Theoretical study of ZnS/CdS bi-layer for thin-film CdTe solar cell

NASA Astrophysics Data System (ADS)

Mohamed, H. A.; Mohamed, A. S.; Ali, H. M.

2018-05-01

The performance of CdTe solar cells is strongly limited by the thickness of CdS window layer. A higher short-circuit current density might be achieved by decreasing the thickness of CdS layer as a result of reducing the absorption losses that take place in this layer. However, it is difficult to obtain uniform and pin-hole free CdS layers thinner than 50 nm. This problem can be solved through increasing the band gap of the window layer by adding a wide band gap semiconductor such as ZnS. In this work, bi-layer ZnS/CdS film was studied as an improved window layer of ITO/ZnS/CdS/CdTe solar cell. The total thickness of ZnS/CdS layer was taken about 60 nm. The effect of optical losses due to reflection at different interfaces in the cell and absorption in ITO, ZnS, CdS as well as the recombination loss have been studied. Finally, the effects of the recombination losses in the space-charge region and the reflectivity from the back contact were taken into accounts. The results revealed that the optical losses of 23% were achieved at 60 nm thickness of CdS and theses losses minimized to 18% when ZnS layer of 30 nm thickness was added to CdS layer. The minimum optical and recombination losses of about 26% were obtained at 1 ns of electron life-time and ∼0.4 μm width of the space-charge region. The maximum efficiency of 18.5% was achieved for ITO/CdS/CdTe cell and the efficiency increased up to 20% for ITO/ZnS/CdS/CdTe cell.

Electrical properties of MIS devices on CdZnTe/HgCdTe

NASA Astrophysics Data System (ADS)

Lee, Tae-Seok; Jeoung, Y. T.; Kim, Hyun Kyu; Kim, Jae Mook; Song, Jinhan; Ann, S. Y.; Lee, Ji Y.; Kim, Young Hun; Kim, Sun-Ung; Park, Mann-Jang; Lee, S. D.; Suh, Sang-Hee

1998-10-01

In this paper, we report the capacitance-voltage (C-V) properties of metal-insulator-semiconductor (MIS) devices on CdTe/HgCdTe by the metalorganic chemical vapor deposition (MOCVD) and CdZnTe/HgCdTe by thermal evaporation. In MOCVD, CdTe layers are directly grown on HgCdTe using the metal organic sources of DMCd and DiPTe. HgCdTe layers are converted to n-type and the carrier concentration, ND is low 1015 cm-3 after Hg-vacancy annealing at 260 degrees Celsius. In thermal evaporation, CdZnTe passivation layers were deposited on HgCdTe surfaces after the surfaces were etched with 0.5 - 2.0% bromine in methanol solution. To investigate the electrical properties of the MIS devices, the C-V measurement is conducted at 80 K and 1 MHz. C-V curve of MIS devices on CdTe/HgCdTe by MOCVD has shown nearly flat band condition and large hysteresis, which is inferred to result from many defects in CdTe layer induced during Hg-vacancy annealing process. A negative flat band voltage (VFB approximately equals -2 V) and a small hysteresis have been observed for MIS devices on CdZnTe/HgCdTe by thermal evaporation. It is inferred that the negative flat band voltage results from residual Te4+ on the surface after etching with bromine in methanol solution.

Phosphine-free synthesis of high-quality reverse type-I ZnSe/CdSe core with CdS/CdxZn1 - xS/ZnS multishell nanocrystals and their application for detection of human hepatitis B surface antigen

NASA Astrophysics Data System (ADS)

Shen, Huaibin; Yuan, Hang; Niu, Jin Zhong; Xu, Shasha; Zhou, Changhua; Ma, Lan; Li, Lin Song

2011-09-01

Highly photoluminescent (PL) reverse type-I ZnSe/CdSe nanocrystals (NCs) and ZnSe/CdSe/CdS/CdxZn1 - xS/ZnS core/multishell NCs were successfully synthesized by a phosphine-free method. By this low-cost, 'green' synthesis route, more than 10 g of high-quality ZnSe/CdSe/CdS/CdxZn1 - xS/ZnS NCs were synthesized in a large scale synthesis. After the overgrowth of a CdS/CdxZn1 - xS/ZnS multishell on ZnSe/CdSe cores, the PL quantum yields (QYs) increased from 28% to 75% along with the stability improvement. An amphiphilic oligomer was used as a surface coating agent to conduct a phase transfer experiment, core/multishell NCs were dissolved in water by such surface modification and the QYs were still kept above 70%. The as-prepared water dispersible ZnSe/CdSe/CdS/CdxZn1 - xS/ZnS core/multishell NCs not only have high fluorescence QYs but also are extremely stable in various physiological conditions. Furthermore, a biosensor system (lateral flow immunoassay system, LFIA) for the detection of human hepatitis B surface antigen (HBsAg) was developed by using this water-soluble core/multishell NCs as a fluorescent label and a nitrocellulose filter membrane for lateral flow. The result showed that such ZnSe/CdSe/CdS/CdxZn1 - xS/ZnS core/multishell NCs were excellent fluorescent labels to detect HBsAg. The sensitivity of HBsAg detection could reach as high as 0.05 ng ml - 1.

