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Sample records for nm diamond nanocrystals

  1. Surface Structure of Aerobically Oxidized Diamond Nanocrystals

    DTIC Science & Technology

    2014-10-27

    distribution is unlimited. Surface Structure of Aerobically Oxidized Diamond Nanocrystals The views, opinions and/or findings contained in this report...2211 diamond nanocrystals, REPORT DOCUMENTATION PAGE 11. SPONSOR/MONITOR’S REPORT NUMBER(S) 10. SPONSOR/MONITOR’S ACRONYM(S) ARO 8. PERFORMING...Room 254, Mail Code 8725 New York, NY 10027 -7922 ABSTRACT Surface Structure of Aerobically Oxidized Diamond Nanocrystals Report Title We investigate

  2. Surface Structure of Aerobically Oxidized Diamond Nanocrystals.

    PubMed

    Wolcott, Abraham; Schiros, Theanne; Trusheim, Matthew E; Chen, Edward H; Nordlund, Dennis; Diaz, Rosa E; Gaathon, Ophir; Englund, Dirk; Owen, Jonathan S

    2014-11-20

    We investigate the aerobic oxidation of high-pressure, high-temperature nanodiamonds (5-50 nm dimensions) using a combination of carbon and oxygen K-edge X-ray absorption, wavelength-dependent X-ray photoelectron, and vibrational spectroscopies. Oxidation at 575 °C for 2 h eliminates graphitic carbon contamination (>98%) and produces nanocrystals with hydroxyl functionalized surfaces as well as a minor component (<5%) of carboxylic anhydrides. The low graphitic carbon content and the high crystallinity of HPHT are evident from Raman spectra acquired using visible wavelength excitation (λexcit = 633 nm) as well as carbon K-edge X-ray absorption spectra where the signature of a core-hole exciton is observed. Both spectroscopic features are similar to those of chemical vapor deposited (CVD) diamond but differ significantly from the spectra of detonation nanodiamond. The importance of these findings to the functionalization of nanodiamond surfaces for biological labeling applications is discussed.

  3. Surface Structure of Aerobically Oxidized Diamond Nanocrystals

    PubMed Central

    2015-01-01

    We investigate the aerobic oxidation of high-pressure, high-temperature nanodiamonds (5–50 nm dimensions) using a combination of carbon and oxygen K-edge X-ray absorption, wavelength-dependent X-ray photoelectron, and vibrational spectroscopies. Oxidation at 575 °C for 2 h eliminates graphitic carbon contamination (>98%) and produces nanocrystals with hydroxyl functionalized surfaces as well as a minor component (<5%) of carboxylic anhydrides. The low graphitic carbon content and the high crystallinity of HPHT are evident from Raman spectra acquired using visible wavelength excitation (λexcit = 633 nm) as well as carbon K-edge X-ray absorption spectra where the signature of a core–hole exciton is observed. Both spectroscopic features are similar to those of chemical vapor deposited (CVD) diamond but differ significantly from the spectra of detonation nanodiamond. The importance of these findings to the functionalization of nanodiamond surfaces for biological labeling applications is discussed. PMID:25436035

  4. Surface Structure of Aerobically Oxidized Diamond Nanocrystals

    SciTech Connect

    Wolcott, Abraham; Schiros, Theanne; Trusheim, Matthew E.; Chen, Edward H.; Nordlund, Dennis; Diaz, Rosa E.; Gaaton, Ophir; Englund, Dirk; Owen, Jonathan S.

    2014-10-27

    Here we investigate the aerobic oxidation of high-pressure, high-temperature nanodiamonds (5–50 nm dimensions) using a combination of carbon and oxygen K-edge X-ray absorption, wavelength-dependent X-ray photoelectron, and vibrational spectroscopies. Oxidation at 575 °C for 2 h eliminates graphitic carbon contamination (>98%) and produces nanocrystals with hydroxyl functionalized surfaces as well as a minor component (<5%) of carboxylic anhydrides. The low graphitic carbon content and the high crystallinity of HPHT are evident from Raman spectra acquired using visible wavelength excitation (λexcit = 633 nm) as well as carbon K-edge X-ray absorption spectra where the signature of a core–hole exciton is observed. Both spectroscopic features are similar to those of chemical vapor deposited (CVD) diamond but differ significantly from the spectra of detonation nanodiamond. Lastly, we discuss the importance of these findings to the functionalization of nanodiamond surfaces for biological labeling applications.

  5. Surface Structure of Aerobically Oxidized Diamond Nanocrystals

    DOE PAGES

    Wolcott, Abraham; Schiros, Theanne; Trusheim, Matthew E.; ...

    2014-10-27

    Here we investigate the aerobic oxidation of high-pressure, high-temperature nanodiamonds (5–50 nm dimensions) using a combination of carbon and oxygen K-edge X-ray absorption, wavelength-dependent X-ray photoelectron, and vibrational spectroscopies. Oxidation at 575 °C for 2 h eliminates graphitic carbon contamination (>98%) and produces nanocrystals with hydroxyl functionalized surfaces as well as a minor component (<5%) of carboxylic anhydrides. The low graphitic carbon content and the high crystallinity of HPHT are evident from Raman spectra acquired using visible wavelength excitation (λexcit = 633 nm) as well as carbon K-edge X-ray absorption spectra where the signature of a core–hole exciton is observed.more » Both spectroscopic features are similar to those of chemical vapor deposited (CVD) diamond but differ significantly from the spectra of detonation nanodiamond. Lastly, we discuss the importance of these findings to the functionalization of nanodiamond surfaces for biological labeling applications.« less

  6. Implantation conditions for diamond nanocrystal formation in amorphous silica

    SciTech Connect

    Buljan, Maja; Radovic, Iva Bogdanovic; Desnica, Uros V.; Ivanda, Mile; Jaksic, Milko; Saguy, Cecile; Kalish, Rafi; Djerdj, Igor; Tonejc, Andelka; Gamulin, Ozren

    2008-08-01

    We present a study of carbon ion implantation in amorphous silica, which, followed by annealing in a hydrogen-rich environment, leads to preferential formation of carbon nanocrystals with cubic diamond (c-diamond), face-centered cubic (n-diamond), or simple cubic (i-carbon) carbon crystal lattices. Two different annealing treatments were used: furnace annealing for 1 h and rapid thermal annealing for a brief period, which enables monitoring of early nucleation events. The influence of implanted dose and annealing type on carbon and hydrogen concentrations, clustering, and bonding were investigated. Rutherford backscattering, elastic recoil detection analysis, infrared spectroscopy, transmission electron microscopy, selected area electron diffraction, ultraviolet-visible absorption measurements, and Raman spectroscopy were used to study these carbon formations. These results, combined with the results of previous investigations on similar systems, show that preferential formation of different carbon phases (diamond, n-diamond, or i-carbon) depends on implantation energy, implantation dose, and annealing conditions. Diamond nanocrystals formed at a relatively low carbon volume density are achieved by deeper implantation and/or lower implanted dose. Higher volume densities led to n-diamond and finally to i-carbon crystal formation. This observed behavior is related to damage sites induced by implantation. The optical properties of different carbon nanocrystal phases were significantly different.

  7. Diamond nanocrystals hosting single nitrogen-vacancy color centers sorted by photon-correlation near-field microscopy.

    PubMed

    Sonnefraud, Yannick; Cuche, Aurélien; Faklaris, Orestis; Boudou, Jean-Paul; Sauvage, Thierry; Roch, Jean-François; Treussart, François; Huant, Serge

    2008-03-15

    Diamond nanocrystals containing highly photoluminescent color centers are attractive, nonclassical, and near-field light sources. For near-field applications, the size of the nanocrystal is crucial, since it defines the optical resolution. Nitrogen-vacancy (NV) color centers are efficiently created by proton irradiation and annealing of a nanodiamond powder. Using near-field microscopy and photon statistics measurements, we show that nanodiamonds with sizes down to 25 nm can hold a single NV color center with bright and stable photoluminescence.

  8. Scalable fabrication of high purity diamond nanocrystals with long-spin-coherence nitrogen vacancy centers.

    PubMed

    Trusheim, Matthew E; Li, Luozhou; Laraoui, Abdelghani; Chen, Edward H; Bakhru, Hassaram; Schröder, Tim; Gaathon, Ophir; Meriles, Carlos A; Englund, Dirk

    2014-01-08

    The combination of long spin coherence time and nanoscale size has made nitrogen vacancy (NV) centers in nanodiamonds the subject of much interest for quantum information and sensing applications. However, currently available high-pressure high-temperature (HPHT) nanodiamonds have a high concentration of paramagnetic impurities that limit their spin coherence time to the order of microseconds, less than 1% of that observed in bulk diamond. In this work, we use a porous metal mask and a reactive ion etching process to fabricate nanocrystals from high-purity chemical vapor deposition (CVD) diamond. We show that NV centers in these CVD nanodiamonds exhibit record-long spin coherence times in excess of 200 μs, enabling magnetic field sensitivities of 290 nT Hz(-1/2) with the spatial resolution characteristic of a 50 nm diameter probe.

  9. Suppression of fluorescence phonon sideband from nitrogen vacancy centers in diamond nanocrystals by substrate effect.

    PubMed

    Zhao, Hong-Quan; Fujiwara, Masazumi; Takeuchi, Shigeki

    2012-07-02

    Substrates effect is observed on the suppression of the phonon sideband from nitrogen vacancy (NV) centers in 50nm diamond nanocrystals at cryogenic temperatures. As a quantitative parameter of the population of phonon sidebands, the Debye-Waller factor is estimated from fluorescence spectra on glass, silicon, and silica-on-silicon substrates. Fluorescence spectra of negatively charged NV centers in nanodiamonds on silica-on-silicon substrates have average and maximum Debye-Waller factors of 12.7% (which is about six times greater than that of samples on glass substrates) and 19.3%, respectively. This effect is expected to be very important for future applications of NV centers in quantum information science and nanosensing.

  10. The hemocompatibility of oxidized diamond nanocrystals for biomedical applications

    NASA Astrophysics Data System (ADS)

    Li, Hung-Cheng; Hsieh, Feng-Jen; Chen, Ching-Pin; Chang, Ming-Yao; Hsieh, Patrick C. H.; Chen, Chia-Chun; Hung, Shain-Un; Wu, Che-Chih; Chang, Huan-Cheng

    2013-10-01

    Low-dimensional carbon-based nanomaterials have recently received enormous attention for biomedical applications. However, increasing evidence indicates that they are cytotoxic and can cause inflammatory responses in the body. Here, we show that monocrystalline nanodiamonds (NDs) synthesized by high-pressure-high-temperature (HPHT) methods and purified by air oxidation and strong oxidative acid treatments have excellent hemocompatibility with negligible hemolytic and thrombogenic activities. Cell viability assays with human primary endothelial cells suggested that the oxidized HPHT-NDs (dimensions of 35-500 nm) are non-cytotoxic. No significant elevation of the inflammatory cytokine levels of IL-1β and IL-6 was detected in mice after intravenous injection of the nanocrystals in vivo. Using a hindlimb-ischemia mouse model, we demonstrated that 35-nm NDs after covalent conjugation with polyarginine are useful as a drug delivery vehicle of heparin for prolonged anticoagulation treatment. The present study lays a solid foundation for further therapeutic applications of NDs in biomedicine.

  11. The hemocompatibility of oxidized diamond nanocrystals for biomedical applications.

    PubMed

    Li, Hung-Cheng; Hsieh, Feng-Jen; Chen, Ching-Pin; Chang, Ming-Yao; Hsieh, Patrick C H; Chen, Chia-Chun; Hung, Shain-Un; Wu, Che-Chih; Chang, Huan-Cheng

    2013-10-25

    Low-dimensional carbon-based nanomaterials have recently received enormous attention for biomedical applications. However, increasing evidence indicates that they are cytotoxic and can cause inflammatory responses in the body. Here, we show that monocrystalline nanodiamonds (NDs) synthesized by high-pressure-high-temperature (HPHT) methods and purified by air oxidation and strong oxidative acid treatments have excellent hemocompatibility with negligible hemolytic and thrombogenic activities. Cell viability assays with human primary endothelial cells suggested that the oxidized HPHT-NDs (dimensions of 35-500 nm) are non-cytotoxic. No significant elevation of the inflammatory cytokine levels of IL-1β and IL-6 was detected in mice after intravenous injection of the nanocrystals in vivo. Using a hindlimb-ischemia mouse model, we demonstrated that 35-nm NDs after covalent conjugation with polyarginine are useful as a drug delivery vehicle of heparin for prolonged anticoagulation treatment. The present study lays a solid foundation for further therapeutic applications of NDs in biomedicine.

  12. Loading an Optical Trap with Diamond Nanocrystals Containing Nitrogen-Vacancy Centers from a Surface

    NASA Astrophysics Data System (ADS)

    Hsu, Jen-Feng; Ji, Peng; Dutt, M. V. Gurudev; D'Urso, Brian R.

    2015-03-01

    We present a simple and effective method of loading particles into an optical trap. Our primary application of this method is loading photoluminescent material, such as diamond nanocrystals containing nitrogen-vacancy (NV) centers, for coupling the mechanical motion of the trapped crystal with the spin of the NV centers. Highly absorptive material at the trapping laser frequency, such as tartrazine dye, is used as media to attach nanodiamonds and burn into a cloud of air-borne particles as the material is swept near the trapping laser focus on a glass slide. Particles are then trapped with the laser used for burning or transferred to a second laser trap at a different wavelength. Evidence of successful loading diamond nanocrystals into the trap presented includes high sensitivity of the photoluminecscence (PL) to the excitation laser and the PL spectra of the optically trapped particles

  13. Rapid Synthesis of Sub-5 nm Sized Cubic Boron Nitride Nanocrystals with High-Piezoelectric Behavior via Electrochemical Shock.

    PubMed

    Chen, Zhigang; Li, Lianhui; Cong, Shan; Xuan, Jinnan; Zhang, Dengsong; Geng, Fengxia; Zhang, Ting; Zhao, Zhigang

    2017-01-11

    A key challenge in current superhard materials research is the design of novel superhard nanocrystals (NCs) whereby new and unexpected properties may be predicted. Cubic boron nitride (c-BN) is a superhard material which ranks next to diamond; however, downsizing c-BN material below the 10 nm scale is rather challenging, and the interesting new properties of c-BN NCs remain unexplored and wide open. Herein we report an electrochemical shock method to prepare uniform c-BN NCs with a lateral size of only 3.4 ± 0.6 nm and a thickness of only 0.74 ± 0.3 nm at ambient temperature and pressure. The fabrication process is simple and fast, with c-BN NCs produced in just a few minutes. Most interestingly, the NCs exhibit excellent piezoelectric performance with a large recordable piezoelectric coefficient of 25.7 pC/N, which is almost 6 times larger than that from bulk c-BN and even competitive to conventional piezoelectric materials. The phenomenon of enhancement in the piezoelectric properties of BN NCs might arise from the nanoscale surface effect and nanoscale shape effect of BN NCs. This work paves an interesting route for exploring new properties of superhard NCs.

  14. Cooling the motion of diamond nanocrystals in a magneto-gravitational trap in high vacuum

    SciTech Connect

    Hsu, Jen -Feng; Ji, Peng; Lewandowski, Charles W.; D’Urso, Brian

    2016-07-22

    Levitated diamond nanocrystals with nitrogen-vacancy (NV) centres in high vacuum have been proposed as a unique system for experiments in fundamental quantum mechanics, including the generation of large quantum superposition states and tests of quantum gravity. This system promises extreme isolation from its environment while providing quantum control and sensing through the NV centre spin. While optical trapping has been the most explored method of levitation, recent results indicate that excessive optical heating of the nanodiamonds under vacuum may make the method impractical with currently available materials. Here, we study an alternative magneto-gravitational trap for diamagnetic particles, such as diamond nanocrystals, with stable levitation from atmospheric pressure to high vacuum. Magnetic field gradients from permanent magnets confine the particle in two dimensions, while confinement in the third dimension is gravitational. Furthermore, we demonstrate that feedback cooling of the centre-of-mass motion of a trapped nanodiamond cluster results in cooling of one degree of freedom to less than 1 K.

  15. Cooling the Motion of Diamond Nanocrystals in a Magneto-Gravitational Trap in High Vacuum

    PubMed Central

    Hsu, Jen-Feng; Ji, Peng; Lewandowski, Charles W.; D’Urso, Brian

    2016-01-01

    Levitated diamond nanocrystals with nitrogen-vacancy (NV) centres in high vacuum have been proposed as a unique system for experiments in fundamental quantum mechanics, including the generation of large quantum superposition states and tests of quantum gravity. This system promises extreme isolation from its environment while providing quantum control and sensing through the NV centre spin. While optical trapping has been the most explored method of levitation, recent results indicate that excessive optical heating of the nanodiamonds under vacuum may make the method impractical with currently available materials. Here, we study an alternative magneto-gravitational trap for diamagnetic particles, such as diamond nanocrystals, with stable levitation from atmospheric pressure to high vacuum. Magnetic field gradients from permanent magnets confine the particle in two dimensions, while confinement in the third dimension is gravitational. We demonstrate that feedback cooling of the centre-of-mass motion of a trapped nanodiamond cluster results in cooling of one degree of freedom to less than 1 K. PMID:27444654

  16. Simulation of ultraviolet- and soft X-ray-pulse generation as a result of cooperative recombination of excitons in diamond nanocrystals embedded in a polymer film

    SciTech Connect

    Kukushkin, V. A.

    2013-11-15

    Using numerical simulation, it is shown that the recombination of free excitons photoexcited in diamond nanocrystals embedded in a polymer film can occur in the cooperative mode. It is found that this mode can be implemented despite the fact that diamond is an 'indirect' semiconductor. It is shown that the power of the generated radiation at the pulse peak during the cooperative recombination of free excitons can exceed that of the incoherent spontaneous emission of the same initial number of free excitons by more than an order of magnitude. Finally, it is shown that the process under consideration can be used to generate picosecond pulses of ultraviolet and soft X-ray electromagnetic field at a wavelength of 235 nm.

  17. Cooling the motion of diamond nanocrystals in a magneto-gravitational trap in high vacuum

    DOE PAGES

    Hsu, Jen -Feng; Ji, Peng; Lewandowski, Charles W.; ...

    2016-07-22

    Levitated diamond nanocrystals with nitrogen-vacancy (NV) centres in high vacuum have been proposed as a unique system for experiments in fundamental quantum mechanics, including the generation of large quantum superposition states and tests of quantum gravity. This system promises extreme isolation from its environment while providing quantum control and sensing through the NV centre spin. While optical trapping has been the most explored method of levitation, recent results indicate that excessive optical heating of the nanodiamonds under vacuum may make the method impractical with currently available materials. Here, we study an alternative magneto-gravitational trap for diamagnetic particles, such as diamondmore » nanocrystals, with stable levitation from atmospheric pressure to high vacuum. Magnetic field gradients from permanent magnets confine the particle in two dimensions, while confinement in the third dimension is gravitational. Furthermore, we demonstrate that feedback cooling of the centre-of-mass motion of a trapped nanodiamond cluster results in cooling of one degree of freedom to less than 1 K.« less

  18. Partially Oxidized Sub-10 nm MnO Nanocrystals with High Activity for Water Oxidation Catalysis

    PubMed Central

    Jin, Kyoungsuk; Chu, Arim; Park, Jimin; Jeong, Donghyuk; Jerng, Sung Eun; Sim, Uk; Jeong, Hui-Yun; Lee, Chan Woo; Park, Yong-Sun; Yang, Ki Dong; Kumar Pradhan, Gajendra; Kim, Donghun; Sung, Nark-Eon; Hee Kim, Sun; Nam, Ki Tae

    2015-01-01

    The oxygen evolution reaction (OER) is considered a major bottleneck in the overall water electrolysis process. In this work, highly active manganese oxide nano-catalysts were synthesized via hot injection. Facile surface treatment generated Mn(III) species on monodisperse 10 nm MnO nanocrystals (NCs). Size dependency of MnO NCs on OER activity was also investigated. Surprisingly, the partially oxidized MnO NCs only required 530 mV @ 5 mA cm−2 under near neutral conditions. PMID:25998696

  19. Highly efficient picosecond diamond Raman laser at 1240 and 1485 nm.

    PubMed

    Warrier, Aravindan M; Lin, Jipeng; Pask, Helen M; Mildren, Richard P; Coutts, David W; Spence, David J

    2014-02-10

    We present a highly efficient picosecond diamond Raman laser synchronously-pumped by a 4.8 W mode-locked laser at 1064 nm. A ring cavity was adopted for efficient operation. With a low-Q cavity for first-Stokes 1240 nm, we have achieved 2.75 W output power at 1240 nm with 59% overall conversion efficiency. The slope efficiency tended towards 76% far above the SRS threshold, approaching the SRS quantum limit for diamond. A high-Q first-Stokes cavity was employed for second-Stokes 1485 nm generation through the combined processes of four-wave mixing and single-pass stimulated Raman scattering. Up to 1.0 W of second-stokes at 1485 nm was obtained, corresponding to 21% overall conversion efficiency. The minimum output pulse duration was compressed relative to the 15 ps pump, producing pulses as short as 9 ps for 1240 nm and 6 ps for 1485 nm respectively.

  20. Nanocrystal structures

    DOEpatents

    Eisler, Hans J.; Sundar, Vikram C.; Walsh, Michael E.; Klimov, Victor I.; Bawendi, Moungi G.; Smith, Henry I.

    2006-12-19

    A structure including a grating and a semiconductor nanocrystal layer on the grating, can be a laser. The semiconductor nanocrystal layer can include a plurality of semiconductor nanocrystals including a Group II–VI compound, the nanocrystals being distributed in a metal oxide matrix. The grating can have a periodicity from 200 nm to 500 nm.

  1. Three-dimensional controlled growth of monodisperse sub-50 nm heterogeneous nanocrystals

    PubMed Central

    Liu, Deming; Xu, Xiaoxue; Du, Yi; Qin, Xian; Zhang, Yuhai; Ma, Chenshuo; Wen, Shihui; Ren, Wei; Goldys, Ewa M.; Piper, James A.; Dou, Shixue; Liu, Xiaogang; Jin, Dayong

    2016-01-01

    The ultimate frontier in nanomaterials engineering is to realize their composition control with atomic scale precision to enable fabrication of nanoparticles with desirable size, shape and surface properties. Such control becomes even more useful when growing hybrid nanocrystals designed to integrate multiple functionalities. Here we report achieving such degree of control in a family of rare-earth-doped nanomaterials. We experimentally verify the co-existence and different roles of oleate anions (OA−) and molecules (OAH) in the crystal formation. We identify that the control over the ratio of OA− to OAH can be used to directionally inhibit, promote or etch the crystallographic facets of the nanoparticles. This control enables selective grafting of shells with complex morphologies grown over nanocrystal cores, thus allowing the fabrication of a diverse library of monodisperse sub-50 nm nanoparticles. With such programmable additive and subtractive engineering a variety of three-dimensional shapes can be implemented using a bottom–up scalable approach. PMID:26743184

  2. Coupling of a single diamond nanocrystal to a whispering-gallery microcavity: Photon transport benefitting from Rayleigh scattering

    SciTech Connect

    Liu Yongchun; Xiao Yunfeng; Li Beibei; Jiang Xuefeng; Li Yan; Gong Qihuang

    2011-07-15

    We study the Rayleigh scattering induced by a diamond nanocrystal in a whispering-gallery-microcavity-waveguide coupling system and find that it plays a significant role in the photon transportation. On the one hand, this study provides insight into future solid-state cavity quantum electrodynamics aimed at understanding strong-coupling physics. On the other hand, benefitting from this Rayleigh scattering, effects such as dipole-induced transparency and strong photon antibunching can occur simultaneously. As a potential application, this system can function as a high-efficiency photon turnstile. In contrast to B. Dayan et al. [Science 319, 1062 (2008)], the photon turnstiles proposed here are almost immune to the nanocrystal's azimuthal position.

  3. Single-particle mass spectrometry of polystyrene microspheres and diamond nanocrystals.

    PubMed

    Cai, Y; Peng, W P; Kuo, S J; Lee, Y T; Chang, H C

    2002-01-01

    High-resolution mass spectra of single submicrometer-sized particles are obtained using an electrospray ionization source in combination with an audio frequency quadrupole ion-trap mass spectrometer. Distinct from conventional methods, light scattering from a continuous Ar-ion laser is detected for particles ejected out of the ion trap. Typically, 10 particles are being trapped and interrogated in each measurement. With the audio frequency ion trap operated in a mass-selective instability mode, analysis of the particles reveals that they all differ in mass-to-charge ratio (m/z), and the individual peak in the observed mass spectrum is essentially derived from one single particle. A histogram of the spectra acquired in 10(2) repetitions of the experiment is equivalent to the single spectrum that would be observed when an ion ensemble of 10(3) particles is analyzed simultaneously using the single-particle mass spectrometer (SPMS). To calibrate such single-particle mass spectra, secular frequencies of the oscillatory motions of the individual particle within the trap are measured, and the trap parameter qz at the point of ejection is determined. A mass resolution exceeding 10(4) can readily be achieved in the absence of ion ensemble effect. We demonstrate in this work that the SPMS not only allows investigations of monodisperse polystyrene microspheres, but also is capable of detecting diamond nanoparticles with a nominal diameter of 100 nm, as well.

  4. Coupling of a single diamond nanocrystal to a whispering-gallery microcavity: Photon transport benefitting from Rayleigh scattering

    NASA Astrophysics Data System (ADS)

    Liu, Yong-Chun; Xiao, Yun-Feng; Li, Bei-Bei; Jiang, Xue-Feng; Li, Yan; Gong, Qihuang

    2011-07-01

    We study the Rayleigh scattering induced by a diamond nanocrystal in a whispering-gallery-microcavity-waveguide coupling system and find that it plays a significant role in the photon transportation. On the one hand, this study provides insight into future solid-state cavity quantum electrodynamics aimed at understanding strong-coupling physics. On the other hand, benefitting from this Rayleigh scattering, effects such as dipole-induced transparency and strong photon antibunching can occur simultaneously. As a potential application, this system can function as a high-efficiency photon turnstile. In contrast to B. Dayan [ScienceSCIEAS0036-807510.1126/science.1152261 319, 1062 (2008)], the photon turnstiles proposed here are almost immune to the nanocrystal’s azimuthal position.

  5. External-cavity diamond Raman laser performance at 1240 nm and 1485 nm wavelengths with high pulse energy

    NASA Astrophysics Data System (ADS)

    Pashinin, V. P.; Ralchenko, V. G.; Bolshakov, A. P.; Ashkinazi, E. E.; Gorbashova, M. A.; Yurov, V. Yu; Konov, V. I.

    2016-06-01

    We report on an external-cavity diamond Raman laser (DRL) pumped with a Q-switched Nd:YAG and generating at 1st and 2nd Stokes (1240 nm and 1485 nm) with enhanced output energy. The slope efficiency of 54% and output energy as high as 1.2 mJ in single pulse at 1240 nm have been achieved with optimized cavity, while the pulse energy of 0.70 mJ was obtained in the eye-safe spectral region at 1485 nm. Calculations of thermal lensing effect indicate it as a possible reason for the observed decrease in conversion efficiency at the highest pump energies.

  6. Seedless Polyol Synthesis and CO Oxidation Activity of Monodisperse (111) and (100)-Oriented Rhodium Nanocrystals in Sub-10 nm Sizes

    SciTech Connect

    Zhang, Yawen; Grass, Michael E.; Huang, Wenyu; Somorjai, Gabor A.

    2010-03-15

    Monodisperse sub-10 nm (6.5 nm) sized Rh nanocrystals with (111) and (100) surface structures were synthesized by a seedless polyol reduction in ethylene glycol, with poly(vinylpyrrolidone) as a capping ligand. When using [Rh(Ac){sub 2}]{sub 2} as the metal precursor, (111)-oriented Rh nanopolyhedra containing 76% (111)-twined hexagons (in 2D projection) were obtained; whereas, when employing RhCl{sub 3} as the metal precursor in the presence of alkylammonium bromide, such as tetramethylammonium bromide and trimethyl(tetradecyl)ammonium bromide, (100)-oriented Rh nanocubes were obtained with 85% selectivity. The {l_brace}100{r_brace} faces of the Rh nanocrystals are stabilized by chemically adsorbed Br{sup -} ions from alkylammonium bromides, which led to (100)-oriented nanocubes. Monolayer films of the (111)-oriented Rh nanopolyhedra and (100)-oriented Rh nanocubes were deposited on silicon wafers in a Langmuir-Blodgett trough to make model 2D nanoarray catalysts. These nanocatalysts were active for CO oxidation by O{sub 2}, and the turnover frequency was independent of nanoparticle shape, consistent with that previously observed for Rh(111) and Rh(100) single crystals.

  7. Sub-10 nm Platinum Nanocrystals with Size and Shape Control: Catalytic Study for Ethylene and Pyrrole Hydrogenation

    SciTech Connect

    Tsung, Chia-Kuang; Kuhn, John N.; Huang, Wenyu; Aliaga, Cesar; Hung, Ling-I; Somorjai, Gabor A.; Yang, Peidong

    2009-03-02

    Platinum nanocubes and nanopolyhedra with tunable size from 5 to 9 nm were synthesized by controlling the reducing rate of metal precursor ions in a one-pot polyol synthesis. A two-stage process is proposed for the simultaneous control of size and shape. In the first stage, the oxidation state of the metal ion precursors determined the nucleation rate and consequently the number of nuclei. The reaction temperature controlled the shape in the second stage by regulation of the growth kinetics. These well-defined nanocrystals were loaded into MCF-17 mesoporous silica for examination of catalytic properties. Pt loadings and dispersions of the supported catalysts were determined by elemental analysis (ICP-MS) and H2 chemisorption isotherms, respectively. Ethylene hydrogenation rates over the Pt nanocrystals were independent of both size and shape and comparable to Pt single crystals. For pyrrole hydrogenation, the nanocubes enhanced ring-opening ability and thus showed a higher selectivity to n-butylamine as compared to nanopolyhedra.

  8. Sub-6 nm monodisperse hexagonal core/shell NaGdF4 nanocrystals with enhanced upconversion photoluminescence.

    PubMed

    Liu, Jing; Chen, Guanying; Hao, Shuwei; Yang, Chunhui

    2017-01-07

    The ability to fabricate lanthanide-doped upconversion nanocrystals (UCNCs) with tailored size and emission profile has fuelled their uses in a broad spectrum of biological applications. Yet, limited success has been met in the preparation of sub-6 nm UCNCs with efficient upconversion photoluminescence (UCPL), which enable high contrast optical bioimaging with minimized adverse biological effects entailed by size-induced rapid clearance from the body. Here, we present a simple and reproducible approach to synthesize a set of monodispersed hexagonal-phase core NaGdF4:Yb/Ln (Ln = Er, Ho, Tm) of ∼3-4 nm and core/shell NaGdF4:Yb/Ln@NaGdF4 (Ln = Er, Ho, Tm) UCNCs of ∼5-6 nm. We show that the core/shell UCNCs can be up to ∼1000 times more efficient than the corresponding core UCNCs due to the effective suppression of surface-related quenching effects for the core. The observation of prolonged PL lifetime for the core/shell than that for the core UCNCs demonstrates the role of the inert shell layer for the protection of the core. The achievement of sub-6 nm NaGdF4 UCNCs with significantly improved luminescence efficiency constitutes a solid step towards high contrast UCPL optical imaging with secured biological safety.

  9. Photonic Modulation Using Bi-Directional Diamond Shaped Ring Lasers at 1550 NM

    DTIC Science & Technology

    2007-04-01

    Infotonics Technology Center worked collaboratively to characterize and eventually package diode-based, diamond-shaped cavity, ring lasers that operate at...laser modes provide a direct means for realizing the Sagnac effect, which has been well established in gyro technology with gas and fiber lasers...Injection Wavelength Investigation……………………………………...15 4.1.2 Injection Frequency Investigation……………………………………….19 4.1.3 Gain Quenching Investigations

  10. Method to grow carbon thin films consisting entirely of diamond grains 3-5 nm in size and high-energy grain boundaries

    DOEpatents

    Carlisle, John A.; Auciello, Orlando; Birrell, James

    2006-10-31

    An ultrananocrystalline diamond (UNCD) having an average grain size between 3 and 5 nanometers (nm) with not more than about 8% by volume diamond having an average grain size larger than 10 nm. A method of manufacturing UNCD film is also disclosed in which a vapor of acetylene and hydrogen in an inert gas other than He wherein the volume ratio of acetylene to hydrogen is greater than 0.35 and less than 0.85, with the balance being an inert gas, is subjected to a suitable amount of energy to fragment at least some of the acetylene to form a UNCD film having an average grain size of 3 to 5 nm with not more than about 8% by volume diamond having an average grain size larger than 10 nm.

  11. Stimulated emission depletion microscopy resolves individual nitrogen vacancy centers in diamond nanocrystals.

    PubMed

    Arroyo-Camejo, Silvia; Adam, Marie-Pierre; Besbes, Mondher; Hugonin, Jean-Paul; Jacques, Vincent; Greffet, Jean-Jacques; Roch, Jean-François; Hell, Stefan W; Treussart, François

    2013-12-23

    Nitrogen-vacancy (NV) color centers in nanodiamonds are highly promising for bioimaging and sensing. However, resolving individual NV centers within nanodiamond particles and the controlled addressing and readout of their spin state has remained a major challenge. Spatially stochastic super-resolution techniques cannot provide this capability in principle, whereas coordinate-controlled super-resolution imaging methods, like stimulated emission depletion (STED) microscopy, have been predicted to fail in nanodiamonds. Here we show that, contrary to these predictions, STED can resolve single NV centers in 40-250 nm sized nanodiamonds with a resolution of ≈10 nm. Even multiple adjacent NVs located in single nanodiamonds can be imaged individually down to relative distances of ≈15 nm. Far-field optical super-resolution of NVs inside nanodiamonds is highly relevant for bioimaging applications of these fluorescent nanolabels. The targeted addressing and readout of individual NV(-) spins inside nanodiamonds by STED should also be of high significance for quantum sensing and information applications.

  12. Structure and microbial synthesis of sub-10 nm Bi2O3 nanocrystals.

    PubMed

    Uddin, Imran; Adyanthaya, Suguna; Syed, Asad; Selvaraj, K; Ahmad, Absar; Poddar, Pankaj

    2008-08-01

    After the advent of novel chemical and microbial techniques, providing control over grain size and shape of the nanomaterials, several binary-oxide materials have been explored in size less than 10 nm for their tunable physical properties. Bi2O3 nanoparticles have also redrawn attention due to their excellent properties, mostly as optoelectronic material. Here, we report the room-temperature biosynthesis of Bi2O3 nanoparticles in a size range of 5-8 nm by extra-cellularly challenging the plant pathogenic fungus--Fusarium oxysporum with the bismuth nitrate as precursor. The as-synthesized particle-surfaces are inherently functionalized by a robust layer of proteins which provides them very good stability in the aqueous medium. Structural investigation using selected area electron diffraction, high resolution transmission electron microscopy and powder XRD shows that particles are almost perfectly single crystalline and primarily crystallize in alpha-phase with monoclinic structure.

  13. Sub-10 nm lanthanide doped BaLuF{sub 5} nanocrystals: Shape controllable synthesis, tunable multicolor emission and enhanced near-infrared upconversion luminescence

    SciTech Connect

    Rao, Ling; Lu, Wei; Wang, Haibo; Yi, Zhigao; Zeng, Songjun; Li, Zheng

    2015-04-15

    Highlights: • Sub-10 nm cubic phase BaLuF{sub 5} nanocrystals were synthesized by a hydrothermal method for the first time. • Tunable multicolor from yellow to yellow-green was achieved by controlling Gd{sup 3+} content in BaLuF{sub 5}:Yb/Er system. • Intense near-infrared upconversion luminescence in BaLuF{sub 5}:Gd/Yb/Tm nanocrystal. • The enhancement near-infrared luminescence can be realized by adjusting the content of Gd{sup 3+} in BaLuF{sub 5}:Gd/Yb/Tm system. - Abstract: In this study, sub-10 nm BaLuF{sub 5} nanocrystals with cubic phase structure were synthesized by a solvothermal method using oleic acid as the stabilizing agent. The as-prepared BaLuF{sub 5} nanocrystals were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and analyzed by the upconversion (UC) spectra. The TEM results reveal that these samples present high uniformity. Compared with Gd-free samples, the size of BaLuF{sub 5}:Yb/Er doped with 10% Gd{sup 3+} decreased to 5.6 nm. In addition, BaLuF{sub 5}:Yb/Tm/Gd upconversion nanoparticles (UCNPs) presented efficient near-infrared (NIR)-NIR UC luminescence. Therefore, it is expected that these ultra-small BaLuF{sub 5} nanocrystals with well-controlled shape, size, and UC emission have potential applications in biomedical imaging fields.

  14. Sensitivity of Raman spectra excited at 325 nm to surface treatments of undoped polycrystalline diamond films

    NASA Astrophysics Data System (ADS)

    Ghodbane, S.; Deneuville, A.; Tromson, D.; Bergonzo, P.; Bustarret, E.; Ballutaud, D.

    2006-08-01

    About 20 m thick films were deposited in the same run by MPCVD at 900 °C on Si substrates and then hydrogenated in situ during 30 min with a hydrogen plasma at the same temperature. Their surfaces were kept as prepared or more or less strongly oxidized by annealing at 600 °C under ambient atmosphere or by sulphochromic acid or aqua regia treatments. Raman spectra were excited at 325 and 632.8 nm. Spectra of the as-prepared sample exhibit structures around 2835 and 2895 cm-1 from monohydride carbon-hydrogen ascribed to the atomically flat (111) and (100) areas, respectively, on the facets of the sample surface crystallites. The decrease of these structures in the normalized spectra after the various oxidation treatments confirms these assignments. The decrease is smaller for the aqua regia treatment than for the two other treatments which give similar effects. Other Raman signals from sp2 C around 1589 cm-1 and CHx bonds around 2930, 2952, 3025 and 3050 cm-1 originate from species at the surface and within the films. Their variation with the oxidizing treatments indicates a significant contribution from the surface species.

  15. Highly stable sub-5 nm Sn₆O₄(OH)₄ nanocrystals with ultrahigh activity as advanced photocatalytic materials for photodegradation of methyl orange.

    PubMed

    Xiao, J; Wu, Q L; Liu, P; Liang, Y; Li, H B; Wu, M M; Yang, G W

    2014-04-04

    Among numerous active photocatalytic materials, Sn-based oxide nanomaterials are promising photocatalytic materials in environmental protection measures such as water remediation due to their excellent physicochemical property. Research on photocatalytic nanomaterials for photodegradation of methyl orange (MO) so far has focused on TiO₂-based nanostructures; e.g., TiO₂-P25 is recognized to be the best commercial photocatalyst to date, rather than Sn-based oxide nanomaterials, in spite of their impressive acid- and alkali-resistant properties and high stability. Here, we demonstrate very high photocatalytic activity of highly stable sub-5 nm hydromarchite (Sn₆O₄(OH)₄) nanocrystals synthesized by a simple and environmentally friendly laser-based technique. These Sn₆O₄(OH)₄ nanocrystals exhibit ultrahigh photocatalytic performance for photodegradation of MO and their degradation efficiency is far superior to that of TiO₂-P25. The detailed investigations demonstrated that the great photocatalytic activity results from the ultrafine size and unique surface activity induced by the laser-based technique. Mass production of reactive species of hydroxyl radicals was detected in the experiments due to the appropriate bandgap of Sn₆O₄(OH)₄ nanocrystals. These findings actually open a door to applications of Sn-based oxide nanomaterials as advanced photocatalytic materials.

  16. A conversion model of graphite to ultrananocrystalline diamond via laser processing at ambient temperature and normal pressure

    SciTech Connect

    Ren, X. D. Yang, H. M.; Zheng, L. M.; Tang, S. X.; Ren, N. F.; Xu, S. D.; Yuan, S. Q.

    2014-07-14

    The synthesis mechanism of ultrananocrystalline diamond via laser shock processing of graphite suspension was presented at room temperature and normal pressure, which yielded the ultrananocrystalline diamond in size of about 5 nm. X-ray diffraction, high-resolution transmission electron microscopy, and laser Raman spectroscopy were used to characterize the nano-crystals. The transformation model and growth restriction mechanism of high power density with short-pulsed laser shocking of graphite particles in liquid was put forward.

  17. Structural Order in Ultrathin Films of the Monolayer Protected Clusters Based Upon 4-nm Gold Nanocrystals: An Experimental and Theoretical Study

    PubMed Central

    Bhattarai, Nabraj; Khanal, Subarna; Bahena, Daniel; Olmos-Asar, Jimena A.; Ponce, Arturo; Whetten, Robert L.; Mariscal, Marcelo M.; Jose-Yacaman, Miguel

    2014-01-01

    The structural order in ultrathin films of monolayer protected clusters (MPCs) is important in a number of application areas but can be difficult to demonstrate by conventional methods, particularly when the metallic core dimension, d, is in the intermediate size-range, 1.5 < d < 5.0 nm. Here, improved techniques for the synthesis of monodisperse thiolate-protected gold nanoparticles have made possible the production of dodecane-thiolate saturated ~ 4 ± 0.5 nm Au clusters with single-crystal core structure and morphology. An ultrathin ordered film or superlattice of these nanocrystal-core MPCs is prepared and investigated using aberration corrected scanning/transmission electron microscopy (STEM) which allowed imaging of long-range hexagonally ordered superlattices of the nanocrystals, separated by the thiolate groups. The lattice constants determined by direct imaging are in good agreement with those determined by small-angle electron diffraction. The STEM image revealed the characteristic grain boundary (GB) with sigma (Σ) 13 in the interface between two crystals. The formation and structures found are interpreted on the basis of theoretical calculations employing molecular dynamics (MD) simulations and coarse-grained (CG) approach. PMID:24875295

  18. Frequency down-conversion of 637 nm light to the telecommunication band for non-classical light emitted from NV centers in diamond.

    PubMed

    Ikuta, Rikizo; Kobayashi, Toshiki; Yasui, Shuto; Miki, Shigehito; Yamashita, Taro; Terai, Hirotaka; Fujiwara, Mikio; Yamamoto, Takashi; Koashi, Masato; Sasaki, Masahide; Wang, Zhen; Imoto, Nobuyuki

    2014-05-05

    We demonstrate a low-noise frequency down-conversion of photons at 637 nm to the telecommunication band at 1587 nm by the difference frequency generation in a periodically-poled lithium niobate. An internal conversion efficiency of the converter is estimated to be 0.44 at the maximum which is achieved by a pump power of 0.43 W, whereas a rate of internal background photons caused by the strong cw pump laser is estimated to be 9 kHz/mW within a bandwidth of about 1 nm. By using the experimental values related to the intrinsic property of the converter, and using the intensity correlation and the average photon number of a 637 nm input light pulse, we derive the intensity correlation of a converted telecom light pulse. Then we discuss feasibility of a single-photon frequency conversion to the telecommunication band for a long-distance quantum communication based on NV centers in diamond.

  19. Nano-manipulation of diamond-based single photon sources.

    PubMed

    Ampem-Lassen, E; Simpson, D A; Gibson, B C; Trpkovski, S; Hossain, F M; Huntington, S T; Ganesan, K; Hollenberg, L C L; Prawer, S

    2009-07-06

    The ability to manipulate nano-particles at the nano-scale is critical for the development of active quantum systems. This paper presents a technique to manipulate diamond nano-crystals at the nano-scale using a scanning electron microscope, nano-manipulator and custom tapered optical fibre probes. The manipulation of a approximately 300 nm diamond crystal, containing a single nitrogen-vacancy centre, onto the endface of an optical fibre is demonstrated. The emission properties of the single photon source post manipulation are in excellent agreement with those observed on the original substrate.

  20. Graphite to ultrafine nanocrystalline diamond phase transition model and growth restriction mechanism induced by nanosecond laser processing

    NASA Astrophysics Data System (ADS)

    Ren, X. D.; Liu, R.; Zheng, L. M.; Ren, Y. P.; Hu, Z. Z.; He, H.

    2015-10-01

    To have a clear insight into nanocrystal growth from graphite to diamond upon high energy pulsed laser irradiation of graphite suspension, synthesis of ultrafine nanocrystalline diamonds with laser energy set up from 0.3 J to 12 J, repetition rate of 10 Hz has been studied. The method allows synthesizing ultrafine nanocrystalline particles continuously at the ambient temperature and normal pressure. The particle size is shown independent of laser energy, which is ultrafine and ranges in 2-6 nm. The theoretical grown size of nano-diamonds is found in well agreement with the experiment results. Four kinds of production were found: nano-diamond, spherical carbon nano-particles, flocculent amorphous carbon, and graphene nano-ribbon rolls. A solid-vapor-plasma-liquid coexistence model describing phase transition from graphite to diamond induced by nanosecond laser processing was proposed. Graphene nano-ribbon rolls might be the intermediate phase in the conversion from graphite to diamond.

  1. Light emission from silicon with tin-containing nanocrystals

    SciTech Connect

    Roesgaard, Søren; Chevallier, Jacques; Hansen, John Lundsgaard; Jensen, Pia Bomholt; Larsen, Arne Nylandsted; Balling, Peter; Julsgaard, Brian; Gaiduk, Peter I.; Svane, Axel

    2015-07-15

    Tin-containing nanocrystals, embedded in silicon, have been fabricated by growing an epitaxial layer of Si{sub 1−x−y}Sn{sub x}C{sub y}, where x = 1.6 % and y = 0.04 % on a silicon substrate, followed by annealing at various temperatures ranging from 650 {sup ∘}C to 900 {sup ∘}C. The nanocrystal density and average diameters are determined by scanning transmission-electron microscopy to ≈10{sup 17} cm{sup −3} and ≈5 nm, respectively. Photoluminescence spectroscopy demonstrates that the light emission is very pronounced for samples annealed at 725 {sup ∘}C, and Rutherford back-scattering spectrometry shows that the nanocrystals are predominantly in the diamond-structured phase at this particular annealing temperature. The origin of the light emission is discussed.

  2. Pulsed photoconductivity in diamond upon quasi-continuous laser excitation at 222 nm at the formation of an electron-hole liquid

    NASA Astrophysics Data System (ADS)

    Lipatov, E. I.; Genin, D. E.; Tarasenko, V. F.

    2016-06-01

    An order-of-magnitude enhancement of the pulsed photocurrent in a polycrystalline diamond sample synthesized by chemical vapor deposition is observed under the conditions of formation of an electron-hole liquid. Nonequilibrium charge carriers are excited by laser pulses at a wavelength of 222 nm with FWHM pulse duration of 18 ns and peak intensity above 2.5 MW/cm2 upon cooling the sample to 90 K. For peak intensities of laser excitation lower than 1 MW/cm2, sample cooling from 300 to 90 K leads to a decrease in pulsed photocurrent by about a factor of 5. The observed increase in pulsed photocurrent is attributed to the formation of the electron-hole liquid.

  3. Grain boundaries and mechanical properties of nanocrystalline diamond films.

    SciTech Connect

    Busmann, H.-G.; Pageler, A.; Gruen, D. M.

    1999-08-06

    Phase-pure nanocrystalline diamond thin films grown from plasmas of a hydrogen-poor carbon argon gas mixture have been analyzed regarding their hardness and elastic moduli by means of a microindentor and a scanning acoustic microscope.The films are superhard and the moduli rival single crystal diamond. In addition, Raman spectroscopy with an excitation wavelength of 1064 nm shows a peak at 1438 l/cm and no peak above 1500 l/cm, and X-ray photoelectron spectroscopy a shake-up loss at 4.2 eV. This gives strong evidence for the existence of solitary double bonds in the films. The hardness and elasticity of the films then are explained by the assumption, that the solitary double bonds interconnect the nanocrystals in the films, leading to an intergrain boundary adhesion of similar strength as the intragrain diamond cohesion. The results are in good agreement with recent simulations of high-energy grain boundaries.

  4. Controllable red, green, blue (RGB) and bright white upconversion luminescence of Lu2O3:Yb3+/Er3+/Tm3+ nanocrystals through single laser excitation at 980 nm.

    PubMed

    Yang, Jun; Zhang, Cuimiao; Peng, Chong; Li, Chunxia; Wang, Lili; Chai, Ruitao; Lin, Jun

    2009-01-01

    Light fantastic! Lu(2)O(3):Yb(3+)/Er(3+)/Tm(3+) nanocrystals with controllable red, green, blue (RGB) and bright white upconversion luminescence by a single laser excitation of 980 nm have been successfully synthesized (see picture). Due to abundant UC PL colors, it can potentially be used as fluorophores in the field of color displays, back light, UC lasers, photonics, and biomedicine.Lu(2)O(3):Yb(3+)/Er(3+)/Tm(3+) nanocrystals have been successfully synthesized by a solvothermal process followed by a subsequent heat treatment at 800 degrees C. Powder X-ray diffraction, transmission electron microscopy, upconversion photoluminescence spectra, and kinetic decay were used to characterize the samples. Under single-wavelength diode laser excitation of 980 nm, the bright blue emissions of Lu(2)O(3):Yb(3+), Tm(3+) nanocrystals near 477 and 490 nm were observed due to the (1)G(4)-->(3)H(6) transition of Tm(3+). The bright green UC emissions of Lu(2)O(3):Er(3+) nanocrystals appeared near 540 and 565 nm were observed and assigned to the (2)H(11/2)-->(4)I(15/2) and (4)S(3/2)-->(4)I(15/2) transitions, respectively, of Er(3+). The ratio of the intensity of green luminescence to that of red luminescence decreases with an increase of concentration of Yb(3+) in Lu(2)O(3):Er(3+) nanocrystals. In sufficient quantities of Yb(3+) with resprct to Er(3+), the bright red UC emission of Lu(2)O(3):Yb(3+)/Er(3+) centered at 662 nm was predominant, due to the (4)F(9/2)-->(4)I(15/2) transition of Er(3+). Based on the generation of red, green, and blue emissions in the different doped Lu(2)O(3):RE(3+) nanocrystals, it is possible to produce the luminescence with a wide spectrum of colors, including white, by the appropriate doping of Yb(3+), Tm(3+), and Er(3+) in the present Lu(2)O(3) nanocrystals. Namely, Lu(2)O(3):3 %Yb(3+)/0.2 %Tm(3+)/0.4 %Er(3+) nanocrystals show suitable intensities of blue, green, and red (RGB) emission, resulting in the production of perfect and bright white light

  5. Nanocrystal-Powered Nanomotor

    SciTech Connect

    Regan, B.C.; Aloni, S.; Jensen, K.; Ritchie, R.O.; Zettl, A.

    2005-07-05

    We have constructed and operated a nanoscale linear motorpowered by a single metal nanocrystal ram sandwiched between mechanicallever arms. Low-level electrical voltages applied to the carbon nanotubelever arms cause the nanocrystal to grow or shrink in a controlledmanner. The length of the ram is adjustable from 0 to more than 150 nm,with extension speeds exceeding 1900 nm/s. The thermodynamic principlesgoverning motor operation resemble those driving frost heave, a naturalsolid-state linear motor.

  6. Natural occurrence of pure nano-polycrystalline diamond from impact crater

    NASA Astrophysics Data System (ADS)

    Ohfuji, Hiroaki; Irifune, Tetsuo; Litasov, Konstantin D.; Yamashita, Tomoharu; Isobe, Futoshi; Afanasiev, Valentin P.; Pokhilenko, Nikolai P.

    2015-10-01

    Consolidated bodies of polycrystalline diamond with grain sizes less than 100 nm, nano-polycrystalline diamond (NPD), has been experimentally produced by direct conversion of graphite at high pressure and high temperature. NPD has superior hardness, toughness and wear resistance to single-crystalline diamonds because of its peculiar nano-textures, and has been successfully used for industrial and scientific applications. Such sintered nanodiamonds have, however, not been found in natural mantle diamonds. Here we identified natural pure NPD, which was produced by a large meteoritic impact about 35 Ma ago in Russia. The impact diamonds consist of well-sintered equigranular nanocrystals (5-50 nm), similar to synthetic NPD, but with distinct [111] preferred orientation. They formed through the martensitic transformation from single-crystal graphite. Stress-induced local fragmentation of the source graphite and subsequent rapid transformation to diamond in the limited time scale result in multiple diamond nucleation and suppression of the overall grain growth, producing the unique nanocrystalline texture of natural NPD. A huge amount of natural NPD is expected to be present in the Popigai crater, which is potentially important for applications as novel ultra-hard material.

  7. Natural occurrence of pure nano-polycrystalline diamond from impact crater

    PubMed Central

    Ohfuji, Hiroaki; Irifune, Tetsuo; Litasov, Konstantin D.; Yamashita, Tomoharu; Isobe, Futoshi; Afanasiev, Valentin P.; Pokhilenko, Nikolai P.

    2015-01-01

    Consolidated bodies of polycrystalline diamond with grain sizes less than 100 nm, nano-polycrystalline diamond (NPD), has been experimentally produced by direct conversion of graphite at high pressure and high temperature. NPD has superior hardness, toughness and wear resistance to single-crystalline diamonds because of its peculiar nano-textures, and has been successfully used for industrial and scientific applications. Such sintered nanodiamonds have, however, not been found in natural mantle diamonds. Here we identified natural pure NPD, which was produced by a large meteoritic impact about 35 Ma ago in Russia. The impact diamonds consist of well-sintered equigranular nanocrystals (5–50 nm), similar to synthetic NPD, but with distinct [111] preferred orientation. They formed through the martensitic transformation from single-crystal graphite. Stress-induced local fragmentation of the source graphite and subsequent rapid transformation to diamond in the limited time scale result in multiple diamond nucleation and suppression of the overall grain growth, producing the unique nanocrystalline texture of natural NPD. A huge amount of natural NPD is expected to be present in the Popigai crater, which is potentially important for applications as novel ultra-hard material. PMID:26424384

  8. Silicon Nanocrystal Laser

    SciTech Connect

    Yu, J

    2005-03-09

    The purpose of this feasibility study project was to attempt to demonstrate the silicon-nanocrystal-based laser. Such a silicon laser (made using conventional silicon-manufacturing technologies) would provide the crucial missing link that would enable a completely-silicon-based photonic system. We prepared thin layers of silicon nanocrystal material by ion-implanting Si in fused silica substrates, followed by a high temperature anneal process. These Si nanocrystals produced intense photoluminescence when optically pumped with ultraviolet light. Laser structures based on Fabry-Perot cavity and distributed feedback (DFB) designs were fabricated using the Si nanocrystals as the ''lasing'' medium. We optically pumped the samples with CW lasers at 413nm wavelength to quickly assess the feasibility of making lasers out of the Nanocrystal Si material and to verify the gain coefficients reported by other research groups.

  9. On Ultrasmall Nanocrystals

    PubMed Central

    McBride, James R.; Dukes, Albert D.; Schreuder, Michael A.; Rosenthal, Sandra J.

    2010-01-01

    Ultrasmall nanocrystals are a growing sub-class of traditional nanocrystals that exhibit new properties at diameters typically below 2 nm. In this review, we define what constitutes an ultrasmall nanoparticle while distinguishing between ultrasmall and magic-size nanoparticles. After a brief overview of ultrasmall nanoparticles, including ultrasmall gold clusters, our recent work is presented covering the optical properties, structure, and application of ultrasmall CdSe nanocrystals. This unique material has potential application in solid state lighting due to its balanced white emission. This section is followed by a discussion on the blurring boundary between what can be considered a nanoparticle and a molecule. PMID:21132106

  10. Solution Sythesis Of Geranium Nanocrystals: Success And Open Challenges

    SciTech Connect

    Casula, M; Galli, G; Saw, C; Zaitseva, N; Gerion, D; van Buuren, T; Fakra, S

    2003-12-15

    We present a two-steps synthesis route that yields nanometer size crystalline germanium in the form of a black powder. It relies on high temperature decomposition of tetraethylgermane (TEG) in organic solvents. The presence of pure germanium with diamond structure is unambiguously attested by powder XRD measurements. Low resolution TEM indicates that the particles are between {approx}5 to 30 nm in size depending on the synthesis conditions. The as-synthesized Ge powders can be stored in air for months and no oxidation occurs. The Ge powders are sparingly soluble in conventional solvents because Ge nanocrystals are likely embedded in a matrix, composed mainly of C=C, C-C, and C-H bonds. The presence of residual organic by-products impedes probing of the optical properties of the dots. Also, we discuss drawbacks and open challenges in high temperature solution synthesis of Ge nanocrystals that could also be faced in the synthesis of Si nanocrystals. Overall, our results call for a cautious interpretation of reported optical properties of Ge and Si nanocrystals obtained by high temperature solution methods.

  11. Microwave synthesis of high-quality and uniform 4 nm ZnFe2O4 nanocrystals for application in energy storage and nanomagnetics

    PubMed Central

    Witte, Ralf; Knapp, Michael; Bauer, Sondes; Baumbach, Tilo

    2016-01-01

    Summary Magnetic nanocrystals with a narrow size distribution hold promise for many applications in different areas ranging from biomedicine to electronics and energy storage. Herein, the microwave-assisted sol–gel synthesis and thorough characterization of size-monodisperse zinc ferrite nanoparticles of spherical shape is reported. X-ray diffraction, 57Fe Mössbauer spectroscopy and X-ray photoelectron spectroscopy all show that the material is both chemically and phase-pure and adopts a partially inverted spinel structure with Fe3+ ions residing on tetrahedral and octahedral sites according to (Zn0.32Fe0.68)tet[Zn0.68Fe1.32]octO4±δ. Electron microscopy and direct-current magnetometry confirm the size uniformity of the nanocrystals, while frequency-dependent alternating-current magnetic susceptibility measurements indicate the presence of a superspin glass state with a freezing temperature of about 22 K. Furthermore, as demonstrated by galvanostatic charge–discharge tests and ex situ X-ray absorption near edge structure spectroscopy, the as-prepared zinc ferrite nanocrystals can be used as a high-capacity anode material for Li-ion batteries, showing little capacity fade – after activation – over hundreds of cycles. Overall, in addition to the good material characteristics, it is remarkable that the microwave-based synthetic route is simple, easily reproducible and scalable. PMID:27826509

  12. Microwave synthesis of high-quality and uniform 4 nm ZnFe2O4 nanocrystals for application in energy storage and nanomagnetics.

    PubMed

    Suchomski, Christian; Breitung, Ben; Witte, Ralf; Knapp, Michael; Bauer, Sondes; Baumbach, Tilo; Reitz, Christian; Brezesinski, Torsten

    2016-01-01

    Magnetic nanocrystals with a narrow size distribution hold promise for many applications in different areas ranging from biomedicine to electronics and energy storage. Herein, the microwave-assisted sol-gel synthesis and thorough characterization of size-monodisperse zinc ferrite nanoparticles of spherical shape is reported. X-ray diffraction, (57)Fe Mössbauer spectroscopy and X-ray photoelectron spectroscopy all show that the material is both chemically and phase-pure and adopts a partially inverted spinel structure with Fe(3+) ions residing on tetrahedral and octahedral sites according to (Zn0.32Fe0.68)(tet)[Zn0.68Fe1.32](oct)O4±δ. Electron microscopy and direct-current magnetometry confirm the size uniformity of the nanocrystals, while frequency-dependent alternating-current magnetic susceptibility measurements indicate the presence of a superspin glass state with a freezing temperature of about 22 K. Furthermore, as demonstrated by galvanostatic charge-discharge tests and ex situ X-ray absorption near edge structure spectroscopy, the as-prepared zinc ferrite nanocrystals can be used as a high-capacity anode material for Li-ion batteries, showing little capacity fade - after activation - over hundreds of cycles. Overall, in addition to the good material characteristics, it is remarkable that the microwave-based synthetic route is simple, easily reproducible and scalable.

  13. Industrial diamond

    USGS Publications Warehouse

    Olson, D.W.

    2001-01-01

    An overview of the industrial diamond industry is provided. More than 90 percent of the industrial diamond consumed in the U.S. and the rest of the world is manufactured diamond. Ireland, Japan, Russia, and the U.S. produce 75 percent of the global industrial diamond output. In 2000, the U.S. was the largest market for industrial diamond. Industrial diamond applications, prices for industrial diamonds, imports and exports of industrial diamonds, the National Defense Stockpile of industrial diamonds, and the outlook for the industrial diamond market are discussed.

  14. Sorting fluorescent nanocrystals with DNA

    SciTech Connect

    Gerion, Daniele; Parak, Wolfgang J.; Williams, Shara C.; Zanchet, Daniela; Micheel, Christine M.; Alivisatos, A. Paul

    2001-12-10

    Semiconductor nanocrystals with narrow and tunable fluorescence are covalently linked to oligonucleotides. These biocompounds retain the properties of both nanocrystals and DNA. Therefore, different sequences of DNA can be coded with nanocrystals and still preserve their ability to hybridize to their complements. We report the case where four different sequences of DNA are linked to four nanocrystal samples having different colors of emission in the range of 530-640 nm. When the DNA-nanocrystal conjugates are mixed together, it is possible to sort each type of nanoparticle using hybridization on a defined micrometer -size surface containing the complementary oligonucleotide. Detection of sorting requires only a single excitation source and an epifluorescence microscope. The possibility of directing fluorescent nanocrystals towards specific biological targets and detecting them, combined with their superior photo-stability compared to organic dyes, opens the way to improved biolabeling experiments, such as gene mapping on a nanometer scale or multicolor microarray analysis.

  15. Cellulose nanocrystal submonolayers by spin coating.

    PubMed

    Kontturi, Eero; Johansson, Leena-Sisko; Kontturi, Katri S; Ahonen, Päivi; Thüne, Peter C; Laine, Janne

    2007-09-11

    Dilute concentrations of cellulose nanocrystal solutions were spin coated onto different substrates to investigate the effect of the substrate on the nanocrystal submonolayers. Three substrates were probed: silica, titania, and amorphous cellulose. According to atomic force microscopy (AFM) images, anionic cellulose nanocrystals formed small aggregates on the anionic silica substrate, whereas a uniform two-dimensional distribution of nanocrystals was achieved on the cationic titania substrate. The uniform distribution of cellulose nanocrystal submonolayers on titania is an important factor when dimensional analysis of the nanocrystals is desired. Furthermore, the amount of nanocrystals deposited on titania was multifold in comparison to the amounts on silica, as revealed by AFM image analysis and X-ray photoelectron spectroscopy. Amorphous cellulose, the third substrate, resulted in a somewhat homogeneous distribution of the nanocrystal submonolayers, but the amounts were as low as those on the silica substrate. These differences in the cellulose nanocrystal deposition were attributed to electrostatic effects: anionic cellulose nanocrystals are adsorbed on cationic titania in addition to the normal spin coating deposition. The anionic silica surface, on the other hand, causes aggregation of the weakly anionic cellulose nanocrystals which are forced on the repulsive substrate by spin coating. The electrostatically driven adsorption also influences the film thickness of continuous ultrathin films of cellulose nanocrystals. The thicker films of charged nanocrystals on a substrate of opposite charge means that the film thickness is not independent of the substrate when spin coating cellulose nanocrystals in the ultrathin regime (<100 nm).

  16. Investigation of the Surface Stress in SiC and Diamond Nanocrystals by In-situ High Pressure Powder Diffraction Technique

    NASA Technical Reports Server (NTRS)

    Palosz, B.; Stelmakh, S.; Grzanka, E.; Gierlotka, S.; Zhao, Y.; Palosz, W.

    2003-01-01

    The real atomic structure of nanocrystals determines key properties of the materials. For such materials the serious experimental problem lies in obtaining sufficiently accurate measurements of the structural parameters of the crystals, since very small crystals constitute rather a two-phase than a uniform crystallographic phase system. As a result, elastic properties of nanograins may be expected to reflect a dual nature of their structure, with a corresponding set of different elastic property parameters. We studied those properties by in-situ high-pressure powder diffraction technique. For nanocrystalline, even one-phase materials such measurements are particularly difficult to make since determination of the lattice parameters of very small crystals presents a challenge due to inherent limitations of standard elaboration of powder diffractograms. In this investigation we used our methodology of the structural analysis, the 'apparent lattice parameter' (alp) concept. The methodology allowed us to avoid the traps (if applied to nanocrystals) of standard powder diffraction evaluation techniques. The experiments were performed for nanocrystalline Sic and GaN powders using synchrotron sources. We applied both hydrostatic and isostatic pressures in the range of up to 40 GPa. Elastic properties of the samples were examined based on the measurements of a change of the lattice parameters with pressure. The results show a dual nature of the mechanical properties (compressibilities) of the materials, indicating a complex, core-shell structure of the grains.

  17. Transient photoresponse of nitrogen-doped ultrananocrystalline diamond electrodes in saline solution

    NASA Astrophysics Data System (ADS)

    Ahnood, Arman; Simonov, Alexandr N.; Laird, Jamie S.; Maturana, Matias I.; Ganesan, Kumaravelu; Stacey, Alastair; Ibbotson, Michael R.; Spiccia, Leone; Prawer, Steven

    2016-03-01

    Beyond conventional electrically-driven neuronal stimulation methods, there is a growing interest in optically-driven approaches. In recent years, nitrogen-doped ultrananocrystalline diamond (N-UNCD) has emerged as a strong material candidate for use in electrically-driven stimulation electrodes. This work investigates the electrochemical activity of N-UNCD in response to pulsed illumination, to assess its potential for use as an optically-driven stimulation electrode. Whilst N-UNCD in the as-grown state exhibits a weak photoresponse, the oxygen plasma treated film exhibits two orders of magnitude enhancement in its sub-bandgap open circuit photovoltage response. The enhancement is attributed to the formation of a dense network of oxygen-terminated diamond nanocrystals at the N-UNCD surface. Electrically connected to the N-UNCD bulk via sub-surface graphitic grain boundaries, these diamond nanocrystals introduce a semiconducting barrier between the sub-surface graphitic semimetal and the electrolyte solution, leading to a photovoltage under irradiation with wavelengths of λ = 450 nm and shorter. Within the safe optical exposure limit of 2 mW mm-2, charge injection capacity of 0.01 mC cm-2 is achieved using a 15 × 15 μm electrode, meeting the requirements for extracellular and intercellular stimulation. The nanoscale nature of processes presented here along with the diamond's biocompatibility and biostability open an avenue for the use of oxygen treated N-UNCD as optically driven stimulating electrodes.

  18. Catalyst-free synthesis of transparent, mesoporous diamond monoliths from periodic mesoporous carbon CMK-8

    SciTech Connect

    Zhang, Li; Mohanty, Paritosh; Coombs, Neil; Fei, Yingwei; Mao, Ho-kwang; Landskrom, Kai

    2010-07-19

    We report on the synthesis of optically transparent, mesoporous, monolithic diamond from periodic mesoporous carbon CMK-8 at a pressure of 21 GPa. The phase transformation is already complete at a mild synthesis temperature of 1,300 °C without the need of a catalyst. Surprisingly, the diamond is obtained as a mesoporous material despite the extreme pressure. X-ray diffraction, SEM, transmission electron microscopy, selected area electron diffraction, high-resolution transmission electron microscopy, and Z-contrast experiments suggest that the mesoporous diamond is composed of interconnected diamond nanocrystals having diameters around 5–10 nm. The Brunauer Emmett Teller surface area was determined to be 33 m2 g-1 according Kr sorption data. The mesostructure is diminished yet still detectable when the diamond is produced from CMK-8 at 1,600 °C and 21 GPa. The temperature dependence of the porosity indicates that the mesoporous diamond exists metastable and withstands transformation into a dense form at a significant rate due to its high kinetic inertness at the mild synthesis temperature. The findings point toward ultrahard porous materials with potential as mechanically highly stable membranes.

  19. Diamond Smoothing Tools

    NASA Technical Reports Server (NTRS)

    Voronov, Oleg

    2007-01-01

    Diamond smoothing tools have been proposed for use in conjunction with diamond cutting tools that are used in many finish-machining operations. Diamond machining (including finishing) is often used, for example, in fabrication of precise metal mirrors. A diamond smoothing tool according to the proposal would have a smooth spherical surface. For a given finish machining operation, the smoothing tool would be mounted next to the cutting tool. The smoothing tool would slide on the machined surface left behind by the cutting tool, plastically deforming the surface material and thereby reducing the roughness of the surface, closing microcracks and otherwise generally reducing or eliminating microscopic surface and subsurface defects, and increasing the microhardness of the surface layer. It has been estimated that if smoothing tools of this type were used in conjunction with cutting tools on sufficiently precise lathes, it would be possible to reduce the roughness of machined surfaces to as little as 3 nm. A tool according to the proposal would consist of a smoothing insert in a metal holder. The smoothing insert would be made from a diamond/metal functionally graded composite rod preform, which, in turn, would be made by sintering together a bulk single-crystal or polycrystalline diamond, a diamond powder, and a metallic alloy at high pressure. To form the spherical smoothing tip, the diamond end of the preform would be subjected to flat grinding, conical grinding, spherical grinding using diamond wheels, and finally spherical polishing and/or buffing using diamond powders. If the diamond were a single crystal, then it would be crystallographically oriented, relative to the machining motion, to minimize its wear and maximize its hardness. Spherically polished diamonds could also be useful for purposes other than smoothing in finish machining: They would likely also be suitable for use as heat-resistant, wear-resistant, unlubricated sliding-fit bearing inserts.

