-lubricated surfaces in contact) taught in introductory physics were originally published in 1699 by Guillaume Amontons. Amontons's first law states that the force of friction is directly proportional to the applied load, i.e., f = μFN, where FN is the normal force and μ is the coefficient of friction. His second law states that the force of friction is independent of the macroscopic area of contact. These laws were verified by Coulomb in 1781.

Is it possible to find presence of lactose in pharmaceuticals? - Preliminary studies by ATR-FTIR spectroscopy and chemometrics

NASA Astrophysics Data System (ADS)

Banas, A.; Banas, K.; Kalaiselvi, S. M. P.; Pawlicki, B.; Kwiatek, W. M.; Breese, M. B. H.

2017-01-01

Lactose and saccharose have the same molecular formula; however, the arrangement of their atoms is different. A major difference between lactose and saccharose with regard to digestion and processing is that it is not uncommon for individuals to be lactose intolerant (around two thirds of the population has a limited ability to digest lactose after infancy), but it is rather unlikely to be saccharose intolerant. The pharmaceutical industry uses lactose and saccharose as inactive ingredients of drugs to help form tablets because of their excellent compressibility properties. Some patients with severe lactose intolerance may experience symptoms of many allergic reactions after taking medicine that contains this substance. People who are specifically "allergic" to lactose (not just lactose intolerant) should not use tablets containing this ingredient. Fourier Transform Infrared (FTIR) spectroscopy has a unique chemical fingerprinting capability and plays a significant important role in the identification and characterization of analyzed samples and hence has been widely used in pharmaceutical science. However, a typical FTIR spectrum collected from tablets contains a myriad of valuable information hidden in a family of tiny peaks. Powerful multivariate spectral data processing can transform FTIR spectroscopy into an ideal tool for high volume, rapid screening and characterization of even minor tablet components. In this paper a method for distinction between FTIR spectra collected for tablets with or without lactose is presented. The results seem to indicate that the success of identifying one component in FTIR spectra collected for pharmaceutical composition (that is tablet) is largely dependent on the choice of the chemometric technique applied.

Probing Long-Range Neutrino-Mediated Forces with Atomic and Nuclear Spectroscopy.

PubMed

Stadnik, Yevgeny V

2018-06-01

The exchange of a pair of low-mass neutrinos between electrons, protons, and neutrons produces a "long-range" 1/r^{5} potential, which can be sought for in phenomena originating on the atomic and subatomic length scales. We calculate the effects of neutrino-pair exchange on transition and binding energies in atoms and nuclei. In the case of atomic s-wave states, there is a large enhancement of the induced energy shifts due to the lack of a centrifugal barrier and the highly singular nature of the neutrino-mediated potential. We derive limits on neutrino-mediated forces from measurements of the deuteron binding energy and transition energies in positronium, muonium, hydrogen, and deuterium, as well as isotope-shift measurements in calcium ions. Our limits improve on existing constraints on neutrino-mediated forces from experiments that search for new macroscopic forces by 18 orders of magnitude. Future spectroscopy experiments have the potential to probe long-range forces mediated by the exchange of pairs of standard-model neutrinos and other weakly charged particles.

Probing Long-Range Neutrino-Mediated Forces with Atomic and Nuclear Spectroscopy

NASA Astrophysics Data System (ADS)

Stadnik, Yevgeny V.

2018-06-01

The exchange of a pair of low-mass neutrinos between electrons, protons, and neutrons produces a "long-range" 1 /r5 potential, which can be sought for in phenomena originating on the atomic and subatomic length scales. We calculate the effects of neutrino-pair exchange on transition and binding energies in atoms and nuclei. In the case of atomic s -wave states, there is a large enhancement of the induced energy shifts due to the lack of a centrifugal barrier and the highly singular nature of the neutrino-mediated potential. We derive limits on neutrino-mediated forces from measurements of the deuteron binding energy and transition energies in positronium, muonium, hydrogen, and deuterium, as well as isotope-shift measurements in calcium ions. Our limits improve on existing constraints on neutrino-mediated forces from experiments that search for new macroscopic forces by 18 orders of magnitude. Future spectroscopy experiments have the potential to probe long-range forces mediated by the exchange of pairs of standard-model neutrinos and other weakly charged particles.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bonthuis, Douwe Jan, E-mail: douwe.bonthuis@physics.ox.ac.uk; Mamatkulov, Shavkat I.; Netz, Roland R.

We optimize force fields for H{sub 3}O{sup +} and OH{sup −} that reproduce the experimental solvation free energies and the activities of H{sub 3}O{sup +} Cl{sup −} and Na{sup +} OH{sup −} solutions up to concentrations of 1.5 mol/l. The force fields are optimized with respect to the partial charge on the hydrogen atoms and the Lennard-Jones parameters of the oxygen atoms. Remarkably, the partial charge on the hydrogen atom of the optimized H{sub 3}O{sup +} force field is 0.8 ± 0.1|e|—significantly higher than the value typically used for nonpolarizable water models and H{sub 3}O{sup +} force fields. In contrast,more » the optimal partial charge on the hydrogen atom of OH{sup −} turns out to be zero. Standard combination rules can be used for H{sub 3}O{sup +} Cl{sup −} solutions, while for Na{sup +} OH{sup −} solutions, we need to significantly increase the effective anion-cation Lennard-Jones radius. While highlighting the importance of intramolecular electrostatics, our results show that it is possible to generate thermodynamically consistent force fields without using atomic polarizability.« less

Manipulating Si(100) at 5 K using qPlus frequency modulated atomic force microscopy: Role of defects and dynamics in the mechanical switching of atoms

NASA Astrophysics Data System (ADS)

Sweetman, A.; Jarvis, S.; Danza, R.; Bamidele, J.; Kantorovich, L.; Moriarty, P.

2011-08-01

We use small-amplitude qPlus frequency modulated atomic force microscopy (FM-AFM), at 5 K, to investigate the atomic-scale mechanical stability of the Si(100) surface. By operating at zero applied bias the effect of tunneling electrons is eliminated, demonstrating that surface manipulation can be performed by solely mechanical means. Striking differences in surface response are observed between different regions of the surface, most likely due to variations in strain associated with the presence of surface defects. We investigate the variation in local energy surface by ab initio simulation, and comment on the dynamics observed during force spectroscopy.

Frequency modulation atomic force microscopy: a dynamic measurement technique for biological systems

NASA Astrophysics Data System (ADS)

Higgins, Michael J.; Riener, Christian K.; Uchihashi, Takayuki; Sader, John E.; McKendry, Rachel; Jarvis, Suzanne P.

2005-03-01

Frequency modulation atomic force microscopy (FM-AFM) has been modified to operate in a liquid environment within an atomic force microscope specifically designed for investigating biological samples. We demonstrate the applicability of FM-AFM to biological samples using the spectroscopy mode to measure the unbinding forces of a single receptor-ligand (biotin-avidin) interaction. We show that quantitative adhesion force measurements can only be obtained provided certain modifications are made to the existing theory, which is used to convert the detected frequency shifts to an interaction force. Quantitative force measurements revealed that the unbinding forces for the biotin-avidin interaction were greater than those reported in previous studies. This finding was due to the use of high average tip velocities, which were calculated to be two orders of magnitude greater than those typically used in unbinding receptor-ligand experiments. This study therefore highlights the potential use of FM-AFM to study a range of biological systems, including living cells and/or single biomolecule interactions.

High-resolution imaging of silicene on an Ag(111) surface by atomic force microscopy

NASA Astrophysics Data System (ADS)

Onoda, Jo; Yabuoshi, Keisuke; Miyazaki, Hiroki; Sugimoto, Yoshiaki

2017-12-01

Silicene, a two-dimensional (2D) honeycomb arrangement of Si atoms, is expected to have better electronic properties than graphene and has been mostly synthesized on Ag surfaces. Although scanning tunneling microscopy (STM) has been used for visualizing its atomic structure in real space, the interpretation of STM contrast is not straightforward and only the topmost Si atoms were observed on the (4 ×4 ) silicene/Ag(111) surface. Here, we demonstrate that high-resolution atomic force microscopy (AFM) can resolve all constituent Si atoms in the buckled honeycomb arrangement of the (4 ×4 ) silicene. Site-specific force spectroscopy attributes the origin of the high-resolution AFM images to chemical bonds between the AFM probe apex and the individual Si atoms on the (4 ×4 ) silicene. A detailed analysis of the geometric parameters suggests that the pulling up of lower-buckled Si atoms by the AFM tip could be a key for high-resolution AFM, implying a weakening of the Si-Ag interactions at the interface. We expect that high-resolution AFM will also unveil atomic structures of edges and defects of silicene, or other emerging 2D materials.

Interplay between Mechanics, Electronics, and Energetics in Atomic-Scale Junctions

NASA Astrophysics Data System (ADS)

Aradhya, Sriharsha V.

The physical properties of materials at the nanoscale are controlled to a large extent by their interfaces. While much knowledge has been acquired about the properties of material in the bulk, there are many new and interesting phenomena at the interfaces that remain to be better understood. This is especially true at the scale of their constituent building blocks - atoms and molecules. Studying materials at this intricate level is a necessity at this point in time because electronic devices are rapidly approaching the limits of what was once thought possible, both in terms of their miniaturization as well as our ability to design their behavior. In this thesis I present our explorations of the interplay between mechanical properties, electronic transport and binding energetics of single atomic contacts and single-molecule junctions. Experimentally, we use a customized conducting atomic force microscope (AFM) that simultaneously measures the current and force across atomic-scale junctions. We use this instrument to study single atomic contacts of gold and silver and single-molecule junctions formed in the gap between two gold metallic point contacts, with molecules with a variety of backbones and chemical linker groups. Combined with density functional theory based simulations and analytical modeling, these experiments provide insight into the correlations between mechanics and electronic structure at the atomic level. In carrying out these experimental studies, we repeatedly form and pull apart nanoscale junctions between a metallized AFM cantilever tip and a metal-coated substrate. The force and conductance of the contact are simultaneously measured as each junction evolves through a series of atomic-scale rearrangements and bond rupture events, frequently resulting in single atomic contacts before rupturing completely. The AFM is particularly optimized to achieve high force resolution with stiff probes that are necessary to create and measure forces across atomic-size junctions that are otherwise difficult to fabricate using conventional lithographic techniques. In addition to the instrumentation, we have developed new algorithmic routines to perform statistical analyses of force data, with varying degrees of reliance on the conductance signatures. The key results presented in this thesis include our measurements with gold metallic contacts, through which we are able to rigorously characterize the stiffness and maximum forces sustained by gold single atomic contacts and many different gold-molecule-gold single-molecule junctions. In our experiments with silver metallic contacts we use statistical correlations in conductance to distinguish between pristine and oxygen-contaminated silver single atomic contacts. This allows us to separately obtain mechanical information for each of these structural motifs. The independently measured force data also provides new insights about atomic-scale junctions that are not possible to obtain through conductance measurements alone. Using a systematically designed set of molecules, we are able to demonstrate that quantum interference is not quenched in single-molecule junctions even at room temperature and ambient conditions. We have also been successful in conducting one of the first quantitative measurements of van der Waals forces at the metal-molecule interface at the single-molecule level. Finally, towards the end of this thesis, we present a general analytical framework to quantitatively reconstruct the binding energy curves of atomic-scale junctions directly from experiments, thereby unifying all of our mechanical measurements. I conclude with a summary of the work presented in this thesis, and an outlook for potential future studies that could be guided by this work.

Midinfrared absorption measured at a lambda/400 resolution with an atomic force microscope.

PubMed

Houel, Julien; Homeyer, Estelle; Sauvage, Sébastien; Boucaud, Philippe; Dazzi, Alexandre; Prazeres, Rui; Ortéga, Jean-Michel

2009-06-22

Midinfrared absorption can be locally measured using a detection combining an atomic force microscope and a pulsed excitation. This is illustrated for the midinfrared bulk GaAs phonon absorption and for the midinfrared absorption of thin SiO(2) microdisks. We show that the signal given by the cantilever oscillation amplitude of the atomic force microscope follows the spectral dependence of the bulk material absorption. The absorption spatial resolution achieved with microdisks is around 50 nanometer for an optical excitation around 22 micrometer wavelength.

Principal Component Analysis of Lipid Molecule Conformational Changes in Molecular Dynamics Simulations.

PubMed

Buslaev, Pavel; Gordeliy, Valentin; Grudinin, Sergei; Gushchin, Ivan

2016-03-08

Molecular dynamics simulations of lipid bilayers are ubiquitous nowadays. Usually, either global properties of the bilayer or some particular characteristics of each lipid molecule are evaluated in such simulations, but the structural properties of the molecules as a whole are rarely studied. Here, we show how a comprehensive quantitative description of conformational space and dynamics of a single lipid molecule can be achieved via the principal component analysis (PCA). We illustrate the approach by analyzing and comparing simulations of DOPC bilayers obtained using eight different force fields: all-atom generalized AMBER, CHARMM27, CHARMM36, Lipid14, and Slipids and united-atom Berger, GROMOS43A1-S3, and GROMOS54A7. Similarly to proteins, most of the structural variance of a lipid molecule can be described by only a few principal components. These major components are similar in different simulations, although there are notable distinctions between the older and newer force fields and between the all-atom and united-atom force fields. The DOPC molecules in the simulations generally equilibrate on the time scales of tens to hundreds of nanoseconds. The equilibration is the slowest in the GAFF simulation and the fastest in the Slipids simulation. Somewhat unexpectedly, the equilibration in the united-atom force fields is generally slower than in the all-atom force fields. Overall, there is a clear separation between the more variable previous generation force fields and significantly more similar new generation force fields (CHARMM36, Lipid14, Slipids). We expect that the presented approaches will be useful for quantitative analysis of conformations and dynamics of individual lipid molecules in other simulations of lipid bilayers.

Mode of bindings of zinc oxide nanoparticles to myoglobin and horseradish peroxidase: A spectroscopic investigations

NASA Astrophysics Data System (ADS)

Mandal, Gopa; Bhattacharya, Sudeshna; Ganguly, Tapan

2011-07-01

The interactions between two heme proteins myoglobin (HMb) and horseradish peroxidase (HRP) with zinc oxide (ZnO) nanoparticles are investigated by using UV-vis absorption, steady state fluorescence, synchronous fluorescence, time-resolved fluorescence, FT-IR, atomic force microscopy (AFM) and circular dichroism (CD) techniques under physiological condition of pH˜7.4. The presence of mainly static mode in fluorescence quenching mechanism of HMb and HRP by ZnO nanoparticle indicates the possibility of formation of ground state complex. The processes of bindings of ZnO nanoparticles with the two proteins are spontaneous molecular interaction procedures. In both cases hydrogen bonding plays a major role. The circular dichroism (CD) spectra reveal that a helicity of the proteins is reduced by increasing ZnO nanoparticle concentration although the α-helical structures of HMb and HRP retain their identity. On binding to the ZnO nanoparticles the secondary structure of HRP molecules (or HMb molecules) remains unchanged while there is a substantial change in the environment of the tyrosin active site in case of HRP molecules and tryptophan active site in case of HMb molecules. Tapping mode atomic force microscopy (AFM) was applied for the investigation the structure of HRP adsorbed in the environment of nanoparticles on the silicon and on the bare silicon. HRP molecules adsorb and aggregate on the mica with ZnO nanoparticle. The aggregation indicates an attractive interaction among the adsorbed molecules. The molecules are randomly distributed on the bare silicon wafer. The adsorption of HRP in the environment of ZnO nanoparticle changes drastically the domains due to a strong interaction between HRP and ZnO nanoparticles. Similar situation is observed in case of HMb molecules. These findings demonstrate the efficacy of biomedical applications of ZnO nanoparticles as well as in elucidating their mechanisms of action as drugs in both human and plant systems.

A complete vibrational study on a potential environmental toxicant agent, the 3,3',4,4'-tetrachloroazobenzene combining the FTIR, FTRaman, UV-Visible and NMR spectroscopies with DFT calculations.

PubMed

Castillo, María V; Pergomet, Jorgelina L; Carnavale, Gustavo A; Davies, Lilian; Zinczuk, Juan; Brandán, Silvia A

2015-01-05

In this study 3,3',4,4'-tetrachloroazobenzene (TCAB) was prepared and then characterized by infrared, Raman, multidimensional nuclear magnetic resonance (NMR) and ultraviolet-visible spectroscopies. The density functional theory (DFT) together with the 6-31G(*) and 6-311++G(**) basis sets were used to study the structures and vibrational properties of the two cis and trans isomers of TCAB. The harmonic vibrational wavenumbers for the optimized geometries were calculated at the same theory levels. A complete assignment of all the observed bands in the vibrational spectra of TCAB was performed combining the DFT calculations with the scaled quantum mechanical force field (SQMFF) methodology. The molecular electrostatic potentials, atomic charges, bond orders and frontier orbitals for the two isomers of TCAB were compared and analyzed. The comparison of the theoretical ultraviolet-visible spectrum with the corresponding experimental demonstrates a good concordance while the calculated (1)H and (13)C chemicals shifts are in good conformity with the corresponding experimental NMR spectra of TCAB in solution. The npp(*) transitions for both forms were studied by natural bond orbital (NBO) while the topological properties were calculated by employing Bader's Atoms in the Molecules (AIM) theory. This study shows that the cis and trans isomers exhibit different structural and vibrational properties and absorption bands. Copyright © 2014. Published by Elsevier B.V.

Study optoelectronic properties for polymer composite thick film

NASA Astrophysics Data System (ADS)

Jobayr, Mahmood Radhi; Al Razak, Ali Hussein Abd; Mahdi, Shatha H.; Fadhil, Rihab Nassr

2018-05-01

Coupling the epoxy with cadmium oxide particles are important for optical properties that may be affected by various mixing proportions. The aim of this experimental study was to evaluate the effect of different mixing proportions on these properties of reinforced epoxy with cadmium oxide particles. The ultrasonic techniques were used to mix and prepared samples of composites. The surfaces topographic of the 50 µm thick reinforced epoxy films were studied using atomic force microscopy (AFM) and microscopy technique (FTIR) Spectroscopy. AFM imaging and quantitative characterization of the films showed that for all samples the root mean square of the surface roughness increases monotonically with increasing the CdO concentrations (from 0% to 15%). The observed effects of CdO concentrations on surface roughness can be explained by two things: the first reason is that the atoms of additives are combined with the original material to form a new compound that is smoother, more homogeneity and smaller in particle size. The second reason is due to high mixing due to ultrasonic mixing. It is clear also, AFM examination of the prepared samples of reinforced epoxy resin shown that topographical contrast and the identification of small structural details critically depend on hardness of epoxy resin, which in turn depended on the ratio of material (CdO) added. We show that the AFM imaging of the films showed that the mean diameter (104.8nm) of films for all of the samples decreased from 135.50 nm to 83.20 nm with the increase of CdO concentrations.

Theoretical Models for Surface Forces and Adhesion and Their Measurement Using Atomic Force Microscopy

PubMed Central

Leite, Fabio L.; Bueno, Carolina C.; Da Róz, Alessandra L.; Ziemath, Ervino C.; Oliveira, Osvaldo N.

2012-01-01

The increasing importance of studies on soft matter and their impact on new technologies, including those associated with nanotechnology, has brought intermolecular and surface forces to the forefront of physics and materials science, for these are the prevailing forces in micro and nanosystems. With experimental methods such as the atomic force spectroscopy (AFS), it is now possible to measure these forces accurately, in addition to providing information on local material properties such as elasticity, hardness and adhesion. This review provides the theoretical and experimental background of AFS, adhesion forces, intermolecular interactions and surface forces in air, vacuum and in solution. PMID:23202925

Performing the Millikan experiment at the molecular scale: Determination of atomic Millikan-Thomson charges by computationally measuring atomic forces.

PubMed

Rogers, T Ryan; Wang, Feng

2017-10-28

An atomic version of the Millikan oil drop experiment is performed computationally. It is shown that for planar molecules, the atomic version of the Millikan experiment can be used to define an atomic partial charge that is free from charge flow contributions. We refer to this charge as the Millikan-Thomson (MT) charge. Since the MT charge is directly proportional to the atomic forces under a uniform electric field, it is the most relevant charge for force field developments. The MT charge shows good stability with respect to different choices of the basis set. In addition, the MT charge can be easily calculated even at post-Hartree-Fock levels of theory. With the MT charge, it is shown that for a planar water dimer, the charge transfer from the proton acceptor to the proton donor is about -0.052 e. While both planar hydrated cations and anions show signs of charge transfer, anions show a much more significant charge transfer to the hydration water than the corresponding cations. It might be important to explicitly model the ion charge transfer to water in a force field at least for the anions.

Energy shift and Casimir-Polder force for an atom out of thermal equilibrium near a dielectric substrate

NASA Astrophysics Data System (ADS)

Zhou, Wenting; Yu, Hongwei

2014-09-01

We study the energy shift and the Casimir-Polder force of an atom out of thermal equilibrium near the surface of a dielectric substrate. We first generalize, adopting the local source hypothesis, the formalism proposed by Dalibard, Dupont-Roc, and Cohen-Tannoudji [J. Phys. (Paris) 43, 1617 (1982), 10.1051/jphys:0198200430110161700; J. Phys. (Paris) 45, 637 (1984), 10.1051/jphys:01984004504063700], which separates the contributions of thermal fluctuations and radiation reaction to the energy shift and allows a distinct treatment of atoms in the ground and excited states, to the case out of thermal equilibrium, and then we use the generalized formalism to calculate the energy shift and the Casimir-Polder force of an isotropically polarizable neutral atom. We identify the effects of the thermal fluctuations that originate from the substrate and the environment and discuss in detail how the Casimir-Polder force out of thermal equilibrium behaves in three different distance regions in both the low-temperature limit and the high-temperature limit for both the ground-state and excited-state atoms, with special attention devoted to the distinctive features as opposed to thermal equilibrium. In particular, we recover the distinctive behavior of the atom-wall force out of thermal equilibrium at large distances in the low-temperature limit recently found in a different theoretical framework, and furthermore we give a concrete region where this behavior holds.

Measuring Roughnesses Of Optical Surfaces

NASA Technical Reports Server (NTRS)

Coulter, Daniel R.; Al-Jumaily, Gahnim A.; Raouf, Nasrat A.; Anderson, Mark S.

1994-01-01

Report discusses use of scanning tunneling microscopy and atomic force microscopy to measure roughnesses of optical surfaces. These techniques offer greater spatial resolution than other techniques. Report notes scanning tunneling microscopes and atomic force microscopes resolve down to 1 nm.

Chemical bond imaging using higher eigenmodes of tuning fork sensors in atomic force microscopy

NASA Astrophysics Data System (ADS)

Ebeling, Daniel; Zhong, Qigang; Ahles, Sebastian; Chi, Lifeng; Wegner, Hermann A.; Schirmeisen, André

2017-05-01

We demonstrate the ability of resolving the chemical structure of single organic molecules using non-contact atomic force microscopy with higher normal eigenmodes of quartz tuning fork sensors. In order to achieve submolecular resolution, CO-functionalized tips at low temperatures are used. The tuning fork sensors are operated in ultrahigh vacuum in the frequency modulation mode by exciting either their first or second eigenmode. Despite the high effective spring constant of the second eigenmode (on the order of several tens of kN/m), the force sensitivity is sufficiently high to achieve atomic resolution above the organic molecules. This is observed for two different tuning fork sensors with different tip geometries (small tip vs. large tip). These results represent an important step towards resolving the chemical structure of single molecules with multifrequency atomic force microscopy techniques where two or more eigenmodes are driven simultaneously.

A review of demodulation techniques for amplitude-modulation atomic force microscopy

PubMed Central

Harcombe, David M; Ragazzon, Michael R P; Moheimani, S O Reza; Fleming, Andrew J

2017-01-01

In this review paper, traditional and novel demodulation methods applicable to amplitude-modulation atomic force microscopy are implemented on a widely used digital processing system. As a crucial bandwidth-limiting component in the z-axis feedback loop of an atomic force microscope, the purpose of the demodulator is to obtain estimates of amplitude and phase of the cantilever deflection signal in the presence of sensor noise or additional distinct frequency components. Specifically for modern multifrequency techniques, where higher harmonic and/or higher eigenmode contributions are present in the oscillation signal, the fidelity of the estimates obtained from some demodulation techniques is not guaranteed. To enable a rigorous comparison, the performance metrics tracking bandwidth, implementation complexity and sensitivity to other frequency components are experimentally evaluated for each method. Finally, the significance of an adequate demodulator bandwidth is highlighted during high-speed tapping-mode atomic force microscopy experiments in constant-height mode. PMID:28900596

The deflection of carbon composite carbon nanotube / graphene using molecular dynamics simulation

NASA Astrophysics Data System (ADS)

Kolesnikova, A. S.; Kirillova, I. V.; Kossovich, L. U.

2018-02-01

For the first time, the dependence of the bending force on the transverse displacement of atoms in the center of the composite material consisting of graphene and parallel oriented zigzag nanotubes was studied. Mathematical modeling of the action of the needle of the atomic force microscope was carried out using the single-layer armchair carbon nanotube. Armchair nanotubes are convenient for using them as a needle of an atomic force microscope, because their edges are not sharpened (unlike zigzag tubes). Consequently, armchair nanotubes will cause minimal damage upon contact with the investigation object. The geometric parameters of the composite was revealed under the action of the bending force of 6μN.