High Pressure Properties of a Ba-Cu-Zn-P Clathrate-I

DOE PAGES

Dolyniuk, Juli -Anna; Kovnir, Kirill

2016-08-12

Here, the high pressure properties of the novel tetrel-free clathrate, Ba 8Cu 13.1Zn 3.3P 29.6, were investigated using synchrotron powder X-ray diffraction. The pressure was applied using a diamond anvil cell. No structural transitions or decomposition were detected in the studied pressure range of 0.1–7 GPa. The calculated bulk modulus for Ba 8Cu 13.1Zn 3.3P 29.6 using a third-order Birch-Murnaghan equation of state is 65(6) GPa at 300 K. This bulk modulus is comparable to the bulk moduli of Ge- and Sn-based clathrates, like A 8Ga 16Ge 30 (A = Sr, Ba) and Sn 19.3Cu 4.7P 22I 8, but lowermore » than those for the transition metal-containing silicon-based clathrates, Ba 8 T xSi46–x, T = Ni, Cu; 3 ≤ x ≤ 5.« less

Low-Cd CIGS solar cells made with a hybrid CdS/Zn(O,S) buffer layer

DOE PAGES

Garris, Rebekah L.; Mansfield, Lorelle M.; Egaas, Brian; ...

2016-10-27

In Cu(In,Ga)Se2 (CIGS) solar cells, CdS and Zn(O,S) buffer layers were compared with a hybrid buffer layer consisting of thin CdS followed Zn(O,S). We explore the physics of this hybrid layer that combines the standard (Cd) approach with the alternative (Zn) approach in the pursuit to unlock further potential for CIGS technology. CdS buffer development has shown optimal interface properties, whereas Zn(O,S) buffer development has shown increased photocurrent. Although a totally Cd-free solar module is more marketable, the retention of a small amount of Cd can be beneficial to achieve optimum junction properties. As long as the amount of Cdmore » is reduced to less than 0.01% by weight, the presence of Cd does not violate the hazardous substance restrictions of the European Union (EU). We estimate the amount of Cd allowed in the EU for CIGS on both glass and stainless steel substrates, and we show that reducing Cd becomes increasingly important as substrate weights decrease. As a result, this hybrid buffer layer had reduced Cd content and a wider space charge region, while achieving equal or better solar cell performance than buffer layers of either CdS or Zn(O,S) alone.« less

CdS/ZnS nanocomposites: from mechanochemical synthesis to cytotoxicity issues.

PubMed

Baláž, Peter; Baláž, Matej; Dutková, Erika; Zorkovská, Anna; Kováč, Jaroslav; Hronec, Pavol; Kováč, Jaroslav; Čaplovičová, Mária; Mojžiš, Ján; Mojžišová, Gabriela; Eliyas, Alexander; Kostova, Nina G

2016-01-01

CdS/ZnS nanocomposites have been prepared by a two-step solid-state mechanochemical synthesis. CdS has been prepared from cadmium acetate and sodium sulfide precursors in the first step. The obtained cubic CdS (hawleyite, JCPDS 00-010-0454) was then mixed in the second step with the cubic ZnS (sphalerite, JCPDS 00-005-0566) synthesized mechanochemically from the analogous precursors. The crystallite sizes of the new type CdS/ZnS nanocomposite, calculated based on the XRD data, were 3-4 nm for both phases. The synthesized nanoparticles have been further characterized by high-resolution transmission electron microscopy (HRTEM) and micro-photoluminescence (μPL) spectroscopy. The PL emission peaks in the PL spectra are attributed to the recombination of holes/electrons in the nanocomposites occurring in depth associated with Cd, Zn vacancies and S interstitials. Their photocatalytic activity was also measured. In the photocatalytic activity tests to decolorize Methyl Orange dye aqueous solution, the process is faster and its effectivity is higher when using CdS/ZnS nanocomposite, compared to single phase CdS. Very low cytotoxic activity (high viability) of the cancer cell lines (selected as models of living cells) has been evidenced for CdS/ZnS in comparison with CdS alone. This fact is in a close relationship with Cd(II) ions dissolution tested in a physiological solution. The concentration of cadmium dissolved from CdS/ZnS nanocomposites with variable Cd:Zn ratio was 2.5-5.0 μg.mL(-1), whereas the concentration for pure CdS was much higher - 53 μg.ml(-1). The presence of ZnS in the nanocrystalline composite strongly reduced the release of cadmium into the physiological solution, which simulated the environment in the human body. The obtained CdS/ZnS quantum dots can serve as labeling media and co-agents in future anti-cancer drugs, because of their potential in theranostic applications. Copyright © 2015 Elsevier B.V. All rights reserved.