  20. Pinned emission from ultrasmall cadmium selenide nanocrystals.

    PubMed

    Dukes, Albert D; Schreuder, Michael A; Sammons, Jessica A; McBride, James R; Smith, Nathanael J; Rosenthal, Sandra J

    2008-09-28

    We report pinning of the emission spectrum in ultrasmall CdSe nanocrystals with a diameter of 1.7 nm and smaller. It was observed that the first emission feature ceased to blueshift once the band edge absorption reached 420 nm, though the band edge absorption continued to blueshift with decreasing nanocrystal diameter.

  1. Sub-10 nm Sr2LuF7:Yb/Er@Sr2GdF7@SrF2 Up-Conversion Nanocrystals for Up-Conversion Luminescence-Magnetic Resonance-Computed Tomography Trimodal Bioimaging.

    PubMed

    Chen, Cailing; Liu, Jianhua; Chen, Ying; Li, Chunguang; Liu, Xiaomin; Huang, He; Liang, Chen; Lou, Yue; Shi, Zhan; Feng, Shouhua

    2017-02-22

    Herein, sub-10 nm core-shell nanocrystals (NCs), which select Sr2LuF7:Yb/Er as core, Sr2GdF7 as middle shell, and SrF2 as an outermost shell, were synthesized by a seed-mediated growth process. The NCs possess good crystallinity, morphology, and up-conversion luminescent properties. After modification by polyethylenimine branched (PEI), in vitro cell up-conversion imaging with low autofluorescence was realized. Due to the presence of Gd(3+) ions, in vivo magnetic resonance (MR) imaging was also achieved with these designed NCs. More significantly, these special core-shell NCs exhibited high contrast in in vivo X-ray computed tomography (CT) imaging because of their good X-ray absorption ability. These results indicate that the core-shell up-conversion NCs can serve as promising contrast agents for up-conversion luminescence-MR-CT trimodal bioimaging.

  2. Industrial diamond

    USGS Publications Warehouse

    Olson, D.W.

    2003-01-01

    Statistics on the production, consumption, cost, trade, and government stockpile of natural and synthetic industrial diamond are provided. The outlook for the industrial diamond market is also considered.

  3. Graphite to ultrafine nanocrystalline diamond phase transition model and growth restriction mechanism induced by nanosecond laser processing

    SciTech Connect

    Ren, X. D. Liu, R.; Zheng, L. M.; Ren, Y. P.; Hu, Z. Z.; He, H.

    2015-10-05

    To have a clear insight into nanocrystal growth from graphite to diamond upon high energy pulsed laser irradiation of graphite suspension, synthesis of ultrafine nanocrystalline diamonds with laser energy set up from 0.3 J to 12 J, repetition rate of 10 Hz has been studied. The method allows synthesizing ultrafine nanocrystalline particles continuously at the ambient temperature and normal pressure. The particle size is shown independent of laser energy, which is ultrafine and ranges in 2–6 nm. The theoretical grown size of nano-diamonds is found in well agreement with the experiment results. Four kinds of production were found: nano-diamond, spherical carbon nano-particles, flocculent amorphous carbon, and graphene nano-ribbon rolls. A solid-vapor-plasma-liquid coexistence model describing phase transition from graphite to diamond induced by nanosecond laser processing was proposed. Graphene nano-ribbon rolls might be the intermediate phase in the conversion from graphite to diamond.

  4. Applications Of Diamond In Optics

    NASA Astrophysics Data System (ADS)

    Seal, M.; van Enckevort, W. J. P.

    1989-01-01

    This paper reviews existing and new applications of single crystal diamond, both natural and synthetic, in optical science. The traditional application is as transmissive components, making use of the very wide spectral transmission range, high thermal conductivity, and chemical inertness of diamond. Diamond windows for corrosive environments are well known; diamond surgical endoscope components are under development; and the use of sharpened diamonds as combined surgical cutting instruments and light pipes for internal illumination of the edge is commercial reality. The superb ability of diamond to conduct heat, combined with its very low thermal expansion coefficient makes it suitable for the transmission of high power laser energy, though there is a problem currently being addressed of a high surface reflection coefficient. It is very probable that CVD diamond-like films will form good anti-reflection coatings for diamond. In new applications, the technology of making diamond lenses is being developed. The use of diamond as a detector of ionising radiation is well known, but recent work shows its possibilities in thermoluminescent as well as conduction and pulse counting modes. There are further possibilities of using diamond for the detection and measurement of optical radiation. Examples are low, medium, and high intensity far ultraviolet (< 225 nm) and very high intensity near ultraviolet and visible light from excimer, dye, or argon lasers. Diamond is very radiation resistant! Sensitivities, response times and impurity trap levels have been measured and appropriate diamonds can be synthesised. The use of diamond as fast opto-electronic switches has been reported in the literature and the mechanical and thermal design of diamond "heat sink" substrates for semiconductor laser diodes is advancing rapidly.

  5. Copper Selenide Nanocrystals for Photothermal Therapy

    PubMed Central

    Hessel, Colin M.; Pattani, Varun; Rasch, Michael; Panthani, Matthew G.; Koo, Bonil; Tunnell, James W.; Korgel, Brian A.

    2011-01-01

    Ligand-stabilized copper selenide (Cu2−xSe) nanocrystals, approximately 16 nm in diameter, were synthesized by a colloidal hot injection method and coated with amphiphilic polymer. The nanocrystals readily disperse in water and exhibit strong near infrared (NIR) optical absorption with a high molar extinction coefficient of 7.7 × 107 cm−1 M−1 at 980 nm. When excited with 800 nm light, the Cu2−xSe nanocrystals produce significant photothermal heating with a photothermal transduction efficiency of 22%, comparable to nanorods and nanoshells of gold (Au). In vitro photothermal heating of Cu2−xSe nanocrystals in the presence of human colorectal cancer cell (HCT-116) led to cell destruction after 5 minutes of laser irradiation at 33 W/cm2, demonstrating the viabilitiy of Cu2−xSe nanocrystals for photothermal therapy applications. PMID:21553924

  6. Copper selenide nanocrystals for photothermal therapy.

    PubMed

    Hessel, Colin M; Pattani, Varun P; Rasch, Michael; Panthani, Matthew G; Koo, Bonil; Tunnell, James W; Korgel, Brian A

    2011-06-08

    Ligand-stabilized copper selenide (Cu(2-x)Se) nanocrystals, approximately 16 nm in diameter, were synthesized by a colloidal hot injection method and coated with amphiphilic polymer. The nanocrystals readily disperse in water and exhibit strong near-infrared (NIR) optical absorption with a high molar extinction coefficient of 7.7 × 10(7) cm(-1) M(-1) at 980 nm. When excited with 800 nm light, the Cu(2-x)Se nanocrystals produce significant photothermal heating with a photothermal transduction efficiency of 22%, comparable to nanorods and nanoshells of gold (Au). In vitro photothermal heating of Cu(2-x)Se nanocrystals in the presence of human colorectal cancer cell (HCT-116) led to cell destruction after 5 min of laser irradiation at 33 W/cm(2), demonstrating the viabilitiy of Cu(2-x)Se nanocrystals for photothermal therapy applications.

  7. Fabrication of diamond shells

    SciTech Connect

    Hamza, Alex V.; Biener, Juergen; Wild, Christoph; Woerner, Eckhard

    2016-11-01

    A novel method for fabricating diamond shells is introduced. The fabrication of such shells is a multi-step process, which involves diamond chemical vapor deposition on predetermined mandrels followed by polishing, microfabrication of holes, and removal of the mandrel by an etch process. The resultant shells of the present invention can be configured with a surface roughness at the nanometer level (e.g., on the order of down to about 10 nm RMS) on a mm length scale, and exhibit excellent hardness/strength, and good transparency in the both the infra-red and visible. Specifically, a novel process is disclosed herein, which allows coating of spherical substrates with optical-quality diamond films or nanocrystalline diamond films.

  8. Hollow nanocrystals and method of making

    DOEpatents

    Alivisatos, A. Paul; Yin, Yadong; Erdonmez, Can Kerem

    2011-07-05

    Described herein are hollow nanocrystals having various shapes that can be produced by a simple chemical process. The hollow nanocrystals described herein may have a shell as thin as 0.5 nm and outside diameters that can be controlled by the process of making.

  9. Industrial diamond

    USGS Publications Warehouse

    Olson, D.W.

    2012-01-01

    Estimated 2011 world production of natural and synthetic industrial diamond was about 4.45 billion carats. During 2011, natural industrial diamonds were produced in more than 20 countries, and synthetic industrial diamond was produced in at least 13 countries. About 98 percent of the combined natural and synthetic global output was produced in China, Ireland, Japan, Russia, South Africa and the United States. China is the world's leading producer of synthetic industrial diamond followed by Russia and the United States.

  10. Nanocrystal synthesis

    SciTech Connect

    Tisdale, William; Prins, Ferry; Weidman, Mark; Beck, Megan

    2016-11-01

    A method of preparing monodisperse MX semiconductor nanocrystals can include contacting an M-containing precursor with an X donor to form a mixture, where the molar ratio between the M containing precursor and the X donor is large. Alternatively, if additional X donor is added during the reaction, a smaller ratio between the M containing precursor and the X donor can be used to prepare monodisperse MX semiconductor nanocrystals.

  11. Industrial diamond

    USGS Publications Warehouse

    Olson, D.W.

    2013-01-01

    Estimated 2012 world production of natural and synthetic industrial diamond was about 4.45 billion carats. During 2012, natural industrial diamonds were produced in at least 20 countries, and synthetic industrial diamond was produced in at least 12 countries. About 99 percent of the combined natural and synthetic global output was produced in Belarus, China, Ireland, Japan, Russia, South Africa and the United States. During 2012, China was the world’s leading producer of synthetic industrial diamond followed by the United States and Russia. In 2012, the two U.S. synthetic producers, one in Pennsylvania and the other in Ohio, had an estimated output of 103 million carats, valued at about $70.6 million. This was an estimated 43.7 million carats of synthetic diamond bort, grit, and dust and powder with a value of $14.5 million combined with an estimated 59.7 million carats of synthetic diamond stone with a value of $56.1 million. Also in 2012, nine U.S. firms manufactured polycrystalline diamond (PCD) from synthetic diamond grit and powder. The United States government does not collect or maintain data for either domestic PCD producers or domestic chemical vapor deposition (CVD) diamond producers for quantity or value of annual production. Current trade and consumption quantity data are not available for PCD or for CVD diamond. For these reasons, PCD and CVD diamond are not included in the industrial diamond quantitative data reported here.

  12. Industrial diamond

    USGS Publications Warehouse

    Olson, D.W.

    2011-01-01

    Estimated world production of natural and synthetic industrial diamond was about 4.44 billion carats in 2010. Natural industrial diamond deposits have been found in more than 35 countries, and synthetic industrial diamond is produced in at least 15 countries.

  13. Industrial diamond

    USGS Publications Warehouse

    Olson, D.W.

    2006-01-01

    In 2005, estimated world production of natural and synthetic industrial diamond was 630 million carats. Natural industrial diamond deposits were found in more than 35 countries. Synthetic industrial diamond is produced in at least 15 countries. More than 81% of the combined natural and synthetic global output was produced in Ireland, Japan, Russia, South Africa and the United States.

  14. Industrial diamond

    USGS Publications Warehouse

    Olson, D.W.

    2000-01-01

    Part of the 1999 Industrial Minerals Review. A review of the state of the global industrial diamond industry in 1999 is presented. World consumption of industrial diamond has increased annually in recent years, with an estimated 500 million carats valued between $650 million and $800 million consumed in 1999. In 1999, the U.S. was the world's largest market for industrial diamond and was also one of the world's main producers; the others were Ireland, Russia, and South Africa. Uses of industrial diamonds are discussed, and prices of natural and synthetic industrial diamond are reported.

  15. Optical Properties of CdSe/ZnS Nanocrystals

    PubMed Central

    Gaigalas, Adolfas K; DeRose, Paul; Wang, Lili; Zhang, Yu-Zhong

    2014-01-01

    Measurements are presented of the absorbance, fluorescence emission, fluorescence quantum yield, and fluorescence lifetime of CdSe/ZnS nanocrystals, also known as quantum dots (QDs). The study included three groups of nanocrystals whose surfaces were either passivated with organic molecules, modified further with carboxyl groups, or conjugated with CD14 mouse anti-human antibodies. The surface modifications had observable effects on the optical properties of the nanocrystals. The oscillator strength (OS) of the band edge transition was about 1.0 for the nanocrystals emitting at 565 nm, 605 nm, and 655 nm. The OS could not be determined for QDs with emission at 700 nm and 800 nm. The fluorescence lifetimes varied from 26 ns for nanocrystals emitting near 600 nm to 150 ns for nanocrystals emitting near 800 nm. The quantum yield ranged between 0.4 and 0.9 for the nanocrystals in this study. A brightness index (BI) was used to evaluate the suitability of the nanocrystal labels for flow cytometer measurements. Most QD labels are at least as bright as fluorescein for applications in flow cytometer assays with 488 nm excitation. For optimal brightness the QDs should be excited with 405 nm light. We observed a strong dependence of the QD absorbance at 250 nm on the surface modification of the QD. PMID:26601047

  16. Size quantization in Cu2Se nanocrystals

    NASA Astrophysics Data System (ADS)

    Govindraju, S.; Kalenga, M. P.; Airo, M.; Moloto, M. J.; Sikhwivhilu, L. M.; Moloto, N.

    2014-12-01

    Herein we report on the synthesis of size quantized copper selenide nanocrystals via the colloidal method. Different colours of the sample were obtained at different time intervals indicative of the sizes of the nanocrystals. The absorption band edges were blue-shifted from bulk indicative of quantum confinement. This was corroborated by the TEM results that showed very small particles ranging from 2 nm to 7 nm. This work therefore shows a phenomenon readily observed in cadmium chalcogenide nanocrystals but has never been reported for copper based chalcogenides.

  17. Silicon and germanium nanocrystals: properties and characterization

    PubMed Central

    Carvalho, Alexandra; Coutinho, José

    2014-01-01

    Summary Group-IV nanocrystals have emerged as a promising group of materials that extends the realm of application of bulk diamond, silicon, germanium and related materials beyond their traditional boundaries. Over the last two decades of research, their potential for application in areas such as optoelectronic applications and memory devices has been progressively unraveled. Nevertheless, new challenges with no parallel in the respective bulk material counterparts have arisen. In this review, we consider what has been achieved and what are the current limitations with regard to growth, characterization and modeling of silicon and germanium nanocrystals and related materials. PMID:25383290

  18. Photoluminescence and Raman spectroscopy studies of Eu3+-doped rutile TiO2 nanocrystals at high pressures

    NASA Astrophysics Data System (ADS)

    Zeng, Q. G.; Ding, Z. J.; Lei, B. F.; Sheng, Y. Q.; Zhang, Z. M.

    2012-09-01

    Nanocrystal samples (particle size about 90 nm) of Eu3+-doped rutile titanium dioxide (TiO2) nanocrystals (rutile Eu3+/TiO2 nanocrystals) were synthesized by the sol-gel method with hydrothermal treatment. The pressure effect on photoluminescence (PL) and Raman spectra of the rutile Eu3+/TiO2 nanocrystals was investigated with a diamond anvil cell under hydrostatic pressure condition. Raman spectra of the samples at high pressures indicated that the critical pressure for the transition from the rutile phase to a new baddeleyite-type phase was between 10 and 14.2 GPa. The position of Raman bands shifted to high wavenumbers and the PL intensity of 5D 0→7F 2 transition of Eu3+ decreased down to zero with the increase of pressure before the phase transition occurred. After releasing the pressure, the rutile phase was not recovered and a α-PbO2-type phase was observed at ambient pressure.

  19. Tailorable, Visible Light Emission From Silicon Nanocrystals

    SciTech Connect

    Samara, G.A.; Wilcoxon, J.P.

    1999-07-20

    J. P. Wilcoxon and G. A. Samara Crystalline, size-selected Si nanocrystals in the size range 1.8-10 nm grown in inverse micellar cages exhibit highly structured optical absorption and photoluminescence (PL) across the visible range of the spectrum. The most intense PL for the smallest nanocrystals produced This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. to induce a useful level of visible photoluminescence (PL) from silicon (Si). The approaches understood. Visible PL has been observed from Si nanocrystals, or quantum dots, produced by a variety of techniques including aerosols,2 colloids,3 and ion implantation.4 However, all of The optical absorption spectra of our nanocrystals are much richer in spectral features spectrum of bulk Si where the spectral features reflect the details of the band structure shown in nanocrystals estimated to have a Si core diameter of 1-2 nm. These measured quantum those in the spectrum of bulk Si in Fig. 1 are striking indicating that nanocrystals of this size 8-Room temperature PL results on an HPLC size-selected, purified 2 nm nanocrystals but blue shifted by -0.4 eV due to quantum confinement. Excitation at 245 nm yields

  20. Diamond nanocrystals for photonics and sensing

    NASA Astrophysics Data System (ADS)

    Aharonovich, Igor

    2014-01-01

    Fluorescent nanodiamonds (FNDs) are becoming a pivotal material in a variety of applications spanning sensing, bio-labeling and nanophotonics. The unique feature of these nanoparticles is their ability to host bright, optically active, photostable defects (color centers) that emit across the entire spectral range. In conjunction with their chemical stability and the relatively known carbon chemistry, nanodiamonds are becoming a key player in modern technologies. This brief review will highlight some of the recent advances of FNDs with an emphasis on nanophotonics.

  1. Study of nanocrystals in the dynamic slip zone

    NASA Astrophysics Data System (ADS)

    Sobolev, G. A.; Kireenkova, S. M.; Morozov, Yu. A.; Smul'skaya, A. I.; Vettegren, V. I.; Kulik, V. B.; Mamalimov, R. I.

    2012-09-01

    Mineral composition is studied and a search to detect nanocrystals is conducted in the surface layers of slickensides formed due to dynamic slip in arkose sandstone. The infrared and Raman spectroscopy show that the slickensided layer is composed of nanocrystals of montmorillonite and anatase measuring ≈15 nm and 3 nm, respectively. The crystalline lattice of the nanocrystals of montmorillonite is stretched by ≈2.5% while the lattice of the nanocrystals of anatase is compressed by ≈0.12%. Deeper than 3 mm below the slickenside surface, the sandstone contains nanocrystals of montmorillonite, beidellite and nontronite, quartz, plagioclase, and anatase. The nanocrystals of anatase have a linear size of ≈8 nm. Their crystalline lattice is compressed by ≈0.03%. It is supposed that montmorillonite in the slickensides was formed due to hydrolytic decomposition of silicates under friction of the fault planes sliding past each other.

  2. Diamond Electronic Devices

    NASA Astrophysics Data System (ADS)

    Isberg, J.

    2010-11-01

    For high-power and high-voltage applications, silicon is by far the dominant semiconductor material. However, silicon has many limitations, e.g. a relatively low thermal conductivity, electric breakdown occurs at relatively low fields and the bandgap is 1.1 eV which effectively limits operation to temperatures below 175° C. Wide-bandgap materials, such as silicon carbide (SiC), gallium nitride (GaN) and diamond offer the potential to overcome both the temperature and power handling limitations of silicon. Diamond is the most extreme in this class of materials. By the fundamental material properties alone, diamond offers the largest benefits as a semiconductor material for power electronic applications. On the other hand, diamond has a problem with a large carrier activation energy of available dopants which necessitates specialised device concepts to allow room temperature (RT) operation. In addition, the role of common defects on the charge transport properties of diamond is poorly understood. Notwithstanding this, many proof-of-principle two-terminal and three-terminal devices have been made and tested. Two-terminal electronic diamond devices described in the literature include: p-n diodes, p-i-n diodes, various types of radiation detectors, Schottky diodes and photoconductive or electron beam triggered switches. Three terminal devices include e.g. MISFETs and JFETs. However, the development of diamond devices poses great challenges for the future. A particularly interesting way to overcome the doping problem, for which there has been some recent progress, is to make so-called delta doped (or pulse-doped) devices. Such devices utilise very thin (˜1 nm) doped layers in order to achieve high RT activation.

  3. Observation of Diamond Nitrogen-Vacancy Center Photoluminescence under High Vacuum in a Magneto-Gravitational Trap

    NASA Astrophysics Data System (ADS)

    Ji, Peng; Hsu, Jen-Feng; Lewandowski, Charles W.; Dutt, M. V. Gurudev; D'Urso, Brian

    2016-05-01

    We report the observation of photoluminescence from nitrogen-vacancy (NV) centers in diamond nanocrystals levitated in a magneto-gravitational trap. The trap utilizes a combination of strong magnetic field gradients and gravity to confine diamagnetic particles in three dimensions. The well-characterized NV centers in trapped diamond nanocrystals provide an ideal built-in sensor to measure the trap magnetic field and the temperature of the trapped diamond nanocrystal. In the future, the NV center spin state could be coupled to the mechanical motion through magnetic field gradients, enabling in an ideal quantum interface between NV center spin and the mechanical motion. National Science Foundation, Grant No. 1540879.

  4. Analysis of Short and Long Range Atomic Order in Nanocrystalline Diamonds with Application of Powder Diffractometry

    NASA Technical Reports Server (NTRS)

    Palosz, B.; Grzanka, E.; Stelmakh, S.; Pielaszek, R.; Bismayer, U.; Neuefiend, J.; Weber, H.-P.; Proffen, T.; VonDreele, R.; Palosz, W.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    Fundamental limitations, with respect to nanocrystalline materials, of the traditional elaboration of powder diffraction data like the Rietveld method are discussed. A tentative method of the analysis of powder diffraction patterns of nanocrystals is introduced which is based on the examination of the variation of lattice parameters calculated from individual Bragg lines (named the "apparent lattice parameter", alp). We examine the application of our methodology using theoretical diffraction patterns computed for models of nanocrystals with a perfect crystal lattice and for grains with a two-phase, core-shell structure. We use the method for the analysis of X-ray and neutron experimental diffraction data of nanocrystalline diamond powders of 4, 6 and 12 nm in diameter. The effects of an internal pressure and strain at the grain surface is discussed. This is based on the dependence of the alp values oil the diffraction vector Q and on the PDF analysis. It is shown, that the experimental results support well the concept of the two-phase structure of nanocrystalline diamond.

  5. Nanocrystal assembly for tandem catalysis

    DOEpatents

    Yang, Peidong; Somorjai, Gabor; Yamada, Yusuke; Tsung, Chia-Kuang; Huang, Wenyu

    2014-10-14

    The present invention provides a nanocrystal tandem catalyst comprising at least two metal-metal oxide interfaces for the catalysis of sequential reactions. One embodiment utilizes a nanocrystal bilayer structure formed by assembling sub-10 nm platinum and cerium oxide nanocube monolayers on a silica substrate. The two distinct metal-metal oxide interfaces, CeO.sub.2--Pt and Pt--SiO.sub.2, can be used to catalyze two distinct sequential reactions. The CeO.sub.2--Pt interface catalyzed methanol decomposition to produce CO and H.sub.2, which were then subsequently used for ethylene hydroformylation catalyzed by the nearby Pt--SiO.sub.2 interface. Consequently, propanal was selectively produced on this nanocrystal bilayer tandem catalyst.

  6. Diamond Coatings

    NASA Technical Reports Server (NTRS)

    1990-01-01

    Advances in materials technology have demonstrated that it is possible to get the advantages of diamond in a number of applications without the cost penalty, by coating and chemically bonding an inexpensive substrate with a thin film of diamond-like carbon (DLC). Diamond films offer tremendous technical and economic potential in such advances as chemically inert protective coatings; machine tools and parts capable of resisting wear 10 times longer; ball bearings and metal cutting tools; a broad variety of optical instruments and systems; and consumer products. Among the American companies engaged in DLC commercialization is Diamonex, Inc., a diamond coating spinoff of Air Products and Chemicals, Inc. Along with its own proprietary technology for both polycrystalline diamond and DLC coatings, Diamonex is using, under an exclusive license, NASA technology for depositing DLC on a substrate. Diamonex is developing, and offering commercially, under the trade name Diamond Aegis, a line of polycrystalline diamond-coated products that can be custom tailored for optical, electronic and engineering applications. Diamonex's initial focus is on optical products and the first commercial product is expected in late 1990. Other target applications include electronic heat sink substrates, x-ray lithography masks, metal cutting tools and bearings.

  7. Industrial diamond

    USGS Publications Warehouse

    Olson, D.W.

    2007-01-01

    World production of natural and synthetic industrial diamond was about 648 million carats in 2006, with 79 percent of the production coming from Ireland, Japan, Russia, South Africa, and the U.S. U.S. consumption was was an estimated 602 million carats, imports were over 391 million carats, and exports were about 83 million carats. About 87 percent of the industrial diamonds market uses synthetic diamonds, which are expected to become less expensive as technology improves and competition from low-cost producers increases.

  8. Photochemical functionalization of diamond surfaces

    NASA Astrophysics Data System (ADS)

    Nichols, Beth Marie

    Diamond surfaces are excellent substrates for potential applications in fields such as biotechnology, molecular sensing, and molecular electronics. In order to develop new diamond-based technologies, it is important to develop a fundamental understanding of diamond surface chemistry. Previous work in the Hamers group has demonstrated covalent functionalization of hydrogen-terminated diamond surfaces with molecules bearing a terminal vinyl group via a photochemical process using sub-bandgap light at 254 nm. While the reaction was shown to occur reproducibly with self-terminating monolayer surface coverage, the mechanism was never fully understood. This thesis investigates the photochemical modification of hydrogen-terminated surfaces of diamond. The results show that this reaction is a surface-mediated radical process initiated by the UV-assisted photoejection of electrons from the diamond surfaces into the liquid phase. To develop a better understanding of the photochemical mechanism, an electrical bias was applied to the diamond samples during the photochemical reaction. Applying a 1 volt potential between two diamond electrodes significantly increases the rate of functionalization of the negative electrode. Cyclic voltammetry and electrochemical impedance measurements show that the applied potential induces downward band-bending within the negative diamond film electrode. At higher voltages a Faradaic current is observed, with no further acceleration of the functionalization rate. The bias-dependent changes in rate are attributed to a field effect; the applied potential induces a downward band-bending on the negative electrode and facilitates electron ejection into the adjacent organic fluid. The ability to directly organically photopattern the surface on length scales of <25 microns has also been demonstrated using simple photomasking techniques. Techniques for the functionalization of diamond may be applied to other 'unreactive' surfaces. The activation of a

  9. Industrial diamond

    USGS Publications Warehouse

    Olson, D.W.

    2004-01-01

    Part of the 2003 industrial minerals review. Supply and demand data for industrial diamond are provided. Topics discussed are consumption, prices, imports and exports, government stockpiles, and the outlook for 2004.

  10. Patterning nanocrystals using DNA

    NASA Astrophysics Data System (ADS)

    Williams, Shara Carol

    One of the goals of nanotechnology is to enable programmed self-assembly of patterns made of various materials with nanometer-sized control. This dissertation describes the results of experiments templating arrangements of gold and semiconductor nanocrystals using 2'-deoxyribonucleic acid (DNA). Previously, simple DNA-templated linear arrangements of two and three nanocrystals structures have been made. Here, we have sought to assemble larger and more complex nanostructures. Cold-DNA conjugates with 50 to 100 bases self-assembled into planned arrangements using strands of DNA containing complementary base sequences. We used two methods to increase the complexity of the arrangements: using branched synthetic doublers within the DNA covalent backbone to create discrete nanocrystal groupings, and incorporating the nanocrystals into a previously developed DNA lattice structure that self-assembles from tiles made of DNA double-crossover molecules to create ordered nanoparticle arrays. In the first project, the introduction of a covalently-branched synthetic doubler reagent into the backbone of DNA strands created a branched DNA "trimer." This DNA trimer templated various structures that contained groupings of three and four gold nanoparticles, giving promising, but inconclusive transmission electron microscopy (TEM) results. Due to the presence of a variety of possible structures in the reaction mixtures, and due to the difficulty of isolating the desired structures, the TEM and gel electrophoresis results for larger structures having four particles, and for structures containing both 5 and 10 nm gold nanoparticles were inconclusive. Better results may come from using optical detection methods, or from improved sample preparation. In the second project, we worked toward making two-dimensional ordered arrays of nanocrystals. We replicated and improved upon previous results for making DNA lattices, increasing the size of the lattices to a length greater than 20 mum, and

  11. Patterning nanocrystals using DNA

    SciTech Connect

    Williams, Shara Carol

    2003-01-01

    One of the goals of nanotechnology is to enable programmed self-assembly of patterns made of various materials with nanometer-sized control. This dissertation describes the results of experiments templating arrangements of gold and semiconductor nanocrystals using 2'-deoxyribonucleic acid (DNA). Previously, simple DNA-templated linear arrangements of two and three nanocrystals structures have been made.[1] Here, we have sought to assemble larger and more complex nanostructures. Gold-DNA conjugates with 50 to 100 bases self-assembled into planned arrangements using strands of DNA containing complementary base sequences. We used two methods to increase the complexity of the arrangements: using branched synthetic doublers within the DNA covalent backbone to create discrete nanocrystal groupings, and incorporating the nanocrystals into a previously developed DNA lattice structure [2][3] that self-assembles from tiles made of DNA double-crossover molecules to create ordered nanoparticle arrays. In the first project, the introduction of a covalently-branched synthetic doubler reagent into the backbone of DNA strands created a branched DNA ''trimer.'' This DNA trimer templated various structures that contained groupings of three and four gold nanoparticles, giving promising, but inconclusive transmission electron microscopy (TEM) results. Due to the presence of a variety of possible structures in the reaction mixtures, and due to the difficulty of isolating the desired structures, the TEM and gel electrophoresis results for larger structures having four particles, and for structures containing both 5 and 10 nm gold nanoparticles were inconclusive. Better results may come from using optical detection methods, or from improved sample preparation. In the second project, we worked toward making two-dimensional ordered arrays of nanocrystals. We replicated and improved upon previous results for making DNA lattices, increasing the size of the lattices to a length greater than

  12. Diamond fiber field emitters

    DOEpatents

    Blanchet-Fincher, Graciela B.; Coates, Don M.; Devlin, David J.; Eaton, David F.; Silzars, Aris K.; Valone, Steven M.

    1996-01-01

    A field emission electron emitter comprising an electrode formed of at least one diamond, diamond-like carbon or glassy carbon composite fiber, said composite fiber having a non-diamond core and a diamond, diamond-like carbon or glassy carbon coating on said non-diamond core, and electronic devices employing such a field emission electron emitter.

  13. Nanotwinned diamond with unprecedented hardness and stability.

    PubMed

    Huang, Quan; Yu, Dongli; Xu, Bo; Hu, Wentao; Ma, Yanming; Wang, Yanbin; Zhao, Zhisheng; Wen, Bin; He, Julong; Liu, Zhongyuan; Tian, Yongjun

    2014-06-12

    Although diamond is the hardest material for cutting tools, poor thermal stability has limited its applications, especially at high temperatures. Simultaneous improvement of the hardness and thermal stability of diamond has long been desirable. According to the Hall-Petch effect, the hardness of diamond can be enhanced by nanostructuring (by means of nanograined and nanotwinned microstructures), as shown in previous studies. However, for well-sintered nanograined diamonds, the grain sizes are technically limited to 10-30 nm (ref. 3), with degraded thermal stability compared with that of natural diamond. Recent success in synthesizing nanotwinned cubic boron nitride (nt-cBN) with a twin thickness down to ∼3.8 nm makes it feasible to simultaneously achieve smaller nanosize, ultrahardness and superior thermal stability. At present, nanotwinned diamond (nt-diamond) has not been fabricated successfully through direct conversions of various carbon precursors (such as graphite, amorphous carbon, glassy carbon and C60). Here we report the direct synthesis of nt-diamond with an average twin thickness of ∼5 nm, using a precursor of onion carbon nanoparticles at high pressure and high temperature, and the observation of a new monoclinic crystalline form of diamond coexisting with nt-diamond. The pure synthetic bulk nt-diamond material shows unprecedented hardness and thermal stability, with Vickers hardness up to ∼200 GPa and an in-air oxidization temperature more than 200 °C higher than that of natural diamond. The creation of nanotwinned microstructures offers a general pathway for manufacturing new advanced carbon-based materials with exceptional thermal stability and mechanical properties.

  14. High temperature diamond film deposition on a natural diamond anvil

    SciTech Connect

    McCauley, T.S.; Vohra, Y.K.

    1995-12-31

    We report on the growth and characterization of a 100 {mu}m thick by 350 {mu}m diameter diamond layer on the culet of a type Ia brilliant cut natural diamond anvil by microwave plasma-assisted CVD (MPCVD). While our previous work [1] on diamond anvils resulted in homoepitaxial film growth at a rate of approximately 20 {mu}m/hr, the present 100 {mu}m thick diamond layer grew in less than 2 hours. This unprecedented growth rate of {approximately} 50 {mu}m/hr is believed to be the result of the extremely high substrate temperature (1800{degrees}-2100{degrees}C) during deposition. The translucent diamond layer was characterized by micro-Raman, low temperature photoluminescence (PL) and PL excitation spectroscopy, as well as atomic force microscopy (AFM). Raman analysis shows the deposit to be of high quality. The PL spectra show numerous features, including prominent emission bands at 575 nm (2.16 eV), 636 nm (1.95 eV), 735 nm (1.68 eV) and 777 run, (1.60 eV).

  15. Structural and optical manipulation of colloidal Ge1-xSnx nanocrystals with experimentally synthesized sizes: Atomistic tight-binding theory

    NASA Astrophysics Data System (ADS)

    Sukkabot, Worasak

    2017-02-01

    Nontoxic, maintainable and cost-effective group IV semiconductors are gorgeous for an expansive range of electronic and optoelectronic applications, even though the presence of the indirect band gap obstructs the optical performance. However, band structures can be modified from indirect to direct band gaps by constructing the nanostructures or by alloying with tin (Sn) material. In the study presented here, I investigate the impact of ion-centred types, Sn compositions and dimensions on the electronic structures and optical properties in Ge1-xSnx diamond cubic nanocrystals of the experimentally synthesized Sn contents and diameters using the atomistic tight-binding theory (TB) in the conjunction with the configuration interaction description (CI). The analysis of the mechanism suggests that the physical properties are mainly sensitive with ion-centred types (anion (a) and cation (c)), Sn compositions and dimensions of Ge1-xSnx diamond cubic nanocrystals. The reduction of optical band gaps is reported with the increasing diameters and Sn alloying contents. The visible spectral range is obtained allowing for the applications in bio imaging and chemical sensing. The optical band gaps based on tight-binding calculations are in close agreement with the experimental data for Ge1-xSnx nanocrystals with diameter of 2.1 nm, while for Ge1-xSnx nanocrystals with diameter of 2.7 nm there is a discrepancy of 0.4 eV with experimental results and first-principles calculations. An improvement in the luminescence properties of such Ge1-xSnx nanocrystals becomes possible in the presence of the Sn contents. The electron-hole coulomb interaction is reduced with the increasing Sn components, while the electron-hole exchange interaction is increased with the increasing Sn contents. In addition, I have to point out an astonishing phenomenon, stokes shift and fine structure splitting, with the aim for the realization of the entangled source. The stokes shift and fine structure splitting

  16. Solar induced growth of silver nanocrystals

    NASA Astrophysics Data System (ADS)

    Thøgersen, Annett; Muntingh, Georg

    2013-04-01

    The effect of solar irradiation on plasmonic silver nanocrystals has been investigated using transmission electron microscopy and size distribution analysis, in the context of solar cell applications for light harvesting. Starting from an initial collection of spherical nanocrystals on a carbon film whose sizes are log-normally distributed, solar irradiation causes the nanocrystals to grow, with one particle reaching a diameter of 638 nm after four hours of irradiation. In addition some of the larger particles lose their spherical shape. The average nanocrystal diameter was found to grow as predicted by the Ostwald ripening model, taking into account the range of area fractions of the samples. The size distribution stays approximately log-normal and does not reach one of the steady-state size distributions predicted by the Ostwald ripening model. This might be explained by the system being in a transient state.

  17. Exciton polarizability in semiconductor nanocrystals.

    PubMed

    Wang, Feng; Shan, Jie; Islam, Mohammad A; Herman, Irving P; Bonn, Mischa; Heinz, Tony F

    2006-11-01

    The response of charge to externally applied electric fields is an important basic property of any material system, as well as one critical for many applications. Here, we examine the behaviour and dynamics of charges fully confined on the nanometre length scale. This is accomplished using CdSe nanocrystals of controlled radius (1-2.5 nm) as prototype quantum systems. Individual electron-hole pairs are created at room temperature within these structures by photoexcitation and are probed by terahertz (THz) electromagnetic pulses. The electronic response is found to be instantaneous even for THz frequencies, in contrast to the behaviour reported in related measurements for larger nanocrystals and nanocrystal assemblies. The measured polarizability of an electron-hole pair (exciton) amounts to approximately 10(4) A(3) and scales approximately as the fourth power of the nanocrystal radius. This size dependence and the instantaneous response reflect the presence of well-separated electronic energy levels induced in the system by strong quantum-confinement effects.

  18. "Nanocrystal bilayer for tandem catalysis"

    SciTech Connect

    Yamada, Yusuke; Tsung, Chia Kuang; Huang, Wenyu; Huo, Ziyang; E.Habas, Susan E; Soejima, Tetsuro; Aliaga, Cesar E; Samorjai, Gabor A; Yang, Peidong

    2011-01-24

    Supported catalysts are widely used in industry and can be optimized by tuning the composition and interface of the metal nanoparticles and oxide supports. Rational design of metal-metal oxide interfaces in nanostructured catalysts is critical to achieve better reaction activities and selectivities. We introduce here a new class of nanocrystal tandem catalysts that have multiple metal-metal oxide interfaces for the catalysis of sequential reactions. We utilized a nanocrystal bilayer structure formed by assembling platinum and cerium oxide nanocube monolayers of less than 10 nm on a silica substrate. The two distinct metal-metal oxide interfaces, CeO2-Pt and Pt-SiO2, can be used to catalyse two distinct sequential reactions. The CeO2-Pt interface catalysed methanol decomposition to produce CO and H2, which were subsequently used for ethylene hydroformylation catalysed by the nearby Pt-SiO2 interface. Consequently, propanal was produced selectively from methanol and ethylene on the nanocrystal bilayer tandem catalyst. This new concept of nanocrystal tandem catalysis represents a powerful approach towards designing high-performance, multifunctional nanostructured catalysts

  19. Mechanism of the electrophoretic assembly of cadmium selenide nanocrystal films and their mechanical properties

    NASA Astrophysics Data System (ADS)

    Jia, Shengguo

    This thesis consists of two closely related experimental studies of electrophoretically deposited CdSe nanocrystal films. In the first part of this thesis, the charging of CdSe nanocrystal in non-aqueous solvent and the mechanism of electrophoretic deposition (EPD) are discussed from the point of view of the influence of the nanocrystal surface. Our experiments show that the charge of these nanocrystals originates from the surface defects of the nanocrystal. EPD leads to equally thick films of CdSe nanocrystals on both positive and negative electrodes due to the deposition of equal numbers of negatively and positively charged nanocrystals, even though their concentrations are not equal in solution. The deposition stops when the charged nanocrystals with lower concentration are depleted. The second part of this thesis focuses on the mechanical and optical properties of these electrophoretically deposited CdSe nanocrystal films. Approaches to measure and analyze the mechanical parameters and fracture properties of electrophoretically deposited CdSe nanocrystal films are described in this part. The values of the elastic modulus of electrophoretically deposited CdSe nanocrystal films composed of 3.2 nm diameter nanocrystals measured by Raman microprobe scattering (˜9.7 GPa) and nanoindentation (˜10 GPa) match each other. The mechanical response of nanocrystal films suggests polymeric features that are attributable to the organic ligand on the nanocrystal cores. After nanocrystal cross-linking and partial ligand removal, the nanocrystal films exhibit more features of granularity. The fracture, strain, and stress of electrophoretically deposited CdSe nanocrystal films are studied as a function of the film thickness, nanocrystal size, and drying method. In addition to Raman microprobe scattering, optical methods such as photoluminescence, high-spatial resolution infrared spectroscopy, and ellipsometry are used to investigate the properties of these electrophoretically

  20. Mo2C coating on diamond: Different effects on thermal conductivity of diamond/Al and diamond/Cu composites

    NASA Astrophysics Data System (ADS)

    Ma, Songdi; Zhao, Naiqin; Shi, Chunsheng; Liu, Enzuo; He, Chunnian; He, Fang; Ma, Liying

    2017-04-01

    Mo2C submicron layer coated diamond particles prepared by a molten salts route with Mo powder as the starting material were used as the filler in Cu- and Al- matrix composites. The microstructure and thermal property of the composites prepared by a vacuum pressure infiltration method were investigated. When introducing a 500 nm thick Mo2C layer, the thermal conductivity of the composites with different matrix presented different performance. A high thermal conductivity (657 W m-1 K-1) was obtained in diamond/Cu composites owing to the improved interfacial bonding and lower interfacial thermal resistance, while the thermal conductivity of diamond/Al composites decreased from 553 W m-1 K-1 to 218 W m-1 K-1 when introducing the Mo2C layer, which can be attributed to the formation of harmful granule-phase (Al12Mo) at the interface of diamond and aluminum. This work provides a promising approach to improve performance of diamond reinforced metal matrix composites by selecting carbide as an interface modifier.

  1. Optical properties of cadmium sulfide nanocrystals obtained by the sol-gel method in gelatin

    NASA Astrophysics Data System (ADS)

    Skobeeva, V. M.; Smyntyna, V. A.; Sviridova, O. I.; Struts, D. A.; Tyurin, A. V.

    2008-07-01

    Based on analysis of optical absorption data for CdS nanocrystals obtained by sol-gel technology in gelatin, we have studied the effect of technological factors (reagent concentrations, gelatin concentration) on the growth process and size distribution of the synthesized nanocrystals. Depending on the reagent concentration, we synthesized CdS nanocrystals with mean radii in the range bar r = 1.9 - 2.4 nm . We have shown that for a low gelatin content (1%), nanocrystals of different sizes are formed (1.7 nm and 2.6 nm). With an increase in the gelatin concentration, the size dispersion decreases and nanocrystals of a single mean radius (2.3 nm) are formed. We have established a correlation between the size dispersion and the shape of the photoluminescence spectrum of the CdS nanocrystals.

  2. Characteristics of Impact Diamonds

    NASA Astrophysics Data System (ADS)

    Skala, R.; Bouska, V. J.

    1992-07-01

    Having studied two Czech diamonds in UV light (lambda=366 nm) they appeared to be an extraordinary dirty orange color [1], the same as in the case of Popigai and ureilites impact diamonds (ID) [2]. SEM images show evidence of a thatch-like surface that is very similar to that of the Abee chondrite [3]. Commonly, the ID contain microscopic black plates which are formed by graphite or a carbon matter with indefinite structure, and they are always associated with hexagonal moissanite [2,4]. One unexplained fact is connected with a fabric of the ID aggregates, i.e. both Czech diamonds are single crystals, otherwise other ID form polycrystalline strongly textured aggregates. [1] Bouska V.J. and Skala R.M. (1992) Abstracts for International Conference on Large Meteorite Impacts and Planetary Evolution, in press. [2] Masaitis V.L., Shafranovskii G.I., Ezerskii V.A., and Reshetnyak N.B. (1990) Meteoritica 49, 180-196. [3] Russell S.S. and Pillinger C.T. (1991) Abstracts 54th Ann. Meet. Meteor. Soc. 200. [4] Bauer J., Fiala J., and Hrichova R. (1963) Amer. Mineral. 48, 620-634.

  3. Application of Powder Diffraction Methods to the Analysis of Short- and Long-Range Atomic Order in Nanocrystalline Diamond and SiC: The Concept of the Apparent Lattice Parameter (alp)

    NASA Technical Reports Server (NTRS)

    Palosz, B.; Grzanka, E.; Gierlotka, S.; Stelmakh, S.; Pielaszek, R.; Bismayer, U.; Weber, H.-P.; Palosz, W.

    2003-01-01

    Two methods of the analysis of powder diffraction patterns of diamond and SiC nanocrystals are presented: (a) examination of changes of the lattice parameters with diffraction vector Q ('apparent lattice parameter', alp) which refers to Bragg scattering, and (b), examination of changes of inter-atomic distances based on the analysis of the atomic Pair Distribution Function, PDF. Application of these methods was studied based on the theoretical diffraction patterns computed for models of nanocrystals having (i) a perfect crystal lattice, and (ii), a core-shell structure, i.e. constituting a two-phase system. The models are defined by the lattice parameter of the grain core, thickness of the surface shell, and the magnitude and distribution of the strain field in the shell. X-ray and neutron experimental diffraction data of nanocrystalline SiC and diamond powders of the grain diameter from 4 nm up to micrometers were used. The effects of the internal pressure and strain at the grain surface on the structure are discussed based on the experimentally determined dependence of the alp values on the Q-vector, and changes of the interatomic distances with the grain size determined experimentally by the atomic Pair Distribution Function (PDF) analysis. The experimental results lend a strong support to the concept of a two-phase, core and the surface shell structure of nanocrystalline diamond and SiC.

  4. Application of Powder Diffraction Methods to the Analysis of the Atomic Structure of Nanocrystals: The Concept of the Apparent Lattice Parameter (ALP)

    NASA Technical Reports Server (NTRS)

    Palosz, B.; Grzanka, E.; Gierlotka, S.; Stelmakh, S.; Pielaszek, R.; Bismayer, U.; Weber, H.-P.; Palosz, W.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    The applicability of standard methods of elaboration of powder diffraction data for determination of the structure of nano-size crystallites is analysed. Based on our theoretical calculations of powder diffraction data we show, that the assumption of the infinite crystal lattice for nanocrystals smaller than 20 nm in size is not justified. Application of conventional tools developed for elaboration of powder diffraction data, like the Rietveld method, may lead to erroneous interpretation of the experimental results. An alternate evaluation of diffraction data of nanoparticles, based on the so-called 'apparent lattice parameter' (alp) is introduced. We assume a model of nanocrystal having a grain core with well-defined crystal structure, surrounded by a surface shell with the atomic structure similar to that of the core but being under a strain (compressive or tensile). The two structural components, the core and the shell, form essentially a composite crystal with interfering, inseparable diffraction properties. Because the structure of such a nanocrystal is not uniform, it defies the basic definitions of an unambiguous crystallographic phase. Consequently, a set of lattice parameters used for characterization of simple crystal phases is insufficient for a proper description of the complex structure of nanocrystals. We developed a method of evaluation of powder diffraction data of nanocrystals, which refers to a core-shell model and is based on the 'apparent lattice parameter' methodology. For a given diffraction pattem, the alp values are calculated for every individual Bragg reflection. For nanocrystals the alp values depend on the diffraction vector Q. By modeling different a0tomic structures of nanocrystals and calculating theoretically corresponding diffraction patterns using the Debye functions we showed, that alp-Q plots show characteristic shapes which can be used for evaluation of the atomic structure of the core-shell system. We show, that using a simple

  5. Diamond Tours

    NASA Technical Reports Server (NTRS)

    2007-01-01

    On April 24, a group traveling with Diamond Tours visited StenniSphere, the visitor center at NASA John C. Stennis Space Center in South Mississippi. The trip marked Diamond Tours' return to StenniSphere since Hurricane Katrina struck the Gulf Coast on Aug. 29, 2005. About 25 business professionals from Georgia enjoyed the day's tour of America's largest rocket engine test complex, along with the many displays and exhibits at the museum. Before Hurricane Katrina, the nationwide company brought more than 1,000 visitors to StenniSphere each month. That contributed to more than 100,000 visitors from around the world touring the space center each year. In past years StenniSphere's visitor relations specialists booked Diamond Tours two or three times a week, averaging 40 to 50 people per visit. SSC was established in the 1960s to test the huge engines for the Saturn V moon rockets. Now 40 years later, the center tests every main engine for the space shuttle. SSC will soon begin testing the rocket engines that will power spacecraft carrying Americans back to the moon and on to Mars. For more information or to book a tour, visit http://www.nasa.gov/centers/stennis/home/index.html and click on the StenniSphere logo; or call 800-237-1821 or 228-688-2370.

  6. Surface chemical modification of nanocrystals

    DOEpatents

    Helms, Brett Anthony; Milliron, Delia Jane; Rosen, Evelyn Louise; Buonsanti, Raffaella; Llordes, Anna

    2017-03-14

    Nanocrystals comprising organic ligands at surfaces of the plurality of nanocrystals are provided. The organic ligands are removed from the surfaces of the nanocrystals using a solution comprising a trialkyloxonium salt in a polar aprotic solvent. The removal of the organic ligands causes the nanocrystals to become naked nanocrystals with cationic surfaces.

  7. Thick-shell nanocrystal quantum dots

    DOEpatents

    Hollingsworth, Jennifer A.; Chen, Yongfen; Klimov, Victor I.; Htoon, Han; Vela, Javier

    2011-05-03

    Colloidal nanocrystal quantum dots comprising an inner core having an average diameter of at least 1.5 nm and an outer shell, where said outer shell comprises multiple monolayers, wherein at least 30% of the quantum dots have an on-time fraction of 0.80 or greater under continuous excitation conditions for a period of time of at least 10 minutes.

  8. Size control and quantum confinement in Cu2ZnSnS4 nanocrystals.

    PubMed

    Khare, Ankur; Wills, Andrew W; Ammerman, Lauren M; Norris, David J; Aydil, Eray S

    2011-11-14

    Starting with metal dithiocarbamate complexes, we synthesize colloidal Cu(2)ZnSnS(4) (CZTS) nanocrystals with diameters ranging from 2 to 7 nm. Structural and Raman scattering data confirm that CZTS is obtained rather than other possible material phases. The optical absorption spectra of nanocrystals with diameters less than 3 nm show a shift to higher energy due to quantum confinement.

  9. Track membranes with embedded semiconductor nanocrystals: structural and optical examinations

    NASA Astrophysics Data System (ADS)

    Orlova, A. O.; Gromova, Yu A.; Savelyeva, A. V.; Maslov, V. G.; Artemyev, M. V.; Prudnikau, A.; Fedorov, A. V.; Baranov, A. V.

    2011-11-01

    We studied the optical properties of poly(ethylene terephthalate) ion track membranes of 1.5, 0.5 and 0.05 µm pores impregnated with luminescent semiconductor CdSe/ZnS nanocrystals of different diameters (2.5 and 5 nm). The nanocrystals were embedded from their colloidal solutions in toluene by the immersion of a membrane in a colloidal solution. Localization of quasi-isolated weakly interacting CdSe/ZnS nanocrystals in a loosened layer on the track pore wall surface along with the existence of empty pores was demonstrated. We observed also the spatial separation of nanocrystals of 2.5 and 5 nm in size along the 50 nm pores.

  10. Research of fluorescent spectra of oleic acid-stabilized ZnSe nanocrystals based on UV light modification

    NASA Astrophysics Data System (ADS)

    Hao, Licai; Bai, Zhongchen; Huang, Zhaoliang; Liao, Sha; Zhang, Zhengping

    2016-11-01

    The non-aqueous synthesized and post-preparative treatment of oleic acid (OA)-stabilized ZnSe nanocrystals were studied systematically. ZnSe nanocrystals were successfully synthesized via paraffin liquid and oleic acid system by using OA as stabilizer. Synthesized nanocrystals were characterized by means of absorption and fluorescent spectra, Fourier transform infrared spectrometer, transmission electron microscopy and selected area electron diffraction. Furthermore, solutions of ZnSe nanocrystals were illuminated with UV light. The experimental results showed that the fluorescent peak was red-shifted from 445 to 510 nm. The results suggested that, when the solution under illumination, OA was removed from the surface of ZnSe nanocrystals and the surface of ZnSe nanocrystals was oxidized to ZnO nanocrystals. ZnSe/ZnO core/shell nanocrystals were formed when the solution of ZnSe nanocrystals illuminated with UV light.

  11. Surface-Driven Magnetotransport in Perovskite Nanocrystals.

    PubMed

    Thi N'Goc, Ha Le; Mouafo, Louis Donald Notemgnou; Etrillard, Céline; Torres-Pardo, Almudena; Dayen, Jean-François; Rano, Simon; Rousse, Gwenaëlle; Laberty-Robert, Christel; Calbet, Jose Gonzales; Drillon, Marc; Sanchez, Clément; Doudin, Bernard; Portehault, David

    2017-03-01

    Unique insights into magnetotransport in 20 nm ligand-free La0.67 Sr0.33 MnO3 perovskite nanocrystals of nearly perfect crystalline quality reveal a chemically altered 0.8 nm thick surface layer that triggers exceptionally large magnetoresistance at low temperature, independently of the spin polarization of the ferromagnetic core. This discovery shows how the nanoscale impacts magnetotransport in a material widely spread as electrode in hybrid spintronic devices.

  12. Diamonds in an Archean greenstone belt: Diamond suites in unconventional rocks of Wawa, Northern Ontario (Canada)

    NASA Astrophysics Data System (ADS)

    Kopylova, Maya; Bruce, Loryn; Ryder, John

    2010-05-01

    population. Diamonds from the conglomerate have nitrogen contents below 400 ppm N, with 47% of the suite being Type IaA stones. Approximately one third of the conglomerate and breccia diamonds belongs to Type II having no measurable N. The two suites of Wawa diamonds, according to the morphology and nitrogen studies, are deemed to be different. The conglomerate diamonds are significantly less resorbed and contain less aggregated N. The diamonds that occur in the Wawa breccia and conglomerate have different primary volcanic sources. We suggest that the primary volcanic rock of the conglomerate diamonds may be a kimberlite, as kimberlitic indicator minerals are found in the matrix of the conglomerate. These indicator minerals garnet, Cr diopside and ilmenite are absent from the diamoniferous lamprophyric breccias. The hypothetical kimberlites may have occured in proximity to the conglomerates as suggested by low mechanical abrasion of the conglomerate diamonds and indicator minerals, and the preservation of garnet kelyphitic rims and Cr-diopside. Our study infers an episode of the Archean, pre-2.7 Ga kimberlite magmatism in MGB, which also experienced multiple emplacement episodes of the 2.7 Ga syn-orogenic diamondiferous calc-alkaline lamprophyres. Despite the distinct origins of the breccia and conglomerate diamonds, they all have similar red-orange-green cathodoluminescence colours controlled by the CL emission mainly at 520 nm. This contrasts with the prevalent CL emission at 415-440 nm commonly observed in kimberlitic and detrital diamonds. We ascribe the red-orange-green CL colours of the two diamond suites of Wawa to the late imprint of metamorphism.

  13. Ion-beam-assisted etching of diamond

    NASA Technical Reports Server (NTRS)

    Efremow, N. N.; Geis, M. W.; Flanders, D. C.; Lincoln, G. A.; Economou, N. P.

    1985-01-01

    The high thermal conductivity, low RF loss, and inertness of diamond make it useful in traveling wave tubes operating in excess of 500 GHz. Such use requires the controlled etching of type IIA diamond to produce grating like structures tens of micrometers deep. Previous work on reactive ion etching with O2 gave etching rates on the order of 20 nm/min and poor etch selectivity between the masking material (Ni or Cr) and the diamond. An alternative approach which uses a Xe(+) beam and a reactive gas flux of NO2 in an ion-beam-assisted etching system is reported. An etching rate of 200 nm/min was obtained with an etching rate ratio of 20 between the diamond and an aluminum mask.

  14. Nanocrystal doped matrixes

    DOEpatents

    Parce, J. Wallace; Bernatis, Paul; Dubrow, Robert; Freeman, William P.; Gamoras, Joel; Kan, Shihai; Meisel, Andreas; Qian, Baixin; Whiteford, Jeffery A.; Ziebarth, Jonathan

    2010-01-12

    Matrixes doped with semiconductor nanocrystals are provided. In certain embodiments, the semiconductor nanocrystals have a size and composition such that they absorb or emit light at particular wavelengths. The nanocrystals can comprise ligands that allow for mixing with various matrix materials, including polymers, such that a minimal portion of light is scattered by the matrixes. The matrixes of the present invention can also be utilized in refractive index matching applications. In other embodiments, semiconductor nanocrystals are embedded within matrixes to form a nanocrystal density gradient, thereby creating an effective refractive index gradient. The matrixes of the present invention can also be used as filters and antireflective coatings on optical devices and as down-converting layers. Processes for producing matrixes comprising semiconductor nanocrystals are also provided. Nanostructures having high quantum efficiency, small size, and/or a narrow size distribution are also described, as are methods of producing indium phosphide nanostructures and core-shell nanostructures with Group II-VI shells.

  15. Doped semiconductor nanocrystal based fluorescent cellular imaging probes

    NASA Astrophysics Data System (ADS)

    Maity, Amit Ranjan; Palmal, Sharbari; Basiruddin, Sk; Karan, Niladri Sekhar; Sarkar, Suresh; Pradhan, Narayan; Jana, Nikhil R.

    2013-05-01

    Doped semiconductor nanocrystals such as Mn doped ZnS, Mn doped ZnSe and Cu doped InZnS, are considered as new classes of fluorescent biological probes with low toxicity. Although the synthesis in high quality of such nanomaterials is now well established, transforming them into functional fluorescent probes remains a challenge. Here we report a fluorescent cellular imaging probe made of high quality doped semiconductor nanocrystals. We have identified two different coating approaches suitable for transforming the as synthesized hydrophobic doped semiconductor nanocrystals into water-soluble functional nanoparticles. Following these approaches we have synthesized TAT-peptide- and folate-functionalized nanoparticles of 10-80 nm hydrodynamic diameter and used them as a fluorescent cell label. The results shows that doped semiconductor nanocrystals can be an attractive alternative for conventional cadmium based quantum dots with low toxicity.Doped semiconductor nanocrystals such as Mn doped ZnS, Mn doped ZnSe and Cu doped InZnS, are considered as new classes of fluorescent biological probes with low toxicity. Although the synthesis in high quality of such nanomaterials is now well established, transforming them into functional fluorescent probes remains a challenge. Here we report a fluorescent cellular imaging probe made of high quality doped semiconductor nanocrystals. We have identified two different coating approaches suitable for transforming the as synthesized hydrophobic doped semiconductor nanocrystals into water-soluble functional nanoparticles. Following these approaches we have synthesized TAT-peptide- and folate-functionalized nanoparticles of 10-80 nm hydrodynamic diameter and used them as a fluorescent cell label. The results shows that doped semiconductor nanocrystals can be an attractive alternative for conventional cadmium based quantum dots with low toxicity. Electronic supplementary information available: Characterization details of coating and

  16. White-light emission from magic-sized cadmium selenide nanocrystals.

    PubMed

    Bowers, Michael J; McBride, James R; Rosenthal, Sandra J

    2005-11-09

    Magic-sized cadmium selenide (CdSe) nanocrystals have been pyrolytically synthesized. These ultra-small nanocrystals exhibit broadband emission (420-710 nm) that covers most of the visible spectrum while not suffering from self absorption. This behavior is a direct result of the extremely narrow size distribution and unusually large Stokes shift (40-50 nm). The intrinsic properties of these ultra-small nanocrystals make them an ideal material for applications in solid state lighting and also the perfect platform to study the molecule-to-nanocrystal transition.

  17. Self-Organized Ultrathin Oxide Nanocrystals

    SciTech Connect

    Huo, Ziyang; Tsung, Chia-kuang; Huang, Wenyu; Fardy, Melissa; Yan, Ruoxue; Li, Yadong; Yang, Piedong; Zhang, Xiaofeng

    2009-01-08

    Sub-2-nm (down to one-unit cell) uniform oxide nanocrystals and highly ordered superstructures were obtained in one step using oleylamine and oleic acid as capping and structure directing agents. The cooperative nature of the nanocrystal growth and assembly resulted in mesoscopic one-dimensional ribbon-like superstructures made of these ultrathin nanocrystals. The process reported here is general and can be readily extended to the production of many other transition metal (TiO2, ZnO, Nb2O5) and rare earth oxide (Eu2O3, Sm2O3, Er2O3, Y2O3, Tb2O3, and Yb2O3) systems.

  18. Antioxidant properties of cerium oxide nanocrystals as a function of nanocrystal diameter and surface coating.

    PubMed

    Lee, Seung Soo; Song, Wensi; Cho, Minjung; Puppala, Hema L; Nguyen, Phuc; Zhu, Huiguang; Segatori, Laura; Colvin, Vicki L

    2013-11-26

    This work examines the effect of nanocrystal diameter and surface coating on the reactivity of cerium oxide nanocrystals with H2O2 both in chemical solutions and in cells. Monodisperse nanocrystals were formed in organic solvents from the decomposition of cerium precursors, and subsequently phase transferred into water using amphiphiles as nanoparticle coatings. Quantitative analysis of the antioxidant capacity of CeO2-x using gas chromatography and a luminol test revealed that 2 mol of H2O2 reacted with every mole of cerium(III), suggesting that the reaction proceeds via a Fenton-type mechanism. Smaller diameter nanocrystals containing more cerium(III) were found to be more reactive toward H2O2. Additionally, the presence of a surface coating did not preclude the reaction between the nanocrystal surface cerium(III) and hydrogen peroxide. Taken together, the most reactive nanoparticles were the smallest (e.g., 3.8 nm diameter) with the thinnest surface coating (e.g., oleic acid). Moreover, a benchmark test of their antioxidant capacity revealed these materials were 9 times more reactive than commercial antioxidants such as Trolox. A unique feature of these antioxidant nanocrystals is that they can be applied multiple times: over weeks, cerium(IV) rich particles slowly return to their starting cerium(III) content. In nearly all cases, the particles remain colloidally stable (e.g., nonaggregated) and could be applied multiple times as antioxidants. These chemical properties were also observed in cell culture, where the materials were able to reduce oxidative stress in human dermal fibroblasts exposed to H2O2 with efficiency comparable to their solution phase reactivity. These data suggest that organic coatings on cerium oxide nanocrystals do not limit the antioxidant behavior of the nanocrystals, and that their redox cycling behavior can be preserved even when stabilized.

  19. Biomineralization: Nanocrystals by design

    NASA Astrophysics Data System (ADS)

    Shang, Li; Nienhaus, Gerd Ulrich

    2015-10-01

    Nanocrystals with precisely defined structures offer promise as components of advanced materials yet they are challenging to create. Now, a nanocrystal made up of seven cadmium and twelve chloride ions has been synthesized via a biotemplating approach that uses a de novo designed protein.

  20. Twinning of cubic diamond explains reported nanodiamond polymorphs

    PubMed Central

    Németh, Péter; Garvie, Laurence A. J.; Buseck, Peter R.

    2015-01-01

    The unusual physical properties and formation conditions attributed to h-, i-, m-, and n-nanodiamond polymorphs has resulted in their receiving much attention in the materials and planetary science literature. Their identification is based on diffraction features that are absent in ordinary cubic (c-) diamond (space group: Fd-3m). We show, using ultra-high-resolution transmission electron microscope (HRTEM) images of natural and synthetic nanodiamonds, that the diffraction features attributed to the reported polymorphs are consistent with c-diamond containing abundant defects. Combinations of {113} reflection and <011> rotation twins produce HRTEM images and d-spacings that match those attributed to h-, i-, and m-diamond. The diagnostic features of n-diamond in TEM images can arise from thickness effects of c-diamonds. Our data and interpretations strongly suggest that the reported nanodiamond polymorphs are in fact twinned c-diamond. We also report a new type of twin (<11> rotational), which can give rise to grains with dodecagonal symmetry. Our results show that twins are widespread in diamond nanocrystals. A high density of twins could strongly influence their applications. PMID:26671288

  1. Twinning of cubic diamond explains reported nanodiamond polymorphs

    NASA Astrophysics Data System (ADS)

    Németh, Péter; Garvie, Laurence A. J.; Buseck, Peter R.

    2015-12-01

    The unusual physical properties and formation conditions attributed to h-, i-, m-, and n-nanodiamond polymorphs has resulted in their receiving much attention in the materials and planetary science literature. Their identification is based on diffraction features that are absent in ordinary cubic (c-) diamond (space group: Fd-3m). We show, using ultra-high-resolution transmission electron microscope (HRTEM) images of natural and synthetic nanodiamonds, that the diffraction features attributed to the reported polymorphs are consistent with c-diamond containing abundant defects. Combinations of {113} reflection and <011> rotation twins produce HRTEM images and d-spacings that match those attributed to h-, i-, and m-diamond. The diagnostic features of n-diamond in TEM images can arise from thickness effects of c-diamonds. Our data and interpretations strongly suggest that the reported nanodiamond polymorphs are in fact twinned c-diamond. We also report a new type of twin (<11> rotational), which can give rise to grains with dodecagonal symmetry. Our results show that twins are widespread in diamond nanocrystals. A high density of twins could strongly influence their applications.

  2. Diamond MEMS: wafer scale processing, devices, and technology insertion

    NASA Astrophysics Data System (ADS)

    Carlisle, J. A.

    2009-05-01

    Diamond has long held the promise of revolutionary new devices: impervious chemical barriers, smooth and reliable microscopic machines, and tough mechanical tools. Yet it's been an outsider. Laboratories have been effectively growing diamond crystals for at least 25 years, but the jump to market viability has always been blocked by the expense of diamond production and inability to integrate with other materials. Advances in chemical vapor deposition (CVD) processes have given rise to a hierarchy of carbon films ranging from diamond-like carbon (DLC) to vapor-deposited diamond coatings, however. All have pros and cons based on structure and cost, but they all share some of diamond's heralded attributes. The best performer, in theory, is the purest form of diamond film possible, one absent of graphitic phases. Such a material would capture the extreme hardness, high Young's modulus and chemical inertness of natural diamond. Advanced Diamond Technologies Inc., Romeoville, Ill., is the first company to develop a distinct chemical process to create a marketable phase-pure diamond film. The material, called UNCD® (for ultrananocrystalline diamond), features grain sizes from 3 to 300 nm in size, and layers just 1 to 2 microns thick. With significant advantages over other thin films, UNCD is designed to be inexpensive enough for use in atomic force microscopy (AFM) probes, microelectromechanical machines (MEMS), cell phone circuitry, radio frequency devices, and even biosensors.

  3. Sol-gel derived precursors to Group 14 semiconductor nanocrystals - Convenient materials for enabling nanocrystal-based applications

    NASA Astrophysics Data System (ADS)

    Veinot, Jonathan G. C.; Henderson, Eric J.; Hessel, Colin M.

    2009-11-01

    Semiconductor nanocrystals are intriguing because of their electronic, optical, and chemical characteristics. Silicon nanocrystals (Si-NCs) of sub-5 nm dimension are of particular interest due to their intense photoluminescent response and the promise of linking silicon photonics and electronics. Other related nanomaterials of technological importance include SiC and Ge. The following contribution describes key experimental findings pertaining to synthetic methodology, investigation of nanodomain formation and growth, as determined by X-ray powder diffraction (XRD) and photoluminescence (PL) spectroscopy for a series of sol-gel derived prepolymers suitable for preparing Group 14 based nanocrystal containing composites.

  4. Origin of Ultralow Friction and Wear in Ultrananocrystalline Diamond

    DTIC Science & Technology

    2008-06-11

    flats and Si3N4 spheres [13]. Substrates were ultrasonically pre- treated as in [10] except with functionalized nanodiamond powder (4 nm diameter...5.0%. [24] K. Miyoshi, in Proceedings of the Applied Diamond Conference 1995. Applications of Diamond Films and Related Materials: Third International

  5. Stabilization of graphene quantum dots (GQDs) by encapsulation inside zeolitic imidazolate framework nanocrystals for photoluminescence tuning

    NASA Astrophysics Data System (ADS)

    Biswal, Bishnu P.; Shinde, Dhanraj B.; Pillai, Vijayamohanan K.; Banerjee, Rahul

    2013-10-01

    Luminescent graphene quantum dots (GQDs) are encapsulated and stabilized in Zeolitic Imidazolate Framework (ZIF-8) nanocrystals. The GQDs are well confined due to the adsorption on the growing face of the ZIF-8 nanocrystals and have a profound effect on the shape of the nanocrystals from rhombic dodecahedron to spherical. Stabilizing GQDs inside the ZIF-8 nanocrystals results in tailoring of the photoluminescence emission (ca. 32 nm, bathochromic shift) of the GQD@ZIF-8 nanocrystal composite even after 3 months of aging under normal laboratory conditions. Also the water adsorption (at STP) capacity increased for the GQD@ZIF-8 composite as compared to the pristine ZIF-8.Luminescent graphene quantum dots (GQDs) are encapsulated and stabilized in Zeolitic Imidazolate Framework (ZIF-8) nanocrystals. The GQDs are well confined due to the adsorption on the growing face of the ZIF-8 nanocrystals and have a profound effect on the shape of the nanocrystals from rhombic dodecahedron to spherical. Stabilizing GQDs inside the ZIF-8 nanocrystals results in tailoring of the photoluminescence emission (ca. 32 nm, bathochromic shift) of the GQD@ZIF-8 nanocrystal composite even after 3 months of aging under normal laboratory conditions. Also the water adsorption (at STP) capacity increased for the GQD@ZIF-8 composite as compared to the pristine ZIF-8. Electronic supplementary information (ESI) available: Experimental procedures and additional supporting data. See DOI: 10.1039/c3nr03511e

  6. Diamond Sheet: A new diamond tool material

    NASA Technical Reports Server (NTRS)

    Mackey, C. R.