Internal Energy Transfer and Dissociation Model Development using Accelerated First-Principles Simulations of Hypersonic Flow Features

DTIC Science & Technology

2013-07-11

in Fig. 3) is simulated. Each atom interacts with its neighboring atoms through a potential energy surface (PES), such as the simple Lennard - Jones ... Lennard -­‐ Jones  (LJ)   potential  energy  surface  (PES)  dictating  atomic  interaction  forces. The main point of this section is to...the potential energy surface (PES) that governs individual atomic interaction forces. In contrast to existing rotational energy models, we found

Toggling Bistable Atoms via Mechanical Switching of Bond Angle

NASA Astrophysics Data System (ADS)

Sweetman, Adam; Jarvis, Sam; Danza, Rosanna; Bamidele, Joseph; Gangopadhyay, Subhashis; Shaw, Gordon A.; Kantorovich, Lev; Moriarty, Philip

2011-04-01

We reversibly switch the state of a bistable atom by direct mechanical manipulation of bond angle using a dynamic force microscope. Individual buckled dimers at the Si(100) surface are flipped via the formation of a single covalent bond, actuating the smallest conceivable in-plane toggle switch (two atoms) via chemical force alone. The response of a given dimer to a flip event depends critically on both the local and nonlocal environment of the target atom—an important consideration for future atomic scale fabrication strategies.

Will a Decaying Atom Feel a Friction Force?

PubMed

Sonnleitner, Matthias; Trautmann, Nils; Barnett, Stephen M

2017-02-03

We show how a simple calculation leads to the surprising result that an excited two-level atom moving through a vacuum sees a tiny friction force of first order in v/c. At first sight this seems to be in obvious contradiction to other calculations showing that the interaction with the vacuum does not change the velocity of an atom. It is even more surprising that this change in the atom's momentum turns out to be a necessary result of energy and momentum conservation in special relativity.

Noncontact atomic force microscopy in liquid environment with quartz tuning fork and carbon nanotube probe

NASA Astrophysics Data System (ADS)

Kageshima, Masami; Jensenius, Henriette; Dienwiebel, Martin; Nakayama, Yoshikazu; Tokumoto, Hiroshi; Jarvis, Suzanne P.; Oosterkamp, Tjerk H.

2002-03-01

A force sensor for noncontact atomic force microscopy in liquid environment was developed by combining a multiwalled carbon nanotube (MWNT) probe with a quartz tuning fork. Solvation shells of octamethylcyclotetrasiloxane on a graphite surface were detected both in the frequency shift and dissipation. Due to the high aspect ratio of the CNT probe, the long-range background force was barely detectable in the solvation region.

Electronegativity determination of individual surface atoms by atomic force microscopy.

PubMed

Onoda, Jo; Ondráček, Martin; Jelínek, Pavel; Sugimoto, Yoshiaki

2017-04-26

Electronegativity is a fundamental concept in chemistry. Despite its importance, the experimental determination has been limited only to ensemble-averaged techniques. Here, we report a methodology to evaluate the electronegativity of individual surface atoms by atomic force microscopy. By measuring bond energies on the surface atoms using different tips, we find characteristic linear relations between the bond energies of different chemical species. We show that the linear relation can be rationalized by Pauling's equation for polar covalent bonds. This opens the possibility to characterize the electronegativity of individual surface atoms. Moreover, we demonstrate that the method is sensitive to variation of the electronegativity of given atomic species on a surface due to different chemical environments. Our findings open up ways of analysing surface chemical reactivity at the atomic scale.

Electronegativity determination of individual surface atoms by atomic force microscopy

PubMed Central

Onoda, Jo; Ondráček, Martin; Jelínek, Pavel; Sugimoto, Yoshiaki

2017-01-01

Electronegativity is a fundamental concept in chemistry. Despite its importance, the experimental determination has been limited only to ensemble-averaged techniques. Here, we report a methodology to evaluate the electronegativity of individual surface atoms by atomic force microscopy. By measuring bond energies on the surface atoms using different tips, we find characteristic linear relations between the bond energies of different chemical species. We show that the linear relation can be rationalized by Pauling's equation for polar covalent bonds. This opens the possibility to characterize the electronegativity of individual surface atoms. Moreover, we demonstrate that the method is sensitive to variation of the electronegativity of given atomic species on a surface due to different chemical environments. Our findings open up ways of analysing surface chemical reactivity at the atomic scale. PMID:28443645

A Novel Method to Reconstruct the Force Curve by Higher Harmonics of the First Two Flexural Modes in Frequency Modulation Atomic Force Microscope (FM-AFM).

PubMed

Zhang, Suoxin; Qian, Jianqiang; Li, Yingzi; Zhang, Yingxu; Wang, Zhenyu

2018-06-04

Atomic force microscope (AFM) is an idealized tool to measure the physical and chemical properties of the sample surfaces by reconstructing the force curve, which is of great significance to materials science, biology, and medicine science. Frequency modulation atomic force microscope (FM-AFM) collects the frequency shift as feedback thus having high force sensitivity and it accomplishes a true noncontact mode, which means great potential in biological sample detection field. However, it is a challenge to establish the relationship between the cantilever properties observed in practice and the tip-sample interaction theoretically. Moreover, there is no existing method to reconstruct the force curve in FM-AFM combining the higher harmonics and the higher flexural modes. This paper proposes a novel method that a full force curve can be reconstructed by any order higher harmonics of the first two flexural modes under any vibration amplitude in FM-AFM. Moreover, in the small amplitude regime, short range forces are reconstructed more accurately by higher harmonics analysis compared with fundamental harmonics using the Sader-Jarvis formula.

Structural and vibrational spectral investigations of melaminium maleate monohydrate by FTIR, FT-Raman and quantum chemical calculations

NASA Astrophysics Data System (ADS)

Arjunan, V.; Kalaivani, M.; Marchewka, M. K.; Mohan, S.

2013-04-01

The structural investigations of the molecular complex of melamine with maleic acid, namely melaminium maleate monohydrate have been carried out by quantum chemical methods in addition to FTIR, FT-Raman and far-infrared spectral studies. The quantum chemical studies were performed with DFT (B3LYP) method using 6-31G**, cc-pVDZ and 6-311++G** basis sets to determine the energy, structural and thermodynamic parameters of melaminium maleate monohydrate. The hydrogen atom from maleic acid was transferred to the melamine molecule giving the singly protonated melaminium cation. The ability of ions to form spontaneous three-dimensional structure through weak Osbnd H⋯O and Nsbnd H⋯O hydrogen bonds shows notable vibrational effects.

X-ray, spectroscopic and antibacterial activity studies of the 1:1 complex of lasalocid acid with 1,1,3,3-tetramethylguanidine

NASA Astrophysics Data System (ADS)

Huczyński, Adam; Janczak, Jan; Stefańska, Joanna; Rutkowski, Jacek; Brzezinski, Bogumil

2010-08-01

The crystal structure of the 1:1 complex between lasalocid acid (LAS) and 1,1,3,3-tetramethylguanidine (TMG) with one inclusion acetone molecule is studied by X-ray diffraction, FT-IR spectroscopy, 1H and 13C NMR. The complex is stabilized by three intra- and two inter-molecular hydrogen bonds formed between LAS anion and protonated TMG molecule. The NH2+ protons of the protonated TMG molecule are hydrogen bonded with the etheric oxygen atom O(6) and the hydroxyl oxygen atom O(8) of the LAS anion. The intermolecular NH⋯O hydrogen bonds are relatively long (2.933(4) Å and 2.903(4) Å). One oxygen atom of the carboxylate group is involved in a relatively strong intramolecular quasi-aromatic O(1)-H⋯O(3) hydrogen bond of 2.428(4) Å length, and the second oxygen atom in the bifurcated intramolecular relatively weak O(4)-H⋯O(2) of 2.803(4) Å and O(8)-H⋯O(2) of 2.805(4) Å hydrogen bonds. The O(4)-H⋯O(2) and O(8)-H⋯O(2) hydrogen bonds bind the ends of the LAS anion forming a pseudo-cyclic structure. The FT-IR spectra of the complex in the solid state and in the solution are comparable, thus the structures observed in the both states are also comparable. The in vitro biological tests of LAS-TMG show its good activity towards some strains of Gram-positive bacteria but this activity is lower than that of lasalocid acid.

Atomic scale study of nanocontacts

NASA Astrophysics Data System (ADS)

Buldum, A.; Ciraci, S.; Batra, Inder P.; Fong, C. Y.

1998-03-01

Nanocontact and subsequent pulling off a sharp Ni(111) tip on a Cu(110) surface are investigated by using molecular dynamics method with embedded atom model. As the contact is formed, the sharp tip experiences multiple jump to contact in the attractive force range. The contact interface develops discontinuously mainly due to disorder-order transformations which lead to disappearance of a layer and hence abrupt changes in the normal force variation. Atom exchange occurs in the repulsive range. The connective neck is reduced also discontinuously by pulling off the tip. The novel atomic structure of the neck under the tensile force is analyzed. We also presented a comperative study for the contact by a Si(111) tip on Si(111)-(2x1) surface.

Dynamics-Enabled Nanoelectromechanical Systems (NEMS) Oscillators

DTIC Science & Technology

2014-06-01

it becomes strongly nonlinear, and thus constitutes an archetypal candidate for nonlinear engineering • its fundamental resonant frequency...width of spectral peaks of atomic force microscopy (AFM) resonators as they are brought close to a surface. 39 Approved for public release...alternating current AD Allan Deviation AFM atomic force microscopy AFRL Air Force Research Laboratory AlN aluminum nitride APN Anomalous Phase

Fabrication of electron beam deposited tip for atomic-scale atomic force microscopy in liquid.

PubMed

Miyazawa, K; Izumi, H; Watanabe-Nakayama, T; Asakawa, H; Fukuma, T

2015-03-13

Recently, possibilities of improving operation speed and force sensitivity in atomic-scale atomic force microscopy (AFM) in liquid using a small cantilever with an electron beam deposited (EBD) tip have been intensively explored. However, the structure and properties of an EBD tip suitable for such an application have not been well-understood and hence its fabrication process has not been established. In this study, we perform atomic-scale AFM measurements with a small cantilever and clarify two major problems: contaminations from a cantilever and tip surface, and insufficient mechanical strength of an EBD tip having a high aspect ratio. To solve these problems, here we propose a fabrication process of an EBD tip, where we attach a 2 μm silica bead at the cantilever end and fabricate a 500-700 nm EBD tip on the bead. The bead height ensures sufficient cantilever-sample distance and enables to suppress long-range interaction between them even with a short EBD tip having high mechanical strength. After the tip fabrication, we coat the whole cantilever and tip surface with Si (30 nm) to prevent the generation of contamination. We perform atomic-scale AFM imaging and hydration force measurements at a mica-water interface using the fabricated tip and demonstrate its applicability to such an atomic-scale application. With a repeated use of the proposed process, we can reuse a small cantilever for atomic-scale measurements for several times. Therefore, the proposed method solves the two major problems and enables the practical use of a small cantilever in atomic-scale studies on various solid-liquid interfacial phenomena.

Two Long-Wave Infrared Spectral Polarimeters for Use in Understanding Polarization Phenomenology

DTIC Science & Technology

2002-05-01

3550 Aberdeen SE Kirtland Air Force Base, New Mexico 87117 Abstract. Spectrally varying long-wave infrared ( LWIR ) polarization measurements can be used...to identify materials and to discriminate samples from a cluttered background. Two LWIR instruments have been built and fielded by the Air Force...Research Laboratory: a multispectral LWIR imaging polarimeter (LIP) and a full-Stokes Fourier transform in- frared (FTIR) spectral polarimeter (FSP

Experimental (13C NMR, 1H NMR, FT-IR, single-crystal X-ray diffraction) and DFT studies on 3,4-bis(isoproylamino)cyclobut-3-ene-1,2-dione.

PubMed

Süleymanoğlu, Nevin; Ustabaş, Reşat; Alpaslan, Yelda Bingöl; Eyduran, Fatih; Ozyürek, Cengiz; Iskeleli, Nazan Ocak

2011-12-01

In this work, 3,4-bis(isoproylamino)cyclobut-3-ene-1,2-dione C(10)H(16)N(2)O(2) (I), was synthesized and characterized by (13)C NMR, (1)H NMR, FT-IR, UV-vis spectroscopy and single-crystal X-ray diffraction. DFT method with 6-31G(d,p) basis set has been used to calculate the optimized geometrical parameters, atomic charges, vibrational frequencies and chemical shift values. The calculated vibrational frequencies and chemical shift values are compared with experimental FT-IR and NMR spectra. The results of the calculation shows good agreement between experimental and calculated values of the compound I. The existence of N-H⋯O type intermolecular ve C-H⋯O type intramolecular hydrogen bonds can be deduced from differences between experimental and calculated results of FT-IR and NMR. In addition, the molecular electrostatic potential map and frontier molecular orbitals and electronic absorption spectra were performed at B3LYP/6-31G(d,p) level of theory. HOMO-LUMO electronic transition of 4.90 eV are derived from the contribution of the bands π→π* and n→π* The spectral results obtained from FT-IR, NMR and X-ray of I revealed that the compound I is in predominantly enamine tautomeric form, which was supported by DFT calculations. Copyright © 2011 Elsevier B.V. All rights reserved.

FT-IR quantification of the carbonyl functional group in aqueous-phase secondary organic aerosol from phenols

NASA Astrophysics Data System (ADS)

George, Kathryn M.; Ruthenburg, Travis C.; Smith, Jeremy; Yu, Lu; Zhang, Qi; Anastasio, Cort; Dillner, Ann M.

2015-01-01

Recent findings suggest that secondary organic aerosols (SOA) formed from aqueous-phase reactions of some organic species, including phenols, contribute significantly to particulate mass in the atmosphere. In this study, we employ a Fourier transform infrared (FT-IR) spectroscopic technique to identify and quantify the functional group makeup of phenolic SOA. Solutions containing an oxidant (hydroxyl radical or 3,4-dimethoxybenzaldehyde) and either one phenol (phenol, guaiacol, or syringol) or a mixture of phenols mimicking softwood or hardwood emissions were illuminated to make SOA, atomized, and collected on a filter. We produced laboratory standards of relevant organic compounds in order to develop calibrations for four functional groups: carbonyls (Cdbnd O), saturated C-H, unsaturated C-H and O-H. We analyzed the SOA samples with transmission FT-IR to identify and determine the amounts of the four functional groups. The carbonyl functional group accounts for 3-12% of the SOA sample mass in single phenolic SOA samples and 9-14% of the SOA sample mass in mixture samples. No carbonyl functional groups are present in the initial reactants. Varying amounts of each of the other functional groups are observed. Comparing carbonyls measured by FT-IR (which could include aldehydes, ketones, esters, and carboxylic acids) with eight small carboxylic acids measured by ion chromatography indicates that the acids only account for an average of 20% of the total carbonyl reported by FT-IR.

Single ricin detection by atomic force microscopy chemomechanical mapping

NASA Astrophysics Data System (ADS)

Chen, Guojun; Zhou, Jianfeng; Park, Bosoon; Xu, Bingqian

2009-07-01

The authors report on a study of detecting ricin molecules immobilized on chemically modified Au (111) surface by chemomechanically mapping the molecular interactions with a chemically modified atomic force microscopy (AFM) tip. AFM images resolved the different fold-up conformations of single ricin molecule as well as their intramolecule structure of A- and B-chains. AFM force spectroscopy study of the interaction indicates that the unbinding force has a linear relation with the logarithmic force loading rate, which agrees well with calculations using one-barrier bond dissociation model.

A nitrogen-doped carbon nanotube enhanced polyethersulfone membrane system for water treatment

NASA Astrophysics Data System (ADS)

Phao, Neo; Nxumalo, Edward N.; Mamba, Bhekie B.; Mhlanga, Sabelo D.

Water quality in South Africa and around the world continues to deteriorate due to contamination by organic, inorganic and microbial substances. While many efforts have been done to address water quality problems, current drinking water treatment technologies remain costly and do not effectively remove pollutants to acceptable levels. In this work nitrogen doped carbon nanotubes/polyethersulfone (N-CNT/PES) blend membranes were synthesized via a modified phase inversion method and assessed for suitability in drinking water treatment. The N-CNTs with outer diameters of 30-45 nm and 3% N content were prepared using a conventional chemical vapour deposition method and functionalized by refluxing in HNO3. The confirmation and degree of functionalization with -OH and -COOH groups was determined using Fourier-transform infrared (FTIR) spectroscopy and zeta potential analysis. FTIR studies confirmed the successful incorporation of functionalized N-CNTs (N-CNTs) in the membrane matrix. Atomic force microscopy (AFM) analysis revealed that the addition of N-CNTs leads to reduced surface roughness, suggesting a good dispersion of the N-CNTs in the matrix. Permeability studies revealed that the addition of N-CNTs to the polyethersulfone (PES) solution increased the water flux of the blend membrane by up to 70%. N-CNT loadings of 0.04 wt% in the blend membranes gave low surface contact angle of 55° and high fluxes. In addition, inclusion of N-CNTs enhanced the mechanical properties of the N-CNT/PES blend membranes. The use of N-CNTs in mixed matrix PES membranes is reported for the first time here. The result already suggests superior compatibility of the N-CNTs with PES compared to undoped CNTs, due to the high surface reactivity of the N-CNTs.

FT-IR, FT-Raman, NMR studies and ab initio-HF, DFT-B3LYP vibrational analysis of 4-chloro-2-fluoroaniline

NASA Astrophysics Data System (ADS)

Arivazhagan, M.; Anitha Rexalin, D.

2012-10-01

The Fourier transform infrared (FT-IR) and Fourier transform Raman (FT-Raman) spectra of 4-chloro-2-fluoroaniline (CFA) have been recorded and analyzed. The equilibrium geometry, bonding features and harmonic vibrational frequencies have been investigated with the help of ab initio and density functional theory (DFT) methods. The assignments of the vibrational spectra have been carried out with the help of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology. The 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of the molecule are calculated by the Gauge including atomic orbital (GIAO) method. The first order hyperpolarizability (β0) of this novel molecular system and related properties (β, α0 and Δα) of CFA are calculated using B3LYP/6-311++G(d,p) and HF/6-311++G(d,p) methods on the finite-field approach. The calculated results also show that the CFA molecule might have microscopic nonlinear optical (NLO) behavior with non-zero values. Stability of the molecule arising from hyper conjugative interactions, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The result confirms the occurrence of intramolecular charge transfer (ICT) within the molecule. The HOMO-LUMO energies UV-vis spectral analysis and MEP are performed by B3LYP/6-311++G(d,p) approach. A detailed interpretation of the infrared and Raman spectra of CFA is also reported based on total energy distribution (TED). The difference between the observed and scaled wave number values of the most of the fundamentals is very small.

Synthesis and evaluation of PEG-O-chitosan nanoparticles for delivery of poor water soluble drugs: ibuprofen.

PubMed

Hassani Najafabadi, Alireza; Abdouss, Majid; Faghihi, Shahab

2014-08-01

Current methods for preparation of PEGylated chitosan have limitations such as harsh de protecting step and several purification cycles. In the present study, a facile new method for conjugating methoxy polyethylene glycol (mPEG) to chitosan under mild condition is introduced to improve water solubility of chitosan and control the release of poor water soluble drugs. The method consists of chitosan modification by grafting the C6 position of chitosan to mPEG which is confirmed by Fourier transformed-infrared (FT-IR) and proton nuclear magnetic resonance ((1)HNMR) analyses. The amine groups at the C2 position of chitosan are protected using sodium dodecylsulfate (SDS) which is removed by dialyzing the precipitation against Tris solution. The chemical structure of the prepared polymer is characterized by FTIR and (1)HNMR. The synthesized polymer is then employed to prepare nanoparticles which are characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), scanning electron microscopy (SEM), and dynamic light scattering (DLS) for their size and morphology. The nanoparticles are used for encapsulation of ibuprofen followed by in vitro release investigation in gastrointestinal and simulated biological fluids. The chitosan nanoparticles are used as control. The PEGylated nanoparticles show a particle size of 80 nm with spherical morphology. The results clearly show that drug release from PEGylated chitosan nanoparticles is remarkably slower than chitosan. In addition, drug encapsulation and encapsulation efficiency in PEGylated nanoparticles are dependent on the amount of drug added to the formulation being significantly higher than chitosan nanoparticles. This study provides an efficient, novel, and facile method for preparing a nano carrier system for delivery of water insoluble drugs. Copyright © 2014 Elsevier B.V. All rights reserved.

Sugar-based novel niosomal nanocarrier system for enhanced oral bioavailability of levofloxacin.

PubMed

Imran, Muhammad; Shah, Muhammad Raza; Ullah, Farhat; Ullah, Shafi; Elhissi, Abdelbary M A; Nawaz, Waqas; Ahmad, Farid; Sadiq, Abdul; Ali, Imdad

2016-11-01

Vesicular systems have attracted great attention in drug delivery because of their amphiphilicity, biodegradability, non-toxicity and potential for increasing drug bioavailability. A novel sugar-based double-tailed surfactant containing renewable block was synthesized for preparing niosomal vesicles that could be exploited for Levofloxacin encapsulation, aiming to increase its oral bioavailability. The surfactant was characterized by 1 H NMR, mass spectroscopy and Fourier transform infrared spectroscopy (FT-IR). Its biocompatibility was studied against cell cultures and human blood hemolysis. In vivo acute toxicity was evaluated in mice. The vesicle morphology, size, drug-excipients interaction and entrapment efficiency (EE) were examined using atomic force microscope (AFM), dynamic light scattering (DLS), FT-IR and HPLC. Oral bioavailability studies of Levofloxacin in surfactant-based niosomal formulation were carried out using rabbits and plasma samples were analyzed using HPLC. Vesicles were spherical in shape and the size was 190.31 ± 4.51 nm with a polydispersity index (PDI) of 0.29 ± 0.03. The drug EE in niosomes was 68.28 ± 3.45%. When applied on cell lines, high cell viability was observed even after prolonged exposure at high concentrations. It caused 5.77 ± 1.34% hemolysis at 1000 μg/mL and was found to be safe up to 2000 mg/kg. Elevated Levofloxacin plasma concentration was achieved when delivered with novel vesicles. The surfactant was demonstrated to be safe and effective as carrier of Levofloxacin. The study suggests that this sugar-based double-tailed nonionic surfactant could be promising nano-vesicular system for delivery and enhancing oral bioavailability of the hydrophobic Levofloxacin.

Analysis of the structure and the FT-IR and Raman spectra of 2-(4-nitrophenyl)-4H-3,1-benzoxazin-4-one. Comparisons with the chlorinated and methylated derivatives

NASA Astrophysics Data System (ADS)

Castillo, María V.; Rudyk, Roxana A.; Davies, Lilian; Brandán, Silvia Antonia

2017-07-01

In this work, the structural, topological and vibrational properties of the monomer and three dimers of the 2-(4-nitrophenyl)-4H-3,1-benzoxazin-4-one (NPB) derivative were studied combining the experimental FTIR and FT-Raman spectra in the solid phase with DFT calculations. Here, Natural Bond Orbital (NBO), Atoms in Molecules (AIM) and HOMO and LUMO calculations were performed by using the hybrid B3LYP/6-31G*and B3LYP/6-311++G** methods in order to compute those properties and to predict their reactivities. The comparisons with the properties reported for the chlorinated (Cl-PB) and methylated (CH3-PB) derivatives at the same levels of theory can be clearly justified by the activating (CH3) and deactivating (NO2 and Cl) characteristics of the different groups linked to oxaxin rings. The NBO and AIM studies evidence the following stability orders: Cl-PB > NO2-PB > CH3-PB in very good concordance with the f(νC23-X26) force constants values. The frontier orbitals analyses reveal that the Cl-PB and NO2-PB derivatives have good stabilities and high chemical hardness while CH3-PB has a higher chemical reactivity. On the other hand, the complete vibrational assignments for monomer and dimers species of NPB were presented. The presence of the IR bands at 1574 and 1037 cm-1 and, of the Raman bands at 1571 and 1038 cm-1 support clearly the presence of the different dimeric species proposed for NPB.

Removal of industrial dyes and heavy metals by Beauveria bassiana: FTIR, SEM, TEM and AFM investigations with Pb(II).

PubMed

Gola, Deepak; Malik, Anushree; Namburath, Maneesh; Ahammad, Shaikh Ziauddin

2017-10-01

Presence of industrial dyes and heavy metal as a contaminant in environment poses a great risk to human health. In order to develop a potential technology for remediation of dyes (Reactive remazol red, Yellow 3RS, Indanthrene blue and Vat novatic grey) and heavy metal [Cu(II), Ni(II), Cd(II), Zn(II), Cr(VI) and Pb(II)] contamination, present study was performed with entomopathogenic fungi, Beauveria bassiana (MTCC no. 4580). High dye removal (88-97%) was observed during the growth of B. bassiana while removal percentage for heavy metals ranged from 58 to 75%. Further, detailed investigations were performed with Pb(II) in terms of growth kinetics, effect of process parameters and mechanism of removal. Growth rate decreased from 0.118 h -1 (control) to 0.031 h -1 , showing 28% reduction in biomass at 30 mg L -1 Pb(II) with 58.4% metal removal. Maximum Pb(II) removal was observed at 30 °C, neutral pH and 30 mg L -1 initial metal concentration. FTIR analysis indicated the changes induced by Pb(II) in functional groups on biomass surface. Further, microscopic analysis (SEM and atomic force microscopy (AFM)) was performed to understand the changes in cell surface morphology of the fungal cell. SEM micrograph showed a clear deformation of fungal hyphae, whereas AFM studies proved the increase in surface roughness (RSM) in comparison to control cell. Homogenous bioaccumulation of Pb(II) inside the fungal cell was clearly depicted by TEM-high-angle annular dark field coupled with EDX. Present study provides an insight into the mechanism of Pb(II) bioremediation and strengthens the significance of using entomopathogenic fungus such as B. bassiana for metal and dye removal.