65Zn and 133Ba standardizing by photon-photon coincidence counting

NASA Astrophysics Data System (ADS)

Loureiro, Jamir S.; da Cruz, Paulo A. L.; Iwahara, Akira; Delgado, José U.; Lopes, Ricardo T.

2018-03-01

The LNMRI/Brazil has deployed a system using X-gamma coincidence technique for the standardizing radionuclide, which present simple and complex decay scheme with X-rays of energy below 100 keV. The work was carried on radionuclide metrology laboratory using a sodium iodide detector, for gamma photons, in combination with a high purity germanium detector for X-rays. Samples of 65Zn and 133Ba were standardized and the results for both radionuclides showed good precision and accuracy when compared with reference values. The standardization differences were 0.72 % for 65Zn and 0.48 % for 133Ba samples.

Ecotoxicological risks of the abandoned F-Ba-Pb-Zn mining area of Osor (Spain).

PubMed

Bori, Jaume; Vallès, Bettina; Navarro, Andrés; Riva, Maria Carme

2017-06-01

Due to its potential toxic properties, metal mobilization is of major concern in areas surrounding Pb-Zn mines. In the present study, metal contents and toxicity of soils, aqueous extracts from soils and mine drainage waters from an abandoned F-Ba-Pb-Zn mining area in Osor (Girona, NE Spain) were evaluated through chemical extractions and ecotoxicity bioassays. Toxicity assessment in the terrestrial compartment included lethal and sublethal endpoints on earthworms Eisenia fetida, arthropods Folsomia candida and several plant species, whereas aquatic tests involved bacteria Vibrio fischeri, microalgae Raphidocelis subcapitata and crustaceans Daphnia magna. Total concentrations of Ba (250-5110 mg kg -1 ), Pb (940 to >5000 mg kg -1 ) and Zn (2370-11,300 mg kg -1 ) in soils exceeded intervention values to protect human health. Risks for the aquatic compartment were identified in the release of drainage waters and in the potential leaching and runoff of metals from contaminated soils, with Cd (1.98-9.15 µg L -1 ), Pb (2.11-326 µg L -1 ) and Zn (280-2900 µg L -1 ) concentrations in filtered water samples surpassing US EPA Water Quality Criteria (2016a, b). Terrestrial ecotoxicity tests were in accordance with metal quantifications and identified the most polluted soil as the most toxic. Avoidance and reproduction tests with earthworms showed the highest sensitivity to metal contamination. Aquatic bioassays performed in aqueous extracts from soils confirmed the results from terrestrial tests and also detected toxic effects caused by the mine drainage waters. Algal growth inhibition was the most sensitive aquatic endpoint. In view of the results, the application of a containment or remediative procedure in the area is encouraged.

CdZnTe substrate impurities and their effects on liquid phase epitaxy HgCdTe

NASA Astrophysics Data System (ADS)

Tower, J. P.; Tobin, S. P.; Kestigian, M.; Norton, P. W.; Bollong, A. B.; Schaake, H. F.; Ard, C. K.

1995-05-01

Impurity levels were tracked through the stages of substrate and liquid phase epitaxy (LPE) layer processing to identify sources of elements which degrade infrared photodetector performance. Chemical analysis by glow discharge mass spectrometry and Zeeman corrected graphite furnace atomic absorption effectively showed the levels of impurities introduced into CdZnTe substrate material from the raw materials and the crystal growth processes. A new purification process (in situ distillation zone refining) for raw materials was developed, resulting in improved CdZnTe substrate purity. Substrate copper contamination was found to degrade the LPE layer and device electrical properties, in the case of lightly doped HgCdTe. Anomalous HgCdTe carrier type conversion was correlated to certain CdZnTe and CdTe substrate ingots.

Enriching rice with Zn and Fe while minimizing Cd risk

PubMed Central

Slamet-Loedin, Inez H.; Johnson-Beebout, Sarah E.; Impa, Somayanda; Tsakirpaloglou, Nikolaos