    1982-01-01

    Diamond sheet is termed a diamond tool material because it is not a cutting tool, but rather a new material from which a variety of different tools may be fabricated. In appearance and properties, it resembles a sheet of copper alloy with diamond abrasive dispersed throughout it. It is capable of being cut, formed, and joined by conventional methods, and subsequently used for cutting as a metal bonded diamond tool. Diamond sheet is normally made with industrial diamond as the abrasive material. The metal matrix in diamond sheet is a medium hard copper alloy which has performed well in most applications. This alloy has the capability of being made harder or softer if specific cutting conditions require it. Other alloys have also been used including a precipitation hardened aluminum alloy with very free cutting characteristics. The material is suitable for use in a variety of cutting, surfacing, and ring type tools, as well as in such mundane items as files and sandpaper. It can also be used as a bearing surface (diamond to diamond) and in wear resistant surfaces.

  7. Formation of noble metal nanocrystals in the presence of biomolecules

    NASA Astrophysics Data System (ADS)

    Burt, Justin Lockheart

    One of the most promising, yet least studied routes for producing biocompatible nanostructures involves synthesis in the presence of biomolecules. I hypothesized that globular proteins could provide a suitable framework to regulate the formation of noble metal nanocrystals. As proof of concept, I designed two novel synthesis protocols utilizing bovine serum albumin (BSA) protein to regulate the formation of gold nanocrystals. In the first case, the standard protocol for polyol reduction was modified by replacing ethylene glycol with glycerin, replacing synthetic polymers with BSA as protecting agent, and decreasing the reaction temperature. In the second case, the Brust-Schiffrin two-phase reduction was modified by replacing alkylthiols with BSA as protecting agent, which facilitated a strictly aqueous phase synthesis. Due to superior product yield and rapid reduction at room temperature, the aqueous protocol became the foundation for subsequent studies. I extended this approach to produce well-dispersed ˜2nm silver, gold, and platinum nanocrystals. Having demonstrated the feasibility of BSA-functionalized nanocrystals, some potential uses were explored. BSA-functionalized silver nanocrystals were employed in a broader study on the interaction of silver nanocrystals with HIV. BSA-functionalized gold nanocrystals were utilized for in vivo dosage of a contrast enhancing agent to bacteria. BSA-functionalized platinum nanocrystals were studied as hydrogenation catalysts. Since many intriguing uses for protein-functionalized nanocrystals involve incorporation into biosystems, I sought to enhance biocompatibility by using ascorbic acid as reducing agent. Initial experiments revealed elongated and branched nanocrystals. Such structures were not observed in previous synthesis protocols with BSA, so I hypothesized ascorbic acid was driving their formation. To test my assertion, I reduced ionic gold in an aqueous solution of ascorbic acid, thereby discovering a new method

  8. High average power diamond Raman laser.

    PubMed

    Feve, Jean-Philippe M; Shortoff, Kevin E; Bohn, Matthew J; Brasseur, Jason K

    2011-01-17

    We report a pulsed Raman laser at 1193 nm based on synthetic diamond crystals with a record output power of 24.5 W and a slope efficiency of 57%. We compared the performance of an anti-reflection coated crystal at normal incidence with a Brewster cut sample. Raman oscillation was achieved at both room temperature and under cryogenic operation at 77 K. Modeling of these experiments allowed us to confirm the value of Raman gain coefficient of diamond, which was found to be 13.5 ± 2.0 cm/GW for a pump wavelength of 1030 nm.

  9. Diamond coated silicon field emitter array

    SciTech Connect

    S. Albin; W. Fu; A. Varghese; A. C. Lavarias; G. R. Myneni

    1999-07-01

    Diamond coated silicon tip arrays, with and without a self-aligned gate, were fabricated, and current-voltage characteristics of 400 tips were measured. Diamond films were grown uniformly on Si tips using microwave plasma after nucleation with 10 nm diamond suspension and substrate bias. An emission current of 57 ?A was obtained at 5 V from the ungated array tips separated from an anode at 2 ?m. In the case of the gated arrays with 1.5 ?m aperture, an emission current of 3.4 ?A was measured at a gate voltage of 80 V for an anode separation of 200 ?m. The turn-on voltages for these two types of devices were 0.2 and 40 V, respectively. Diamond coated Si tip arrays have potential applications in field emission based low voltage vacuum electronic devices and microsensors.

  10. The nature and origin of interstellar diamond.

    PubMed

    Blake, D F; Freund, F; Krishnan, K F; Echer, C J; Shipp, R; Bunch, T E; Tielens, A G; Lipari, R J; Hetherington, C J; Chang, S

    1988-04-14

    Microscopic diamond was recently discovered in oxidized acid residues from several carbonaceous chondrite meteorites (for example, the C delta component of the Allende meteorite). Some of the reported properties of C delta seem in conflict with those expected of diamond. Here we present high spatial resolution analytical data which may help to explain such results. The C delta diamond is an extremely fine-grained (0.5-10 nm) single-phase material, but surface and interfacial carbon atoms, which may comprise as much as 25% of the total, impart an 'amorphous' character to some spectral data. These data support the proposed high-pressure conversion of amorphous carbon and graphite into diamonds due to grain-grain collisions in the interstellar medium although a low-pressure mechanism of formation cannot be ruled out.

  11. Diamond Field Emission Source using Transfer Mold Technique Prepared by Diamond Powder Seeding

    NASA Astrophysics Data System (ADS)

    Tezuka, Sachiaki; Matsuba, Yohei; Takahashi, Kohro

    Diamond thin films fabricated by MPCVD (microwave plasma chemical vapor deposition) are available for use as a field emitter material, because of its high mechanical quality, thermal conductivity, chemical stability, environmental tolerance, and NEA (negative electron affinity). Diode and triode emitter arrays using P-doped polycrystalline diamond were manufactured on a SiO2/Si(100) substrate with reverse pyramids formed by the transfer mold technique. As the diamond nucleation process, spin-coat seeding with pure diamond powder dispersed in isoamyl acetate has been introduced in place of the bias method. SEM (scanning electron microscopy) images and Raman spectroscopy indicate that the crystal quality of the diamond thin film fabricated by spin-coat seeding is superior to that fabricated by the bias method. The diamond crystal completely grew on top of the diode emitter by the US (ultrasonic) treatment in a diamond powder solution before spin-coat seeding. The tip radius was smaller than 50 nm. The beginning voltage of the emission of the diode emitter is 3 V after the DC glow discharge treatment in H2, which is lower than that of an emitter array fabricated by the bias method, 40 V. On the other hand, the emission of the diamond triode emitter starts at a gate voltage of only 0.5 V, and the emission current of 50∼60 mA is obtained at a gate voltage of 2 V.

  12. Toward deep blue nano hope diamonds: heavily boron-doped diamond nanoparticles.

    PubMed

    Heyer, Steffen; Janssen, Wiebke; Turner, Stuart; Lu, Ying-Gang; Yeap, Weng Siang; Verbeeck, Jo; Haenen, Ken; Krueger, Anke

    2014-06-24

    The production of boron-doped diamond nanoparticles enables the application of this material for a broad range of fields, such as electrochemistry, thermal management, and fundamental superconductivity research. Here we present the production of highly boron-doped diamond nanoparticles using boron-doped CVD diamond films as a starting material. In a multistep milling process followed by purification and surface oxidation we obtained diamond nanoparticles of 10-60 nm with a boron content of approximately 2.3 × 10(21) cm(-3). Aberration-corrected HRTEM reveals the presence of defects within individual diamond grains, as well as a very thin nondiamond carbon layer at the particle surface. The boron K-edge electron energy-loss near-edge fine structure demonstrates that the B atoms are tetrahedrally embedded into the diamond lattice. The boron-doped diamond nanoparticles have been used to nucleate growth of a boron-doped diamond film by CVD that does not contain an insulating seeding layer.

  13. Nanocrystal diffusion doping.

    PubMed

    Vlaskin, Vladimir A; Barrows, Charles J; Erickson, Christian S; Gamelin, Daniel R

    2013-09-25

    A diffusion-based synthesis of doped colloidal semiconductor nanocrystals is demonstrated. This approach involves thermodynamically controlled addition of both impurity cations and host anions to preformed seed nanocrystals under equilibrium conditions, rather than kinetically controlled doping during growth. This chemistry allows thermodynamic crystal compositions to be prepared without sacrificing other kinetically trapped properties such as shape, size, or crystallographic phase. This doping chemistry thus shares some similarities with cation-exchange reactions, but proceeds without the loss of host cations and excels at the introduction of relatively unreactive impurity ions that have not been previously accessible using cation exchange. Specifically, we demonstrate the preparation of Cd(1-x)Mn(x)Se (0 ≤ x ≤ ∼0.2) nanocrystals with narrow size distribution, unprecedentedly high Mn(2+) content, and very large magneto-optical effects by diffusion of Mn(2+) into seed CdSe nanocrystals grown by hot injection. Controlling the solution and lattice chemical potentials of Cd(2+) and Mn(2+) allows Mn(2+) diffusion into the internal volumes of the CdSe nanocrystals with negligible Ostwald ripening, while retaining the crystallographic phase (wurtzite or zinc blende), shape anisotropy, and ensemble size uniformity of the seed nanocrystals. Experimental results for diffusion doping of other nanocrystals with other cations are also presented that indicate this method may be generalized, providing access to a variety of new doped semiconductor nanostructures not previously attainable by kinetic routes or cation exchange.

  14. Radiation-Induced Nucleation of Diamond from Amorphous Carbon: Effect of Hydrogen.

    PubMed

    Sun, Yanqiu; Kvashnin, Alexander G; Sorokin, Pavel B; Yakobson, Boris I; Billups, W E

    2014-06-05

    Electron irradiation of anthracite functionalized by dodecyl groups leads to recrystallization of the carbon network into diamonds. The diamonds range in size from ∼2 to ∼10 nm and exhibit {111} spacing of 2.1 Å. A bulk process consistent with bias-enhanced nucleation is proposed in which the dodecyl group provides hydrogen during electron irradiation. Recrystallization into diamond occurs in the hydrogenated graphitic subsurface layers. Unfunctionalized anthracite could not be converted into diamond during electron irradiation. The dependence of the phase transition pressure on cluster size was estimated, and it was found that diamond particles with a radius up to 20 nm could be formed.

  15. Physical and Tribological Characteristics of Ion-Implanted Diamond Films

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Heidger, S.; Korenyi-Both, A. L.; Jayne, D. T.; Herrera-Fierro, P.; Shogrin, B.; Wilbur, P. J.; Wu, R. L. C.; Garscadden, A.; Barnes, P. N.

    1994-01-01

    Unidirectional sliding friction experiments were conducted with a natural, polished diamond pin in contact with both as-deposited and carbon-ion-implanted diamond films in ultrahigh vacuum. Diamond films were deposited on silicon, silicon carbide, and silicon nitride by microwave-plasma-assisted chemical vapor deposition. The as-deposited diamond films were impacted with carbon ions at an accelerating energy of 60 keV and a current density of 50 micron A/cm(exp 2) for approximately 6 min, resulting in a dose of 1.2 x 10(exp 17) carbon ions/cm(exp 2). The results indicate that the carbon ion implantation produced a thin surface layer of amorphous, nondiamond carbon. The nondiamond carbon greatly decreased both friction and wear of the diamond films. The coefficients of friction for the carbon-ion-implanted, fine-grain diamond films were less than 0.1, factors of 20 to 30 lower than those for the as-deposited, fine-grain diamond films. The coefficients of friction for the carbon-ion-implanted, coarse-grain diamond films were approximately 0.35, a factor of five lower than those for the as-deposited, coarse-grain diamond films. The wear rates for the carbon-ion-implanted, diamond films were on the order of 10(exp -6) mm(exp 3)/Nm, factors of 30 to 80 lower than that for the as-deposited diamond films, regardless of grain size. The friction of the carbon-ion-implanted diamond films was greatly reduced because the amorphous, nondiamond carbon, which had a low shear strength, was restricted to the surface layers (less than 0.1 micron thick) and because the underlying diamond materials retained their high hardness. In conclusion, the carbon-ion-implanted, fine-grain diamond films can be used effectively as wear resistant, self-lubricating coatings for ceramics, such as silicon nitride and silicon carbide, in ultrahigh vacuum.

  16. Physical and tribological characteristics of ion-implanted diamond films

    SciTech Connect

    Miyoshi, K.; Heidger, S.; Korenyi-both, A.L.; Jayne, D.T.; Herrera-Fierro, P.; Shogrin, B.; Wilbur, P.J.; Wu, R.L.C.; Garscadden, A.; Barnes, P.N.

    1994-11-01

    Unidirectional sliding friction experiments were conducted with a natural, polished diamond pin in contact with both as-deposited and carbon-ion-implanted diamond films in ultrahigh vacuum. Diamond films were deposited on silicon, silicon carbide, and silicon nitride by microwave-plasma-assisted chemical vapor deposition. The as-deposited diamond films were impacted with carbon ions at an accelerating energy of 60 keV and a current density of 50 micron A/cm(exp 2) for approximately 6 min, resulting in a dose of 1.2 x 10(exp 17) carbon ions/cm(exp 2). The results indicate that the carbon ion implantation produced a thin surface layer of amorphous, nondiamond carbon. The nondiamond carbon greatly decreased both friction and wear of the diamond films. The coefficients of friction for the carbon-ion-implanted, fine-grain diamond films were less than 0.1, factors of 20 to 30 lower than those for the as-deposited, fine-grain diamond films. The coefficients of friction for the carbon-ion-implanted, coarse-grain diamond films were approximately 0.35, a factor of five lower than those for the as-deposited, coarse-grain diamond films. The wear rates for the carbon-ion-implanted, diamond films were on the order of 10(exp -6) mm(exp 3)/Nm, factors of 30 to 80 lower than that for the as-deposited diamond films, regardless of grain size. The friction of the carbon-ion-implanted diamond films was greatly reduced because the amorphous, nondiamond carbon, which had a low shear strength, was restricted to the surface layers (less than 0.1 micron thick) and because the underlying diamond materials retained their high hardness. In conclusion, the carbon-ion-implanted, fine-grain diamond films can be used effectively as wear resistant, self-lubricating coatings for ceramics, such as silicon nitride and silicon carbide, in ultrahigh vacuum.

  17. Investigating the role of hydrogen in ultra-nanocrystalline diamond thin film growth

    NASA Astrophysics Data System (ADS)

    Birrell, James; Gerbi, J. E.; Auciello, O. A.; Carlisle, J. A.

    2006-08-01

    Hydrogen has long been known to be critical for the growth of high-quality microcrystalline diamond thin films as well as homoepitaxial single-crystal diamond. A hydrogen-poor growth process that results in ultra-nanocrystalline diamond thin films has also been developed, and it has been theorized that diamond growth with this gas chemistry can occur in the absence of hydrogen. This study investigates the role of hydrogen in the growth of ultra-nanocrystalline diamond thin films in two different regimes. First, we add hydrogen to the gas phase during growth, and observe that there seems to be a competitive growth process occurring between microcrystalline diamond and ultra-nanocrystalline diamond, rather than a simple increase in the grain size of ultra-nanocrystalline diamond. Second, we remove hydrogen from the plasma by changing the hydrocarbon precursor from methane to acetylene and observe that there does seem to be some sort of lower limit to the amount of hydrogen that can sustain ultra-nanocrystalline diamond growth. We speculate that this is due to the amount of hydrogen needed to stabilize the surface of the growing diamond nanocrystals.

  18. Solution based synthesis of simple fcc Si nano-crystals under ambient conditions.

    PubMed

    Balcı, Mustafa H; Sæterli, Ragnhild; Maria, Jerome; Lindgren, Mikael; Holmestad, Randi; Grande, Tor; Einarsrud, Mari-Ann

    2013-02-28

    We demonstrate for the first time that simple face-centered cubic (fcc) silicon nano-crystals can be produced by a solution based bottom-up synthesis route under ambient conditions. Simple fcc Si nano-crystals (2-7 nm) were prepared at room temperature by using sodium cyclopentadienide as a reducing agent for silicon tetrachloride. Photoluminescence emission at 550 nm was observed for the fcc silicon nano-crystals upon excitation at 340 nm, indicating that fcc Si nano-crystals were exhibiting direct bandgap like semiconductor properties with very fast radiative recombination rates. The new synthesis route makes possible the production and study of simple fcc polymorphs of Si nano-crystals with an easy alteration of surface termination groups.

  19. Electrically conductive diamond electrodes

    DOEpatents

    Swain, Greg; Fischer, Anne ,; Bennett, Jason; Lowe, Michael

    2009-05-19

    An electrically conductive diamond electrode and process for preparation thereof is described. The electrode comprises diamond particles coated with electrically conductive doped diamond preferably by chemical vapor deposition which are held together with a binder. The electrodes are useful for oxidation reduction in gas, such as hydrogen generation by electrolysis.

  20. Diamond Nucleation from Amorphous Carbon and Graphite with COH Fluids: an in Situ High Pressure and Temperature Laser-Heated Diamond Anvil Cell Experimental Study

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Prakapenka, V.; Kubo, A.; Kavner, A.; Green, H. W.; Dobrzhinetskaya, L. F.

    2007-12-01

    Microdiamonds from orogenic belts contain nanometer size fluid inclusions suggesting diamond formation from supercritical COH fluids. Previous studies have shown that diamonds synthesized from high pressure and temperature experiments with supercritical COH fluids are characterized by skeletal morphology and solid oxide inclusions. However, mechanism and kinetics of graphite/carbon-to-diamond transformation promoted by COH fluids at high pressure and high temperature conditions are not well understood. Here we report in situ observations of diamond nucleation from COH fluids in laser-heated diamond anvil cell. Our experimental starting materials were amorphous carbon (impurity < 2ppm) and graphite (99.9% pure). Oxalic acid dihydrate (COOH)2·2H2O) was added to amorphous carbon and glucose (C6H12O6) was added to both amorphous carbon and graphite. The organic compounds (3 wt.%) provide CO2- and CH4-rich fluid environments respectively during their breakdown at high pressure and temperature. The mixtures were kept at temperature of 1400-1700 °C and pressure of 8-10 GPa for 10-30 minutes. Experiments show that only nanocrystals of diamond were nucleated from amorphous carbon in CO2-rich fluid environment. The fastest rate of diamond nucleation and growth of ~15 micron size crystals was found in the mixture of amorphous carbon with glucose (CH4-rich environment), whereas only nanocrystalline nuclei were produced in the mixture of graphite with glucose. We have also established that under anhydrous conditions, no diamond nucleation occurred in pure graphite, and only nanocrystals of diamond were observed in the amorphous carbon starting material at temperatures 1700-1900 °C. Our results revealed that the kinetics of diamond nucleation depend on the ¡°precursor¡±: diamond nucleates and grows faster from amorphous carbon than from graphite in the presence of COH fluid; in our anhydrous experiments diamond nucleates only from amorphous carbon. These results

  1. Controlled synthesis of bright and compatible lanthanide-doped upconverting nanocrystals

    DOEpatents

    Cohen, Bruce E.; Ostrowski, Alexis D.; Chan, Emory M.; Gargas, Daniel J.; Katz, Elan M.; Schuck, P. James; Milliron, Delia J.

    2017-01-31

    Certain nanocrystals possess exceptional optical properties that may make them valuable probes for biological imaging, but rendering these nanoparticles biocompatible requires that they be small enough not to perturb cellular systems. This invention describes a phosphorescent upconverting sub-10 nm nanoparticle comprising a lanthanide-doped hexagonal .beta.-phase NaYF.sub.4 nanocrystal and methods for making the same.

  2. Friction and wear of plasma-deposited diamond films

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Wu, Richard L. C.; Garscadden, Alan; Barnes, Paul N.; Jackson, Howard E.

    1993-01-01

    Reciprocating sliding friction experiments in humid air and in dry nitrogen and unidirectional sliding friction experiments in ultrahigh vacuum were conducted with a natural diamond pin in contact with microwave-plasma-deposited diamond films. Diamond films with a surface roughness (R rms) ranging from 15 to 160 nm were produced by microwave-plasma-assisted chemical vapor deposition. In humid air and in dry nitrogen, abrasion occurred when the diamond pin made grooves in the surfaces of diamond films, and thus the initial coefficients of friction increased with increasing initial surface roughness. The equilibrium coefficients of friction were independent of the initial surface roughness of the diamond films. In vacuum the friction for diamond films contacting a diamond pin arose primarily from adhesion between the sliding surfaces. In these cases, the initial and equilibrium coefficients of friction were independent of the initial surface roughness of the diamond films. The equilibrium coefficients of friction were 0.02 to 0.04 in humid air and in dry nitrogen, but 1.5 to 1.8 in vacuum. The wear factor of the diamond films depended on the initial surface roughness, regardless of environment; it increased with increasing initial surface roughness. The wear factors were considerably higher in vacuum than in humid air and in dry nitrogen.

  3. Cathodoluminescence of diamond as an indicator of its metamorphic history

    NASA Astrophysics Data System (ADS)

    Kopylova, Maya; Bruce, Loryn; Longo, Micaela; Ryder, John; Dobrzhinetskaya, Larissa

    2010-05-01

    Diamond displays a supreme resistance to chemical and mechanical weathering, ensuring its survival through complex and prolonged crustal processes, including metamorphism and exhumation. For these reasons, volcanic sources and secondary and tertiary collectors for detrital placer diamonds, like Ural or Bingara diamonds, may be difficult to determine. If metamorphic processes leave their marks on diamond, they can be used to reconstruct crustal geologic processes and ages of primary diamondiferous volcanics. Four diamond suites extracted from metamorphic rocks have been characterized using optical CL, infrared and CL spectroscopy, and photoluminescence at the liquid nitrogen temperature. The studied diamonds are from the ~2.7 Ga sedimentary conglomerate and lamprophyric breccia metamorphosed in the greenschist facies (Wawa, Northern Ontario, Canada) during the 2.67 Ga Kenoran orogeny, and from the ultra-high pressure (UHP) terranes of Kokchetav (Kazakhstan) and Erzgebirge (Germany) exhumated in the Paleozoic. Wawa diamonds (Type IaAB and Type II) displayed green, yellow, orange, and red CL colours controlled by the CL emittance at 520, 576 nm, and between 586 and 664 nm. The UHP terranes diamonds show much weaker CL; few luminescent stones display CL peaks at 395, 498, 528 nm and a broad band at 580-668 nm. In contrast, most common diamonds found in unmetamorphosed rocks, i.e. octahedrally grown Type IaAB stones, luminescence blue emitting light at ~415-440 nm and 480-490 nm. There is a noticeable difference between cathodoluminescence of these diamonds and diamonds in metamorphic rocks. The studied diamonds that experienced metamorphism show a shift of CL emission to longer wavelengths (above 520 nm) and to green, yellow and red CL colours. Photoluminescence has the high resolution necessary to assign luminescence to specific optical centers of diamond. Diamonds in metamorphic rocks contain H3 (pairs of substitutional nitrogen atoms separated by a vacancy) and NVo

  4. Optical properties of femtosecond laser-treated diamond

    NASA Astrophysics Data System (ADS)

    Calvani, P.; Bellucci, A.; Girolami, M.; Orlando, S.; Valentini, V.; Lettino, A.; Trucchi, D. M.

    2014-10-01

    A laser-induced periodic surface structure (LIPSS) has been fabricated on polycrystalline diamond by an ultrashort Ti:Sapphire pulsed laser source ( λ = 800 nm, P = 3 mJ, 100 fs) in a high vacuum chamber (<10-7 mbar) in order to increase diamond absorption in the visible and infrared wavelength ranges. A horizontally polarized laser beam had been focussed perpendicularly to the diamond surface and diamond target had been moved by an automated X- Y translational stage along the two directions orthogonal to the optical axis. Scanning electron microscopy of samples reveals an LIPSS with a ripple period of about 170 nm, shorter than the laser wavelength. Raman spectra of processed sample do not point out any evident sp 2 content, and diamond peak presents a right shift, indicating a compressive stress. The investigation of optical properties of fs-laser surface textured diamond is reported. Spectral photometry in the range 200/2,000 nm wavelength shows a significant increase of visible and infrared absorption (more than 80 %) compared to untreated specimens (less than 40 %). The analysis of optical characterization data highlights a close relationship between fabricated LIPSS and absorption properties, confirming the optical effectiveness of such a treatment as a light-trapping structure for diamond: these properties, reported for the first time, open the path for new applications of CVD diamond.

  5. Polishing of polycrystalline diamond films

    NASA Astrophysics Data System (ADS)

    Harker, Alan B.; Flintoff, John F.; DeNatale, Jeffrey F.

    1990-12-01

    Optically smooth surfaces can be produced on initially rough polycrystalline diamond film through the combined use of reactive ion etching and high temperature lapping on Fe metai Protective thin film barriers are first applied to the diamond surface to restrict the reactiv oxygen or hydrogen ion etching process to regions of greatest roughness. When the overaJ surface roughness has been reduced sufficiently by etching mechanical lapping of the surfac on an Fe plate at temperatures of 730C-900C in the presence of hydrogen can be used t produce surface roughnesses of less than 10 nm as measured by profilimetry. The tw techniques are complementary for flat surfaces while the reactive etching process alone can b used with shaped substrates to produce a surface finish suitable for LWIR optical applications. 1.

  6. Diamond heteroepitaxial lateral overgrowth

    NASA Astrophysics Data System (ADS)

    Tang, Yung-Hsiu

    This dissertation describes improvements in the growth of single crystal diamond by microwave plasma-assisted chemical vapor deposition (CVD). Heteroepitaxial (001) diamond was grown on 1 cm. 2 a-plane sapphiresubstrates using an epitaxial (001) Ir thin-film as a buffer layer. Low-energy ion bombardment of the Ir layer, a process known as bias-enhanced nucleation, is a key step in achieving a high density of diamond nuclei. Bias conditions were optimized to form uniformly-high nucleation densities across the substrates, which led to well-coalesced diamond thin films after short growth times. Epitaxial lateral overgrowth (ELO) was used as a means of decreasing diamond internal stress by impeding the propagation of threading dislocations into the growing material. Its use in diamond growth requires adaptation to the aggressive chemical and thermal environment of the hydrogen plasma in a CVD reactor. Three ELO variants were developed. The most successful utilized a gold (Au) mask prepared by vacuum evaporation onto the surface of a thin heteroepitaxial diamond layer. The Au mask pattern, a series of parallel stripes on the micrometer scale, was produced by standard lift-off photolithography. When diamond overgrows the mask, dislocations are largely confined to the substrate. Differing degrees of confinement were studied by varying the stripe geometry and orientation. Significant improvement in diamond quality was found in the overgrown regions, as evidenced by reduction of the Raman scattering linewidth. The Au layer was found to remain intact during diamond overgrowth and did not chemically bond with the diamond surface. Besides impeding the propagation of threading dislocations, it was discovered that the thermally-induced stress in the CVD diamond was significantly reduced as a result of the ductile Au layer. Cracking and delamination of the diamond from the substrate was mostly eliminated. When diamond was grown to thicknesses above 0.1 mm it was found that

  7. Diamond bio electronics.

    PubMed

    Linares, Robert; Doering, Patrick; Linares, Bryant

    2009-01-01

    The use of diamond for advanced applications has been the dream of mankind for centuries. Until recently this dream has been realized only in the use of diamond for gemstones and abrasive applications where tons of diamonds are used on an annual basis. Diamond is the material system of choice for many applications, but its use has historically been limited due to the small size, high cost, and inconsistent (and typically poor) quality of available diamond materials until recently. The recent development of high quality, single crystal diamond crystal growth via the Chemical Vapor Deposition (CVD) process has allowed physcists and increasingly scientists in the life science area to think beyond these limitations and envision how diamond may be used in advanced applications ranging from quantum computing, to power generation and molecular imaging, and eventually even diamond nano-bots. Because of diamond's unique properties as a bio-compatible material, better understanding of diamond's quantum effects and a convergence of mass production, semiconductor-like fabrication process, diamond now promises a unique and powerful key to the realization of the bio-electronic devices being envisioned for the new era of medical science. The combination of robust in-the-body diamond based sensors, coupled with smart bio-functionalized diamond devices may lead to diamond being the platform of choice for bio-electronics. This generation of diamond based bio-electronic devices would contribute substantially to ushering in a paradigm shift for medical science, leading to vastly improved patient diagnosis, decrease of drug development costs and risks, and improved effectiveness of drug delivery and gene therapy programs through better timed and more customized solutions.

  8. Nanocrystalline diamond micro-anvil grown on single crystal diamond as a generator of ultra-high pressures

    NASA Astrophysics Data System (ADS)

    Samudrala, Gopi K.; Moore, Samuel L.; Velisavljevic, Nenad; Tsoi, Georgiy M.; Baker, Paul A.; Vohra, Yogesh K.

    2016-09-01

    By combining mask-less lithography and chemical vapor deposition (CVD) techniques, a novel two-stage diamond anvil has been fabricated. A nanocrystalline diamond (NCD) micro-anvil 30 μ m in diameter was grown at the center of a [100]-oriented, diamond anvil by utilizing microwave plasma CVD method. The NCD micro-anvil has a diamond grain size of 115 nm and micro-focused Raman and X-ray Photoelectron spectroscopy analysis indicate sp3-bonded diamond content of 72%. These CVD grown NCD micro-anvils were tested in an opposed anvil configuration and the transition metals osmium and tungsten were compressed to high pressures of 264 GPa in a diamond anvil cell.

  9. Nanostructured diamond layers enhance the infrared spectroscopy of biomolecules.

    PubMed

    Kozak, Halyna; Babchenko, Oleg; Artemenko, Anna; Ukraintsev, Egor; Remes, Zdenek; Rezek, Bohuslav; Kromka, Alexander

    2014-03-04

    We report on the fabrication and practical use of high-quality optical elements based on Au mirrors coated with diamond layers with flat, nanocolumnar, and nanoporous morphologies. Diamond layers (100 nm thickness) are grown at low temperatures (about 300 °C) from a methane, carbon dioxide, and hydrogen gas mixture by a pulsed microwave plasma system with linear antennas. Using grazing angle reflectance (GAR) Fourier transform infrared spectroscopy with p-polarized light, we compare the IR spectra of fetal bovine serum proteins adsorbed on diamond layers with oxidized (hydrophilic) surfaces. We show that the nanoporous diamond layers provide IR spectra with a signal gain of about 600% and a significantly improved sensitivity limit. This is attributed to its enhanced internal surface area. The improved sensitivity enabled us to distinguish weak infrared absorption peaks of <10-nm-thick protein layers and thereby to analyze the intimate diamond-molecule interface.

  10. Diamond heteroepitaxial lateral overgrowth

    SciTech Connect

    Tang, Y. -H.; Bi, B.; Golding, B.

    2015-02-24

    A method of diamond heteroepitaxial lateral overgrowth is demonstrated which utilizes a photolithographic metal mask to pattern a thin (001) epitaxial diamond surface. Significant structural improvement was found, with a threading dislocation density reduced by two orders of magnitude at the top surface of a thick overgrown diamond layer. In the initial stage of overgrowth, a reduction of diamond Raman linewidth in the overgrown area was also realized. Thermally-induced stress and internal stress were determined by Raman spectroscopy of adhering and delaminated diamond films. As a result, the internal stress is found to decrease as sample thickness increases.

  11. Diamonds for beam instrumentation

    SciTech Connect

    Griesmayer, Erich

    2013-04-19

    Diamond is perhaps the most versatile, efficient and radiation tolerant material available for use in beam detectors with a correspondingly wide range of applications in beam instrumentation. Numerous practical applications have demonstrated and exploited the sensitivity of diamond to charged particles, photons and neutrons. In this paper, a brief description of a generic diamond detector is given and the interaction of the CVD diamond detector material with protons, electrons, photons and neutrons is presented. Latest results of the interaction of sCVD diamond with 14 MeV mono-energetic neutrons are shown.

  12. Diamond Synthesis Employing Nanoparticle Seeds

    NASA Technical Reports Server (NTRS)

    Uppireddi, Kishore (Inventor); Morell, Gerardo (Inventor); Weiner, Brad R. (Inventor)

    2014-01-01

    Iron nanoparticles were employed to induce the synthesis of diamond on molybdenum, silicon, and quartz substrates. Diamond films were grown using conventional conditions for diamond synthesis by hot filament chemical vapor deposition, except that dispersed iron oxide nanoparticles replaced the seeding. This approach to diamond induction can be combined with dip pen nanolithography for the selective deposition of diamond and diamond patterning while avoiding surface damage associated to diamond-seeding methods.

  13. Nanocrystal dispersed amorphous alloys

    NASA Technical Reports Server (NTRS)

    Perepezko, John H. (Inventor); Allen, Donald R. (Inventor); Foley, James C. (Inventor)

    2001-01-01

    Compositions and methods for obtaining nanocrystal dispersed amorphous alloys are described. A composition includes an amorphous matrix forming element (e.g., Al or Fe); at least one transition metal element; and at least one crystallizing agent that is insoluble in the resulting amorphous matrix. During devitrification, the crystallizing agent causes the formation of a high density nanocrystal dispersion. The compositions and methods provide advantages in that materials with superior properties are provided.

  14. Nanocrystals for electronics.

    PubMed

    Panthani, Matthew G; Korgel, Brian A

    2012-01-01

    Semiconductor nanocrystals are promising materials for low-cost large-area electronic device fabrication. They can be synthesized with a wide variety of chemical compositions and size-tunable optical and electronic properties as well as dispersed in solvents for room-temperature deposition using various types of printing processes. This review addresses research progress in large-area electronic device applications using nanocrystal-based electrically active thin films, including thin-film transistors, light-emitting diodes, photovoltaics, and thermoelectrics.

  15. Dependence of the stimulated luminescence threshold in ZnO nanocrystals on their geometric shape

    SciTech Connect

    Gruzintsev, A. N. Redkin, A. N.; Barthou, C.

    2010-05-15

    The effect of the shape and dimensions of zinc oxide nanocrystals on the spontaneous luminescence decay times and the thresholds of stimulated luminescence in the ultraviolet spectral region is studied. It is shown that the columnar nanocrystals with hexagonal faceting exhibit the lowest threshold power of optical excitation for the diameters of the nanocavities are 100-200 nm, comparable to the absorption length for the excitation light. Different mechanisms of lasing are established for nanocrystals shaped as prisms and pyramids with a hexagonal base. Variations in the decay times and lasing thresholds can be attributed to different local densities of photon states in regularly shaped nanocrystals.

  16. Radiative decay rates of impurity states in semiconductor nanocrystals

    NASA Astrophysics Data System (ADS)

    Turkov, Vadim K.; Baranov, Alexander V.; Fedorov, Anatoly V.; Rukhlenko, Ivan D.

    2015-10-01

    Doped semiconductor nanocrystals is a versatile material base for contemporary photonics and optoelectronics devices. Here, for the first time to the best of our knowledge, we theoretically calculate the radiative decay rates of the lowest-energy states of donor impurity in spherical nanocrystals made of four widely used semiconductors: ZnS, CdSe, Ge, and GaAs. The decay rates were shown to vary significantly with the nanocrystal radius, increasing by almost three orders of magnitude when the radius is reduced from 15 to 5 nm. Our results suggest that spontaneous emission may dominate the decay of impurity states at low temperatures, and should be taken into account in the design of advanced materials and devices based on doped semiconductor nanocrystals.

  17. Radiative decay rates of impurity states in semiconductor nanocrystals

    SciTech Connect

    Turkov, Vadim K.; Baranov, Alexander V.; Fedorov, Anatoly V.; Rukhlenko, Ivan D.

    2015-10-15

    Doped semiconductor nanocrystals is a versatile material base for contemporary photonics and optoelectronics devices. Here, for the first time to the best of our knowledge, we theoretically calculate the radiative decay rates of the lowest-energy states of donor impurity in spherical nanocrystals made of four widely used semiconductors: ZnS, CdSe, Ge, and GaAs. The decay rates were shown to vary significantly with the nanocrystal radius, increasing by almost three orders of magnitude when the radius is reduced from 15 to 5 nm. Our results suggest that spontaneous emission may dominate the decay of impurity states at low temperatures, and should be taken into account in the design of advanced materials and devices based on doped semiconductor nanocrystals.

  18. Doped semiconductor nanocrystal based fluorescent cellular imaging probes.

    PubMed

    Maity, Amit Ranjan; Palmal, Sharbari; Basiruddin, S K; Karan, Niladri Sekhar; Sarkar, Suresh; Pradhan, Narayan; Jana, Nikhil R

    2013-06-21

    Doped semiconductor nanocrystals such as Mn doped ZnS, Mn doped ZnSe and Cu doped InZnS, are considered as new classes of fluorescent biological probes with low toxicity. Although the synthesis in high quality of such nanomaterials is now well established, transforming them into functional fluorescent probes remains a challenge. Here we report a fluorescent cellular imaging probe made of high quality doped semiconductor nanocrystals. We have identified two different coating approaches suitable for transforming the as synthesized hydrophobic doped semiconductor nanocrystals into water-soluble functional nanoparticles. Following these approaches we have synthesized TAT-peptide- and folate-functionalized nanoparticles of 10-80 nm hydrodynamic diameter and used them as a fluorescent cell label. The results shows that doped semiconductor nanocrystals can be an attractive alternative for conventional cadmium based quantum dots with low toxicity.

  19. Controlled crystalline structure and surface stability of cobalt nanocrystals.

    PubMed

    Bao, Yuping; Beerman, Michael; Pakhomov, Alexandre B; Krishnan, Kannan M

    2005-04-21

    The synthesis of monodispersed 10 nm cobalt nanocrystals with controlled crystal morphology and investigation of the surface stability of these nanocrystals are described. Depending on the surfactants used, single crystalline or multiple grain nanocrystals can be reproducibly produced. The relative surface stability of these nanocrystals is analyzed using the temperature dependences of the dc magnetic susceptibility. The novel method, which allows sensitive monitoring of the surface stability, is based on the observation that, with particle oxidation, an anomalous peak appears at 8 K in zero-field-cooled magnetization measurements. It is found that the surfactant protective layer is more important for long-term stability at room temperature, while the high-temperature oxidation rate is controlled by the crystal morphology of the nanoparticles.

  20. The Nature of Diamonds

    NASA Astrophysics Data System (ADS)

    Harlow, George E.

    1997-10-01

    The paragon of physical perfection and a sparkling example of Earth's forces at work, the diamond has fascinated all realms of society, from starlets to scientists. The Nature of Diamonds is a comprehensive look at nature's most coveted gem. A handsome, large-format book, The Nature of Diamonds is an authoritative and richly-illustrated tribute to the diamond. Leading geologists, gemologists, physicists, and cultural observers cover every facet of the stone, from its formation in the depths of the Earth, its ascent to the surface, and its economic, regal, social, and technological roles. Cutting-edge research takes the reader to the frontiers of diamond exploration and exploitation, from the Arctic wastes to the laboratories where diamonds are created for massive road shredders that rip up and then re-create superhighways. Here also is an overview of cutting, from the rough stones in Roman rings to the highly-faceted stones we see today, and a glimpse into the business of diamonds. Finally, The Nature of Diamonds chronicles scientific and cultural history and explores the diamond as both a sacred and a social symbol, including a picture history of betrothal rings. Wide-ranging illustrations explain the geology of diamonds, chart the history of mining from its origins in India and Brazil through the diamond rush in South Africa and today's high-tech enterprises, and capture the brilliance and beauty of this extraordinary gem. _

  1. Multiexciton fluorescence from semiconductor nanocrystals

    NASA Astrophysics Data System (ADS)

    Fisher, Brent; Caruge, Jean-Michel; Chan, Yin-Thai; Halpert, Jonathan; Bawendi, Moungi G.

    2005-11-01

    We use transient photoluminescence to spectrally resolve the emission from 1, 2, and 3 electron-hole pairs states in CdSe colloidal nanocrystals with radii ranging between 2.3 and 5.2 nm. Temporally and spectrally resolved multiexciton emission from single NCs is also observed. The observation of multiexciton emission enables new experiments and potential applications at both the single NC level and using ensembles of NCs. First we discuss the use of single CdSe(CdZnS) core(shell) colloidal NCs (spheres and rods) to generate triggered photon pair emission at room temperature, with specific ordering of the pair's constituent photons. Second, we incorporate CdSe/ZnS core-shell nanocrystals into a TiO 2 host matrix and observe simultaneous two-state amplified spontaneous emission and lasing from both multiexcitonic transitions (1S 3/2-1S e and 1P 3/2-1P e) in a surface-emitting distributed feedback CdSe NC laser. From our data we deduce radiative lifetimes, quantum yields, stimulated emission gain, and power dependencies for the multiexciton transitions.

  2. Thermally stable diamond brazing

    DOEpatents

    Radtke, Robert P.

    2009-02-10

    A cutting element and a method for forming a cutting element is described and shown. The cutting element includes a substrate, a TSP diamond layer, a metal interlayer between the substrate and the diamond layer, and a braze joint securing the diamond layer to the substrate. The thickness of the metal interlayer is determined according to a formula. The formula takes into account the thickness and modulus of elasticity of the metal interlayer and the thickness of the TSP diamond. This prevents the use of a too thin or too thick metal interlayer. A metal interlayer that is too thin is not capable of absorbing enough energy to prevent the TSP diamond from fracturing. A metal interlayer that is too thick may allow the TSP diamond to fracture by reason of bending stress. A coating may be provided between the TSP diamond layer and the metal interlayer. This coating serves as a thermal barrier and to control residual thermal stress.

  3. Organization of 'nanocrystal molecules' using DNA

    NASA Astrophysics Data System (ADS)

    Alivisatos, A. Paul; Johnsson, Kai P.; Peng, Xiaogang; Wilson, Troy E.; Loweth, Colin J.; Bruchez, Marcel P.; Schultz, Peter G.

    1996-08-01

    PATTERNING matter on the nanometre scale is an important objective of current materials chemistry and physics. It is driven by both the need to further miniaturize electronic components and the fact that at the nanometre scale, materials properties are strongly size-dependent and thus can be tuned sensitively1. In nanoscale crystals, quantum size effects and the large number of surface atoms influence the, chemical, electronic, magnetic and optical behaviour2-4. 'Top-down' (for example, lithographic) methods for nanoscale manipulation reach only to the upper end of the nanometre regime5; but whereas 'bottom-up' wet chemical techniques allow for the preparation of mono-disperse, defect-free crystallites just 1-10 nm in size6-10, ways to control the structure of nanocrystal assemblies are scarce. Here we describe a strategy for the synthesis of'nanocrystal molecules', in which discrete numbers of gold nanocrystals are organized into spatially defined structures based on Watson-Crick base-pairing interactions. We attach single-stranded DNA oligonucleotides of defined length and sequence to individual nanocrystals, and these assemble into dimers and trimers on addition of a complementary single-stranded DNA template. We anticipate that this approach should allow the construction of more complex two-and three-dimensional assemblies.

  4. Diamond stabilization of ice multilayers at human body temperature.

    PubMed

    Wissner-Gross, Alexander D; Kaxiras, Efthimios

    2007-08-01

    Diamond is a promising material for wear-resistant medical coatings. Here we report a remarkable increase in the melting point of ice resting on a diamond (111) surface modified with a submonolayer of Na+. Our molecular dynamics simulations show that the interfacial ice bilayer melts at a temperature 130 K higher than in free ice, and relatively thick ice films (2.6 nm at 298 K and 2.2 nm at 310 K ) are stabilized by dipole interactions with the substrate. This unique physical effect may enable biocompatibility-enhancing ice overcoatings for diamond at human body temperature.

  5. Super-stable ultrafine beta-tungsten nanocrystals with metastable phase and related magnetism.

    PubMed

    Xiao, J; Liu, P; Liang, Y; Li, H B; Yang, G W

    2013-02-07

    Ultrafine tungsten nanocrystals (average size of 3 nm) with a metastable phase (beta-tungsten with A15 structure, β-W) have been prepared by laser ablation of tungsten in liquid nitrogen. The as-prepared metastable nanocrystals exhibited super-stablity, and can keep the same metastable structure over a period of 6 months at room temperature. This super-stability is attributed to the nanosized confinement effect of ultrafine nanocrystals. The magnetism measurements showed that the β-W nanocrystals have weak ferromagnetic properties at 2 K, which may arise from surface defects and unpaired electrons on the surface of the ultrafine nanocrystals. These findings provided useful information for the application of ultrafine β-W nanocrystals in microelectronics and spintronics.

  6. Size-dependent structural transition from multiple-twinned particles to epitaxial fcc nanocrystals and nanocrystal decay

    SciTech Connect

    Sato, K.; Huang, W. J.; Bohra, F.; Sivaramakrishnan, S.; Tedjasaputra, A. P.; Zuo, J. M.

    2007-10-01

    The size dependence of structural transition from multiple-twinned particles (MTP) to epitaxial face centered cubic nanocrystals was investigated for Ag nanoparticles formed on Si(001) surfaces by in situ reflection high-energy electron diffraction and ex situ transmission electron microscopy. The transition from MTP to nanocrystals was promoted by postdeposition annealing. Clear particle size dependence is found in the epitaxial formation temperatures (T{sub E}), which is about 2/3 of the calculated, size-dependent, melting temperature (T{sub M}) using the value of surface energy {gamma}{sub S}=1.2 J/m{sup 2} for larger particles (>2 nm). Once nanocrystals are formed, they decay and disappear in a narrow temperature range between 795 and 850 K. No evidence of nanocrystal melting was detected from the reflection high-energy electron diffraction observations.

  7. Size-dependent structural transition from multiple-twinned particles to epitaxial fcc nanocrystals and nanocrystal decay

    NASA Astrophysics Data System (ADS)

    Sato, K.; Huang, W. J.; Bohra, F.; Sivaramakrishnan, S.; Tedjasaputra, A. P.; Zuo, J. M.

    2007-10-01

    The size dependence of structural transition from multiple-twinned particles (MTP) to epitaxial face centered cubic nanocrystals was investigated for Ag nanoparticles formed on Si(001) surfaces by in situ reflection high-energy electron diffraction and ex situ transmission electron microscopy. The transition from MTP to nanocrystals was promoted by postdeposition annealing. Clear particle size dependence is found in the epitaxial formation temperatures (TE) , which is about 2/3 of the calculated, size-dependent, melting temperature (TM) using the value of surface energy γS=1.2J/m2 for larger particles (>2nm) . Once nanocrystals are formed, they decay and disappear in a narrow temperature range between 795 and 850K . No evidence of nanocrystal melting was detected from the reflection high-energy electron diffraction observations.

  8. Frequency upconverted lasing of nanocrystal quantum dots in microbeads

    NASA Astrophysics Data System (ADS)

    Zhang, Chunfeng; Zhang, Fan; Cheng, An; Kimball, Brian; Wang, Andrew Y.; Xu, Jian

    2009-11-01

    Stable, frequency upconverted lasing of semiconductor nanocrystal quantum dots was demonstrated in silica microbeads under two-photon pumping conditions. Upon infrared excitation, the stimulated emission of the nanocrystal-doped microbeads exhibits sharp peaks at λ ˜610 nm with narrow line widths of ≤1 nm. The lasing action has been attributed to the biexciton gain coupled to the whispering gallery modes in spherical cavities, as confirmed by time-resolved photoluminescence spectra. The lasing lifetime characterized in term of pulse numbers (˜106 pulses) was two orders of magnitude longer than that of the dye salt-based two-photon lasers.

  9. Nano-inclusions in diamond: Evidence of diamond genesis

    NASA Astrophysics Data System (ADS)

    Wirth, R.

    2015-12-01

    The use of Focused Ion Beam technology (FIB) for TEM sample preparation introduced approximately 15 years ago revolutionized the application of TEM in Geosciences. For the first time, FIB enabled cutting samples for TEM use from exactly the location we are interested in. Applied to diamond investigation, this technique revealed the presence of nanometre-sized inclusions in diamond that have been simply unknown before. Nanoinclusions in diamond from different location and origin such as diamonds from the Lower and Upper Mantle, metamorphic diamonds (Kazakhstan, Erzgebirge, Bohemia), diamonds from ophiolites (Tibet, Mongolia, Xinjiang, Ural Mountains), diamonds from igneous rocks (Hawaii, Kamchatka) and impact diamonds (Popigai Crater, Siberia) have been investigated during the last 15 years. The major conclusion of all these TEM studies is, that the nanoinclusions, their phases and phase composition together with the micro- and nanostructure evidence the origin of diamond and genesis of diamond. We can discriminate Five different mechanisms of diamond genesis in nature are observed: Diamond crystallized from a high-density fluid (Upper mantle and metamorphic diamond). Diamond crystallized from carbonatitic melt (Lower mantle diamond). Diamond precipitates from a metal alloy melt (Diamond from ophiolites). Diamond crystallized by gas phase condensation or chemical vapour condensation (CVD) (Lavas from Kamchatka, xenoliths in Hawaiian lavas). Direct transformation of graphite into diamond.

  10. Patterning of nanocrystalline diamond films for diamond microstructures useful in MEMS and other devices

    DOEpatents

    Gruen, Dieter M.; Busmann, Hans-Gerd; Meyer, Eva-Maria; Auciello, Orlando; Krauss, Alan R.; Krauss, Julie R.

    2004-11-02

    MEMS structure and a method of fabricating them from ultrananocrystalline diamond films having average grain sizes of less than about 10 nm and feature resolution of less than about one micron . The MEMS structures are made by contacting carbon dimer species with an oxide substrate forming a carbide layer on the surface onto which ultrananocrystalline diamond having average grain sizes of less than about 10 nm is deposited. Thereafter, microfabrication process are used to form a structure of predetermined shape having a feature resolution of less than about one micron.

  11. Novel silica stabilization method for the analysis of fine nanocrystals using coherent X-ray diffraction imaging.

    PubMed

    Monteforte, Marianne; Estandarte, Ana K; Chen, Bo; Harder, Ross; Huang, Michael H; Robinson, Ian K

    2016-07-01

    High-energy X-ray Bragg coherent diffraction imaging (BCDI) is a well established synchrotron-based technique used to quantitatively reconstruct the three-dimensional morphology and strain distribution in nanocrystals. The BCDI technique has become a powerful analytical tool for quantitative investigations of nanocrystals, nanotubes, nanorods and more recently biological systems. BCDI has however typically failed for fine nanocrystals in sub-100 nm size regimes - a size routinely achievable by chemical synthesis - despite the spatial resolution of the BCDI technique being 20-30 nm. The limitations of this technique arise from the movement of nanocrystals under illumination by the highly coherent beam, which prevents full diffraction data sets from being acquired. A solution is provided here to overcome this problem and extend the size limit of the BCDI technique, through the design of a novel stabilization method by embedding the fine nanocrystals into a silica matrix. Chemically synthesized FePt nanocrystals of maximum dimension 20 nm and AuPd nanocrystals in the size range 60-65 nm were investigated with BCDI measurement at beamline 34-ID-C of the APS, Argonne National Laboratory. Novel experimental methodologies to elucidate the presence of strain in fine nanocrystals are a necessary pre-requisite in order to better understand strain profiles in engineered nanocrystals for novel device development.

  12. Diamond thin film temperature and heat-flux sensors

    NASA Technical Reports Server (NTRS)

    Aslam, M.; Yang, G. S.; Masood, A.; Fredricks, R.

    1995-01-01

    Diamond film temperature and heat-flux sensors are developed using a technology compatible with silicon integrated circuit processing. The technology involves diamond nucleation, patterning, doping, and metallization. Multi-sensor test chips were designed and fabricated to study the thermistor behavior. The minimum feature size (device width) for 1st and 2nd generation chips are 160 and 5 micron, respectively. The p-type diamond thermistors on the 1st generation test chip show temperature and response time ranges of 80-1270 K and 0.29-25 microseconds, respectively. An array of diamond thermistors, acting as heat flux sensors, was successfully fabricated on an oxidized Si rod with a diameter of 1 cm. Some problems were encountered in the patterning of the Pt/Ti ohmic contacts on the rod, due mainly to the surface roughness of the diamond film. The use of thermistors with a minimum width of 5 micron (to improve the spatial resolution of measurement) resulted in lithographic problems related to surface roughness of diamond films. We improved the mean surface roughness from 124 nm to 30 nm by using an ultra high nucleation density of 10(exp 11)/sq cm. To deposit thermistors with such small dimensions on a curved surface, a new 3-D diamond patterning technique is currently under development. This involves writing a diamond seed pattern directly on the curved surface by a computer-controlled nozzle.

  13. Diamond tool machining of materials which react with diamond

    DOEpatents

    Lundin, Ralph L.; Stewart, Delbert D.; Evans, Christopher J.

    1992-01-01

    Apparatus for the diamond machining of materials which detrimentally react with diamond cutting tools in which the cutting tool and the workpiece are chilled to very low temperatures. This chilling halts or retards the chemical reaction between the workpiece and the diamond cutting tool so that wear rates of the diamond tool on previously detrimental materials are comparable with the diamond turning of materials which do not react with diamond.

  14. Diamond tool machining of materials which react with diamond

    DOEpatents

    Lundin, R.L.; Stewart, D.D.; Evans, C.J.

    1992-04-14

    An apparatus is described for the diamond machining of materials which detrimentally react with diamond cutting tools in which the cutting tool and the workpiece are chilled to very low temperatures. This chilling halts or retards the chemical reaction between the workpiece and the diamond cutting tool so that wear rates of the diamond tool on previously detrimental materials are comparable with the diamond turning of materials which do not react with diamond. 1 figs.

  15. Nanocrystal Solar Cells

    SciTech Connect

    Gur, Ilan

    2006-01-01

    This dissertation presents the results of a research agenda aimed at improving integration and stability in nanocrystal-based solar cells through advances in active materials and device architectures. The introduction of 3-dimensional nanocrystals illustrates the potential for improving transport and percolation in hybrid solar cells and enables novel fabrication methods for optimizing integration in these systems. Fabricating cells by sequential deposition allows for solution-based assembly of hybrid composites with controlled and well-characterized dispersion and electrode contact. Hyperbranched nanocrystals emerge as a nearly ideal building block for hybrid cells, allowing the controlled morphologies targeted by templated approaches to be achieved in an easily fabricated solution-cast device. In addition to offering practical benefits to device processing, these approaches offer fundamental insight into the operation of hybrid solar cells, shedding light on key phenomena such as the roles of electrode-contact and percolation behavior in these cells. Finally, all-inorganic nanocrystal solar cells are presented as a wholly new cell concept, illustrating that donor-acceptor charge transfer and directed carrier diffusion can be utilized in a system with no organic components, and that nanocrystals may act as building blocks for efficient, stable, and low-cost thin-film solar cells.

  16. Solution-processable white-light-emitting germanium nanocrystals

    SciTech Connect

    Shirahata, Naoto

    2014-06-01

    This paper describes an efficient chemical route for the synthesis of visible light emitting nanocrystals of germanium (ncGe). The synthesis started by heating Ge(II) iodide at 300 °C in argon atmosphere. Spectroscopic characterizations confirmed the formation of diamond cubic lattice structures of ncGe. By grafting hydrophobic chains on the ncGe surface, the dispersions in nonpolar solvents of the ncGe became very stable. The as-synthesized ncGe showed the bluish white photoluminescence (PL) feature, but it was found that the PL spectrum is composed of many different emission spectra. Therefore, the color-tuning of white light emission is demonstrated through the witting removal of extra ncGe with unfavorable emission feature by making full use of column chromatographic techniques. - Highlights: • Visible light emitting nanocrystals of germanium was synthesized by chemical reduction of germanium iodide. • White light emission was achieved by control over size distribution of germanium nanocrystals. • Tuning the color of white light was achieved by separation of nanocrystals by emission.

  17. Heteroepitaxial Diamond Growth

    DTIC Science & Technology

    1992-11-01

    methyl radicals to a nickel (111) surface . The detailed results are contained in an attached copy of a recently published journal article, "Effects of...nucleation on surfaces which otherwise would not even nucleate diamond. The second area of research is devoted to the development of implant and...in explaining results of hydrogen dosing of diamond surfaces . Experimental results indicated that the dimmer bond on the diamond 2x1 surface was very

  18. A wear simulation study of nanostructured CVD diamond-on-diamond articulation involving concave/convex mating surfaces

    PubMed Central

    Baker, Paul A.; Thompson, Raymond G.; Catledge, Shane A.

    2015-01-01

    Using microwave-plasma Chemical Vapor Deposition (CVD), a 3-micron thick nanostructured-diamond (NSD) layer was deposited onto polished, convex and concave components that were machined from Ti-6Al-4V alloy. These components had the same radius of curvature, 25.4mm. Wear testing of the surfaces was performed by rotating articulation of the diamond-deposited surfaces (diamond-on-diamond) with a load of 225N for a total of 5 million cycles in bovine serum resulting in polishing of the diamond surface and formation of very shallow, linear wear grooves of less than 50nm depth. The two diamond surfaces remained adhered to the components and polished each other to an average surface roughness that was reduced by as much as a factor of 80 for the most polished region located at the center of the condyle. Imaging of the surfaces showed that the initial wearing-in phase of diamond was only beginning at the end of the 5 million cycles. Atomic force microscopy, scanning electron microscopy, Raman spectroscopy, and surface profilometry were used to characterize the surfaces and verify that the diamond remained intact and uniform over the surface, thereby protecting the underlying metal. These wear simulation results show that diamond deposition on Ti alloy has potential application for joint replacement devices with improved longevity over existing devices made of cobalt chrome and ultra-high molecular weight polyethylene (UHMWPE). PMID:26989457

  19. Diamond anvil technology

    NASA Astrophysics Data System (ADS)

    Seal, Michael

    This paper is largely a review of the techniques used in making diamond anvils and the constraints these put on the shapes of anvil. Techniques available for shaping diamonds include cleaving, sawing, polishing, laser cutting, and bruting. At present the shapes most commonly used for anvils are a modification of the brilliant cut derived from the gem industry, and a design based on an octagonal prism with truncated pyramidal top and base, known as the "Drukker standard design". Diamond orientation and material selection are considered as are future possibilities for the attainment of still higher pressures through modifications of the diamond anvil material or design.

  20. Infrared photoluminescence from GeSi nanocrystals embedded in a germanium–silicate matrix

    SciTech Connect

    Volodin, V. A. Gambaryan, M. P.; Cherkov, A. G.; Vdovin, V. I.; Stoffel, M.; Rinnert, H.; Vergnat, M.

    2015-12-15

    We investigate the structural and optical properties of GeO/SiO{sub 2} multilayers obtained by evaporation of GeO{sub 2} and SiO{sub 2} powders under ultrahigh vacuum conditions on Si(001) substrates. Both Raman and infrared absorption spectroscopy measurements indicate the formation of GeSi nanocrystals after postgrowth annealing at 800°C. High-resolution transmission electron microscopy characterizations show that the average size of the nanocrystals is about 5 nm. For samples containing GeSi nanocrystals, photoluminescence is observed at 14 K in the spectral range 1500–1600 nm. The temperature dependence of the photoluminescence is studied.

  1. Effects of PEGylated paclitaxel nanocrystals on breast cancer and its lung metastasis

    NASA Astrophysics Data System (ADS)

    Zhang, Hua; Hu, Hongxiang; Zhang, Haoran; Dai, Wenbing; Wang, Xinglin; Wang, Xueqing; Zhang, Qiang

    2015-06-01

    As an attractive strategy developed rapidly in recent years, nanocrystals are used to deliver insoluble drugs. PEGylation may further prolong the circulation time of nanoparticles and improve the therapeutic outcome of drugs. In this study, paclitaxel (PTX) nanocrystals (PTX-NCs) and PEGylated PTX nanocrystals (PEG-PTX-NCs) were prepared using antisolvent precipitation augmented by probe sonication. The characteristics and antitumor efficacy of nanocrystals were investigated. The results indicated that the nanocrystals showed rod-like morphology, and the average particle size was 240 nm and 330 nm for PTX-NCs and PEG-PTX-NCs, respectively. The PEG molecules covered the surface of nanocrystals with an 11.54 nm fixed aqueous layer thickness (FALT), much higher than that of PTX-NCs (0.2 nm). PEG-PTX-NCs showed higher stability than PTX-NCs under both storage and physiological conditions. In breast cancer xenografted mice, PEG-PTX-NCs showed significantly better tumor inhibition compared to saline (p < 0.001) and PTX-NC groups (p < 0.05) after intravenous administration. In a model of lung tumor metastasis quantified by the luciferase activity, the PEG-PTX-NCs group showed higher anticancer efficacy not only than saline and PTX-NCs groups, but also than Taxol®, achieving an 82% reduction at the end of the experiment. These studies suggested the potential advantages of PEGylated PTX nanocrystals as alternative drug delivery systems for anticancer therapy.

  2. Ultra thin CVD diamond film deposition by electrostatic self-assembly seeding process with nano-diamond particles.

    PubMed

    Kim, J H; Lee, S K; Kwon, O M; Lim, D S

    2009-07-01

    Ultra thin and smooth nano crystalline diamond films were fabricated with electrostatic self-assembly seeding of explosively synthesized nano-diamond particles. Hard aggregates of nano-diamond particles were crushed by high revolution attrition milling at 1000 RPM to regulate the particle size. Through this process, cationic nano-diamond particles were coated with anionic PSS (poly sodium 4-styrene sulfonate) electrolytes. Anionic Si(100) substrate was coated with cationic PDDA (poly diallyldimethyl ammonium chloride) solution. Si(100)/PDDA/PSS/ND (nano-diamond) layer-by-layer structure was formed as a seeding layer by the simple dipping and rinsing of positively charged substrate into anionic PSS/nano-diamond solution. Throughout the seeding process, neither mechanical damage nor chemical attack was observed on the substrate. Every stage of this preparation was carried out at room temperature and pressure. The effect of attrition milling was determined by changing the milling time from 1 hr to 5 hrs. Through the attritional milling and monolayer formation of the nano-diamond, nucleation density was increased up to 3 x 10(11)/cm2. Typical hot filament chemical vapor deposition system was used to coat the diamond film on the ESA (electrostatic self-assembly) seeded Si(100) substrate. Although typical diamond deposition conditions (90 torr/1% CH4 in H2/800 degrees C) were maintained, ultra thin (< 100 nm) and continuous nano crystalline diamond films were deposited. Regardless of metallic or ceramic substrate, ESND (ESA Seeding of nano-diamond) process is applicable if the substrate has any charge. This simple nano technology based process ensures high thickness uniformity of diamond coating without visible edge effect.

  3. Morphology evolution of single-crystalline hematite nanocrystals: magnetically recoverable nanocatalysts for enhanced facet-driven photoredox activity.

    PubMed

    Patra, Astam K; Kundu, Sudipta K; Bhaumik, Asim; Kim, Dukjoon

    2016-01-07

    We have developed a new green chemical approach for the shape-controlled synthesis of single-crystalline hematite nanocrystals in aqueous medium. FESEM, HRTEM and SAED techniques were used to determine the morphology and crystallographic orientations of each nanocrystal and its exposed facets. PXRD and HRTEM techniques revealed that the nanocrystals are single crystalline in nature; twins and stacking faults were not detected in these nanocrystals. The structural, vibrational, and electronic spectra of these nanocrystals were highly dependent on their shape. Different shaped hematite nanocrystals with distinct crystallographic planes have been synthesized under similar reaction conditions, which can be desired as a model for the purpose of properties comparison with the nanocrystals prepared under different reaction conditions. Here we investigated the photocatalytic performance of these different shaped-nanocrystals for methyl orange degradation in the presence of white light (λ > 420 nm). In this study, we found that the density of surface Fe(3+) ions in particular facets was the key factor for the photocatalytic activity and was higher on the bitruncated-dodecahedron shape nanocrystals by coexposed {104}, {100} and {001} facets, attributing to higher catalytic activity. The catalytic activity of different exposed facet nanocrystals were as follows: {104} + {100} + {001} (bitruncated-dodecahedron) > {101} + {001} (bitruncated-octahedron) > {001} + {110} (nanorods) > {012} (nanocuboid) which provided the direct evidence of exposed facet-driven photocatalytic activity. The nanocrystals were easily recoverable using an external magnet and reused at least six times without significant loss of its catalytic activity.

  4. Superhard Diamond/tungsten Carbide Nanocomposites

    SciTech Connect

    Z Lin; J Zhang; B Li; L Wang; H Mao; R Hemley; Y Zhao

    2011-12-31

    We investigated the processing conditions of diamond/tungsten carbide (WC) composites using in situ synchrotron x-ray diffraction (XRD) and reactive sintering techniques at high pressure and high temperatures. The as-synthesized composites were characterized by synchrotron XRD, scanning electron microscopy, high-resolution transmission electron microscopy, and indentation hardness measurements. Through tuning of the reaction temperature and time, we produced fully reacted, well-sintered, and nanostructured diamond composites with Vickers hardness of about 55 GPa and the grain size of WC binding matrix smaller than 50 nm. A specific set of orientation relationships between WC and tungsten is identified to gain microstructural insight into the reaction mechanism between diamond and tungsten.

  5. Infrared emitting and photoconducting colloidal silver chalcogenide nanocrystal quantum dots from a silylamide-promoted synthesis.

    PubMed

    Yarema, Maksym; Pichler, Stefan; Sytnyk, Mykhailo; Seyrkammer, Robert; Lechner, Rainer T; Fritz-Popovski, Gerhard; Jarzab, Dorota; Szendrei, Krisztina; Resel, Roland; Korovyanko, Oleksandra; Loi, Maria Antonietta; Paris, Oskar; Hesser, Günter; Heiss, Wolfgang

    2011-05-24

    Here, we present a hot injection synthesis of colloidal Ag chalcogenide nanocrystals (Ag(2)Se, Ag(2)Te, and Ag(2)S) that resulted in exceptionally small nanocrystal sizes in the range between 2 and 4 nm. Ag chalcogenide nanocrystals exhibit band gap energies within the near-infrared spectral region, making these materials promising as environmentally benign alternatives to established infrared active nanocrystals containing toxic metals such as Hg, Cd, and Pb. We present Ag(2)Se nanocrystals in detail, giving size-tunable luminescence with quantum yields above 1.7%. The luminescence, with a decay time on the order of 130 ns, was shown to improve due to the growth of a monolayer thick ZnSe shell. Photoconductivity with a quantum efficiency of 27% was achieved by blending the Ag(2)Se nanocrystals with a soluble fullerene derivative. The co-injection of lithium silylamide was found to be crucial to the synthesis of Ag chalcogenide nanocrystals, which drastically increased their nucleation rate even at relatively low growth temperatures. Because the same observation was made for the nucleation of Cd chalcogenide nanocrystals, we conclude that the addition of lithium silylamide might generally promote wet-chemical synthesis of metal chalcogenide nanocrystals, including in as-yet unexplored materials.

  6. An attempt to cast light into starch nanocrystals preparation and cross-linking.

    PubMed

    Jivan, Mehdi Jalali; Madadlou, Ashkan; Yarmand, Mohamadsaeed

    2013-12-01

    Potato starch was hydrolyzed with 2.2 or 3.7 M hydrochloric acid in order to obtain the nanocrystals which afterwards were chemically cross-linked with sodium hexametaphosphate. The stronger acidity resulted in smaller nanocrystals with mean size of 48 nm in a shorter time. X-ray diffraction confirmed the dominant crystalline nature of particles and Fourier transform infrared spectroscopy suggested the presence of lower number of free hydroxyl groups in nanocrystals after cross-linking. Starch nanocrystals showed two distinctive differential scaning colorimetry endotherms at 26 and 125 °C, attributed to destruction of nanocrystals lattice and moblizing of each nanocrystal's structure, respectively. Cross-linking resulted in a tenacious spatial arrangement of nanocrystals, strengthening the crystals lattice against phase transitions induced by heating. Scanning electron microscopy images confirmed the particle size measured for nanocrystals by light scattering. Atomic force microscopy topographic images suggested that starch nanocrystals were originated from small amylopectin blocklets in granular assembly of starch.