Optical Absorption and Visible Photoluminescence from Thin Films of Silicon Phthalocyanine Derivatives

PubMed Central

Rodríguez Gómez, Arturo; Moises Sánchez-Hernández, Carlos; Fleitman-Levin, Ilán; Arenas-Alatorre, Jesús; Carlos Alonso-Huitrón, Juan; Elena Sánchez Vergara, María

2014-01-01

The interest of microelectronics industry in new organic compounds for the manufacture of luminescent devices has increased substantially in the last decade. In this paper, we carried out a study of the usage feasibility of three organic bidentate ligands (2,6-dihydroxyanthraquinone, anthraflavic acid and potassium derivative salt of anthraflavic acid) for the synthesis of an organic semiconductor based in silicon phthalocyanines (SiPcs). We report the visible photoluminescence (PL) at room temperature obtained from thermal-evaporated thin films of these new materials. The surface morphology of these films was analyzed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). AFM indicated that the thermal evaporation technique is an excellent resource in order to obtain low thin film roughness when depositing these kinds of compounds. Fourier transform infrared spectroscopy (FTIR) spectroscopy was employed to investigate possible changes in the intra-molecular bonds and to identify any evidence of crystallinity in the powder compounds and in the thin films after their deposition. FTIR showed that there was not any important change in the samples after the thermal deposition. The absorption coefficient (α) in the absorption region reveals non-direct transitions. Furthermore, the PL of all the investigated samples were observed with the naked eye in a bright background and also measured by a spectrofluorometer. The normalized PL spectra showed a Stokes shift ≈ 0.6 eV in two of our three samples, and no PL emission in the last one. Those results indicate that the Vis PL comes from a recombination of charge carriers between conduction band and valence band preceded by a non-radiative relaxation in the conduction band tails. PMID:28788200

Quantum mechanical study and spectroscopic (FT-IR, FT-Raman, UV-Visible) study, potential energy surface scan, Fukui function analysis and HOMO-LUMO analysis of 3-tert-butyl-4-methoxyphenol by DFT methods.

PubMed

Saravanan, S; Balachandran, V

2014-09-15

This study represents an integral approach towards understanding the electronic and structural aspects of 3-tert-butyl-4-methoxyphenol (TBMP). Fourier-transform Infrared (FT-IR) and Fourier-transform Raman (FT-Raman) spectra of TBMP was recorded in the region 4000-400 cm(-1) and 3500-100 cm(-1), respectively. The molecular structures, vibrational wavenumbers, infrared intensities and Raman activities were calculated using DFT (B3LYP and LSDA) methods using 6-311++G (d,p) basis set. The most stable conformer of TBMP was identified from the computational results. The assignments of vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA) following the scaled quantum mechanical force field (SQMFF) methodology. The first order hyperpolarizability (β0) and related properties (β, α0 and Δα) of TBMP have been discussed. The stability and charge delocalization of the molecule was studied by Natural Bond Orbital (NBO) analysis. UV-Visible spectrum and effects of solvents have been discussed and the electronic properties such as HOMO and LUMO energies were determined by time-dependent TD-DFT approach with B3LYP/6-311++G (d,p) level of theory. The molecule orbital contributions are studied by density of energy states (DOSs). The reactivity sites are identified by mapping the electron density into electrostatic potential surface (MEP). Mulliken analysis of atomic charges is also calculated. The thermodynamic properties at different temperatures were calculated, revealing the correlations between standard heat capacities, standard entropy and standard enthalpy changes with temperatures. Global hardness, global softness, global electrophilicity and ionization potential of the title compound are determined. Copyright © 2014 Elsevier B.V. All rights reserved.

Experimental spectroscopic (FTIR, FT-Raman, FT-NMR, UV-Visible) and DFT studies of 1-ethyl-1,4-dihydro-7-methyl-4oxo-1,8 napthyridine-3-carboxylic acids.

PubMed

Muthu, S; Elamurugu Porchelvi, E

2013-12-01

The solid phase FTIR and FT-Raman spectra of 1-ethyl-1,4-dihydro-7-methyl-4oxo-1,8 napthyridine-3-carboxylic acid (EDMONCA) have been recorded in the regions 4000-500 and 4000-400 cm(-1) respectively. The equilibrium geometry, harmonic vibrational frequencies have been investigated by DFT/B3LYP and B3PW91 methods with 6-311G (d,p) basis set. The different between the observed and scaled wave number values of most of the fundamental is very small. The assignments of the vibrational spectra have been carried out with the aid of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology (SQMFFM). Stability of the molecule arising from hyper conjugative interactions, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. UV-Visible spectrum of the compound was recorded and the electronic properties HOMO and LOMO energies were measured. The electric dipole moment (μD) and first hyperpolarizability (βtot) values of the investigated molecule were computed using ab initio quantum mechanical calculations. The calculated results also show that the EDMONCA molecule may have microscopic nonlinear optics (NLO) behavior with non-zero values. (1)H and (13)C NMR spectra were recorded and (1)H and (13)C nuclear magnetic resonance chemical shift of the molecule were calculated using the gauge independent atomic orbital (GIAO) method. Thermal stability of EDMONCA was studied by thermogravimetric analysis (TGA). Next Fukui function was calculated to explain the chemical selectivity or reactivity site in EDMONCA. Finally molecular electrostatic potential (MEP) and other molecular properties were performed. Copyright © 2013 Elsevier B.V. All rights reserved.

Synthesis, characterization and photovoltaic performance of Mn-doped ZnS quantum dots- P3HT hybrid bulk heterojunction solar cells

NASA Astrophysics Data System (ADS)

Jabeen, Uzma; Adhikari, Tham; Shah, Syed Mujtaba; Pathak, Dinesh; Nunzi, Jean-Michel

2017-11-01

Zinc sulphide (ZnS) and transition metal-doped ZnS nanocrystals were synthesized by co-precipitation method. Further the synthesized nanocrystals were characterized by Field Emission Scanning Electron Microscope (FESEM), High Resolution Transmission Electron Microscope (HRTEM), Fluorescence, UV-Visible, X-ray diffraction (XRD) and Fourier Transformed Infra-red (FTIR) Spectrometer (FTIR). Scanning electron microscope supplemented with EDAX was employed to attain grain size and chemical composition of the nanomaterials. A considerable blue shift of absorption band was noted by the manganese concentration (0.5 M) in the doped sample in comparison with ZnS quantum dots because of the decrease in the size of nanoparticles which may be due to quantum confinement. The photoluminescence emission observed at 596 nm is due to the emission of divalent manganese and can be ascribed to a 4T1→6A1 transition within the 3d shell. Though, the broad blue emission band was observed at 424 nm which may originates from the radiative recombination comprising defect states in the un-doped zinc sulphide quantum dots. XRD analysis exhibited that the synthesized nanomaterial endured in cubic structure. The synthesized nanomaterial combined with organic polymer P3HT, poly (3-hexyl thiophene) and worked in the construction of inverted solar cells. The photovoltaic devices with un-doped zinc sulphide quantum dots showed power conversion efficiency of 0.48% without annealing and 0.52% with annealing. By doping with manganese, the efficiency was enhanced by a factor of 0.52 without annealing and 0.59 with annealing. The morphology and packing behavior of blend of nanocrystals with organic polymer were explored using Atomic Force Microscopy.

Production of polyimide ceria nanocomposites by development of molecular hook technology in nano-sonochemistry.

PubMed

Hatami, Mehdi

2018-06-01

Poly(amic acid), the precursor of polyimide (PI), was used for the preparation of PI/CeO 2 nanocomposites (NC)s by ultrasonic assisted technique via insertion of the surface modified CeO 2 nanoparticles (NP)s into PI matrix. In the preparation stages, in the first, the modifications of CeO 2 NPs by using hexadecyltrimethoxysilane (HDTMS) as a binder were targeted using ultrasonic waves. In the second step, newly designed PI structure was formed from the sonochemical imidization process as a molecular hook. In this step two different reactions were occurred. The acetic acid elimination reaction in the main chain of macromolecule, and the acetylation reaction in the side chains of poly(amic acid) were accomplished. By acetylation process the hook structure was created for trapping of the modified nanoparticles. In the final step the preparation of PI NCs were achieved by sonochemical process. The structural and thermal properties of pure PI and PI/CeO 2 NCs were studied by several techniques such as fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and thermal analyses. FT-IR and 1 H NMR spectra confirmed the success in preparation of PI matrix. The FE-SEM, TEM, and AFM analyses showed the uniform distribution of CeO 2 NPs in PI matrix. The XRD patterns of NCs show the presence of crystalline CeO 2 NPs in amorphous PI matrix. The thermal analysis results reveal that, with increases in the content of CeO 2 NPs in PI matrix, the thermally stability factors of samples were improved. Copyright © 2018 Elsevier B.V. All rights reserved.

Primate cathelicidin orthologues display different structures and membrane interactions.

PubMed

Morgera, Francesca; Vaccari, Lisa; Antcheva, Nikolinka; Scaini, Denis; Pacor, Sabrina; Tossi, Alessandro

2009-02-01

The human cathelicidin LL-37 displays both direct antibacterial activities and the capacity to modulate host-cell activities. These depend on structural characteristics that are subject to positive selection for variation, as observed in a previous analysis of the CAMP gene (encoding LL-37) in primates. The altered balance between cationic and anionic residues in different primate orthologues affects intramolecular salt-bridging and influences the stability of the helical conformation and tendency to aggregate in solution of the peptide. In the present study, we have analysed the effects of these structural variations on membrane interactions for human LL-37, rhesus RL-37 and orang-utan LL-37, using several complementary biophysical and biochemical methods. CD and ATR (attenuated total reflection)-FTIR (Fourier-transform IR) spectroscopy on model membranes indicate that RL-37, which is monomeric and unstructured in bulk solution [F-form (free form)], and human LL-37, which is partly structured and probably aggregated [A-form (aggregated form)], bind biological membranes in different manners. RL-37 may insert more deeply into the lipid bilayer than LL-37, which remains aggregated. AFM (atomic force microscopy) performed on the same supported bilayer as used for ATR-FTIR measurements suggests a carpet-like mode of permeabilization for RL37 and formation of more defined worm-holes for LL-37. Comparison of data from the biological activity on bacterial cells with permeabilization of model membranes indicates that the structure/aggregation state also affects the trajectory of the peptides from bulk solution through the outer cell-wall layers to the membrane. The results of the present study suggest that F-form cathelicidin orthologues may have evolved to have primarily a direct antimicrobial defensive capacity, whereas the A-forms have somewhat sacrificed this to gain host-cell modulating functions.

Swift heavy ion induced modification in morphological and physico-chemical properties of tin oxide nanocomposites

NASA Astrophysics Data System (ADS)

Jaiswal, Manoj Kumar; Kanjilal, D.; Kumar, Rajesh

2013-11-01

Nanocomposite thin films of tin oxide (SnO2)/titanium oxide (TiO2) were grown on silicon (1 0 0) substrates by electron beam evaporation deposition technique using sintered nanocomposite pellet of SnO2/TiO2 in the percentage ratio of 95:5. Sintering of the nanocomposite pellet was done at 1300 °C for 24 h. The thicknesses of these films were measured to be 100 nm during deposition using piezo-sensor attached to the deposition chamber. TiO2 doped SnO2 nanocomposite films were irradiated by 100 MeV Au8+ ion beam at fluence range varying from 1 × 1011 ions/cm2 to 5 × 1013 ions/cm2 at Inter University Accelerator Center (IUAC), New Delhi, India. Chemical properties of pristine and ion irradiation modified thin films were characterized by Fourier Transform Infrared (FTIR) spectroscopy. FTIR peak at 610 cm-1 confirms the presence of O-Sn-O bridge of tin (IV) oxide signifying the composite nature of pristine and irradiated thin films. Atomic Force Microscope (AFM) in tapping mode was used to study the surface morphology and grain growth due to swift heavy ion irradiation at different fluencies. Grain size calculations obtained from sectional analysis of AFM images were compared with results obtained from Glancing Angle X-ray Diffraction (GAXRD) measurements using Scherrer’s formulae. Phase transformation due to irradiation was observed from Glancing Angle X-ray Diffraction (GAXRD) results. The prominent 2θ peaks observed in GAXRD spectrum are at 30.67°, 32.08°, 43.91°, 44.91° and 52.35° in the irradiated films.

FT-IR, FT-Raman, NMR studies and ab initio-HF, DFT-B3LYP vibrational analysis of 4-chloro-2-fluoroaniline.

PubMed

Arivazhagan, M; Anitha Rexalin, D

2012-10-01

The Fourier transform infrared (FT-IR) and Fourier transform Raman (FT-Raman) spectra of 4-chloro-2-fluoroaniline (CFA) have been recorded and analyzed. The equilibrium geometry, bonding features and harmonic vibrational frequencies have been investigated with the help of ab initio and density functional theory (DFT) methods. The assignments of the vibrational spectra have been carried out with the help of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology. The (1)H and (13)C nuclear magnetic resonance (NMR) chemical shifts of the molecule are calculated by the Gauge including atomic orbital (GIAO) method. The first order hyperpolarizability (β(0)) of this novel molecular system and related properties (β, α(0) and Δα) of CFA are calculated using B3LYP/6-311++G(d,p) and HF/6-311++G(d,p) methods on the finite-field approach. The calculated results also show that the CFA molecule might have microscopic nonlinear optical (NLO) behavior with non-zero values. Stability of the molecule arising from hyper conjugative interactions, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The result confirms the occurrence of intramolecular charge transfer (ICT) within the molecule. The HOMO-LUMO energies UV-vis spectral analysis and MEP are performed by B3LYP/6-311++G(d,p) approach. A detailed interpretation of the infrared and Raman spectra of CFA is also reported based on total energy distribution (TED). The difference between the observed and scaled wave number values of the most of the fundamentals is very small. Copyright © 2012 Elsevier B.V. All rights reserved.

Quantum mechanical study of the structure and spectroscopic (FT-IR, FT-Raman, 13C, 1H and UV), first order hyperpolarizabilities, NBO and TD-DFT analysis of the 4-methyl-2-cyanobiphenyl.

PubMed

Sebastian, S; Sundaraganesan, N; Karthikeiyan, B; Srinivasan, V

2011-02-01

The Fourier transform infrared (FT-IR) and FT-Raman of 4-methyl-2-cyanobiphenyl (4M2CBP) have been recorded and analyzed. The equilibrium geometry, bonding features and harmonic vibrational frequencies have been investigated with the help of density functional theory (DFT) method. The assignments of the vibrational spectra have been carried out with the help of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology (SQMFF). The 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by the Gauge including atomic orbital (GIAO) method. The first order hyperpolarizability (β0) of this novel molecular system and related properties (β, α0 and Δα) of 4M2CBP are calculated using HF/6-311G(d,p) method on the finite-field approach. Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital (NBO) analysis. The results show that charge in electron density (ED) in the σ* and π* antibonding orbitals and second order delocalization energies (E2) confirms the occurrence of intramolecular charge transfer (ICT) within the molecule. UV-vis spectrum of the compound was recorded and the electronic properties, such as HOMO and LUMO energies, were performed by time-dependent density functional theory (TD-DFT) approach. Finally the calculations results were applied to simulated infrared and Raman spectra of the title compound which show good agreement with observed spectra. Copyright © 2010 Elsevier B.V. All rights reserved.

Spectroscopic investigations (FT-IR, UV, 1H and 13C NMR) and DFT/TD-DFT calculations of potential analgesic drug 2-[2-(dimethylamino)ethyl]-6-methoxy-4-(pyridin-2-yl)-1(2H)-phthalazinone

NASA Astrophysics Data System (ADS)

Sroczyński, Dariusz; Malinowski, Zbigniew

2017-12-01

The theoretical molecular geometry and the IR, UV, 1H and 13C NMR spectroscopic properties of 2-[2-(dimethylamino)ethyl]-6-methoxy-4-(pyridin-2-yl)-1(2H)-phthalazinone with the previously demonstrated in vivo analgesic activity were characterized. The conformational analysis, performed using the molecular mechanics method with the General AMBER Force Field (GAFF) and the Density Functional Theory (DFT) approach with the B3LYP hybrid functional and the 6-31 + g(d) basis sets, allowed to determine the most stable rotamer. The theoretical molecular geometry of this conformer was then calculated at the B3LYP/6-311++g(d,p) level of theory, and its phthalazinone core was compared with the experimental geometry of 1(2H)-phthalazinone. The calculated vibrational frequencies and the potential energy distribution enabled to assign the theoretical vibrational modes to the experimental FT-IR bands. The UV spectrum calculated with the Time-Dependent Density Functional Theory (TD-DFT) method in methanol identified the main electronic transitions and their character. 1H and 13C NMR chemical shifts simulated by the Gauge-Independent Atomic Orbital (GIAO) method in chloroform confirmed the previous assignment of the experimental resonance signals. The stability of the molecule was considered taking into account the hyperconjugation and electron density delocalization effects evaluated by the Natural Bond Orbital (NBO) method. The calculated spatial distribution of molecular electrostatic potential made possible to estimate the regions with nucleophilic and electrophilic properties. The results of the potentiodynamic polarization measurements were also indicated the corrosion inhibition activity of the title compound on 100Cr6 bearing steel in 1 mol dm-3 HCl solution.

Vibrational properties of TaW alloy using modified embedded atom method potential

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chand, Manesh, E-mail: maneshchand@gmail.com; Uniyal, Shweta; Joshi, Subodh

2016-05-06

Force-constants up to second neighbours of pure transition metal Ta and TaW alloy are determined using the modified embedded atom method (MEAM) potential. The obtained force-constants are used to calculate the phonon dispersion of pure Ta and TaW alloy. As a further application of MEAM potential, the force-constants are used to calculate the local vibrational density of states and mean square thermal displacements of pure Ta and W impurity atoms with Green’s function method. The calculated results are found to be in agreement with the experimental measurements.

Analysis of Complex Carbohydrate Composition in Plant Cell Wall Using Fourier Transformed Mid-Infrared Spectroscopy (FT-IR).

PubMed

Badhan, Ajay; Wang, Yuxi; McAllister, Tim A

2017-01-01

Fourier transformed mid-infrared spectroscopy (FTIR) is a powerful tool for compositional analysis of plant cell walls (Acebes et al., Front Plant Sci 5:303, 2014; Badhan et al., Biotechnol Biofuels 7:1-15, 2014; Badhan et al., BioMed Res Int 2015: 562952, 2015; Roach et al., Plant Physiol 156:1351-1363, 2011). The infrared spectrum generates a fingerprint of a sample with absorption peaks corresponding to the frequency of vibrations between the bonds of the atoms making up the material. Here, we describe a method focused on the use of FTIR in combination with principal component analysis (PCA) to characterize the composition of the plant cell wall. This method has been successfully used to study complex enzyme saccharification processes like rumen digestion to identify recalcitrant moieties in low-quality forage which resist rumen digestion (Badhan et al., BioMed Res Int 2015: 562952, 2015), as well as to characterize cell wall mutant lines or transgenic lines expressing exogenous hydrolases (Badhan et al., Biotechnol Biofuels 7:1-15, 2014; Roach et al., Plant Physiol 156:1351-1363, 2011). The FTIR method described here facilitates high-throughput identification of the major compositional differences across a large set of samples in a low cost and nondestructive manner.

Effect of chain structure on hydrogen bonding in vinyl acetate - vinyl alcohol copolymers

NASA Astrophysics Data System (ADS)

Merekalova, Nadezhda D.; Bondarenko, Galina N.; Denisova, Yuliya I.; Krentsel, Liya B.; Litmanovich, Arkadiy D.; Kudryavtsev, Yaroslav V.

2017-04-01

FTIR spectroscopy and semi-empirical AM1 method are used to study hydrogen bonding in multiblock and random equimolar copolymers of vinyl acetate and vinyl alcohol. An energetically beneficial zip-holder complex, built on multiple inter- and intrachain hydroxyl-hydroxyl bonds and an intrachain hydroxyl-acetyloxy bond, can be formed between two vinyl alcohol sequences. As a result, multiblock copolymers reveal stronger degree of association that affects crystallinity, as well as various rheological and relaxation properties discussed in the literature. Macromolecular complexes in random copolymers are weak and tend to be destroyed in the presence of residual DMF solvent and adsorbed water. Nevertheless, a rather stable interchain quaternary complex can be formed that includes vinyl alcohol and vinyl acetate units and DMF and water molecules. For a single chain it is shown that an H-bond between neighboring vinyl alcohol and vinyl acetate monomer units mostly engages a carbonyl oxygen atom of the vinyl acetate, if the vinyl alcohol belongs to a short (<5 units) sequence, and an ether oxygen atom in the other case. On the whole, the quantum chemistry calculations shed much light on the origin of distinctions in the copolymer FTIR spectra, which may seem subtle when considered standalone.

Effect of the tip state during qPlus noncontact atomic force microscopy of Si(100) at 5 K: Probing the probe

PubMed Central

Jarvis, Sam; Danza, Rosanna; Moriarty, Philip

2012-01-01

Summary Background: Noncontact atomic force microscopy (NC-AFM) now regularly produces atomic-resolution images on a wide range of surfaces, and has demonstrated the capability for atomic manipulation solely using chemical forces. Nonetheless, the role of the tip apex in both imaging and manipulation remains poorly understood and is an active area of research both experimentally and theoretically. Recent work employing specially functionalised tips has provided additional impetus to elucidating the role of the tip apex in the observed contrast. Results: We present an analysis of the influence of the tip apex during imaging of the Si(100) substrate in ultra-high vacuum (UHV) at 5 K using a qPlus sensor for noncontact atomic force microscopy (NC-AFM). Data demonstrating stable imaging with a range of tip apexes, each with a characteristic imaging signature, have been acquired. By imaging at close to zero applied bias we eliminate the influence of tunnel current on the force between tip and surface, and also the tunnel-current-induced excitation of silicon dimers, which is a key issue in scanning probe studies of Si(100). Conclusion: A wide range of novel imaging mechanisms are demonstrated on the Si(100) surface, which can only be explained by variations in the precise structural configuration at the apex of the tip. Such images provide a valuable resource for theoreticians working on the development of realistic tip structures for NC-AFM simulations. Force spectroscopy measurements show that the tip termination critically affects both the short-range force and dissipated energy. PMID:22428093

Optical Interferometric Micrometrology

NASA Technical Reports Server (NTRS)

Abel, Phillip B.; Lauer, James R.

1989-01-01

Resolutions in angstrom and subangstrom range sought for atomic-scale surface probes. Experimental optical micrometrological system built to demonstrate calibration of piezoelectric transducer to displacement sensitivity of few angstroms. Objective to develop relatively simple system producing and measuring translation, across surface of specimen, of stylus in atomic-force or scanning tunneling microscope. Laser interferometer used to calibrate piezoelectric transducer used in atomic-force microscope. Electronic portion of calibration system made of commercially available components.

Effect of dispersion forces on squeezing with Rydberg atoms

NASA Technical Reports Server (NTRS)

Ng, S. K.; Muhamad, M. R.; Wahiddin, M. R. B.

1994-01-01

We report exact results concerning the effect of dipole-dipole interaction (dispersion forces) on dynamic and steady-state characteristics of squeezing in the emitted fluorescent field from two identical coherently driven two-level atoms. The atomic system is subjected to three different damping baths in particular the normal vacuum, a broad band thermal field and a broad band squeezed vacuum. The atomic model is the Dicke model, hence possible experiments are most likely to agree with theory when performed on systems of Rydberg atoms making microwave transitions. The presence of dipole-dipole interaction can enhance squeezing for realizable values of the various parameters involved.

Synthesis and characterization of Ni(II) complex with 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-7,14-dienium bromide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yusoff, Latifah M.; Yusoff, Siti Fairus M.; Ismail, Wafiuddin

Nickel(II) complex have been synthesized by treating a 14-membered ring tetraaza macrocyclic compound, 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-7,14-dienium, bromide (Me{sub 6}N{sub 4}H{sub 4})Br{sub 2} with nickel acetate in metanol. The complex was characterized using elemental analysis, Fourier Transform Infrared (FTIR), Ultraviolet-Visible (UV-Vis), and single crystal diffraction (X-ray). The nickel atom coordinates through four nitrogen atoms in the ligand. Square planar geometry has been proposed for this complex.

FT-IR characterization of the acidic and basic sites on a nanostructured aluminum nitride surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baraton, M.I.; Chen, X.; Gonsalves, K.E.

1997-12-31

A nanostructured aluminum nitride powder prepared by sol-gel type chemical synthesis is analyzed by Fourier transform infrared spectrometry. The surface acidic and basic sites are probed out by adsorption of several organic molecules. Resulting from the unavoidable presence of oxygen, the aluminum nitride surface is an oxinitride layer in fact, and its surface chemistry should present some analogies with alumina. Therefore, a thorough comparison between the acido-basicity of aluminum nitride and aluminum oxide is discussed. The remaining nitrogen atoms in the first atomic layer modify the acidity-basicity relative balance and reveals the specificity of the aluminum nitride surface.

Adhesion Forces between Lewis(X) Determinant Antigens as Measured by Atomic Force Microscopy.

PubMed

Tromas, C; Rojo, J; de la Fuente, J M; Barrientos, A G; García, R; Penadés, S

2001-01-01

The adhesion forces between individual molecules of Lewis(X) trisaccharide antigen (Le(X) ) have been measured in water and in calcium solution by using atomic force microscopy (AFM, see graph). These results demonstrate the self-recognition capability of this antigen, and reinforce the hypothesis that carbohydrate-carbohydrate interaction could be considered as the first step in the cell-adhesion process in nature. Copyright © 2001 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.

Atmospheric reactivity of alcohols, thiols and fluoroalcohols with chlorine atoms

NASA Astrophysics Data System (ADS)

Garzon Ruiz, Andres

Alcohols, thiols and fluoroalcohols are volatile organic compounds (VOCs) which are emitted to the atmosphere from both natural (vegetation, oceans, volcanoes, etc.) and anthropogenic sources (fuels, solvents, wastewater, incinerators, refrigerants, etc.). These pollutants can be eliminated from the troposphere by deposition on the terrestrial surface, direct photolysis or reaction with different tropospheric oxidants. Reactions of VOCs with tropospheric oxidants are involved in the well-known atmospheric phenomenon of photochemical smog or the production of tropospheric ozone. The oxidation of these VOCs in the troposphere is mainly initiated by reaction with OH radicals during the daytime and with NO radicals at night. However, in recent years, the oxidation by chlorine atoms (Cl) has gained great importance in the study of atmospheric reactions because they may exert some influence in the boundary layer, particularly in marine and coastal environments. In general, Cl atoms are much more reactive species than OH and NO; radicals and therefore low concentrations of Cl may compete with OH and NO3 in hydrocarbon oxidation processes. The main source of tropospheric Cl atoms is believed to be the photolysis of chlorine-containing molecules generated by heterogeneous reactions of sea salt aerosols. It has also been proposed that Cl atoms, produced in the photolysis of Cl2 emitted from industrial processes, may enhance hydrocarbon oxidation rates and ozone production in urban environments. In this work, a kinetic, theoretical and mechanistic study of the reaction of several alcohols, thiols, and fluoroalcohols with Cl atoms has been carried out. Pulsed laser photolysis-fluorescence resonance (PLP-RF) technique was used for the kinetic study as a function of temperature and pressure. An environmental chamber-Fourier transform infrared (FTIR) system was also employed in the kinetic studies. Tropospheric lifetimes of these pollutants were estimated using obtained kinetic data. Products of these reactions were determined by FTIR and derivatization with 2,4-dinitrophenylhydrazine and HPLC analysis. Finally, in order to determine the main reaction pathways a theoretical study at QCISD(T)/6-311G**//MP2(Full)(6-311C** level was performed for each reaction.

Topological Structures and Membrane Nanostructures of Erythrocytes after Splenectomy in Hereditary Spherocytosis Patients via Atomic Force Microscopy.

PubMed

Li, Ying; Lu, Liyuan; Li, Juan

2016-09-01

Hereditary spherocytosis is an inherited red blood cell membrane disorder resulting from mutations of genes encoding erythrocyte membrane and cytoskeletal proteins. Few equipments can observe the structural characteristics of hereditary spherocytosis directly expect for atomic force microscopy In our study, we proved atomic force microscopy is a powerful and sensitive instrument to describe the characteristics of hereditary spherocytosis. Erythrocytes from hereditary spherocytosis patients were small spheroidal, lacking a well-organized lattice on the cell membrane, with smaller cell surface particles and had reduced valley to peak distance and average cell membrane roughness vs. those from healthy individuals. These observations indicated defects in the certain cell membrane structural proteins such as α- and β-spectrin, ankyrin, etc. Until now, splenectomy is still the most effective treatment for symptoms relief for hereditary spherocytosis. In this study, we further solved the mysteries of membrane nanostructure changes of erythrocytes before and after splenectomy in hereditary spherocytosis by atomic force microscopy. After splenectomy, the cells were larger, but still spheroidal-shaped. The membrane ultrastructure was disorganized and characterized by a reduced surface particle size and lower than normal Ra values. These observations indicated that although splenectomy can effectively relieve the symptoms of hereditary spherocytosis, it has little effect on correction of cytoskeletal membrane defects of hereditary spherocytosis. We concluded that atomic force microscopy is a powerful tool to investigate the pathophysiological mechanisms of hereditary spherocytosis and to monitor treatment efficacy in clinical practices. To the best of our knowledge, this is the first report to study hereditary spherocytosis with atomic force microscopy and offers important mechanistic insight into the underlying role of splenectomy.

Further along the Road Less Traveled: AMBER ff15ipq, an Original Protein Force Field Built on a Self-Consistent Physical Model

PubMed Central

2016-01-01

We present the AMBER ff15ipq force field for proteins, the second-generation force field developed using the Implicitly Polarized Q (IPolQ) scheme for deriving implicitly polarized atomic charges in the presence of explicit solvent. The ff15ipq force field is a complete rederivation including more than 300 unique atomic charges, 900 unique torsion terms, 60 new angle parameters, and new atomic radii for polar hydrogens. The atomic charges were derived in the context of the SPC/Eb water model, which yields more-accurate rotational diffusion of proteins and enables direct calculation of nuclear magnetic resonance (NMR) relaxation parameters from molecular dynamics simulations. The atomic radii improve the accuracy of modeling salt bridge interactions relative to contemporary fixed-charge force fields, rectifying a limitation of ff14ipq that resulted from its use of pair-specific Lennard-Jones radii. In addition, ff15ipq reproduces penta-alanine J-coupling constants exceptionally well, gives reasonable agreement with NMR relaxation rates, and maintains the expected conformational propensities of structured proteins/peptides, as well as disordered peptides—all on the microsecond (μs) time scale, which is a critical regime for drug design applications. These encouraging results demonstrate the power and robustness of our automated methods for deriving new force fields. All parameters described here and the mdgx program used to fit them are included in the AmberTools16 distribution. PMID:27399642

Evolution of optical force on two-level atom by ultrashort time-domain dark hollow Gaussian pulse

NASA Astrophysics Data System (ADS)

Cao, Xiaochao; Wang, Zhaoying; Lin, Qiang

2017-09-01

Based on the analytical expression of the ultrashort time-domain dark hollow Gaussian (TDHG) pulse, the optical force on two-level atoms induced by a TDHG pulse is calculated in this paper. The phenomena of focusing or defocusing of the light force is numerical analyzed for different detuning, various duration time, and different order of the ultrashort pulse. The transverse optical force can change from a focusing force to a defocusing force depending on the spatial-temporal coupling effect as the TDHG pulses propagating in free space. Our results also show that the initial phase of the TDHG pulse can significantly changes the envelope of the optical force.

Athermalization in atomic force microscope based force spectroscopy using matched microstructure coupling.

PubMed

Torun, H; Finkler, O; Degertekin, F L

2009-07-01

The authors describe a method for athermalization in atomic force microscope (AFM) based force spectroscopy applications using microstructures that thermomechanically match the AFM probes. The method uses a setup where the AFM probe is coupled with the matched structure and the displacements of both structures are read out simultaneously. The matched structure displaces with the AFM probe as temperature changes, thus the force applied to the sample can be kept constant without the need for a separate feedback loop for thermal drift compensation, and the differential signal can be used to cancel the shift in zero-force level of the AFM.

The use of atomic force microscopy to evaluate warm mix asphalt.

DOT National Transportation Integrated Search

2013-01-01

The main objective of this study was to use the Atomic Force Microscopy (AFM) to examine the moisture susceptibility : and healing characteristics of Warm Mix Asphalt (WMA) and compare it with those of conventional Hot Mix Asphalt (HMA). To : this en...

New Angles on Standard Force Fields: Toward a General Approach for Treating Atomic-Level Anisotropy

DOE PAGES

Van Vleet, Mary J.; Misquitta, Alston J.; Schmidt, J. R.

2017-12-21

Nearly all standard force fields employ the “sum-of-spheres” approximation, which models intermolecular interactions purely in terms of interatomic distances. Nonetheless, atoms in molecules can have significantly nonspherical shapes, leading to interatomic interaction energies with strong orientation dependencies. Neglecting this “atomic-level anisotropy” can lead to significant errors in predicting interaction energies. Herein, we propose a simple, transferable, and computationally efficient model (MASTIFF) whereby atomic-level orientation dependence can be incorporated into ab initio intermolecular force fields. MASTIFF includes anisotropic exchange-repulsion, charge penetration, and dispersion effects, in conjunction with a standard treatment of anisotropic long-range (multipolar) electrostatics. To validate our approach, we benchmarkmore » MASTIFF against various sum-of-spheres models over a large library of intermolecular interactions between small organic molecules. MASTIFF achieves quantitative accuracy, with respect to both high-level electronic structure theory and experiment, thus showing promise as a basis for “next-generation” force field development.« less

New Angles on Standard Force Fields: Toward a General Approach for Treating Atomic-Level Anisotropy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Vleet, Mary J.; Misquitta, Alston J.; Schmidt, J. R.

Nearly all standard force fields employ the “sum-of-spheres” approximation, which models intermolecular interactions purely in terms of interatomic distances. Nonetheless, atoms in molecules can have significantly nonspherical shapes, leading to interatomic interaction energies with strong orientation dependencies. Neglecting this “atomic-level anisotropy” can lead to significant errors in predicting interaction energies. Herein, we propose a simple, transferable, and computationally efficient model (MASTIFF) whereby atomic-level orientation dependence can be incorporated into ab initio intermolecular force fields. MASTIFF includes anisotropic exchange-repulsion, charge penetration, and dispersion effects, in conjunction with a standard treatment of anisotropic long-range (multipolar) electrostatics. To validate our approach, we benchmarkmore » MASTIFF against various sum-of-spheres models over a large library of intermolecular interactions between small organic molecules. MASTIFF achieves quantitative accuracy, with respect to both high-level electronic structure theory and experiment, thus showing promise as a basis for “next-generation” force field development.« less

First-principles calculation of the polarization-dependent force driving the Eg mode in bismuth under optical excitation.

NASA Astrophysics Data System (ADS)

Murray, Eamonn; Fahy, Stephen

2014-03-01

Using first principles electronic structure methods, we calculate the induced force on the Eg (zone centre transverse optical) phonon mode in bismuth immediately after absorption of polarized light. When radiation with polarization perpendicular to the c-axis is absorbed in bismuth, the distribution of excited electrons and holes breaks the three-fold rotational symmetry and leads to a net force on the atoms in the direction perpendicular to the axis. We calculate the initial excited electronic distribution as a function of photon energy and polarization and find the resulting transverse and longitudinal forces experienced by the atoms. Using the measured, temperature-dependent rate of decay of the transverse force[2], we predict the approximate amplitude of induced atomic motion in the Eg mode as a function of temperature and optical fluence. This work is supported by Science Foundation Ireland and a Marie Curie International Incoming Fellowship.

Universal aspects of brittle fracture, adhesion, and atomic force microscopy

NASA Technical Reports Server (NTRS)

Banerjea, Amitava; Ferrante, John; Smith, John R.

1989-01-01

This universal relation between binding energy and interatomic separation was originally discovered for adhesion at bimetallic interfaces involving the simple metals Al, Zn, Mg, and Na. It is shown here that the same universal relation extends to adhesion at transition-metal interfaces. Adhesive energies have been computed for the low-index interfaces of Al, Ni, Cu, Ag, Fe, and W, using the equivalent-crystal theory (ECT) and keeping the atoms in each semiinfinite slab fixed rigidly in their equilibrium positions. These adhesive energy curves can be scaled onto each other and onto the universal adhesion curve. The effect of tip shape on the adhesive forces in the atomic-force microscope (AFM) is studied by computing energies and forces using the ECT. While the details of the energy-distance and force-distance curves are sensitive to tip shape, all of these curves can be scaled onto the universal adhesion curve.

Vibrational spectra for uric acid and its D- and 15N-substituted analogues. Assignments for its normal modes from ab initio 3-21G force field.

NASA Astrophysics Data System (ADS)

Majoube, M.; Vergoten, G.

1993-03-01

FTR, Raman, FTIR spectra are obtained for polycrystalline uric acid and seven of its D-and 15N-substituted analogues. Assignments are given from a normal coordinate analysis carried out using a 3-21G ab initio force field. These are discussed by considering observed and calculated frequencies and D- and 15N-isotopic shifts.

Fabrication of anti-adhesion surfaces on aluminium substrates of rubber plastic moulds using electrolysis plasma treatment

NASA Astrophysics Data System (ADS)

Meng, Jianbing; Dong, Xiaojuan; Wei, Xiuting; Yin, Zhanmin

2015-04-01

An anti-adhesion surface with a water contact angle of 167° was fabricated on aluminium samples of rubber plastic moulds by electrolysis plasma treatment using mixed electrolytes of C6H5O7(NH4)3 and Na2SO4, followed by fluorination. To optimise the fabrication conditions, several important processing parameters such as the discharge voltage, discharge time, concentrations of supporting electrolyte and stearic acid ethanol solution were examined systematically. Using scanning electron microscopy (SEM) to analyse surfaces morphology, micrometer scale pits, and protrusions were found on the surface, with numerous nanometer mastoids contained in the protrusions. These binary micro/nano-scale structures, which are similar to the micro-structures of soil-burrowing animals, play a critical role in achieving low adhesion properties. Otherwise, the anti-adhesion behaviours of the resulting samples were analysed by the atomic force microscope (AFM), Fourier-transform infrared spectrophotometer (FTIR), electrons probe micro-analyzer (EPMA), optical contact angle meter, digital Vickers microhardness (Hv) tester, and electronic universal testing. The results show that the electrolysis plasma treatment does not require complex processing parameters, using a simple device, and is an environment-friendly and effective method. Under the optimised conditions, the contact angle (CA) for the modified anti-adhesion surface is up to 167°, the sliding angle (SA) is less than 2°, roughness of the sample surface is only 0.409μm. Moreover, the adhesion force and Hv are 0. 9KN and 385, respectively.

Universal aspects of adhesion and atomic force microscopy

NASA Technical Reports Server (NTRS)

Banerjea, Amitava; Smith, John R.; Ferrante, John

1990-01-01

Adhesive energies are computed for flat and atomically sharp tips as a function of the normal distance to the substrate. The dependence of binding energies on tip shape is investigated. The magnitudes of the binding energies for the atomic force microscope are found to depend sensitively on tip material, tip shape and the sample site being probed. The form of the energy-distance curve, however, is universal and independent of these variables, including tip shape.

Scanning ion-conductance and atomic force microscope with specialized sphere-shaped nanopippettes

NASA Astrophysics Data System (ADS)

Zhukov, M. V.; Sapozhnikov, I. D.; Golubok, A. O.; Chubinskiy-Nadezhdin, V. I.; Komissarenko, F. E.; Lukashenko, S. Y.

2017-11-01

A scanning ion-conductance microscope was designed on the basis of scanning probe microscope NanoTutor. The optimal parameters of nanopipettes fabrication were found according to scanning electron microscopy diagnostics, current-distance I (Z) and current-voltage characteristics. A comparison of images of test objects, including biological samples, was carried out in the modes of optical microscopy, atomic force microscopy and scanning ion-conductance microscopy. Sphere-shaped nanopippettes probes were developed and tested to increase the stability of pipettes, reduce invasiveness and improve image quality of atomic force microscopy in tapping mode. The efficiency of sphere-shaped nanopippettes is shown.

Length-extension resonator as a force sensor for high-resolution frequency-modulation atomic force microscopy in air.

PubMed

Beyer, Hannes; Wagner, Tino; Stemmer, Andreas

2016-01-01

Frequency-modulation atomic force microscopy has turned into a well-established method to obtain atomic resolution on flat surfaces, but is often limited to ultra-high vacuum conditions and cryogenic temperatures. Measurements under ambient conditions are influenced by variations of the dew point and thin water layers present on practically every surface, complicating stable imaging with high resolution. We demonstrate high-resolution imaging in air using a length-extension resonator operating at small amplitudes. An additional slow feedback compensates for changes in the free resonance frequency, allowing stable imaging over a long period of time with changing environmental conditions.

Analysis of the physical atomic forces between noble gas atoms, alkali ions and halogen ions

NASA Technical Reports Server (NTRS)

Wilson, J. W.; Heinbockel, J. H.; Outlaw, R. A.

1986-01-01

The physical forces between atoms and molecules are important in a number of processes of practical importance, including line broadening in radiative processes, gas and crystal properties, adhesion, and thin films. The components of the physical forces between noble gas atoms, alkali ions, and halogen ions are analyzed and a data base for the dispersion forces is developed from the literature based on evaluations with the harmonic oscillator dispersion model for higher order coefficients. The Zener model of the repulsive core is used in the context of the recent asymptotic wave functions of Handler and Smith; and an effective ionization potential within the Handler and Smith wave functions is defined to analyze the two body potential data of Waldman and Gordon, the alkali-halide molecular data, and the noble gas crystal and salt crystal data. A satisfactory global fit to this molecular and crystal data is then reproduced by the model to within several percent. Surface potentials are evaluated for noble gas atoms on noble gas and salt crystal surfaces with surface tension neglected. Within this context, the noble gas surface potentials on noble gas and salt crystals are considered to be accurate to within several percent.

Minimizing pulling geometry errors in atomic force microscope single molecule force spectroscopy.

PubMed

Rivera, Monica; Lee, Whasil; Ke, Changhong; Marszalek, Piotr E; Cole, Daniel G; Clark, Robert L

2008-10-01

In atomic force microscopy-based single molecule force spectroscopy (AFM-SMFS), it is assumed that the pulling angle is negligible and that the force applied to the molecule is equivalent to the force measured by the instrument. Recent studies, however, have indicated that the pulling geometry errors can drastically alter the measured force-extension relationship of molecules. Here we describe a software-based alignment method that repositions the cantilever such that it is located directly above the molecule's substrate attachment site. By aligning the applied force with the measurement axis, the molecule is no longer undergoing combined loading, and the full force can be measured by the cantilever. Simulations and experimental results verify the ability of the alignment program to minimize pulling geometry errors in AFM-SMFS studies.

VEDA: a web-based virtual environment for dynamic atomic force microscopy.

PubMed

Melcher, John; Hu, Shuiqing; Raman, Arvind

2008-06-01

We describe here the theory and applications of virtual environment dynamic atomic force microscopy (VEDA), a suite of state-of-the-art simulation tools deployed on nanoHUB (www.nanohub.org) for the accurate simulation of tip motion in dynamic atomic force microscopy (dAFM) over organic and inorganic samples. VEDA takes advantage of nanoHUB's cyberinfrastructure to run high-fidelity dAFM tip dynamics computations on local clusters and the teragrid. Consequently, these tools are freely accessible and the dAFM simulations are run using standard web-based browsers without requiring additional software. A wide range of issues in dAFM ranging from optimal probe choice, probe stability, and tip-sample interaction forces, power dissipation, to material property extraction and scanning dynamics over hetereogeneous samples can be addressed.

Invited Article: VEDA: A web-based virtual environment for dynamic atomic force microscopy

NASA Astrophysics Data System (ADS)

Melcher, John; Hu, Shuiqing; Raman, Arvind

2008-06-01

We describe here the theory and applications of virtual environment dynamic atomic force microscopy (VEDA), a suite of state-of-the-art simulation tools deployed on nanoHUB (www.nanohub.org) for the accurate simulation of tip motion in dynamic atomic force microscopy (dAFM) over organic and inorganic samples. VEDA takes advantage of nanoHUB's cyberinfrastructure to run high-fidelity dAFM tip dynamics computations on local clusters and the teragrid. Consequently, these tools are freely accessible and the dAFM simulations are run using standard web-based browsers without requiring additional software. A wide range of issues in dAFM ranging from optimal probe choice, probe stability, and tip-sample interaction forces, power dissipation, to material property extraction and scanning dynamics over hetereogeneous samples can be addressed.

Three-dimensional atomic force microscopy mapping at the solid-liquid interface with fast and flexible data acquisition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Söngen, Hagen, E-mail: soengen@uni-mainz.de; Graduate School Materials Science in Mainz, Staudinger Weg 9, 55128 Mainz; Nalbach, Martin

2016-06-15

We present the implementation of a three-dimensional mapping routine for probing solid-liquid interfaces using frequency modulation atomic force microscopy. Our implementation enables fast and flexible data acquisition of up to 20 channels simultaneously. The acquired data can be directly synchronized with commercial atomic force microscope controllers, making our routine easily extendable for related techniques that require additional data channels, e.g., Kelvin probe force microscopy. Moreover, the closest approach of the tip to the sample is limited by a user-defined threshold, providing the possibility to prevent potential damage to the tip. The performance of our setup is demonstrated by visualizing themore » hydration structure above the calcite (10.4) surface in water.« less

Imaging contrast and tip-sample interaction of non-contact amplitude modulation atomic force microscopy with Q-control

NASA Astrophysics Data System (ADS)

Shi, Shuai; Guo, Dan; Luo, Jianbin

2017-10-01

Active quality factor (Q) exhibits many promising properties in dynamic atomic force microscopy. Energy dissipation and image contrasts are investigated in the non-contact amplitude modulation atomic force microscopy (AM-AFM) with an active Q-control circuit in the ambient air environment. Dissipated power and virial were calculated to compare the highly nonlinear interaction of tip-sample and image contrasts with different Q gain values. Greater free amplitudes and lower effective Q values show better contrasts for the same setpoint ratio. Active quality factor also can be employed to change tip-sample interaction force in non-contact regime. It is meaningful that non-destructive and better contrast images can be realized in non-contact AM-AFM by applying an active Q-control to the dynamic system.

Taking nanomedicine teaching into practice with atomic force microscopy and force spectroscopy.

PubMed

Carvalho, Filomena A; Freitas, Teresa; Santos, Nuno C

2015-12-01

Atomic force microscopy (AFM) is a useful and powerful tool to study molecular interactions applied to nanomedicine. The aim of the present study was to implement a hands-on atomic AFM course for graduated biosciences and medical students. The course comprises two distinct practical sessions, where students get in touch with the use of an atomic force microscope by performing AFM scanning images of human blood cells and force spectroscopy measurements of the fibrinogen-platelet interaction. Since the beginning of this course, in 2008, the overall rating by the students was 4.7 (out of 5), meaning a good to excellent evaluation. Students were very enthusiastic and produced high-quality AFM images and force spectroscopy data. The implementation of the hands-on AFM course was a success, giving to the students the opportunity of contact with a technique that has a wide variety of applications on the nanomedicine field. In the near future, nanomedicine will have remarkable implications in medicine regarding the definition, diagnosis, and treatment of different diseases. AFM enables students to observe single molecule interactions, enabling the understanding of molecular mechanisms of different physiological and pathological processes at the nanoscale level. Therefore, the introduction of nanomedicine courses in bioscience and medical school curricula is essential. Copyright © 2015 The American Physiological Society.

Linker Dependent Bond Rupture Force Measurements in Single-Molecule Junctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frei M.; Hybertsen M.; Aradhya S.V.

We use a modified conducting atomic force microscope to simultaneously probe the conductance of a single-molecule junction and the force required to rupture the junction formed by alkanes terminated with four different chemical link groups which vary in binding strength and mechanism to the gold electrodes. Molecular junctions with amine, methylsulfide, and diphenylphosphine terminated molecules show clear conductance signatures and rupture at a force that is significantly smaller than the measured 1.4 nN force required to rupture the single-atomic gold contact. In contrast, measurements with a thiol terminated alkane which can bind covalently to the gold electrode show conductance andmore » force features unlike those of the other molecules studied. Specifically, the strong Au-S bond can cause structural rearrangements in the electrodes, which are accompanied by substantial conductance changes. Despite the strong Au-S bond and the evidence for disruption of the Au structure, the experiments show that on average these junctions also rupture at a smaller force than that measured for pristine single-atom gold contacts.« less

Synthesis, structural, thermal and Hirshfeld surface analysis of novel [1,2,4]triazolo[3,4-b][1,3,4] thiadiazine carrying 1,4-benzothiazine-3-one moiety

NASA Astrophysics Data System (ADS)

Shruthi, C.; Ravindrachary, V.; Guruswamy, B.; Lokanath, N. K.; Kumara, Karthik; Goveas, Janet

2018-05-01

Needle shaped single crystal of the title compound was grown by slow evaporation solution growth technique using ethanol as solvent. The grown single crystal was characterized using FT-IR, Single crystal XRD and Thermal analysis. The FT-IR spectrum confirms the molecular structure and identifies the different functional groups present in the compound. Single crystal XRD study reveals that the crystallized compound belongs to the monoclinic crystal system with P21/c space group and the corresponding cell parameters were identified. The thermal stability of the material was determined using both TGA and DTA analysis. The intermolecular interaction of each individual atom in the crystal lattice was estimated using Hirshfeld surface and finger print analysis.

Structural and vibrational spectral investigations of melaminium maleate monohydrate by FTIR, FT-Raman and quantum chemical calculations.

PubMed

Arjunan, V; Kalaivani, M; Marchewka, M K; Mohan, S

2013-04-15

The structural investigations of the molecular complex of melamine with maleic acid, namely melaminium maleate monohydrate have been carried out by quantum chemical methods in addition to FTIR, FT-Raman and far-infrared spectral studies. The quantum chemical studies were performed with DFT (B3LYP) method using 6-31G(**), cc-pVDZ and 6-311++G(**) basis sets to determine the energy, structural and thermodynamic parameters of melaminium maleate monohydrate. The hydrogen atom from maleic acid was transferred to the melamine molecule giving the singly protonated melaminium cation. The ability of ions to form spontaneous three-dimensional structure through weak OH···O and NH···O hydrogen bonds shows notable vibrational effects. Copyright © 2013 Elsevier B.V. All rights reserved.