  7. Diamond photonics platform enabled by femtosecond laser writing

    PubMed Central

    Sotillo, Belén; Bharadwaj, Vibhav; Hadden, J. P.; Sakakura, Masaaki; Chiappini, Andrea; Fernandez, Toney Teddy; Longhi, Stefano; Jedrkiewicz, Ottavia; Shimotsuma, Yasuhiko; Criante, Luigino; Osellame, Roberto; Galzerano, Gianluca; Ferrari, Maurizio; Miura, Kiyotaka; Ramponi, Roberta; Barclay, Paul E.; Eaton, Shane Michael

    2016-01-01

    Diamond is a promising platform for sensing and quantum processing owing to the remarkable properties of the nitrogen-vacancy (NV) impurity. The electrons of the NV center, largely localized at the vacancy site, combine to form a spin triplet, which can be polarized with 532 nm laser light, even at room temperature. The NV’s states are isolated from environmental perturbations making their spin coherence comparable to trapped ions. An important breakthrough would be in connecting, using waveguides, multiple diamond NVs together optically. However, still lacking is an efficient photonic fabrication method for diamond akin to the photolithographic methods that have revolutionized silicon photonics. Here, we report the first demonstration of three dimensional buried optical waveguides in diamond, inscribed by focused femtosecond high repetition rate laser pulses. Within the waveguides, high quality NV properties are observed, making them promising for integrated magnetometer or quantum information systems on a diamond chip. PMID:27748428

  8. Electronic structure studies of nanocrystalline diamond grain boundaries

    SciTech Connect

    Zapol, P.; Sternberg, M.; Frauenheim, T.; Gruen, D. M.; Curtiss, L. A.

    1999-11-29

    Diamond growth from hydrogen-poor plasmas results in diamond structures that are profoundly different from conventionally CVD-grown diamond. High concentration of carbon dimers in the microwave plasma results in a high rate of heterogeneous renucleation leading to formation of nanocrystalline diamond with a typical grain size of 3--10 nm. Therefore, up to 10% of carbon atoms are located in the grain boundaries. In this paper the authors report on density-functional based tight-binding molecular dynamics calculations of the structure of a {Sigma}13 twist (100) grain boundary in diamond. Beginning with a coincidence site lattice model, simulated annealing of the initial structure was performed at 1,500 K followed by relaxation toward lower temperatures. About one-half of the carbons in the grain boundary are found to be three-coordinated. Coordination numbers, bond length and bond angle distributions are analyzed and compared to those obtained in previous studies.

  9. Diamond photonics platform enabled by femtosecond laser writing

    NASA Astrophysics Data System (ADS)

    Sotillo, Belén; Bharadwaj, Vibhav; Hadden, J. P.; Sakakura, Masaaki; Chiappini, Andrea; Fernandez, Toney Teddy; Longhi, Stefano; Jedrkiewicz, Ottavia; Shimotsuma, Yasuhiko; Criante, Luigino; Osellame, Roberto; Galzerano, Gianluca; Ferrari, Maurizio; Miura, Kiyotaka; Ramponi, Roberta; Barclay, Paul E.; Eaton, Shane Michael

    2016-10-01

    Diamond is a promising platform for sensing and quantum processing owing to the remarkable properties of the nitrogen-vacancy (NV) impurity. The electrons of the NV center, largely localized at the vacancy site, combine to form a spin triplet, which can be polarized with 532 nm laser light, even at room temperature. The NV’s states are isolated from environmental perturbations making their spin coherence comparable to trapped ions. An important breakthrough would be in connecting, using waveguides, multiple diamond NVs together optically. However, still lacking is an efficient photonic fabrication method for diamond akin to the photolithographic methods that have revolutionized silicon photonics. Here, we report the first demonstration of three dimensional buried optical waveguides in diamond, inscribed by focused femtosecond high repetition rate laser pulses. Within the waveguides, high quality NV properties are observed, making them promising for integrated magnetometer or quantum information systems on a diamond chip.

  10. Effect of location of Si or Ge nanocrystals on the memory behavior of MNOS structures

    NASA Astrophysics Data System (ADS)

    Horváth, Zs. J.; Basa, P.; Molnár, K. Z.; Molnár, Gy.; Jászi, T.; Pap, A. E.

    2013-06-01

    Charge injection and retention behaviors of metal-nitride-oxide-silicon (MNOS) memory structures with Si or Ge nanocrystals embedded at a depth of 3 nm in the nitride layer were studied. The effect of Si nanocrystals on these properties was opposite in comparison with that of Ge nanocrystals. To understand the origin of these opposite effects, the influence of the oxide thickness and of the depth, size and location of semiconductor nanocrystals has been studied on the charging behavior of MNOS non-volatile memory structures by the calculation of electron and hole tunneling probabilities, and by the simulation of memory window, memory hysteresis and retention behavior. For MNOS structures it is obtained that the presence of nanocrystals enhances the charge injection resulting in better performance, but only for structures with thin tunnel oxide layer (below 3 nm), and if the nanocrystals are located close to the oxide/nitride interface. In the case of very high tunneling probability, i.e., of high tunneling currents the system approaches equilibrium and the memory behavior collapses. There is a narrow range of oxide thickness or depth of nanocrystals, where the charging properties change very fast. Retention exhibits a very sharp dependence on the oxide thickness and on depth of nanocrystals as well. Most part of the experimental results can be explained on the basis of the results of simulations.

  11. Active Electrochemical Plasmonic Switching on Polyaniline-Coated Gold Nanocrystals.

    PubMed

    Lu, Wenzheng; Jiang, Nina; Wang, Jianfang

    2017-02-01

    High-performance electrochemical plasmonic switching is realized on both single-particle and ensemble levels by coating polyaniline on colloidal gold nanocrystals through surfactant-assisted oxidative polymerization. Under small applied potentials, the core@shell nanostructures exhibit reversible plasmon shifts as large as 150 nm, a switching time of less than 10 ms, and a high switching stability.

  12. Synthesis of nanocrystals and nanocrystal self-assembly

    NASA Astrophysics Data System (ADS)

    Chen, Zhuoying

    Chapter 1. A general introduction is presented on nanomaterials and nanoscience. Nanoparticles are discussed with respect to their structure and properties. Ferroelectric materials and nanoparticles in particular are highlighted, especially in the case of the barium titanate, and their potential applications are discussed. Different nanocrystal synthetic techniques are discussed. Nanoparticle superlattices, the novel "meta-materials" built from self-assembly at the nanoscale, are introduced. The formation of nanoparticle superlattices and the importance and interest of synthesizing these nanostructures is discussed. Chapter 2. Advanced applications for high k dielectric and ferroelectric materials in the electronics industry continues to demand an understanding of the underlying physics in decreasing dimensions into the nanoscale. The first part of this chapter presents the synthesis, processing, and electrical characterization of nanostructured thin films (thickness ˜100 nm) of barium titanate BaTiO3 built from uniform nanoparticles (<20 nm in diameter) in diameter. Essential to our approach is an understanding of the nanoparticle as a building block, combined with an ability to integrate them into thin films that have uniform and characteristic electrical properties. We observe the BaTiO3 nanocrystals crystallize with evidence of tetragonality. Electric field dependent polarization measurements show spontaneous polarization and hysteresis, indicating ferroelectric behavior for the BaTiO 3 nanocrystalline films with grain sizes in the range of 10--30 nm. Dielectric measurements of the films show dielectic constants in the range of 85--90 over the 1 kHz--100 kHz, with low loss. We present nanocrystals as initial building blocks for the preparation of thin films which exhibit uniform nanostructured morphologies and grain sizes. In the second part of this chapter, a nonhydrolytic alcoholysis route to study the preparation of well-crystallized size-tunable BaTiO3

  13. Superconductivity in diamond.

    PubMed

    Ekimov, E A; Sidorov, V A; Bauer, E D; Mel'nik, N N; Curro, N J; Thompson, J D; Stishov, S M

    2004-04-01

    Diamond is an electrical insulator well known for its exceptional hardness. It also conducts heat even more effectively than copper, and can withstand very high electric fields. With these physical properties, diamond is attractive for electronic applications, particularly when charge carriers are introduced (by chemical doping) into the system. Boron has one less electron than carbon and, because of its small atomic radius, boron is relatively easily incorporated into diamond; as boron acts as a charge acceptor, the resulting diamond is effectively hole-doped. Here we report the discovery of superconductivity in boron-doped diamond synthesized at high pressure (nearly 100,000 atmospheres) and temperature (2,500-2,800 K). Electrical resistivity, magnetic susceptibility, specific heat and field-dependent resistance measurements show that boron-doped diamond is a bulk, type-II superconductor below the superconducting transition temperature T(c) approximately 4 K; superconductivity survives in a magnetic field up to Hc2(0) > or = 3.5 T. The discovery of superconductivity in diamond-structured carbon suggests that Si and Ge, which also form in the diamond structure, may similarly exhibit superconductivity under the appropriate conditions.

  14. Diamond nucleation using polyethene

    SciTech Connect

    Morell, Gerardo; Makarov, Vladimir; Varshney, Deepak; Weiner, Brad

    2013-07-23

    The invention presents a simple, non-destructive and non-abrasive method of diamond nucleation using polyethene. It particularly describes the nucleation of diamond on an electrically viable substrate surface using polyethene via chemical vapor deposition (CVD) technique in a gaseous environment.

  15. Diamond Nucleation Using Polyethene

    NASA Technical Reports Server (NTRS)

    Morell, Gerardo (Inventor); Makarov, Vladimir (Inventor); Varshney, Deepak (Inventor); Weiner, Brad (Inventor)

    2013-01-01

    The invention presents a simple, non-destructive and non-abrasive method of diamond nucleation using polyethene. It particularly describes the nucleation of diamond on an electrically viable substrate surface using polyethene via chemical vapor deposition (CVD) technique in a gaseous environment.

  16. Diamond films: Historical perspective

    SciTech Connect

    Messier, R.

    1993-01-01

    This section is a compilation of notes and published international articles about the development of methods of depositing diamond films. Vapor deposition articles are included from American, Russian, and Japanese publications. The international competition to develop new deposition methodologies is stressed. The current status of chemical vapor deposition of diamond is assessed.

  17. Substitutional doping in nanocrystal superlattices

    NASA Astrophysics Data System (ADS)

    Cargnello, Matteo; Johnston-Peck, Aaron C.; Diroll, Benjamin T.; Wong, Eric; Datta, Bianca; Damodhar, Divij; Doan-Nguyen, Vicky V. T.; Herzing, Andrew A.; Kagan, Cherie R.; Murray, Christopher B.

    2015-08-01

    Doping is a process in which atomic impurities are intentionally added to a host material to modify its properties. It has had a revolutionary impact in altering or introducing electronic, magnetic, luminescent, and catalytic properties for several applications, for example in semiconductors. Here we explore and demonstrate the extension of the concept of substitutional atomic doping to nanometre-scale crystal doping, in which one nanocrystal is used to replace another to form doped self-assembled superlattices. Towards this goal, we show that gold nanocrystals act as substitutional dopants in superlattices of cadmium selenide or lead selenide nanocrystals when the size of the gold nanocrystal is very close to that of the host. The gold nanocrystals occupy random positions in the superlattice and their density is readily and widely controllable, analogous to the case of atomic doping, but here through nanocrystal self-assembly. We also show that the electronic properties of the superlattices are highly tunable and strongly affected by the presence and density of the gold nanocrystal dopants. The conductivity of lead selenide films, for example, can be manipulated over at least six orders of magnitude by the addition of gold nanocrystals and is explained by a percolation model. As this process relies on the self-assembly of uniform nanocrystals, it can be generally applied to assemble a wide variety of nanocrystal-doped structures for electronic, optical, magnetic, and catalytic materials.

  18. Oxide Nanocrystal Model Catalysts.

    PubMed

    Huang, Weixin

    2016-03-15

    Model catalysts with uniform and well-defined surface structures have been extensively employed to explore structure-property relationships of powder catalysts. Traditional oxide model catalysts are based on oxide single crystals and single crystal thin films, and the surface chemistry and catalysis are studied under ultrahigh-vacuum conditions. However, the acquired fundamental understandings often suffer from the "materials gap" and "pressure gap" when they are extended to the real world of powder catalysts working at atmospheric or higher pressures. Recent advances in colloidal synthesis have realized controlled synthesis of catalytic oxide nanocrystals with uniform and well-defined morphologies. These oxide nanocrystals consist of a novel type of oxide model catalyst whose surface chemistry and catalysis can be studied under the same conditions as working oxide catalysts. In this Account, the emerging concept of oxide nanocrystal model catalysts is demonstrated using our investigations of surface chemistry and catalysis of uniform and well-defined cuprous oxide nanocrystals and ceria nanocrystals. Cu2O cubes enclosed with the {100} crystal planes, Cu2O octahedra enclosed with the {111} crystal planes, and Cu2O rhombic dodecahedra enclosed with the {110} crystal planes exhibit distinct morphology-dependent surface reactivities and catalytic properties that can be well correlated with the surface compositions and structures of exposed crystal planes. Among these types of Cu2O nanocrystals, the octahedra are most reactive and catalytically active due to the presence of coordination-unsaturated (1-fold-coordinated) Cu on the exposed {111} crystal planes. The crystal-plane-controlled surface restructuring and catalytic activity of Cu2O nanocrystals were observed in CO oxidation with excess oxygen. In the propylene oxidation reaction with O2, 1-fold-coordinated Cu on Cu2O(111), 3-fold-coordinated O on Cu2O(110), and 2-fold-coordinated O on Cu2O(100) were identified

  19. Laser structuring of the diamond surface in the nanoablation regime

    NASA Astrophysics Data System (ADS)

    Gololobov, V. M.; Kononenko, V. V.; Konov, V. I.

    2016-12-01

    The possibility of using nanoablation (graphitisation-free photoinduced etching) for precise micro- and nanostructuring of the surface of a diamond single crystal has been experimentally investigated. The processing has been performed by femtosecond third-harmonic pulses of a Ti : sapphire laser (λ = 266 {\\text{nm}}). The specific features of the formation of a surface nanorelief (regularity of the newly formed structures and reduced nanoablation rate near craters) are discussed. The possibility of fabricating a diamond phase diffraction grating with a relief depth of ∼ 130 {\\text{nm}} is demonstrated and the diffraction pattern recorded at λ = 532 {\\text{nm}} is compared with the results of theoretical analysis.

  20. Color Centers in Silic On-Doped Diamond Films

    NASA Astrophysics Data System (ADS)

    Sedov, V. S.; Krivobok, V. S.; Khomich, A. V.; Ralchenko, V. G.; Khomich, A. A.; Martyanov, A. K.; Nikolaev, S. N.; Poklonskaya, O. N.; Konov, V. I.

    2016-05-01

    Silicon-doped microcrystalline diamond films of 1 μm thickness were grown by chemical vapor deposition in microwave plasma from mixtures of methane-hydrogen-silane on substrates of aluminum nitride, tungsten, and silicon. The diamond films were found to contain optically active silicon vacancy (SiV) centers giving rise to the 737-nm band in the photoluminescence spectra. The spectral features of a newly discovered narrow band of comparable intensity at 720-722 nm were studied. It is shown that the band at 720-722 nm occurs in the photoluminescence spectra only in the presence of silica in the diamond, regardless of the substrate material. The temperature dynamics of the photoluminescence spectra in the range of 5-294 K were investigated. The possible nature and mechanisms of formation of the color centers responsible for the 720-722 nm band are discussed.

  1. Germanium Nanocrystal Solar Cells

    NASA Astrophysics Data System (ADS)

    Holman, Zachary Charles

    Greenhouse gas concentrations in the atmosphere are approaching historically unprecedented levels from burning fossil fuels to meet the ever-increasing world energy demand. A rapid transition to clean energy sources is necessary to avoid the potentially catastrophic consequences of global warming. The sun provides more than enough energy to power the world, and solar cells that convert sunlight to electricity are commercially available. However, the high cost and low efficiency of current solar cells prevent their widespread implementation, and grid parity is not anticipated to be reached for at least 15 years without breakthrough technologies. Semiconductor nanocrystals (NCs) show promise for cheap multi-junction photovoltaic devices. To compete with photovoltaic materials that are currently commercially available, NCs need to be inexpensively cast into dense thin films with bulk-like electrical mobilities and absorption spectra that can be tuned by altering the NC size. The Group II-VI and IV-VI NC communities have had some success in achieving this goal by drying and then chemically treating colloidal particles, but the more abundant and less toxic Group IV NCs have proven more challenging. This thesis reports thin films of plasma-synthesized Ge NCs deposited using three different techniques, and preliminary solar cells based on these films. Germanium tetrachloride is dissociated in the presence of hydrogen in a nonthermal plasma to nucleate Ge NCs. Transmission electron microscopy and X-ray diffraction indicate that the particles are nearly monodisperse (standard deviations of 10-15% the mean particle diameter) and the mean diameter can be tuned from 4-15 nm by changing the residence time of the Ge NCs in the plasma. In the first deposition scheme, a Ge NC colloid is formed by reacting nanocrystalline powder with 1-dodecene and dispersing the functionalized NCs in a solvent. Films are then formed on substrates by drop-casting the colloid and allowing it to dry

  2. Alkyl passivation and amphiphilic polymer coating of silicon nanocrystals for diagnostic imaging.

    PubMed

    Hessel, Colin M; Rasch, Michael R; Hueso, Jose L; Goodfellow, Brian W; Akhavan, Vahid A; Puvanakrishnan, Priyaveena; Tunnel, James W; Korgel, Brian A

    2010-09-20

    A method to produce biocompatible polymer-coated silicon nanocrystals for medical imaging is shown. Silica-embedded Si nanocrystals are formed by HSQ thermolysis. The nanocrystals are then liberated from the oxide and terminated with Si-H bonds by HF etching, followed by alkyl monolayer passivation by thermal hydrosilylation. The Si nanocrystals have an average diameter of 2.1 nm ± 0.6 nm and photoluminesce with a peak emission wavelength of 650 nm, which lies within the transmission window of 650-900 nm that is useful for biological imaging. The hydrophobic Si nanocrystals are then coated with an amphiphilic polymer for dispersion in aqueous media with the pH ranging between 7 and 10 and an ionic strength between 30 mM and 2 M, while maintaining a bright and stable photoluminescence and a hydrodynamic radius of only 20 nm. Fluorescence imaging of polymer-coated Si nanocrystals in biological tissue is demonstrated, showing the potential for in vivo imaging.

  3. Controllable Synthesis of Monodisperse Er3+-Doped Lanthanide Oxyfluorides Nanocrystals with Intense Mid-Infrared Emission

    PubMed Central

    He, Huilin; Liu, Qiang; Yang, Dandan; Pan, Qiwen; Qiu, Jianrong; Dong, Guoping

    2016-01-01

    Monodisperse lanthanide oxyfluorides LnOF (Ln = Gd, Y) with mid-infrared emissions were controllably synthesized via a mild co-precipitation route and a subsequent heat-treatment. The detailed composition and morphology were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and high resolution transmission electron microscopy (HRTEM). The results showed that monodisperse GdOF:Er3+ were nano-riced shape with length about 350 nm and width about 120 nm, while the quasi-spherical YOF:Er3+ were uniform nanocrystals with an average size around 100 nm. The influence of calcination temperature on the size and phase transition of LnOF nanocrystals was also investigated. The photoluminescence (PL) spectra indicated that the 2.7 μm emission of Er3+ had achieved in both GdOF and YOF nanocrystals, which were calcined at different temperatures. In addition, the decay time of both 4I13/2 and 4I13/2 energy levels corresponding to Er3+ in YOF nanocrystals were also studied in detail. The results suggested that both rice-shaped GdOF nanocrystals and YOF nanocrystals could provide suitable candidate materials for nanocrystals-glass composites, which could be a step forward to the realization of mid-infrared laser materials. PMID:27748411

  4. Controllable Synthesis of Monodisperse Er3+-Doped Lanthanide Oxyfluorides Nanocrystals with Intense Mid-Infrared Emission

    NASA Astrophysics Data System (ADS)

    He, Huilin; Liu, Qiang; Yang, Dandan; Pan, Qiwen; Qiu, Jianrong; Dong, Guoping

    2016-10-01

    Monodisperse lanthanide oxyfluorides LnOF (Ln = Gd, Y) with mid-infrared emissions were controllably synthesized via a mild co-precipitation route and a subsequent heat-treatment. The detailed composition and morphology were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and high resolution transmission electron microscopy (HRTEM). The results showed that monodisperse GdOF:Er3+ were nano-riced shape with length about 350 nm and width about 120 nm, while the quasi-spherical YOF:Er3+ were uniform nanocrystals with an average size around 100 nm. The influence of calcination temperature on the size and phase transition of LnOF nanocrystals was also investigated. The photoluminescence (PL) spectra indicated that the 2.7 μm emission of Er3+ had achieved in both GdOF and YOF nanocrystals, which were calcined at different temperatures. In addition, the decay time of both 4I13/2 and 4I13/2 energy levels corresponding to Er3+ in YOF nanocrystals were also studied in detail. The results suggested that both rice-shaped GdOF nanocrystals and YOF nanocrystals could provide suitable candidate materials for nanocrystals-glass composites, which could be a step forward to the realization of mid-infrared laser materials.

  5. Nanofocusing optics for synchrotron radiation made from polycrystalline diamond.

    PubMed

    Fox, O J L; Alianelli, L; Malik, A M; Pape, I; May, P W; Sawhney, K J S

    2014-04-07

    Diamond possesses many extreme properties that make it an ideal material for fabricating nanofocusing x-ray optics. Refractive lenses made from diamond are able to focus x-ray radiation with high efficiency but without compromising the brilliance of the beam. Electron-beam lithography and deep reactive-ion etching of silicon substrates have been used in a transfer-molding technique to fabricate diamond optics with vertical and smooth sidewalls. Latest generation compound refractive lenses have seen an improvement in the quality and uniformity of the optical structures, resulting in an increase in their focusing ability. Synchrotron beamline tests of two recent lens arrays, corresponding to two different diamond morphologies, are described. Focal line-widths down to 210 nm, using a nanocrystalline diamond lens array and a beam energy of E = 11 keV, and 230 nm, using a microcrystalline diamond lens at E = 15 keV, have been measured using the Diamond Light Source Ltd. B16 beamline. This focusing prowess is combined with relatively high transmission through the lenses compared with silicon refractive designs and other diffractive optics.

  6. Ion-Implanted Diamond Films and Their Tribological Properties

    NASA Technical Reports Server (NTRS)

    Wu, Richard L. C.; Miyoshi, Kazuhisa; Korenyi-Both, Andras L.; Garscadden, Alan; Barnes, Paul N.

    1993-01-01

    This paper reports the physical characterization and tribological evaluation of ion-implanted diamond films. Diamond films were produced by microwave plasma, chemical vapor deposition technique. Diamond films with various grain sizes (0.3 and 3 microns) and roughness (9.1 and 92.1 nm r.m.s. respectively) were implanted with C(+) (m/e = 12) at an ion energy of 160 eV and a fluence of 6.72 x 10(exp 17) ions/sq cm. Unidirectional sliding friction experiments were conducted in ultrahigh vacuum (6.6 x 10(exp -7)Pa), dry nitrogen and humid air (40% RH) environments. The effects of C(+) ion bombardment on fine and coarse-grained diamond films are as follows: the surface morphology of the diamond films did not change; the surface roughness increased (16.3 and 135.3 nm r.m.s.); the diamond structures were damaged and formed a thin layer of amorphous non-diamond carbon; the friction coefficients dramatically decreased in the ultrahigh vacuum (0.1 and 0.4); the friction coefficients decreased slightly in the dry nitrogen and humid air environments.

  7. Single-color centers implanted in diamond nanostructures

    NASA Astrophysics Data System (ADS)

    Hausmann, Birgit J. M.; Babinec, Thomas M.; Choy, Jennifer T.; Hodges, Jonathan S.; Hong, Sungkun; Bulu, Irfan; Yacoby, Amir; Lukin, Mikhail D.; Lončar, Marko

    2011-04-01

    The development of material-processing techniques that can be used to generate optical diamond nanostructures containing a single-color center is an important problem in quantum science and technology. In this work, we present the combination of ion implantation and top-down diamond nanofabrication in two scenarios: diamond nanopillars and diamond nanowires. The first device consists of a 'shallow' implant (~20 nm) to generate nitrogen-vacancy (NV) color centers near the top surface of the diamond crystal prior to device fabrication. Individual NV centers are then mechanically isolated by etching a regular array of nanopillars in the diamond surface. Photon anti-bunching measurements indicate that a high yield (>10%) of the devices contain a single NV center. The second device demonstrates 'deep' (~1 μm) implantation of individual NV centers into diamond nanowires as a post-processing step. The high single-photon flux of the nanowire geometry, combined with the low background fluorescence of the ultrapure diamond, allowed us to observe sustained photon anti-bunching even at high pump powers.

  8. Analyzing the performance of diamond-coated micro end mills.

    SciTech Connect

    Torres, C. D.; Heaney, P. J.; Sumant, A. V.; Hamilton, M. A.; Carpick, R. W.; Pfefferkorn, F. E.; Univ. of Wisconsin at Madison; Univ. of Pennsylvania

    2009-06-01

    A method is presented to improve the tool life and cutting performance of 300 {micro}m diameter tungsten carbide (WC) micro end mills by applying thin (<300 nm) fine-grained diamond (FGD) and nanocrystalline diamond (NCD) coatings using the hot-filament chemical vapor deposition (HF-CVD) process. The performance of the diamond-coated tools has been evaluated by comparing their performance in dry slot milling of 6061-T6 aluminum against uncoated WC micro end mills. Tool wear, coating integrity, and chip morphology were characterized using SEM and white light interferometry. The initial test results show a dramatic improvement in the tool integrity (i.e., corners not breaking off), a lower wear rate, no observable adhesion of aluminum to the diamond-coated tool, and a significant reduction in the cutting forces (>50%). Reduction of the cutting forces is attributed to the low friction and adhesion of the diamond coating. However, approximately 80% of the tools coated with the larger FGD coatings failed during testing due to delamination. Additional machining benefits were attained for the NCD films, which was obtained by using a higher nucleation density seeding process for diamond growth. This process allowed for thinner, smaller grained diamond coatings to be deposited on the micro end mills, and enabled continued operation of the tool even after the integrity of the diamond coating had been compromised. As opposed to the FGD-coated end mills, only 40% of the NCD-tools experienced delamination issues.

  9. Photochemical versus Thermal Synthesis of Cobalt Oxyhydroxide Nanocrystals

    SciTech Connect

    Alvarado, Samuel R.; Guo, Yijun; Ruberu, T. Purnima A.; Bakac, Andreja; Vela, Javier

    2012-04-18

    Photochemical methods facilitate the generation, isolation, and study of metastable nanomaterials having unusual size, composition, and morphology. These harder-to-isolate and highly reactive phases, inaccessible using conventional high-temperature pyrolysis, are likely to possess enhanced and unprecedented chemical, electromagnetic, and catalytic properties. We report a fast, low-temperature and scalable photochemical route to synthesize very small (3 nm) monodisperse cobalt oxyhydroxide (Co(O)OH) nanocrystals. This method uses readily and commercially available pentaamminechlorocobalt(III) chloride, [Co(NH3)5Cl]Cl2, under acidic or neutral pH and proceeds under either near-UV (350 nm) or Vis (575 nm) illumination. Control experiments showed that the reaction proceeds at competent rates only in the presence of light, does not involve a free radical mechanism, is insensitive to O2, and proceeds in two steps: (1) Aquation of [Co(NH3)5Cl]2+ to yield [Co(NH3)5(H2O)]3+, followed by (2) slow photoinduced release of NH3 from the aqua complex. This reaction is slow enough for Co(O)OH to form but fast enough so that nanocrystals are small (ca. 3 nm). The alternative dark thermal reaction proceeds much more slowly and produces much larger (250 nm) polydisperse Co(O)OH aggregates. UV–Vis absorption measurements and ab initio calculations yield a Co(O)OH band gap of 1.7 eV. Fast thermal annealing of Co(O)OH nanocrystals leads to Co3O4 nanocrystals with overall retention of nanoparticle size and morphology. Thermogravimetric analysis shows that oxyhydroxide to mixed-oxide phase transition occurs at significantly lower temperatures (up to ΔT = 64 °C) for small nanocrystals compared with the bulk.

  10. Laser nanoablation of diamond surface at high pulse repetition rates

    NASA Astrophysics Data System (ADS)

    Kononenko, V. V.; Gololobov, V. M.; Pashinin, V. P.; Konov, V. I.

    2016-10-01

    The chemical etching of the surface of a natural diamond single crystal irradiated by subpicosecond laser pulses with a high repetition rate (f ≤slant 500 {\\text{kHz}}) in air is experimentally investigated. The irradiation has been performed by the second-harmonic (515 {\\text{nm}}) radiation of a disk Yb : YAG laser. Dependences of the diamond surface etch rate on the laser energy density and pulse repetition rate are obtained.

  11. Brown diamonds from an eclogite xenolith from Udachnaya kimberlite, Yakutia, Russia.

    PubMed

    Stepanov, Aleksandr S; Korsakov, Andrey V; Yuryeva, Olga P; Nadolinniy, Vladimir A; Perraki, Maria; De Gussem, Kris; Vandenabeele, Peter

    2011-10-01

    We have performed petrographic and spectroscopic studies of brown diamonds from an eclogite xenolith from the Udachnaya pipe (Yakutia, Russia). Brown diamonds are randomly intermixed with colorless ones in the rock and often located at the grain boundaries of clinopyroxene and garnet. Brown diamonds can be characterized by a set of defects (H4, N2D and a line at 490.7 nm) which are absent in colorless diamonds. This set of defects is typical for plastically deformed diamonds and indicates that diamonds were likely annealed for a relatively short period after deformation had occurred. Excitation of brown colored zones with a 632.8 nm He-Ne laser produced the typical diamond band plus two additional bands at 1730 cm(-1) and 3350 cm(-1). These spectral features are not genuine Raman bands, and can be attributed to photoluminescence at ∼710 nm (1.75 eV) and ∼802 nm (1.54 eV). No Raman peak corresponding to graphite was observed in regions of brown coloration. Comparison with previous reports of brown diamonds from eclogites showed our eclogitic sample to have a typical structure without signs of apparent deformation. Two mechanisms with regard to diamond deformation are proposed: deformation of eclogite by external forces followed by subsequent recrystallization of silicates or, alternatively, deformation by local stress arising due to decompression and expansion of silicates during ascent of the xenolith to surface conditions.

  12. Calpain inhibitor nanocrystals prepared using Nano Spray Dryer B-90

    NASA Astrophysics Data System (ADS)

    Baba, Koichi; Nishida, Kohji

    2012-08-01

    The Nano Spray Dryer B-90 offers a new, simple, and alternative approach for the production of drug nanocrystals. Among attractive drugs, calpain inhibitor that inhibits programmed cell death `apoptosis' is a candidate for curing apoptosis-mediated intractable diseases such as Alzheimer's disease and Parkinson's disease. In this study, the preparation of calpain inhibitor nanocrystals using Nano Spray Dryer B-90 was demonstrated. The particle sizes were controlled by means of selecting mesh aperture sizes. The obtained average particle sizes were in the range of around 300 nm to submicron meter.

  13. Magnetization Reversal in Europium Sulfide Nanocrystals

    NASA Astrophysics Data System (ADS)

    Dickerson, James; Redigolo, Marcela; Koktysh, Dmitry; Rosenthal, Sandra; Gai, Zheng; Gao, Lan; Shen, Jian

    2007-03-01

    We report the observation of the reversal in the magnetization hysteresis curve of europium sulfide nanocrystals. This phenomenon was investigated through the temperature-dependent magnetization of two classes of nanomaterials, nanocrystalline (2.0 nm <= dNCs <= 100 nm), and quantum-confined (dNCs <= 2.0 nm), where dNCs is the diameter of the nanomaterial. The effect of the size of the nanomaterial on the magnetization is attributed to the competition between the magnetic properties of strained surface atoms and unstrained core atoms. Superconducting quantum interference device (SQUID) probed the magnetic response. Electron microscopy and X-ray diffraction spectroscopy revealed the crystallinity and monodispersivity of the nanomaterials.

  14. Effective optical Faraday rotations of semiconductor EuS nanocrystals with paramagnetic transition-metal ions.

    PubMed

    Hasegawa, Yasuchika; Maeda, Masashi; Nakanishi, Takayuki; Doi, Yoshihiro; Hinatsu, Yukio; Fujita, Koji; Tanaka, Katsuhisa; Koizumi, Hitoshi; Fushimi, Koji

    2013-02-20

    Novel EuS nanocrystals containing paramagnetic Mn(II), Co(II), or Fe(II) ions have been reported as advanced semiconductor materials with effective optical rotation under a magnetic field, Faraday rotation. EuS nanocrystals with transition-metal ions, EuS:M nanocrystals, were prepared by the reduction of the Eu(III) dithiocarbamate complex tetraphenylphosphonium tetrakis(diethyldithiocarbamate)europium(III) with transition-metal complexes at 300 °C. The EuS:M nanocrystals thus prepared were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma atomic emission spectroanalysis (ICP-AES), and a superconducting quantum interference device (SQUID) magnetometer. Enhanced Faraday rotations of the EuS:M nanocrystals were observed around 550 nm, and their enhanced spin polarization was estimated using electron paramagnetic resonance (EPR) measurements. In this report, the magneto-optical relationship between the Faraday rotation efficiency and spin polarization is discussed.

  15. Fabrication of multilayered Ge nanocrystals embedded in SiO xGeN y films

    NASA Astrophysics Data System (ADS)

    Gao, Fei; Green, Martin A.; Conibeer, Gavin; Cho, Eun-Chel; Huang, Yidan; Perez-Wurfl, Ivan; Flynn, Chris

    2008-09-01

    Multilayered Ge nanocrystals embedded in SiO xGeN y films have been fabricated on Si substrate by a (Ge + SiO 2)/SiO xGeN y superlattice approach, using a rf magnetron sputtering technique with a Ge + SiO 2 composite target and subsequent thermal annealing in N 2 ambient at 750 °C for 30 min. X-ray diffraction (XRD) measurement indicated the formation of Ge nanocrystals with an average size estimated to be 5.4 nm. Raman scattering spectra showed a peak of the Ge-Ge vibrational mode downward shifted to 299.4 cm -1, which was caused by quantum confinement of phonons in the Ge nanocrystals. Transmission electron microscopy (TEM) revealed that Ge nanocrystals were confined in (Ge + SiO 2) layers. This superlattice approach significantly improved both the size uniformity of Ge nanocrystals and their uniformity of spacing on the 'Z' growth direction.

  16. Ion beam synthesis and optical properties of semiconductor nanocrystals and quantum dots

    SciTech Connect

    Zhu, J.G.; White, C.W.; Withrow, S.P.

    1996-11-01

    Nanocrystals of semiconductor materials have been fabricated in SiO{sub 2} by ion implantation and subsequent thermal annealing. Strong red photoluminescence (PL) peaked around 750 nm has been observed in samples containing Si nanocrystals in SiO{sub 2}. The Si nanocrystals in the samples with optimized PL intensities are a few nanometers in diameter. Difference in the absorption bandgap energies and the PL peak energies are discussed. Significant influence of implantation sequence on the formation of compound semiconductor nanocrystals are demonstrated with the GaAs in the SiO{sub 2} system. Optical absorption measurements show that Ga particles have already formed in the as-implanted stage if Ga is implanted first. A single surface phonon mode has been observed in the infrared reflectance measurement from samples containing GaAs nanocrystals.

  17. Growth and stability of oxidation resistant Si nanocrystals formed by decomposition of alkyl silanes

    SciTech Connect

    Zaitseva, N; Hamel, S; Dai, Z R; Saw, C; Williamson, A J; Galli, G

    2007-01-12

    The synthesis and characterization of 1-10 nm Si nanocrystals highly resistant to oxidation is described. The nanocrystals were prepared by thermal decomposition of tetramethylsilane at 680 C, or in a gold- induced catalytic process at lower temperatures down to 400-450 C using trioctylamine as an initial solvent. Transmission electron microscopic analysis of samples obtained in the presence of gold show that the nanocrystals form via solid-phase epitaxial attachment of Si to the gold crystal lattice. The results of computational modeling performed using first principles density functional theory (DFT) calculations predict that the enhanced stability of nanocrystals to oxidation is due to the presence of N or N-containing groups on the surface of nanocrystals.

  18. High-Brightness Blue and White LEDs based on Inorganic Perovskite Nanocrystals and their Composites.

    PubMed

    Yao, En-Ping; Yang, Zhanlue; Meng, Lei; Sun, Pengyu; Dong, Shiqi; Yang, Ye; Yang, Yang

    2017-04-10

    Inorganic metal halide perovskite nanocrystals (NCs) have been employed universally in light-emitting applications during the past two years. Here, blue-emission (≈470 nm) Cs-based perovskite NCs are derived by directly mixing synthesized bromide and chloride nanocrystals with a weight ratio of 2:1. High-brightness blue perovskite light-emitting diodes (PeLEDs) are obtained by controlling the grain size of the perovskite films. Moreover, a white PeLED is demonstrated for the first time by blending orange polymer materials with the blue perovskite nanocrystals as the active layer. Exciton transfer from the blue nanocrystals to the orange polymers via Förster or Dexter energy transfer is analyzed through time resolved photoluminescence. By tuning the ratio between the perovskite nanocrystals and polymers, pure white light is achieved with the a CIE coordinate at (0.33,0.34).

  19. Chemical design of nanocrystal solids.

    PubMed

    Kovalenko, Maksym V

    2013-01-01

    This account highlights our recent and present activities dedicated to chemical synthesis and applications of inorganic nanostructures. In particular, we discuss the potential of metal amides as precursors in the synthesis of metallic and semiconductor nanocrystals. We show the importance of surface chemical functionalization for the emergence of collective electronic properties in nanocrystal solids. We also demonstrate a new kind of long-range ordered, crystalline matter comprising colloidal nanocrystals and atomically defined inorganic clusters. Finally, we point the reader's attention to the high potential benefits of size- and shape-tunability of nanocrystals for achieving higher performance of rechargeable Li-ion battery electrodes.

  20. Electronic states in spherical GaN nanocrystals embedded in various dielectric matrices: The k ⋅ p-calculations

    SciTech Connect

    Konakov, A. A. Filatov, D. O.; Korolev, D. S.; Belov, A. I.; Mikhaylov, A. N.; Tetelbaum, D. I.; Kumar, Mahesh

    2016-01-15

    Using the envelope-function approximation, the single-particle states of electrons and holes in spherical GaN nanocrystals embedded in different amorphous dielectric matrices (SiO{sub 2}, Al{sub 2}O{sub 3}, HfO{sub 2} and Si{sub 3}N{sub 4}) have been calculated. Ground state energies of electrons and holes in GaN nanocrystals are determined using the isotropic approximation of the k ⋅ p -Hamiltonian. All the ground state energies are found to increase with lowering the nanocrystal size and are proportional to the R{sup −n}, where R is the nanocrystal radius, n =1.5-1.9 for electrons and 1.7-2.0 for holes. The optical gap of GaN nanocrystals changes from 3.8 to 5 eV for the nanocrystal radius ranging from 3 to 1 nm.

  1. Controlled assembly and electronics in semiconductor nanocrystal-based devices

    NASA Astrophysics Data System (ADS)

    Drndic, Marija

    2006-03-01

    I will discuss the assembly of semiconductor nanocrystals (CdSe and PbSe) into electronic devices and the basic mechanisms of charge transport in nanocrystal arrays [1-4]. Spherical CdSe nanocrystals show robust memory effects that can be exploited for memory applications [1]. Nanocrystal memory can be erased electrically or optically and is rewritable. In PbSe nanocrystal arrays, as the interdot coupling is increased, the system evolves from an insulating regime dominated by Coulomb blockade to a semiconducting regime, where hopping conduction is the dominant transport mechanism [2]. Two-dimensional CdSe nanorod arrays show striking and anomalous transport properties, including strong and reproducible non-linearities and current oscillations with dc-voltage [4]. I will also discuss imaging of the charge transport in nanocrystal-based electronic devices. Nanocrystal arrays were investigated using electrostatic force microscopy (EFM) and transmission electron microscopy (TEM) [3]. Changes in lattice and transport properties upon annealing in vacuum were revealed. Local charge transport was directly imaged by EFM and correlated to nanopatterns observed with TEM. This work shows how charge transport in complex nanocrystal networks can be identified with nm resolution [3]. This work was supported by the ONR grant N000140410489, the NSF grants DMR-0449553 and MRSEC DMR00-79909, and the ACS PRF grant 41256-G10. References:1) Fischbein M. D. and Drndic M., ``CdSe nanocrystal quantum-dot memory,'' Applied Physics Letters, 86 (19), 193106, 2005.2) H. E. Romero and Drndic M., ``Coulomb blockade and hopping conduction in PbSe quantum dots,'' Physical Review Letters 95, 156801, 2005.3) Hu Z., Fischbein M. D. and Drndic M., ``Local charge transport in two-dimensional PbSe nanocrystal arrays studied by electrostatic force microscopy",'' Nano Letters 5 (7), 1463, 2005.4) Romero H.E., Calusine G. and Drndic M., ``Current oscillations, switching and hysteresis in CdSe nanorod

  2. Synthesis and characterization of luminescent aluminium selenide nanocrystals

    SciTech Connect

    Balitskii, O.A.; Demchenko, P.Yu.; Mijowska, E.; Cendrowski, K.

    2013-02-15

    Highlights: ► Synthesis procedure of size and sharp controlled Al{sub 2}Se{sub 3} nanocrystals is introduced. ► Obtained nanoparticles are highly crystalline of hexagonal wurtzite type. ► Colloidal Al{sub 2}Se{sub 3} nanocrystals are highly luminescent in the near UV spectral region. ► They can be implemented in light emitters/collectors, concurring with II–VI nanodots. -- Abstract: We propose the synthesis and characterization of colloidal aluminium selenide nanocrystals using trioctylphosphine as a solvent. The nanoparticles have several absorption bands in the spectral region 330–410 nm and are bright UV-blue luminescent, which is well demanded in light collecting and emitting devices, e.g. for tuning their spectral characteristics to higher energy solar photons.

  3. Seeded Growth Route to Noble Calcium Carbonate Nanocrystal

    PubMed Central

    Islam, Aminul; Teo, Siow Hwa; Rahman, M. Aminur; Taufiq-Yap, Yun Hin

    2015-01-01

    A solution-phase route has been considered as the most promising route to synthesize noble nanostructures. A majority of their synthesis approaches of calcium carbonate (CaCO3) are based on either using fungi or the CO2 bubbling methods. Here, we approached the preparation of nano-precipitated calcium carbonate single crystal from salmacis sphaeroides in the presence of zwitterionic or cationic biosurfactants without external source of CO2. The calcium carbonate crystals were rhombohedron structure and regularly shaped with side dimension ranging from 33–41 nm. The high degree of morphological control of CaCO3 nanocrystals suggested that surfactants are capable of strongly interacting with the CaCO3 surface and control the nucleation and growth direction of calcium carbonate nanocrystals. Finally, the mechanism of formation of nanocrystals in light of proposed routes was also discussed. PMID:26700479

  4. Seeded Growth Route to Noble Calcium Carbonate Nanocrystal.

    PubMed

    Islam, Aminul; Teo, Siow Hwa; Rahman, M Aminur; Taufiq-Yap, Yun Hin

    2015-01-01

    A solution-phase route has been considered as the most promising route to synthesize noble nanostructures. A majority of their synthesis approaches of calcium carbonate (CaCO3) are based on either using fungi or the CO2 bubbling methods. Here, we approached the preparation of nano-precipitated calcium carbonate single crystal from salmacis sphaeroides in the presence of zwitterionic or cationic biosurfactants without external source of CO2. The calcium carbonate crystals were rhombohedron structure and regularly shaped with side dimension ranging from 33-41 nm. The high degree of morphological control of CaCO3 nanocrystals suggested that surfactants are capable of strongly interacting with the CaCO3 surface and control the nucleation and growth direction of calcium carbonate nanocrystals. Finally, the mechanism of formation of nanocrystals in light of proposed routes was also discussed.

  5. Nanocrystal waveguide (NOW) laser

    DOEpatents

    Simpson, John T.; Simpson, Marcus L.; Withrow, Stephen P.; White, Clark W.; Jaiswal, Supriya L.

    2005-02-08

    A solid state laser includes an optical waveguide and a laser cavity including at least one subwavelength mirror disposed in or on the optical waveguide. A plurality of photoluminescent nanocrystals are disposed in the laser cavity. The reflective subwavelength mirror can be a pair of subwavelength resonant gratings (SWG), a pair of photonic crystal structures (PC), or a distributed feedback structure. In the case of a pair of mirrors, a PC which is substantially transmissive at an operating wavelength of the laser can be disposed in the laser cavity between the subwavelength mirrors to improve the mode structure, coherence and overall efficiency of the laser. A method for forming a solid state laser includes the steps of providing an optical waveguide, creating a laser cavity in the optical waveguide by disposing at least one subwavelength mirror on or in the waveguide, and positioning a plurality of photoluminescent nanocrystals in the laser cavity.

  6. PROCESS FOR COLORING DIAMONDS

    DOEpatents

    Dugdale, R.A.

    1960-07-19

    A process is given for coloring substantially colorless diamonds in the blue to blue-green range and comprises the steps of irradiating the colorless diamonds with electrons having an energy within the range 0.5 to 2 Mev to obtain an integrated electron flux of between 1 and 2 x 10/sup 18/ thc diamonds may be irradiated 1 hr when they take on a blue color with a slight green tint: After being heated at about 500 deg C for half an hour they become pure blue. Electrons within this energy range contam sufficient energy to displace the diamond atoms from their normal lattice sites into interstitial sites, thereby causing the color changes.

  7. Diamond Ranch High School.

    ERIC Educational Resources Information Center

    Betsky, Aaron

    2000-01-01

    Highlights award-winning Diamond Ranch High School (California) that was designed and built on a steep site around Los Angeles considered unsatisfactory for building due to its unstable soils. Building organization is discussed, and photos are provided. (GR)

  8. Amorphous diamond films

    DOEpatents

    Falabella, S.

    1998-06-09

    Amorphous diamond films having a significant reduction in intrinsic stress are prepared by biasing a substrate to be coated and depositing carbon ions thereon under controlled temperature conditions. 1 fig.

  9. Quantum engineering: Diamond envy

    NASA Astrophysics Data System (ADS)

    Nunn, Joshua

    2013-03-01

    Nitrogen atoms trapped tens of nanometres apart in diamond can now be linked by quantum entanglement. This ability to produce and control entanglement in solid systems could enable powerful quantum computers.

  10. Size-Dependent Melting Behavior of Colloidal In, Sn, and Bi Nanocrystals

    PubMed Central

    Liu, Minglu; Wang, Robert Y.

    2015-01-01

    Colloidal nanocrystals are a technologically important class of nanostructures whose phase change properties have been largely unexplored. Here we report on the melting behavior of In, Sn, and Bi nanocrystals dispersed in a polymer matrix. This polymer matrix prevents the nanocrystals from coalescing with one another and enables previously unaccessed observations on the melting behavior of colloidal nanocrystals. We measure the melting temperature, melting enthalpy, and melting entropy of colloidal nanocrystals with diameters of approximately 10 to 20 nm. All of these properties decrease as nanocrystal size decreases, although the depression rate for melting temperature is comparatively slower than that of melting enthalpy and melting entropy. We also observe an elevated melting temperature during the initial melt-freeze cycle that we attribute to surface stabilization from the organic ligands on the nanocrystal surface. Broad endothermic melting valleys and very large supercoolings in our calorimetry data suggest that colloidal nanocrystals exhibit a significant amount of surface pre-melting and low heterogeneous nucleation probabilities during freezing. PMID:26573146

  11. Atomically precise gold nanocrystal molecules with surface plasmon resonance.

    PubMed

    Qian, Huifeng; Zhu, Yan; Jin, Rongchao

    2012-01-17

    Since Faraday's pioneering work on gold colloids, tremendous scientific research on plasmonic gold nanoparticles has been carried out, but no atomically precise Au nanocrystals have been achieved. This work reports the first example of gold nanocrystal molecules. Mass spectrometry analysis has determined its formula to be Au(333)(SR)(79) (R = CH(2)CH(2)Ph). This magic sized nanocrystal molecule exhibits fcc-crystallinity and surface plasmon resonance at approximately 520 nm, hence, a metallic nanomolecule. Simulations have revealed that atomic shell closing largely contributes to the particular robustness of Au(333)(SR)(79), albeit the number of free electrons (i.e., 333 - 79 = 254) is also consistent with electron shell closing based on calculations using a confined free electron model. Guided by the atomic shell closing growth mode, we have also found the next larger size of extraordinarily stability to be Au(~530)(SR)(~100) after a size-focusing selection--which selects the robust size available in the starting polydisperse nanoparticles. This work clearly demonstrates that atomically precise nanocrystal molecules are achievable and that the factor of atomic shell closing contributes to their extraordinary stability compared to other sizes. Overall, this work opens up new opportunities for investigating many fundamental issues of nanocrystals, such as the formation of metallic state, and will have potential impact on condensed matter physics, nanochemistry, and catalysis as well.

  12. Synthesis of discrete aluminophosphate -CLO nanocrystals in a eutectic mixture.

    PubMed

    Tao, Shuo; Xu, Renshun; Li, Xiaolei; Li, Dawei; Ma, Huaijun; Wang, Donge; Xu, Yunpeng; Tian, Zhijian

    2015-08-01

    Extra-large-pore aluminophosphate -CLO (i.e., DNL-1) nanocrystals were synthesized in a eutectic mixture composed of diethylamine hydrochloride (DEAC) and ethylene glycol (EG) with 1-methylimidazole (1-MIm) as an additional amine using both conventional and microwave heating. The effects of the synthesis parameters, such as the amount of 1-MIm and the P/Al ratio, on the formation of DNL-1 nanocrystals were studied. The products were characterized using a variety of techniques. XRD, DLS, SEM and TEM results indicate that the as-synthesized DNL-1 nanocrystals have good crystallinity and narrow particle size distributions, and their average particle size was controlled in the 100-220nm range by simply adjusting the amount of 1-MIm. TG-DSC and N2 adsorption analyses reveal that the as-synthesized DNL-1 nanocrystals exhibit good thermal stability and the calcined samples possess high BET surface areas and large pore volumes. In addition, the cooperative structure-directing effects of 1-MIm and the eutectic mixture cation (DEA(+)) in the formation of DNL-1 nanocrystals were discussed.

  13. Flavonoid nanocrystals produced by ARTcrystal®-technology.

    PubMed

    Scholz, Patrik; Keck, Cornelia M

    2015-03-30

    ARTcrystal(®)-technology is a novel technique for a more efficient production of nanocrystals. It consists of a high speed stirring (HSS) step as pre-milling and subsequent high pressure homogenization (HPH) at reduced pressure and cycle numbers. In this study, three antioxidants, rutin, hesperidin and apigenin, were processed by ARTcrystal(®)-technology, the results were compared to sizes obtained for the production of nanocrystals produced by classical HPH. By using the ARTcrystal(®)-process, all three substances could be transformed into nanosuspensions with mean sizes and PdIs of 431 nm/0.27, 717 nm/0.21 and 262 nm/0.31, respectively. Depending on the properties of the raw material the ARTcrystal(®)-technology revealed similar or even better results than classical HPH. Further optimization of the setup of the HSS process might lead to an optimized process with higher efficacy than classical HPH.

  14. Strongly bound citrate stabilizes the apatite nanocrystals in bone

    SciTech Connect

    Hu, Y.-Y.; Rawal, A.; Schmidt-Rohr, K.

    2010-10-12

    Nanocrystals of apatitic calcium phosphate impart the organic-inorganic nanocomposite in bone with favorable mechanical properties. So far, the factors preventing crystal growth beyond the favorable thickness of ca. 3 nm have not been identified. Here we show that the apatite surfaces are studded with strongly bound citrate molecules, whose signals have been identified unambiguously by multinuclear magnetic resonance (NMR) analysis. NMR reveals that bound citrate accounts for 5.5 wt% of the organic matter in bone and covers apatite at a density of about 1 molecule per (2 nm){sup 2}, with its three carboxylate groups at distances of 0.3 to 0.45 nm from the apatite surface. Bound citrate is highly conserved, being found in fish, avian, and mammalian bone, which indicates its critical role in interfering with crystal thickening and stabilizing the apatite nanocrystals in bone

  15. Diamond Technology Initiative

    DTIC Science & Technology

    1994-05-01

    thermal stresses of 10 million Watts per meter, 1,000 times better than Zerodur *. This property is also important for many thermal management...products UTD has coated to date include: • Optical windows, lenses, and mirrors . Zinc sulfide infrared windows coated with a 2.5 micron-thick...implants 16, 49 microwave plasma-enhanced CVD 2 mirrors , diamond-coated 49 models of diamond growth 10, 25, 33, 34, 39 moderators 10

  16. Nanocrystals of medium soluble actives--novel concept for improved dermal delivery and production strategy.

    PubMed

    Zhai, Xuezhen; Lademann, Jürgen; Keck, Cornelia M; Müller, Rainer H

    2014-08-15

    After use in oral pharmaceutical products, nanocrystals are meanwhile applied to improve the dermal penetration of cosmetic actives (e.g. rutin, hesperidin) and of drugs. By now, nanocrystals are only dermally applied made from poorly soluble actives. The novel concept is to formulate nanocrystals also from medium soluble actives, and to apply a dermal formulation containing additionally nanocrystals. The nanocrystals should act as fast dissolving depot, increase saturation solubility and especially accumulate in the hair follicles, to further increase skin penetration. Caffeine was used as model compound with relevance to market products, and a particular process was developed for the production of caffeine nanocrystals to overcome the supersaturation related effect of crystal growth and fiber formation - typical with medium soluble compounds. It is based on low energy milling (pearl milling) in combination with low dielectric constant dispersion media (water-ethanol or ethanol-propylene glycol mixtures) and optimal stabilizers. Most successful was Carbopol(®) 981 (e.g. 20% caffeine in ethanol-propylene glycol 3:7 with 2% Carbopol, w/w). Nanocrystals with varied sizes can now be produced in a controlled process e.g. 660 nm (optimal for hair follicle accumulation) to 250 nm (optimal for fast dissolution). The short term test proved stability over 2 months of the present formulation being sufficient to perform in vivo testing of the novel concept.

  17. Ultra-small photoluminescent silicon-carbide nanocrystals by atmospheric-pressure plasmas.

    PubMed

    Askari, Sadegh; Ul Haq, Atta; Macias-Montero, Manuel; Levchenko, Igor; Yu, Fengjiao; Zhou, Wuzong; Ostrikov, Kostya Ken; Maguire, Paul; Svrcek, Vladimir; Mariotti, Davide

    2016-10-06

    Highly size-controllable synthesis of free-standing perfectly crystalline silicon carbide nanocrystals has been achieved for the first time through a plasma-based bottom-up process. This low-cost, scalable, ligand-free atmospheric pressure technique allows fabrication of ultra-small (down to 1.5 nm) nanocrystals with very low level of surface contamination, leading to fundamental insights into optical properties of the nanocrystals. This is also confirmed by their exceptional photoluminescence emission yield enhanced by more than 5 times by reducing the nanocrystals sizes in the range of 1-5 nm, which is attributed to quantum confinement in ultra-small nanocrystals. This method is potentially scalable and readily extendable to a wide range of other classes of materials. Moreover, this ligand-free process can produce colloidal nanocrystals by direct deposition into liquid, onto biological materials or onto the substrate of choice to form nanocrystal films. Our simple but efficient approach based on non-equilibrium plasma environment is a response to the need of most efficient bottom-up processes in nanosynthesis and nanotechnology.

  18. Magnetic and upconverted luminescent properties of multifunctional lanthanide doped cubic KGdF4nanocrystals

    NASA Astrophysics Data System (ADS)

    Yang, L. W.; Zhang, Y. Y.; Li, J. J.; Li, Y.; Zhong, J. X.; Chu, Paul K.

    2010-12-01

    Lanthanide (Ln3+) doped KGdF4 (Ln = Yb3+, Er3+, Ho3+, Tm3+) nanocrystals with a mean diameter of approximately 12 nm were synthesized by a hydrothermal method using oleic acid as a stabilizing agent at 180 °C. The nanocrystals crystallize in the cubic phase as α-NaGdF4. When excited by a 980 nm laser, these Ln3+ doped nanocrystals exhibit multicolor up-conversion (UC) emissions in red, yellow, blue and white. The calculated color coordinates demonstrate that white UC emission (CIE-X = 0.352, CIE-Y = 0.347) can be obtained by varying the dopant concentrations in the Yb3+/Ho3+/Tm3+ triply-doped nanocrystals to yield different RGB emission intensities. The measured field dependence of magnetization (M-H curves) of the KGdF4nanocrystals shows their paramagnetic characteristics that can be ascribed to the non-interacting localized nature of the magnetic moment of Gd3+ ions. Moreover, low temperature thermal treatment can enhance UC properties, magnetization and magnetic mass susceptibility of Ln3+ doped KGdF4nanocrystals. The multifunctional Ln3+ doped KGdF4nanocrystals have potential applications in color displays, bioseparation, and optical-magnetic dual modal nanoprobes in biomedical imaging.

  19. High-mobility diamond

    NASA Astrophysics Data System (ADS)

    Landstrass, Maurice I.

    1994-04-01

    Recent improvements in the CVD diamond deposition process have made possible the fabrication of diamond photoconductive diodes with carrier mobility and lifetime exceeding the values typical of natural gemstones. One of the more surprising recent results is that the best room-temperature carrier properties have been measured on polycrystalline diamond films. The combined electron- hole mobility, as measured by transient photoconductivity at low carrier densities, is 4000 square centimeters per volt per second at electric field of 200 volts per centimeter and is comparable to that of the best single-crystal IIa natural diamonds. Carrier lifetimes measured under the same conditions are 150 picoseconds for the CVD diamond films. The collection distance within the diamond films, at the highest applied fields, is comparable to the average film grain size, indicative of little or no carrier scattering at grain boundaries. A comparison of SIMS measurements with electrical results suggest that impurity incorporation in the near grain boundary regions are responsible for controlling the carrier mobility.

  20. Multifunctional Sn- and Fe-Codoped In2O3 Colloidal Nanocrystals: Plasmonics and Magnetism.

    PubMed

    Tandon, Bharat; Shanker, G Shiva; Nag, Angshuman

    2014-07-03

    We prepared Fe- and Sn-codoped colloidal In2O3 nanocrystals (∼6 nm). Sn doping provides free electrons in the conduction band, originating localized surface plasmon resonance (LSPR) and electrical conductivity. The LSPR band can be tuned between 2000 and >3000 nm, depending on the extent and kind of dopant ions. Fe doping, on the other hand, provides unpaired electrons, resulting in weak ferromagnetism at room temperature. Fe doping shifts the LSPR band of 10% Sn-doped In2O3 nanocrystals to a longer wavelength along with a reduction in intensity, suggesting trapping of charge carriers around the dopant centers, whereas Sn doping increases the magnetization of 10% Fe-doped In2O3 nanocrystals, probably because of the free electron mediated interactions between distant magnetic ions. The combination of plasmonics and magnetism, in addition to electronic conductivity and visible-light transparency, is a unique feature of our colloidal codoped nanocrystals.

  1. Examination of Short- and Long-Range Atomic Order Nanocrystalline SiC and Diamond by Powder Diffraction Methods

    NASA Technical Reports Server (NTRS)

    Palosz, B.; Grzanka, E.; Stelmakh, S.; Gierlotka, S.; Weber, H.-P.; Proffen, T.; Palosz, W.

    2002-01-01

    The real atomic structure of nanocrystals determines unique, key properties of the materials. Determination of the structure presents a challenge due to inherent limitations of standard powder diffraction techniques when applied to nanocrystals. Alternate methodology of the structural analysis of nanocrystals (several nanometers in size) based on Bragg-like scattering and called the "apparent lattice parameter" (alp) is proposed. Application of the alp methodology to examination of the core-shell model of nanocrystals will be presented. The results of application of the alp method to structural analysis of several nanopowders were complemented by those obtained by determination of the Atomic Pair Distribution Function, PDF. Based on synchrotron and neutron diffraction data measured in a large diffraction vector of up to Q = 25 Angstroms(exp -1), the surface stresses in nanocrystalline diamond and SiC were evaluated.

  2. Synthesis and size differentiation of Ge nanocrystals in amorphous SiO2

    NASA Astrophysics Data System (ADS)

    Ağan, S.; Çelik-Aktaş, A.; Zuo, J. M.; Dana, A.; Aydınlı, A.

    2006-04-01

    Germanosilicate layers were grown on Si substrates by plasma enhanced chemical vapor deposition (PECVD) and annealed at different temperatures ranging from 700 1010 °C for durations of 5 to 60 min. Transmission electron microscopy (TEM) was used to investigate Ge nanocrystal formation in SiO2:Ge films. High-resolution cross section TEM images, electron energy-loss spectroscopy and energy dispersive X-ray analysis (EDX) data indicate that Ge nanocrystals are present in the amorphous silicon dioxide films. These nanocrystals are formed in two spatially separated layers with average sizes of 15 and 50 nm, respectively. EDX analysis indicates that Ge also diffuses into the Si substrate.

  3. Triphasic Tooling with Small Oriented Diamond Tip for Turning and Smoothing Lightweight Mirrors

    NASA Technical Reports Server (NTRS)

    Voronov, O. A.; Tompa, G. S.; Kear, B. H.; Veress, V.

    2004-01-01

    We are developing a new method for the growth of small diamond crystals at very high temperatures and pressures directly from a carbon melt. A prototype "Supercell" has been developed for this purpose. This system is capable of high rate crystal growth in relatively large working volumes. The resulting high quality diamond crystals will be incorporated into a triphasic diamond/titanium carbide/titanium composite tool, with an oriented diamond crystal at its tip. High pressure is needed to prevent degradation of diamond at high temperature, and to ensure the formation of a crack & composite structure. After grinding and polishing, the composite material will be joined to a steel holder, thus forming a diamond-tipped tool for turning and smoothing of a mirror surface. A properly oriented single-crystal diamond cuts and smoothes much better than a conventional polycrystalline diamond crystal. This is because the hardness depends on crystallographic orientation-the difference corresponds to 60-100 GPa on the Knoop scale. Our goal is to achieve surface roughness of about 1 nm, which will be accomplished by precision cutting and smoothing. The hardness of the functionally-graded diamond/titanium carbide/titanium composite tool varies from 100 GPa at its tip to 15 GPa at its base. Previous work has shown that the mass of machined material using an oriented-diamond tool is much larger than that for a standard diamond-metal composite tool.

  4. Electronic spectra of semiconductor nanocrystals

    SciTech Connect

    Alivisatos, A.P.

    1993-12-31

    Semiconductor nanocrystals smaller than the bulk exciton show substantial quantum confinement effects. Recent experiments including Stark effect, resonance Raman, valence band photoemission, and near edge X-ray adsorption will be used to put together a picture of the nanocrystal electronic states.

  5. Nanocrystal/sol-gel nanocomposites

    DOEpatents

    Petruska, Melissa A.; Klimov, Victor L.

    2007-06-05

    The present invention is directed to solid composites including colloidal nanocrystals within a sol-gel host or matrix and to processes of forming such solid composites. The present invention is further directed to alcohol soluble colloidal nanocrystals useful in formation of sol-gel based solid composites.

  6. Photoemission studies of semiconductor nanocrystals

    SciTech Connect

    Hamad, K. S.; Roth, R.; Alivisatos, A. P.

    1997-04-01

    Semiconductor nanocrystals have been the focus of much attention in the last ten years due predominantly to their size dependent optical properties. Namely, the band gap of nanocrystals exhibits a shift to higher energy with decreasing size due to quantum confinement effects. Research in this field has employed primarily optical techniques to study nanocrystals, and in this respect this system has been investigated extensively. In addition, one is able to synthesize monodisperse, crystalline particles of CdS, CdSe, Si, InP, InAs, as well as CdS/HgS/CdS and CdSe/CdS composites. However, optical spectroscopies have proven ambiguous in determining the degree to which electronic excitations are interior or surface admixtures or giving a complete picture of the density of states. Photoemission is a useful technique for understanding the electronic structure of nanocrystals and the effects of quantum confinement, chemical environments of the nanocrystals, and surface coverages. Of particular interest to the authors is the surface composition and structure of these particles, for they have found that much of the behavior of nanocrystals is governed by their surface. Previously, the authors had performed x-ray photoelectron spectroscopy (XPS) on CdSe nanocrystals. XPS has proven to be a powerful tool in that it allows one to determine the composition of the nanocrystal surface.

  7. Method of synthesizing pyrite nanocrystals

    DOEpatents

    Wadia, Cyrus; Wu, Yue

    2013-04-23

    A method of synthesizing pyrite nanocrystals is disclosed which in one embodiment includes forming a solution of iron (III) diethyl dithiophosphate and tetra-alkyl-ammonium halide in water. The solution is heated under pressure. Pyrite nanocrystal particles are then recovered from the solution.

  8. Nanocrystal/sol-gel nanocomposites

    SciTech Connect

    Petruska, Melissa A; Klimov, Victor L

    2012-06-12

    The present invention is directed to solid composites including colloidal nanocrystals within a sol-gel host or matrix and to processes of forming such solid composites. The present invention is further directed to alcohol soluble colloidal nanocrystals useful in formation of sol-gel based solid composites

  9. White light generation using CdSe/ZnS core shell nanocrystals hybridized with InGaN/GaN light emitting diodes

    NASA Astrophysics Data System (ADS)

    Nizamoglu, S.; Ozel, T.; Sari, E.; Demir, H. V.

    2007-02-01

    We introduce white light generation using CdSe/ZnS core-shell nanocrystals of single, dual, triple and quadruple combinations hybridized with InGaN/GaN LEDs. Such hybridization of different nanocrystal combinations provides the ability to conveniently adjust white light parameters including the tristimulus coordinates (x,y), correlated colour temperature (Tc) and colour rending index (Ra). We present the design, growth, fabrication and characterization of our white hybrid nanocrystal-LEDs that incorporate combinations of (1) yellow nanocrystals (λPL = 580 nm) on a blue LED (λEL = 440 nm) with (x,y) = (0.37,0.25), Tc = 2692 K and Ra = 14.69; (2) cyan and red nanocrystals (λPL = 500 and 620 nm) on a blue LED (λEL = 440 nm) with (x,y) = (0.37,0.28), Tc = 3246 K and Ra = 19.65; (3) green, yellow and red nanocrystals (λPL = 540, 580 and 620 nm) on a blue LED (λEL = 452 nm) with (x,y) = (0.30,0.28), Tc = 7521 K and Ra = 40.95; and (4) cyan, green, yellow and red nanocrystals (λPL = 500, 540, 580 and 620 nm) on a blue LED (λEL = 452 nm) with (x,y) = (0.24,0.33), Tc = 11 171 K and Ra = 71.07. These hybrid white light sources hold promise for future lighting and display applications with their highly adjustable properties.

  10. Mechanical Properties of Nanocrystal Supercrystals

    SciTech Connect

    Tam, Enrico; Podsiadlo, Paul; Shevchenko, Elena; Ogletree, D. Frank; Delplancke-Ogletree, Marie-Paule; Ashby, Paul D.

    2009-12-30

    Colloidal nanocrystals attract significant interest due to their potential applications in electronic, magnetic, and optical devices. Nanocrystal supercrystals (NCSCs) are particularly appealing for their well ordered structure and homogeneity. The interactions between organic ligands that passivate the inorganic nanocrystal cores critically influence their self-organization into supercrystals, By investigating the mechanical properties of supercrystals, we can directly characterize the particle-particle interactions in a well-defined geometry, and gain insight into both the self-assembly process and the potential applications of nanocrystal supercrystals. Here we report nanoindentation studies of well ordered lead-sulfide (Pbs) nanocrystal supercrystals. Their modulus and hardness were found to be similar to soft polymers at 1.7 GPa and 70 MPa respectively and the fractures toughness was 39 KPa/m1/2, revealing the extremely brittle nature of these materials.

  11. Nanocrystal/sol-gel nanocomposites

    DOEpatents

    Klimov, Victor L.; Petruska, Melissa A.

    2010-05-25

    The present invention is directed to a process for preparing a solid composite having colloidal nanocrystals dispersed within a sol-gel matrix, the process including admixing colloidal nanocrystals with an amphiphilic polymer including hydrophilic groups selected from the group consisting of --COOH, --OH, --SO.sub.3H, --NH.sub.2, and --PO.sub.3H.sub.2 within a solvent to form an alcohol-soluble colloidal nanocrystal-polymer complex, admixing the alcohol-soluble colloidal nanocrystal-polymer complex and a sol-gel precursor material, and, forming the solid composite from the admixture. The present invention is also directed to the resultant solid composites and to the alcohol-soluble colloidal nanocrystal-polymer complexes.

  12. The investigation of boron-doped diamond absorbance spectrum

    NASA Astrophysics Data System (ADS)

    Aksenova, A. S.; Altuhov, A. A.; Ryabeva, E. V.; Samosadnyi, V. T.; Feshchenko, V. S.; Chernyaev, A. P.; Shepelev, V. A.

    2017-01-01

    The trend of using of radiation with shorter wave length in leading high technological processes demands the detected search of materials for the solid-state electronics equipment and optical systems of an ultra violet and vacuum ultra violet spectral range. Diamond photodetectors of ultra violet radiation have the advantage of their opponents due to their unique properties, such as high sensitivity at the range of 190–250 nm and low sensitivity to the solar irradiation. The modification of semiconductive diamond material properties by the doping to get photodetectors with the different width of photosensitivity range is of a great interest. Due to this fact the spectroscopic investigation of artificial diamonds doped with boron took place for the definition of their applicability to produce the wide-spectral photosensitive equipment. The samples of thin diamond films were cut out in a crystallography plane (001). Sample transmission spectra were measured by vacuum infrared Fourier transform spectrometer at the range of 400–7000 cm-1. As a result it was explored that diamond based detectors doped with boron could be applied for the detection of infrared irradiation at the average infrared spectral range, however it is necessary to optimize the doping level of diamond materials to reach the compromise between the sensitivity and the speed capability of produced diamond photodetectors.

  13. Polycrystalline-Diamond MEMS Biosensors Including Neural Microelectrode-Arrays.

    PubMed

    Varney, Michael W; Aslam, Dean M; Janoudi, Abed; Chan, Ho-Yin; Wang, Donna H

    2011-08-15

    Diamond is a material of interest due to its unique combination of properties, including its chemical inertness and biocompatibility. Polycrystalline diamond (poly-C) has been used in experimental biosensors that utilize electrochemical methods and antigen-antibody binding for the detection of biological molecules. Boron-doped poly-C electrodes have been found to be very advantageous for electrochemical applications due to their large potential window, low background current and noise, and low detection limits (as low as 500 fM). The biocompatibility of poly-C is found to be comparable, or superior to, other materials commonly used for implants, such as titanium and 316 stainless steel. We have developed a diamond-based, neural microelectrode-array (MEA), due to the desirability of poly-C as a biosensor. These diamond probes have been used for in vivo electrical recording and in vitro electrochemical detection. Poly-C electrodes have been used for electrical recording of neural activity. In vitro studies indicate that the diamond probe can detect norepinephrine at a 5 nM level. We propose a combination of diamond micro-machining and surface functionalization for manufacturing diamond pathogen-microsensors.

  14. Polycrystalline-Diamond MEMS Biosensors Including Neural Microelectrode-Arrays

    PubMed Central

    Varney, Michael W.; Aslam, Dean M.; Janoudi, Abed; Chan, Ho-Yin; Wang, Donna H.

    2011-01-01

    Diamond is a material of interest due to its unique combination of properties, including its chemical inertness and biocompatibility. Polycrystalline diamond (poly-C) has been used in experimental biosensors that utilize electrochemical methods and antigen-antibody binding for the detection of biological molecules. Boron-doped poly-C electrodes have been found to be very advantageous for electrochemical applications due to their large potential window, low background current and noise, and low detection limits (as low as 500 fM). The biocompatibility of poly-C is found to be comparable, or superior to, other materials commonly used for implants, such as titanium and 316 stainless steel. We have developed a diamond-based, neural microelectrode-array (MEA), due to the desirability of poly-C as a biosensor. These diamond probes have been used for in vivo electrical recording and in vitro electrochemical detection. Poly-C electrodes have been used for electrical recording of neural activity. In vitro studies indicate that the diamond probe can detect norepinephrine at a 5 nM level. We propose a combination of diamond micro-machining and surface functionalization for manufacturing diamond pathogen-microsensors. PMID:25586924

  15. Localized Synthesis of Silicon Nanocrystals in Silicon-rich SiO2 by CO2 Laser Annealing

    DTIC Science & Technology

    2007-05-01

    film rapid-thermal-annealed (RTA) by CO2 laser are primarily investigated. The micro -photoluminescence (μ-PL) and HRTEM analysis indicate that the...Si nanocrystals exhibits a largest diameter of 8 nm and a highest density of 4.5×1016 cm-3, which emits strong PL at 790-825 nm. The micro ...SiOx film. Index Terms— CO2 Laser annealing, Si nanocrystal, SiOx, Nanotechnology, micro -photoluminescence. I. Introduction CO2 laser based zone

  16. How Plasmonic excitation influences the LIPSS formation on diamond during multipulse femtosecond laser irradiation ?

    NASA Astrophysics Data System (ADS)

    Abdelmalek, Ahmed; Bedrane, Zeyneb; Amara, El-Hachemi; Eaton, Shane M.; Ramponi, Roberta

    2017-03-01

    A generalized plasmonic model is proposed to calculate the nanostructure period induced by multipulse laser femtosecond on diamond at 800 nm wavelengths. We follow the evolution of LIPSS formation by changing diamond optical parameters in function of electron plasma excitation during laser irradiation. Our calculations shows that the ordered nanostructures can be observed only in the range of surface plasmon polariton excitation.

  17. Ultrasound effects on the tribological properties of synthesized diamond films

    SciTech Connect

    Snikta, V.; Trava-Airoldi, V.J.; Baranauskas, V.

    1995-09-01

    The friction and wear behavior of chemical vapor deposition grown diamond films has been investigated under strong ultrasound conditions at the friction interface. Experiments were performed on an alternating {open_quotes}pin-on-plate{close_quotes} tribometer constructed as an ultrasonic motor with excited bimodal mechanical vibrations at the frequency of 20 kHz. Ultrasound sliding of the films was done against alumina ceramics and with the diamond film itself. We have shown that chemical vapor deposition diamond films can be fast polished mechanically without significant graphitization by ultrasonic treatment. The initial film roughness was reduced from an average R{sub a} {approximately}3000 nm to R{sub a} {approximately}10 nm. The polishing decreased the static coefficient of friction of the diamond film from about 0.53 to about 0.12. The operative mechanism for the polishing in the case of initially rough diamond samples appears to be asperity fracture. For smooth diamond samples it is suggested that tribochemical oxidation is also a polishing mechanism. 17 refs., 8 figs.

  18. Development of cationic nanocrystals for ocular delivery.

    PubMed

    Romero, Gregori B; Keck, Cornelia M; Müller, Rainer H; Bou-Chacra, Nadia A

    2016-10-01

    A cationic nanocrystal formulation containing dexamethasone acetate nanocrystals (0.05%) and polymyxin B (0.10%) for ophthalmic application was produced using a self-developed small scale method for wet bead milling. The formulation developed offers the advantage of increased saturation solubility of the drug (due to the nano-size of the crystals) and increased residence time in the eye (due to small size and increased mucoadhesion by the cationic charge) resulting ultimately in potential increased bioavailability. Characterization of the nanosuspensions by photon correlation spectroscopy (PCS) and transmission electron microscopy showed that the production method was successful in achieving dexamethasone crystals in the range of about 200-250nm. The physical stabilization of the nanocrystals and generation of the positive charge were realized by using cetylpyridinium chloride (CPC) and benzalkonium chloride (BAC) at the concentration of 0.01%. In contrast to other cationic excipients, they are regulatorily accepted due to their use as preservatives. The drug polymyxin B also contributed to the positive charge. Positive zeta potentials in the range +20 to +30mV were achieved. Isotonicity was adjusted using NaCl and non-ionic excipients (glycerol, sorbitol, dextrose). Physical and chemical stabilities were monitored for a period of 6months at room temperature, 5°C and 40°C. Particle size of the bulk population assessed by PCS remained practically unchanged over 6months of storage for the various formulations without isotonicity agents, and for the CPC-containing formulations with non-ionic isotonicity excipients. The chemical content also proved stable after 6months for all 3 temperatures evaluated. In vitro investigation of mucoadhesion was tested using mucin solutions at different concentrations, and the generated negative zeta potential was used as a measure of the interaction. The zeta potential reversed to about -15mV, indicating distinct interaction. The

  19. Silica based polishing of {100} and {111} single crystal diamond

    PubMed Central

    Thomas, Evan L H; Mandal, Soumen; Brousseau, Emmanuel B; Williams, Oliver A

    2014-01-01

    Diamond is one of the hardest and most difficult to polish materials. In this paper, the polishing of {111} and {100} single crystal diamond surfaces by standard chemical mechanical polishing, as used in the silicon industry, is demonstrated. A Logitech Tribo Chemical Mechanical Polishing system with Logitech SF1 Syton and a polyurethane/polyester polishing pad was used. A reduction in roughness from 0.92 to 0.23 nm root mean square and 0.31 to 0.09 nm rms for {100} and {111} samples respectively was observed. PMID:27877689

  20. Cryotribology of diamond and graphite

    SciTech Connect

    Iwasa, Yukikazu; Ashaboglu, A.F.; Rabinowicz, E.R.

    1996-12-31

    An experimental study was carried out on the tribological behavior of materials of interest in cryogenic applications, focusing on diamond and graphite. Both natural diamond (referred in the text as diamond) and chemical-vapor-deposition (CVD) diamond (CVD-diamond) were used. The experiment was carried out using a pin-on-disk tribometer capable of operating at cryogenic temperatures, from 4.2 to 293 K. Two basic scenarios of testing were used: (1) frictional coefficient ({mu}) vs velocity (v) characteristics at constant temperatures; (2) {mu} vs temperature (T) behavior at fixed sliding speeds. For diamond/CVD-diamond, graphite/CVD-diamond, stainless steel/CVD-diamond pairs, {mu}`s are virtually velocity independent. For each of diamond/graphite, alumina/graphite, and graphite/graphite pairs, the {partial_derivative}{mu}/{partial_derivative}v characteristic is favorable, i.e., positive. For diamond/CVD-diamond and graphite/CVD-diamond pairs, {mu}`s are nearly temperature independent between in the range 77 - 293 K. Each {mu} vs T plot for pin materials sliding on graphite disks has a peak at a temperature in the range 100 - 200 K.

  1. Size- and shape-dependent growth of fluorescent ZnS nanorods and nanowires using Ag nanocrystals as seeds

    NASA Astrophysics Data System (ADS)

    Shen, Huaibin; Shang, Hangying; Niu, Jinzhong; Xu, Weiwei; Wang, Hongzhe; Li, Lin Song

    2012-09-01

    High-quality, monodisperse, and size-controlled Ag-ZnS nanorods or nanowires have been synthesized successfully using Ag nanocrystals as seeds. Such one-dimensional colloidal Ag-ZnS nanorods or nanowires having a purposefully controlled diameter in the range of 5-9 nm and a length of 18-600 nm were obtained by altering the reaction conditions, such as concentration, reaction time, reaction temperature, and diameter of Ag nanocrystals. The conjunction interface of Ag-ZnS nanorods or nanowires consists of the (200) plane of Ag nanocrystal and (101) plane of ZnS rod or wire, the <101> directions of ZnS nanorods grow preferentially. Based on the photoluminescence and lifetime of Ag-ZnS nanorods, it was found that Ag nanocrystals enhanced the radiative rate eventually, the fluorescence intensity of Ag-ZnS nanorods can be tuned by changing the size of the Ag seeds. The Ag-ZnS nanorods or nanowires showed greatly improved optical properties as compared to ZnS nanocrystals, the maximum emission was around 402 nm and the photoluminescence quantum yield was up to 30% when 5 nm Ag nanocrystals were used as seeds.High-quality, monodisperse, and size-controlled Ag-ZnS nanorods or nanowires have been synthesized successfully using Ag nanocrystals as seeds. Such one-dimensional colloidal Ag-ZnS nanorods or nanowires having a purposefully controlled diameter in the range of 5-9 nm and a length of 18-600 nm were obtained by altering the reaction conditions, such as concentration, reaction time, reaction temperature, and diameter of Ag nanocrystals. The conjunction interface of Ag-ZnS nanorods or nanowires consists of the (200) plane of Ag nanocrystal and (101) plane of ZnS rod or wire, the <101> directions of ZnS nanorods grow preferentially. Based on the photoluminescence and lifetime of Ag-ZnS nanorods, it was found that Ag nanocrystals enhanced the radiative rate eventually, the fluorescence intensity of Ag-ZnS nanorods can be tuned by changing the size of the Ag seeds. The Ag

  2. Loosening quantum confinement: observation of real conductivity caused by hole polarons in semiconductor nanocrystals smaller than the Bohr radius.

    PubMed

    Ulbricht, Ronald; Pijpers, Joep J H; Groeneveld, Esther; Koole, Rolf; Donega, Celso de Mello; Vanmaekelbergh, Daniel; Delerue, Christophe; Allan, Guy; Bonn, Mischa

    2012-09-12

    We report on the gradual evolution of the conductivity of spherical CdTe nanocrystals of increasing size from the regime of strong quantum confinement with truly discrete energy levels to the regime of weak confinement with closely spaced hole states. We use the high-frequency (terahertz) real and imaginary conductivities of optically injected carriers in the nanocrystals to report on the degree of quantum confinement. For the smaller CdTe nanocrystals (3 nm < radius < 5 nm), the complex terahertz conductivity is purely imaginary. For nanocrystals with radii exceeding 5 nm, we observe the onset of real conductivity, which is attributed to the increasingly smaller separation between the hole states. Remarkably, this onset occurs for a nanocrystal radius significantly smaller than the bulk exciton Bohr radius a(B) ∼ 7 nm and cannot be explained by purely electronic transitions between hole states, as evidenced by tight-binding calculations. The real-valued conductivity observed in the larger nanocrystals can be explained by the emergence of mixed carrier-phonon, that is, polaron, states due to hole transitions that become resonant with, and couple strongly to, optical phonon modes for larger QDs. These polaron states possess larger oscillator strengths and broader absorption, and thereby give rise to enhanced real conductivity within the nanocrystals despite the confinement.

  3. Atomic-scale modeling of cellulose nanocrystals

    NASA Astrophysics Data System (ADS)

    Wu, Xiawa

    Cellulose nanocrystals (CNCs), the most abundant nanomaterials in nature, are recognized as one of the most promising candidates to meet the growing demand of green, bio-degradable and sustainable nanomaterials for future applications. CNCs draw significant interest due to their high axial elasticity and low density-elasticity ratio, both of which are extensively researched over the years. In spite of the great potential of CNCs as functional nanoparticles for nanocomposite materials, a fundamental understanding of CNC properties and their role in composite property enhancement is not available. In this work, CNCs are studied using molecular dynamics simulation method to predict their material' behaviors in the nanoscale. (a) Mechanical properties include tensile deformation in the elastic and plastic regions using molecular mechanics, molecular dynamics and nanoindentation methods. This allows comparisons between the methods and closer connectivity to experimental measurement techniques. The elastic moduli in the axial and transverse directions are obtained and the results are found to be in good agreement with previous research. The ultimate properties in plastic deformation are reported for the first time and failure mechanism are analyzed in details. (b) The thermal expansion of CNC crystals and films are studied. It is proposed that CNC film thermal expansion is due primarily to single crystal expansion and CNC-CNC interfacial motion. The relative contributions of inter- and intra-crystal responses to heating are explored. (c) Friction at cellulose-CNCs and diamond-CNCs interfaces is studied. The effects of sliding velocity, normal load, and relative angle between sliding surfaces are predicted. The Cellulose-CNC model is analyzed in terms of hydrogen bonding effect, and the diamond-CNC model compliments some of the discussion of the previous model. In summary, CNC's material properties and molecular models are both studied in this research, contributing to

  4. Fabrication of planarised conductively patterned diamond for bio-applications.

    PubMed

    Tong, Wei; Fox, Kate; Ganesan, Kumaravelu; Turnley, Ann M; Shimoni, Olga; Tran, Phong A; Lohrmann, Alexander; McFarlane, Thomas; Ahnood, Arman; Garrett, David J; Meffin, Hamish; O'Brien-Simpson, Neil M; Reynolds, Eric C; Prawer, Steven

    2014-10-01

    The development of smooth, featureless surfaces for biomedical microelectronics is a challenging feat. Other than the traditional electronic materials like silicon, few microelectronic circuits can be produced with conductive features without compromising the surface topography and/or biocompatibility. Diamond is fast becoming a highly sought after biomaterial for electrical stimulation, however, its inherent surface roughness introduced by the growth process limits its applications in electronic circuitry. In this study, we introduce a fabrication method for developing conductive features in an insulating diamond substrate whilst maintaining a planar topography. Using a combination of microwave plasma enhanced chemical vapour deposition, inductively coupled plasma reactive ion etching, secondary diamond growth and silicon wet-etching, we have produced a patterned substrate in which the surface roughness at the interface between the conducting and insulating diamond is approximately 3 nm. We also show that the patterned smooth topography is capable of neuronal cell adhesion and growth whilst restricting bacterial adhesion.

  5. Temperature enhancement of secondary electron emission from hydrogenated diamond films

    SciTech Connect

    Stacey, A.; Prawer, S.; Rubanov, S.; Akhvlediani, R.; Michaelson, Sh.; Hoffman, A.

    2009-09-15

    The effect of temperature on the stability of the secondary electron emission (SEE) yield from approx100-nm-thick continuous diamond films is reported. At room temperature, the SEE yield was found to decay as a function of electron irradiation dose. The SEE yield is observed to increase significantly upon heating of the diamond surface. Furthermore, by employing moderate temperatures, the decay of the SEE yield observed at room temperature is inhibited, showing a nearly constant yield with electron dose at 200 deg. C. The results are explained in terms of the temperature dependence of the electron beam-induced hydrogen desorption from the diamond surface and surface band bending. These findings demonstrate that the longevity of diamond films in practical applications of SEE can be increased by moderate heating.

  6. Silicon nanocrystal inks, films, and methods

    DOEpatents

    Wheeler, Lance Michael; Kortshagen, Uwe Richard

    2015-09-01

    Silicon nanocrystal inks and films, and methods of making and using silicon nanocrystal inks and films, are disclosed herein. In certain embodiments the nanocrystal inks and films include halide-terminated (e.g., chloride-terminated) and/or halide and hydrogen-terminated nanocrystals of silicon or alloys thereof. Silicon nanocrystal inks and films can be used, for example, to prepare semiconductor devices.

  7. In situ capping for size control of monochalcogenides (ZnS, CdS, and SnS) nanocrystals produced by anaerobic metal-reducing bacteria

    SciTech Connect

    Jang, Gyoung Gug; Jacobs, Christopher B.; Ivanov, Ilia N.; Joshi, Pooran C.; Meyer, III, Harry M.; Kidder, Michelle; Armstrong, Beth L.; Datskos, Panos G.; Graham, David E.; Moon, Ji -Won

    2015-07-24

    Metal monochalcogenide quantum dot nanocrystals of ZnS, CdS and SnS were prepared by anaerobic, metal-reducing bacteria using in situ capping by oleic acid or oleylamine. Furthermore, the capping agent preferentially adsorbs on the surface of the nanocrystal, suppressing the growth process in the early stages, thus leading to production of nanocrystals with a diameter of less than 5 nm.

  8. Magnetization reversal in europium sulfide nanocrystals

    NASA Astrophysics Data System (ADS)

    Redígolo, Marcela L.; Koktysh, Dmitry S.; Rosenthal, Sandra J.; Dickerson, James H.; Gai, Zheng; Gao, Lan; Shen, Jian

    2006-11-01

    The authors report the observation of the reversal in the magnetization hysteresis curve of europium sulfide nanocrystals. This phenomenon was investigated through the temperature-dependent magnetization of two classes of nanomaterials, nanocrystalline (2.0nm⩽dNCs⩽100nm) and quantum confined (dNCs⩽2.0nm), where dNCs is the diameter of the nanomaterial. The effect of the size of the nanomaterial on the magnetization is attributed to the competition between the magnetic properties of strained surface atoms and unstrained core atoms. Superconducting quantum interference device probed the magnetic response. Electron microscopy and X-ray diffraction spectroscopy revealed the crystallinity and monodispersivity of the nanomaterials.

  9. Growth of Au nanocrystals on CdS nanorods

    NASA Astrophysics Data System (ADS)

    Yang, Heesun

    2006-08-01

    Nanorods of S2- rich CdS were synthesized by a reaction of excess S versus Cd precursors in the presence of ethylene diamine. The photoluminescence (PL) emission from the S2- rich CdS nanorods was broad with a peak at ˜710 nm, which was 40 nm longer in wavelength than the PL peak from Cd2+ rich CdS (˜670 nm) nanorods. The influence of surface electron or hole trap states on the luminescent pathway of CdS nanorods will be discussed to explain these shifts in wavelength. Nanocrystals of Au ˜2 nm in size were grown on S2- rich surfaces of CdS nanorods. Significant luminescence quenching was observed from the Au nanocrystals on the CdS nanorods due to interfacial charge separation. Change separation by the Au nanocrystals on the CdS resulted in enhanced photocatalytic degradation of Procion red mix-5B (PRB) dye in an aqueous solution under UV light irradiation.

  10. Evaluation of genipin-crosslinked chitosan hydrogels as a potential carrier for silver sulfadiazine nanocrystals.

    PubMed

    Gao, Lei; Gan, Hui; Meng, Zhiyun; Gu, Ruolan; Wu, Zhuona; Zhu, Xiaoxia; Sun, Wenzhong; Li, Jian; Zheng, Ying; Sun, Tao; Dou, Guifang

    2016-12-01

    In the present study genipin crosslinked chitosan (CHI) hydrogels, which had been constructed and reported in our previous studies (Gao et al., 2014 [22]), were further evaluated for their advantage as a carrier for silver sulfadiazine (AgSD) nanocrystal systems. Firstly, AgSD nanocrystals with a mean particle size of 289nm were prepared by wet milling method and encapsulated into genipin crosslinked CHI hydrogels. AgSD nanocrystals displayed a uniform distribution and very good physical stability in the hydrogel network. Swelling-dependent release pattern was found for AgSD nanocrystals from hydrogels and the release profile could be well fitted with Peppas equation. When AgSD nanocrystals were encapsulated in hydrogels their fibroblast cytotoxicity decreased markedly, and their antibacterial effects against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were still comparable to unencapsulated AgSD nanocrystals. In vivo evaluation in excision and burn cutaneous wound models in mice showed that AgSD nanocrystal hydrogels markedly decreased the expression of inflammatory cytokine IL-6, but increased the levels of growth factors VEGF-A and TGF-β1. Histopathologically, the wounds treated by hydrogels containing AgSD nanocrystals showed the best healing state compared with commercial AgSD cream, hydrogels containing AgSD bulk powders and blank hydrogels. The wounds treated by AgSD nanocrystal hydrogels were dominated by marked fibroblast proliferation, new blood vessels and thick regenerated epithelial layer. Sirius Red staining assay indicated that AgSD nanocrystal hydrogels resulted in more collagen deposition characterized by a large proportion of type I fibers. Our study suggested that genipin-crosslinked CHI hydrogel was a potential carrier for local antibacterial nanomedicines.

  11. The Diamond Makers

    NASA Astrophysics Data System (ADS)

    Hazen, Robert M.

    1999-08-01

    Since time immemorial, we have treasured diamonds for their exquisite beauty and unrivaled hardness. Yet, most of the earth's diamonds lie deep underground and totally unaccessible to us--if only we knew how to fabricate them! In The Diamond Makers Robert Hazen vividly recounts the very human desire to exceed nature and create a synthetic diamond. Spanning centuries of ground-breaking science, instances of bitter rivalry, cases of outright fraud and self-delusion, Hazen blends drama and science to reveal the extraordinary technological advances and devastating failures of the diamond industry. Along the way, readers will be introduced to the brilliant, often eccentric and controversial, pioneers of high-pressure research who have harnessed crushing pressures and scorching temperatures to transform almost any carbon-rich material, from road tar to peanut butter, into the most prized of all gems. Robert M. Hazen is the author of fifteen books, including the bestseller, Science Matters: Achieving Scientific Literacy, which he wrote with James Trefil. Dr. Hazen has won numerous awards for his research and scientific writing.

  12. Heteroepitaxial diamond growth

    NASA Astrophysics Data System (ADS)

    Markunas, R. J.; Rudder, R. A.; Posthill, J. B.; Thomas, R. E.; Hudson, G.

    1994-02-01

    Technical highlights from 1993 include the following: Growth Chemistries: A clear correlation was observed between ionization potential of feedstock gasses and critical power necessary for inductive coupling of the plasma and consequent diamond growth. Substrate preparation and epitaxial film quality: Ion-implantation of C and O has been coupled with either electrochemical etching or acid cleaning for surface preparation prior to homoepitaxial growth. Reactor modifications: Key improvements were made to the RF reactor to allow for long growths to consolidate substrates. Liquid mass flow controllers were added to precisely meter both the water and selected alcohol. Ion-implantation and lift off: Lift off of diamond platelets has been achieved with two processes. Ion-implantation of either C or O followed by annealing and implantation of either C or O followed by water based electrolysis. Diamond characterization: Development of novel detect characterization techniques: (1) Etch delineation of defects by exposure to propane torch flame. (2) Hydrogen plasma exposure to enhance secondary electron emission and provide non-topographical defect contrast. Acetylene will react at room temperature with sites created by partial desorption of oxygen from the (100) diamond surface. Thermal desorption measurements give an apparent activation energy for CO desorption from diamond (100) of 45 kcal/mol. Quantum chemical calculations indicate an activation energy of 38 kcal/mol for CO desorption. Ab initio calculations on (100) surfaces indicates that oxygen adsorbed at one dimer site has an effect on the dimerization of an adjacent site.

  13. [Studies on nano-diamond prepared by explosive detonation by Raman and infrared spectroscopy].

    PubMed

    Wen, Chao; Jin, Zhi-Hao; Liu, Xiao-Xin; Li, Xun; Guan, Jin-Qing; Sun, De-Yu; Lin, Ying-Rui; Tang, Shi-Ying; Zhou, Gang; Lin, Jun-De

    2005-05-01

    Nano-diamond was synthesized by TNT/RDX explosives detonation in a steel chamber and characterized by X-ray diffraction (XRD), laser Raman spectroscopy, and infrared spectroscopy. XRD results indicate that nano-diamond has cubic diamond structure. The parameter of unit cell of nano-diamond is 0.359 23 nm and is 0.72% larger than that of the bulk diamond. The high-density defects and other impurity atoms in the nano-diamond structure may lead to the large lattice constant. The examination results of Raman spectra show that the Raman band is broader and shifts to l ow frequency by 3 cm(-1), because the size of nano-diamond reaches nanometer order. There is little graphite in the nano-diamond. There are two peaks in FTIR of the nano-diamond, which are characteristic peaks of diamond at 1 262 and 1 134 cm(-1). Besides these two peaks, there are six peaks at 3 422, 1 643, 2 971, 2 930, 2 857 and 1 788 cm(-1) respectively. The FTIR bands at 2 930 and 2 857 cm(-1) are the antisymmetrical and symmetrical stretch vibration absorption spectra of CH2 respectively. The 3 422 cm(-1) is the stretch vibration absorption peak of O-H. The 1 634 cm(-1) confirms that there are H2O in the nano-diamond. The 2 971 cm(-1) is the antisymmetrical stretch vibration absorption peak of CH3. The 1 788 cm(-1) is the stretch vibration absorption peak of C=O. These indicate that there are H and O elements in the nano-diamond. From the mechanism of the nano-diamond, the authors discuss the reason for the vibration absorption peaks of O-H, CH2, CH3, and C=O, existing in the FTIR of the nano-diamond.

  14. Diamond Nanowire for UV Detection

    DTIC Science & Technology

    2010-02-28

    addition to the stated goal of solar - blind , radiation-hard diamond nanowire UV detectors [3]. The use of diamond nanowires in field-effect transistors could...the next phase. As a result, a working diamond nanowire UV detector can be expected within the coming few months. And, a completely new diamond...attractive candidate for use in ultraviolet ( UV ) light detectors and emitters[2]. Of all known materials, it is the hardest, and has the highest

  15. Preparation of zwitterionically charged nanocrystals by surface TEMPO-mediated oxidation and partial deacetylation of α-chitin.

    PubMed

    Ifuku, Shinsuke; Hori, Taishi; Izawa, Hironori; Morimoto, Minoru; Saimoto, Hiroyuki

    2015-05-20

    Zwitterionic nanocrystals were prepared by TEMPO-mediated oxidation, partial deacetylation, and subsequent mechanical disintegration of α-chitin. The pH dependence of the morphology, transparency, and viscosity of the nanocrystals were evaluated. After those reactions, the carboxylate and amino group contents of the chitin derivative were 0.45 and 1.26 mmol/g, respectively. After mechanical treatment, the water dispersion consisted of nanocrystals approximately 250 nm long and 10nm thick. Under acidic and basic conditions, the water dispersions were highly transparent. On the other hand, under neutral conditions, the dispersion was turbid due to the ionic interaction between the cationic and anionic groups on the nanocrystal surface. Although the surface zwitterionic nanocrystals collected from acidic and basic dispersion were randomly oriented due to electrostatic repulsions, nanocrystals formed aggregates in neutral water due to the cationic and anionic interaction between them. Nanocrystals in neutral water had higher viscosity than those in acidic and basic water, since ionic interaction caused nanocrystal networks to form in water.

  16. Diamond collecting in northern Colorado.

    USGS Publications Warehouse

    Collins, D.S.

    1982-01-01

    The discovery of numerous diamond-bearing kimberlite diatremes in the N Front Range of Colorado and Wyoming is of both scientific and economic interest. Species recovered from heavy-mineral concentrates include Cr-diopside, spinel, Mg-ilmenite, pyrope and diamond. A nodule tentatively identified as a graphite-diamond eclogite was also found. -G.W.R.

  17. Making Diamond in the Laboratory

    ERIC Educational Resources Information Center

    Strong, Herbert

    1975-01-01

    Discusses the graphite to diamond transformation and a phase diagram for carbon. Describes high temperature-higher pressure experimental apparatus and growth of diamonds from seed crystals. Reviews properties of the diamond which suggest uses for the synthetic product. Illustrations with text. (GH)

  18. Biomolecular Assembly of Gold Nanocrystals

    SciTech Connect

    Micheel, Christine Marya

    2005-05-20

    Over the past ten years, methods have been developed to construct discrete nanostructures using nanocrystals and biomolecules. While these frequently consist of gold nanocrystals and DNA, semiconductor nanocrystals as well as antibodies and enzymes have also been used. One example of discrete nanostructures is dimers of gold nanocrystals linked together with complementary DNA. This type of nanostructure is also known as a nanocrystal molecule. Discrete nanostructures of this kind have a number of potential applications, from highly parallel self-assembly of electronics components and rapid read-out of DNA computations to biological imaging and a variety of bioassays. My research focused in three main areas. The first area, the refinement of electrophoresis as a purification and characterization method, included application of agarose gel electrophoresis to the purification of discrete gold nanocrystal/DNA conjugates and nanocrystal molecules, as well as development of a more detailed understanding of the hydrodynamic behavior of these materials in gels. The second area, the development of methods for quantitative analysis of transmission electron microscope data, used computer programs written to find pair correlations as well as higher order correlations. With these programs, it is possible to reliably locate and measure nanocrystal molecules in TEM images. The final area of research explored the use of DNA ligase in the formation of nanocrystal molecules. Synthesis of dimers of gold particles linked with a single strand of DNA possible through the use of DNA ligase opens the possibility for amplification of nanostructures in a manner similar to polymerase chain reaction. These three areas are discussed in the context of the work in the Alivisatos group, as well as the field as a whole.

  19. Spindly cobalt ferrite nanocrystals: preparation, characterization and magnetic properties.

    PubMed

    Cao, Xuebo; Gu, Li

    2005-02-01

    In this paper we describe the preparation of homogeneously needle-shaped cobalt ferrite (CoFe(2)O(4)) nanocrystals on a large scale through the smooth decomposition of urea and the resulting co-precipitation of Co(2+) and Fe(3+) in oleic acid micelles. Furthermore, we found that other ferrite nanocrystals with a needle-like shape, such as zinc ferrite (ZnFe(2)O(4)) and nickel ferrite (NiFe(2)O(4)), can be prepared by the same process. Needle-shaped CoFe(2)O(4) nanocrystals dispersed in an aqueous solution containing oleic acid exhibit excellent stability and the formed colloid does not produce any precipitations after two months, which is of prime importance if these materials are applied in magnetic fluids. X-ray diffraction (XRD) measurements were used to characterize the phase and component of the co-precipitation products, and demonstrate that they are spinel ferrite with a cubic symmetry. Transmission electron microscopy (TEM) observation showed that all the nanocrystals present a needle-like shape with a 22 nm short axis and an aspect ratio of around 6. Varying the concentration of oleic acid did not bring about any obvious influence on the size distribution and shapes of CoFe(2)O(4). The magnetic properties of the needle-shaped CoFe(2)O(4) nanocrystals were evaluated by using a vibrating sample magnetometer (VSM), electron paramagnetic resonance (EPR), and a Mössbauer spectrometer, and the results all demonstrated that CoFe(2)O(4) nanocrystals were superparamagnetic at room temperature.

  20. Nanofabrication of sharp diamond tips by e-beam lithography and inductively coupled plasma reactive ion etching.

    SciTech Connect

    Moldovan, N.; Divan, R.; Zeng, H.; Carlisle, J. A.; Advanced Diamond Tech.

    2009-12-07

    Ultrasharp diamond tips make excellent atomic force microscopy probes, field emitters, and abrasive articles due to diamond's outstanding physical properties, i.e., hardness, low friction coefficient, low work function, and toughness. Sharp diamond tips are currently fabricated as individual tips or arrays by three principal methods: (1) focused ion beam milling and gluing onto a cantilever of individual diamond tips, (2) coating silicon tips with diamond films, or (3) molding diamond into grooves etched in a sacrificial substrate, bonding the sacrificial substrate to another substrate or electrodepositing of a handling chip, followed by dissolution of the sacrificial substrate. The first method is tedious and serial in nature but does produce very sharp tips, the second method results in tips whose radius is limited by the thickness of the diamond coating, while the third method involves a costly bonding and release process and difficulties in thoroughly filling the high aspect ratio apex of molding grooves with diamond at the nanoscale. To overcome the difficulties with these existing methods, this article reports on the feasibility of the fabrication of sharp diamond tips by direct etching of ultrananocrystalline diamond (UNCD{reg_sign}) as a starting and structural material. The UNCD is reactive ion etched using a cap-precursor-mask scheme. An optimized etching recipe demonstrates the formation of ultrasharp diamond tips ({approx} 10 nm tip radius) with etch rates of 650 nm/min.

  1. Unusual Cathodoluminescence in Diamonds: Evidence for Metamorphism or a Source Characteristic

    NASA Astrophysics Data System (ADS)

    Bruce, L. F.; Longo, M.; Kopylova, M.; Ryder, J.

    2009-05-01

    Cathodoluminescence (CL) is a useful means of diamond "fingerprinting". CL-active cratonic macrodiamonds usually cathodoluminesce blue or yellow, and always exhibit prominent wide CL emittance peaks at 430-450 nm and 480-490 nm. Exceptions to this norm are diamond suites recently discovered in the Archean rocks metamorphosed in the greenschist facies. These macrodiamonds cathodoluminesce red, orange and yellow, and invariably exhibit the most prominent CL peak at 520 nm. The diamond suites with the unusual CL are derived from two different locations within the Michipicoten Greenstone Belt (Southern Superior craton), near the town of Wawa (Ontario). One suite is extracted from the 2.68-2.74 Ga polymict volcanic breccias and lamprophyres and the other suite - from the 2.68 Ga sedimentary conglomerates grading into overlying sandstones of the Dore assemblage. The diamondiferous conglomerates are found in an area 8 km south of the breccias and 12 km northeast of Wawa. CL emittance of macrodiamonds (> 0.5 mm) extracted from the breccias consists of a broad band at 520 nm, a sharp peak at 575.5 nm, and several lines at 550-670 nm. The conglomerate macrodiamonds mostly show a dominant peak at 520 nm, whereas corresponding microdiamonds exhibit two peaks at about 576 and 600 nm. None of the diamonds show a maximum peak at 420 nm. Polycrystalline stones from conglomerates show distinct CL spectra and colours for all intergrown crystals in the same diamond. The relative abundances of the CL colors of the conglomerate diamonds are orange-red (46%), yellow (28%), orange-green (10%), green (6%), and non-uniform colors (10%). These colours are more diverse than mostly orange CL colours in the breccia diamonds; this results from a larger variety of positions and intensity of CL peaks in the conglomerate diamonds. We propose two models for explaining the presence of the 520 nm CL peak in the breccia and conglomerate diamonds in Wawa. The first model suggests metamorphism as the

  2. Effect of argon implantation on solid-state dewetting: control of size and surface density of silicon nanocrystals

    NASA Astrophysics Data System (ADS)

    Almadori, Y.; Borowik, Ł.; Chevalier, N.; Barbé, J.-C.

    2017-01-01

    Thermally induced solid-state dewetting of ultra-thin films on insulators is a process of prime interest, since it is capable of easily forming nanocrystals. If no particular treatment is performed to the film prior to the solid-state dewetting, it is already known that the size, the shape and the density of nanocrystals is governed by the initial film thickness. In this paper, we report a novel approach to control the size and the surface density of silicon nanocrystals based on an argon-implantation preliminary surface treatment. Using 7.5 nm thin layers of silicon, we show that increasing the implantation dose tends to form smaller silicon nanocrystals with diameter and height lower than 50 nm and 30 nm, respectively. Concomitantly, the surface density is increased by a factor greater than 20, going from 5 μm-2 to values over 100 μm-2.

  3. Heteroepitaxial Diamond Growth

    DTIC Science & Technology

    1993-01-12

    of CH3 and C6 H6 adsorbed on nickel. Calculated chemisorption energies of pyramidal CH3 on Ni(l 11) are 38 for the clean surface and 50 , 47, and 17... results from early experiments on the diamond (100) surface . In Figure 3.1 we can easily distinguish features associated with the conversion of the...those 5 reports were for fairly thin (< 2 gm) epitaxial layers. The results reported there for homoepitaxy on the diamond (100) surface were quite

  4. Chemical Vapor Deposited Diamond

    DTIC Science & Technology

    1991-09-27

    surface roughness. 0.9 0.8 p0.7 0.6 0.5 C0.4 0.3 0.2- 0.1- 0-. 0 50 100 150 200 250 300 350 frequency (cm-1) Figure 10. Transmission spectrum of CVD...significantly less than one micrometer. The resultant films show root-mean- squared surface roughnesses -0.02 pm as long as the film thickness is not much... Derjaguin , B.V., Vapor Growth of Diamond on Diamond and Other Surfaces , J. Cryst. Growth 52:219-226 (1981); Spitsyn, B.V., The State of the Art in

  5. Carbon onions as nanoscopic pressure cells for diamond formation

    NASA Astrophysics Data System (ADS)

    Banhart, F.; Ajayan, P. M.

    1996-08-01

    SPHERICAL particles of carbon consisting of concentric graphite-like shells ('carbon onions') can be formed by electron irradiation of graphitic carbon materials1,2. Here we report that, when such particles are heated to ~700 °C and irradiated with electrons, their cores can be transformed to diamond. Under these conditions the spacing between layers in the carbon onions decreases from 0.31 in the outer shells (slightly less than the 0.34-nm layer spacing of graphite) to about 0.22 nm in the core, indicating considerable compression towards the particle centres. We find that this compression allows diamond to nucleate-in effect the carbon onions act as nanoscopic pressure cells for diamond formation.

  6. Nonlinear Absorption and Low-Threshold Multiphoton Pumped Stimulated Emission from All-Inorganic Perovskite Nanocrystals.

    PubMed

    Wang, Yue; Li, Xiaoming; Zhao, Xin; Xiao, Lian; Zeng, Haibo; Sun, Handong

    2016-01-13

    Halide perovskite materials have attracted intense research interest due to the striking performance in photoharvesting photovoltaics as well as photoemitting applications. Very recently, the emerging CsPbX3 (X = Cl, Br, I) perovskite nanocrystals have been demonstrated to be efficient emitters with photoluminescence quantum yield as high as ∼90%, room temperature single photon sources, and favorable lasing materials. Herein, the nonlinear optical properties, in particular, the multiphoton absorption and resultant photoluminescence of the CsPbBr3 nanocrystals, were investigated. Notably, a large two-photon absorption cross-section of up to ∼1.2 × 10(5) GM is determined for 9 nm sized CsPbBr3 nanocrystals. Moreover, low-threshold frequency-upconverted stimulated emission by two-photon absorption was observed from the thin film of close-packed CsPbBr3 nanocrystals. The stimulated emission is found to be photostable and wavelength-tunable. We further realize the three-photon pumped stimulated emission in green spectra range from colloidal nanocrystals for the first time. Our results reveal the strong nonlinear absorption in the emerging CsPbX3 perovskite nanocrystals and suggest these nanocrystals as attractive multiphoton pumped optical gain media, which would offer new opportunities in nonlinear photonics and revive the nonlinear optical devices.

  7. Formulation of 20(S)-protopanaxadiol nanocrystals to improve oral bioavailability and brain delivery.

    PubMed

    Chen, Chen; Wang, Lisha; Cao, Fangrui; Miao, Xiaoqing; Chen, Tongkai; Chang, Qi; Zheng, Ying

    2016-01-30

    The aim of this study was to fabricate 20(S)-protopanaxadiol (PPD) nanocrystals to improve PPD's oral bioavailability and brain delivery. PPD nanocrystals were fabricated using an anti-solvent precipitation approach where d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) was optimized as the stabilizer. The fabricated nanocrystals were nearly spherical with a particle size and drug loading of 90.44 ± 1.45 nm and 76.92%, respectively. They are in the crystalline state and stable at 4°C for at least 1 month. More than 90% of the PPD could be rapidly released from the nanocrystals, which was much faster than the physical mixture and PPD powder. PPD nanocrystals demonstrated comparable permeability to solution at 2.52 ± 0.44×10(-5)cm/s on MDCK monolayers. After oral administration of PPD nanocrystals to rats, PPD was absorbed quickly into the plasma and brain with significantly higher Cmax and AUC0-t compared to those of the physical mixture. However, no brain targeting was observed, as the ratios of the plasma AUC0-t to brain AUC0-t for the two groups were similar. In summary, PPD nanocrystals are a potential oral delivery system to improve PPD's poor bioavailability and its delivery into the brain for neurodegenerative disease and intracranial tumor therapies in the future.

  8. Nanodisco Balls: Control over Surface versus Core Loading of Diagnostically Active Nanocrystals into Polymer Nanoparticles

    PubMed Central

    2015-01-01

    Nanoparticles of complex architectures can have unique properties. Self-assembly of spherical nanocrystals is a high yielding route to such systems. In this study, we report the self-assembly of a polymer and nanocrystals into aggregates, where the location of the nanocrystals can be controlled to be either at the surface or in the core. These nanospheres, when surface decorated with nanocrystals, resemble disco balls, thus the term nanodisco balls. We studied the mechanism of this surface loading phenomenon and found it to be Ca2+ dependent. We also investigated whether excess phospholipids could prevent nanocrystal adherence. We found surface loading to occur with a variety of nanocrystal types including iron oxide nanoparticles, quantum dots, and nanophosphors, as well as sizes (10–30 nm) and shapes. Additionally, surface loading occurred over a range of polymer molecular weights (∼30–3000 kDa) and phospholipid carbon tail length. We also show that nanocrystals remain diagnostically active after loading onto the polymer nanospheres, i.e., providing contrast in the case of magnetic resonance imaging for iron oxide nanoparticles and fluorescence for quantum dots. Last, we demonstrated that a fluorescently labeled protein model drug can be delivered by surface loaded nanospheres. We present a platform for contrast media delivery, with the unusual feature that the payload can be controllably localized to the core or the surface. PMID:25188401

  9. Using Si-doped diamond plate of sandwich type for spatial profiling of laser beam

    NASA Astrophysics Data System (ADS)

    Shershulin, V. A.; Samoylenko, S. R.; Sedov, V. S.; Kudryavtsev, O. S.; Ralchenko, V. G.; Nozhkina, A. V.; Vlasov, I. I.; Konov, V. I.

    2017-02-01

    We demonstrated a laser beam profiling method based on imaging of the laser induced photoluminescence of a transparent single-crystal diamond plate. The luminescence at 738 nm is caused by silicon-vacancy color centers formed in the epitaxial diamond film by its doping with Si during CVD growth of the film. The on-line beam monitor was tested for a cw laser emitting at 660 nm wavelength.

  10. Transmission-mode diamond white-beam position monitor at NSLS.

    PubMed

    Muller, Erik M; Smedley, John; Bohon, Jen; Yang, Xi; Gaowei, Mengjia; Skinner, John; De Geronimo, Gianluigi; Sullivan, Michael; Allaire, Marc; Keister, Jeffrey W; Berman, Lonny; Héroux, Annie

    2012-05-01

    Two transmission-mode diamond X-ray beam position monitors installed at National Synchrotron Light Source (NSLS) beamline X25 are described. Each diamond beam position monitor is constructed around two horizontally tiled electronic-grade (p.p.b. nitrogen impurity) single-crystal (001) CVD synthetic diamonds. The position, angle and flux of the white X-ray beam can be monitored in real time with a position resolution of 500 nm in the horizontal direction and 100 nm in the vertical direction for a 3 mm × 1 mm beam. The first diamond beam position monitor has been in operation in the white beam for more than one year without any observable degradation in performance. The installation of a second, more compact, diamond beam position monitor followed about six months later, adding the ability to measure the angular trajectory of the photon beam.

  11. Transmission-mode diamond white-beam position monitor at NSLS

    PubMed Central

    Muller, Erik M.; Smedley, John; Bohon, Jen; Yang, Xi; Gaowei, Mengjia; Skinner, John; De Geronimo, Gianluigi; Sullivan, Michael; Allaire, Marc; Keister, Jeffrey W.; Berman, Lonny; Héroux, Annie

    2012-01-01

    Two transmission-mode diamond X-ray beam position monitors installed at National Synchrotron Light Source (NSLS) beamline X25 are described. Each diamond beam position monitor is constructed around two horizontally tiled electronic-grade (p.p.b. nitrogen impurity) single-crystal (001) CVD synthetic diamonds. The position, angle and flux of the white X-ray beam can be monitored in real time with a position resolution of 500 nm in the horizontal direction and 100 nm in the vertical direction for a 3 mm × 1 mm beam. The first diamond beam position monitor has been in operation in the white beam for more than one year without any observable degradation in performance. The installation of a second, more compact, diamond beam position monitor followed about six months later, adding the ability to measure the angular trajectory of the photon beam. PMID:22514173

  12. Fluidized bed deposition of diamond

    DOEpatents

    Laia, Jr., Joseph R.; Carroll, David W.; Trkula, Mitchell; Anderson, Wallace E.; Valone, Steven M.

    1998-01-01

    A process for coating a substrate with diamond or diamond-like material including maintaining a substrate within a bed of particles capable of being fluidized, the particles having substantially uniform dimensions and the substrate characterized as having different dimensions than the bed particles, fluidizing the bed of particles, and depositing a coating of diamond or diamond-like material upon the substrate by chemical vapor deposition of a carbon-containing precursor gas mixture, the precursor gas mixture introduced into the fluidized bed under conditions resulting in excitation mechanisms sufficient to form the diamond coating.

  13. Si nanocrystals and nanocrystal interfaces studied by positron annihilation

    NASA Astrophysics Data System (ADS)

    Kujala, J.; Slotte, J.; Tuomisto, F.; Hiller, D.; Zacharias, M.

    2016-10-01

    Si nanocrystals embedded in a SiO 2 matrix were studied with positron annihilation and photoluminescence spectroscopies. Analysis of the S- and W-parameters for the sample annealed at 800 °C reveals a positron trap at the interface between the amorphous nanodots and the surrounding matrix. Another trap state is observed in the 1150 °C heat treated samples where nanodots are in a crystalline form. Positrons are most likely trapped to defects related to dangling bonds at the surface of the nanocrystals. Passivation of the samples results on one hand in the decrease of the S-parameter implying a decrease in the open volume of the interface state and, on the other hand, in the strengthening of the positron annihilation signal from the interface. The intensity of the photoluminescence signal increases with the formation of the nanocrystals. Passivation of samples strengthens the photoluminescence signal, further indicating a successful deactivation of luminescence quenching at the nanocrystal surface. Strengthening of the positron annihilation signal and an increase in the photoluminescence intensity in passivated silicon nanocrystals suggests that the positron trap at the interface does not contribute to a significant extent to the exciton recombination in the nanocrystals.

  14. Synthesis and Doping of Silicon Nanocrystals for Versatile Nanocrystal Inks

    NASA Astrophysics Data System (ADS)

    Kramer, Nicolaas Johannes

    The impact of nanotechnology on our society is getting larger every year. Electronics are becoming smaller and more powerful, the "Internet of Things" is all around us, and data generation is increasing exponentially. None of this would have been possible without the developments in nanotechnology. Crystalline semiconductor nanoparticles (nanocrystals) are one of the latest developments in the field of nanotechnology. This thesis addresses three important challenges for the transition of silicon nanocrystals from the lab bench to the marketplace: A better understanding of the nanocrystal synthesis was obtained, the electronic properties of the nanocrystals were characterized and tuned, and novel silicon nanocrystal inks were formed and applied using simple coating technologies. Plasma synthesis of nanocrystals has numerous advantages over traditional solution-based synthesis methods. While the formation of nanoparticles in low pressure nonthermal plasmas is well known, the heating mechanism leading to their crystallization is poorly understood. A combination of comprehensive plasma characterization with a nanoparticle heating model presented here reveals the underlying plasma physics leading to crystallization. The model predicts that the nanoparticles reach temperatures as high as 900 K in the plasma as a result of heating reactions on the nanoparticle surface. These temperatures are well above the gas temperature and sufficient for complete nanoparticle crystallization. Moving the field of plasma nanoparticle synthesis to atmospheric pressures is important for lowering its cost and making the process attractive for industrial applications. The heating and charging model for silicon nanoparticles was adapted in Chapter 3 to study plasmas maintained over a wide range of pressures (10 -- 105 Pa). The model considers three collisionality regimes and determines the dominant contribution of each regime under various plasma conditions. Strong nanoparticle cooling at

  15. Singlet Oxygen Generation Mediated By Silicon Nanocrystal Assemblies

    DTIC Science & Technology

    2011-01-01

    network. Structural investigations have confirmed that PSi layers consist of Si nanocrystals having sizes dependent mainly on the doping level of...porosified Si grains consist from almost ideal nanosilicon spheres with mean size ~ 5 nm (see Fig. 4 a). For this range of sizes quantum confinement...Therefore, to obtain reliable luminescence data, solvents consisting of poor quenchers have been chosen. Fig. 15 demonstrates spectroscopic

  16. Low temperature thin films formed from nanocrystal precursors

    DOEpatents

    Alivisatos, A. Paul; Goldstein, Avery N.

    1993-01-01

    Nanocrystals of semiconductor compounds are produced. When they are applied as a contiguous layer onto a substrate and heated they fuse into a continuous layer at temperatures as much as 250, 500, 750 or even 1000.degree. K below their bulk melting point. This allows continuous semiconductor films in the 0.25 to 25 nm thickness range to be formed with minimal thermal exposure.

  17. Low temperature thin films formed from nanocrystal precursors

    DOEpatents

    Alivisatos, A.P.; Goldstein, A.N.

    1993-11-16

    Nanocrystals of semiconductor compounds are produced. When they are applied as a contiguous layer onto a substrate and heated they fuse into a continuous layer at temperatures as much as 250, 500, 750 or even 1000 K below their bulk melting point. This allows continuous semiconductor films in the 0.25 to 25 nm thickness range to be formed with minimal thermal exposure. 9 figures.

  18. A Novel Thermal Electrochemical Synthesis Method for Production of Stable Colloids of "Naked" Metal (Ag) Nanocrystals

    SciTech Connect

    Hu, Michael Z.; Easterly, Clay E

    2009-01-01

    Solution synthesis of nanocrystal silver is reviewed. This paper reports a novel thermal electrochemical synthesis (TECS) for producing metal Ag nanocrystals as small as a few nanometers. The TECS method requires mild conditions (25-100oC), low voltage (1-50 V DC) on Ag electrodes, and simple water or aqueous solutions as reaction medium. Furthermore, a tubular dialysis membrane surround electrodes proves favorable to produce nanosized (<10 nm) Ag nanocrystals. Different from those nanocrystals reported in literature, our nanocrystals have several unique features: (1) small nanometer size, (2) nakedness , i.e., surfaces of metal nanocrystals are free of organic ligands or capping molecules and no need of dispersant in synthesis solutions, and (3) colloidally stable in water solutions. It was discovered that Ag nanoparticles with initially large size distribution can be homogenized into near-monodispersed system by a low power (< 15 mW) He-Ne laser exposure treatment. The combination of the TECS technique and the laser treatment could lead to a new technology that produces metal nanoparticles that are naked, stable, and uniform sized. In the presence of stabilizing agent (also as supporting electrolyte) such as polyvinyl alcohol (PVA), large yield of silver nanoparticles (<100nm) in the form of thick milky sols are produced.

  19. Deposition and characterization of diamond thin films by HF-CVD method

    SciTech Connect

    Mishra, S. C. Choudhary, R. K.; Mishra, P.; Abraham, G. J.

    2015-06-24

    Effect of reactor pressure and methane gas concentration on the growth of diamond films on Si (100) substrate by hot filament chemical vapor deposition (HFCVD) method has been studied in this work. Raman spectroscopy measurements of the obtained film confirmed the formation of a mixture of micro and nanocrystalline diamond by showing peaks at 1140 and 1334 cm{sup −1} wave shifts. Scanning electron microscopy results showed formation of well defined faceted diamond grains of 100–500 nm size. Average roughness of the films measured by a surface profilometer was in the range of 40–60 nm.

  20. Research Update: Direct conversion of amorphous carbon into diamond at ambient pressures and temperatures in air

    SciTech Connect

    Narayan, Jagdish Bhaumik, Anagh

    2015-10-01

    We report on fundamental discovery of conversion of amorphous carbon into diamond by irradiating amorphous carbon films with nanosecond lasers at room-temperature in air at atmospheric pressure. We can create diamond in the form of nanodiamond (size range <100 nm) and microdiamond (>100 nm). Nanosecond laser pulses are used to melt amorphous diamondlike carbon and create a highly undercooled state, from which various forms of diamond can be formed upon cooling. The quenching from the super undercooled state results in nucleation of nanodiamond. It is found that microdiamonds grow out of highly undercooled state of carbon, with nanodiamond acting as seed crystals.

  1. DIAMOND AMPLIFIED PHOTOCATHODES.

    SciTech Connect

    SMEDLEY,J.; BEN-ZVI, I.; BOHON, J.; CHANG, X.; GROVER, R.; ISAKOVIC, A.; RAO, T.; WU, Q.

    2007-11-26

    High-average-current linear electron accelerators require photoinjectors capable of delivering tens to hundreds of mA average current, with peak currents of hundreds of amps. Standard photocathodes face significant challenges in meeting these requirements, and often have short operational lifetimes in an accelerator environment. We report on recent progress toward development of secondary emission amplifiers for photocathodes, which are intended to increase the achievable average current while protecting the cathode from the accelerator. The amplifier is a thin diamond wafer which converts energetic (few keV) primary electrons into hundreds of electron-hole pairs via secondary electron emission. The electrons drift through the diamond under an external bias and are emitted into vacuum via a hydrogen-terminated surface with negative electron affinity (NEA). Secondary emission gain of over 200 has been achieved. Two methods of patterning diamond, laser ablation and reactive-ion etching (RIE), are being developed to produce the required geometry. A variety of diagnostic techniques, including FTIR, SEM and AFM, have been used to characterize the diamonds.

  2. 'Diamond' in 3-D

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This 3-D, microscopic imager mosaic of a target area on a rock called 'Diamond Jenness' was taken after NASA's Mars Exploration Rover Opportunity ground into the surface with its rock abrasion tool for a second time.

    Opportunity has bored nearly a dozen holes into the inner walls of 'Endurance Crater.' On sols 177 and 178 (July 23 and July 24, 2004), the rover worked double-duty on Diamond Jenness. Surface debris and the bumpy shape of the rock resulted in a shallow and irregular hole, only about 2 millimeters (0.08 inch) deep. The final depth was not enough to remove all the bumps and leave a neat hole with a smooth floor. This extremely shallow depression was then examined by the rover's alpha particle X-ray spectrometer.

    On Sol 178, Opportunity's 'robotic rodent' dined on Diamond Jenness once again, grinding almost an additional 5 millimeters (about 0.2 inch). The rover then applied its Moessbauer spectrometer to the deepened hole. This double dose of Diamond Jenness enabled the science team to examine the rock at varying layers. Results from those grindings are currently being analyzed.

    The image mosaic is about 6 centimeters (2.4 inches) across.

  3. CVD diamond - fundamental phenomena

    SciTech Connect

    Yarbrough, W.A.

    1993-01-01

    This compilation of figures and diagrams addresses the basic physical processes involved in the chemical vapor deposition of diamond. Different methods of deposition are illustrated. For each method, observations are made of the prominent advantages and disadvantages of the technique. Chemical mechanisms of nucleation are introduced.

  4. California: Diamond Valley

    Atmospheric Science Data Center

    2014-05-15

    ... water storage capacity. In addition to routine water management, Diamond Valley Lake is designed to provide protection against ... 20, 2001 (Terra orbit 7564), is a false-color view combining data from the instrument's 26-degree forward view (displayed as blue) with data ...

  5. ELECTRON AMPLIFICATION IN DIAMOND.

    SciTech Connect

    SMEDLEY, J.; BEN-ZVI, I.; BURRILL, A.; CHANG, X.; GRIMES, J.; RAO, T.; SEGALOV, Z.; WU, Q.

    2006-07-10

    We report on recent progress toward development of secondary emission ''amplifiers'' for photocathodes. Secondary emission gain of over 300 has been achieved in transmission mode and emission mode for a variety of diamond samples. Techniques of sample preparation, including hydrogenation to achieve negative electron affinity (NEA), have been adapted to this application.

  6. Diamond growth in mantle fluids

    NASA Astrophysics Data System (ADS)

    Bureau, Hélène; Frost, Daniel J.; Bolfan-Casanova, Nathalie; Leroy, Clémence; Esteve, Imène; Cordier, Patrick

    2016-11-01

    In the upper mantle, diamonds can potentially grow from various forms of media (solid, gas, fluid) with a range of compositions (e.g. graphite, C-O-H fluids, silicate or carbonate melts). Inclusions trapped in diamonds are one of the few diagnostic tools that can constrain diamond growth conditions in the Earth's mantle. In this study, inclusion-bearing diamonds have been synthesized to understand the growth conditions of natural diamonds in the upper mantle. Diamonds containing syngenetic inclusions were synthesized in multi-anvil presses employing starting mixtures of carbonates, and silicate compositions in the presence of pure water and saline fluids (H2O-NaCl). Experiments were performed at conditions compatible with the Earth's geotherm (7 GPa, 1300-1400 °C). Results show that within the timescale of the experiments (6 to 30 h) diamond growth occurs if water and carbonates are present in the fluid phase. Water promotes faster diamond growth (up to 14 mm/year at 1400 °C, 7 GPa, 10 g/l NaCl), which is favorable to the inclusion trapping process. At 7 GPa, temperature and fluid composition are the main factors controlling diamond growth. In these experiments, diamonds grew in the presence of two fluids: an aqueous fluid and a hydrous silicate melt. The carbon source for diamond growth must be carbonate (CO32) dissolved in the melt or carbon dioxide species in the aqueous fluid (CO2aq). The presence of NaCl affects the growth kinetics but is not a prerequisite for inclusion-bearing diamond formation. The presence of small discrete or isolated volumes of water-rich fluids is necessary to grow inclusion-bearing peridotitic, eclogitic, fibrous, cloudy and coated diamonds, and may also be involved in the growth of ultradeep, ultrahigh-pressure metamorphic diamonds.

  7. White light emission and optical gains from a Si nanocrystal thin film

    NASA Astrophysics Data System (ADS)

    Wang, Dong-Chen; Hao, Hong-Chen; Chen, Jia-Rong; Zhang, Chi; Zhou, Jing; Sun, Jian; Lu, Ming

    2015-11-01

    We report a Si nanocrystal thin film consisting of free-standing Si nanocrystals, which can emit white light and show positive optical gains for its red, green and blue (RGB) components under ultraviolet excitation. Si nanocrystals with ϕ = 2.31 ± 0.35 nm were prepared by chemical etching of Si powder, followed by filtering. After being mixed with SiO2 sol-gel and thermally annealed, a broadband photoluminescence (PL) from the thin film was observed. The RGB ratio of the PL can be tuned by changing the annealing temperature or atmosphere, which is 1.00/3.26/4.59 for the pure white light emission. The origins of the PL components could be due to differences in oxygen-passivation degree for Si nanocrystals. The results may find applications in white-light Si lasing and Si lighting.

  8. Low Temperature Synthesis of Rutile TiO2 Nanocrystals and Their Photovoltaic and Photocatalytic Properties.

    PubMed

    Roy, Subhasis; Han, Gill Sang; Shin, Hyunjung; Lee, Jin Wook; Mun, Jinsoo; Shin, Hyunho; Jung, Hyun Suk

    2015-06-01

    We report a novel method of synthesizing rutile TiO2 nanocrystals at low temperature (200 degrees C) via a butanol rinsing process followed by heat treatment in an O2 atmosphere. The rutile nanocrystals show uniform size distribution of approximately 20 nm and good crystallinity confirmed by X-ray diffraction and transmission electron microscopy. A mechanism for the low temperature synthesis of rutile nanocrystals is rationalized in terms of an explosive thermal decomposition reaction of butoxy groups on TiO2 powders with O2 gas. Characterizations of the photovoltaic and photocatalytic properties of rutile nanocrystals exhibited higher photoactivity than large-sized conventional rutile powder, which demonstrates that this novel synthesis technology could expand applications of rutile powders to various photoactive devices beyond solar cells and photocatalysts.

  9. White light emission and optical gains from a Si nanocrystal thin film.

    PubMed

    Wang, Dong-Chen; Hao, Hong-Chen; Chen, Jia-Rong; Zhang, Chi; Zhou, Jing; Sun, Jian; Lu, Ming

    2015-11-27

    We report a Si nanocrystal thin film consisting of free-standing Si nanocrystals, which can emit white light and show positive optical gains for its red, green and blue (RGB) components under ultraviolet excitation. Si nanocrystals with ϕ = 2.31 ± 0.35 nm were prepared by chemical etching of Si powder, followed by filtering. After being mixed with SiO2 sol-gel and thermally annealed, a broadband photoluminescence (PL) from the thin film was observed. The RGB ratio of the PL can be tuned by changing the annealing temperature or atmosphere, which is 1.00/3.26/4.59 for the pure white light emission. The origins of the PL components could be due to differences in oxygen-passivation degree for Si nanocrystals. The results may find applications in white-light Si lasing and Si lighting.

  10. Synthesis of highly luminescent mercaptosuccinic acid-coated CdSe nanocrystals under atmospheric conditions.

    PubMed

    Dong, Meiting; Xu, Jingyi; Liu, Shuxian; Zhou, Ying; Huang, Chaobiao

    2014-11-01

    Here we report a facile one-pot method for the preparation of high-quality CdSe nanocrystals (NCs) in aqueous solution under an air atmosphere. Compared with the traditional use of NaHSe or H2 Se, the more stable sodium selenite is utilized as the Se source for preparing highly luminescent CdSe nanocrystals. By using mercaptosuccinic acid (MSA) as the capping agent and borate-citrate acid as the buffering solution, CdSe nanocrystals with high quantum yield (up to 70%) have been synthesized conveniently. The influence of different experimental parameters, such as the pH of the precursor solution, the molar ratio of Cd(2+) to Na2 SeO3 and Cd(2+) to MSA on the CdSe nanocrystals, has been systematically investigated. The prepared CdSe NCs were spherical with a size of ~ 5 nm.

  11. Tuning the formation and functionalities of ultrafine CoFe2O4 nanocrystals via interfacial coherent strain.

    PubMed

    Hsieh, Ying-Hui; Kuo, Ho-Hung; Liao, Sheng-Chieh; Liu, Heng-Jui; Chen, Ying-Jiun; Lin, Hong-Ji; Chen, Chien-Te; Lai, Chih-Huang; Zhan, Qian; Chueh, Yu-Lun; Chu, Ying-Hao

    2013-07-21

    Complex oxide nanocrystals with a spinel structure show their remarkable optical, electronic, mechanical, thermal, and magnetic properties. In this study, we present a simple yet versatile strategy to grow self-assembled epitaxial CoFe2O4 nanocrystals with well-controlled size (less than 10 nm) and single orientation. CoFe2O4 nanocrystals were fabricated via phase separation in a BiFeO3-CoF2O4 ultrathin film by pulsed laser deposition. The coherent strain at the BiFeO3-CoF2O4 interface suppressed the growth of the nanocrystals regardless of substrate temperatures. This strain also resulted in the ferromagnetic anisotropy and interesting conducting behaviors of ultrafine CFO nanocrystals.

  12. Preparation of ternary Cd1- x Zn x S nanocrystals with tunable ultraviolet absorption by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Zhang, Qi; Zhang, Huihui; Liu, Limin; Li, Shaohua; Murowchick, James B.; Wisner, Clarissa; Leventis, Nickolas; Peng, Zhonghua; Tan, Guolong

    2015-03-01

    Composition-tunable ternary Cd1- x Zn x S nanocrystals are among the most extensively studied alloyed semiconductor nanocrystals. However, they are almost exclusively prepared by wet chemical routes, which lead to surface-capped nanoparticles. Herein, we present a simple mechanical alloying process to prepare uncapped Zn1- x Cd x S nanocrystals throughout the entire composition range. The resulting nanocrystals have average sizes smaller than 9 nm, are chemically homogenous, and exhibit linear lattice parameter-composition and close-to-linear band-gap-composition relationships. Continuous lattice contraction of the Cd1- x Zn x S nanocrystals with the atomic Zn concentration results in a successional enlargement of their band gap energies expanding from the visible region to the ultraviolet (UV) region, demonstrating the ability for precise control of band gap engineering through composition tuning and mechanical alloying. [Figure not available: see fulltext.

  13. A facile and green preparation of high-quality CdTe semiconductor nanocrystals at room temperature

    NASA Astrophysics Data System (ADS)

    Liu, Yan; Shen, Qihui; Yu, Dongdong; Shi, Weiguang; Li, Jixue; Zhou, Jianguang; Liu, Xiaoyang

    2008-06-01

    One chemical reagent, hydrazine hydrate, was discovered to accelerate the growth of semiconductor nanocrystals (cadmium telluride) instead of additional energy, which was applied to the synthesis of high-quality CdTe nanocrystals at room temperature and ambient conditions within several hours. Under this mild condition the mercapto stabilizers were not destroyed, and they guaranteed CdTe nanocrystal particle sizes with narrow and uniform distribution over the largest possible range. The CdTe nanocrystals (photoluminescence emission range of 530-660 nm) synthesized in this way had very good spectral properties; for instance, they showed high photoluminescence quantum yield of up to 60%. Furthermore, we have succeeded in detecting the living Borrelia burgdorferi of Lyme disease by its photoluminescence image using CdTe nanocrystals.

  14. TEM studies of Ge nanocrystal formation in PECVD grown SiO2:Ge/SiO2 multilayers

    NASA Astrophysics Data System (ADS)

    Agan, S.; Dana, A.; Aydinli, A.

    2006-06-01

    We investigate the effect of annealing on the Ge nanocrystal formation in multilayered germanosilicate-oxide films grown on Si substrates by plasma enhanced chemical vapour deposition (PECVD). The multilayered samples were annealed at temperatures ranging from 750 to 900 °C for 5 min under nitrogen atmosphere. The onset of formation of Ge nanocrystals, at 750 °C, can be observed via high resolution TEM micrographs. The diameters of Ge nanocrystals were observed to be between 5 and 14 nm. As the annealing temperature is raised to 850 °C, a second layer of Ge nanocrystals forms next to the original precipitation band, positioning itself closer to the substrate SiO2 interface. High resolution cross section TEM images, electron diffraction and electron energy-loss spectroscopy as well as energy-dispersive x-ray analysis (EDAX) data all indicate that Ge nanocrystals are present in each layer.

  15. Diamond film deposition using microwave plasmas under low pressures

    NASA Technical Reports Server (NTRS)

    Shing, Y. H.; Pool, F. S.; Rich, D. H.