Spectroscopic investigation (FT-IR, FT-Raman), HOMO-LUMO, NBO, and molecular docking analysis of N-ethyl-N-nitrosourea, a potential anticancer agent

NASA Astrophysics Data System (ADS)

Singh, Priyanka; Islam, S. S.; Ahmad, Hilal; Prabaharan, A.

2018-02-01

Nitrosourea plays an important role in the treatment of cancer. N-ethyl-N-nitrosourea, also known as ENU, (chemical formula C3H7N3O2), is a highly potent mutagen. The chemical is an alkylating agent and acts by transferring the ethyl group of ENU to nucleobases (usually thymine) in nucleic acids. The molecular structure of N-ethyl-N-nitrosourea has been elucidated using experimental (FT-IR and FT-Raman) and theoretical (DFT) techniques. APT charges, Mulliken atomic charges, Natural bond orbital, Electrostatic potential, HOMO-LUMO and AIM analysis were performed to identify the reactive sites and charge transfer interactions. Furthermore, to evaluate the anticancer activity of ENU molecular docking studies were carried out against 2JIU protein.

FTIR studies of low temperature sulfuric acid aerosols

NASA Technical Reports Server (NTRS)

Anthony, S. E.; Tisdale, R. T.; Disselkamp, R. S.; Tolbert, M. A.; Wilson, J. C.

1995-01-01

Sub-micrometer sized sulfuric acid H2SO4 particles were generated using a constant output atomizer source. The particles were then exposed to water vapor before being injected into a low temperature cell. Multipass transmission Fourier Transformation Infrared (FTIR) spectroscopy was used to determine the phase and composition of the aerosols as a function of time for periods of up to five hours. Binary H2SO4H2O aerosols with compositions from 35 to 95 wt % H2SO4 remained liquid for over 3 hours at room temperatures ranging from 189-240 K. These results suggest that it is very difficut to freeze SSAs via homogeneous nucleation. Attempts to form aerosols more dilute than 35 wt % H2SO4 resulted in ice formation.

The Effects of Orthophosphate in Drinking Water on the Initial Copper Corrosion Using Atomic Force Microscopy

EPA Science Inventory

Corroding of copper piping used in household drinking water plumbing may potentially impacts consumer’s health and economics. Copper corrosion studies conducted on newly corroding material with atomic force microscopy (AFM) may be particularly useful in understanding the impact ...

Development of acceptance criteria for batches of silane primer for external tank thermal protection system bonding applications

NASA Technical Reports Server (NTRS)

Mikes, F.

1985-01-01

Concluding tests for the thermogravimetric and FTIR analyses of DC 1200 silane primers are discussed as well as methods for HPLC and GC analyses and for determining titanium and silicon by atomic absorption spectroscopy. Tables summarizes results obtained for residue, ash, titanium, silicone, Si/Ti ratio, OH-absorption, the lap-shear test, and the GC headspace for alcohols.

Trapped atom number in millimeter-scale magneto-optical traps

NASA Astrophysics Data System (ADS)

Hoth, Gregory W.; Donley, Elizabeth A.; Kitching, John

2012-06-01

For compact cold-atom instruments, it is desirable to trap a large number of atoms in a small volume to maximize the signal-to-noise ratio. In MOTs with beam diameters of a centimeter or larger, the slowing force is roughly constant versus velocity and the trapped atom number scales as d^4. For millimeter-scale MOTs formed from pyramidal reflectors, a d^6 dependence has been observed [Pollack et al., Opt. Express 17, 14109 (2009)]. A d^6 scaling is expected for small MOTs, where the slowing force is proportional to the atom velocity. For a 1 mm diameter MOT, a d^6 scaling results in 10 atoms, and the difference between a d^4 and a d^6 dependence corresponds to a factor of 1000 in atom number and a factor of 30 in the signal-to-noise ratio. We have observed >10^4 atoms in 1 mm diameter MOTs, consistent with a d^4 dependence. We are currently performing measurements for sub-mm MOTs to determine where the d^4 to d^6 crossover occurs in our system. We are also exploring MOTs based on linear polarization, which can potentially produce stronger slowing forces due to stimulated emission [Emile et al., Europhys. Lett. 20, 687 (1992)]. It may be possible to trap more atoms in small volumes with this method, since high intensities can be easily achieved.

How Langmuir-Blodgett trilayers act as templates for directed self-assembly of nanoparticles

NASA Astrophysics Data System (ADS)

Mukherjee, Smita; Datta, Alokmay; Biswas, Nupur; Giglia, Angelo; Nannarone, Stefano

2014-04-01

Atomic force microscopy (AFM) shows that Langmuir-Blodgett (LB) deposition of dissimilar metal stearates (MSt, M = Co, Zn, Cd) on templates of Co-stearate (Co-T) and Cd-stearate (Cd-T) results in self-assembly of MSts into nanocrystalline grains having clear and consistent morphological habits. The grains are better formed and well separated on Cd-T than on Co-T. Fourier transform infrared spectroscopy (FTIR) results show that the headgroup coordination of the overlayer is tuned by the coordination of the Cd-T template and remains unaffected by that of the Co-T template. They also indicate co-existence of a different kind of headgroup structure that is close to the undissociated fatty acid headgroup but differing more in the two types of carbon-oxygen bonds, suggesting an inter-headgroup bonding such as hydrogen bond that may exist on a nanocrystal surface. Results of synchrotron x-ray diffraction at C K-edge, of ZnSt on Cd-T (ZnSt/Cd-T) and Co-T (ZnSt/Co-T), point to a non-closed packed structure for ZnSt/Cd-T and a closed-packed structure for ZnSt/Co-T, with significant superlattice order in the former. The presence of crystalline phases of ZnSt in the nanometer scale, on LB templates, in contrast to the the presence of lamellar phase in bulk ZnSt, is attributed to the the presence of unidentate metal-carboxylate coordination in the former and absence of it in the latter, creating different gradients of dipolar forces at template overlayer interface. Relative strength of this long-range force over short-range intermolecular forces in the templates qualitatively explains better crystallinity and higher ordering in ZnSt/Cd-T compared to ZnSt/Co-T. We propose that the role of dipole moment gradient between template and overlayer in tuning of these metal-organic nanoparticles may be somewhat similar to structural and optical tunability of semiconductor nanocrystals by thermal and self-equilibrium strain.

Direct quantitative measurement of the C═O⋅⋅⋅H–C bond by atomic force microscopy

PubMed Central

Kawai, Shigeki; Nishiuchi, Tomohiko; Kodama, Takuya; Spijker, Peter; Pawlak, Rémy; Meier, Tobias; Tracey, John; Kubo, Takashi; Meyer, Ernst; Foster, Adam S.

2017-01-01

The hydrogen atom—the smallest and most abundant atom—is of utmost importance in physics and chemistry. Although many analysis methods have been applied to its study, direct observation of hydrogen atoms in a single molecule remains largely unexplored. We use atomic force microscopy (AFM) to resolve the outermost hydrogen atoms of propellane molecules via very weak C═O⋅⋅⋅H–C hydrogen bonding just before the onset of Pauli repulsion. The direct measurement of the interaction with a hydrogen atom paves the way for the identification of three-dimensional molecules such as DNAs and polymers, building the capabilities of AFM toward quantitative probing of local chemical reactivity. PMID:28508080

Atom-Pair Kinetics with Strong Electric-Dipole Interactions.

PubMed

Thaicharoen, N; Gonçalves, L F; Raithel, G

2016-05-27

Rydberg-atom ensembles are switched from a weakly to a strongly interacting regime via adiabatic transformation of the atoms from an approximately nonpolar into a highly dipolar quantum state. The resultant electric dipole-dipole forces are probed using a device akin to a field ion microscope. Ion imaging and pair-correlation analysis reveal the kinetics of the interacting atoms. Dumbbell-shaped pair-correlation images demonstrate the anisotropy of the binary dipolar force. The dipolar C_{3} coefficient, derived from the time dependence of the images, agrees with the value calculated from the permanent electric-dipole moment of the atoms. The results indicate many-body dynamics akin to disorder-induced heating in strongly coupled particle systems.

Stretching of short monatomic gold chains-some model calculations

NASA Astrophysics Data System (ADS)

Sumali, Priyanka, Verma, Veena; Dharamvir, Keya

2012-06-01

The Mechanical properties of zig-zag monatomic gold chains containing 5 and 7 atoms were studied using the Siesta Code (SC), which works within the framework of DFT formalism and Gupta Potential (GP), which is an effective atom-atom potential. The zig-zag chains were stretched by keeping the end atoms fixed while rest of the atoms were relaxed till minimum energy is obtained. Energy, Force and Young's Modulus found using GP and SC were plotted as functions of total length. It is found that the breaking force in case of GP is of order of 1.6nN while for SIESTA is of the order of 2.9nN for both the chains.

Imaging powders with the atomic force microscope: from biominerals to commercial materials.

PubMed

Friedbacher, G; Hansma, P K; Ramli, E; Stucky, G D

1991-09-13

Atomically resolved images of pressed powder samples have been obtained with the atomic force microscope (AFM). The technique was successful in resolving the particle, domain, and atomic structure of pismo clam (Tivela stultorum) and sea urchin (Strongylocentrotus purpuratus) shells and of commercially available calcium carbonate (CaCO(3)) and strontium carbonate (SrCO(3)) powders. Grinding and subsequent pressing of the shells did not destroy the microstructure of these materials. The atomic-resolution imaging capabilities of AFM can be applied to polycrystalline samples by means of pressing powders with a grain size as small as 50 micrometers. These results illustrate that the AFM is a promising tool for material science and the study of biomineralization.

Effect of polarization forces on carbon deposition on a non-spherical nanoparticle. Monte Carlo simulations [Effect of polarization forces on atom deposition on a non-spherical nanoparticle. Monte Carlo simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nemchinsky, V.; Khrabry, A.

Trajectories of a polarizable species (atoms or molecules) in the vicinity of a negatively charged nanoparticle (at a floating potential) are considered. The atoms are pulled into regions of strong electric field by polarization forces. The polarization increases the deposition rate of the atoms and molecules at the nanoparticle. The effect of the non-spherical shape of the nanoparticle is investigated by the Monte Carlo method. The shape of the non-spherical nanoparticle is approximated by an ellipsoid. The total deposition rate and its flux density distribution along the nanoparticle surface are calculated. As a result, it is shown that the fluxmore » density is not uniform along the surface. It is maximal at the nanoparticle tips.« less

Effect of polarization forces on carbon deposition on a non-spherical nanoparticle. Monte Carlo simulations [Effect of polarization forces on atom deposition on a non-spherical nanoparticle. Monte Carlo simulations

DOE PAGES

Nemchinsky, V.; Khrabry, A.

2018-02-01

Trajectories of a polarizable species (atoms or molecules) in the vicinity of a negatively charged nanoparticle (at a floating potential) are considered. The atoms are pulled into regions of strong electric field by polarization forces. The polarization increases the deposition rate of the atoms and molecules at the nanoparticle. The effect of the non-spherical shape of the nanoparticle is investigated by the Monte Carlo method. The shape of the non-spherical nanoparticle is approximated by an ellipsoid. The total deposition rate and its flux density distribution along the nanoparticle surface are calculated. As a result, it is shown that the fluxmore » density is not uniform along the surface. It is maximal at the nanoparticle tips.« less

Refined tip preparation by electrochemical etching and ultrahigh vacuum treatment to obtain atomically sharp tips for scanning tunneling microscope and atomic force microscope.

PubMed

Hagedorn, Till; El Ouali, Mehdi; Paul, William; Oliver, David; Miyahara, Yoichi; Grütter, Peter

2011-11-01

A modification of the common electrochemical etching setup is presented. The described method reproducibly yields sharp tungsten tips for usage in the scanning tunneling microscope and tuning fork atomic force microscope. In situ treatment under ultrahigh vacuum (p ≤10(-10) mbar) conditions for cleaning and fine sharpening with minimal blunting is described. The structure of the microscopic apex of these tips is atomically resolved with field ion microscopy and cross checked with field emission. © 2011 American Institute of Physics

Radiation pressure excitation of a low temperature atomic force/magnetic force microscope for imaging in 4-300 K temperature range

NASA Astrophysics Data System (ADS)

Ćelik, Ümit; Karcı, Özgür; Uysallı, Yiǧit; Özer, H. Özgür; Oral, Ahmet

2017-01-01

We describe a novel radiation pressure based cantilever excitation method for imaging in dynamic mode atomic force microscopy (AFM) for the first time. Piezo-excitation is the most common method for cantilever excitation, however it may cause spurious resonance peaks. Therefore, the direct excitation of the cantilever plays a crucial role in AFM imaging. A fiber optic interferometer with a 1310 nm laser was used both for the excitation of the cantilever at the resonance and the deflection measurement of the cantilever in a commercial low temperature atomic force microscope/magnetic force microscope (AFM/MFM) from NanoMagnetics Instruments. The laser power was modulated at the cantilever's resonance frequency by a digital Phase Locked Loop (PLL). The laser beam is typically modulated by ˜500 μW, and ˜141.8 nmpp oscillation amplitude is obtained in moderate vacuum levels between 4 and 300 K. We have demonstrated the performance of the radiation pressure excitation in AFM/MFM by imaging atomic steps in graphite, magnetic domains in CoPt multilayers between 4 and 300 K and Abrikosov vortex lattice in BSCCO(2212) single crystal at 4 K for the first time.

Radiation pressure excitation of a low temperature atomic force/magnetic force microscope for imaging in 4-300 K temperature range.

PubMed

Çelik, Ümit; Karcı, Özgür; Uysallı, Yiğit; Özer, H Özgür; Oral, Ahmet

2017-01-01

We describe a novel radiation pressure based cantilever excitation method for imaging in dynamic mode atomic force microscopy (AFM) for the first time. Piezo-excitation is the most common method for cantilever excitation, however it may cause spurious resonance peaks. Therefore, the direct excitation of the cantilever plays a crucial role in AFM imaging. A fiber optic interferometer with a 1310 nm laser was used both for the excitation of the cantilever at the resonance and the deflection measurement of the cantilever in a commercial low temperature atomic force microscope/magnetic force microscope (AFM/MFM) from NanoMagnetics Instruments. The laser power was modulated at the cantilever's resonance frequency by a digital Phase Locked Loop (PLL). The laser beam is typically modulated by ∼500 μW, and ∼141.8 nm pp oscillation amplitude is obtained in moderate vacuum levels between 4 and 300 K. We have demonstrated the performance of the radiation pressure excitation in AFM/MFM by imaging atomic steps in graphite, magnetic domains in CoPt multilayers between 4 and 300 K and Abrikosov vortex lattice in BSCCO(2212) single crystal at 4 K for the first time.

Thermodynamic forces in coarse-grained simulations

NASA Astrophysics Data System (ADS)

Noid, William

Atomically detailed molecular dynamics simulations have profoundly advanced our understanding of the structure and interactions in soft condensed phases. Nevertheless, despite dramatic advances in the methodology and resources for simulating atomically detailed models, low-resolution coarse-grained (CG) models play a central and rapidly growing role in science. CG models not only empower researchers to investigate phenomena beyond the scope of atomically detailed simulations, but also to precisely tailor models for specific phenomena. However, in contrast to atomically detailed simulations, which evolve on a potential energy surface, CG simulations should evolve on a free energy surface. Therefore, the forces in CG models should reflect the thermodynamic information that has been eliminated from the CG configuration space. As a consequence of these thermodynamic forces, CG models often demonstrate limited transferability and, moreover, rarely provide an accurate description of both structural and thermodynamic properties. In this talk, I will present a framework that clarifies the origin and impact of these thermodynamic forces. Additionally, I will present computational methods for quantifying these forces and incorporating their effects into CG MD simulations. As time allows, I will demonstrate applications of this framework for liquids, polymers, and interfaces. We gratefully acknowledge the support of the National Science Foundation via CHE 1565631.

Hydrogen bond docking preference in furans: Osbnd H ⋯ π vs. Osbnd H ⋯ O

NASA Astrophysics Data System (ADS)

Jiang, Xiaotong; Tsona, Narcisse T.; Tang, Shanshan; Du, Lin

2018-02-01

The docking sites of hydrogen bonds in complexes formed between 2,2,2-trifluoroethanol (TFE), furan (Fu), and 2-methyl furan (MF) have been investigated. Using density functional theory (DFT) calculations, gas phase and matrix isolation FTIR spectroscopies, the strengths of Osbnd H ⋯ O and Osbnd H ⋯ π hydrogen bonds in the complexes were compared to find the docking preference. Calculations suggest that the hydrogen bond donor, TFE, is more likely to dock onto the oxygen atom of the aromatic furans ring, and consequently, the Osbnd H ⋯ O type hydrogen bond is relatively stronger than the Osbnd H ⋯ π type. The FTIR spectrum in the OH-stretching fundamental range obtained at room temperatures has been compared with that obtained at extremely low temperatures in the matrix. The fundamental and the red shifts of OH-stretching vibrations were observed in both FTIR spectra, confirming the formation of hydrogen bonded complexes. By assessing the ability of furan and MF to participate in the formation of Osbnd H ⋯ O hydrogen bond, the effect of ring methylation has been highlighted. From the calculated geometric and thermodynamic parameters as well as the frequency shift of the OH-stretching vibrations in complexes, TFE-MF is found to be more stable than TFE-Fu, which suggests that the strength of the Osbnd H ⋯ O hydrogen bond in TFE-MF originates from the high activity of the furan molecule caused by the methylation of the aromatic ring. The present study furthers the knowledge of docking preference in heteroaromatic molecules and is helpful to understand the nature of intermolecular interactions between hydrogen bond donors and acceptors, including both electron-deficient atoms and π cloud.

Green synthesis of stabilized spherical shaped gold nanoparticles using novel aqueous Elaeis guineensis (oil palm) leaves extract

NASA Astrophysics Data System (ADS)

Ahmad, Tausif; Bustam, Mohamad Azmi; Irfan, Muhammad; Moniruzzaman, Muhammad; Anwaar Asghar, Hafiz Muhammad; Bhattacharjee, Sekhar

2018-05-01

In the last decade, development of bioinspired protocols to synthesize gold nanoparticles (AuNPs) using plants and their extracts have been dealt by researchers due to their low cost, renewability and non-toxic features. A simple, cheap and ecofriendly method is reported to synthesize stabilized AuNPs of size 35-75 nm at room temperature using aqueous Elaeis guineensis (oil palm) leaves extract without addition of any external agent. Oil palm leaves mediated AuNPs were characterized using FTIR, UV-vis spectrophotometer, EDAX, XPS, FESEM, TEM, DLS and TGA. FTIR spectra results revealed contribution of phenolic, carboxylic, amines and amides in reduction of trivalent gold ions and stabilization of formed gold atoms. Reaction solution color change and UV-vis spectra confirmed reduction of gold ions to generate gold atoms. Reaction mechanism explained the role of phenolic compounds in reduction reaction using FTIR and UV-vis spectra results. EDAX and XPS results further validated the formation of metallic gold particles through bioreduction of gold ions. Crystal structure of metallic gold particles was confirmed through XRD peaks indexing to (111), (200), (220) and (311) planes. TEM and FESEM particles size measurements exhibited the formation of nanostructured AuNPs. Synthesis of well scattered and spherical shaped AuNPs was revealed through FESEM and TEM images. The excellent stability of AuNPs was shown through high negative zeta potential value (-14.7 ± 4.68 mV) and uniform dispersion in aqueous media. Our results disclosed the excellent potential of Elaeis guineensis (oil palm) leaves as reducing and stabilizing agents in green synthesis of well scattered spherical shaped AuNPs, which can be employed as strong candidates in medical drug delivery and industrial applications.

Spectroscopic (FT-IR, FT-Raman, UV and NMR) investigation and NLO, HOMO-LUMO, NBO analysis of organic 2,4,5-trichloroaniline.

PubMed

Govindarajan, M; Karabacak, M; Periandy, S; Tanuja, D

2012-11-01

In this work, the experimental and theoretical study on the molecular structure and vibrational spectra of 2,4,5-trichloroaniline (C(6)H(4)NCl(3), abbreviated as 2,4,5-TClA) were studied. The FT-IR and FT-Raman spectra were recorded. The molecular geometry and vibrational frequencies in the ground state were calculated by using the Hartree-Fock (HF) and density functional theory (DFT) methods (B3LYP) with 6-311++G(d,p) basis set. Comparison of the observed fundamental vibrational frequencies of 2,4,5-TClA with calculated results by HF and DFT indicates that B3LYP is superior to HF method for molecular vibrational problems. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. The theoretically predicted FT-IR and FT-Raman spectra of the title molecule have been constructed. A study on the electronic properties, such as HOMO and LUMO energies, were performed by time-dependent DFT (TD-DFT) approach. Besides, molecular electrostatic potential (MEP) and thermodynamic properties were performed. The electric dipole moment (μ) and the first hyperpolarizability (β) values of the investigated molecule were computed using ab initio quantum mechanical calculations. The calculated results also show that the 2,4,5-TClA molecule may have microscopic nonlinear optical (NLO) behavior with non-zero values. Mulliken atomic charges of 2,4,5-TClA was calculated and compared with aniline and chlorobenzene molecules. The (13)C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by the gauge independent atomic orbital (GIAO) method and compared with experimental results. Copyright © 2012 Elsevier B.V. All rights reserved.

Observation of DNA Molecules Using Fluorescence Microscopy and Atomic Force Microscopy

ERIC Educational Resources Information Center

Ito, Takashi

2008-01-01

This article describes experiments for an undergraduate instrumental analysis laboratory that aim to observe individual double-stranded DNA (dsDNA) molecules using fluorescence microscopy and atomic force microscopy (AFM). dsDNA molecules are observed under several different conditions to discuss their chemical and physical properties. In…

Conductive Atomic Force Microscopy | Materials Science | NREL

Science.gov Websites

electrical measurement techniques is the high spatial resolution. For example, C-AFM measurements on : High-resolution image of a sample semiconductor device; the image shows white puff-like clusters on a dark background and was obtained using atomic force microscopy. Bottom: High-resolution image of the

Uncertainty quantification in nanomechanical measurements using the atomic force microscope

Treesearch

Ryan Wagner; Robert Moon; Jon Pratt; Gordon Shaw; Arvind Raman

2011-01-01

Quantifying uncertainty in measured properties of nanomaterials is a prerequisite for the manufacture of reliable nanoengineered materials and products. Yet, rigorous uncertainty quantification (UQ) is rarely applied for material property measurements with the atomic force microscope (AFM), a widely used instrument that can measure properties at nanometer scale...

Note: Thermal analog to atomic force microscopy force-displacement measurements for nanoscale interfacial contact resistance.

PubMed

Iverson, Brian D; Blendell, John E; Garimella, Suresh V

2010-03-01

Thermal diffusion measurements on polymethylmethacrylate-coated Si substrates using heated atomic force microscopy tips were performed to determine the contact resistance between an organic thin film and Si. The measurement methodology presented demonstrates how the thermal contrast signal obtained during a force-displacement ramp is used to quantify the resistance to heat transfer through an internal interface. The results also delineate the interrogation thickness beyond which thermal diffusion in the organic thin film is not affected appreciably by the underlying substrate.

77 FR 42483 - Application(s) for Duty-Free Entry of Scientific Instruments

Federal Register 2010, 2011, 2012, 2013, 2014

2012-07-19

... creating artificial nanoscale structures on an atom-by- atom basis using nascent atom manipulation techniques. The instrument will be used to investigate the amount of force required to move one atom on a materials surface while simultaneously measuring local electronic structural changes during atom movement...

DelPhiForce web server: electrostatic forces and energy calculations and visualization.

PubMed

Li, Lin; Jia, Zhe; Peng, Yunhui; Chakravorty, Arghya; Sun, Lexuan; Alexov, Emil

2017-11-15

Electrostatic force is an essential component of the total force acting between atoms and macromolecules. Therefore, accurate calculations of electrostatic forces are crucial for revealing the mechanisms of many biological processes. We developed a DelPhiForce web server to calculate and visualize the electrostatic forces at molecular level. DelPhiForce web server enables modeling of electrostatic forces on individual atoms, residues, domains and molecules, and generates an output that can be visualized by VMD software. Here we demonstrate the usage of the server for various biological problems including protein-cofactor, domain-domain, protein-protein, protein-DNA and protein-RNA interactions. The DelPhiForce web server is available at: http://compbio.clemson.edu/delphi-force. delphi@clemson.edu. Supplementary data are available at Bioinformatics online. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com

Resonance oscillations of nonreciprocal long-range van der Waals forces between atoms in electromagnetic fields

NASA Astrophysics Data System (ADS)

Sherkunov, Yury

2018-03-01

We study theoretically the van der Waals interaction between two atoms out of equilibrium with an isotropic electromagnetic field. We demonstrate that at large interatomic separations, the van der Waals forces are resonant, spatially oscillating, and nonreciprocal due to resonance absorption and emission of virtual photons. We suggest that the van der Waals forces can be controlled and manipulated by tuning the spectrum of artificially created random light.

Effects of atomic oxygen on polymeric materials flown on EOIM-3

NASA Technical Reports Server (NTRS)

Kamenetzky, Rachel R.; Linton, Roger C.; Finckenor, Miria M.; Vaughn, Jason A.

1995-01-01

Diverse polymeric materials, including several variations of Kapton, were flown on STS-46 as part of the Evaluation of Oxygen Interaction with Materials Experiment (EOIM-3). These materials were flown in the cargo bay and exposed to the space environment July 31 - August 8, 1992, including 40 hours of direct atomic oxygen impingement. The atomic oxygen exposure was approximately 2.2 x 10(exp 20) atoms/sq cm. Polymeric materials flown on EOIM-3 include coated and uncoated Kapton, Tefzel ETFE, Lexan, FEP and TFE Teflon, bulk Halar and PEEK, S383 silicone and Viton elastomeric seal material. Analyses performed included thickness measurements using Dektak and eddy current methods, mass loss, resistance, permeability, hardness, and FTIR. The effects of stress and the space environment on Kapton were also evaluated. Previous EOIM missions on STS-5 and STS-8 and the Long Duration Exposure Facility also contained polymeric material samples. Data from these previous flights are shown for comparison, as well as ground simulation of space environment effects using both thermal energy flow tubes and 5 eV neutral atomic oxygen beam facilities. Reaction efficiencies for the various atomic oxygen exposure conditions are discussed.

Characterization and intramolecular bonding patterns of busulfan: Experimental and quantum chemical approach

NASA Astrophysics Data System (ADS)

Karthick, T.; Tandon, Poonam; Singh, Swapnil; Agarwal, Parag; Srivastava, Anubha

2017-02-01

The investigations of structural conformers, molecular interactions and vibrational characterization of pharmaceutical drug are helpful to understand their behaviour. In the present work, the 2D potential energy surface (PES) scan has been performed on the dihedral angles C6sbnd O4sbnd S1sbnd C5 and C25sbnd S22sbnd O19sbnd C16 to find the stable conformers of busulfan. In order to show the effects of long range interactions, the structures on the global minima of PES scan have been further optimized by B3LYP/6-311 ++G(d,p) method with and without empirical dispersion functional in Gaussian 09W package. The presence of n → σ* and σ → σ* interactions which lead to stability of the molecule have been predicted by natural bond orbital analysis. The strong and weak hydrogen bonds between the functional groups of busulfan were analyzed using quantum topological atoms in molecules analysis. In order to study the long-range forces, such as van der Waals interactions, steric effect in busulfan, the reduced density gradient as well as isosurface defining these interactions has been plotted using Multiwfn software. The spectroscopic characterization on the solid phase of busulfan has been studied by experimental FT-IR and FT-Raman spectra. From the 13C and 1H NMR spectra, the chemical shifts of individual C and H atoms of busulfan have been predicted. The maximum absorption wavelengths corresponding to the electronic transitions between the highest occupied molecular orbital and the lowest unoccupied molecular orbital of busulfan have been found by UV-vis spectrum.

Enhancement of nonlinear optical and temperature dependent dielectric properties of Ce:BaTiO3 nano and submicron particles

NASA Astrophysics Data System (ADS)

Senthilkumar, P.; Dhanuskodi, S.; Thomas, Anitta Rose; Philip, Reji

2017-08-01

The solgel synthesized Ce: BaTiO3 (BT) particles are crystallized in tetragonal structure and the expansion of lattice along a-axis is ensured from the Rietveld refined XRD spectra. FTIR shows that the increase of force constant from 199.97 to 213.13 N m-1 is owing to an effective incorporation of heavier atomic mass of Ce in BT lattice. HRTEM reflects the discontinuous atomic planes in the form of Ti vacancies which is supported by EDS measurement. The modification of optical band structure of BT with Ce ions is validated through several absorption and defect emission bands. Energy dependent second harmonic generation is carried out to confirm the non saturated signal, thermal stability and maximum intensity 2483 counts attained for 2 mol% Ce at 200 mJ. Optical limiting characteristics of the samples is analysed at 532 nm using 5 ns laser pulses of energy 50, 100 and 150 µJ. The nonlinear absorption coefficient (β) is found to be enhanced upon Ce doping. Lower optical limiting thresholds of 2.8 and 3.3 J cm-2 are obtained in the case of 1 and 4 mol% Ce samples respectively. Dielectric properties in a broad temperature range (40-500 °C) and frequency (100 Hz-5 MHz) have been investigated in detail. The dielectric constant is increased from 1926 to 3750 on Ce doping and there are two semicircles in the Cole-Cole plot at 500 °C due to grain and grain boundaries and corresponding equivalent circuit model is proposed.

Study on effect of plasma surface treatments for diamond deposition by DC arc plasmatron.

PubMed

Kang, In-Je; Joa, Sang-Beom; Lee, Heon-Ju

2013-11-01

To improve the thermal conductivity and wear resistance of ceramic materials in the field of renewable energy technologies, diamond coating by plasma processing has been carried out in recent years. This study's goal is to improve diamond deposition on Al2O3 ceramic substrates by plasma surface treatments. Before diamond deposition was carried out in a vacuum, plasma surface treatments using Ar gas were conducted to improve conditions for deposition. We also conducted plasma processing for diamond deposition on Al2O3 ceramic substrates using a DC arc Plasmatron. The Al2O3 ceramic substrates with diamond film (5 x 15 mm2), were investigated by SEM (Scanning Electron Microscopy), AFM (Atomic Force Microscopy) and XRD (X-ray Diffractometer). Then, the C-H stretching of synthetic diamond films by FTIR (Fourier Transform Infrared Spectroscopy) was studied. We identified nanocrystalline diamond films on the Al2O3 ceramic substrates. The results showed us that the deposition rate of diamond films was 2.3 microm/h after plasma surface treatments. Comparing the above result with untreated ceramic substrates, the deposition rate improved with the surface roughness of the deposited diamond films.

Silk fibroin/gold nanocrystals: a new example of biopolymer-based nanocomposites

NASA Astrophysics Data System (ADS)

Noinville, S.; Garnier, A.; Courty, A.

2017-05-01

The dispersion of nanoparticles in ordered polymer nanostructures can provide control over particle location and orientation, and pave the way for tailored nanomaterials that have enhanced mechanical, electrical, or optical properties. Here we used silk fibroin, a natural biopolymer, to embed gold nanocrystals (NCs), so as to obtain well-ordered structures such as nanowires and self-assembled triangular nanocomposites. Monodisperse gold NCs synthesized in organic media are mixed to silk fibroin and the obtained nanocomposites are characterized by UV-visible spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and Infrared spectroscopy. The optical properties study of gold NCs and silk-gold nanocomposites shows that the Surface Plasmon band is blue shifted compared to gold NCs. The size and shape of NCs gold superlattices can be well controlled by the presence of silk fibroin giving nanowires and also self-assembled triangular nanocomposites as characterized by TEM, FE-SEM and AFM. The strong interaction between gold NCs and silk fibroin is also revealed by the conformation change of silk protein in presence of gold NCs, as shown by FTIR analysis. The formation of such ordered nanocomposites (gold NCs/silk fibroin) will provide new nanoplasmonic devices.

Hygroscopic properties of internally mixed particles composed of NaCl and water-soluble organic acids.

PubMed

Ghorai, Suman; Wang, Bingbing; Tivanski, Alexei; Laskin, Alexander

2014-02-18

Atmospheric aging of naturally emitted marine aerosol often leads to formation of internally mixed particles composed of sea salts and water-soluble organic compounds of anthropogenic origin. Mixing of sea salt and organic components has profound effects on the evolving chemical composition and hygroscopic properties of the resulted particles, which are poorly understood. Here, we have studied chemical composition and hygroscopic properties of laboratory generated NaCl particles mixed with malonic acid (MA) and glutaric acid (GA) at different molar ratios using micro-FTIR spectroscopy, atomic force microscopy, and X-ray elemental microanalysis. Hygroscopic properties of internally mixed NaCl and organic acid particles were distinctly different from pure components and varied significantly with the type and amount of organic compound present. Experimental results were in a good agreement with the AIM modeling calculations of gas/liquid/solid partitioning in studied systems. X-ray elemental microanalysis of particles showed that Cl/Na ratio decreased with increasing organic acid component in the particles with MA yielding lower ratios relative to GA. We attribute the depletion of chloride to the formation of sodium malonate and sodium glutarate salts resulted by HCl evaporation from dehydrating particles.

Characterization of 10,12-pentacosadiynoic acid Langmuir–Blodgett monolayers and their use in metal–insulator–metal tunnel devices

PubMed Central

Sharma, Saumya; Khawaja, Mohamad; Ram, Manoj K; Goswami, D Yogi

2014-01-01

Summary The characterization of Langmuir–Blodgett thin films of 10,12-pentacosadiynoic acid (PDA) and their use in metal–insulator–metal (MIM) devices were studied. The Langmuir monolayer behavior of the PDA film was studied at the air/water interface using surface tension–area isotherms of polymeric and monomeric PDA. Langmuir–Blodgett (LB, vertical deposition) and Langmuir–Schaefer (LS, horizontal deposition) techniques were used to deposit the PDA film on various substrates (glass, quartz, silicon, and nickel-coated film on glass). The electrochemical, electrical and optical properties of the LB and LS PDA films were studied using cyclic voltammetry, current–voltage characteristics (I–V), and UV–vis and FTIR spectroscopies. Atomic force microscopy measurements were performed in order to analyze the surface morphology and roughness of the films. A MIM tunnel diode was fabricated using a PDA monolayer assembly as the insulating barrier, which was sandwiched between two nickel layers. The precise control of the thickness of the insulating monolayers proved critical for electron tunneling to take place in the MIM structure. The current–voltage characteristics of the MIM diode revealed tunneling behavior in the fabricated Ni–PDA LB film–Ni structures. PMID:25551052

Effect of TiO, nanoparticles on the interface in the PET-rubber composites.

PubMed

Vladuta, Cristina; Andronic, Luminita; Duta, Anca

2010-04-01

Usually, ceramic powders (SiO2, ZnO) are used as fillers for enhancing rubber mechanical strength. Poly-ethylene terephthalate (PET)-rubber nanocomposites were prepared by compression molding using titanium oxide (TiO2) nanoparticles as low content fillers (<2% wt). The interface properties of PET-rubber nanocomposites were studied before and after keeping the samples under UV-radiation for a week. UV-radiation has interesting potential for the photochemical modification of polymers and TiO2. The influence of UV radiation on the properties of the interface polymer-TiO2 nanoparticles was evaluated. The impact of nanoparticle aggregates on the nanometer to micrometer organization of PET-rubber composites was studied with Atomic Force Microscopy (AFM). The interface properties were explained by measuring the contact angles and surface tensions. The interactions between components of nanocomposites were investigated with Fourier Transform-Infrared (FTIR) and the effects of TiO2 nanoparticle on the interfaces and composites crystalline structure were evaluated by X-ray diffraction (XRD). The results proved that the TiO2 nanoparticles, in different weight percentages, did not alter the nanocomposites crystallinity or the average crystallites size, but improve the interface properties.

Characterization of ZrO2 and (ZrO2)x(Al2O3)1-X thin films on Si substrates: effect of the Al2O3 component

NASA Astrophysics Data System (ADS)

Vitanov, P.; Harizanova, A.; Ivanova, T.

2014-05-01

ZrO2 and (ZrO2)x(Al2O3)1-x films were deposited by the sol-gel technique on Si substrates. The effect of the Al2O3 additive on the film surface morphology was studied by atomic force microscopy (AFM). The mixed oxide films showed a smoother morphology and lower values of the root-mean-square (RMS) roughness compared to ZrO2. Further, FTIR spectra indicated that ZrO2 underwent crystallization. The electrical measurements of the MIS structure revealed that the presence of Al2O3 and the amorphization affects its dielectric properties. The MIS structure with (ZrO2)x(Al2O3)1-x showed a lower fixed charge (~ 6×1010 cm-2) and an interface state density in the middle of the band gap of 6×1011 eV-1 cm-2). The dielectric constant measured was 22, with the leakage current density decreasing to 2×10-8 A cm-2 at 1×106 V cm-1.

Physicochemical properties of liposomes as potential anticancer drugs carriers. Interaction of etoposide and cytarabine with the membrane: Spectroscopic studies

NASA Astrophysics Data System (ADS)

Pentak, Danuta

2014-03-01

The interactions between etoposide, cytarabine and 1,2-dihexadecanoyl-sn-glycerol-3-phosphocholine bilayers were studied using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR). These techniques have proven to be a very powerful tool in studying the structure and dynamics of phospholipid bilayers. In particular, DSC can provide information on the phase transition temperature and cooperativity of the lipid molecules in the absence and presence of the drug. Vibrational spectroscopy is well suited to the study of drug-lipid interactions, since it allows for an investigation of the conformation of phospholipid molecules at different levels in lipid bilayers and follows structural changes that occur during the gel to liquid-crystalline phase transition. NMR supported the determination of the main phase transition temperatures (TC) of 1,2-dihexadecanoyl-sn-glycerol-3-phosphocholine (DPPC). The main phase transition temperature (TC) determined by 1H NMR is comparable with values obtained by DSC for all studied liposomes. The location of cytarabine and etoposide in liposomes was also determined by NMR. Atomic force microscopy (AFM) images, acquired immediately after sample deposition on a mica surface, revealed the spherical shape of lipid vesicles.

Loose nanofiltration membrane for dye/salt separation through interfacial polymerization with in-situ generated TiO2 nanoparticles

NASA Astrophysics Data System (ADS)

Zhang, Qi; Fan, Lin; Yang, Zhen; Zhang, Runnan; Liu, Ya-nan; He, Mingrui; Su, Yanlei; Jiang, Zhongyi

2017-07-01

In this study, a high flux nanofiltration (NF) membrane with hybrid polymer-nanoparticle active layer was fabricated by chemical crosslinking of piperazine (PIP) and 1, 3, 5-benzene tricarbonyl trichloride (TMC). An in-situ generated method was applied to deposit titanium dioxide (TiO2) nanoparticles uniformly on the membrane surface, leading to the enhancement of the surface hydrophilicity, roughness and relative surface area of the polyamide (PA) layer. The morphology of the modified membrane was investigated by scanning electron microscopy (SEM) and Atomic force microscopy (AFM), also energy dispersive X-ray microanalysis (EDX) was used to analyze the distribution of Ti element. Chemical structure was observed by Fourier transmission infrared attenuated total reflectance (FTIR-ATR) spectroscopy. Remarkably, the optimal water flux of the loose NF membrane was 65.0 Lm-2 h-1 bar-1 nearly 5 times as much as the pure PA membrane flux. The rejections of the loose NF membranes for dyes were almost all greater than 95.0%, while the rejection for sodium sulfate (Na2SO4) was only about 17.0%, which indicated that the modified membrane had an impressive potential application for dye desalination and purification.

Modified silicas with different structure of grafted methylphenylsiloxane layer

NASA Astrophysics Data System (ADS)

Bolbukh, Yuliia; Terpiłowski, Konrad; Kozakevych, Roman; Sternik, Dariusz; Deryło-Marczewska, Anna; Tertykh, Valentin

2016-06-01

The method of a chemical assembly of the surface polymeric layer with high contents of the modifying agent was developed. Powders of nanodispersed silica with chemisorbed polymethylphenylsiloxane (PMPS) were synthesized by solvent-free chemical assembly technique with a dimethyl carbonate (DMC) as scission agent. Samples were characterized using FTIR spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM), and elemental analysis (CHN analysis). Coating microstructure, morphology, and hydrophilic-hydrophobic properties of nanoparticles were estimated. The results indicate a significant effect of the PMPS/DMC ratio at each modification stage on hydrophobic properties of modified silicas. Modification with a similar composition of the PMPS/DMC mixture, even with different polymer amount at each stage, provides the worst hydrophobicity. Results suggest that the highest hydrophobicity (contact angle θ = 135°-140°) is achieved in the case when silica modified with the PMPS/DMC mixture using multistage approach that providing a formation of the monomolecular layer of polysiloxane at the first modification step. The characteristics of surface structure were interpreted in terms of density of polymer-silica bonds at the interfaces that, usually, are reduced for modified surfaces, in a coupling with conformation model that accented the shape of chains (arch- and console-like) adsorbed on solid surfaces.

Characterization of 10,12-pentacosadiynoic acid Langmuir-Blodgett monolayers and their use in metal-insulator-metal tunnel devices.

PubMed

Sharma, Saumya; Khawaja, Mohamad; Ram, Manoj K; Goswami, D Yogi; Stefanakos, Elias

2014-01-01

The characterization of Langmuir-Blodgett thin films of 10,12-pentacosadiynoic acid (PDA) and their use in metal-insulator-metal (MIM) devices were studied. The Langmuir monolayer behavior of the PDA film was studied at the air/water interface using surface tension-area isotherms of polymeric and monomeric PDA. Langmuir-Blodgett (LB, vertical deposition) and Langmuir-Schaefer (LS, horizontal deposition) techniques were used to deposit the PDA film on various substrates (glass, quartz, silicon, and nickel-coated film on glass). The electrochemical, electrical and optical properties of the LB and LS PDA films were studied using cyclic voltammetry, current-voltage characteristics (I-V), and UV-vis and FTIR spectroscopies. Atomic force microscopy measurements were performed in order to analyze the surface morphology and roughness of the films. A MIM tunnel diode was fabricated using a PDA monolayer assembly as the insulating barrier, which was sandwiched between two nickel layers. The precise control of the thickness of the insulating monolayers proved critical for electron tunneling to take place in the MIM structure. The current-voltage characteristics of the MIM diode revealed tunneling behavior in the fabricated Ni-PDA LB film-Ni structures.

Silicon heterojunction solar cells with novel fluorinated n-type nanocrystalline silicon oxide emitters on p-type crystalline silicon

NASA Astrophysics Data System (ADS)

Dhar, Sukanta; Mandal, Sourav; Das, Gourab; Mukhopadhyay, Sumita; Pratim Ray, Partha; Banerjee, Chandan; Barua, Asok Kumar

2015-08-01

A novel fluorinated phosphorus doped silicon oxide based nanocrystalline material have been used to prepare heterojunction solar cells on flat p-type crystalline silicon (c-Si) Czochralski (CZ) wafers. The n-type nc-SiO:F:H material were deposited by radio frequency plasma enhanced chemical vapor deposition. Deposited films were characterized in detail by using atomic force microscopy (AFM), high resolution transmission electron microscopy (HRTEM), Raman, fourier transform infrared spectroscopy (FTIR) and optoelectronics properties have been studied using temperature dependent conductivity measurement, Ellipsometry, UV-vis spectrum analysis etc. It is observed that the cell fabricated with fluorinated silicon oxide emitter showing higher initial efficiency (η = 15.64%, Jsc = 32.10 mA/cm2, Voc = 0.630 V, FF = 0.77) for 1 cm2 cell area compare to conventional n-a-Si:H emitter (14.73%) on flat c-Si wafer. These results indicate that n type nc-SiO:F:H material is a promising candidate for heterojunction solar cell on p-type crystalline wafers. The high Jsc value is associated with excellent quantum efficiencies at short wavelengths (<500 nm).

Characterization of bonding between poly(dimethylsiloxane) and cyclic olefin copolymer using corona discharge induced grafting polymerization.

PubMed

Liu, Ke; Gu, Pan; Hamaker, Kiri; Fan, Z Hugh

2012-01-01

Thermoplastics have been increasingly used for fabricating microfluidic devices because of their low cost, mechanical/biocompatible attributes, and well-established manufacturing processes. However, there is sometimes a need to integrate such a device with components made from other materials such as polydimethylsiloxane (PDMS). Bonding thermoplastics with PDMS to produce hybrid devices is not straightforward. We have reported our method to modify the surface property of a cyclic olefin copolymer (COC) substrate by using corona discharge and grafting polymerization of 3-(trimethoxysilyl)propyl methacrylate; the modified surface enabled strong bonding of COC with PDMS. In this paper, we report our studies on the surface modification mechanism using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and contact angle measurement. Using this bonding method, we fabricated a three-layer (COC/PDMS/COC) hybrid device consisting of elastomer-based valve arrays. The microvalve operation was confirmed through the displacement of a dye solution in a fluidic channel when the elastomer membrane was pneumatically actuated. Valve-enabled microfluidic handling was demonstrated. Copyright © 2011 Elsevier Inc. All rights reserved.

Electrochemical synthesis of MoS2 quantum dots embedded nanostructured porous silicon with enhanced electroluminescence property

NASA Astrophysics Data System (ADS)

Shrivastava, Megha; Kumari, Reeta; Parra, Mohammad Ramzan; Pandey, Padmini; Siddiqui, Hafsa; Haque, Fozia Z.

2017-11-01

In this report we present the successful enhancement in electroluminescence (EL) in nanostructured n-type porous silicon (PS) with an idea of embedding luminophorous Molybdenum disulfide (MoS2) quantum dots (QD's). Electrochemical anodization technique was used for the formation of PS surface and MoS2 QD's were prepared using the electrochemical route. Spin coating technique was employed for the proper incorporation of MoS2 QD's within the PS nanostructures. The crystallographic analysis was performed using X-ray diffraction (XRD), Raman and Fourier transform infrared (FT-IR) spectroscopy techniques. However, surface morphology was determined using Transmission electron microscopy (TEM) and Atomic force microscopy (AFM). The optical measurements were performed on photoluminescence (PL) spectrophotometer; additionally for electroluminescence (EL) study special arrangement of instrumental setup was made at laboratory level which provides novelty to this work. A diode prototype was made comprising Ag/MoS2:PS/Silicon/Ag for EL study. The MoS2:PS shows a remarkable concentration dependent enhancement in PL as well as in EL intensities, which paves a way to better utilize this strategy in optoelectronic device applications.

One pot light assisted green synthesis, storage and antimicrobial activity of dextran stabilized silver nanoparticles.

PubMed

Hussain, Muhammad Ajaz; Shah, Abdullah; Jantan, Ibrahim; Tahir, Muhammad Nawaz; Shah, Muhammad Raza; Ahmed, Riaz; Bukhari, Syed Nasir Abbas

2014-12-03

Green synthesis of nanomaterials finds the edge over chemical methods due to its environmental compatibility. Herein, we report green synthesis of silver nanoparticles (Ag NPs) mediated with dextran. Dextran was used as a stabilizer and capping agent to synthesize Ag NPs using silver nitrate (AgNO3) under diffused sunlight conditions. UV-vis spectra of as synthesized Ag nanoparticles showed characteristic surface plasmon band in the range from ~405-452 nm. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies showed spherical Ag NPs in the size regime of ~50-70 nm. Face centered cubic lattice of Ag NPs was confirmed by powder X-ray diffraction (PXRD). FT-IR spectroscopy confirmed that dextran not only acts as reducing agent but also functionalizes the surfaces of Ag NPs to make very stable dispersions. Moreover, on drying, the solution of dextran stabilized Ag NPs resulted in the formation of thin films which were found stable over months with no change in the plasmon band of pristine Ag NPs. The antimicrobial assay of the as synthesized Ag NPs showed remarkable activity. Being significantly active against microbes, the Ag NPs can be explored for antimicrobial medical devices.

High-performance polyamide thin-film composite nanofiltration membrane: Role of thermal treatment

NASA Astrophysics Data System (ADS)

Liu, Baicang; Wang, Shuai; Zhao, Pingju; Liang, Heng; Zhang, Wen; Crittenden, John

2018-03-01

Nanofiltration (NF) membranes have many excellent applications (e.g., removing multivalent ions and pretreating water before reverse osmosis, RO), but their relatively high cost limits their application. Especially in recent years, researchers have paid substantial attention to reducing the cost of NF membranes. In this paper, high-performance NF membranes were fabricated using interfacial polymerization (IP) methods. The polymer concentration, IP solution concentration, and thermal treatment conditions were varied. The synthesized membranes were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), a contact angle goniometer, X-ray photoelectron spectroscopy (XPS), attenuated total reflectance fourier transform infrared (ATR-FTIR) spectroscopy, and performance tests. The results show that water flux was significantly improved using a hot-water thermal treatment method. Our fabricated thermal-treated NF membrane had an approximately 15% higher water permeability with a value of 13.6 L/(m2 h bar) than that of the commercially available GE HL membrane with a value of 11.8 L/(m2 h bar). Our membranes had the same MgSO4 rejection as that of the GE HL membrane. We found that the thermal treatment causes the NF membrane surface to be smoother and have a high crosslinking degree.

Preparation of acetylated nanofibrillated cellulose from corn stalk microcrystalline cellulose and its reinforcing effect on starch films.

PubMed

Cheng, Li; Zhang, Dongli; Gu, Zhengbiao; Li, Zhaofeng; Hong, Yan; Li, Caiming

2018-05-01

Acetylated nanofibrillated cellulose (ANFC) with different degrees of substitution (DS) was prepared from corn-stalk microcrystalline cellulose (MCC) using chemical-mechanical combined processes. The physicochemical properties of nanofibrillated cellulose (NFC) and ANFC were investigated together with the influence of added nanoparticles on the mechanical properties of starch films. The acetylation reaction was monitored by Fourier transform infrared (FT-IR) and titration. Particle size and morphological of NFC and ANFC were studied by atomic force microscope (AFM). The results suggested that NFC had nano-order-unit web-like network with mean diameter of ~24 nm. The thermostability of all samples was found to decrease as the modification extent rose, and mechanical disposal revealed no significant influence on the DS and crystalline structure of cellulose. The ANFC with the DS value of 0.35 demonstrated the best enhancement effect on starch films, with increased tension strength (TS) by 201%. The tensile tests confirmed that the web-like network structure of NFC was more conducive to strength, and proper chemical modification could improve the uniform dispersion of nano-fillers in starch to result in higher strength performances. Copyright © 2018 Elsevier B.V. All rights reserved.