    1991-01-01

    Microwave plasma depositions of diamond films have been investigated under low pressures of 10 mTorr to 10 Torr, at low substrate temperatures of 400 to 750 C, using high methane concentrations of 5 to 15 percent and oxygen concentrations of 5 to 10 percent in hydrogen plasmas. The deposition system consists of a microwave plasma chamber, a downstream deposition chamber, and a RF induction-heated sample stage. The deposition system can be operated in either high-pressure microwave or electron cyclotron resonance (ECR) modes by varying the sample stage position. Cathodoluminescence (CL) studies on diamond films deposited at 10 Torr pressure show that CL emissions at 430, 480, 510, 530, 560, 570 and 740 nm can be employed to characterize the quality of diamond films. High-quality, well-faceted diamond films have been deposited at 10 Torr and 600 C using 5 percent CH4 and 5 percent O2 in H2 plasmas; CL measurements on these films show very low N impurities and no detectable Si impurities. Diamond nucleation on SiC has been demonstrated by depositing well-faceted diamond crystallites on SiC-coated Si substrates.

  16. Structural peculiarities of single crystal diamond needles of nanometer thickness

    NASA Astrophysics Data System (ADS)

    Orekhov, Andrey S.; Tuyakova, Feruza T.; Obraztsova, Ekaterina A.; Loginov, Artem B.; Chuvilin, Andrey L.; Obraztsov, Alexander N.

    2016-11-01

    Diamond is attractive for various applications due to its unique mechanical and optical properties. In particular, single crystal diamond needles with high aspect ratios and sharp apexes of nanometer size are demanded for different types of optical sensors including optically sensing tip probes for scanning microscopy. This paper reports on electron microscopy and Raman spectroscopy characterization of the diamond needles having geometrically perfect pyramidal shapes with rectangular atomically flat bases with (001) crystallography orientation, 2-200 nm sharp apexes, and with lengths from about 10-160 μm. The needles were produced by selective oxidation of (001) textured polycrystalline diamond films grown by chemical vapor deposition. Here we study the types and distribution of defects inside and on the surface of the single crystal diamond needles. We show that sp3 type point defects are incorporated into the volume of the diamond crystal during growth, while the surface of the lateral facets is enriched by multiple extended defects. Nitrogen addition to the reaction mixture results in increase of the growth rate on {001} facets correlated with the rise in the concentration of sp3 type defects.

  17. Luminescence mechanisms in 6H-SiC nanocrystals

    NASA Astrophysics Data System (ADS)

    Botsoa, J.; Bluet, J. M.; Lysenko, V.; Sfaxi, L.; Zakharko, Y.; Marty, O.; Guillot, G.

    2009-10-01

    Experimental conditions allowing consequent selection of a dominating photoluminescence mechanism in 6H-SiC nanocrystals at room temperature are reported. Electrostatic screening of surface states involved in radiative transitions can be efficiently achieved by polar ethanol molecules. This leads to a preponderant radiative channel between the electronic levels corresponding to the impurity atoms (N and Al). This radiative channel is deactivated by centrifugation-induced selection of the smallest colloidal 6H-SiC nanocrystals in which the probability to have both donor and acceptor atoms is negligible. Consequently, for these smallest 6H-SiC nanocrystals with switched off transitions between surface states and impurity levels, quantum-confinement effect can be clearly observed. The formation of energy subbands in the 6H-SiC nanocrystals is then evidenced from photoluminescence excitation and absorption measurements performed on the centrifuged colloidal nanosuspension. A most probable mean diameter of 1.9 nm for these particles is deduced from calculation of energy levels in the effective-mass approximation.

  18. Precursor conversion kinetics and the nucleation of cadmium selenide nanocrystals.

    PubMed

    Owen, Jonathan S; Chan, Emory M; Liu, Haitao; Alivisatos, A Paul

    2010-12-29

    The kinetics of cadmium selenide (CdSe) nanocrystal formation was studied using UV-visible absorption spectroscopy integrated with an automated, high-throughput synthesis platform. Reaction of anhydrous cadmium octadecylphosphonate (Cd-ODPA) with alkylphosphine selenides (1, tri-n-octylphosphine selenide; 2, di-n-butylphenylphosphine selenide; 3, n-butyldiphenylphosphine selenide) in recrystallized tri-n-octylphosphine oxide was monitored by following the absorbance of CdSe at λ = 350 nm, where the extinction coefficient is independent of size, and the disappearance of the selenium precursor using {(1)H}(31)P NMR spectroscopy. Our results indicate that precursor conversion limits the rate of nanocrystal nucleation and growth. The initial precursor conversion rate (Q(o)) depends linearly on [1] (Q(o)(1) = 3.0-36 μM/s) and decreases as the number of aryl groups bound to phosphorus increases (1 > 2 > 3). Changes to Q(o) influence the final number of nanocrystals and thus control particle size. Using similar methods, we show that changing [ODPA] has a negligible influence on precursor reactivity while increasing the growth rate of nuclei, thereby decreasing the final number of nanocrystals. These results are interpreted in light of a mechanism where the precursors react in an irreversible step that supplies the reaction medium with a solute form of the semiconductor.

  19. Assemblies of Cellulose Nanocrystals

    NASA Astrophysics Data System (ADS)

    Kumacheva, Eugenia

    The entropically driven coassembly of nanorods (cellulose nanocrystals, CNCs) and different types of nanoparticles (NPs), including dye-labeled latex NPs, carbon dots and plasmonic NPs was experimentally studied in aqueous suspensions and in solid films. In mixed CNC-NP suspensions, phase separation into an isotropic NP-rich and a chiral nematic CNC-rich phase took place; the latter contained a significant amount of NPs. Drying the mixed suspension resulted in CNC-NP films with planar disordered layers of NPs, which alternated with chiral nematic CNC-rich regions. In addition, NPs were embedded in the chiral nematic domains. The stratified morphology of the films, together with a random distribution of NPs in the anisotropic phase, led to the films having close-to-uniform fluorescence, birefringence, and circular dichroism properties.

  20. Morphology evolution of single-crystalline hematite nanocrystals: magnetically recoverable nanocatalysts for enhanced facet-driven photoredox activity

    NASA Astrophysics Data System (ADS)

    Patra, Astam K.; Kundu, Sudipta K.; Bhaumik, Asim; Kim, Dukjoon

    2015-12-01

    We have developed a new green chemical approach for the shape-controlled synthesis of single-crystalline hematite nanocrystals in aqueous medium. FESEM, HRTEM and SAED techniques were used to determine the morphology and crystallographic orientations of each nanocrystal and its exposed facets. PXRD and HRTEM techniques revealed that the nanocrystals are single crystalline in nature; twins and stacking faults were not detected in these nanocrystals. The structural, vibrational, and electronic spectra of these nanocrystals were highly dependent on their shape. Different shaped hematite nanocrystals with distinct crystallographic planes have been synthesized under similar reaction conditions, which can be desired as a model for the purpose of properties comparison with the nanocrystals prepared under different reaction conditions. Here we investigated the photocatalytic performance of these different shaped-nanocrystals for methyl orange degradation in the presence of white light (λ > 420 nm). In this study, we found that the density of surface Fe3+ ions in particular facets was the key factor for the photocatalytic activity and was higher on the bitruncated-dodecahedron shape nanocrystals by coexposed {104}, {100} and {001} facets, attributing to higher catalytic activity. The catalytic activity of different exposed facet nanocrystals were as follows: {104} + {100} + {001} (bitruncated-dodecahedron) > {101} + {001} (bitruncated-octahedron) > {001} + {110} (nanorods) > {012} (nanocuboid) which provided the direct evidence of exposed facet-driven photocatalytic activity. The nanocrystals were easily recoverable using an external magnet and reused at least six times without significant loss of its catalytic activity.We have developed a new green chemical approach for the shape-controlled synthesis of single-crystalline hematite nanocrystals in aqueous medium. FESEM, HRTEM and SAED techniques were used to determine the morphology and crystallographic orientations of

  1. Lower pressure synthesis of diamond material

    DOEpatents

    Lueking, Angela; Gutierrez, Humberto; Narayanan, Deepa; Burgess Clifford, Caroline E.; Jain, Puja

    2010-07-13

    Methods of synthesizing a diamond material, particularly nanocrystalline diamond, diamond-like carbon and bucky diamond are provided. In particular embodiments, a composition including a carbon source, such as coal, is subjected to addition of energy, such as high energy reactive milling, producing a milling product enriched in hydrogenated tetrahedral amorphous diamond-like carbon compared to the coal. A milling product is treated with heat, acid and/or base to produce nanocrystalline diamond and/or crystalline diamond-like carbon. Energy is added to produced crystalline diamond-like carbon in particular embodiments to produce bucky diamonds.

  2. Nanocrystals for dermal penetration enhancement - Effect of concentration and underlying mechanisms using curcumin as model.

    PubMed

    Vidlářová, Lucie; Romero, Gregori B; Hanuš, Jaroslav; Štěpánek, František; Müller, Rainer H

    2016-07-01

    Nanocrystals have received considerable attention in dermal application due to their ability to enhance delivery to the skin and overcome bioavailability issues caused by poor water and oil drug solubility. The objective of this study was to investigate the effect of nanocrystals on the mechanism of penetration behavior of curcumin as a model drug. Curcumin nanocrystals were produced by the smartCrystals® process, i.e. bead milling followed by high pressure homogenization. The mean particle size of the curcumin crystals was about 200nm. Stabilization was performed with alkyl polyglycoside surfactants. The distribution of curcumin within the skin was determined in vitro on cross-sections of porcine skin and visualized by fluorescent microscopy. The skin penetration profile was analyzed for the curcumin nanosuspension with decreasing concentrations (2%, 0.2%, 0.02% and 0.002% by weight) and compared to nanocrystals in a viscous hydroxypropylcellulose (HPC) gel. This study demonstrated there was minor difference between low viscous nanosuspension and the gel, but low viscosity seemed to favor skin penetration. Localization of curcumin was observed in the hair follicles, also contributing to skin uptake. Looking at the penetration of curcumin from formulations with decreasing nanocrystal concentration, formulations with 2%, 0.2% and 0.02% showed a similar penetration profile, whereas a significantly weaker fluorescence was observed in the case of a formulation containing 0.002% of curcumin nanocrystals. In this study we have shown that curcumin nanocrystals prepared by the smartCrystal® process are promising carriers in dermal application and furthermore, we identified the ideal concentration of 0.02% nanocrystals in dermal formulations. The comprehensive study of decreasing curcumin concentration in formulations revealed that the saturation solubility (Cs) is not the only determining factor for the penetration. A new mechanism based also on the concentration of the

  3. A facile arrested precipitation method for synthesis of pure wurtzite Cu{sub 2}ZnSnS{sub 4} nanocrystals using thiourea as a sulfur source

    SciTech Connect

    Li, Chunya; Ha, Enna; Wong, Wing-Leung; Li, Cuiling; Ho, Kam-Piu; Wong, Kwok-Yin

    2012-11-15

    Graphical abstract: High-resolution TEM image of wurtzite Cu{sub 2}ZnSnS{sub 4} nanocrystals. Highlights: ► Wurtzite Cu{sub 2}ZnSnS{sub 4} nanocrystals were synthesized by arrested precipitation method. ► XRD, EDX, TEM demonstrate that the CZTS nanocrystals are purely wurtzite structure. ► The average diameter of the bulk CZTS products is found to be 10 ± 1.1 nm. ► The estimated direct bandgap energy is 1.56 eV for wurtzite CZTS nanocrystals. ► The electrical resistivity of the wurtzite CZTS nanocrystals is low. -- Abstract: A facile route for the synthesis of wurtzite Cu{sub 2}ZnSnS{sub 4} (CZTS) nanocrystals was developed by an arrested precipitation method at 240 °C under simple reaction conditions with diethanolamine as the solvent and thiourea as sulfur source. The structure and morphology of the CZTS nanocrystals were characterized by X-ray diffraction and transmission electron microscopy. Control experiments demonstrated that CZTS nanocrystals which are purely wurtzite structure are readily obtained. The average diameter of the bulk CZTS products is found to be 10 ± 1.1 nm. The estimated direct bandgap energy is 1.56 eV, which indicates that the CZTS nanocrystals produced by this method possess promising applications in photovoltaic devices.

  4. 31 CFR 592.310 - Rough diamond.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 31 Money and Finance:Treasury 3 2011-07-01 2011-07-01 false Rough diamond. 592.310 Section 592.310... ASSETS CONTROL, DEPARTMENT OF THE TREASURY ROUGH DIAMONDS CONTROL REGULATIONS General Definitions § 592.310 Rough diamond. The term rough diamond means any diamond that is unworked or simply sawn,...

  5. 31 CFR 592.310 - Rough diamond.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 31 Money and Finance:Treasury 3 2012-07-01 2012-07-01 false Rough diamond. 592.310 Section 592.310... ASSETS CONTROL, DEPARTMENT OF THE TREASURY ROUGH DIAMONDS CONTROL REGULATIONS General Definitions § 592.310 Rough diamond. The term rough diamond means any diamond that is unworked or simply sawn,...

  6. 31 CFR 592.310 - Rough diamond.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 31 Money and Finance:Treasury 3 2014-07-01 2014-07-01 false Rough diamond. 592.310 Section 592.310... ASSETS CONTROL, DEPARTMENT OF THE TREASURY ROUGH DIAMONDS CONTROL REGULATIONS General Definitions § 592.310 Rough diamond. The term rough diamond means any diamond that is unworked or simply sawn,...

  7. 31 CFR 592.310 - Rough diamond.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 31 Money and Finance:Treasury 3 2013-07-01 2013-07-01 false Rough diamond. 592.310 Section 592.310... ASSETS CONTROL, DEPARTMENT OF THE TREASURY ROUGH DIAMONDS CONTROL REGULATIONS General Definitions § 592.310 Rough diamond. The term rough diamond means any diamond that is unworked or simply sawn,...

  8. 31 CFR 592.310 - Rough diamond.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 31 Money and Finance: Treasury 3 2010-07-01 2010-07-01 false Rough diamond. 592.310 Section 592... FOREIGN ASSETS CONTROL, DEPARTMENT OF THE TREASURY ROUGH DIAMONDS CONTROL REGULATIONS General Definitions § 592.310 Rough diamond. The term rough diamond means any diamond that is unworked or simply...

  9. Elucidating the in vivo fate of nanocrystals using a physiologically based pharmacokinetic model: a case study with the anticancer agent SNX-2112

    PubMed Central

    Dong, Dong; Wang, Xiao; Wang, Huailing; Zhang, Xingwang; Wang, Yifei; Wu, Baojian

    2015-01-01

    Introduction SNX-2112 is a promising anticancer agent but has poor solubility in both water and oil. In the study reported here, we aimed to develop a nanocrystal formulation for SNX-2112 and to determine the pharmacokinetic behaviors of the prepared nanocrystals. Methods Nanocrystals of SNX-2112 were prepared using the wet-media milling technique and characterized by particle size, differential scanning calorimetry, drug release, etc. Physiologically based pharmacokinetic (PBPK) modeling was undertaken to evaluate the drug’s disposition in rats following administration of drug cosolvent or nanocrystals. Results The optimized SNX-2112 nanocrystals (with poloxamer 188 as the stabilizer) were 203 nm in size with a zeta potential of −11.6 mV. In addition, the nanocrystals showed a comparable release profile to the control (drug cosolvent). Further, the rat PBPK model incorporating the parameters of particulate uptake (into the liver and spleen) and of in vivo drug release was well fitted to the experimental data following administration of the drug nanocrystals. The results reveal that the nanocrystals rapidly released drug molecules in vivo, accounting for their cosolvent-like pharmacokinetic behaviors. Due to particulate uptake, drug accumulation in the liver and spleen was significant at the initial time points (within 1 hour). Conclusion The nanocrystals should be a good choice for the systemic delivery of the poorly soluble drug SNX-2112. Also, our study contributes to an improved understanding of the in vivo fate of nanocrystals. PMID:25848269

  10. Photophysical properties of wavelength-tunable methylammonium lead halide perovskite nanocrystals

    DOE PAGES

    Freppon, Daniel J.; Men, Long; Burkhow, Sadie J.; ...

    2016-11-25

    Here we present the time-correlated luminescence of isolated nanocrystals of five methylammonium lead mixed-halide perovskite compositions (CH3NH3PbBr3$-$xIx) that were synthesized with varying iodide and bromide anion loading. All analyzed nanocrystals had a spherical morphology with diameters in the range of 2 to 32 nm. The luminescence maxima of CH3NH3PbBr3$-$xIx nanocrystals were tuned to wavelengths ranging between 498 and 740 nm by varying the halide loading. Both CH3NH3PbI3 and CH3NH3PbBr3 nanocrystals exhibited no luminescence intermittency for more than 90% of the 250 s analysis time, as defined by a luminescence intensity three standard deviations above the background. The mixed halide CH3NH3PbBr0.75I0.25,more » CH3NH3PbBr0.50I0.50, and CH3NH3PbBr0.25I0.75 nanocrystals exhibited luminescence intermittency in 18%, 4% and 26% of the nanocrystals, respectively. Irrespective of luminescence intermittency, luminescence intensities were classified for each nanocrystal as: (a) constant, (b) multimodal, (c) photobrightening, and (d) photobleaching. Finally, based on their photophysics, the CH3NH3PbBr3$-$xIx nanocrystals can be expected to be useful in a wide-range of applications where low and non-intermittent luminescence is desirable, for example as imaging probes and in films for energy conversion devices.« less

  11. Optically induced dynamic nuclear spin polarisation in diamond

    NASA Astrophysics Data System (ADS)

    Scheuer, Jochen; Schwartz, Ilai; Chen, Qiong; Schulze-Sünninghausen, David; Carl, Patrick; Höfer, Peter; Retzker, Alexander; Sumiya, Hitoshi; Isoya, Junichi; Luy, Burkhard; Plenio, Martin B.; Naydenov, Boris; Jelezko, Fedor

    2016-01-01

    The sensitivity of magnetic resonance imaging (MRI) depends strongly on nuclear spin polarisation and, motivated by this observation, dynamical nuclear spin polarisation has recently been applied to enhance MRI protocols (Kurhanewicz et al 2011 Neoplasia 13 81). Nuclear spins associated with the 13C carbon isotope (nuclear spin I = 1/2) in diamond possess uniquely long spin lattice relaxation times (Reynhardt and High 2011 Prog. Nucl. Magn. Reson. Spectrosc. 38 37). If they are present in diamond nanocrystals, especially when strongly polarised, they form a promising contrast agent for MRI. Current schemes for achieving nuclear polarisation, however, require cryogenic temperatures. Here we demonstrate an efficient scheme that realises optically induced 13C nuclear spin hyperpolarisation in diamond at room temperature and low ambient magnetic field. Optical pumping of a nitrogen-vacancy centre creates a continuously renewable electron spin polarisation which can be transferred to surrounding 13C nuclear spins. Importantly for future applications we also realise polarisation protocols that are robust against an unknown misalignment between magnetic field and crystal axis.

  12. Fabrication and Optical Properties of Water Soluble CdSeS Nanocrystals Using Glycerin as Stabilizing Agent

    PubMed Central

    Jiang, Fengrui; Tan, Guolong

    2013-01-01

    Herein we present an unusual phosphine-free method to fabricate water soluble CdSeS nanocrystals in cubic structure. In this method, glycerin was used as a stabilizing agent replacing tri-n-octylphosphine oxide (TOPO). Water solution of Na2SeO3 in polyethylene glycol was utilized as Se source. 3-Mercaptopropionic acid (MPA) provides S source. The phosphine-free Se and S sources were found to be highly reactive and suitable for the synthesis of CdSeS nanocrystals. XRD and HRTEM images confirm the formation of CdSeS nanocrystals in zinc blende structure. The absorption peaks on UV-vis spectra of as-prepared CdSeS nanocrystals are tunable from 330 nm to 440 nm, which blue shifts to shorter wavelength side in comparison with that of pure CdSe nanocrystals. The cubic CdSeS nanocrystals demonstrate narrow PL emissions spectra between 464 and 615 nm. Transmission electron microscopy images show the uniformity for the size distribution of the ternary QDs. Series water soluble CdSe1–xSx (x = 0∼1) nanocrystals have also been synthesized using Na2SeO3 and Na2S solution as the Se-S co-sources. Tunable band gap energies of CdSe1–xSx (x = 0∼1) nanocrystals upon chemical composition x have been achieved, the gap ranges from 290 nm to 558 nm. PMID:24204781

  13. Raman investigation of diamond films

    SciTech Connect

    Feng, Li-Ming

    1993-12-31

    Extensive Raman investigations were conducted on a wide range of diamond films whose structures were dilineated by optical and confocal microscopy. The Raman Spectra from one extreme of this range indicates a very intense 1331 cm{sup {minus}1} line diagnostic of bulk crystalline diamond. Microscopy of the corresponding film shows the presence of many large true diamond crystallite. The 1331 cm{sup {minus}1} Raman line at the other extreme of the range, however, is virtually absent. It is replaced, at this extreme, by a very broad Raman contour whose maxima occur near 1355 cm{sup {minus}1} and 1575 cm{sup {minus}1}. Optical microscopy now reveals a complete lack of diamond crystallites. The ratio of the integrated Raman intensity of the 1331 cm{sup {minus}1} diamond line to the integral of the entire broad contour extending from {approx}1200 cm{sup {minus}1} to 1800 cm{sup {minus}1}, with maxima near 1355 cm{sup {minus}1} and 1575 cm{sup {minus}1}, was determined. This ratio rises with increasing diamond crystallite size, and it decreases as true diamond crystallites are replaced by diamond-like, but amorphous, hard carbon, which produces the broad Raman contour. The measured intensity ratio was analyzed in terms of a differential equation related to phonon coupling. The increase of the intensity ratio of the 1331 cm{sup {minus}1} diagnostic diamond peak is due to phono-phonon coupling between the diamond crystallites, as the concentration of the amorphous diamond-like carbon decreases. Confocal microscopy indicates many amorphous-like regions interspersed between diamond crystallites which account for the intensity loss, and agree with the Raman intensity measurements. These Raman measurements crystallinity versus amorphous hard-carbon character of thin diamond film.

  14. Low Temperature Growth of Nanostructured Diamond Films on Metals

    NASA Technical Reports Server (NTRS)

    Baker, Paul A.; Catledge, Shane A.; Vohra, Yogesh K.

    2001-01-01

    The field of nanocrystalline diamond and tetrahedral amorphous carbon films has been the focus of intense experimental activity in the last few years for applications in field emission display devices, optical windows, and tribological coatings, The choice of substrate used in most studies has typically been silicon. For metals, however, the thermal expansion mismatch between the diamond film and substrate gives rise to thermal stress that often results in delamination of the film. To avoid this problem in conventional CVD deposition low substrate temperatures (less than 700 C) have been used, often with the incorporation of oxygen or carbon monoxide to the feedgas mixture. Conventionally grown CVD diamond films are also rough and would require post-deposition polishing for most applications. Therefore, there is an obvious need to develop techniques for deposition of well-adhered, smooth nano-structured diamond films on metals for various tribological applications. In our work, nanostructured diamond films are grown on a titanium alloy substrate using a two-step deposition process. The first step is performed at elevated temperature (820 C) for 30 minutes using a H2/CH4/N2 gas mixture in order to grow a thin (approx. 600 nm) nanostructured diamond layer and improve film adhesion. The remainder of the deposition involves growth at low temperature (less than 600 C) in a H2/CH4/O2 gas mixture. Laser reflectance Interferometry (LRI) pattern during growth of a nanostructured diamond film on Ti-6Al-4V alloy. The first 30 minutes are at a high temperature of 820 C and the rest of the film is grown at a low temperature of 580 T. The fringe pattern is observed till the very end due to extremely low surface roughness of 40 nm. The continuation of the smooth nanostructured diamond film growth during low temperature deposition is confirmed by in-situ laser reflectance interferometry and by post-deposition micro-Raman spectroscopy and surface profilometry. Similar experiments

  15. Friction and Wear Properties of As-deposited and Carbon Ion-implanted Diamond Films

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa

    1994-01-01

    Recent work on the friction and wear properties of as-deposited and carbon ion-implanted diamond films was reviewed. Diamond films were produced by the microwave plasma chemical vapor deposition (CVD) technique. Diamond films with various grain sizes and surface roughnesses were implanted with carbon ions at 60 ke V ion energy, resulting in a dose of 1.2310(exp 17) carbon ions/cm(exp 2). Various analytical techniques, including Raman spectroscopy, proton recoil analysis, Rutherford backscattering, transmission and scanning electron microscopy, x-ray photoelectron spectroscopy, and x-ray diffraction, were utilized to characterize the diamond films. Sliding friction experiments were conducted with a polished natural diamond pin in contact with diamond films in the three environments: humid air (40 percent relative humidity), dry nitrogen (less than 1 percent relative humidity), and ultrahigh vacuum (10(exp -7) Pa). The CVD diamond films indeed have friction and were properties similar to those of natural diamond in the three environments. The as-deposited, fine-grain diamond films can be effectively used as self-lubricating, wear-resistant coatings that have low coefficients of friction (0.02 to 0.04) and low wear rates (10(exp -7) to 10(exp -8)mm(exp 3)/N-m) in both humid air and dry nitrogen. However, they have high coefficients of friction (1.5 to 1.7) and a high wear rate (10(exp -4)mm(exp 3/N-m) in ultrahigh vacuum. The carbon ion implanation produced a thin surficial layer (less than 0.1 micron thick) of amorphous, nondiamond carbon on the diamond films. In humid air and dry nitrogen, the ion-implanted, fine- and coarse-grain diamond films have a low coefficient of friction (around 0.1) and a low wear rate (10(exp -7)mm(exp 3/N-m). Even in ultrahigh vacuum, the presence of the nondiamond carbon layer reduced the coefficient of friction of fine-grain diamond films to 0.1 or lower and the wear rate to 10(exp -6)mm(exp 3)/N-m. Thus, the carbon ion-implanted, fine

  16. Electrochemically grafted polypyrrole changes photoluminescence of electronic states inside nanocrystalline diamond

    SciTech Connect

    Galář, P. Malý, P.; Čermák, J.; Kromka, A.; Rezek, B.

    2014-12-14

    Hybrid diamond-organic interfaces are considered attractive for diverse applications ranging from electronics and energy conversion to medicine. Here we use time-resolved and time-integrated photoluminescence spectroscopy in visible spectral range (380–700 nm) to study electronic processes in H-terminated nanocrystalline diamond films (NCD) with 150 nm thin, electrochemically deposited polypyrrole (PPy) layer. We observe changes in dynamics of NCD photoluminescence as well as in its time-integrated spectra after polymer deposition. The effect is reversible. We propose a model where the PPy layer on the NCD surface promotes spatial separation of photo-generated charge carriers both in non-diamond carbon phase and in bulk diamond. By comparing different NCD thicknesses we show that the effect goes as much as 200 nm deep inside the NCD film.

  17. Semiconductor nanocrystal-based phagokinetic tracking

    SciTech Connect

    Alivisatos, A Paul; Larabell, Carolyn A; Parak, Wolfgang J; Le Gros, Mark; Boudreau, Rosanne

    2014-11-18

    Methods for determining metabolic properties of living cells through the uptake of semiconductor nanocrystals by cells. Generally the methods require a layer of neutral or hydrophilic semiconductor nanocrystals and a layer of cells seeded onto a culture surface and changes in the layer of semiconductor nanocrystals are detected. The observed changes made to the layer of semiconductor nanocrystals can be correlated to such metabolic properties as metastatic potential, cell motility or migration.

  18. Precipitation-lyophilization-homogenization (PLH) for preparation of clarithromycin nanocrystals: influencing factors on physicochemical properties and stability.

    PubMed

    Morakul, Boontida; Suksiriworapong, Jiraphong; Leanpolchareanchai, Jiraporn; Junyaprasert, Varaporn Buraphacheep

    2013-11-30

    Nanocrystals is one of effective technologies used to improve solubility and dissolution behavior of poorly soluble drugs. Clarithromycin is classified in BCS class II having low bioavailability due to very low dissolution behavior. The main purpose of this study was to investigate an efficiency of clarithromycin nanocrystals preparation by precipitation-lyophilization-homogenization (PLH) combination method in comparison with high pressure homogenization (HPH) method. The factors influencing particle size reduction and physical stability were assessed. The results showed that the PLH technique provided an effective and rapid reduction of particle size of nanocrystals to 460 ± 10 nm with homogeneity size distribution after only the fifth cycle of homogenization, whereas the same size was attained after 30 cycles by the HPH method. The smallest nanocrystals were achieved by using the combination of poloxamer 407 (2%, w/v) and SLS (0.1%, w/v) as stabilizers. This combination could prevent the particle aggregation over 3-month storage at 4 °C. The results from SEM showed that the clarithromycin nanocrystals were in cubic-shaped similar to its initial particle morphology. The DSC thermogram and X-ray diffraction pattern of nanocrystals were not different from the original drug except for intensity of peaks which indicated the presenting of nanocrystals in the crystalline state and/or partial amorphous form. In addition, the dissolution of the clarithromycin nanocrystals was dramatically increased as compared to the coarse clarithromycin.

  19. Charge separation in type II tunneling structures of close-packed CdTe and CdSe nanocrystals.

    PubMed

    Gross, Dieter; Susha, Andrei S; Klar, Thomas A; Da Como, Enrico; Rogach, Andrey L; Feldmann, Jochen

    2008-05-01

    We report on charge separation between type II aligned CdTe and CdSe nanocrystals. Two types of electrostatically bound nanocrystal structures have been studied: first, clusters of nanocrystals hold together by Ca(II) ions in aqueous solution and, second, thin film structures of nanocrystals created with layer-by-layer deposition in combination with polyelectrolytes. In both types of structures, short interparticle distances of less than 1 nm have been achieved, whereby the isolating organic ligands on the nanocrystal surfaces and/or the polymer monolayers act as tunneling barriers between nanocrystals. We have observed an efficient quenching of photoluminescence and a reduced emission lifetime for CdTe nanocrystals in both types of type II heterostructures. This result is explained by a spatial charge separation of the photoexcited electron-hole pairs due to tunneling of charge carriers through the thin organic layer between CdTe and CdSe nanocrystals. Type II heterostructures demonstrated here may find future applications in photovoltaics.

  20. Effects of disorder state and interfacial layer on thermal transport in copper/diamond system

    SciTech Connect

    Sinha, V.; Gengler, J. J.; Muratore, C.; Spowart, J. E.

    2015-02-21

    The characterization of Cu/diamond interface thermal conductance (h{sub c}) along with an improved understanding of factors affecting it are becoming increasingly important, as Cu-diamond composites are being considered for electronic packaging applications. In this study, ∼90 nm thick Cu layers were deposited on synthetic and natural single crystal diamond substrates. In several specimens, a Ti-interface layer of thickness ≤3.5 nm was sputtered between the diamond substrate and the Cu top layer. The h{sub c} across Cu/diamond interfaces for specimens with and without a Ti-interface layer was determined using time-domain thermoreflectance. The h{sub c} is ∼2× higher for similar interfacial layers on synthetic versus natural diamond substrate. The nitrogen concentration of synthetic diamond substrate is four orders of magnitude lower than natural diamond. The difference in nitrogen concentration can lead to variations in disorder state, with a higher nitrogen content resulting in a higher level of disorder. This difference in disorder state potentially can explain the variations in h{sub c}. Furthermore, h{sub c} was observed to increase with an increase of Ti-interface layer thickness. This was attributed to an increased adhesion of Cu top layer with increasing Ti-interface layer thickness, as observed qualitatively in the current study.

  1. Structure and properties of diamond and diamond-like films

    SciTech Connect

    Clausing, R.E.

    1993-01-01

    This section is broken into four parts: (1) introduction, (2) natural IIa diamond, (3) importance of structure and composition, and (4) control of structure and properties. Conclusions of this discussion are that properties of chemical vapor deposited diamond films can compare favorably with natural diamond, that properties are anisotropic and are a strong function of structure and crystal perfection, that crystal perfection and morphology are functions of growth conditions and can be controlled, and that the manipulation of texture and thereby surface morphology and internal crystal perfection is an important step in optimizing chemically deposited diamond films for applications.

  2. Synthesis, characterization, shape evolution, and optical properties of copper sulfide hexagonal bifrustum nanocrystals

    NASA Astrophysics Data System (ADS)

    Jia, Baorui; Qin, Mingli; Jiang, Xuezhi; Zhang, Zili; Zhang, Lin; Liu, Ye; Qu, Xuanhui

    2013-03-01

    The hexagonal bifrustum-shaped copper sulfide (CuS) nanocrystals were selectively and facilely synthesized by a hydrothermal method for the first time at 120 °C. The products were characterized by X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, ultraviolet-visible (UV-Vis) spectroscopy, and photoluminescence spectroscopy. The results showed that the CuS hexagonal bifrustum nanocrystal was bounded by two top hexagons with edge length of about 50-70 nm and twelve lateral trapezoids with a base of about 100 nm and that the length of each hexagonal bifrustum was about 250 nm. Tetradecylamine (TDA), as an effective capping agent, was found to be critical for this special shape. Using different amounts of TDA, two kinds of CuS hexagonal bifrustum nanocrystals were obtained: "lender hexagonal bifrustum" and "pancake hexagonal bifrustum." Furthermore, we studied the formation mechanism of hexagonal bifrustum, which is related to the intrinsic crystalline structure of CuS and Ostwald ripening. And, the results revealed that the CuS nanocrystal evolved from hexagonal plate to hexagonal bifrustum and finally to hexagonal bipyramid as the heating time increased. The UV-Vis absorption spectrum showed that these CuS hexagonal bifrustum nanocrystals exhibited strong absorption in the near-infrared region and had a potential application for photothermal therapy and photocatalysis.

  3. Two-silicon-nanocrystal layer memory structure with improved retention characteristics.

    PubMed

    Nassiopoulou, A G; Salonidou, A

    2007-01-01

    It was demonstrated in the literature that the use of self-aligned doubly-stacked Si dots improves retention characteristics of a nanocrystal memory. In this paper, we show that a similar effect may be obtained by using two distinct layers of silicon nanocrystals within the gate dielectric of the MOS structure, if the nanocrystal density in each layer is high enough (above 10(12) dots/cm2) so as to get an average effect of at least one smaller dot underneath each larger one. The relative distance of the layers and their position from the silicon substrate and the gate metal are critical for optimum memory operation. Two different double-nanocrystal-layer structures were investigated. In the first structure the two nanocrystal layers were close together and they were composed of dots of different size (lower layer: 3 nm, upper layer: 5 nm), while in the second structure the dot layers were composed of dots of equal diameter (d = 3 nm) and their inter-distance was much larger. In both cases, the retention characteristics of the structure were improved compared with a single dot layer structure. In the second case this improvement was significantly larger than in the first case. Extrapolation of the data to ten years memory operation, showed that the charge loss after this time was only approximately 12%.

  4. CVD Diamond Films for Tribological Applications

    DTIC Science & Technology

    1990-03-31

    diamond film) tests. In the following discussion, coefficient of friction is abbreviated as g ; subscripts i, f, and min refer to initial, final, and...100)/(110) films exhibit significantly lower g ±i than do (111) films. The importance of film morphology in determining gi is most strongly...00.6 0 0 00 mn 0 -0.5 008 0 0 0 *c 0.4 00 80 o 0.3 G 0.2 0 0.1 X X 0 IN m 10.0 100.0 1000.0 Initial Surface Roughness (nm) Figure 16a: Coefficient of

  5. Cytotoxicity and cellular uptake of ZnS:Mn nanocrystals biofunctionalized with chitosan and aminoacids

    NASA Astrophysics Data System (ADS)

    Sajimol Augustine, M.; Anas, Abdulaziz; Das, Ani V.; Sreekanth, S.; Jayalekshmi, S.

    2015-02-01

    Highly luminescent, manganese doped, zinc sulphide (ZnS:Mn) nanocrystals biofunctionalized with chitosan and various aminoacids such as L-citrulline, L-lysine, L-arginine, L-serine, L-histidine and glycine were synthesized by chemical capping co-precipitation method at room temperature, which is a simple and cost effective technique. The synthesized nanocrystals were structurally characterized by TEM, XRD, EDXS and FT-IR spectroscopy techniques. They possess high colloidal stability with strong orange red photoluminescence emission at 598 nm. The intensity of orange red emission has been observed to be maximum in L-citrulline capped ZnS:Mn nanocrystals in which the emission at 420 nm is effectively quenched by surface passivation due to capping. Taking into consideration the prospects of these highly luminescent, bio-compatible ZnS:Mn nanocrystals in bio-imaging applications, cytotoxicity studies were conducted to identify the capping combination which would accomplish minimum toxic effects. ZnS:Mn nanocrystals biofunctionalized with chitosan, L-citrulline, glycine, L-artginine, L-serine and L-histidine showed least toxicity up to 10 nM concentrations in mouse fibroblast L929 cells, which further confirms their cytocompatibility. Also the ZnS:Mn nanocrystals biofunctionalized with L-arginine showed maximum uptake in in vitro studies carried out in human embryonic kidney cells, HEK-293T, which shows the significant role of this particular amino acid in fetoplacental nutrition. The present study highlights the suitability of aminoacid conjugated ZnS:Mn nanocrystals, as promising candidates for biomedical applications.

  6. Highly crosslinked poly(dimethylsiloxane) microbeads with uniformly dispersed quantum dot nanocrystals.

    PubMed

    Shojaei-Zadeh, Shahab; Morris, Jeffrey F; Couzis, Alex; Maldarelli, Charles

    2011-11-01

    This study demonstrates how luminescent semiconductor nanocrystals (quantum dots or QDs) can be dispersed uniformly in a poly(dimethylsiloxane) (PDMS) matrix by polymerizing a mixture of the prepolymer oligomers and the nanocrystals with a relatively large concentration of crosslinking molecules. A microfluidic device is used to fabricate PDMS microbeads embedded with the QDs by using flow focusing to first form monodisperse droplets of the prepolymer/crosslinker/nanocrystal mixture in a continuous aqueous phase. The droplets are subsequently collected, and heated to polymerize them into solid microbead composites. The degree of aggregation of the nanocrystals in the matrix is studied by measuring the nonradiative resonance energy transfer (RET) between the nanocrystals. For this purpose, two quantum dots are used with maxima in their luminescence emission spectrum at 560 nm and 620 nm. When the nanocrystals are within the Förster radius (approximately 10 nm) of each other, exciton energy cascades from the QDs which emit at the shorter wavelength to the QDs which emit at the longer wavelength. This energy transfer is quantified, for two concentration ratios of the prepolmer to the crosslinker, by measuring the deviation of the microbead luminescence spectrum from a reference spectrum obtained by dispersing the QD mixture in a solvent (toluene) in which the nanocrystals do not aggregate. For a low concentration of crosslinking molecules relative to the prepolymer (5:1 by weight prepolymer to crosslinker), strong RET is observed as the emission of the 620 nm QDs is increased and the 560 nm QDs is decreased relative to the reference. In the emission spectrum for a higher concentration of crosslinkers (2:1 by weight prepolymer to crosslinker), the resonance energy transfer is less relative to the case of the low concentration of crosslinkers, and the spectrum more closely resembles the reference. This result indicates that the increase in the crosslinker concentration

  7. Differing morphologies of textured diamond films with electrical properties made with microwave plasma chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Lai, Wen Chi; Wu, Yu-Shiang; Chang, Hou-Cheng; Lee, Yuan-Haun

    2010-12-01

    This study investigates the orientation of textured diamond films produced through microwave plasma chemical vapor deposition (MPCVD) at 1200 W, 110 Torr, CH 4/H 2 = 1/20, with depositions times of 0.5-4.0 h. After a growth period of 2.0-4.0 h, this particular morphology revealed a rectangular structure stacked regularly on the diamond film. The orientation on {1 1 1}-textured diamond films grew a preferred orientation of {1 1 0} on the surface, as measured by XRD. The formation of the diamond epitaxial film formed textured octahedrons in ball shaped (or cauliflower-like) diamonds in the early stages (0.5 h), and the surface of the diamond film extended to pile the rectangular structure at 4.0 h. The width of the tier was approximately 200 nm at the 3.0 h point of deposition, according to TEM images. The results revealed that the textured diamond films showed two different morphological structures (typical ball shaped and rectangular diamonds), at different stages of the deposition period. The I- V characteristics of the oriented diamond films after 4.0 h of deposition time showed good conformity with the ohmic contact.

  8. Heavy-Ion Radiation-Induced Diamond Formation in Carbonaceous Materials

    NASA Astrophysics Data System (ADS)

    Daulton, T. L.; Ozima, M.

    1996-10-01

    The feasibility of a radiation-induced diamond formation (RIDF) mechanism is demonstrated by the observation of nano-diamonds in carburanium, a U-rich fine-grained, coal-like assemblage containing amorphous carbonaceous material of Precambrian age from North Karelia, Russia. This mineral deposit represents an ideal natural environment for RIDF because the carbonaceous grains present have received a high fluence of energetic particles over a geological time scale. Fragments of carburanium were subjected to acid dissolution treatments to isolate any diamond present. Transmission electron microscopy on these acid residues identified 500 nm polycrystalline diamond aggregates. This observation and estimates of formation efficiencies supports the hypothesis that diamond can form in carbonaceous material irradiated by U decay fragments. Diamond concentration in bulk carburanium is #197# 30 ppm indicating that the RIDF efficiencies might be relatively low as compared to the competing formation of graphite; the acid treatment was an essential key in the recovery of diamond in carburanium. This fact could contribute to the lack of observation of diamond in well- studied ion-implanted carbons. Experiments to synthesize nano-diamonds by heavy-ion irradiation are scheduled for late 1996 at ANL's accelerator ATLAS.

  9. Application of precision diamond machining to the manufacture of microphotonics components

    NASA Astrophysics Data System (ADS)

    Davies, Matthew A.; Evans, Christopher J.; Vohra, Rashmi R.; Bergner, Brent C.; Patterson, Steven R.

    2003-11-01

    The use of diamonds to generate precision patterns and precision surfaces on a micrometer or nanometer scale has a history that dates back centuries. Uses of diamond in semi-automated machinery can be traced to ruling machines, pantographs, and ornamental turning with "diamond turning" dating back about a century. Poor behavior in machining more common materials (e.g. ferrous alloys) has limited diamond use in traditional industrial machining. The niche of the single crystal diamond is its edge sharpness and the ability to produce near-optical finish in materials such as aluminum, copper and their alloys; however, due to machine limitations, diamond machining remained a novelty until relatively recently. A convergence of machine technologies developed for both weapons and commercial applications led to modern diamond turning. Current turnkey machines can produce contoured surfaces with surface finish in the range of 5 nm Ra and long range accuracy of micrometers or less. Macroscopic scale, three axis, diamond machining is a well-developed technology; machining of features on a micrometer and submicrometer scale is a new and rapidly developing application of single crystal diamond machining. The role of this technology in micro-optics replication has yet to be fully defined.

  10. Aqueous based synthesis of N-acetyl-L-cysteine capped ZnSe nanocrystals with intense blue emission

    NASA Astrophysics Data System (ADS)

    Soheyli, Ehsan; Sahraei, Reza; Nabiyouni, Gholamreza

    2016-10-01

    In this work a very simple reflux route for preparation of ZnSe nanocrystals with minor modification and faster preparation over conventional ones is introduced. X-ray diffraction analysis indicated that the ZnSe nanocrystals have a cubic structure. The complete disappearance of the S-H band in FT-IR spectrum of N-acetyl-L-cysteine capped ZnSe nanocrystals was an indication over formation of Zn-thiol covalent bonds at the surface of the nanocrystals which results in passivation of small nanocrystals. The strong size-quantization regime was responsible of significant blue shift in absorption/emission spectra. Using the well-known calculations, band gap and Urbach energy of the ZnSe nanocrystals were measured and their average size was estimated optically to be around 4.6 nm along with the TEM image. A dark blue emission with higher relative intensity of excitonic to trap emissions (compared to conventional method), very narrow excitonic emission peak of about 16 nm and remarkable stability was obtained from the ZnSe nanocrystals.

  11. Genetics Home Reference: Diamond-Blackfan anemia

    MedlinePlus

    ... Understand Genetics Home Health Conditions Diamond-Blackfan anemia Diamond-Blackfan anemia Enable Javascript to view the expand/ ... boxes. Download PDF Open All Close All Description Diamond-Blackfan anemia is a disorder of the bone ...

  12. Genetics Home Reference: Shwachman-Diamond syndrome

    MedlinePlus

    ... Genetics Home Health Conditions Shwachman-Diamond syndrome Shwachman-Diamond syndrome Enable Javascript to view the expand/collapse ... Download PDF Open All Close All Description Shwachman-Diamond syndrome is an inherited condition that affects many ...

  13. Smooth diamond films as low friction, long wear surfaces

    DOEpatents

    Gruen, Dieter M.; Krauss, Alan R.; Erdemir, Ali; Bindal, Cuma; Zuiker, Christopher D.

    1999-01-01

    An article and method of manufacture of a nanocrystalline diamond film. The nanocrystalline film is prepared by forming a carbonaceous vapor, providing an inert gas containing gas stream and combining the gas stream with the carbonaceous containing vapor. A plasma of the combined vapor and gas stream is formed in a chamber and fragmented carbon species are deposited onto a substrate to form the nanocrystalline diamond film having a root mean square flatness of about 50 nm deviation from flatness in the as deposited state.

  14. Transforming graphite to nanoscale diamonds by a femtosecond laser pulse

    SciTech Connect

    Nueske, R.; Jurgilaitis, A.; Enquist, H.; Harb, M.; Larsson, J.; Fang, Y.; Haakanson, U.

    2012-01-23

    Formation of cubic diamond from graphite following irradiation by a single, intense, ultra-short laser pulse has been observed. Highly oriented pyrolytic graphite (HOPG) samples were irradiated by a 100 fs pulse with a center wavelength of 800 nm. Following laser exposure, the HOPG samples were studied using Raman spectroscopy of the sample surface. In the laser-irradiated areas, nanoscale cubic diamond crystals have been formed. The exposed areas were also studied using grazing incidence x-ray powder diffraction showing a restacking of planes from hexagonal graphite to rhombohedral graphite.

  15. Diamond films for laser hardening

    NASA Technical Reports Server (NTRS)

    Albin, S.; Watkins, L.; Ravi, K.; Yokota, S.

    1989-01-01

    Laser-damage experiments were performed on free-standing polycrystalline diamond films prepared by plasma-enhanced CVD. The high laser-induced stress resistance found for this material makes it useful for thin-film coatings for laser optics. Results for diamond-coated silicon substrates demonstrate the enhanced damage threshold imparted by diamond thin-film coatings to materials susceptible to laser damage.

  16. Conversion of fullerenes to diamond

    DOEpatents

    Gruen, Dieter M.

    1994-01-01

    A method of forming synthetic diamond on a substrate. The method involves providing a substrate surface covered with a fullerene or diamond coating, positioning a fullerene in an ionization source, creating a fullerene vapor, ionizing fullerene molecules, accelerating the fullerene ions to energies above 250 eV to form a fullerene ion beam, impinging the fullerene ion beam on the substrate surface and continuing these steps to obtain a diamond film thickness on the substrate.

  17. Conversion of fullerenes to diamond

    DOEpatents

    Gruen, Dieter M.

    1993-01-01

    A method of forming synthetic diamond on a substrate is disclosed. The method involves providing a substrate surface covered with a fullerene or diamond coating, positioning a fullerene in an ionization source, creating a fullerene vapor, ionizing fullerene molecules, accelerating the fullerene ions to energies above 250 eV to form a fullerene ion beam, impinging the fullerene ion beam on the substrate surface and continuing these steps to obtain a diamond thickness on the substrate.

  18. Quantum Confinement Regimes in CdTe Nanocrystals Probed by Single Dot Spectroscopy: From Strong Confinement to the Bulk Limit.

    PubMed

    Tilchin, Jenya; Rabouw, Freddy T; Isarov, Maya; Vaxenburg, Roman; Van Dijk-Moes, Relinde J A; Lifshitz, Efrat; Vanmaekelbergh, Daniel

    2015-08-25

    Sufficiently large semiconductor nanocrystals are a useful model system to characterize bulk-like excitons, with the electron and hole bound predominantly by Coulomb interaction. We present optical characterization of excitons in individual giant CdTe nanocrystals with diameters up to 25.5 nm at 4.2 K under varying excitation power and magnetic field strength. We determine values for the biexciton binding energy, diamagnetic shift constant, and Landé g-factor, which approach the bulk values with increasing nanocrystal size.

  19. DIAMOND SECONDARY EMITTER

    SciTech Connect

    BEN-ZVI, I.; RAO, T.; BURRILL, A.; CHANG, X.; GRIMES, J.; RANK, J.; SEGALOV, Z.; SMEDLEY, J.

    2005-10-09

    We present the design and experimental progress on the diamond secondary emitter as an electron source for high average power injectors. The design criteria for average currents up to 1 A and charge up to 20 nC are established. Secondary Electron Yield (SEY) exceeding 200 in transmission mode and 50 in emission mode have been measured. Preliminary results on the design and fabrication of the self contained capsule with primary electron source and secondary electron emitter will also be presented.

  20. Diamond Technology Study.

    DTIC Science & Technology

    1979-06-11

    has been conducted into the use of diamond as a TWT helix support material to increase the average output power capability of broadband high frequency...unifilar helix is the one TWT circuit capable of broadband operation with good efficiency, methods to increase jT its power dissipation capability are of...BIBLIOGRAPHY IRa D> AE .,L,-,# ACot .,i n iv 4 I IPT-5413 LIST OF ILLUSTRATIONS Figure No. Title 1 Temperature Differences in a PPM Focused Helix TWT

  1. Diamond turning of glass

    SciTech Connect

    Blackley, W.S.; Scattergood, R.O.

    1988-12-01

    A new research initiative will be undertaken to investigate the critical cutting depth concepts for single point diamond turning of brittle, amorphous materials. Inorganic glasses and a brittle, thermoset polymer (organic glass) are the principal candidate materials. Interrupted cutting tests similar to those done in earlier research are Ge and Si crystals will be made to obtain critical depth values as a function of machining parameters. The results will provide systematic data with which to assess machining performance on glasses and amorphous materials

  2. Nitrogen and silicon defect incorporation during homoepitaxial CVD diamond growth on (111) surfaces

    SciTech Connect

    Moore, Samuel L.; Vohra, Yogesh K.

    2015-01-01

    Chemical Vapor Deposited (CVD) diamond growth on (111)-diamond surfaces has received increased attention lately because of the use of N-V related centers in quantum computing as well as application of these defect centers in sensing nano-Tesla strength magnetic fields. We have carried out a detailed study of homoepitaxial diamond deposition on (111)-single crystal diamond (SCD) surfaces using a 1.2 kW microwave plasma CVD (MPCVD) system employing methane/hydrogen/nitrogen/oxygen gas phase chemistry. We have utilized Type Ib (111)-oriented single crystal diamonds as seed crystals in our study. The homoepitaxially grown diamond films were analyzed by Raman spectroscopy, Photoluminescence Spectroscopy (PL), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The nitrogen concentration in the plasma was carefully varied between 0 and 1500 ppm while a ppm level of silicon impurity is present in the plasma from the quartz bell jar. The concentration of N-V defect centers with PL zero phonon lines (ZPL) at 575nm and 637nm and the Si-defect center with a ZPL at 737nm were experimentally detected from a variation in CVD growth conditions and were quantitatively studied. As a result, altering nitrogen and oxygen concentration in the plasma was observed to directly affect N-V and Si-defect incorporation into the (111)-oriented diamond lattice and these findings are presented.

  3. Nitrogen and silicon defect incorporation during homoepitaxial CVD diamond growth on (111) surfaces

    DOE PAGES

    Moore, Samuel L.; Vohra, Yogesh K.

    2015-01-01

    Chemical Vapor Deposited (CVD) diamond growth on (111)-diamond surfaces has received increased attention lately because of the use of N-V related centers in quantum computing as well as application of these defect centers in sensing nano-Tesla strength magnetic fields. We have carried out a detailed study of homoepitaxial diamond deposition on (111)-single crystal diamond (SCD) surfaces using a 1.2 kW microwave plasma CVD (MPCVD) system employing methane/hydrogen/nitrogen/oxygen gas phase chemistry. We have utilized Type Ib (111)-oriented single crystal diamonds as seed crystals in our study. The homoepitaxially grown diamond films were analyzed by Raman spectroscopy, Photoluminescence Spectroscopy (PL), X-ray Photoelectronmore » Spectroscopy (XPS), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The nitrogen concentration in the plasma was carefully varied between 0 and 1500 ppm while a ppm level of silicon impurity is present in the plasma from the quartz bell jar. The concentration of N-V defect centers with PL zero phonon lines (ZPL) at 575nm and 637nm and the Si-defect center with a ZPL at 737nm were experimentally detected from a variation in CVD growth conditions and were quantitatively studied. As a result, altering nitrogen and oxygen concentration in the plasma was observed to directly affect N-V and Si-defect incorporation into the (111)-oriented diamond lattice and these findings are presented.« less

  4. Single-Crystal Diamond Nanowire Tips for Ultrasensitive Force Microscopy.

    PubMed

    Tao, Y; Degen, C L

    2015-12-09

    We report the fabrication, integration, and assessment of sharp diamond tips for ultrasensitive force microscopy experiments. Two types of tips, corresponding to the upper and lower halves of a diamond nanowire, were fabricated by top-down plasma etching from a single-crystalline substrate. The lower, surface-attached halves can be directly integrated into lithographically defined nanostructures, like cantilevers. The upper, detachable halves result in diamond nanowires with a tunable diameter (50-500 nm) and lengths of a few microns. Tip radii were around 10 nm and tip apex angles around 15°. We demonstrate the integration of diamond nanowires for use as scanning tips onto ultrasensitive pendulum-style silicon cantilevers. We find the noncontact friction and frequency jitter to be exceptionally low, with no degradation in the intrinsic mechanical quality factor (Q ≈ 130,000) down to tip-to-surface distances of about 10 nm. Our results are an encouraging step toward further improvement of the sensitivity and resolution of force-detected magnetic resonance imaging.

  5. DIAMOND AMPLIFIER FOR PHOTOCATHODES.

    SciTech Connect

    RAO,T.; BEN-ZVI,I.; BURRILL,A.; CHANG,X.; HULBERT,S.; JOHNSON,P.D.; KEWISCH,J.

    2004-06-21

    We report a new approach to the generation of high-current, high-brightness electron beams. Primary electrons are produced by a photocathode (or other means) and are accelerated to a few thousand electron-volts, then strike a specially prepared diamond window. The large Secondary Electron Yield (SEY) provides a multiplication of the number of electrons by about two orders of magnitude. The secondary electrons drift through the diamond under an electric field and emerge into the accelerating proper of the ''gun'' through a Negative Electron Affinity surface of the diamond. The advantages of the new approach include the following: (1) Reduction of the number of primary electrons by the large SEY, i.e. a very low laser power in a photocathode producing the primaries. (2) Low thermal emittance due to the NEA surface and the rapid thermalization of the electrons. (3) Protection of the cathode from possible contamination from the gun, allowing the use of large quantum efficiency but sensitive cathodes. (4) Protection of the gun from possible contamination by the cathode, allowing the use of superconducting gun cavities. (5) Production of high average currents, up to ampere class. (6) Encapsulated design, making the ''load-lock'' systems unnecessary. This paper presents the criteria that need to be taken into account in designing the amplifier.

  6. Linearly arranged polytypic CZTSSe nanocrystals

    PubMed Central

    Fan, Feng-Jia; Wu, Liang; Gong, Ming; Chen, Shi You; Liu, Guang Yao; Yao, Hong-Bin; Liang, Hai-Wei; Wang, Yi-Xiu; Yu, Shu-Hong

    2012-01-01

    Even colloidal polytypic nanostructures show promising future in band-gap tuning and alignment, researches on them have been much less reported than the standard nano-heterostructures because of the difficulties involved in synthesis. Up to now, controlled synthesis of colloidal polytypic nanocrsytals has been only realized in II-VI tetrapod and octopod nanocrystals with branched configurations. Herein, we report a colloidal approach for synthesizing non-branched but linearly arranged polytypic I2-II-IV-VI4 nanocrystals, with a focus on polytypic non-stoichiometric Cu2ZnSnSxSe4−x nanocrystals. Each synthesized polytypic non-stoichiometric Cu2ZnSnSxSe4−x nanocrystal is consisted of two zinc blende-derived ends and one wurtzite-derived center part. The formation mechanism has been studied and the phase composition can be tuned through adjusting the reaction temperature, which brings a new band-gap tuning approach to Cu2ZnSnSxSe4-x nanocrystals. PMID:23233871

  7. Conversion of fullerenes to diamonds

    DOEpatents

    Gruen, Dieter M.

    1995-01-01

    A method of forming synthetic diamond or diamond-like films on a substrate surface. The method involves the steps of providing a vapor selected from the group of fullerene molecules or an inert gas/fullerene molecule mixture, providing energy to the fullerene molecules consisting of carbon-carbon bonds, the energized fullerene molecules breaking down to form fragments of fullerene molecules including C.sub.2 molecules and depositing the energized fullerene molecules with C.sub.2 fragments onto the substrate with farther fragmentation occurring and forming a thickness of diamond or diamond-like films on the substrate surface.

  8. Diamonds in ophiolites: Contamination or a new diamond growth environment?

    NASA Astrophysics Data System (ADS)

    Howell, D.; Griffin, W. L.; Yang, J.; Gain, S.; Stern, R. A.; Huang, J.-X.; Jacob, D. E.; Xu, X.; Stokes, A. J.; O'Reilly, S. Y.; Pearson, N. J.

    2015-11-01

    For more than 20 years, the reported occurrence of diamonds in the chromites and peridotites of the Luobusa massif in Tibet (a complex described as an ophiolite) has been widely ignored by the diamond research community. This skepticism has persisted because the diamonds are similar in many respects to high-pressure high-temperature (HPHT) synthetic/industrial diamonds (grown from metal solvents), and the finding previously has not been independently replicated. We present a detailed examination of the Luobusa diamonds (recovered from both peridotites and chromitites), including morphology, size, color, impurity characteristics (by infrared spectroscopy), internal growth structures, trace-element patterns, and C and N isotopes. A detailed comparison with synthetic industrial diamonds shows many similarities. Cubo-octahedral morphology, yellow color due to unaggregated nitrogen (C centres only, Type Ib), metal-alloy inclusions and highly negative δ13C values are present in both sets of diamonds. The Tibetan diamonds (n = 3) show an exceptionally large range in δ15N (-5.6 to + 28.7 ‰) within individual crystals, and inconsistent fractionation between {111} and {100} growth sectors. This in contrast to large synthetic HPHT diamonds grown by the temperature gradient method, which have with δ15N = 0 ‰ in {111} sectors and + 30 ‰ in {100} sectors, as reported in the literature. This comparison is limited by the small sample set combined with the fact the diamonds probably grew by different processes. However, the Tibetan diamonds do have generally higher concentrations and different ratios of trace elements; most inclusions are a NiMnCo alloy, but there are also some small REE-rich phases never seen in HPHT synthetics. These characteristics indicate that the Tibetan diamonds grew in contact with a C-saturated Ni-Mn-Co-rich melt in a highly reduced environment. The stable isotopes indicate a major subduction-related contribution to the chemical environment. The

  9. Near-infrared luminescent cubic silicon carbide nanocrystals for in vivo biomarker applications: an ab initio study.

    PubMed

    Somogyi, Bálint; Zólyomi, Viktor; Gali, Adam

    2012-12-21

    Molecule-sized fluorescent emitters are much sought-after to probe biomolecules in living cells. We demonstrate here by time-dependent density functional calculations that the experimentally achievable 1-2 nm sized silicon carbide nanocrystals can emit light in the near-infrared region after introducing appropriate color centers in them. These near-infrared luminescent silicon carbide nanocrystals may act as ideal fluorophores for in vivo bioimaging.

  10. Tailoring Plasmonic Enhanced Upconversion in Single NaYF4:Yb3+/Er3+ Nanocrystals

    PubMed Central

    Wang, Ya-Lan; Mohammadi Estakhri, Nasim; Johnson, Amber; Li, Hai-Yang; Xu, Li-Xiang; Zhang, Zhenyu; Alù, Andrea; Wang, Qu-Quan; Shih, Chih-Kang (Ken)

    2015-01-01

    By using silver nanoplatelets with a widely tunable localized surface plasmon resonance (LSPR), and their corresponding local field enhancement, here we show large manipulation of plasmonic enhanced upconversion in NaYF4:Yb3+/Er3+ nanocrystals at the single particle level. In particular, we show that when the plasmonic resonance of silver nanolplatelets is tuned to 656 nm, matching the emission wavelength, an upconversion enhancement factor ~5 is obtained. However, when the plasmonic resonance is tuned to 980 nm, matching the nanocrystal absorption wavelength, we achieve an enhancement factor of ~22 folds. The precise geometric arrangement between fluorescent nanoparticles and silver nanoplatelets allows us to make, for the first time, a comparative analysis between experimental results and numerical simulations, yielding a quantitative agreement at the single particle level. Such a comparison lays the foundations for a rational design of hybrid metal-fluorescent nanocrystals to harness the upconversion enhancement for biosensing and light harvesting applications. PMID:25976870

  11. Self-Assembly and Thermal Stability of Binary Superlattices of Gold and Silicon Nanocrystals

    PubMed Central

    Yu, Yixuan; Bosoy, Christian A.; Smilgies, Detlef-M.; Korgel, Brian A.

    2013-01-01

    Simple hexagonal (sh) AB2 binary superlattices (BSLs) of organic ligand-capped silicon (A; 5.40(±9.8%) nm diameter) and gold (B; 1.88(±10.1%) nm diameter) nanocrystals were assembled by evaporation of colloidal dispersions and characterized using transmission electron microscopy (TEM) and grazing incidence small-angle X-ray scattering (GISAXS). When deposited on tilted substrates by slow evaporation, the sh-AB2 superlattice contracts slightly towards the substrate with centered orthorhombic structure. Heating the BSL to 200°C in air led to gold coalescence and segregation to the surface of the assembly without disrupting the Si nanocrystal sublattice, thus creating a simple hexagonal superlattice of Si nanocrystals. PMID:24327828

  12. Nanocrystal powered nanomotor

    DOEpatents

    Regan, Brian C.; Zettl, Alexander K.; Aloni, Shaul

    2011-01-04

    A nanoscale nanocrystal which may be used as a reciprocating motor is provided, comprising a substrate having an energy differential across it, e.g. an electrical connection to a voltage source at a proximal end; an atom reservoir on the substrate distal to the electrical connection; a nanoparticle ram on the substrate distal to the atom reservoir; a nanolever contacting the nanoparticle ram and having an electrical connection to a voltage source, whereby a voltage applied between the electrical connections on the substrate and the nanolever causes movement of atoms between the reservoir and the ram. Movement of the ram causes movement of the nanolever relative to the substrate. The substrate and nanolever preferably comprise multiwalled carbon nanotubes (MWNTs) and the atom reservoir and nanoparticle ram are preferably metal (e.g. indium) deposited as small particles on the MWNTs. The substrate may comprise a silicon chip that has been fabricated to provide the necessary electrodes and other electromechanical structures, and further supports an atomic track, which may comprise an MWNT.

  13. Dispersing upconversion nanocrystals in a single silicon microtube

    PubMed Central

    Li, Hanyang; Wang, Yan; Li, Hui; Zhang, Yundong; Yang, Jun

    2016-01-01

    Nanocrystals of Ln3+ (Ln = Yb, Tm and Ho) doped β-NaLuF4 with average diameter about 200 nm are dispersed in silica-based microtube (MT) by a simple flame heating method. The fabricated microtube has a diameter range from 2 μm to 30 μm and lengths up to hundreds microns. The fluorescence of upconversion nanocrystals (UCNCs) can propagate along a single MT and couple into another MT through evanescent field. The guiding performance of the single UCNCs doped MT is measured to prove that it can be used as an active waveguide. Moreover, optical temperature sensing based on the single UCNCs-MT is also demonstrated, and the sensitivity of UCNCs-MT is significantly enough for thermometry applications in the range of 298–383 K. PMID:27779210

  14. Hybrid solar cells from P3HT and silicon nanocrystals.

    PubMed

    Liu, Chin-Yi; Holman, Zachary C; Kortshagen, Uwe R

    2009-01-01

    We are reporting new hybrid solar cells based on blends of silicon nanocrystals (Si NCs) and poly-3(hexylthiophene) (P3HT) polymer in which a percolating network of the nanocrystals acts as the electron-conducting phase. The properties of composite Si NCs/P3HT devices made by spin-coating Si NCs and P3HT from a common solvent were studied as a function of Si NC size and Si NC/P3HT ratio. The open-circuit voltage and short-circuit current are observed to depend on the Si NC size due to changes in the bandgap and surface-area-to-volume ratio. Under simulated one-sun A.M. 1.5 direct illumination (100 mW/cm2), devices made with 35 wt % Si NCs 3-5 nm in size showed 1.15% power conversion efficiency.

  15. Nanocrystals for luminescent solar concentrators.

    PubMed

    Bradshaw, Liam R; Knowles, Kathryn E; McDowall, Stephen; Gamelin, Daniel R

    2015-02-11

    Luminescent solar concentrators (LSCs) harvest sunlight over large areas and concentrate this energy onto photovoltaics or for other uses by transporting photons through macroscopic waveguides. Although attractive for lowering solar energy costs, LSCs remain severely limited by luminophore reabsorption losses. Here, we report a quantitative comparison of four types of nanocrystal (NC) phosphors recently proposed to minimize reabsorption in large-scale LSCs: two nanocrystal heterostructures and two doped nanocrystals. Experimental and numerical analyses both show that even the small core absorption of the leading NC heterostructures causes major reabsorption losses at relatively short transport lengths. Doped NCs outperform the heterostructures substantially in this critical property. A new LSC phosphor is introduced, nanocrystalline Cd(1-x)Cu(x)Se, that outperforms all other leading NCs by a significant margin in both small- and large-scale LSCs under full-spectrum conditions.

  16. Structure and infrared photoluminescence of GeSi nanocrystals formed by high temperature annealing of GeOx/SiO2 multilayers

    NASA Astrophysics Data System (ADS)

    Volodin, V. A.; Gambaryan, M. P.; Cherkov, A. G.; Stoffel, M.; Rinnert, H.; Vergnat, M.

    2016-08-01

    Germanium and GeSi nanocrystals were synthesized in SiGeO2 glass by high temperature annealings of GeOx(5 nm)/SiO2(5 nm) multilayers. According to electron microscopy data, the size distribution and stoichiometry of the nanocrystals depend on the annealing temperature (700, 800, or 900 °C). Spatial redistribution of Ge with the formation of large faceted nanocrystals located near the Si substrate and GeSi intermixing at the substrate/film interface were observed. In the case of the 900 °C annealed sample, we note that some nanocrystals have a pyramid-like shape. Infrared absorption spectroscopy demonstrates that intermixing takes place between the GeOx and SiO2 layers leading to the formation of SiGeO2 glass. Raman spectroscopy confirms the formation of Ge nanocrystals after annealing at 700 °C and GeSi nanocrystals after annealing at 800 and 900 °C. For all annealed samples, we report the observation of infrared photoluminescence (PL) at low temperatures in the spectral range 1300-2100 nm. The observation of PL at wavelengths close to 2000 nm may be due to defect-induced radiative transitions in the nanocrystals.

  17. Diamond Pixel Detectors and 3D Diamond Devices

    NASA Astrophysics Data System (ADS)

    Venturi, N.

    2016-12-01

    Results from detectors of poly-crystalline chemical vapour deposited (pCVD) diamond are presented. These include the first analysis of data of the ATLAS Diamond Beam Monitor (DBM). The DBM module consists of pCVD diamond sensors instrumented with pixellated FE-I4 front-end electronics. Six diamond telescopes, each with three modules, are placed symmetrically around the ATLAS interaction point. The DBM tracking capabilities allow it to discriminate between particles coming from the interaction point and background particles passing through the ATLAS detector. Also, analysis of test beam data of pCVD DBM modules are presented. A new low threshold tuning algorithm based on noise occupancy was developed which increases the DBM module signal to noise ratio significantly. Finally first results from prototypes of a novel detector using pCVD diamond and resistive electrodes in the bulk, forming a 3D diamond device, are discussed. 3D devices based on pCVD diamond were successfully tested with test beams at CERN. The measured charge is compared to that of a strip detector mounted on the same pCVD diamond showing that the 3D device collects significantly more charge than the planar device.

  18. Surface passivated silicon nanocrystals with stable luminescence synthesized by femtosecond laser ablation in solution.

    PubMed

    Tan, Dezhi; Ma, Zhijun; Xu, Beibei; Dai, Ye; Ma, Guohong; He, Min; Jin, Zuanming; Qiu, Jianrong

    2011-12-07

    We report the synthesis of silicon nanocrystals via a one-step route, namely, femtosecond laser ablation in 1-hexene under ambient conditions. The size of these silicon nanocrystals is 2.37 ± 0.56 nm as determined by transmission electron microscopy. Fourier transform infrared spectra and X-ray photoelectron spectra indicate that the surface of the silicon nanocrystals is passivated by organic molecules and is also partially oxidized by O(2) and H(2)O dissolved in the solution. These silicon nanocrystals emit stable and bright blue photoluminescence. We suggest that the photoluminescence originates from the radiative recombination of electron-hole pairs through the oxide-related centers on the surface of the silicon nanocrystals. The decay rate of the oxide-related surface recombination can be comparable to that of the direct band gap transition. In the excitation and emission spectra, a vibrational structure with nearly constant spacings (0.18 eV) is observed. We propose that the strong electron-phonon coupling between excitons and the longitudinal optical (LO) phonons of the Si-C vibration is responsible for this vibrational structure. The fluctuations in the peak resolution, about ±0.01 eV, are ascribed to the size distribution and presence of Si-O vibrations. These silicon nanocrystals offer stable luminescence and are synthesized through a "green" and simple route. They may find important applications in many fields, such as bioimaging and environmental science.

  19. Onion-like carbon from ultra-disperse diamond

    NASA Astrophysics Data System (ADS)

    Kuznetsov, Vladimir L.; Chuvilin, Andrey L.; Butenko, Yuri V.; Mal'kov, Igor Yu.; Titov, Vladimir M.

    1994-05-01

    A new material containing macroscopic quantities of onion-like carbon (OLC) particles is produced by heat treatment of ultra-disperse diamond (UDD) powder (2-6 nm). Annealing products (characterized by high-resolution electron microscopy) are presented by; (a) quasi-spherical particles with closed concentric graphite shells, (b) polyhedron particles with closed shells, (c) elongated particles with linked external graphite-like layers and closed quasi-spherical internal shells. The intermediates of UDD transformation have been registered. The structural transformation of UDD begins from the surface of the diamond particles towards a crystal bulk. The transformation rate of (111) diamond planes to graphite-like sheets is higher than that of other planes.

  20. Alternate current magnetic property characterization of nonstoichiometric zinc ferrite nanocrystals for inductor fabrication via a solution based process

    NASA Astrophysics Data System (ADS)

    Yun, Hongseok; Kim, Jungkwun; Paik, Taejong; Meng, Lingyao; Jo, Pil Sung; Kikkawa, James M.; Kagan, Cherie R.; Allen, Mark G.; Murray, Christopher B.

    2016-03-01

    We investigate the ac magnetic behavior of solution processable, non-stoichiometric zinc ferrite nanocrystals with a series of sizes and zinc concentrations. Nearly monodisperse ZnxFe3-xO4 nanocrystals (x = 0-0.25) with an average size ranging from 7.4 nm to 13.8 nm are synthesized by using a solvothermal method. All the nanocrystals are in a superparamagnetic state at 300 K, which is confirmed by Superconductive Quantum Interference Device magnetometry. Due to the doping of non-magnetic Zn2+ into A site of ferrite, the saturation magnetization of nanocrystals increases as the size and Zn concentration increases. The ac magnetic permeability measurements at radio frequencies reveal that the real part of the magnetic permeability of similarly sized ferrite nanocrystals can be enhanced by almost twofold as the Zn2+ doping level increases from 0 to 0.25. The integration of 12.3 nm Zn0.25Fe2.75O4 nanocrystals into a toroidal inductor and a solenoid inductor prepared via a simple solution cast process yields a higher quality factors than air core inductors with the same geometries up to 5 MHz and 9 MHz, respectively, which is in the regime of the switching frequencies for the advanced integrated power converters.

  1. Solvent-like ligand-coated ultrasmall cadmium selenide nanocrystals: strong electronic coupling in a self-organized assembly.

    PubMed

    Lawrence, Katie N; Johnson, Merrell A; Dolai, Sukanta; Kumbhar, Amar; Sardar, Rajesh

    2015-07-21

    Strong inter-nanocrystal electronic coupling is a prerequisite for delocalization of exciton wave functions and high conductivity. We report 170 meV electronic coupling energy of short chain poly(ethylene glycol) thiolate-coated ultrasmall (<2.5 nm in diameter) CdSe semiconductor nanocrystals (SNCs) in solution. Cryo-transmission electron microscopy analysis showed the formation of a pearl-necklace assembly of nanocrystals in solution with regular inter-nanocrystal spacing. The electronic coupling was studied as a function of CdSe nanocrystal size where the smallest nanocrystals exhibited the largest coupling energy. The electronic coupling in spin-cast thin-film (<200 nm in thickness) of poly(ethylene glycol) thiolate-coated CdSe SNCs was studied as a function of annealing temperature, where an unprecedentedly large, ∼400 meV coupling energy was observed for 1.6 nm diameter SNCs, which were coated with a thin layer of poly(ethylene glycol) thiolates. Small-angle X-ray scattering measurements showed that CdSe SNCs maintained an order array inside the films. The strong electronic coupling of SNCs in a self-organized film could facilitate the large-scale production of highly efficient electronic materials for advanced optoelectronic device application.

  2. Gamma-radiation synthesis and properties of superparamagnetic CS-ZnSe:Mn nanocrystals for biological labeling.

    PubMed

    Kang, Bin; Chang, Shu-Quan; Sun, Hao; Dai, Yao-Dong; Chen, Da

    2008-08-01

    Chitosan coated ZnSe:Mn (CS-ZnSe:Mn) nanocrystals were successfully synthesized in aqueous system through a gamma-radiation route at room temperature under ambient pressure. The structure and properties of nanocrystals were investigated with transmission electron microscope (TEM), fourier transform infrared spectrometer (FT-IR), ultraviolet-visible (UV-vis) spectrometer, photoluminescence emission (PL) spectra, X-ray Diffraction (XRD) and energy dispersion spectrum (EDS). Results showed that the diameter of these nanocrystals was about 4 nm with narrow size distribution. With the increase of doped Mn2+ concentration, strong emission peak at 610 nm was observed besides the weak emission peak at 425 nm since the non-radiative transition of 4T1(4G)-6A1(6S) level, resulting the transfer of fluorescence color from blue to orange. Moreover, analysis of SQUID magnetometer indicated that the nanocrystals were superparamagnetic with a saturation magnetization of 1.7 emu/g and a Curie-Weiss temperature of 14-15 K. Hep G2 cells were incubated in solution of nanocrystals and results showed that the synthesized nanocrystals could stain cytoplasm but could not enter into nucleus.

  3. Single-crystal diamond pyramids: synthesis and application for atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Tuyakova, Feruza T.; Obraztsova, Ekaterina A.; Ismagilov, Rinat R.

    2016-03-01

    Here we present the results of investigations aimed at the development and testing of robust, chemically inert single-crystal diamond probes for atomic force microscopy (AFM). The probes were prepared by assembling common silicon probes with micrometer-sized pyramid-shaped single-crystal diamonds (SCD). The SCD were obtained by the selective thermal oxidation of the polycrystalline films grown by chemical vapor deposition. Electrostatic spray of adhesive coating onto silicon probes was used to attach individual SCD. Geometrical parameters of produced AFM SCD probes were revealed with transmission electron microscopy: the apex angle of the pyramidal diamond crystallite was ˜10 deg, and the curvature radius at the apex was ˜2 to 10 nm. The diamond AFM probes were used for surface imaging of deoxyribonucleic acid deposited on graphite substrate. Obtained results demonstrate high efficiency of the diamond AFM probes, allowing improvement of the image quality compared to standard silicon probes.

  4. Injected nanocrystals for targeted drug delivery

    PubMed Central

    Lu, Yi; Li, Ye; Wu, Wei

    2016-01-01

    Nanocrystals are pure drug crystals with sizes in the nanometer range. Due to the advantages of high drug loading, platform stability, and ease of scaling-up, nanocrystals have been widely used to deliver poorly water-soluble drugs. Nanocrystals in the blood stream can be recognized and sequestered as exogenous materials by mononuclear phagocytic system (MPS) cells, leading to passive accumulation in MPS-rich organs, such as liver, spleen and lung. Particle size, morphology and surface modification affect the biodistribution of nanocrystals. Ligand conjugation and stimuli-responsive polymers can also be used to target nanocrystals to specific pathogenic sites. In this review, the progress on injected nanocrystals for targeted drug delivery is discussed following a brief introduction to nanocrystal preparation methods, i.e., top-down and bottom-up technologies. PMID:27006893

  5. KY3F10:Er3+/Yb3+ nanocrystals doped laser-induced self-written waveguide for optical amplification in the C-band

    NASA Astrophysics Data System (ADS)

    Xue, Xiaojie; Cheng, Tonglei; Suzuki, Takenobu; Ohishi, Yasutake

    2016-02-01

    We successfully synthesized Er3+/Yb3+ co-doped KY3F10 nanocrystals by a facile hydrothermal method. The average size of the as-prepared nanocrystals was about 60 nm based on the observation of scanning electron microscope. Under the excitation of a 976 nm laser, the Er3+/Yb3+ doped KY3F10 nanocrystals showed intense near-infrared emission band centered at 1539 nm. The optimal concentrations of Er3+ were carefully selected according to the quantum yield measurement for a stronger emission in the C-band. The as-prepared nanocrystals were dispersed into a monomer, bisphenol A ethoxylate diacrylates, in which self-written waveguides can be fabricated under the irradiation of an induced laser at 450 nm. The KY3F10: Er3+/Yb3+ nanocrystals embedded polymer waveguide were fabricated by laser-induced self-written technique. Two pieces of single mode fiber were well connected with the waveguide in the fabrication procedure. Under a 976 nm laser pumping, amplified spontaneous emission at 1539 nm was observed in the KY3F10: Er3+/Yb3+ nanocrystals doped waveguide.

  6. Semiconductor Nanocrystals for Biological Imaging

    SciTech Connect

    Fu, Aihua; Gu, Weiwei; Larabell, Carolyn; Alivisatos, A. Paul

    2005-06-28

    Conventional organic fluorophores suffer from poor photo stability, narrow absorption spectra and broad emission feature. Semiconductor nanocrystals, on the other hand, are highly photo-stable with broad absorption spectra and narrow size-tunable emission spectra. Recent advances in the synthesis of these materials have resulted in bright, sensitive, extremely photo-stable and biocompatible semiconductor fluorophores. Commercial availability facilitates their application in a variety of unprecedented biological experiments, including multiplexed cellular imaging, long-term in vitro and in vivo labeling, deep tissue structure mapping and single particle investigation of dynamic cellular processes. Semiconductor nanocrystals are one of the first examples of nanotechnology enabling a new class of biomedical applications.

  7. Design and investigation of properties of nanocrystalline diamond optical planar waveguides.

    PubMed

    Prajzler, Vaclav; Varga, Marian; Nekvindova, Pavla; Remes, Zdenek; Kromka, Alexander

    2013-04-08

    Diamond thin films have remarkable properties comparable with natural diamond. Because of these properties it is a very promising material for many various applications (sensors, heat sink, optical mirrors, chemical and radiation wear, cold cathodes, tissue engineering, etc.) In this paper we report about design, deposition and measurement of properties of optical planar waveguides fabricated from nanocrystalline diamond thin films. The nanocrystalline diamond planar waveguide was deposited by microwave plasma enhanced chemical vapor deposition and the structure of the deposited film was studied by scanning electron microscopy and Raman spectroscopy. The design of the presented planar waveguides was realized on the bases of modified dispersion equation and was schemed for 632.8 nm, 964 nm, 1 310 nm and 1 550 nm wavelengths. Waveguiding properties were examined by prism coupling technique and it was found that the diamond based planar optical element guided one fundamental mode for all measured wavelengths. Values of the refractive indices of our NCD thin film measured at various wavelengths were almost the same as those of natural diamond.

  8. The characteristic photoluminescence and EPR features of superdeep diamonds (São-Luis, Brazil)

    NASA Astrophysics Data System (ADS)

    Yuryeva, Olga P.; Rakhmanova, Mariana I.; Nadolinny, Vladimir A.; Zedgenizov, Dmitry A.; Shatsky, Vladislav S.; Kagi, Hiroyuki; Komarovskikh, Andrey Yu.

    2015-10-01

    Photoluminescence (PL) spectroscopy and electron paramagnetic resonance (EPR) were used for the first time to characterize properties of superdeep diamonds from the São-Luis alluvial deposits (Brazil). The infrared measurements showed the low nitrogen content (>50 of 87 diamonds from this locality were nitrogen free and belonged to type IIa) and simultaneously the extremely high level of nitrogen aggregation (pure type IaB being predominant), which indicates that diamonds under study might have formed under high pressure and temperature conditions. In most cases, PL features excited at various wavelengths (313, 473, and 532 nm) were indicative of different growth and post-growth processes during which PL centers could be formed via interaction between vacancies and nitrogen atoms. The overall presence of the 490.7 nm, H3, and H4 centers in the luminescence spectra attests to strong plastic deformations in these diamonds. The neutral vacancy known as the GR1 center has probably occurred in a number of crystals due to radiation damage in the post-growth period. The 558.5 nm PL center is found to be one of the most common defects in type IIa samples which is accompanied by the EPR center with g-factor of 2.00285. The 536 and 576 nm vibronic systems totally dominated the PL spectra of superdeep diamonds, while none of "normal" diamonds from the Mir pipe (Yakutia) with similar nitrogen characteristics showed the latter three PL centers.

  9. Tribological properties of nanocrystalline diamond films

    SciTech Connect

    Erdemir, A.; Fenske, G. R.; Kraus, A. R.; Gruen, D. M.; McCauley, T.; Csencsits, R. T.

    2000-01-26

    In this paper, the authors present the friction and wear properties of nanocrystalline diamond (NCD) films grown in A-fullerene (C{sub 60}) and Ar-CH{sub 4} microwave plasmas. Specifically, they address the fundamental tribological issues posed by these films during sliding against Si{sub 3}N{sub 4} counterfaces in ambient air and inert gases. Grain sizes of the films grown by the new method are very small (10--30 nm) and are much smoother (20-40 nm, root mean square) than those of films grown by the conventional H{sub 2}-CH{sub 4} microwave-assisted chemical-vapor-deposition (CVD) process. Transmission electron microscopy (TEM) revealed that the grain boundaries of these films are very sharp and free of nondiamond phases. The microcrystalline diamond (MCD) films grown by most conventional methods consist of large grains and a rough surface finish, which can cause severe abrasion during sliding against other materials. The friction coefficients of films grown by the new method (i.e., in Ar-C{sub 60} and Ar-CH{sub 4} plasmas) are comparable to those of natural diamond, and wear damage on counterface materials is minimal. Fundamental tribological studies indicate that these films may undergo phase transformation during long-duration, high-speed and/or high-load sliding tests and that the transformation products trapped at the sliding interfaces can intermittently dominate friction and wear performance. Using results from a combination of TEM, electron diffraction, Raman spectroscopy, and electron energy loss spectroscopy (EELS), they describe the structural chemistry of the debris particles trapped at the sliding interfaces and elucidate their possible effects on friction and wear of NCD films in dry N{sub 2}. Finally, they suggest a few potential applications in which NCD films can improve performance and service lives.

  10. Integration of colloidal silicon nanocrystals on metal electrodes in single-electron transistor

    NASA Astrophysics Data System (ADS)

    Higashikawa, Yasuhiro; Azuma, Yasuo; Majima, Yutaka; Kano, Shinya; Fujii, Minoru

    2016-11-01

    We develop a facile process to integrate colloidal silicon nanocrystals (Si NCs) with metal electrodes in a single-electron transistor by self-assembly. Gold (Au) surface is modified by an amine-terminated self-assembled monolayer to have a positive potential. All-inorganic boron (B) and phosphorus (P) codoped Si NCs, with a negative surface potential and size-controllability, are selectively adsorbed on an amine-terminated Au surface by electrostatic attraction. We demonstrate the fabrication of SETs consisting of electroless-plated Au nanogap electrodes and codoped Si NCs using this process and observation of clear Coulomb diamonds at 9 K.

  11. White electroluminescence of n-ZnO:Al/p-diamond heterostructure devices

    NASA Astrophysics Data System (ADS)

    Yang, Can; Wang, Xiao-Ping; Wang, Li-Jun; Pan, Xiu-Fang; Li, Song-Kun; Jing, Long-Wei

    2013-08-01

    An n-ZnO:Al/p-boron-doped diamond heterostructure electroluminescent device is produced, and a rectifying behavior can be observed. The electroluminescence spectrum at room temperature exhibits two visible bands centred at 450 nm-485 nm (blue emission) and 570 nm-640 nm (yellow emission). Light emission with a luminance of 15 cd/m2 is observed from the electroluminescent device at a forward applied voltage of 85 V, which is distinguished from white light by the naked eye.

  12. Topomineralogy of the Siberian diamonds

    NASA Astrophysics Data System (ADS)

    Afanasyev, Valentin; Lobanov, Sergey; Vasiliy, Koptil; Bogdan, Pomazanskiy; Alexander, Gerasimchuk; Nikolay, Pokhilenko

    2010-05-01

    Diamond placers are widespread in the modern alluvial deposits and ancient sedimentary collectors of the Siberian craton and can be divided into two major types: 1) related with the rich and famous kimberlites such as Mir and International pipe and 2) with unidentified root source. The lattert are wide spread, industrially significant and in use in the north-east of the Siberian craton. Yet, kimberlites known in the north-east of the Siberian craton have poor diamond concentrations or non-diamondiferous at all. A contradiction occur between high alluvial and extremely-low host diamond content of this region. Detailed studies of this problem led to the fact that diamonds from the alluvial deposits of the Siberian craton, as well as other diamondiferous regions, show broader spectrum of typomorphic features than diamonds from the known kimberlites. Moreover, some diamond groups are not typical for the phanerozoic kimberlites of Siberia, or do not occur in significant amounts. The foregoing suggests that diamonds from the unknown host rock type occur in the diamond placers of the Siberian craton along with typical kimberlite diamonds. Based on the detailed studies of the typomorphic features of the alluvial diamonds from Siberian craton 5 parasteresis groups, probably related to different host rock types, were distinguished. Parasteresis is a regular spatial mineral association which are united by single geological process, such as kimberlite indicator minerals and diamonds from kimberlites which differ in genesis but united by the whole kimberlitic process. Parasteresis 1 (kimberlite-type) involves diamonds which are common for the phanerozoic kimberlites. Parasteresis 2 (supposed to be lamproitic) includes roundish (cryptolaminar) diamonds of dodecahedron habit, the so called "brazilian" or "ural" types. In Siberian phanerozoic industrial kimberlites the part of such diamonds does not exceed 15%. That is the diamonds which dominate in the placers of the Urals and

  13. Twin Quintuplets in CVD Diamond

    DTIC Science & Technology

    1992-08-26

    microscopy (HRTEM). We conclude that the twin quintuplets have two main morphologies. The first consists of four Sigma = 3 twin boundaries and one...slightly more than the 70.53 deg tilt of a Sigma = 3 boundary. These grain boundaries and the conventional diamond lattice twin boundaries are the only types of boundaries that we have observed in CVD diamond.

  14. Surface morphology and bond characterization of nanocrystalline diamonds grown on tungsten carbide via hot filament chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Hamzah, E.; Yong, T. M.; Mat Yajid, M. A.

    2013-06-01

    Nanocrystalline diamonds (NCDs) were deposited on chemically prepared tungsten carbide substrates via hot filament chemical vapor deposition. The surface morphology of the NCDs was examined using field emission scanning electron microscopy. The NCDs formed a ballas morphology evenly across the tungsten carbide surface. Overetching affected the diamond deposition by causing the ballas to form aggregations. Cross-sectional fragmentation using a diamond wafering blade caused the nanocrystalline diamond to fragment at overetched boundaries, and delamination only occurred 30-50 µm off the edge and revealed that the thickness of the diamond film was 6 µm. Grazing XRD is an effective method to identify diamonds even at the nanoscale. The crystallite size was calculated to be 18.4 nm by modeling. Cross-sectional TEM analysis indicated that the diamond grain size was approximately 10-30 nm near the interface. Amorphous carbon, an embedded diamond and voids were also observed. TEM also revealed that the tungsten carbide surface undulates. The nanocrystalline diamonds nucleated and grew on the tungsten carbide (100) planes in the <111> direction, forming (111) planes, as observed from HRTEM, d-spacing measurements, SAD and FFT analyses for a FIB-prepared sample.

  15. Preparation of nanorod-like anatase TiO2 nanocrystals and their photovoltaic properties.

    PubMed

    Zhang, Qinghong; Li, Shuang; Li, Yaogang; Wang, Hongzhi

    2011-12-01

    Anatase TiO2 nanocrystals with the high specific surface area were prepared by the hydrothermal treatment of anatase TiO2 sols at the temperature of 150 degrees C and above. When TiO2 sols with a lower content of TiO2 and at a relatively high pH value were hydrothermal treated, the dispersible and nanorod-like TiO2 nanocrystals were formed via the oriented attachment. The nanorod-like TiO2 nanocrystals with an aspect ratio of larger than 5 and a mean diameter of less than 7 nm were obtained in the absence of organic compounds. The as-prepared TiO2 nanocrystals were characterized with X-ray diffraction, transmission electron microscopy and BET surface area techniques. The TiO2 nanostructures were deposited on the FTO conductive glass as the anodic electrode for the dye-sensitized solar cells (DSSCs) and assembled into solar cells. The derived solar cells showed a conversion efficiency of 6.12% under 1 sun illumination of simulated sunlight and external quantum efficiency (EQE) of more than 60% at the wavelength of 550 nm. The DSSCs from the anatase nanorods has a higher open circuit voltage compared to the spherical nanocrystals.

  16. Two- and three-dimensional ultrananocrystalline diamond (UNCD) structures for a high resolution diamond-based MEMS technology.

    SciTech Connect

    Auciello, O.; Krauss, A. R.; Gruen, D. M.; Busmann, H. G.; Meyer, E. M.; Tucek, J.; Sumant, A.; Jayatissa, A.; Moldovan, N.; Mancini, D. C.; Gardos, M. N.

    2000-01-17

    Silicon is currently the most commonly used material for the fabrication of microelectromechanical systems (MEMS). However, silicon-based MEMS will not be suitable for long-endurance devices involving components rotating at high speed, where friction and wear need to be minimized, components such as 2-D cantilevers that may be subjected to very large flexural displacements, where stiction is a problem, or components that will be exposed to corrosive environments. The mechanical, thermal, chemical, and tribological properties of diamond make it an ideal material for the fabrication of long-endurance MEMS components. Cost-effective fabrication of these components could in principle be achieved by coating Si with diamond films and using conventional lithographic patterning methods in conjunction with e. g. sacrificial Ti or SiO{sub 2} layers. However, diamond coatings grown by conventional chemical vapor deposition (CVD) methods exhibit a coarse-grained structure that prevents high-resolution patterning, or a fine-grained microstructure with a significant amount of intergranular non-diamond carbon. The authors demonstrate here the fabrication of 2-D and 3-D phase-pure ultrananocrystalline diamond (UNCD) MEMS components by coating Si with UNCD films, coupled with lithographic patterning methods involving sacrificial release layers. UNCD films are grown by microwave plasma CVD using C{sub 60}-Ar or CH{sub 4}-Ar gas mixtures, which result in films that have 3--5 nm grain size, are 10--20 times smoother than conventionally grown diamond films, are extremely resistant to corrosive environments, and are predicted to have a brittle fracture strength similar to that of single crystal diamond.

  17. High efficiency diamond solar cells

    DOEpatents

    Gruen, Dieter M.

    2008-05-06

    A photovoltaic device and method of making same. A layer of p-doped microcrystalline diamond is deposited on a layer of n-doped ultrananocrystalline diamond such as by providing a substrate in a chamber, providing a first atmosphere containing about 1% by volume CH.sub.4 and about 99% by volume H.sub.2 with dopant quantities of a boron compound, subjecting the atmosphere to microwave energy to deposit a p-doped microcrystalline diamond layer on the substrate, providing a second atmosphere of about 1% by volume CH.sub.4 and about 89% by volume Ar and about 10% by volume N.sub.2, subjecting the second atmosphere to microwave energy to deposit a n-doped ultrananocrystalline diamond layer on the p-doped microcrystalline diamond layer. Electrodes and leads are added to conduct electrical energy when the layers are irradiated.

  18. Engineering high refractive index sensitivity through the internal and external composition of bimetallic nanocrystals.

    PubMed

    Smith, Alison F; Harvey, Samantha M; Skrabalak, Sara E; Weiner, Rebecca G

    2016-10-14

    High refractive index sensitivity (RIS) of branched Au-Pd nanocrystals (NCs) is engineered through lowering the dielectric dispersion at the NC resonant wavelength with internal or external atomic % Pd. To our knowledge, these NCs display the highest ensemble RIS measurement for colloids with LSPR maximum band positions ≤900 nm, and these results are corroborated with FDTD computations.

  19. CdSe nanocrystals ingrained dielectric nanocomposites: synthesis and photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Dey, Chirantan; Goswami, Madhumita; Karmakar, Basudeb

    2015-01-01

    Cadmium selenide (CdSe) nanocrystals ingrained dielectric nanocomposites in a B2O3-SiO2-Al2O3-Na2O-K2O borosilicate glass system were synthesized by a single step in situ melt quenching technique. The sizes of the nanocrystals as well as the band gap of the nanocomposites were controlled by both concentration of CdSe and post thermal treatment duration. The nanocomposites were characterized by different instrumental techniques including detailed photoluminescence studies. The sizes of the CdSe nanocrystals were found to alter in the range 4-16 nm as estimated from the effective mass approximation model and optical absorption spectroscopy. However, the TEM analysis revealed the generation of two different size ranges, 3-4 and 23-45 nm, of the particles within the dielectric matrix. Selected area diffraction (SAED) and x-ray diffraction (XRD) patterns authenticate the formation of hexagonal nanostructures of CdSe. These nanocomposites were found to be capable of exhibiting strong visible red luminescence around 715 nm on excitation at 446 nm. This has originated from the electron-hole recombination of CdSe nanocrystal and defects or traps related transitions. The properties of these nanocomposites advocate their significant applications as semiconductor based luminescent materials.

  20. Nanocrystal ghosting: Extensive radiation damage in MgO induced by low-energy electrons

    NASA Astrophysics Data System (ADS)

    Frankenfield, Zackery; Kane, Kenneth; Sawyer, William H.

    2017-03-01

    We report direct evidence of extensive radiation damage in MgO nanocrystals due to intense bombardment (2 × 10 electrons/nm sec) by electrons with beam energies between 60 keV and 120 keV. Based upon a minimum intensity necessary to produce the observed damage, we present an explanation based on the Knotek-Feibelman process.

  1. Molecular Limits to the Quantum Confinement Model in Diamond Clusters

    SciTech Connect

    Willey, T M; Bostedt, C; van Buuren, T; Dahl, J E; Liu, S E; Carlson, R K; Terminello, L J; Moller, T

    2005-04-07

    The electronic structure of monodisperse, hydrogen-passivated diamond clusters in the gas phase has been studied with x-ray absorption spectroscopy. The data show that the bulk-related unoccupied states do not exhibit any quantum confinement. Additionally, density of states below the bulk absorption edge appears, consisting of features correlated to CH and CH{sub 2} hydrogen surface termination, resulting in an effective red shift of the lowest unoccupied states. The results contradict the commonly used and very successful quantum confinement model for semiconductors which predicts increasing band edge blue shifts with decreasing particle size. Our findings indicate that in the ultimate size limit for nanocrystals a more molecular description is necessary.

  2. Laser-induced refractive index changes in nanocrystalline diamond membranes.

    PubMed

    Preclíková, Jana; Kromka, Alexander; Rezek, Bohuslav; Malý, Petr

    2010-02-15

    We have observed what we believe to be a new phenomenon in nanocrystalline diamond membranes. The optical thickness of the membrane is changed under laser irradiation, which leads to a spectral shift of interference fringes in the transmission and photoluminescence spectra of high-quality thin self-supporting nanocrystalline membranes. The direction of the spectral shift (red/blue) can be tuned by the ambient air pressure. The effect is reversible and is accompanied by changes in photoluminescence intensity. We interpret the results in terms of the changes in the index of refraction caused by the photoinduced adsorption/desorption of air molecules that subsequently affect the properties of subgap energy states related to the surface and the grain boundaries of the nanocrystals.

  3. Gardner-Diamond syndrome.

    PubMed

    Park, Joyce H; Yagerman, Sarah; Feng, Hao; Kim, Randie H; Meehan, Shane A; Lewin, Jesse

    2016-12-15

    Gardner-Diamond syndrome, which also is knownas autoerythrocyte sensitization disorder, is a raresyndrome of inflammatory, edematous papulesthat evolve into painful ecchymoses on the trunkand lower legs after a period of stress with no priorhistory of trauma. This syndrome usually occurs inwomen with a history of psychiatric disorders, themost common one being depression. Although theexact mechanism of injury is not well understood,it is hypothesized that these patients haveautoantibodies to phosphatidylserine, which is aphospholipid membrane component in erythrocytes.Treatment for this disorder includes symptomatictherapies and psychotropic medications to treat theunderlying psychiatric disorder.

  4. Diamond Anvil Cell Techniques

    NASA Astrophysics Data System (ADS)

    Piermarini, Gasper J.

    It has often been said that scientific advances are made either in a dramatic and revolutionary way, or, as in the case of the diamond anvil cell (DAC), in a slow and evolutionary manner over a period of several years. For more than 2 decades, commencing in 1958, the DAC developed stepwise from a rather crude qualitative instrument to the sophisticated quantitative research tool it is today, capable of routinely producing sustained static pressures in the multi-megabar range and readily adaptable to numerous scientific measurement techniques because of its optical accessibility, miniature size, and portability.

  5. Oxygen transport in unreduced, reduced and Rh(III)-doped CeO2 nanocrystals.

    PubMed

    Sayle, Thi X T; Parker, Stephen C; Sayle, Dean C

    2007-01-01

    Ceria, CeO2, based materials are a major (active) component of exhaust catalysts and promising candidates for solid oxide fuel cells. In this capacity, oxygen transport through the material is pivotal. Here, we explore whether oxygen transport is influenced (desirably increased) compared with transport within the bulk parent material by traversing to the nanoscale. In particular, atomistic models for ceria nanocrystals, including perfect: CeO2; reduced: CeO1.95 and doped: Rh0.1Ce0.9O1.95, have been generated. The nanocrystals were about 8 nm in diameter and each comprised about 16,000 atoms. Oxygen transport can also be influenced, sometimes profoundly, by microstructural features such as dislocations and grain-boundaries. However, these are difficult to generate within an atomistic model using, for example, symmetry operations. Accordingly, we crystallised the nanocrystals from an amorphous precursor, which facilitated the evolution of a variety of microstructures including: twin-boundaries and more general grain-boundaries and grain-junctions, dislocations and epitaxy, isolated and associated point defects. The shapes of the nanocrystals are in accord with HRTEM data and comprise octahedral morphologies with {111} surfaces, truncated by (dipolar) {100} surfaces together with a complex array of steps, edges and corners. Oxygen transport data was then calculated using these models and compared with data calculated previously for CeO1.97/ YSZ thin films and the (bulk) parent material, CeO197. Oxygen transport was calculated to increase in the order: CeO2 nanocrystal < (reduced) CeO1.95 nanocrystal approximately Rh0.1Ce0.9O1.95 nanocrystal < CeO1.97/YSZ thin film < (reduced) CeO1.97 (bulk) parent material; the mechanism was determined to be primarily vacancy driven. Our findings indicate that reducing one- (thin film) or especially three- (nanocrystal) dimensions to the nanoscale may prove deleterious to oxygen transport. Conversely, we observed dynamic evolution and

  6. Flexible and fragmentable tandem photosensitive nanocrystal skins

    NASA Astrophysics Data System (ADS)

    Akhavan, S.; Uran, C.; Bozok, B.; Gungor, K.; Kelestemur, Y.; Lesnyak, V.; Gaponik, N.; Eychmüller, A.; Demir, H. V.

    2016-02-01

    We proposed and demonstrated the first account of large-area, semi-transparent, tandem photosensitive nanocrystal skins (PNSs) constructed on flexible substrates operating on the principle of photogenerated potential buildup, which avoid the need for applying an external bias and circumvent the current-matching limitation between junctions. We successfully fabricated and operated the tandem PNSs composed of single monolayers of colloidal water-soluble CdTe and CdHgTe nanocrystals (NCs) in adjacent junctions on a Kapton polymer tape. Owing to the usage of a single NC layer in each junction, noise generation was significantly reduced while keeping the resulting PNS films considerably transparent. In each junction, photogenerated excitons are dissociated at the interface of the semi-transparent Al electrode and the NC layer, with holes migrating to the contact electrode and electrons trapped in the NCs. As a result, the tandem PNSs lead to an open-circuit photovoltage buildup equal to the sum of those of the two single junctions, exhibiting a total voltage buildup of 128.4 mV at an excitation intensity of 75.8 μW cm-2 at 350 nm. Furthermore, we showed that these flexible PNSs could be bent over 3.5 mm radius of curvature and cut out in arbitrary shapes without damaging the operation of individual parts and without introducing any significant loss in the total sensitivity. These findings indicate that the NC skins are promising as building blocks to make low-cost, flexible, large-area UV/visible sensing platforms with highly efficient full-spectrum conversion.We proposed and demonstrated the first account of large-area, semi-transparent, tandem photosensitive nanocrystal skins (PNSs) constructed on flexible substrates operating on the principle of photogenerated potential buildup, which avoid the need for applying an external bias and circumvent the current-matching limitation between junctions. We successfully fabricated and operated the tandem PNSs composed of

  7. The Toucan's Diamond

    NASA Astrophysics Data System (ADS)

    2006-06-01

    The Southern constellation Tucana (the Toucan) is probably best known as the home of the Small Magellanic Cloud, one of the satellite galaxies of the Milky Way. But Tucana also hosts another famous object that shines thousands of lights, like a magnificent, oversized diamond in the sky: the globular cluster 47 Tucanae. More popularly known as 47 Tuc, it is surpassed in size and brightness by only one other globular cluster, Omega Centauri. Globular clusters are gigantic families of stars, comprising several tens of thousands of stars, all thought to be born at the same time from the same cloud of gas [1]. As such, they constitute unique laboratories for the study of how stars evolve and interact. This is even more so because they are located at the same distance, so the brightness of different types of stars, at different stages in their evolution can be directly compared. The stars in globular clusters are held together by their mutual gravity which gives them their spherical shape, hence their name. Globular clusters are thought to be among the oldest objects in our Milky Way galaxy, and contain therefore mostly old, low-mass stars. ESO PR Photo 20/06 ESO PR Photo 20/06 Globular Cluster 47 Tuc 47 Tucanae is an impressive globular cluster that is visible with the unaided eye from the southern hemisphere. It was discovered in 1751 by the French astronomer Nicholas Louis de Lacaille who cataloged it in his list of southern nebulous objects. Located about 16 000 light years away, it has a total mass of about 1 million times the mass of the Sun and is 120 light years across, making it appear on the sky as big as the full moon. The colour image of 47 Tucanae presented here was taken with FORS1 on ESO's Very Large Telescope in 2001. The image covers only the densest, very central part of the cluster. The globular cluster extends in reality four times further away! As can be seen however, the density of stars rapidly drops off when moving away from the centre. The red

  8. Flexible and fragmentable tandem photosensitive nanocrystal skins.

    PubMed

    Akhavan, S; Uran, C; Bozok, B; Gungor, K; Kelestemur, Y; Lesnyak, V; Gaponik, N; Eychmüller, A; Demir, H V

    2016-02-28

    We proposed and demonstrated the first account of large-area, semi-transparent, tandem photosensitive nanocrystal skins (PNSs) constructed on flexible substrates operating on the principle of photogenerated potential buildup, which avoid the need for applying an external bias and circumvent the current-matching limitation between junctions. We successfully fabricated and operated the tandem PNSs composed of single monolayers of colloidal water-soluble CdTe and CdHgTe nanocrystals (NCs) in adjacent junctions on a Kapton polymer tape. Owing to the usage of a single NC layer in each junction, noise generation was significantly reduced while keeping the resulting PNS films considerably transparent. In each junction, photogenerated excitons are dissociated at the interface of the semi-transparent Al electrode and the NC layer, with holes migrating to the contact electrode and electrons trapped in the NCs. As a result, the tandem PNSs lead to an open-circuit photovoltage buildup equal to the sum of those of the two single junctions, exhibiting a total voltage buildup of 128.4 mV at an excitation intensity of 75.8 μW cm(-2) at 350 nm. Furthermore, we showed that these flexible PNSs could be bent over 3.5 mm radius of curvature and cut out in arbitrary shapes without damaging the operation of individual parts and without introducing any significant loss in the total sensitivity. These findings indicate that the NC skins are promising as building blocks to make low-cost, flexible, large-area UV/visible sensing platforms with highly efficient full-spectrum conversion.

  9. Innovative machining method on CVD diamond thin film

    NASA Astrophysics Data System (ADS)

    Tsai, Hung-Yin; Cheng, Chih-Yung; Liu, Pin-Yin; Wu, Tung-Chuan

    2002-11-01

    Chemical vapor deposition (CVD) diamond has outstanding properties, including low thermal expansion, high chemical resistance and high acoustic propagation and has been widely used in optical, electrical, mechanical, chemical and thermal applications. Since synthesized diamond film results in large surface roughness, the surface treatment or polishing should be applied to expand the applications. Although reducing surface roughness by mechanical and etching methods have been investigated, the cost on the complicated equipment and on the long processing time is the most particular important issue. A new method is developed in the present study to approach the smooth surface by a catalytic grinding wheel. As grinding, the catalytic reaction occurs at the contact area between the grinding wheel and the diamond surface, and sp3 structure of diamond can be converted to sp2 structure with lower bonding energy; therefore, the lower surface roughness. Consequently, the average surface roughness is extremely improved from 230 nm to 20 nm, and the processing time can be shortened 10 times more than conventional methods, either lapping, or chemical assisted lapping.

  10. Find of anisotropic carbonic matter on a curve-faced diamond crystal

    NASA Astrophysics Data System (ADS)

    Brodskaya, R. L.; Golubev, E. A.; Isaenko, S. I.

    2016-12-01

    The study focuses on the identification and investigation of crystal-optical anisotropy phenomena observed on surfaces of a curve-faced diamond crystal found in alluvial sediments of the Lower Us'va River in Perm territory. Raman spectroscopy and atomic force microscopy show that interference of polarized light reflected from the tetrahexahedral faces of the diamond crystal is inspired by anisotropic carbonic matter, which appears as a film with graphene or nanographite structure and about 4 nm in thickness. The data allow us to suggest the formation conditions of curve-faced diamond crystals and origin of nanocrystalline carbonic matter on their faces.

  11. Laser patterning of diamond. Part II. Surface nondiamond carbon formation and its removal

    NASA Astrophysics Data System (ADS)

    Smedley, John; Jaye, Cherno; Bohon, Jen; Rao, Triveni; Fischer, Daniel A.

    2009-06-01

    As diamond becomes more prevalent for electronic and research applications, methods of patterning diamond will be required. One such method, laser ablation, has been investigated in a related work. We report on the formation of surface nondiamond carbon during laser ablation of both polycrystalline and single-crystal synthetic diamonds. Near edge x-ray absorption fine structure spectroscopy was used to confirm that the nondiamond carbon layer formed during the ablation was amorphous, and Fourier transform infrared absorption spectroscopy (FTIR) was used to estimate the thickness of this layer to be ˜60 nm. Ozone cleaning was used to remove the nondiamond carbon layer.

  12. Increasing the creation yield of shallow single defects in diamond by surface plasma treatment

    SciTech Connect

    Osterkamp, Christian; Scharpf, Jochen; Naydenov, Boris; Jelezko, Fedor; Pezzagna, Sebastien; Meijer, Jan; Diemant, Thomas; Jürgen Behm, Rolf

    2013-11-04

    Single Nitrogen-Vacancy (NV) centers in diamond close to the crystal surface are very promising magnetic field sensors with very high sensitivity. Here, we report the enhanced creation of very shallow (less than 3 nm below the diamond surface) NV centers by using fluorine and oxygen plasma treatment. We observe a four fold increase—from 0.11% to about 0.45% in the production yield when the sample surface is terminated with fluorine or oxygen atoms. This effect is explained by the stabilization of the NV's negative charge state which is influenced by the various defects present on the diamond surface.

  13. Growth of diamond microcrystals by the oriented attachment mechanism at high pressure and high temperature

    NASA Astrophysics Data System (ADS)

    Kidalov, S. V.; Shakhov, F. M.; Shvidchenko, A. V.; Smirnov, A. N.; Sokolov, V. V.; Yagovkina, M. A.; Vul', A. Ya.

    2017-01-01

    For the first time it has been experimentally shown that a powder of detonation nanodiamonds (DND) and a saturated acyclic hydrocarbon, mono- or dibasic alcohol, used as the reaction mixture after treatment at high pressures (5-8 GPa) and high temperatures (1300-1800°C) results in the formation of diamond single crystals up to 15 micron in size. The Raman spectrum indicates that the diamonds have a perfect of crystal structure. It has been suggested that the oriented attachment mechanism is responsible for growth of micrometer-size diamond single crystals out of DND particles with sizes of about 5 nm under these technological conditions.

  14. Laser Patterning of Diamond. Part II. Surface Nondiamond Carbon Formation and its Removal

    SciTech Connect

    Smedley, J.; Jaye, C; Bohon, J; Rao, T; Fischer, D

    2009-01-01

    As diamond becomes more prevalent for electronic and research applications, methods of patterning diamond will be required. One such method, laser ablation, has been investigated in a related work. We report on the formation of surface nondiamond carbon during laser ablation of both polycrystalline and single-crystal synthetic diamonds. Near edge x-ray absorption fine structure spectroscopy was used to confirm that the nondiamond carbon layer formed during the ablation was amorphous, and Fourier transform infrared absorption spectroscopy (FTIR) was used to estimate the thickness of this layer to be {approx} 60 nm. Ozone cleaning was used to remove the nondiamond carbon layer.

  15. Nanocrystals Research for Energy Efficient and Clean Energy Technologies:

    SciTech Connect

    Rosenthal, Sandra J

    2013-12-17

    Efforts centered on: nanocrystal photovoltaic fabrication, ultrafast dynamics and aberration-corrected STEM characterization of II-VI core, core/shell and alloyed nanocrystals, and fundamental investigation and applications of ultrasmall white light-emitting CdSe nanocrystal.

  16. CVD Diamond, DLC, and c-BN Coatings for Solid Film Lubrication

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa

    1998-01-01

    When the main criteria for judging coating performance were coefficient of friction and wear rate, which had to be less than 0.1 and 10(exp -6) mm(exp 3)/N-m, respectively, carbon- and nitrogen-ion-implanted, fine-grain CVD diamond and DLC ion beam deposited on fine-grain CVD diamond met the requirements regardless of environment (vacuum, nitrogen, and air).

  17. CVD Diamond, DLC, and c-BN Coatings for Solid Film Lubrication

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Murakawa, Masao; Watanabe, Shuichi; Takeuchi, Sadao; Miyake, Shojiro; Wu, Richard L. C.

    1998-01-01

    The main criteria for judging coating performance were coefficient of friction and wear rate, which had to be less than 0.1 and 10(exp -6) cubic MM /(N*m), respectively. Carbon- and nitrogen-ion-implanted, fine-grain, chemical-vapor-deposited (CVD) diamond and diamondlike carbon (DLC) ion beam deposited on fine-grain CVD diamond met the criteria regardless of environment (vacuum, nitrogen, and air).

  18. Electron energy loss spectrometry of interstellar diamonds

    NASA Technical Reports Server (NTRS)

    Bernatowicz, Thomas J.; Gibbons, Patrick C.; Lewis, Roy S.

    1990-01-01

    The results are reported of electron energy loss spectra (EELS) measurements on diamond residues from carbonaceous meteorites designed to elucidate the structure and composition of interstellar diamonds. Dynamic effective medium theory is used to model the dielectric properties of the diamonds and in particular to synthesize the observed spectra as mixtures of diamond and various pi-bonded carbons. The results are shown to be quantitatively consistent with the idea that diamonds and their surfaces are the only contributors to the electron energy loss spectra of the diamond residues and that these peculiar spectra are the result of the exceptionally small grain size and large specific surface area of the interstellar diamonds.

  19. Dual-functional CeO2:Eu3+ nanocrystals for performance-enhanced dye-sensitized solar cells.

    PubMed

    Roh, Jongmin; Hwang, Sun Hye; Jang, Jyongsik

    2014-11-26

    Single-crystalline, octahedral CeO2:Eu3+ nanocrystals, successfully prepared using a simple hydrothermal method, were investigated to determine their photovoltaic properties in an effort to enhance the light-harvesting efficiency of dye-sensitized solar cells (DSSCs). The size of the CeO2:Eu3+ nanocrystals (300-400 nm), as well as their mirrorlike facets, significantly improved the diffuse reflectance of visible light. Excitation of the CeO2:Eu3+ nanocrystal with 330 nm ultraviolet light was re-emitted via downconversion photoluminescence (PL) from 570 to 672 nm, corresponding to the 5D0→7FJ transition in the Eu3+ ions. Downconversion PL was dominant at 590 nm and had a maximum intensity for 1 mol % Eu3+. The CeO2:Eu3+ nanocrystal-based DSSCs exhibited a power conversion efficiency of 8.36%, an increase of 14%, compared with conventional TiO2 nanoparticle-based DSSCs, because of the strong light-scattering and downconversion PL of the CeO2:Eu3+ nanocrystals.

  20. Processing of Diamond for Integrated Optic Devices Using Q-Switched Nd:YAG Laser at Different Wavelengths

    NASA Astrophysics Data System (ADS)

    Sudheer, S. K.; Pillai, V. P. Mahadevan; Nayar, V. U.

    In the present investigation, a Q-switched Nd:YAG laser is used to study the various aspects of diamond processing for fabricating integrated optic and UV optoelectronic devices. Diamond is a better choice of substrate compared to silicon and gallium arsenide for the fabrication of waveguides to perform operations such as modulation, switching, multiplexing, and filtering, particularly in the ultraviolet spectrum. The experimental setup of the present investigation consists of two Q-Switched Nd:YAG lasers capable of operating at wavelengths of 1064 nm and 532 nm. The diamond cutting is performed using these two wavelengths by making the "V"-shaped groove with various opening angle. The variation of material loss of diamond during cutting is noted for the two wavelengths. The cut surface morphology and elemental and structural analysis of graphite formed during processing in both cases are compared using scanning electron microscopy (SEM) and laser Raman spectroscopy. Both the Q-Switched Nd:YAG laser systems (at 1064 nm and 532 nm) show very good performance in terms of peak-to-peak output stability, minimal spot diameter, smaller divergence angle, higher peak power in Q-switched mode, and good fundamental TEM00 mode quality for processing natural diamond stones. Less material loss and minimal micro cracks are achieved with wavelength 532 nm whereas a better diamond cut surface is achieved with processing at 1064 nm with minimum roughness.

  1. Chemical-Vapor-Deposited Diamond Film

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa

    1999-01-01

    This chapter describes the nature of clean and contaminated diamond surfaces, Chemical-vapor-deposited (CVD) diamond film deposition technology, analytical techniques and the results of research on CVD diamond films, and the general properties of CVD diamond films. Further, it describes the friction and wear properties of CVD diamond films in the atmosphere, in a controlled nitrogen environment, and in an ultra-high-vacuum environment.

  2. Toxicity of nanocrystal quantum dots: the relevance of surface modifications.

    PubMed

    Hoshino, Akiyoshi; Hanada, Sanshiro; Yamamoto, Kenji

    2011-07-01

    With the development of nanotechnology, nanometer-sized products smaller than several 100 nm have been applied for all areas of science and technology. The nanometer-sized products, including carbon nanotubes, fullerene derivatives, and nanocrystals made of various materials, are widely employed as novel tools in various fields, not only in material engineering, electronics, plastics, automobile, aviation, and aerospace industries, but also even in cellular biology, molecular biology, and basic and clinical medical fields. In particular, nanocrystal quantum dots (QDs) have been widely used in biological and medical studies because of their far brighter photoemission and photostability. The physical and chemical properties of QDs have been circumstantially investigated, but little is known about the potential harmful effects of QDs on human health. In addition to the physical and chemical properties of the QDs, their toxicity and biological behavior are generally regulated by three other conditions: (1) the QD core material itself, (2) the surface modifications of the QD, and (3) the external environmental condition of the QDs. We herein report on the in vitro and in vivo toxicity and biological behavior of nanocrystals such as QDs. Accumulating evidence suggests that the QD-capping material, rather than the core metalloid complex, is responsible for the majority of their toxicity and biological activity. For example, molecules covered with a toxic agent showed cytotoxicity, whereas QDs conjugated with biomolecules retained the biological effects of the conjugate.

  3. Mechanochemical synthesis and reactivity of PbS nanocrystals

    NASA Astrophysics Data System (ADS)

    Baláž, Peter; Pourghahramani, Parviz; Achimovičová, Marcela; Dutková, Erika; Kováč, Jaroslav; Šatka, Alexander; Jiang, Jiangzhong

    2011-10-01

    PbS nanocrystals using surfactant assisted mechanochemical synthesis have been prepared by co-milling of lead acetate (CH 3COO) 2Pb rad 3H 2O and sodium sulfide Na 2S rad 9H 2O. The methods of XRD, FE-SEM, TEM (HRTEM), UV-vis, specific surface area measurements as well as reactivity in acidic FeCl 3 media were used for the nanocrystals characterization. The XRD patterns confirmed the presence of galena PbS (JCPDS 5-592) whatever treatment conditions were applied. The strong observable peaks indicate the highly crystalline nature in formation of PbS nanostructures where preferential crystal growth in the (2 0 0) direction after addition of ethylenediamine (EDA), sodiumdodecylsulphate (SDS) and ethylendiaminetetraacetic disodium salt dihydrate (EDH) surfactants has been observed. The surface weighted crystallite sizes 3, 8, 11 and 19 nm have been calculated from XRD data using the Warren-Averbach method for surfactant-free and/or EDA, SDS and EDH surfactants assisted mechanochemical synthesis. The leaching rate of galena PbS in acidic FeCl 3 solution has been studied. The dependence of PbS nanocrystals reactivity on preferential growth parameter is documented. The highest value of the specific rate constant of leaching, k0/ SA has been obtained for the mechanochemically synthesized PbS in presence of EDH surfactant.

  4. Non-injection synthesis of monodisperse Cu-Fe-S nanocrystals and their size dependent properties.

    PubMed

    Gabka, Grzegorz; Bujak, Piotr; Żukrowski, Jan; Zabost, Damian; Kotwica, Kamil; Malinowska, Karolina; Ostrowski, Andrzej; Wielgus, Ireneusz; Lisowski, Wojciech; Sobczak, Janusz W; Przybylski, Marek; Pron, Adam

    2016-06-01

    It is demonstrated that ternary Cu-Fe-S nanocrystals differing in composition (from Cu-rich to Fe-rich), structure (chalcopyrite or high bornite) and size can be obtained from a mixture of CuCl, FeCl3, thiourea and oleic acid (OA) in oleylamine (OLA) using the heating up procedure. This new preparation method yields the smallest Cu-Fe-S nanocrystals ever reported to date (1.5 nm for the high bornite structure and 2.7 nm for the chalcopyrite structure). A comparative study of nanocrystals of the same composition (Cu1.6Fe1.0S2.0) but different in size (2.7 nm and 9.3 nm) revealed a pronounced quantum confinement effect, confirmed by three different techniques: UV-vis spectroscopy, cyclic voltammetry and Mössbauer spectroscopy. The optical band gap increased from 0.60 eV in the bulk material to 0.69 eV in the nanocrystals of 9.3 nm size and to 1.39 eV in nanocrystals of 2.7 nm size. The same trend was observed in the electrochemical band gaps, derived from cyclic voltammetry studies (band gaps of 0.74 eV and 1.54 eV). The quantum effect was also manifested in Mössbauer spectroscopy by an abrupt change in the spectrum from a quadrupole doublet to a Zeeman sextet below 10 K, which could be interpreted in terms of the well defined energy states in these nanoparticles, resulting from quantum confinement. The Mössbauer spectroscopic data confirmed, in addition to the results of XPS spectroscopy, the co-existence of Fe(iii) and Fe(ii) in the synthesized nanocrystals. The organic shell composition was investigated by NMR (after dissolution of the inorganic core) and IR spectroscopy. Both methods identified oleylamine (OLA) and 1-octadecene (ODE) as surfacial ligands, the latter being formed in situ via an elimination-hydrogenation reaction occurring between OLA and the nanocrystal surface.

  5. Cellulose nanocrystals: synthesis, functional properties, and applications

    PubMed Central

    George, Johnsy; Sabapathi, SN

    2015-01-01

    Cellulose nanocrystals are unique nanomaterials derived from the most abundant and almost inexhaustible natural polymer, cellulose. These nanomaterials have received significant interest due to their mechanical, optical, chemical, and rheological properties. Cellulose nanocrystals primarily obtained from naturally occurring cellulose fibers are biodegradable and renewable in nature and hence they serve as a sustainable and environmentally friendly material for most applications. These nanocrystals are basically hydrophilic in nature; however, they can be surface functionalized to meet various challenging requirements, such as the development of high-performance nanocomposites, using hydrophobic polymer matrices. Considering the ever-increasing interdisciplinary research being carried out on cellulose nanocrystals, this review aims to collate the knowledge available about the sources, chemical structure, and physical and chemical isolation procedures, as well as describes the mechanical, optical, and rheological properties, of cellulose nanocrystals. Innovative applications in diverse fields such as biomedical engineering, material sciences, electronics, catalysis, etc, wherein these cellulose nanocrystals can be used, are highlighted. PMID:26604715

  6. Intermetallic Nanocrystals: Syntheses and Catalytic Applications.

    PubMed

    Yan, Yucong; Du, Jingshan S; Gilroy, Kyle D; Yang, Deren; Xia, Younan; Zhang, Hui

    2017-02-24

    At the forefront of nanochemistry, there exists a research endeavor centered around intermetallic nanocrystals, which are unique in terms of long-range atomic ordering, well-defined stoichiometry, and controlled crystal structure. In contrast to alloy nanocrystals with no elemental ordering, it is challenging to synthesize intermetallic nanocrystals with a tight control over their size and shape. Here, recent progress in the synthesis of intermetallic nanocrystals with controllable sizes and well-defined shapes is highlighted. A simple analysis and some insights key to the selection of experimental conditions for generating intermetallic nanocrystals are presented, followed by examples to highlight the viable use of intermetallic nanocrystals as electrocatalysts or catalysts for various reactions, with a focus on the enhanced performance relative to their alloy counterparts that lack elemental ordering. Within the conclusion, perspectives on future developments in the context of synthetic control, structure-property relationships, and applications are discussed.

  7. Phase transitions and doping in semiconductor nanocrystals

    NASA Astrophysics Data System (ADS)

    Sahu, Ayaskanta

    Colloidal semiconductor nanocrystals are a promising technological material because their size-dependent optical and electronic properties can be exploited for a diverse range of applications such as light-emitting diodes, bio-labels, transistors, and solar cells. For many of these applications, electrical current needs to be transported through the devices. However, while their solution processability makes these colloidal nanocrystals attractive candidates for device applications, the bulky surfactants that render these nanocrystals dispersible in common solvents block electrical current. Thus, in order to realize the full potential of colloidal semiconductor nanocrystals in the next-generation of solid-state devices, methods must be devised to make conductive films from these nanocrystals. One way to achieve this would be to add minute amounts of foreign impurity atoms (dopants) to increase their conductivity. Electronic doping in nanocrystals is still very much in its infancy with limited understanding of the underlying mechanisms that govern the doping process. This thesis introduces an innovative synthesis of doped nanocrystals and aims at expanding the fundamental understanding of charge transport in these doped nanocrystal films. The list of semiconductor nanocrystals that can be doped is large, and if one combines that with available dopants, an even larger set of materials with interesting properties and applications can be generated. In addition to doping, another promising route to increase conductivity in nanocrystal films is to use nanocrystals with high ionic conductivities. This thesis also examines this possibility by studying new phases of mixed ionic and electronic conductors at the nanoscale. Such a versatile approach may open new pathways for interesting fundamental research, and also lay the foundation for the creation of novel materials with important applications. In addition to their size-dependence, the intentional incorporation of

  8. Tailoring nanocrystalline diamond film properties

    DOEpatents

    Gruen, Dieter M.; McCauley, Thomas G.; Zhou, Dan; Krauss, Alan R.

    2003-07-15

    A method for controlling the crystallite size and growth rate of plasma-deposited diamond films. A plasma is established at a pressure in excess of about 55 Torr with controlled concentrations of hydrogen up to about 98% by volume, of unsubstituted hydrocarbons up to about 3% by volume and an inert gas of one or more of the noble gases and nitrogen up to about 98% by volume. The volume ratio of inert gas to hydrogen is preferably maintained at greater than about 4, to deposit a diamond film on a suitable substrate. The diamond film is deposited with a predetermined crystallite size and at a predetermined growth rate.

  9. Conversion of fullerenes to diamond

    DOEpatents

    Gruen, Dieter M.

    1994-01-01

    A method of forming synthetic hydrogen defect free diamond or diamond like films on a substrate. The method involves providing vapor containing fullerene molecules with or without an inert gas, providing a device to impart energy to the fullerene molecules, fragmenting at least in part some of the fullerene molecules in the vapor or energizing the molecules to incipient fragmentation, ionizing the fullerene molecules, impinging ionized fullerene molecules on the substrate to assist in causing fullerene fragmentation to obtain a thickness of diamond on the substrate.

  10. CVD Diamond Dielectric Accelerating Structures

    SciTech Connect

    Schoessow, P.; Kanareykin, A.; Gat, R.

    2009-01-22

    The electrical and mechanical properties of diamond make it an ideal candidate material for use in dielectric accelerating structures: high RF breakdown field, extremely low dielectric losses and the highest available thermoconductive coefficient. Using chemical vapor deposition (CVD) cylindrical diamond structures have been manufactured with dimensions corresponding to fundamental TM{sub 01} mode frequencies in the GHz to THz range. Surface treatments are being developed to reduce the secondary electron emission (SEE) coefficient below unity to reduce the possibility of multipactor. The diamond CVD cylindrical waveguide technology developed here can be applied to a variety of other high frequency, large-signal applications.

  11. CVD diamond metallization and characterization

    NASA Astrophysics Data System (ADS)

    Fraimovitch, D.; Adelberd, A.; Marunko, S.; Lefeuvre, G.; Ruzin, A.

    2017-02-01

    In this study we compared three diamond substrate grades: polycrystalline, optical grade single crystal, and electronic grade single crystal for detector application. Beside the bulk type, the choice of contact material, pre-treatment, and sputtering process details have shown to alter significantly the diamond detector performance. Characterization of diamond substrate permittivity and losses indicate grade and crystallinity related, characteristic differences for frequencies in 1 kHz-1 MHz range. Substantial grade related variations were also observed in surface electrostatic characterization performed by contact potential difference (CPD) mode of an atomic force microscope. Study of conductivity variations with temperature reveal that bulk trap energy levels are also dependent on the crystal grade.

  12. Hydrothermal synthesis of Mo-doped VO2/TiO2 composite nanocrystals with enhanced thermochromic performance.

    PubMed

    Li, Dengbing; Li, Ming; Pan, Jing; Luo, Yuanyuan; Wu, Hao; Zhang, Yunxia; Li, Guanghai

    2014-05-14

    This paper reports a one-step TiO2 seed-assistant hydrothermal synthesis of Mo-doped VO2(M)/TiO2 composite nanocrystals. It was found that excess Mo doping can promote formation of the VO2(M) phase, and rutile TiO2 seed is beneficial to morphology control, size reduction, and infrared modulation of Mo-doped VO2(M) nanocrystals. The Mo-doped VO2 nanocrystals epitaxially grow on TiO2 seeds and have a quasi-spherical shape with size down to 20 nm and a nearly 35% infrared modulation near room temperature. The findings of this work demonstrate important progress in the near-room-temperature thermochromic performance of VO2(M) nanomaterials, which will find potential application in constructing VO2(M) nanocrystal-based smart window coatings.

  13. Synthesis of CulnS2, CulnSe2, and Cu(InxGa(1-x))Se2 (CIGS) nanocrystal "inks" for printable photovoltaics.

    PubMed

    Panthani, Matthew G; Akhavan, Vahid; Goodfellow, Brian; Schmidtke, Johanna P; Dunn, Lawrence; Dodabalapur, Ananth; Barbara, Paul F; Korgel, Brian A

    2008-12-10

    Chalcopyrite copper indium sulfide (CuInS2) and copper indium gallium selenide (Cu(InxGa(1-x))-Se2; CIGS) nanocrystals ranging from approximately 5 to approximately 25 nm in diameter were synthesized by arrested precipitation in solution. The In/Ga ratio in the CIGS nanocrystals could be controlled by varying the In/Ga reactant ratio in the reaction, and the optical properties of the CulnS2 and CIGS nanocrystals correspond to those of the respective bulk materials. Using methods developed to produce uniform, crack-free micrometer-thick films, CulnSe2 nanocrystals were tested in prototype photovoltaic devices. As a proof-of-concept, the nanocrystal-based devices exhibited a reproducible photovoltaic response.

  14. Fabrication of platy apatite nanocrystals loaded with TiO2 nanoparticles by two-step emulsion method and their photocatalytic activity.

    PubMed

    Iwasaki, Mitsunobu; Miyamoto, Yuki; Ito, Seishiro; Furuzono, Tsutomu; Park, Won-Kyu

    2008-10-15

    Nanometer-sized TiO(2) island structure on the platy hydroxyapatite nanocrystals (HAp) has been accomplished by two-step emulsion process. At the first step, platy HAp nanocrystals, of which size was in the range of 70-200 nm after heat-treatment at 1078 K for 1 h, were prepared using the W/O emulsion system. Before the second step, HAp nanocrystals were immersed in NaH(2)PO(4) solution for the formation of hydroxyl group on their surface. In the following, titanium tetraisopropoxide reacted with the hydroxyl group of HAp surface to form TiO(2) nanoparticles on the surface of HAp nanocrystals, which were dispersed in the micrometer-sized methanol droplets of polyethylene cetylether-cyclohexane mixture (methanol/oil emulsion). The resulting hydroxyapatite nanocrystals loaded with TiO(2) nanoparticles showed the high photocatalytic activity comparing to the commercial TiO(2) catalyst.

  15. Nanoscale fluorescence lifetime imaging of an optical antenna with a single diamond NV center.

    PubMed

    Beams, Ryan; Smith, Dallas; Johnson, Timothy W; Oh, Sang-Hyun; Novotny, Lukas; Vamivakas, A Nick

    2013-08-14

    Solid-state quantum emitters, such as artificially engineered quantum dots or naturally occurring defects in solids, are being investigated for applications ranging from quantum information science and optoelectronics to biomedical imaging. Recently, these same systems have also been studied from the perspective of nanoscale metrology. In this letter, we study the near-field optical properties of a diamond nanocrystal hosting a single nitrogen vacancy center. We find that the nitrogen vacancy center is a sensitive probe of the surrounding electromagnetic mode structure. We exploit this sensitivity to demonstrate nanoscale fluorescence lifetime imaging microscopy (FLIM) with a single nitrogen vacancy center by imaging the local density of states of an optical antenna.

  16. Discrete plasticity in sub-10-nm-sized gold crystals

    PubMed Central

    Zheng, He; Cao, Ajing; Weinberger, Christopher R.; Huang, Jian Yu; Du, Kui; Wang, Jianbo; Ma, Yanyun; Xia, Younan; Mao, Scott X.

    2010-01-01

    Although deformation processes in submicron-sized metallic crystals are well documented, the direct observation of deformation mechanisms in crystals with dimensions below the sub-10-nm range is currently lacking. Here, through in situ high-resolution transmission electron microscopy (HRTEM) observations, we show that (1) in sharp contrast to what happens in bulk materials, in which plasticity is mediated by dislocation emission from Frank-Read sources and multiplication, partial dislocations emitted from free surfaces dominate the deformation of gold (Au) nanocrystals; (2) the crystallographic orientation (Schmid factor) is not the only factor in determining the deformation mechanism of nanometre-sized Au; and (3) the Au nanocrystal exhibits a phase transformation from a face-centered cubic to a body-centered tetragonal structure after failure. These findings provide direct experimental evidence for the vast amount of theoretical modelling on the deformation mechanisms of nanomaterials that have appeared in recent years. PMID:21266994

  17. Cu nanocrystal growth on peptide nanotubes by biomineralization: Size control of Cu nanocrystals by tuning peptide conformation

    NASA Astrophysics Data System (ADS)

    Banerjee, Ipsita A.; Yu, Lingtao; Matsui, Hiroshi

    2003-12-01

    With recent interest in seeking new biologically inspired device-fabrication methods in nanotechnology, a new biological approach was examined to fabricate Cu nanotubes by using sequenced histidine-rich peptide nanotubes as templates. The sequenced histidine-rich peptide molecules were assembled as nanotubes, and the biological recognition of the specific sequence toward Cu lead to efficient Cu coating on the nanotubes. Cu nanocrystals were uniformly coated on the histidine-incorporated nanotubes with high packing density. In addition, the diameter of Cu nanocrystal was controlled between 10 and 30 nm on the nanotube by controlling the conformation of histidine-rich peptide by means of pH changes. Those nanotubes showed significant change in electronic structure by varying the nanocrystal diameter; therefore, this system may be developed to a conductivity-tunable building block for microelectronics and biological sensors. This simple biomineralization method can be applied to fabricate various metallic and semiconductor nanotubes with peptides whose sequences are known to mineralize specific ions.

  18. Synthesis, Optical and Structural Properties of Copper Sulfide Nanocrystals from Single Molecule Precursors

    PubMed Central

    Ajibade, Peter A.; Botha, Nandipha L.

    2017-01-01

    We report the synthesis and structural studies of copper sulfide nanocrystals from copper (II) dithiocarbamate single molecule precursors. The precursors were thermolysed in hexadecylamine (HDA) to prepare HDA-capped CuS nanocrystals. The optical properties of the nanocrystals studied using UV–visible and photoluminescence spectroscopy showed absorption band edges at 287 nm that are blue shifted, and the photoluminescence spectra show emission curves that are red-shifted with respect to the absorption band edges. These shifts are as a result of the small crystallite sizes of the nanoparticles leading to quantum size effects. The structural studies were carried out using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and atomic force microscopy. The XRD patterns indicates that the CuS nanocrystals are in hexagonal covellite crystalline phases with estimated particles sizes of 17.3–18.6 nm. The TEM images showed particles with almost spherical or rod shapes, with average crystallite sizes of 3–9.8 nm. SEM images showed morphology with ball-like microspheres on the surfaces, and EDS spectra confirmed the presence of CuS nanoparticles. PMID:28336865

  19. In2O3 nanocrystal memory with the barrier engineered tunnel layer.

    PubMed

    Lee, Dong Uk; Kim, Seon Pil; Han, Dong Seok; Kim, Eun Kyu; Park, Goon-Ho; Cho, Won-Ju; Kim, Young-Ho

    2011-01-01

    In2O3 nanocrystal memories with barrier-engineered tunnel layers were fabricated on a p-type Si substrate. The structure and thickness of the barrier-engineered tunnel layers were SiO2/Si3N4/SiO2 (ONO) and 2/2/3 nm, respectively. The equivalent oxide thickness of the ONO tunnel layers was 5.64 nm. The average size and density of the In2O3 nanocrystals after the reaction between BPDA-PDA polyimide and the In thin film were about 8 nm and 4 x 10(11) cm(-2), respectively. The electrons were charged from the channel of the memory device to the quantum well of the In2O3 nanocrystal through the ONO tunnel layer via Fowler-Nordheim tunneling. The memory window was about 1.4 V when the program and erase conditions of the In2O3 nanocrystal memory device were 12 V for 1 s and -15 V for 200 ms.

  20. Synthesis and stabilization of selenium nanoparticles on cellulose nanocrystal

    SciTech Connect

    Shin, Yongsoon; Blackwood, Jade M.; Bae, In-Tae; Arey, Bruce W.; Exarhos, Gregory J.

    2007-08-01

    Selenium nanoparticles of 10-20 nm in diameter have been prepared using cellulose nanocrystal (CNXL) as a reducing and structure-directing agent under hydrothermal conditions. Na2SeO3 was reduced to form elemental selenium nanoparticles under hydrothermal conditions. During the hydrothermal process (120-160 oC), CNXL rods were mainly maintained and selenium nanoparticles were interfacially bound to CNXL surface. The reaction temperature affects the sizes of interfacially bound selenium nanoparticles. X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), and transmission electron microscope (TEM) were employed to characterize interfacially bound selenium nanoparticles on CNXL surface.

  1. Fabrication of amorphous diamond films

    DOEpatents

    Falabella, S.

    1995-12-12

    Amorphous diamond films having a significant reduction in intrinsic stress are prepared by biasing a substrate to be coated and depositing carbon ions thereon under controlled temperature conditions. 1 fig.