Biodegradation of thermally treated high-density polyethylene (HDPE) by Klebsiella pneumoniae CH001.

PubMed

Awasthi, Shraddha; Srivastava, Pratap; Singh, Pardeep; Tiwary, D; Mishra, Pradeep Kumar

2017-10-01

Biodegradation of plastics, which are the potential source of environmental pollution, has received a great deal of attention in the recent years. We aim to screen, identify, and characterize a bacterial strain capable of degrading high-density polyethylene (HDPE). In the present study, we studied HDPE biodegradation using a laboratory isolate, which was identified as Klebsiella pneumoniae CH001 (Accession No MF399051). The HDPE film was characterized by Universal Tensile Machine (UTM), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), and Atomic Force Microscope (AFM) before and after microbial incubation. We observed that this strain was capable of adhering strongly on HDPE surface and form a thick biofilm, when incubated in nutrient broth at 30 °C on 120 rpm for 60 days. UTM analysis showed a significant decrease in weight (18.4%) and reduction in tensile strength (60%) of HDPE film. Furthermore, SEM analysis showed the cracks on the HDPE surface, whereas AFM results showed an increase in surface roughness after bacterial incubation. Overall, these results indicate that K. pneumoniae CH001 can be used as potential candidate for HDPE degradation in eco-friendly and sustainable manner in the environment.

Effects of the glycerophosphate-polylactic copolymer formation on electrospun fibers

NASA Astrophysics Data System (ADS)

Shen, Wen; Zhang, Guanghua; Li, YaLi; Fan, Guodong

2018-06-01

Poly-lactic (PLA) porous fibers are widely used in tissue engineering scaffolds and many other fields. Non-solvent induced phase separation is one of the best way for preparation of porous fiber. It is difficult to obtain the PLA electrospun porous fibers by phase separation. In this paper, glycerophosphate-polylactic copolymer (GP-PLA) are synthesized with sodium glyceryl phosphate and L-lactide to produce porous fibers. Furthermore, the Gel permeation chromatography (GPC), FT-IR and 1H-NMR are applied for characterizing the obtained copolymers. Thermogravimetric (TG) measurements indicate that the thermal stability of GP-PLA is lower than that of linear PLA. Under 30% humidity, porous GP-PLA fibers are obtained by electrospinning method, the scanning electron microscopy (SEM) refers that through the modification of the molecular structure, GP-PLA fibers are more porous under the same condition. The water contact angle is increased coming with the increase of GP contents. Hydrophilic porous GP-PLA fibers are obtained via solvent phase separation. The relationship between hydrophilicity and surface morphology of materials is further explained by Atomic Force Microscope (AFM). GP-PLA has a potential application in the field of scaffold for tissue engineering.

Chitosan-doped-hybrid/TiO2 nanocomposite based sol-gel coating for the corrosion resistance of aluminum metal in 3.5% NaCl medium.

PubMed

J, Balaji; M G, Sethuraman

2017-11-01

The study outlines the role of chitosan, a biopolymer on corrosion behavior of Hy/nano-TiO 2 based sol-gel coating over aluminum metal. In this study organic-inorganic hybrid sols were synthesized through hydrolysis and condensation of 3-glycidoxypropyltrimethoxy silane (GPTMS), tetraethoxysilane (TEOS) and titanium (IV) isopropoxide (TIP) in acidic solution. Chitosan was doped into sol-gel matrix and self-assembled over aluminum substrate. The resultant chitosan-doped-Hy/nano-TiO 2 sol-gel coating was characterized by Fourier Transform Infrared (FT-IR) spectra, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Energy-Dispersive X-ray Spectroscopy (EDX) analyses. The as-tailored aluminum substrate was evaluated for corrosion resistance in neutral medium. The protection ability of these coatings was evaluated by electrochemical impedance studies (EIS) and potentiodynamic polarization (PP) measurements in 3.5% NaCl medium. The EIS and PP results showed that chitosan-doped- Hy/nano-TiO 2 sol-gel coating exhibited better protection from corrosion than the undoped Hy/TiO 2 nanocomposite coating. Copyright © 2017 Elsevier B.V. All rights reserved.

Superficial physicochemical properties of polyurethane biomaterials as osteogenic regulators in human mesenchymal stem cells fates.

PubMed

Shahrousvand, Mohsen; Sadeghi, Gity Mir Mohamad; Shahrousvand, Ehsan; Ghollasi, Marzieh; Salimi, Ali

2017-08-01

All of the cells' interactions are done through their surfaces. Evaluation of surface physicochemical scaffolds along with other factors is important and determines the fate of stem cells. In this work, biodegradable and biocompatible polyester/polyether based polyurethanes (PUs) were synthesized by polycaprolactone diol (PCL) and poly (tetra methylene ether) glycol (PTMEG) as the soft segment. To assess better the impact of surface parameters such as stiffness and roughness effects on osteogenic differentiation of the human mesenchymal stem cell (hMSC), the dimension effect of substrates was eliminated and two-dimensional membranes were produced by synthesized polyurethane. Surface and bulk properties of prepared 2D membranes such as surface chemistry, roughness, stiffness and tensile behavior were evaluated by Attenuated total reflectance Fourier transform infrared (ATR-FTIR), atomic force microscopy (AFM) and tensile behavior. The prepared 2D PU films had suitable hydrophilicity, biodegradability, water absorption, surface roughness and bulk strength. The hMSCs showed greater osteogenesis expression in PU substrates with more roughness and stiffness than others. The results demonstrated that surface parameters along with other differentiation cues have a synergistic effect on stem cells fates. Copyright © 2017 Elsevier B.V. All rights reserved.

Flexible magnetic polyurethane/Fe2O3 nanoparticles as organic-inorganic nanocomposites for biomedical applications: Properties and cell behavior.

PubMed

Shahrousvand, Mohsen; Hoseinian, Monireh Sadat; Ghollasi, Marzieh; Karbalaeimahdi, Ali; Salimi, Ali; Tabar, Fatemeh Ahmadi

2017-05-01

Nowadays, the discovery of cell behaviors and their responses in communication with the stem cell niches and/or microenvironments are one of the major topics in tissue engineering and regenerative medicine. In this study, incorporated organic-inorganic polyurethane (PU) nanocomposites were prepared for better understanding of cell signaling and the effect of magnetite nanoparticles on cell proliferation and cell responses. The properties of PU-IONs were evaluated by fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic-force microscopy (AFM), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS). The presence of the iron oxide nanoparticles (IONs) affects on the properties of polyurethane nanocomposites such as bulk morphology, mechanical, electrochemical, and biological properties. The electrical conductivity and hydrophilicity of PU-IONs were improved by increasing the magnetite nanoparticles; therefore water absorption, biodegradation and cell viability were changed. The biocompatibility of PU-IONs was investigated by MTT assay, cell attachment and cell staining. According to the results, the magnetite polyurethane nanocomposites could be a potential choice for cell therapy and tissue engineering, especially nerve repair. Copyright © 2016 Elsevier B.V. All rights reserved.

Structural, optical, electrochemical and photovoltaic studies of spider web like Silver Indium Diselenide Quantum dots synthesized by ligand mediated colloidal sol-gel approach

NASA Astrophysics Data System (ADS)

Adhikari, Tham; Pathak, Dinesh; Wagner, Tomas; Jambor, Roman; Jabeen, Uzma; Aamir, Muhammad; Nunzi, Jean-Michel

2017-11-01

Silver indium diselenide quantum dots were successively synthesized by colloidal sol-gel method by chelating with organic ligand oleylamine (OLA). The particle size was studied by transmission electron microscopy (TEM) and the size was found about 10 nm. X-ray diffraction (XRD) was used to study crystalline structure of the nanocrystals. The grain size and morphology were further studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The elemental composition was studied by X-ray photon electron spectroscopy (XPS) and energy dispersive x-ray spectroscopy (EDAX). The capping property of OLA in nanocrystal was also demonstrated by Fourier Transform Infrared spectroscopy (FTIR). The band gap was calculated from both cyclic voltammetry and optical absorption and suggest quantum confinement. The solution processed bilayer thin film solar cells were fabricated with n-type Zinc oxide using doctor blading/spin coating method and their photovoltaic performance was studied. The best device sintered at 450 °C showed an efficiency 0.75% with current density of 4.54 mAcm-2, open-circuit voltage 0.44 V and fill factor 39.4%.

Mechanistic study of wettability alteration of oil-wet sandstone surface using different surfactants

NASA Astrophysics Data System (ADS)

Hou, Bao-feng; Wang, Ye-fei; Huang, Yong

2015-03-01

Different analytical methods including Fourier transform infrared (FTIR), atomic force microscopy (AFM), zeta potential measurements, contact angle measurements and spontaneous imbibition tests were utilized to make clear the mechanism for wettability alteration of oil-wet sandstone surface using different surfactants. Results show that among three types of surfactants including cationic surfactants, anionic surfactants and nonionic surfactants, the cationic surfactant CTAB demonstrates the best effect on the wettability alteration of oil-wet sandstone surface. The positively charged head groups of CTAB molecules and carboxylic acid groups from crude oil could interact to form ion pairs, which could be desorbed from the solid surface and solubilized into the micelle formed by CTAB. Thus, the water-wetness of the solid surface is improved. Nonionic surfactant TX-100 could be adsorbed on oil-wet sandstone surface through hydrogen bonds and hydrophobic interaction to alter the wettability of oil-wet solid surface. The wettability alteration of oil-wet sandstone surface using the anionic surfactant POE(1) is caused by hydrophobic interaction. Due to the electrostatic repulsion between the anionic surfactant and the negatively charged surface, POE(1) shows less effect on the wettability alteration of oil-wet sandstone surface.

On the role of extracellular polymeric substances during early stages of Xylella fastidiosa biofilm formation.

PubMed

Lorite, Gabriela S; de Souza, Alessandra A; Neubauer, Daniel; Mizaikoff, Boris; Kranz, Christine; Cotta, Mônica A

2013-02-01

The structural integrity and protection of bacterial biofilms are intrinsically associated with a matrix of extracellular polymeric substances (EPS) produced by the bacteria cells. However, the role of these substances during biofilm adhesion to a surface remains largely unclear. In this study, the influence of EPS on Xylella fastidiosa biofilm formation was investigated. This bacterium is associated with economically important plant diseases; it presents a slow growth rate and thus allows us to pinpoint more precisely the early stages of cell-surface adhesion. Scanning electron microscopy and atomic force microscopy show evidence of EPS production in such early stages and around individual bacteria cells attached to the substrate surface even a few hours after inoculation. In addition, EPS formation was investigated via attenuated total reflectance (ATR) Fourier transform infrared spectroscopy (FTIR). To this end, X. fastidiosa cells were inoculated within an ATR liquid cell assembly. IR-ATR spectra clearly reveal EPS formation already during the early stages of X. fastidiosa biofilm formation, thereby providing supporting evidence for the hypothesis of the relevance of the EPS contribution to the adhesion process. Copyright © 2012 Elsevier B.V. All rights reserved.

Tungsten oxide--fly ash oxide composites in adsorption and photocatalysis.

PubMed

Visa, Maria; Bogatu, Cristina; Duta, Anca

2015-05-30

A novel composite based on tungsten oxide and fly ash was hydrothermally synthetized to be used as substrate in the advanced treatment of wastewaters with complex load resulted from the textile industry. The proposed treatment consists of one single step process combining photocatalysis and adsorption. The composite's crystalline structure was investigated by X-ray diffraction and FTIR, while atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to analyze the morphology. The adsorption capacity and photocatalytic properties of the material were tested on mono- and multi-pollutants systems containing two dyes (Bemacid Blau - BB and Bemacid Rot - BR) and one heavy metal ion-Cu(2+), and the optimized process conditions were identified. The results indicate better removal efficiencies using the novel composite material in the combined adsorption and photocatalysis, as compared to the separated processes. Dyes removal was significantly enhanced in the photocatalytic process by adding hydrogen peroxide and the mechanism was presented and discussed. The pseudo second order kinetics model best fitted the experimental data, both in the adsorption and in the combined processes. The kinetic parameters were calculated and correlated with the properties of the composite substrate. Copyright © 2015 Elsevier B.V. All rights reserved.

Development and in vitro evaluation of oxytetracycline-loaded PMMA nanoparticles for oral delivery against anaplasmosis.

PubMed

SadguruPrasad, Lakshminarayana Turuvekere; Madhusudhan, Basavaraj; Kodihalli B, Prakash; Ghosh, Prahlad Chandra

2017-02-01

Poly-methyl methacrylate (PMMA) polymer with remarkable properties and merits are being preferred in various biomedical applications due to its biocompatibility, non-toxicity and cost effectiveness. In this investigation, oxytetracycline-loaded PMMA nanoparticles were prepared using nano-precipitation method for the treatment of anaplasmosis. The prepared nanoparticles were characterised using dynamic light scattering (DLS), atomic force microscopy (AFM), differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy. The mean average diameter of the nanoparticles ranged between 190-240 nm and zeta potential was found to be -19 mV. The drug loading capacity and entrapment efficiency of nanoparticles was found varied between 33.7-62.2% and 40.5-60.0%. The in vitro drug release profile exhibited a biphasic phenomenon indicating controlled drug release. The uptake of coumarin-6(C-6)-loaded PMMA nanoparticles in Plasmodium falciparum ( Pf 3D7) culture model was studied. The preferential uptake of C-6-loaded nanoparticles by the Plasmodium infected erythrocytes in comparison with the uninfected erythrocytes was observed under fluorescence microscopy. These findings suggest that oxytetracycline-loaded PMMA nanoparticles were found to be an effective oral delivery vehicle and an alternative pharmaceutical formulation in anaplasmosis treatment, too.

A surface-mediated siRNA delivery system developed with chitosan/hyaluronic acid-siRNA multilayer films through layer-by-layer self-assembly

NASA Astrophysics Data System (ADS)

Wu, Lijuan; Wu, Changlin; Liu, Guangwan; Liao, Nannan; Zhao, Fang; Yang, Xuxia; Qu, Hongyuan; Peng, Bo; Chen, Li; Yang, Guang

2016-12-01

siRNA delivery remains highly challenging because of its hydrophilic and anionic nature and its sensitivity to nuclease degradation. Effective siRNA loading and improved transfection efficiency into cells represents a key problem. In our study, we prepared Chitosan/Hyaluronic acid-siRNA multilayer films through layer-by-layer self-assembly, in which siRNAs can be effectively loaded and protected. The construction process was characterized by FTIR, 13C NMR (CP/MAS), UV-vis spectroscopy, and atomic force microscopy (AFM). We presented the controlled-release performance of the films during incubation in 1 M NaCl solution for several days through UV-vis spectroscopy and polyacrylamide gel electrophoresis (PAGE). Additionally, we verified the stability and integrity of the siRNA loaded on multilayer films. Finally, the biological efficacy of the siRNA delivery system was evaluated via cells adhesion and gene silencing analyses in eGFP-HEK 293T cells. This new type of surface-mediated non-viral multilayer films may have considerable potential in the localized and controlled-release delivery of siRNA in mucosal tissues, and tissue engineering application.

Preparation and mechanical properties of layers made of recombinant spider silk proteins and silk from silk worm

NASA Astrophysics Data System (ADS)

Junghans, F.; Morawietz, M.; Conrad, U.; Scheibel, T.; Heilmann, A.; Spohn, U.

2006-02-01

Layers of recombinant spider silks and native silks from silk worms were prepared by spin-coating and casting of various solutions. FT-IR spectra were recorded to investigate the influence of the different mechanical stress occurring during the preparation of the silk layers. The solubility of the recombinant spider silk proteins SO1-ELP, C16, AQ24NR3, and of the silk fibroin from Bombyx mori were investigated in hexafluorisopropanol, ionic liquids and concentrated salt solutions. The morphology and thickness of the layers were determined by Atomic Force Microscopy (AFM) or with a profilometer. The mechanical behaviour was investigated by acoustic impedance analysis by using a quartz crystal microbalance (QCMB) as well as by microindentation. The density of silk layers (d<300 nm) was determined based on AFM and QCMB measurements. At silk layers thicker than 300 nm significant changes of the half-band-half width can be correlated with increasing energy dissipation. Microhardness measurements demonstrate that recombinant spider silk and sericine-free Bombyx mori silk layers achieve higher elastic penetration modules EEP and Martens hardness values HM than those of polyethylenterephthalate (PET) and polyetherimide (PEI) foils.

Structure and Dynamics Investigations of Sr/Ca-Doped LaPO 4 Proton Conductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

al-Wahish, Amal; al-Binni, U.; Tetard, L.

Proton conductors loom out of the pool of candidate materials with great potential to boost hydrogen alternatives to fossil-based resources for energy. Acceptor doped lanthanum orthophosphates are considered for solid oxide fuel cells (SOFCs) for their potential stability and conductivity at high temperature. By exploring the crystal and defect structure of x% Sr/Ca-doped LaPO 4 with different nominal Sr/Ca concentrations (x = 0 – 10) with Neutron powder diffraction (NPD) and X-ray powder diffraction (XRD), we confirm that Sr/Ca-doped LaPO 4 can exist as self-supported structures at high temperatures during solid oxide fuel cell operation. Thermal stability, surface topography, sizemore » distribution are also studied to better understand the proton conductivity for dry and wet compounds obtained at sintering temperatures ranging from 1200 to 1400 °C using a combination of scanning electron microscopy (SEM), Atomic Force Microscopy (AFM), Fourier transform infrared spectroscopy (FTIR) and electrochemical impedance spectroscopy (EIS). In conclusion, the results suggest that Sr doped samples exhibit the highest proton conductivity of our samples and illustrate the impact of material design and versatile characterization schemes on the development of proton conductors with superior functionality.« less

Structure and self-assembly properties of a new chitosan-based amphiphile.

PubMed

Huang, Yuping; Yu, Hailong; Guo, Liang; Huang, Qingrong

2010-06-17

A new chitosan-based amphiphile, octanoyl-chitosan-polyethylene glycol monomethyl ether (acylChitoMPEG), has been prepared using both hydrophobic octanoyl and hydrophilic polyethylene glycol monomethyl ether (MPEG) substitutions. The success of synthesis was confirmed by Fourier transform infrared (FT-IR) and (1)H NMR spectroscopy. The synthesized acylChitoMPEG exhibited good solubility in either aqueous solution or common organic solvents such as ethanol, acetone, and CHCl(3). The self-aggregation behavior of acylChitoMPEG in solutions was studied by a combination of pyrene fluorescence technique, dynamic light scattering, atomic force microscopy, and small-angle X-ray scattering (SAXS). The critical aggregation concentration (CAC) and hydrodynamic diameter were found to be 0.066 mg/mL and 24.4 nm, respectively. SAXS results suggested a coiled structure of the triple helical acylChitoMPEG backbone with the hydrophobic moieties hiding in the center of the backbone, and the hydrophilic MPEG chains surrounding the acylChitoMPEG backbone in a random Gaussian chain conformation. Cytotoxicity results showed that acylChitoMPEG exhibited negligible cytotoxicity even at concentrations as high as 1.0 mg/mL. All results implied that acylChitoMPEG has the potential to be used for biological or medical applications.

One Step Assembly of Thin Films of Carbon Nanotubes on Screen Printed Interface for Electrochemical Aptasensing of Breast Cancer Biomarker.

PubMed

Nawaz, Muhammad Azhar Hayat; Rauf, Sajid; Catanante, Gaelle; Nawaz, Mian Hasnain; Nunes, Gilvanda; Marty, Jean Louis; Hayat, Akhtar

2016-10-06

Thin films of organic moiety functionalized carbon nanotubes (CNTs) from a very well-dispersed aqueous solution were designed on a screen printed transducer surface through a single step directed assembly methodology. Very high density of CNTs was obtained on the screen printed electrode surface, with the formation of a thin and uniform layer on transducer substrate. Functionalized CNTs were characterized by X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and Brunauer-Emmett- Teller (BET) surface area analyzer methodologies, while CNT coated screen printed transducer platform was analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The proposed methodology makes use of a minimum amount of CNTs and toxic solvents, and is successfully demonstrated to form thin films over macroscopic areas of screen printed carbon transducer surface. The CNT coated screen printed transducer surface was integrated in the fabrication of electrochemical aptasensors for breast cancer biomarker analysis. This CNT coated platform can be applied to immobilize enzymes, antibodies and DNA in the construction of biosensor for a broad spectrum of applications.

One Step Assembly of Thin Films of Carbon Nanotubes on Screen Printed Interface for Electrochemical Aptasensing of Breast Cancer Biomarker

PubMed Central

Nawaz, Muhammad Azhar Hayat; Rauf, Sajid; Catanante, Gaelle; Nawaz, Mian Hasnain; Nunes, Gilvanda; Louis Marty, Jean; Hayat, Akhtar

2016-01-01

Thin films of organic moiety functionalized carbon nanotubes (CNTs) from a very well-dispersed aqueous solution were designed on a screen printed transducer surface through a single step directed assembly methodology. Very high density of CNTs was obtained on the screen printed electrode surface, with the formation of a thin and uniform layer on transducer substrate. Functionalized CNTs were characterized by X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and Brunauer–Emmett–Teller (BET) surface area analyzer methodologies, while CNT coated screen printed transducer platform was analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The proposed methodology makes use of a minimum amount of CNTs and toxic solvents, and is successfully demonstrated to form thin films over macroscopic areas of screen printed carbon transducer surface. The CNT coated screen printed transducer surface was integrated in the fabrication of electrochemical aptasensors for breast cancer biomarker analysis. This CNT coated platform can be applied to immobilize enzymes, antibodies and DNA in the construction of biosensor for a broad spectrum of applications. PMID:27782067

In vitro testing of curcumin based composites coatings as antitumoral systems against osteosarcoma cells

NASA Astrophysics Data System (ADS)

Tirca, I.; Mitran, V.; Marascu, V.; Brajnicov, S.; Ion, V.; Stokker-Cheregi, F.; Popovici, I. A.; Cimpean, A.; Dinca, V.; Dinescu, M.

2017-12-01

In this work, we propose a new design for biodegradable composite coatings obtained by laser methods, which are aimed at evaluating the effects of active antitumoral elements on osteosarcoma cells. Our approach relies on embedding curcumin, which is a natural polyphenol having antitumoral properties, within biodegradable copolymer coatings (i.e. polyvinyl alcohol-polyethylene glycol - PVA-PEG) by using matrix assisted pulsed laser evaporation (MAPLE). The structural and morphological characteristics of the coatings were tailored by using different solvents (water, ethanol, benzene, dimethylsufoxide) as deposition matrix. The morphological characteristics of the resulting films were investigated by atomic force microscopy (AFM), whereas their chemical composition was characterized by Fourier transform infrared spectroscopy (FTIR). These characteristics were correlated with the degradation behavior by using ellipsometry (SE) and AFM measurements data. The in vitro study of the MG-63 osteosarcoma cell behavior indicates that the developed hybrid coatings significantly decreased osteosarcoma cell viability and proliferation potential. The physico-chemical characteristics of the thin films, along with the preliminary in vitro analyses, suggest that our developed polymeric hybrid coatings represent an efficient way to tackle the design of antitumoral surfaces, with applications in biomedicine.

Electrochemical DNA sensor for Neisseria meningitidis detection.

PubMed

Patel, Manoj K; Solanki, Pratima R; Kumar, Ashok; Khare, Shashi; Gupta, Sunil; Malhotra, Bansi D

2010-08-15

Meningitis sensor based on nucleic acid probe of Neisseria meningitidis has been fabricated by immobilization of 5'-thiol end labeled single stranded deoxyribonucleic acid probe (ssDNA-SH) onto gold (Au) coated glass electrode. This ssDNA-SH/Au electrode hybridized with the genomic DNA (G-dsDNA/Au) and amplified DNA (PCR-dsDNA/Au) has been characterized using atomic force microscopy (AFM), Fourier transforms infrared spectroscopy (FT-IR) and electrochemical techniques. The ssDNA-SH/Au electrode can specifically detect upto 10-60 ng/microl of G-dsDNA-SH/Au and PCR-dsDNA-SH/Au of meningitis within 60s of hybridization time at 25 degrees C by cyclic voltammetry (CV) using methylene blue (MB) as electro-active DNA hybridization indicator. The values of sensitivities of the G-dsDNA-SH/Au and PCR-dsDNA-SH/Au electrodes have been determined as 0.0115 microA/ng cm(-2) and 0.0056 microA/ng cm(-2), respectively with regression coefficient (R) as 0.999. This DNA bioelectrode is stable for about 4 months when stored at 4 degrees C. Copyright 2010 Elsevier B.V. All rights reserved.

Functional Micrococcus lysodeikticus layers deposited by laser technique for the optical sensing of lysozyme.