  2. Amorphous-diamond electron emitter

    DOEpatents

    Falabella, Steven

    2001-01-01

    An electron emitter comprising a textured silicon wafer overcoated with a thin (200 .ANG.) layer of nitrogen-doped, amorphous-diamond (a:D-N), which lowers the field below 20 volts/micrometer have been demonstrated using this emitter compared to uncoated or diamond coated emitters wherein the emission is at fields of nearly 60 volts/micrometer. The silicon/nitrogen-doped, amorphous-diamond (Si/a:D-N) emitter may be produced by overcoating a textured silicon wafer with amorphous-diamond (a:D) in a nitrogen atmosphere using a filtered cathodic-arc system. The enhanced performance of the Si/a:D-N emitter lowers the voltages required to the point where field-emission displays are practical. Thus, this emitter can be used, for example, in flat-panel emission displays (FEDs), and cold-cathode vacuum electronics.

  3. Method of dehalogenation using diamonds

    DOEpatents

    Farcasiu, Malvina; Kaufman, Phillip B.; Ladner, Edward P.; Anderson, Richard R.

    2000-01-01

    A method for preparing olefins and halogenated olefins is provided comprising contacting halogenated compounds with diamonds for a sufficient time and at a sufficient temperature to convert the halogenated compounds to olefins and halogenated olefins via elimination reactions.

  4. Superheating and supercooling of Ge nanocrystals embedded inSiO2

    SciTech Connect

    Xu, Q.; Sharp, I.D.; Yuan, C.W.; Yi, D.O.; Liao, C.Y.; Glaeser,A.M.; Minor, A.M.; Beeman, J.W.; Ridgway, M.C.; Kluth, P.; Ager III,J.W.; Chrzan, D.C.; Haller, E.E.

    2006-08-21

    Free-standing nanocrystals exhibit a size-dependant thermodynamic melting point reduction relative to the bulk melting point that is governed by the surface free energy. The presence of an encapsulating matrix, however, alters the interface free energy of nanocrystals and their thermodynamic melting point can either increase or decrease relative to bulk. Furthermore, kinetic contributions can significantly alter the melting behaviors of embedded nanoscale materials. To study the effect of an encapsulating matrix on the melting behavior of nanocrystals, we performed in situ electron diffraction measurements on Ge nanocrystals embedded in a silicon dioxide matrix. Ge nanocrystals were formed by multi-energy ion implantation into a 500 nm thick silica thin film on a silicon substrate followed by thermal annealing at 900 C for 1 h. We present results demonstrating that Ge nanocrystals embedded in SiO{sub 2} exhibit a 470 K melting/solidification hysteresis that is approximately symmetric about the bulk melting point. This unique behavior, which is thought to be impossible for bulk materials, is well described using a classical thermodynamic model that predicts both kinetic supercooling and kinetic superheating. The presence of the silica matrix suppresses surface pre-melting of nanocrystals. Therefore, heterogeneous nucleation of both the liquid phase and the solid phase are required during the heating and cooling cycle. The magnitude of melting hysteresis is governed primarily by the value of the liquid Ge/solid Ge interface free energy, whereas the relative values of the solid Ge/matrix and liquid Ge/matrix interface free energies govern the position of the hysteresis loop in absolute temperature.

  5. Analytical modeling of localized surface plasmon resonance in heterostructure copper sulfide nanocrystals

    SciTech Connect

    Caldwell, Andrew H.; Ha, Don-Hyung; Robinson, Richard D.; Ding, Xiaoyue

    2014-10-28

    Localized surface plasmon resonance (LSPR) in semiconductor nanocrystals is a relatively new field of investigation that promises greater tunability of plasmonic properties compared to metal nanoparticles. A novel process by which the LSPR in semiconductor nanocrystals can be altered is through heterostructure formation arising from solution-based cation exchange. Herein, we describe the development of an analytical model of LSPR in heterostructure copper sulfide-zinc sulfide nanocrystals synthesized via a cation exchange reaction between copper sulfide (Cu{sub 1.81}S) nanocrystals and Zn ions. The cation exchange reaction produces dual-interface, heterostructure nanocrystals in which the geometry of the copper sulfide phase can be tuned from a sphere to a thin disk separating symmetrically-grown sulfide (ZnS) grains. Drude model electronic conduction and Mie-Gans theory are applied to describe how the LSPR wavelength changes during cation exchange, taking into account the morphology evolution and changes to the local permittivity. The results of the modeling indicate that the presence of the ZnS grains has a significant effect on the out-of-plane LSPR mode. By comparing the results of the model to previous studies on solid-solid phase transformations of copper sulfide in these nanocrystals during cation exchange, we show that the carrier concentration is independent of the copper vacancy concentration dictated by its atomic phase. The evolution of the effective carrier concentration calculated from the model suggests that the out-of-plane resonance mode is dominant. The classical model was compared to a simplified quantum mechanical model which suggested that quantum mechanical effects become significant when the characteristic size is less than ∼8 nm. Overall, we find that the analytical models are not accurate for these heterostructured semiconductor nanocrystals, indicating the need for new model development for this emerging field.

  6. Shape and size controlled synthesis of uniform iron oxide nanocrystals through new non-hydrolytic routes

    NASA Astrophysics Data System (ADS)

    Li, Wenlu; Lee, Seung Soo; Wu, Jiewei; Hinton, Carl H.; Fortner, John D.

    2016-08-01

    New, non-hydrolytic routes to synthesize highly crystalline iron oxide nanocrystals (8-40 nm, magnetite) are described in this report whereby particle size and morphology were precisely controlled through reactant (precursor, e.g. (FeO(OH)) ratios, co-surfactant and organic additive, and/or reaction time. Particle size, with high monodispersivity (<10%), is demonstrated to be a function of precursor concentrations and through the addition of different cosurfactants and/or additives, cubic, octahedral, potato-like, and flower-like iron oxide nanocrystals can be reproducibly synthesized through simple one-pot thermal decomposition methods. High resolution transmission electron microscope, x-ray diffraction, and superconducting quantum interference device were used to characterize the size, structure and magnetic properties of the resulting nanocrystals. For aqueous applications, materials synthesized/purified in organic solvents are broadly water dispersible through a variety of phase (aqueous) transfer method(s).

  7. Direct Observation of Room-Temperature Polar Ordering in Colloidal GeTe Nanocrystals

    SciTech Connect

    Polking, Mark J.; Zheng, Haimei; Urban, Jeffrey J.; Milliron, Delia J.; Chan, Emory; Caldwell, Marissa A.; Raoux, Simone; Kisielowski, Christian F.; Ager III, Joel W.; Ramesh, Ramamoorthy; Alivisatos, A.P.

    2009-12-07

    Ferroelectrics and other materials that exhibit spontaneous polar ordering have demonstrated immense promise for applications ranging from non-volatile memories to microelectromechanical systems. However, experimental evidence of polar ordering and effective synthetic strategies for accessing these materials are lacking for low-dimensional nanomaterials. Here, we demonstrate the synthesis of size-controlled nanocrystals of the polar material germanium telluride (GeTe) using colloidal chemistry and provide the first direct evidence of room-temperature polar ordering in nanocrystals less than 5 nm in size using aberration-corrected transmission electron microscopy. Synchrotron x-ray diffraction and Raman studies demonstrate a sizeable polar distortion and a reversible size-dependent polar phase transition in these nanocrystals. The stability of polar ordering in solution-processible nanomaterials suggests an economical avenue to Tbit/in2-density non-volatile memory devices and other applications.

  8. Luminescence enhancement of nanocrystal quantum wells by bandgap and strain engineering

    NASA Astrophysics Data System (ADS)

    Cao, Xian-An; Lu, Yifei

    2015-01-01

    CdSe-based nanocrystal quantum wells (QWs) were synthesized around CdS nanocrystal quantum dots and were bandgap- and strain-engineered to achieve high-efficiency short-wavelength luminescence. Tuning the CdSe QW width in the range of 1.05 to 1.58 nm has led to blue-green light emission, whose quantum yield was improved up to 48% through strain compensation by an optimized ZnS outer shell. The luminescence spectrum can be modified by adding a ZnS inner barrier layer to block charge and exciton transfer between the QW and CdS core. Strain management by adjusting the well and barrier thickness has proven critical in such a complex multilayer quantum system for obtaining high-quality nanocrystals and light emission.

  9. Formation of Organic Molecular Nanocrystals under Rigid Confinement with Analysis by Solid State NMR.

    PubMed

    Yang, X; Ong, T C; Michaelis, V K; Heng, S; Huang, J; Griffin, R G; Myerson, A S

    2014-10-21

    Crystallization in rigid confinement is a promising method to obtain organic molecular nanocrystals. However, the crystallization behavior and the related characterization methods are not well studied. Here we present a systematic study of the nucleation of organic molecular nanocrystals in rigid pores. Four different compounds were studied, ibuprofen, fenofibrate, griseofulvin, and indomethacin, which range from simple to complex molecules. Solid-state Nuclear Magnetic Resonance (NMR) was employed to analyse the structure of these compounds inside pores which are difficult to characterize by other analytical methods. We successfully demonstrated the production of nano-crystalline ibuprofen, fenofibrate and griseofulvin in porous silica particles with ~ 40 nm pores. These nanocrystals showed significant enhancement in dissolution rates. These results help advance the fundamental understanding of nucleation under rigid confinement and may lead to potential applications in developing new formulations in the pharmaceutical industry.

  10. Silicon monoxide - a convenient precursor for large scale synthesis of near infrared emitting monodisperse silicon nanocrystals

    NASA Astrophysics Data System (ADS)

    Sun, Wei; Qian, Chenxi; Cui, Xiao Sherri; Wang, Liwei; Wei, Muan; Casillas, Gilberto; Helmy, Amr S.; Ozin, Geoffrey A.

    2016-02-01

    While silicon nanocrystals (ncSi) embedded in silicon dioxide thin films have been intensively studied in physics, the potential of batch synthesis of silicon nanocrystals from the solid-state disproportionation of SiO powder has not drawn much attention in chemistry. Herein we describe some remarkable effects observed in the diffraction, microscopy and spectroscopy of SiO powder upon thermal processing in the temperature range 850-1100 °C. Quantum confinement effects and structural changes of the material related to the size of the silicon nanocrystals nucleated and grown in this way were established by Photoluminescence (PL), Raman, FTIR and UV-Visible spectroscopy, PXRD and STEM, pinpointing that the most significant disproportionation transformations happened in the temperature range between 900 and 950 °C. With this know-how a high yield synthesis was developed that produced polydispersions of decyl-capped, hexane-soluble silicon nanocrystals predominantly with near infrared (NIR) PL. Using size-selective precipitation, these polydispersions were separated into monodisperse fractions, which allowed their PL absolute quantum yield (AQY) to be studied as a function of silicon nanocrystal size. This investigation yielded volcano-shaped plots for the AQY confirming the most efficient PL wavelength for ncSi to be located at around 820-830 nm, which corresponded to a size of 3.5-4.0 nm. This work provides opportunities for applications of size-selected near infrared emitting silicon nanocrystals in biomedical imaging and photothermal therapy.While silicon nanocrystals (ncSi) embedded in silicon dioxide thin films have been intensively studied in physics, the potential of batch synthesis of silicon nanocrystals from the solid-state disproportionation of SiO powder has not drawn much attention in chemistry. Herein we describe some remarkable effects observed in the diffraction, microscopy and spectroscopy of SiO powder upon thermal processing in the temperature

  11. Formation of Organic Molecular Nanocrystals under Rigid Confinement with Analysis by Solid State NMR

    PubMed Central

    Yang, X.; Ong, T. C.; Michaelis, V. K.; Heng, S.; Huang, J.; Griffin, R. G.; Myerson, A. S.

    2014-01-01

    Crystallization in rigid confinement is a promising method to obtain organic molecular nanocrystals. However, the crystallization behavior and the related characterization methods are not well studied. Here we present a systematic study of the nucleation of organic molecular nanocrystals in rigid pores. Four different compounds were studied, ibuprofen, fenofibrate, griseofulvin, and indomethacin, which range from simple to complex molecules. Solid-state Nuclear Magnetic Resonance (NMR) was employed to analyse the structure of these compounds inside pores which are difficult to characterize by other analytical methods. We successfully demonstrated the production of nano-crystalline ibuprofen, fenofibrate and griseofulvin in porous silica particles with ~ 40 nm pores. These nanocrystals showed significant enhancement in dissolution rates. These results help advance the fundamental understanding of nucleation under rigid confinement and may lead to potential applications in developing new formulations in the pharmaceutical industry. PMID:25258590

  12. Development of Microspheres Covered with Hydroxyapatite Nanocrystals as Cell Scaffold for Angiogenesis

    NASA Astrophysics Data System (ADS)

    Iwamoto, Takashi; Terada, Takahiro; Kogai, Yasumichi; Okada, Masahiro; Fujii, Syuji; Furuzono, Tsutomu

    2012-06-01

    We prepared poly(L-lactide-co-glycolide) cell scaffolds coated with hydroxyapatite (HAp) nanocrystals with 50-100 nm in diameter via the Pickering emulsion method. Our cell scaffolds were composed of biodegradable polymers and HAp nanocrystals as a core and shell, respectively. The scaffolds were spherical but displayed uneven shapes when altering a shear speed of homogenization during syntheses. The surface coverage of HAp nanocrystals was examined because the HAp-coating ratio for the scaffolds was an important factor as cell scaffolds in order to enhance cell adhesion. On the basis of scanning electron microscopy observations and thermogravimetric analyses, it was found that the cell scaffolds showed distorted morphologies, and the HAp-coating ratio decreased with increasing the shear speed in the synthesis because shear stress influenced shapes of the scaffolds.

  13. Shape and size controlled synthesis of uniform iron oxide nanocrystals through new non-hydrolytic routes.

    PubMed

    Li, Wenlu; Lee, Seung Soo; Wu, Jiewei; Hinton, Carl H; Fortner, John D

    2016-08-12

    New, non-hydrolytic routes to synthesize highly crystalline iron oxide nanocrystals (8-40 nm, magnetite) are described in this report whereby particle size and morphology were precisely controlled through reactant (precursor, e.g. (FeO(OH)) ratios, co-surfactant and organic additive, and/or reaction time. Particle size, with high monodispersivity (<10%), is demonstrated to be a function of precursor concentrations and through the addition of different cosurfactants and/or additives, cubic, octahedral, potato-like, and flower-like iron oxide nanocrystals can be reproducibly synthesized through simple one-pot thermal decomposition methods. High resolution transmission electron microscope, x-ray diffraction, and superconducting quantum interference device were used to characterize the size, structure and magnetic properties of the resulting nanocrystals. For aqueous applications, materials synthesized/purified in organic solvents are broadly water dispersible through a variety of phase (aqueous) transfer method(s).

  14. Optical and Structural Properties of Silicon with Ion-Beam Synthesized InSb Nanocrystals

    NASA Astrophysics Data System (ADS)

    Komarov, F. F.; Romanov, I. A.; Vlasukova, L. A.; Milchanin, O. V.; Parkhomenko, I. N.; Kovaleva, T. B.; Korolik, O. V.; Mudryi, A. V.; Wendler, E.

    2017-01-01

    Transmission electron microscopy (TEM), Raman scattering (RS), and photoluminescence (PL) techniques are used to study the structure, phase composition, and radiative properties of silicon with implanted InSb nanocrystals produced by implanting Sb+ and In+ ions with energies of 350 keV and fluences of 3.5·1016 cm-2 followed by heat treatment at 1100°C for 3, 10, and 60 min. The TEM and RS data confirm the formation of InSb nanocrystals with sizes ranging from 2 to 50 nm in the implanted and annealed samples. A broad band in the 0.8-1.05 eV range is detected in low-temperature (4.2 K) PL spectra of the annealed samples. The possible mechanisms for the luminescence in this range are luminescence of InSb nanocrystals and radiative recombination between the conduction band of silicon and an In acceptor.

  15. Lasing from ZnO Nanocrystals in ZnO-ZnS Microbelts

    NASA Astrophysics Data System (ADS)

    Nghia, N. V.; Dung, N. D.; Huy, P. T.; Nguyen, D. H.

    2017-03-01

    We present an investigation of the morphology, structure, composition, chemical state and optical properties of ZnO-ZnS microbelts grown by the thermal evaporation method. It is found that the ZnO-ZnS microbelts are composed of ZnS and ZnO nanocrystals with high crystalline quality. Under optical pumping from a Nd:YAG laser at 266 nm, stimulated lasing emissions from ZnO nanocrystals are observed with a threshold as low as 10 mJ/cm2. The low lasing threshold of ZnO nanocrystals is interpreted as a result of the modification of ZnO surfaces with a ZnS layer that efficiently passivates the surface defects and reduces nonradiative Auger recombination.

  16. Physical preparation and optical properties of CuSbS2 nanocrystals by mechanical alloying process

    NASA Astrophysics Data System (ADS)

    Zhang, Huihui; Xu, Qishu; Tan, Guolong

    2016-09-01

    CuSbS2 nanocrystals have been synthesized through mechanical alloying Cu, Sb and S elemental powders for 40 hs. The optical spectrum of as-milled CuSbS2 nano-powders demonstrates a direct gap of 1.35 eV and an indirect gap of 0.36 eV, which are similar to that of silicon and reveals the evidence for the indirect semiconductor characterization of CuSbS2. Afterwards, CuSbS2 nanocrystals were capped with trioctylphosphine oxide/trioctylphosphine/pyridine (TOPO/TOP). There appear four sharp absorption peaks within the region of 315 to 355 nm for the dispersion solution containing the capped nanocrystals. The multiple peaks are proposed to be originating from the energy level splitting of 1S electronic state into four discrete sub-levels, where electrons were excited into the conduction band and thus four exciton absorption peaks were produced.

  17. Photorefractivity in a polymeric composite photosensitized with NiS nanocrystals

    NASA Astrophysics Data System (ADS)

    Fears, Tyler M.; Anderson, Charles; Winiarz, Jeffrey G.

    2008-10-01

    The photorefractive performance of a polymeric composite photosensitized through the inclusion of NiS nanocrystals is described. The nanocrystals were characterized using visible-absorption spectroscopy, energy-dispersive x-ray spectroscopy, and transmission electron microscopy. We further demonstrate the ability to enhance various aspects of the composite's photorefractive performance by performing ligand exchange on the nanocrystals prior to their incorporation into the polymer composite. This procedure resulted in a lowering of the overmodulation voltage from ˜70to˜50V/μm without affecting the maximum diffraction efficiency of ˜40%. An increase in the two-beam-coupling gain coefficient was similarly observed, increasing from 38to79cm-1. The photoconductivities were used in determining the overall quantum efficiencies associated with the photorefractive devices. All experiments were conducted at 633nm and the data represent a significant improvement in the photorefractive performance of inorganic-organic hybrid photorefractive materials.

  18. Cubic to tetragonal phase transition of Tm{sup 3+} doped nanocrystals in oxyfluoride glass ceramics

    SciTech Connect

    Li, Yiming; Fu, Yuting; Shi, Yahui; Zhang, Xiaoyu; Yu, Hua E-mail: yuhua@nankai.edu.cn; Zhao, Lijuan E-mail: yuhua@nankai.edu.cn

    2016-02-15

    Tm{sup 3+} ions doped β-PbF{sub 2} nanocrystals in oxyfluoride glass ceramics with different doping concentrations and thermal temperatures are prepared by a traditional melt-quenching and thermal treatment method to investigate the structure and the phase transition of Tm{sup 3+} doped nanocrystals. The structures are characterized by X-ray diffraction Rietveld analysis and confirmed with numerical simulation. The phase transitions are proved further by the emission spectra. Both of the doping concentration and thermal temperature can induce an O{sub h} to D{sub 4h} site symmetry distortion and a cubic to tetragonal phase transition. The luminescence of Tm{sup 3+} doped nanocrystals at 800 nm was modulated by the phase transition of the surrounding crystal field.

  19. Charge transport across high surface area metal/diamond nanostructured composites.

    PubMed

    Plana, D; Humphrey, J J L; Bradley, K A; Celorrio, V; Fermín, D J

    2013-04-24

    High surface area composites featuring metal nanostructures and diamond particles have generated a lot of interest in the fields of heterogeneous catalysis, electrocatalysis, and sensors. Diamond surfaces provide a chemically robust framework for active nanostructures in comparison with sp(2) carbon supports. The present paper investigates the charge transport properties of high surface area films of high-pressure, high-temperature diamond particles in the presence and absence of metal nanostructures, employing electrochemical field-effect transistors. Oxygen- and hydrogen-terminated surfaces were generated on 500 nm diamond powders. Homogeneously distributed metal nanostructures, with metal volume fractions between ca. 5 and 20%, were either nucleated at the diamond particles by impregnation or incorporated from colloidal solution. Electrochemical field-effect transistor measurements, employing interdigitated electrodes, allowed the determination of composite conductivity as a function of electrode potential, as well as in air. In the absence of metal nanostructures, the lateral conductivity of the diamond assemblies in air is increased by over one order of magnitude upon hydrogenation of the particle surface. This observation is consistent with studies at diamond single crystals, although the somewhat modest change in conductivity suggests that charge transport is not only determined by the intrinsic surface conductivity of individual diamond particles but also by particle-to-particle charge transfer. Interestingly, the latter contribution effectively controls the assembly conductivity in the presence of an electrolyte solution as the difference between hydrogenated and oxygenated particles vanishes. The conductivity in the presence of metal nanoparticles is mainly determined by the metal volume fraction, while diamond surface termination and the presence of electrolyte solutions exert only minor effects. The experimental trends are discussed in terms of the

  20. Fabrication and characterization of boron-doped nanocrystalline diamond-coated MEMS probes

    NASA Astrophysics Data System (ADS)

    Bogdanowicz, Robert; Sobaszek, Michał; Ficek, Mateusz; Kopiec, Daniel; Moczała, Magdalena; Orłowska, Karolina; Sawczak, Mirosław; Gotszalk, Teodor

    2016-04-01

    Fabrication processes of thin boron-doped nanocrystalline diamond (B-NCD) films on silicon-based micro- and nano-electromechanical structures have been investigated. B-NCD films were deposited using microwave plasma assisted chemical vapour deposition method. The variation in B-NCD morphology, structure and optical parameters was particularly investigated. The use of truncated cone-shaped substrate holder enabled to grow thin fully encapsulated nanocrystalline diamond film with a thickness of approx. 60 nm and RMS roughness of 17 nm. Raman spectra present the typical boron-doped nanocrystalline diamond line recorded at 1148 cm-1. Moreover, the change in mechanical parameters of silicon cantilevers over-coated with boron-doped diamond films was investigated with laser vibrometer. The increase of resonance to frequency of over-coated cantilever is attributed to the change in spring constant caused by B-NCD coating. Topography and electrical parameters of boron-doped diamond films were investigated by tapping mode AFM and electrical mode of AFM-Kelvin probe force microscopy (KPFM). The crystallite-grain size was recorded at 153 and 238 nm for boron-doped film and undoped, respectively. Based on the contact potential difference data from the KPFM measurements, the work function of diamond layers was estimated. For the undoped diamond films, average CPD of 650 mV and for boron-doped layer 155 mV were achieved. Based on CPD values, the values of work functions were calculated as 4.65 and 5.15 eV for doped and undoped diamond film, respectively. Boron doping increases the carrier density and the conductivity of the material and, consequently, the Fermi level.

  1. Quantitative tunneling spectroscopy of nanocrystals

    SciTech Connect

    First, Phillip N; Whetten, Robert L; Schaaff, T Gregory

    2007-05-25

    The proposed goals of this collaborative work were to systematically characterize the electronic structure and dynamics of 3-dimensional metal and semiconducting nanocrystals using scanning tunneling microscopy/spectroscopy (STM/STS) and ballistic electron emission spectroscopy (BEES). This report describes progress in the spectroscopic work and in the development of methods for creating and characterizing gold nanocrystals. During the grant period, substantial effort also was devoted to the development of epitaxial graphene (EG), a very promising materials system with outstanding potential for nanometer-scale ballistic and coherent devices ("graphene" refers to one atomic layer of graphitic, sp2 -bonded carbon atoms [or more loosely, few layers]). Funding from this DOE grant was critical for the initial development of epitaxial graphene for nanoelectronics

  2. Lead sulphide nanocrystal photodetector technologies

    NASA Astrophysics Data System (ADS)

    Saran, Rinku; Curry, Richard J.

    2016-02-01

    Light detection is the underlying principle of many optoelectronic systems. For decades, semiconductors including silicon carbide, silicon, indium gallium arsenide and germanium have dominated the photodetector industry. They can show excellent photosensitivity but are limited by one or more aspects, such as high production cost, high-temperature processing, flexible substrate incompatibility, limited spectral range or a requirement for cryogenic cooling for efficient operation. Recently lead sulphide (PbS) nanocrystals have emerged as one of the most promising new materials for photodetector fabrication. They offer several advantages including low-cost manufacturing, solution processability, size-tunable spectral sensitivity and flexible substrate compatibility, and they have achieved figures of merit outperforming conventional photodetectors. We review the underlying concepts, breakthroughs and remaining challenges in photodetector technologies based on PbS nanocrystals.

  3. Ultra-thick, low-stress nanostructured diamond films

    SciTech Connect

    Kucheyev, S O; Biener, J; Tringe, J W; Wang, Y M

    2005-01-13

    We describe a hot-filament chemical vapor deposition process for growing freestanding nanostructured diamond films, {approx}80 {micro}m thick, with residual tensile stress levels {le} 90 MPa. We characterize the film microstructure, mechanical properties, chemical bond distribution, and elemental composition. Results show that our films are nanostructured with columnar grain diameters of {le} 150 nm and a highly variable grain length along the growth direction of {approx}50-1500 nm. These films have a rms surface roughness of {le} 200 nm for a 300 x 400 {micro}m{sup 2} scan, which is about one order of magnitude lower than the roughness of typical microcrystalline diamond films of comparable thickness. Soft x-ray absorption near-edge structure (XANES) spectroscopy indicates a large percentage of sp{sup 3} bonding in the films,consistent with a high hardness of 66 GPa. Nanoindentation and XANES results are also consistent with a high phase and elemental purity of the films, directly measured by x-ray and electron diffraction, Rutherford backscattering spectrometry, and elastic recoil detection analysis. Cross-sectional transmission electron microscopy reveals a large density of planar defects within the grains, suggesting a high rate of secondary nucleation during film growth. These films represent a new class of smooth, ultra-thick nanostructured diamond.

  4. The Surface Chemistry of Metal Chalcogenide Nanocrystals

    NASA Astrophysics Data System (ADS)

    Anderson, Nicholas Charles

    The surface chemistry of metal chalcogenide nanocrystals is explored through several interrelated analytical investigations. After a brief discussion of the nanocrystal history and applications, molecular orbital theory is used to describe the electronic properties of semiconductors, and how these materials behave on the nanoscale. Quantum confinement plays a major role in dictating the optical properties of metal chalcogenide nanocrystals, however surface states also have an equally significant contribution to the electronic properties of nanocrystals due to the high surface area to volume ratio of nanoscale semiconductors. Controlling surface chemistry is essential to functionalizing these materials for biological imaging and photovoltaic device applications. To better understand the surface chemistry of semiconducting nanocrystals, three competing surface chemistry models are presented: 1.) The TOPO model, 2.) the Non-stoichiometric model, and 3.) the Neutral Fragment model. Both the non-stoichiometric and neutral fragment models accurately describe the behavior of metal chalcogenide nanocrystals. These models rely on the covalent bond classification system, which divides ligands into three classes: 1.) X-type, 1-electron donating ligands that balance charge with excess metal at the nanocrystal surface, 2.) L-type, 2-electron donors that bind metal sites, and 3.) Z-type, 2-electron acceptors that bind chalcogenide sites. Each of these ligand classes is explored in detail to better understand the surface chemistry of metal chalcogenide nanocrystals. First, chloride-terminated, tri-n-butylphosphine (Bu 3P) bound CdSe nanocrystals were prepared by cleaving carboxylate ligands from CdSe nanocrystals with chlorotrimethylsilane in Bu3P solution. 1H and 31P{1H} nuclear magnetic resonance spectra of the isolated nanocrystals allowed assignment of distinct signals from several free and bound species, including surface-bound Bu3P and [Bu3P-H]+[Cl]- ligands as well as a Bu

  5. Plasmonic resonators for enhanced diamond NV-center single photon sources.

    PubMed

    Bulu, Irfan; Babinec, Thomas; Hausmann, Birgit; Choy, Jennifer T; Loncar, Marko

    2011-03-14

    We propose a novel source of non-classical light consisting of plasmonic aperture with single-crystal diamond containing a single Nitrogen-Vacancy (NV) color center. Theoretical calculations of optimal structures show that these devices can simultaneously enhance optical pumping by a factor of 7, spontaneous emission rates by Fp~50 (Purcell factor), and offer collection efficiencies up to 40%. These excitation and collection enhancements occur over a broad range of wavelengths (~30 nm), and are independently tunable with device geometry, across the excitation (~530 nm) and emission (~600-800 nm) spectrum of the NV center. Implementing this system with top-down techniques in bulk diamond crystals will provide a scalable architecture for a myriad of diamond NV center applications.

  6. Nearly Monodisperse Insulator Cs4PbX6 (X = Cl, Br, I) Nanocrystals, Their Mixed Halide Compositions, and Their Transformation into CsPbX3 Nanocrystals.

    PubMed

    Akkerman, Quinten A; Park, Sungwook; Radicchi, Eros; Nunzi, Francesca; Mosconi, Edoardo; De Angelis, Filippo; Brescia, Rosaria; Rastogi, Prachi; Prato, Mirko; Manna, Liberato

    2017-03-08

    We have developed a colloidal synthesis of nearly monodisperse nanocrystals of pure Cs4PbX6 (X = Cl, Br, I) and their mixed halide compositions with sizes ranging from 9 to 37 nm. The optical absorption spectra of these nanocrystals display a sharp, high energy peak due to transitions between states localized in individual PbX6(4-) octahedra. These spectral features are insensitive to the size of the particles and in agreement with the features of the corresponding bulk materials. Samples with mixed halide composition exhibit absorption bands that are intermediate in spectral position between those of the pure halide compounds. Furthermore, the absorption bands of intermediate compositions broaden due to the different possible combinations of halide coordination around the Pb(2+) ions. Both observations are supportive of the fact that the [PbX6](4-) octahedra are electronically decoupled in these systems. Because of the large band gap of Cs4PbX6 (>3.2 eV), no excitonic emission in the visible range was observed. The Cs4PbBr6 nanocrystals can be converted into green fluorescent CsPbBr3 nanocrystals by their reaction with an excess of PbBr2 with preservation of size and size distributions. The insertion of PbX2 into Cs4PbX6 provides a means of accessing CsPbX3 nanocrystals in a wide variety of sizes, shapes, and compositions, an important aspect for the development of precisely tuned perovskite nanocrystal inks.

  7. Nearly Monodisperse Insulator Cs4PbX6 (X = Cl, Br, I) Nanocrystals, Their Mixed Halide Compositions, and Their Transformation into CsPbX3 Nanocrystals

    PubMed Central

    2017-01-01

    We have developed a colloidal synthesis of nearly monodisperse nanocrystals of pure Cs4PbX6 (X = Cl, Br, I) and their mixed halide compositions with sizes ranging from 9 to 37 nm. The optical absorption spectra of these nanocrystals display a sharp, high energy peak due to transitions between states localized in individual PbX64– octahedra. These spectral features are insensitive to the size of the particles and in agreement with the features of the corresponding bulk materials. Samples with mixed halide composition exhibit absorption bands that are intermediate in spectral position between those of the pure halide compounds. Furthermore, the absorption bands of intermediate compositions broaden due to the different possible combinations of halide coordination around the Pb2+ ions. Both observations are supportive of the fact that the [PbX6]4– octahedra are electronically decoupled in these systems. Because of the large band gap of Cs4PbX6 (>3.2 eV), no excitonic emission in the visible range was observed. The Cs4PbBr6 nanocrystals can be converted into green fluorescent CsPbBr3 nanocrystals by their reaction with an excess of PbBr2 with preservation of size and size distributions. The insertion of PbX2 into Cs4PbX6 provides a means of accessing CsPbX3 nanocrystals in a wide variety of sizes, shapes, and compositions, an important aspect for the development of precisely tuned perovskite nanocrystal inks. PMID:28196323

  8. Independent Composition and Size Control for Highly Luminescent Indium-Rich Silver Indium Selenide Nanocrystals.

    PubMed

    Yarema, Olesya; Yarema, Maksym; Bozyigit, Deniz; Lin, Weyde M M; Wood, Vanessa

    2015-11-24

    Ternary I-III-VI nanocrystals, such as silver indium selenide (AISe), are candidates to replace cadmium- and lead-based chalcogenide nanocrystals as efficient emitters in the visible and near IR, but, due to challenges in controlling the reactivities of the group I and III cations during synthesis, full compositional and size-dependent behavior of I-III-VI nanocrystals is not yet explored. We report an amide-promoted synthesis of AISe nanocrystals that enables independent control over nanocrystal size and composition. By systematically varying reaction time, amide concentration, and Ag- and In-precursor concentrations, we develop a predictive model for the synthesis and show that AISe sizes can be tuned from 2.4 to 6.8 nm across a broad range of indium-rich compositions from AgIn11Se17 to AgInSe2. We perform structural and optical characterization for representative AISe compositions (Ag0.85In1.05Se2, Ag3In5Se9, AgIn3Se5, and AgIn11Se17) and relate the peaks in quantum yield to stoichiometries exhibiting defect ordering in the bulk. We optimize luminescence properties to achieve a record quantum yield of 73%. Finally, time-resolved photoluminescence measurements enable us to better understand the physics of donor-acceptor emission and the role of structure and composition in luminescence.

  9. Synergistic effect of titanium dioxide nanocrystal/reduced graphene oxide hybrid on enhancement of microbial electrocatalysis

    NASA Astrophysics Data System (ADS)

    Zou, Long; Qiao, Yan; Wu, Xiao-Shuai; Ma, Cai-Xia; Li, Xin; Li, Chang Ming

    2015-02-01

    A small sized TiO2 nanocrystal (˜10 nm)/reduced graphene oxide (TiO2/rGO) hybrid is synthesized through a sol-gel process for hybrid TiO2/GO followed by solvothermal reduction of GO to rGO and is further used as a microbial fuel cell (MFC) anode. The strong synergistic effect from a large surface area produced by uniformly deposited TiO2 nanocrystals, good hydrophilicity of TiO2 nanocrystals and superior conductivity of rGO leads to significantly improved electrocatalysis. In particular, a direct electrochemistry is realized by generating endogenous flavins from a large amount of microbes grown on the highly biocompatible TiO2 nanocrystals to mediate fast electron transfer between microbes and conductive rGO for a high performance anode. The TiO2/rGO hybrid anode delivers a maximum power density of 3169 mW m-2 in Shewanella putrefaciens CN32 MFC, which is much large than that of the conventional carbon cloth anode and reported TiO2/carbon hybrid anode, thus offering great potential for practical applications of MFC. This work is for the first time to report that the synergistic effect from tailoring the physical structure to achieve small sized TiO2 nanocrystals while rationally designing chemistry to introduce highly conductive rGO and superior biocompatible TiO2 is able to significantly boost the MFC performance.

  10. Role of Halides in the Ordered Structure Transitions of Heated Gold Nanocrystal Superlattices

    PubMed Central

    2015-01-01

    Dodecanethiol-capped gold (Au) nanocrystal superlattices can undergo a surprisingly diverse series of ordered structure transitions when heated (Goodfellow, B. W.; Rasch, M. R.; Hessel, C. M.; Patel, R. N.; Smilgies, D.-M.; Korgel, B. A. Nano Lett.2013, 13, 5710–5714). These are the result of highly uniform changes in nanocrystal size, which subsequently force a spontaneous rearrangement of superlattice structure. Here, we show that halide-containing surfactants play an essential role in these transitions. In the absence of any halide-containing surfactant, superlattices of dodecanethiol-capped (1.9-nm-diameter) Au nanocrystals do not change size until reaching about 190–205 °C, at which point the gold cores coalesce. In the presence of halide-containing surfactant, such as tetraoctylphosphonium bromide (TOPB) or tetraoctylammounium bromide (TOAB), the nanocrystals ripen at much lower temperature and superlattices undergo various ordered structure transitions upon heating. Chloride- and iodide-containing surfactants induce similar behavior, destabilizing the Au–thiol bond and reducing the thermal stability of the nanocrystals. PMID:26013597

  11. Physical-chemical properties of furosemide nanocrystals developed using rotation revolution mixer.

    PubMed

    Barbosa, Sávio Fujita; Takatsuka, Takayuki; Tavares, Guilherme Diniz; Araújo, Gabriel Lima Barros; Wang, Hui; Vehring, Reinhard; Löbenberg, Raimar; Bou-Chacra, Nádia Araci

    2016-11-01

    Recently, several approaches have been reported to improve the dissolution rate and bioavailability of furosemide, a class IV drug. However, to the best of our knowledge, none of them proposed nanocrystals. In the last decade, nanocrystals successfully addressed solubility issues by increasing surface area and saturation solubility, both leading to an increase in the dissolution rate of poor water soluble drugs. The preparation of furosemide nanocrystals was by a rotation revolution mixer method. Size distribution and morphology were performed using laser diffraction and scanning electron microscopy, respectively. In addition, differential scanning calorimetry, thermogravimetry, X-ray powder diffraction (XRD) and low frequency shift-Raman spectroscopy allowed investigating the thermal properties and crystalline state. Solubility saturation and intrinsic dissolution rate (IDR) studies were conducted. The thermal analysis revealed lower melting range for the nanocrystals comparing to furosemide. Moreover, a slight crystalline structure change to the amorphous state was observed by XRD and confirmed by low frequency shift Raman. The particle size was reduced to 231 nm with a polydispersity index of 0.232, a 30-fold reduction from the original powder. Finally, the saturation solubility and IDR showed a significant increase. Furosemide nanocrystals showed potential for development of innovative formulations as an alternative to the commercial products.

  12. Adhesion and internalization differences of COM nanocrystals on Vero cells before and after cell damage.

    PubMed

    Gan, Qiong-Zhi; Sun, Xin-Yuan; Ouyang, Jian-Ming

    2016-02-01

    The adhesion and internalization between African green monkey kidney epithelial (Vero) cells (before and after oxidative damage by hydrogen peroxide) and calcium oxalate monohydrate (COM) nanocrystals (97±35nm) were investigated so as to discuss the molecular and cellular mechanism of kidney stone formation. Scanning electron microscope (SEM) was used to observe the Vero-COM nanocrystal adhesion; the nanocrystal-cell adhesion was evaluated by measuring the content of malonaldehyde (MDA), the activity of superoxide dismutase (SOD), the expression level of cell surface osteopontin (OPN) and the change of Zeta potential. Confocal microscopy and flow cytometry were used for the observation and quantitative analysis of crystal internalization. In the process of adhesion, the cell viability and the SOD activity declined, the MDA content, Zeta potential, and the OPN expression level increased. The adhesive capacity of injured Vero was obviously stronger than normal cells; in addition the injured cells promoted the aggregation of COM nanocrystals. The capacity of normal cells to internalize crystals was obviously stronger than that of injured cells. Cell injury increased adhesive sites on cell surface, thereby facilitating the aggregation of COM nanocrystals and their attachment, which results in enhanced risk of calcium oxalate stone formation.

  13. A dual-colored bio-marker made of doped ZnO nanocrystals

    NASA Astrophysics Data System (ADS)

    Wu, Y. L.; Fu, S.; Tok, A. I. Y.; Zeng, X. T.; Lim, C. S.; Kwek, L. C.; Boey, F. C. Y.

    2008-08-01

    Bio-compatible ZnO nanocrystals doped with Co, Cu and Ni cations, surface capped with two types of aminosilanes and titania are synthesized by a soft chemical process. Due to the small particle size (2-5 nm), surface functional groups and the high photoluminescence emissions at the UV and blue-violet wavelength ranges, bio-imaging on human osteosarcoma (Mg-63) cells and histiocytic lymphoma U-937 monocyte cells showed blue emission at the nucleus and bright turquoise emission at the cytoplasm simultaneously. This is the first report on dual-color bio-images labeled by one semiconductor nanocrystal colloidal solution. Bright green emission was detected on mung bean seedlings labeled by all the synthesized ZnO nanocrystals. Cytotoxicity tests showed that the aminosilanes capped nanoparticles are non-toxic. Quantum yields of the nanocrystals varied from 79% to 95%. The results showed the potential of the pure ZnO and Co-doped ZnO nanocrystals for live imaging of both human cells and plant systems.

  14. Synthesis of Multicolor Core/Shell NaLuF₄:Yb(3+)/Ln(3+)@CaF₂ Upconversion Nanocrystals.

    PubMed

    Li, Hui; Hao, Shuwei; Yang, Chunhui; Chen, Guanying

    2017-02-07

    The ability to synthesize high-quality hierarchical core/shell nanocrystals from an efficient host lattice is important to realize efficacious photon upconversion for applications ranging from bioimaging to solar cells. Here, we describe a strategy to fabricate multicolor core @ shell α-NaLuF₄:Yb(3+)/Ln(3+)@CaF₂ (Ln = Er, Ho, Tm) upconversion nanocrystals (UCNCs) based on the newly established host lattice of sodium lutetium fluoride (NaLuF₄). We exploited the liquid-solid-solution method to synthesize the NaLuF₄ core of pure cubic phase and the thermal decomposition approach to expitaxially grow the calcium fluoride (CaF₂) shell onto the core UCNCs, yielding cubic core/shell nanocrystals with a size of 15.6 ± 1.2 nm (the core ~9 ± 0.9 nm, the shell ~3.3 ± 0.3 nm). We showed that those core/shell UCNCs could emit activator-defined multicolor emissions up to about 772 times more efficient than the core nanocrystals due to effective suppression of surface-related quenching effects. Our results provide a new paradigm on heterogeneous core/shell structure for enhanced multicolor upconversion photoluminescence from colloidal nanocrystals.

  15. Facile synthesis of pentacle gold–copper alloy nanocrystals and their plasmonic and catalytic properties

    PubMed Central

    He, Rong; Wang, You-Cheng; Wang, Xiaoyong; Wang, Zhantong; Liu, Gang; Zhou, Wei; Wen, Longping; Li, Qunxiang; Wang, Xiaoping; Chen, Xiaoyuan; Zeng, Jie; Hou, J. G.

    2014-01-01

    The combination of gold and copper is a good way to pull down the cost of gold and ameliorate the instability of copper. Through shape control, the synergy of these two metals can be better exploited. Here, we report an aqueous phase route to the synthesis of pentacle gold–copper alloy nanocrystals with fivefold twinning, the size of which can be tuned in the range from 45 to 200 nm. The growth is found to start from a decahedral core, followed by protrusion of branches along twinning planes. Pentacle products display strong localized surface plasmon resonance peaks in the near-infrared region. Under irradiation by an 808-nm laser, 70-nm pentacle nanocrystals exhibit a notable photothermal effect to kill 4T1 murine breast tumours established on BALB/c mice. In addition, 70-nm pentacle nanocrystals show better catalytic activity than conventional citrate-coated 5-nm Au nanoparticles towards the reduction of p-nitrophenol to p-aminophenol by sodium borohydride. PMID:24999674

  16. A procedure for diamond turning KDP crystals

    SciTech Connect

    Montesanti, R.C.; Thompson, S.L.

    1995-07-07

    A procedure and the equipment necessary for single-point diamond flycutting (loosely referred to as diamond turning) potassium di-hydrogen phosphate (KDP) crystals are described. It is based on current KDP diamond turning activities at the Lawrence Livermore National Laboratory (LLNL), drawing upon knowledge from the Nova crystal finishing development during the 1980`s and incorporating refinements from our efforts during 1995. In addition to describing a step-by-step process for diamond turning KDP, specific discussions are included on the necessary diamond tool geometry and edge sharpness, cutting fluid, and crystal preparation, handling, cleaning, and inspection. The authors presuppose that the reader is already familiar with diamond turning practices.

  17. Sub-10 nm nanopantography

    NASA Astrophysics Data System (ADS)

    Tian, Siyuan; Donnelly, Vincent M.; Ruchhoeft, Paul; Economou, Demetre J.

    2015-11-01

    Nanopantography, a massively parallel nanopatterning method over large areas, was previously shown to be capable of printing 10 nm features in silicon, using an array of 1000 nm-diameter electrostatic lenses, fabricated on the substrate, to focus beamlets of a broad area ion beam on selected regions of the substrate. In the present study, using lens dimensional scaling optimized by computer simulation, and reduction in the ion beam image size and energy dispersion, the resolution of nanopantography was dramatically improved, allowing features as small as 3 nm to be etched into Si.

  18. Diamonds: Exploration, mines and marketing

    NASA Astrophysics Data System (ADS)

    Read, George H.; Janse, A. J. A. (Bram)

    2009-11-01

    The beauty, value and mystique of exceptional quality diamonds such as the 603 carat Lesotho Promise, recovered from the Letseng Mine in 2006, help to drive a multi-billion dollar diamond exploration, mining and marketing industry that operates in some 45 countries across the globe. Five countries, Botswana, Russia, Canada, South Africa and Angola account for 83% by value and 65% by weight of annual diamond production, which is mainly produced by four major companies, De Beers, Alrosa, Rio Tinto and BHP Billiton (BHPB), which together account for 78% by value and 72% by weight of annual diamond production for 2007. During the last twelve years 16 new diamond mines commenced production and 4 re-opened. In addition, 11 projects are in advanced evaluation and may begin operations within the next five years. Exploration for diamondiferous kimberlites was still energetic up to the last quarter of 2008 with most work carried out in Canada, Angola, Democratic Republic of the Congo (DRC) and Botswana. Many kimberlites were discovered but no new economic deposits were outlined as a result of this work, except for the discovery and possible development of the Bunder project by Rio Tinto in India. Exploration methods have benefitted greatly from improved techniques of high resolution geophysical aerial surveying, new research into the geochemistry of indicator minerals and further insights into the formation of diamonds and the relation to tectonic/structural events in the crust and mantle. Recent trends in diamond marketing indicate that prices for rough diamonds and polished goods were still rising up to the last quarter of 2008 and subsequently abruptly sank in line with the worldwide financial crisis. Most analysts predict that prices will rise again in the long term as the gap between supply and demand will widen because no new economic diamond discoveries have been made recently. The disparity between high rough and polished prices and low share prices of publicly

  19. A multilayer innovative solution to improve the adhesion of nanocrystalline diamond coatings

    NASA Astrophysics Data System (ADS)

    Poulon-Quintin, A.; Faure, C.; Teulé-Gay, L.; Manaud, J. P.

    2015-03-01

    Nano-crystalline diamond (NCD) films grown under negative biased substrates by chemical vapor deposition (CVD) are widely used as surface overlay coating onto cermet WC-Co cutting tools to get better performances. To improve the diamond adhesion to the cermet substrate, suitable multi-layer systems have been added. They are composed of a cobalt diffusion barrier close to the substrate (single and sequenced nitrides layers) coated with a nucleation extra layer to improve the nucleus density of diamond during CVD processing. For all systems, before and after diamond deposition, transmission electron microscopy (TEM) has been performed for a better understanding of the diffusion phenomena occurring at the interfaces and to evaluate the presence of graphitic species at the interface with the diamond. Innovative multilayer system dedicated to the regulation of cobalt diffusion coated with a bilayer system optimized for the carbon diffusion control, is shown as an efficient solution to significantly reduce the graphite layer formation at the interface with the diamond down to 10 nm thick and to increase the adhesion of NCD diamond layer as scratch-tests confirm.

  20. Large scale fabrication of nitrogen vacancy-embedded diamond nanostructures for single-photon source applications

    NASA Astrophysics Data System (ADS)

    Jiang, Qianqing; Li, Wuxia; Tang, Chengchun; Chang, Yanchun; Hao, Tingting; Pan, Xinyu; Ye, Haitao; Li, Junjie; Gu, Changzhi

    2016-11-01

    Some color centers in diamond can serve as quantum bits which can be manipulated with microwave pulses and read out with laser, even at room temperature. However, the photon collection efficiency of bulk diamond is greatly reduced by refraction at the diamond/air interface. To address this issue, we fabricated arrays of diamond nanostructures, differing in both diameter and top end shape, with HSQ and Cr as the etching mask materials, aiming toward large scale fabrication of single-photon sources with enhanced collection efficiency made of nitrogen vacancy (NV) embedded diamond. With a mixture of O2 and CHF3 gas plasma, diamond pillars with diameters down to 45 nm were obtained. The top end shape evolution has been represented with a simple model. The tests of size dependent single-photon properties confirmed an improved single-photon collection efficiency enhancement, larger than tenfold, and a mild decrease of decoherence time with decreasing pillar diameter was observed as expected. These results provide useful information for future applications of nanostructured diamond as a single-photon source. Project supported by the National Key Research and Development Plan of China (Grant No. 2016YFA0200402), the National Natural Science Foundation of China (Grants Nos. 11574369, 11574368, 91323304, 11174362, and 51272278), and the FP7 Marie Curie Action (project No. 295208) sponsored by the European Commission.

  1. Fabrication of thin diamond membranes by using hot implantation and ion-cut methods

    NASA Astrophysics Data System (ADS)

    Suk, Jaekwon; Kim, Hyeongkwon; Lim, Weon Cheol; Yune, Jiwon; Moon, Sung; Eliades, John A.; Kim, Joonkon; Lee, Jaeyong; Song, Jonghan

    2017-03-01

    A thin (2 μm) and relatively large area (3 × 3 mm2) diamond membrane was fabricated by cleaving a surface from a single crystal chemical vapor deposition (CVD) diamond wafer (3 × 3 mm2× 300 μm) using a hot implantation and ion-cut method. First, while maintaining the CVD diamond at 400 °C, a damage zone was created at a depth of 2.3 μm underneath the surface by implanting 4 MeV carbon ions into the diamond in order to promote membrane cleavage (hot implantation). According to TEM data, hot implantation reduces the thickness of the implantation damage zone by about a factor of 10 when compared to implanting carbon ions with the CVD diamond at room temperature (RT). In order to recover crystallinity, the implanted sample was then annealed at 850 °C. Next, 380 keV hydrogen ions were implanted into the sample to a depth of 2.3 μm below the surface with the CVD diamond at RT. After annealing at 850 °C, the CVD diamond surface layer was cleaved at the damage-zone due to internal pressure from H2 gas arising from the implanted hydrogen (ion-cut). A thin layer of graphite (˜300 nm) on the cleavage surface, arising from the implanted carbon, was removed by O2 annealing. This technique can potentially be used to produce much larger area membranes of variable thickness.

  2. Stress engineering of high-quality single crystal diamond by heteroepitaxial lateral overgrowth

    NASA Astrophysics Data System (ADS)

    Tang, Y.-H.; Golding, B.

    2016-02-01

    A method for lateral overgrowth of low-stress single crystal diamond by chemical vapor deposition (CVD) is described. The process is initiated by deposition of a thin (550 nm) (001) diamond layer on Ir-buffered a-plane sapphire. The diamond is partially masked by periodic thermally evaporated Au stripes using photolithography. Lateral overgrowth of the Au occurs with extremely effective filtering of threading dislocations. Thermal stress resulting from mismatch of the low thermal expansion diamond and the sapphire substrate is largely accommodated by the ductile Au layer. The stress state of the diamond is investigated by Raman spectroscopy for two thicknesses: at 10 μm where the film has just overgrown the Au mask and at 180 μm where the film thickness greatly exceeds the scale of the masking. For the 10-μm film, the Raman linewidth shows spatial oscillations with the period of the Au stripes with a factor of 2 to 3 reduction relative to the unmasked region. In a 180-μm thick diamond film, the overall surface stress was extremely low, 0.00 ± 0.16 GPa, obtained from the Raman shift averaged over the 7.5 mm diameter of the crystal at its surface. We conclude that the metal mask protects the overgrown diamond layer from substrate-induced thermal stress and cracking. It is also responsible for low internal stress by reducing dislocation density by several orders of magnitude.

  3. Single Crystal Diamond Beam Position Monitors with Radiofrequency Electronic Readout

    SciTech Connect

    Solar, B.; Graafsma, H.; Potdevin, G.; Trunk, U.; Morse, J.; Salome, M.

    2010-06-23

    Over the energy range 5{approx}30 keV a suitably contacted, thin ({approx}100 {mu}m) diamond plate can be operated in situ as a continuous monitor of X-ray beam intensity and position as the diamond absorbs only a small percentage of the incident beam. Single crystal diamond is a completely homogeneous material showing fast (ns), spatially uniform signal response and negligible (diamond beam position monitors of simple quadrant electrode designs with metal contacts, operated using wideband electronic readout corresponding to the RF accelerator frequency. The instrumentation for these monitors must cover a large range of operating conditions: different beam sizes, fluxes, energies and time structure corresponding to the synchrotron fill patterns. Sophisticated new RF sampling electronics can satisfy most requirements: using a modified Libera Brilliance readout system, we measured the center of gravity position of a 25 {mu}m beam at the DORIS III F4 beam line at a rate of 130 Msample/s with narrowband filtering of a few MHz bandwidth. Digitally averaging the signal further provided a spatial resolution {approx}20 nm.

  4. Large piezoresistive effect in surface conductive nanocrystalline diamond

    SciTech Connect

    Janssens, S. D. Haenen, K.; Drijkoningen, S.

    2014-09-08

    Surface conductivity in hydrogen-terminated single crystal diamond is an intriguing phenomenon for fundamental reasons as well as for application driven research. Surface conductivity is also observed in hydrogen-terminated nanocrystalline diamond although the electronic transport mechanisms remain unclear. In this work, the piezoresistive properties of intrinsic surface conductive nanocrystalline diamond are investigated. A gauge factor of 35 is calculated from bulging a diamond membrane of 350 nm thick, with a diameter of 656 μm and a sheet resistance of 1.45 MΩ/sq. The large piezoresistive effect is reasoned to originate directly from strain-induced changes in the resistivity of the grain boundaries. Additionally, we ascribe a small time-dependent fraction of the piezoresistive effect to charge trapping of charge carriers at grain boundaries. In conclusion, time-dependent piezoresistive effect measurements act as a tool for deeper understanding the complex electronic transport mechanisms induced by grain boundaries in a polycrystalline material or nanocomposite.

  5. Native NIR-emitting single colour centres in CVD diamond

    NASA Astrophysics Data System (ADS)

    Gatto Monticone, D.; Traina, P.; Moreva, E.; Forneris, J.; Olivero, P.; Degiovanni, I. P.; Taccetti, F.; Giuntini, L.; Brida, G.; Amato, G.; Genovese, M.

    2014-05-01

    Single-photon sources are a fundamental element for developing quantum technologies, and sources based on colour centres in diamonds are among the most promising candidates. The well-known nitrogen vacancy centres are characterized by several limitations, and thus few other defects have recently been considered. In the present work, we characterize, in detail, native efficient single colour centres emitting in the near infra-red (λ = 740-780 nm) in both standard IIa single-crystal and electronic-grade polycrystalline commercial chemical vapour deposited (CVD) diamond samples. In the former case, a high-temperature (T > 1000 °C) annealing process in vacuum is necessary to induce the formation/activation of luminescent centres with good emission properties, while in the latter case the annealing process has marginally beneficial effects on the number and performance of native centres in commercially available samples. Although displaying significant variability in several photo-physical properties (emission wavelength, emission rate instabilities, saturation behaviours), these centres generally display appealing photophysical properties for applications as single photon sources: short lifetimes (0.7-3 ns), high emission rates (˜50-500 × 103 photons s-1) and strongly (>95%) polarized light. The native centres are tentatively attributed to impurities incorporated in the diamond crystal during the CVD growth of high-quality type-IIa samples, and offer promising perspectives in diamond-based photonics.

  6. Fabrication and characterization of nano-crystalline diamond films

    SciTech Connect

    Gruen, D.M.; Pan, X.; Krauss, A.R.; Liu, S.; Luo, J.; Foster, C.M.

    1993-11-01

    Highly uniform, smooth nano-crystalline diamond films have been fabricated with a magneto-active microwave CVD system. Top and bottom magnet currents were 145A and 60A, while microwave power and substrate temperature were controlled at 1500W and 850{degrees}C during deposition. Total processing pressure was regulated at 40 Pa (300 mTorr), with gas flow rates of 30 sccm of hydrogen, 2.4 sccm of methane and 1 sccm of oxygen. Diamond films obtained under the above conditions have grain sizes between 0.1--0.3 {mu}m, a growth rate of 0.1{mu}m/hr and a mean roughness of 14.95 nm. Characterization techniques have involved XRD, Raman spectroscopy, SEM, AFM and TEM. Both X-ray and electron diffraction patterns show no evidence of non-diamond phases. Although a high density of twins and stacking faults were revealed by HREM, compact diamond grains and clean intergranular boundaries (no graphitic or amorphous phases) were observed.

  7. Hierarchical assembly of protein nanocrystals into macroscopic gels

    NASA Astrophysics Data System (ADS)

    Greene, Daniel; Sandler, Stanley; Wagner, Norman; Lenhoff, Abraham

    From crystallization screens to downstream processing, protein gel phases are common during protein solution processing. While the structure of crystalline protein is well known, very little is known about the structure of these gel phases. We recently measured the microstructure of a salted-out ovalbumin dense phase and found that nanocrystalline protein clusters, which are only a few unit cells in size, percolate 5 micron gel beads. It is unclear if the behavior seen for ovalbumin is representative of a more general phenomenon. Here we present microstructural measurements on a salted-out monoclonal antibody (mAb) and salted-out ribonuclease-a that support this possibility. Using small-angle x-ray and neutron scattering (SAS) and transmission electron microscopy (TEM), we find both salted-out mAb and ribonuclease-a gels exhibit nanocrystalline regions. Within the mAb gel, the mAb aggregates into hollow tubular structures that are hundreds of nanometers long, have an inner diameter of approximately 15-20 nm and an outer diameter of approximately 20-30 nm. The SAS intensity from these structures contains a peak at high-q that is commensurate with scattering from idealized mAb nanocrystals that are 1-2 unit cells wide. Ribonuclease-a does not appear to from tubular structures, but the SAS intensity contains peaks at high-q that are consistent with the scattering from a nanocrystal 2-3 unit cells wide. Power-law scattering at low-q indicates the nanocrystals aggregate into a gel with fractal dimension 2.5. This research provides insight into the nanostructure and formation of protein gel phases.

  8. Structure Map for Embedded Binary Alloy Nanocrystals

    SciTech Connect

    Yuan, C.W.; Shin, S.J.; Liao, C.Y.; Guzman, J.; Stone, P.R.; Watanabe, M.; Ager III, J.W.; Haller, E.E.; Chrzan, D.C.

    2008-09-20

    The equilibrium structure of embedded nanocrystals formed from strongly segregating binary-alloys is considered within a simple thermodynamic model. The model identifies two dimensionlessinterface energies that dictate the structure, and allows prediction of the stable structure for anychoice of these parameters. The resulting structure map includes three distinct nanocrystal mor-phologies: core/shell, lobe/lobe, and completely separated spheres.

  9. Microscopic diamond solid-immersion-lenses fabricated around single defect centers by focused ion beam milling

    SciTech Connect

    Jamali, Mohammad; Rezai, Mohammad; Fedder, Helmut; Gerhardt, Ilja; Wrachtrup, Jörg; Frenner, Karsten

    2014-12-15

    Recent efforts to define microscopic solid-immersion-lenses (SIL) by focused ion beam milling into diamond substrates that are registered to a preselected single photon emitter are summarized. We show how we determine the position of a single emitter with at least 100 nm lateral and 500 nm axial accuracy, and how the milling procedure is optimized. The characteristics of a single emitter, a Nitrogen Vacancy (NV) center in diamond, are measured before and after producing the SIL and compared with each other. A count rate of 1.0 × 10{sup 6} counts/s is achieved with a [111] oriented NV center.

  10. Electronic displays using optically pumped luminescent semiconductor nanocrystals

    DOEpatents

    Weiss, Shimon; Schlam, Michael C; Alivisatos, A. Paul

    2014-03-25

    A multicolor electronic display is based on an array of luminescent semiconductor nanocrystals. Nanocrystals which emit tight of different colors are grouped into pixels. The nanocrystals are optically pumped to produce a multicolor display. Different sized nanocrystals are used to produce the different colors. A variety of pixel addressing systems can be used.

  11. Electronic displays using optically pumped luminescent semiconductor nanocrystals

    DOEpatents

    Weiss, Shimon; Schlamp, Michael C.; Alivisatos, A. Paul

    2010-04-13

    A multicolor electronic display is based on an array of luminescent semiconductor nanocrystals. Nanocrystals which emit light of different colors are grouped into pixels. The nanocrystals are optically pumped to produce a multicolor display. Different sized nanocrystals are used to produce the different colors. A variety of pixel addressing systems can be used.

  12. Electronic displays using optically pumped luminescent semiconductor nanocrystals

    DOEpatents

    Weiss, Shimon; Schlamp, Michael C; Alivisatos, A. Paul

    2014-02-11

    A multicolor electronic display is based on an array of luminescent semiconductor nanocrystals. Nanocrystals which emit light of different colors are grouped into pixels. The nanocrystals are optically pumped to produce a multicolor display. Different sized nanocrystals are used to produce the different colors. A variety of pixel addressing systems can be used.

  13. Electronic displays using optically pumped luminescent semiconductor nanocrystals

    DOEpatents

    Weiss, Shimon; Schlamp, Michael C.; Alivisatos, Paul A.

    2015-11-10

    A multicolor electronic display is based on an array of luminescent semiconductor nanocrystals. Nanocrystals which emit tight of different colors are grouped into pixels. The nanocrystals are optically pumped to produce a multicolor display. Different sized nanocrystals are used to produce the different colors. A variety of pixel addressing systems can be used.

  14. Electronic displays using optically pumped luminescent semiconductor nanocrystals

    DOEpatents

    Weiss, Shimon; Schlamp, Michael C.; Alivisatos, A. Paul

    2015-06-23

    A multicolor electronic display is based on an array of luminescent semiconductor nanocrystals. Nanocrystals which emit light of different colors are grouped into pixels. The nanocrystals are optically pumped to produce a multicolor display. Different sized nanocrystals are used to produce the different colors. A variety of pixel addressing systems can be used.

  15. Electronic displays using optically pumped luminescent semiconductor nanocrystals

    DOEpatents

    Weiss, Shimon; Schlamp, Michael C.; Alivisatos, A. Paul

    2011-09-27

    A multicolor electronic display is based on an array of luminescent semiconductor nanocrystals. Nanocrystals which emit light of different colors are grouped into pixels. The nanocrystals are optically pumped to produce a multicolor display. Different sized nanocrystals are used to produce the different colors. A variety of pixel addressing systems can be used.

  16. Electronic displays using optically pumped luminescent semiconductor nanocrystals

    DOEpatents

    Weiss, Shimon; Schlamp, Michael C.; Alivisatos, A. Paul

    2005-03-08

    A multicolor electronic display is based on an array of luminescent semiconductor nanocrystals. Nanocrystals which emit light of different colors are grouped into pixels. The nanocrystals are optically pumped to produce a multicolor display. Different sized nanocrystals are used to produce the different colors. A variety of pixel addressing systems can be used.

  17. Synthesis and characterization of embedded germanium nanocrystals

    NASA Astrophysics Data System (ADS)

    Xu, Qing

    Isotopically pure Ge nanocrystals have been synthesized by ion implantation followed by thermal annealing in amorphous silica and crystalline sapphire matrix. The structure, and the mechanical and thermal properties of the two systems are studied and compared. Ge cluster nucleation during implantation is observed in as-implanted silica samples. It results in the wide size distribution observed after thermal annealing. Theoretical calculations predict that if the nucleation during implantation can be suppressed, a much narrower size distribution is achievable. As-grown Ge nanocrystals are under large compressive stress, 1.2GPa for nanocrystals embedded in silica, and 4GPa for those embedded in sapphire. The stress can be gradually relieved by vapor etching, liberating the nanocrystals from the matrix as well as post-growth thermal treatments. One of the main sources of the stress observed in the sapphire system is the volume expansion of Ge clusters in the liquid/solid phase transformation which occurs during the cooling process from annealing temperature to room temperature, as the density of liquid Ge is larger by 4.6% than that of solid Ge. The large stress and damage in the sapphire matrix lead to a unique double-peak size distribution of the Ge nanocrystals. However, the in situ transmission electron microscopy (TEM) experiments indicate that the Ge nanocrystals embedded in silica are already in their solid phase at the annealing temperature. Therefore, the stress originates from other sources. Vapor etching with HF solutions enables a gradual exposure of embedded Ge nanocrystals in SiO2, while the liquid etching in HF solution leaves fully liberated Ge nanocrystals loosely packed on the Si substrate. Transfer of liberated Ge nanocrystals to other surfaces is achieved by solution dispersion and subsequent evaporation. The patterning of nanocrystals has been achieved by a combination of lithography, coimplantation and electron irradiation. The latter one will

  18. Study of optical and luminescent properties of nanocrystals NaYF4:Tm3+, Yb3+ in the UV range in the application of integrated optics

    NASA Astrophysics Data System (ADS)

    Asharchuk, I. M.; Molchanova, S. I.; Rocheva, V. V.; Baranov, M. S.; Sarycheva, M. E.; Khaydukov, K. V.

    2016-12-01

    Studied the photoluminescence properties of synthesized nanocrystals doped with rare-earth ions NaYF4:Tm3+, Yb3+, measured luminescence spectra and absorption in the visible and near infrared regions of 300-1000 nm. Were measured the energy of phonons these nanocrystals, the average phonon energy was 332cm-1. Made optical waveguide impregnated with nanoparticles NaYF4: Yb3+, Tm3+ as the prospect of a compact source of radiation in the visible and UV range.

  19. Multiple exciton generation in colloidal silicon nanocrystals.

    PubMed

    Beard, Matthew C; Knutsen, Kelly P; Yu, Pingrong; Luther, Joseph M; Song, Qing; Metzger, Wyatt K; Ellingson, Randy J; Nozik, Arthur J

    2007-08-01

    Multiple exciton generation (MEG) is a process whereby multiple electron-hole pairs, or excitons, are produced upon absorption of a single photon in semiconductor nanocrystals (NCs) and represents a promising route to increased solar conversion efficiencies in single-junction photovoltaic cells. We report for the first time MEG yields in colloidal Si NCs using ultrafast transient absorption spectroscopy. We find the threshold photon energy for MEG in 9.5 nm diameter Si NCs (effective band gap identical with Eg = 1.20 eV) to be 2.4 +/- 0.1Eg and find an exciton-production quantum yield of 2.6 +/- 0.2 excitons per absorbed photon at 3.4Eg. While MEG has been previously reported in direct-gap semiconductor NCs of PbSe, PbS, PbTe, CdSe, and InAs, this represents the first report of MEG within indirect-gap semiconductor NCs. Furthermore, MEG is found in relatively large Si NCs (diameter equal to about twice the Bohr radius) such that the confinement energy is not large enough to produce a large blue-shift of the band gap (only 80 meV), but the Coulomb interaction is sufficiently enhanced to produce efficient MEG. Our findings are of particular importance because Si dominates the photovoltaic solar cell industry, presents no problems regarding abundance and accessibility within the Earth's crust, and poses no significant environmental problems regarding toxicity.

  20. Development of curcumin nanocrystal: physical aspects.

    PubMed

    Rachmawati, Heni; Al Shaal, Loaye; Müller, Rainer H; Keck, Cornelia M

    2013-01-01

    Curcumin, a naturally occuring polyphenolic phytoconstituent, is isolated from the rhizomes of Curcuma longa Linn. (Zingiberaceae). It is water insoluble under acidic or neutral conditions but dissolves in alkaline environment. In neutral or alkaline conditions, curcumin is highly unstable undergoing rapid hydrolytic degradation to feruloyl methane and ferulic acid. Thus, the use of curcumin is limited by its poor aqueous solubility in acidic or neutral conditions and instability in alkaline pH. In the present study, curcumin nanocrystals were prepared using high-pressure homogenization, to improve its solubility. Five different stabilizers [polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), d-α-tocopherol polyethylene glycol 1000 succinate (TPGS), sodium dodecyl sulfate (SDS), carboxymethylcellulose sodium salt] possessing different stabilization mechanism were investigated. The nanoparticles were characterized with regard to size, surface charge, shape and morphology, thermal property, and crystallinity. A short-term stability study was performed storing the differently stabilized nanoparticles at 4°C and room temperature. PVA, PVP, TPGS, and SDS successfully produced curcumin nanoparticle with the particle size in the range of 500-700 nm. PVA, PVP, and TPGS showed similar performance in preserving the curcumin nanosuspension stability. However, PVP is the most efficient polymer to stabilize curcumin nanoparticle. This study illustrates that the developed curcumin nanoparticle held great potential as a possible approach to improve the curcumin solubility then enhancing bioavailability.