PubMed

Dinca, Valentina; Zaharie-Butucel, Diana; Stanica, Luciana; Brajnicov, Simona; Marascu, Valentina; Bonciu, Anca; Cristocea, Andra; Gaman, Laura; Gheorghiu, Mihaela; Astilean, Simion; Vasilescu, Alina

2018-02-01

Whole cell optical biosensors, made by immobilizing whole algal, bacterial or mammalian cells on various supports have found applications in several fields, from ecology and ecotoxicity testing to biopharmaceutical production or medical diagnostics. We hereby report the deposition of functional bacterial layers of Micrococcus lysodeikticus (ML) via Matrix-Assisted Pulsed Laser Evaporation (MAPLE) on poly(diallyldimethylamonium) (PDDA)-coated-glass slides and their application as an optical biosensor for the detection of lysozyme in serum. Lysozyme is an enzyme upregulated in inflammatory diseases and ML is an enzymatic substrate for this enzyme. The MAPLE-deposited bacterial interfaces were characterised by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Fourier-Transformed Infrared Spectroscopy (FTIR), Raman and optical microscopy and were compared with control interfaces deposited via layer-by-layer on the same substrate. After MAPLE deposition and coating with graphene oxide (GO), ML-modified interfaces retained their functionality and sensitivity to lysozyme's lytic action. The optical biosensor detected lysozyme in undiluted serum in the clinically relevant range up to 10μgmL -1 , in a fast and simple manner. Copyright © 2017 Elsevier B.V. All rights reserved.

PREFACE: NC-AFM 2003: Proceedings of the 6th International Conference on Non-contact Atomic Force Microscopy

NASA Astrophysics Data System (ADS)

Reichling, Michael

2004-02-01

Direct nanoscale and atomic resolution imaging is a key issue in nanoscience and nanotechnology. The invention of the dynamic force microscope in the early 1990s was an important step forward in this direction as this instrument provides a universal tool for measuring the topography and many other physical and chemical properties of surfaces at the nanoscale. Operation in the so-called non-contact mode now allows direct atomic resolution imaging of electrically insulating surfaces and nanostructures which has been an unsolved problem during the first decade of nanotechnology. Today, we face a most rapid development of the technique and an extension of its capabilities far beyond imaging; atomically resolved force spectroscopy provides information about local binding properties and researchers now develop sophisticated schemes of force controlled atomic manipulation with the tip of the force microscope. Progress in the field of non-contact force microscopy is discussed at the annually held NC-AFM conferences that are part of a series started in 1998 with a meeting in Osaka, Japan. The 6th International Conference on Non-contact Atomic Force Microscopy took place in Dingle, Ireland, from 31 August to 3 September 2003 and this special issue is a compilation of the original publications of work presented at this meeting. The papers published here well reflect recent achievements, current trends and some of the challenging new directions in non-contact force microscopy that have been discussed during the most stimulating conference days in Dingle. Fundamental aspects of forces and dissipation relevant in imaging and spectroscopy have been covered by experimental and theoretical contributions yielding a more detailed understanding of tip--surface interaction in force microscopy. Novel and improved imaging and spectroscopy techniques have been introduced that either improve the performance of force microscopy or pave the way towards new functionalities and applications. With regard to studies on the specific systems investigated, there was a strong emphasis on oxides and ionics, as well as on organic systems. Following previous pioneering work in uncovering the atomic structure of insulating oxides with force microscopy, it was shown in the meeting that this important class of materials is now accessible for a quantitative atomic scale surface characterization. Single organic molecules and ordered organic layers are building blocks for functional nanostructures currently developed in many laboratories for applications in molecular electronics and sensor technologies. The Dingle conference impressively demonstrated that dynamic force microscopy is ready for its application as an analytical tool for these promising future nanotechnologies. The meeting was a great success scientifically and participants enjoyed the beauty of the conference site. I would like to thank all members of the international steering committee, the programme committee and the co-chairs, J Pethica, A Shluger and G Thornton, for their efforts in preparing the meeting. The members of the local organising committee, J Ballentine-Armstrong, G Cross, S Dunne, S Jarvis and Ö Özer, kept the meeting running smoothly and created a very pleasant atmosphere. The generous financial support from Science Foundation Ireland (SFI), is greatly appreciated; SFI is dramatically raising the profile of Irish science. I would also like to express my sincere gratitude to N Couzin and the journal team from Institute of Physics Publishing for their editorial management and perfect co-operation in the preparation of this special issue.

Atomic Force Microscopy of Biological Membranes

PubMed Central

Frederix, Patrick L.T.M.; Bosshart, Patrick D.; Engel, Andreas

2009-01-01

Abstract Atomic force microscopy (AFM) is an ideal method to study the surface topography of biological membranes. It allows membranes that are adsorbed to flat solid supports to be raster-scanned in physiological solutions with an atomically sharp tip. Therefore, AFM is capable of observing biological molecular machines at work. In addition, the tip can be tethered to the end of a single membrane protein, and forces acting on the tip upon its retraction indicate barriers that occur during the process of protein unfolding. Here we discuss the fundamental limitations of AFM determined by the properties of cantilevers, present aspects of sample preparation, and review results achieved on reconstituted and native biological membranes. PMID:19167286

Atomic force microscopy captures length phenotypes in single proteins

PubMed Central

Carrion-Vazquez, Mariano; Marszalek, Piotr E.; Oberhauser, Andres F.; Fernandez, Julio M.

1999-01-01

We use single-protein atomic force microscopy techniques to detect length phenotypes in an Ig module. To gain amino acid resolution, we amplify the mechanical features of a single module by engineering polyproteins composed of up to 12 identical repeats. We show that on mechanical unfolding, mutant polyproteins containing five extra glycine residues added to the folded core of the module extend 20 Å per module farther than the wild-type polyproteins. By contrast, similar insertions near the N or C termini have no effect. Hence, our atomic force microscopy measurements readily discriminate the location of the insert and measure its size with a resolution similar to that of NMR and x-ray crystallography. PMID:10500169

Preparation and atomic force microscopy of CTAB stabilized polythiophene nanoparticles thin film

DOE Office of Scientific and Technical Information (OSTI.GOV)

Graak, Pinki; Devi, Ranjna; Kumar, Dinesh

2016-05-06

Polythiophene nanoparticles were synthesized by iron catalyzed oxidative polymerization method. Polythiophene formation was detected by UV-Visible spectroscopy with λmax 375nm. Thin films of CTAB stabilized polythiophene nanoparticles was deposited on n-type silicon wafer by spin coating technique at 3000rpm in three cycles. Thickness of the thin films was computed as 300-350nm by ellipsometry. Atomic force micrscopyrevealws the particle size of polymeric nanoparticles in the range of 30nm to 100nm. Roughness of thinfilm was also analyzed from the atomic force microscopy data by Picoimage software. The observed RMS value lies in the range of 6 nm to 12 nm.

Inter-atomic force constants of BaF{sub 2} by diffuse neutron scattering measurement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sakuma, Takashi, E-mail: sakuma@mx.ibaraki.ac.jp; Makhsun,; Sakai, Ryutaro

2015-04-16

Diffuse neutron scattering measurement on BaF{sub 2} crystals was performed at 10 K and 295 K. Oscillatory form in the diffuse scattering intensity of BaF{sub 2} was observed at 295 K. The correlation effects among thermal displacements of F-F atoms were obtained from the analysis of oscillatory diffuse scattering intensity. The force constants among neighboring atoms in BaF{sub 2} were determined and compared to those in ionic crystals and semiconductors.

Coercion from the Air: The United States Use of Airpower to Influence End of Conflict Negotiations

DTIC Science & Technology

2017-05-25

shock of two atomic bombs drove the Japanese to surrender. In the months and days leading to the armistice in Korea, Far East Air Force (FEAF...mainland by the Twentieth Air Force and the shock of two atomic bombs drove the Japanese to surrender. In the months and days leading to the...increasing destruction brought upon the Japanese population and war-making capacity combined with the shock of two atomic bombs to drive the Japanese towards

Laboratory Studies of Ice Growth in the Presence of Oxygen Atoms

NASA Astrophysics Data System (ADS)

Morgan, C. G.; Boulter, J. E.; Marschall, J.

2003-12-01

In the mesopause region, where noctilucent clouds (NLCs) form and polar summertime echoes are present, atomic oxygen is the dominant reactive species. Observations by Gumbel et al. (1998) reveal sharp gradients and distinctive minima in oxygen atom concentration coinciding with observed NLC layers. These observations suggest an interaction between oxygen atoms and NLC particles. Recent laboratory studies conclude that the uptake coefficient of atomic oxygen on ice is not large enough to change the gas-phase concentrations in the mesosphere lower thermosphere (MLT) region (Murray and Plane, 2003). However, the question of whether or not atomic oxygen can affect the formation and growth of ice has not been experimentally addressed. To gain insight into possible interactions between atomic oxygen and ice surfaces, we directly measure ice growth rates at temperatures associated with the summertime mesopause region (110-150 K), with and without exposure of the growing ice layer to partially dissociated oxygen. A liquid nitrogen cooled cryostat is used to control the temperature of a gold mirror in a high vacuum chamber. Water vapor, either from the residual background or from an introduced source, is allowed to condense on the mirror. A microwave discharge is used to partially dissociate an oxygen stream, which is sampled into the chamber through a small orifice facing the gold mirror. Grazing angle Fourier transform infrared reflection absorption spectroscopy (FTIR-RAS) is used to monitor the rate of ice growth. Preliminary results at 130 K indicate that the ice growth rate in the presence of oxygen slows when the microwave discharge is activated and the ratio of water to oxygen is low. For H2O/O2 = ˜0.3 %, at a total chamber pressure of about 7 μ Torr, the growth rate reduction amounts to 24+/-9 %. Changes in the FTIR-RAS absorption profile of the OH stretching vibrations are also noted, which may indicate changes in ice morphology. Both results suggest that the presence of atomic oxygen influences how ice forms and grows, though more extensive experimentation is required to solidify this conclusion. This testing is underway and results will be presented and discussed. Gumbel, J., D. P. Murtagh, P. J. Espy, and G. Witt, "Odd Oxygen measurements during the Noctilucent Cloud 93 rocket campaign," Journal of Geophysical Research, Vol. 103, No. A10, 1998, pp. 23,399-23,414. Murray, B. J, and J. M. C. Plane, personal communications, 2003

Mechanical properties of cellulose nanomaterials studied by contact resonance atomic force microscopy

Treesearch

Ryan Wagner; Robert J. Moon; Arvind Raman

2016-01-01

Quantification of the mechanical properties of cellulose nanomaterials is key to the development of new cellulose nanomaterial based products. Using contact resonance atomic force microscopy we measured and mapped the transverse elastic modulus of three types of cellulosic nanoparticles: tunicate cellulose nanocrystals, wood cellulose nanocrystals, and wood cellulose...

Coffee Cup Atomic Force Microscopy

ERIC Educational Resources Information Center

Ashkenaz, David E.; Hall, W. Paige; Haynes, Christy L.; Hicks, Erin M.; McFarland, Adam D.; Sherry, Leif J.; Stuart, Douglas A.; Wheeler, Korin E.; Yonzon, Chanda R.; Zhao, Jing; Godwin, Hilary A.; Van Duyne, Richard P.

2010-01-01

In this activity, students use a model created from a coffee cup or cardstock cutout to explore the working principle of an atomic force microscope (AFM). Students manipulate a model of an AFM, using it to examine various objects to retrieve topographic data and then graph and interpret results. The students observe that movement of the AFM…

Topographical and Chemical Imaging of a Phase Separated Polymer Using a Combined Atomic Force Microscopy/Infrared Spectroscopy/Mass Spectrometry Platform

DOE PAGES

Tai, Tamin; Karácsony, Orsolya; Bocharova, Vera; ...

2016-02-18

This article describes how the use of a hybrid atomic force microscopy/infrared spectroscopy/mass spectrometry imaging platform was demonstrated for the acquisition and correlation of nanoscale sample surface topography and chemical images based on infrared spectroscopy and mass spectrometry.

Surface structure. Subatomic resolution force microscopy reveals internal structure and adsorption sites of small iron clusters.

PubMed

Emmrich, Matthias; Huber, Ferdinand; Pielmeier, Florian; Welker, Joachim; Hofmann, Thomas; Schneiderbauer, Maximilian; Meuer, Daniel; Polesya, Svitlana; Mankovsky, Sergiy; Ködderitzsch, Diemo; Ebert, Hubert; Giessibl, Franz J

2015-04-17

Clusters built from individual iron atoms adsorbed on surfaces (adatoms) were investigated by atomic force microscopy (AFM) with subatomic resolution. Single copper and iron adatoms appeared as toroidal structures and multiatom clusters as connected structures, showing each individual atom as a torus. For single adatoms, the toroidal shape of the AFM image depends on the bonding symmetry of the adatom to the underlying structure [twofold for copper on copper(110) and threefold for iron on copper(111)]. Density functional theory calculations support the experimental data. The findings correct our previous work, in which multiple minima in the AFM signal were interpreted as a reflection of the orientation of a single front atom, and suggest that dual and triple minima in the force signal are caused by dimer and trimer tips, respectively. Copyright © 2015, American Association for the Advancement of Science.

Force-field parameters of the Psi and Phi around glycosidic bonds to oxygen and sulfur atoms.

PubMed

Saito, Minoru; Okazaki, Isao

2009-12-01

The Psi and Phi torsion angles around glycosidic bonds in a glycoside chain are the most important determinants of the conformation of a glycoside chain. We determined force-field parameters for Psi and Phi torsion angles around a glycosidic bond bridged by a sulfur atom, as well as a bond bridged by an oxygen atom as a preparation for the next study, i.e., molecular dynamics free energy calculations for protein-sugar and protein-inhibitor complexes. First, we extracted the Psi or Phi torsion energy component from a quantum mechanics (QM) total energy by subtracting all the molecular mechanics (MM) force-field components except for the Psi or Phi torsion angle. The Psi and Phi energy components extracted (hereafter called "the remaining energy components") were calculated for simple sugar models and plotted as functions of the Psi and Phi angles. The remaining energy component curves of Psi and Phi were well represented by the torsion force-field functions consisting of four and three cosine functions, respectively. To confirm the reliability of the force-field parameters and to confirm its compatibility with other force-fields, we calculated adiabatic potential curves as functions of Psi and Phi for the model glycosides by adopting the Psi and Phi force-field parameters obtained and by energetically optimizing other degrees of freedom. The MM potential energy curves obtained for Psi and Phi well represented the QM adiabatic curves and also these curves' differences with regard to the glycosidic oxygen and sulfur atoms. Our Psi and Phi force-fields of glycosidic oxygen gave MM potential energy curves that more closely represented the respective QM curves than did those of the recently developed GLYCAM force-field. (c) 2009 Wiley Periodicals, Inc.

Nonperturbative theory of atom-surface interaction: corrections at short separations

NASA Astrophysics Data System (ADS)

Bordag, M.; Klimchitskaya, G. L.; Mostepanenko, V. M.

2018-02-01

The nonperturbative expressions for the free energy and force of interaction between a ground-state atom and a real-material surface at any temperature are presented. The transition to the Matsubara representation is performed, whereupon the comparison is made with the commonly used perturbative results based on the standard Lifshitz theory. It is shown that the Lifshitz formulas for the free energy and force of an atom-surface interaction follow from the nonperturbative ones in the lowest order of the small parameter. Numerical computations of the free energy and force for the atoms of He{\\hspace{0pt}}\\ast and Na interacting with a surface of an Au plate have been performed using the frequency-dependent dielectric permittivity of Au and highly accurate dynamic atomic polarizabilities in the framework of both the nonperturbative and perturbative theories. According to our results, the maximum deviations between the two theories are reached at the shortest atom-surface separations of about 1 nm. Simple analytic expressions for the atom-surface free energy are derived in the classical limit and for an ideal-metal plane. In the lowest order of the small parameter, they are found in agreement with the perturbative ones following from the standard Lifshitz theory. Possible applications of the obtained results in the theory of van der Waals adsorption are discussed.

Atomic force microscopic study of the influence of physical stresses on Saccharomyces cerevisiae and Schizosaccharomyces pombe.

PubMed

Adya, Ashok K; Canetta, Elisabetta; Walker, Graeme M

2006-01-01

Morphological changes in the cell surfaces of the budding yeast Saccharomyces cerevisiae (strain NCYC 1681), and the fission yeast Schizosaccharomyces pombe (strain DVPB 1354), in response to thermal and osmotic stresses, were investigated using an atomic force microscope. With this microscope imaging, together with measurements of culture viability and cell size, it was possible to relate topological changes of the cell surface at nanoscale with cellular stress physiology. As expected, when the yeasts were exposed to thermostress or osmostress, their viability together with the mean cell volume decreased in conjunction with the increase in thermal or osmotic shock. Nevertheless, the viability of cells stressed for up to 1 h remained relatively high. For example, viabilities were >50% and >90% for the thermostressed, and >60% and >70% for the osmostressed S. cerevisiae and Schiz. pombe, respectively. Mean cell volume measurements, and bearing and roughness analyses of atomic force microscope images of stressed yeasts indicate that Schiz. pombe may be more resistant to physical stresses than S. cerevisiae. Overall, this study has highlighted the usefulness of atomic force microscope in studies of yeast stress physiology.

Harnessing the damping properties of materials for high-speed atomic force microscopy.

PubMed

Adams, Jonathan D; Erickson, Blake W; Grossenbacher, Jonas; Brugger, Juergen; Nievergelt, Adrian; Fantner, Georg E

2016-02-01

The success of high-speed atomic force microscopy in imaging molecular motors, enzymes and microbes in liquid environments suggests that the technique could be of significant value in a variety of areas of nanotechnology. However, the majority of atomic force microscopy experiments are performed in air, and the tapping-mode detection speed of current high-speed cantilevers is an order of magnitude lower in air than in liquids. Traditional approaches to increasing the imaging rate of atomic force microscopy have involved reducing the size of the cantilever, but further reductions in size will require a fundamental change in the detection method of the microscope. Here, we show that high-speed imaging in air can instead be achieved by changing the cantilever material. We use cantilevers fabricated from polymers, which can mimic the high damping environment of liquids. With this approach, SU-8 polymer cantilevers are developed that have an imaging-in-air detection bandwidth that is 19 times faster than those of conventional cantilevers of similar size, resonance frequency and spring constant.

Effectiveness of Modal Decomposition for Tapping Atomic Force Microscopy Microcantilevers in Liquid Environment.

PubMed

Kim, Il Kwang; Lee, Soo Il

2016-05-01

The modal decomposition of tapping mode atomic force microscopy microcantilevers in liquid environments was studied experimentally. Microcantilevers with different lengths and stiffnesses and two sample surfaces with different elastic moduli were used in the experiment. The response modes of the microcantilevers were extracted as proper orthogonal modes through proper orthogonal decomposition. Smooth orthogonal decomposition was used to estimate the resonance frequency directly. The effects of the tapping setpoint and the elastic modulus of the sample under test were examined in terms of their multi-mode responses with proper orthogonal modes, proper orthogonal values, smooth orthogonal modes and smooth orthogonal values. Regardless of the stiffness of the microcantilever under test, the first mode was dominant in tapping mode atomic force microscopy under normal operating conditions. However, at lower tapping setpoints, the flexible microcantilever showed modal distortion and noise near the tip when tapping on a hard sample. The stiff microcantilever had a higher mode effect on a soft sample at lower tapping setpoints. Modal decomposition for tapping mode atomic force microscopy can thus be used to estimate the characteristics of samples in liquid environments.

Quantification of surface displacements and electromechanical phenomena via dynamic atomic force microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balke, Nina; Jesse, Stephen; Yu, Pu

Detection of dynamic surface displacements associated with local changes in material strain provides access to a number of phenomena and material properties. Contact resonance-enhanced methods of atomic force microscopy (AFM) have been shown capable of detecting ~1–3 pm-level surface displacements, an approach used in techniques such as piezoresponse force microscopy, atomic force acoustic microscopy, and ultrasonic force microscopy. Here, based on an analytical model of AFM cantilever vibrations, we demonstrate a guideline to quantify surface displacements with high accuracy by taking into account the cantilever shape at the first resonant contact mode, depending on the tip–sample contact stiffness. The approachmore » has been experimentally verified and further developed for piezoresponse force microscopy (PFM) using well-defined ferroelectric materials. These results open up a way to accurate and precise measurements of surface displacement as well as piezoelectric constants at the pm-scale with nanometer spatial resolution and will allow avoiding erroneous data interpretations and measurement artifacts. Furthermore, this analysis is directly applicable to all cantilever-resonance-based scanning probe microscopy (SPM) techniques.« less

Sensing mode atomic force microscope

DOEpatents

Hough, Paul V. C.; Wang, Chengpu

2003-01-01

An atomic force microscope utilizes a pulse release system and improved method of operation to minimize contact forces between a probe tip affixed to a flexible cantilever and a specimen being measured. The pulse release system includes a magnetic particle affixed proximate the probe tip and an electromagnetic coil. When energized, the electromagnetic coil generates a magnetic field which applies a driving force on the magnetic particle sufficient to overcome adhesive forces exhibited between the probe tip and specimen. The atomic force microscope includes two independently displaceable piezo elements operable along a Z-axis. A controller drives the first Z-axis piezo element to provide a controlled approach between the probe tip and specimen up to a point of contact between the probe tip and specimen. The controller then drives the first Z-axis piezo element to withdraw the cantilever from the specimen. The controller also activates the pulse release system which drives the probe tip away from the specimen during withdrawal. Following withdrawal, the controller adjusts the height of the second Z-axis piezo element to maintain a substantially constant approach distance between successive samples.

Introduction of steered molecular dynamics into UNRES coarse-grained simulations package.

PubMed

Sieradzan, Adam K; Jakubowski, Rafał

2017-03-30

In this article, an implementation of steered molecular dynamics (SMD) in coarse-grain UNited RESidue (UNRES) simulations package is presented. Two variants of SMD have been implemented: with a constant force and a constant velocity. The huge advantage of SMD implementation in the UNRES force field is that it allows to pull with the speed significantly lower than the accessible pulling speed in simulations with all-atom representation of a system, with respect to a reasonable computational time. Therefore, obtaining pulling speed closer to those which appear in the atomic force spectroscopy is possible. The newly implemented method has been tested for behavior in a microcanonical run to verify the influence of introduction of artificial constrains on keeping total energy of the system. Moreover, as time dependent artificial force was introduced, the thermostat behavior was tested. The new method was also tested via unfolding of the Fn3 domain of human contactin 1 protein and the I27 titin domain. Obtained results were compared with Gø-like force field, all-atom force field, and experimental results. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Quantification of surface displacements and electromechanical phenomena via dynamic atomic force microscopy

DOE PAGES

Balke, Nina; Jesse, Stephen; Yu, Pu; ...

2016-09-15

Detection of dynamic surface displacements associated with local changes in material strain provides access to a number of phenomena and material properties. Contact resonance-enhanced methods of atomic force microscopy (AFM) have been shown capable of detecting ~1–3 pm-level surface displacements, an approach used in techniques such as piezoresponse force microscopy, atomic force acoustic microscopy, and ultrasonic force microscopy. Here, based on an analytical model of AFM cantilever vibrations, we demonstrate a guideline to quantify surface displacements with high accuracy by taking into account the cantilever shape at the first resonant contact mode, depending on the tip–sample contact stiffness. The approachmore » has been experimentally verified and further developed for piezoresponse force microscopy (PFM) using well-defined ferroelectric materials. These results open up a way to accurate and precise measurements of surface displacement as well as piezoelectric constants at the pm-scale with nanometer spatial resolution and will allow avoiding erroneous data interpretations and measurement artifacts. Furthermore, this analysis is directly applicable to all cantilever-resonance-based scanning probe microscopy (SPM) techniques.« less

Emergence of Huge Negative Spin-Transfer Torque in Atomically Thin Co layers

NASA Astrophysics Data System (ADS)

Je, Soong-Geun; Yoo, Sang-Cheol; Kim, Joo-Sung; Park, Yong-Keun; Park, Min-Ho; Moon, Joon; Min, Byoung-Chul; Choe, Sug-Bong

2017-04-01

Current-induced domain wall motion has drawn great attention in recent decades as the key operational principle of emerging magnetic memory devices. As the major driving force of the motion, the spin-orbit torque on chiral domain walls has been proposed and is currently extensively studied. However, we demonstrate here that there exists another driving force, which is larger than the spin-orbit torque in atomically thin Co films. Moreover, the direction of the present force is found to be the opposite of the prediction of the standard spin-transfer torque, resulting in the domain wall motion along the current direction. The symmetry of the force and its peculiar dependence on the domain wall structure suggest that the present force is, most likely, attributed to considerable enhancement of a negative nonadiabatic spin-transfer torque in ultranarrow domain walls. Careful measurements of the giant magnetoresistance manifest a negative spin polarization in the atomically thin Co films which might be responsible for the negative spin-transfer torque.

The Bichromatic Optical Force on the Atomic Life- time Scale

NASA Astrophysics Data System (ADS)

Corder, Christopher; Arnold, Brian; Metcalf, Harold

2013-05-01

Our experimental and theoretical studies of the bichromatic force (BF) have shown that its strength and velocity range are very much larger than those of the usual radiative force. Since the BF relies on stimulated effects, the role of spontaneous emission in laser cooling has come into question. We drive the 23 S -->33 P transition of He at λ = 389 nm with laser frequencies ωl =ωa +/- δ , where ωa is the atomic transition frequency and δ ~ 30 MHz. Thus the velocity range of the force is Δv ~ δ / 2 k = 6 m/s. Because of the large and nearly constant strength of the BF, F ~ ℏkδ / π , all atoms can reach the velocity limit in a time <= MΔv / F = π / 4ωr = 380 ns, where ωr is the atomic recoil frequency. In our experiment a beam of He atoms crosses perpendicular through the BF laser beams in 380 ns so the relatively long lifetime of the excited state (τ = 106 ns) allows one or at most two spontaneous emission events, despite Δv of many tens of recoils. We will present our initial measurements of the BF in this new domain. Supported by ONR and Dept. of Ed. GAANN.