2015-01-01

Enriching iron (Fe) and zinc (Zn) content in rice grains, while minimizing cadmium (Cd) levels, is important for human health and nutrition. Natural genetic variation in rice grain Zn enables Zn-biofortification through conventional breeding, but limited natural Fe variation has led to a need for genetic modification approaches, including over-expressing genes responsible for Fe storage, chelators, and transporters. Generally, Cd uptake and allocation is associated with divalent metal cations (including Fe and Zn) transporters, but the details of this process are still unknown in rice. In addition to genetic variation, metal uptake is sometimes limited by its bioavailability in the soil. The availability of Fe, Zn, and Cd for plant uptake varies widely depending on soil redox potential. The typical practice of flooding rice increases Fe while decreasing Zn and Cd availability. On the other hand, moderate soil drying improves Zn uptake but also increases Cd and decreases Fe uptake. Use of Zn- or Fe-containing fertilizers complements breeding efforts by providing sufficient metals for plant uptake. In addition, the timing of nitrogen fertilization has also been shown to affect metal accumulation in grains. The purpose of this mini-review is to identify knowledge gaps and prioritize strategies for improving the nutritional value and safety of rice. PMID:25814994

Photorefractivity in a Titanium Doped ZnCdTe Crystal

NASA Technical Reports Server (NTRS)

Davis, M.; Collins, L.; Dyer, K.; Tong, J.; Ueda, A.; Chen, H.; Chen, K.-T.; Burger, A.; Pan, Z.; Morgan, S. H.

1997-01-01

Single crystals of Zn(.04)Cd(.96)Te was grown by horizontal physical vapor transport (PVT) method and doped by annealing with TiTe2 powder at 600 C for six days. Photorefractive two-beam coupling, along with photoluminescence and absorption spectroscopy, were used to characterize the ZnCdTe:Ti crystal. At 1.32 micrometers, the photorefractive gain has been measured as a function of the grating period. A gain of about 0.16/cm was obtained at an intensity of about 0.1 W/sq cm. The results of this titanium doped ZnCdTe crystal are compared to that of vanadium-doped CdTe crystals reported previously.

Histidine pairing at the metal transport site of mammalian ZnT transporters controls Zn2+ over Cd2+ selectivity.

PubMed

Hoch, Eitan; Lin, Wei; Chai, Jin; Hershfinkel, Michal; Fu, Dax; Sekler, Israel

2012-05-08

Zinc and cadmium are similar metal ions, but though Zn(2+) is an essential nutrient, Cd(2+) is a toxic and common pollutant linked to multiple disorders. Faster body turnover and ubiquitous distribution of Zn(2+) vs. Cd(2+) suggest that a mammalian metal transporter distinguishes between these metal ions. We show that the mammalian metal transporters, ZnTs, mediate cytosolic and vesicular Zn(2+) transport, but reject Cd(2+), thus constituting the first mammalian metal transporter with a refined selectivity against Cd(2+). Remarkably, the bacterial ZnT ortholog, YiiP, does not discriminate between Zn(2+) and Cd(2+). A phylogenetic comparison between the tetrahedral metal transport motif of YiiP and ZnTs identifies a histidine at the mammalian site that is critical for metal selectivity. Residue swapping at this position abolished metal selectivity of ZnTs, and fully reconstituted selective Zn(2+) transport of YiiP. Finally, we show that metal selectivity evolves through a reduction in binding but not the translocation of Cd(2+) by the transporter. Thus, our results identify a unique class of mammalian transporters and the structural motif required to discriminate between Zn(2+) and Cd(2+), and show that metal selectivity is tuned by a coordination-based mechanism that raises the thermodynamic barrier to Cd(2+) binding.

Histidine pairing at the metal transport site of mammalian ZnT transporters controls Zn2+ over Cd2+ selectivity

PubMed Central

Hoch, Eitan; Lin, Wei; Chai, Jin; Hershfinkel, Michal; Fu, Dax; Sekler, Israel

2012-01-01

Zinc and cadmium are similar metal ions, but though Zn2+ is an essential nutrient, Cd2+ is a toxic and common pollutant linked to multiple disorders. Faster body turnover and ubiquitous distribution of Zn2+ vs. Cd2+ suggest that a mammalian metal transporter distinguishes between these metal ions. We show that the mammalian metal transporters, ZnTs, mediate cytosolic and vesicular Zn2+ transport, but reject Cd2+, thus constituting the first mammalian metal transporter with a refined selectivity against Cd2+. Remarkably, the bacterial ZnT ortholog, YiiP, does not discriminate between Zn2+ and Cd2+. A phylogenetic comparison between the tetrahedral metal transport motif of YiiP and ZnTs identifies a histidine at the mammalian site that is critical for metal selectivity. Residue swapping at this position abolished metal selectivity of ZnTs, and fully reconstituted selective Zn2+ transport of YiiP. Finally, we show that metal selectivity evolves through a reduction in binding but not the translocation of Cd2+ by the transporter. Thus, our results identify a unique class of mammalian transporters and the structural motif required to discriminate between Zn2+ and Cd2+, and show that metal selectivity is tuned by a coordination-based mechanism that raises the thermodynamic barrier to Cd2+ binding. PMID:22529353

Evaluation of ZnO:Al as a contact material to CdZnTe for radiation detector applications (Conference Presentation)

NASA Astrophysics Data System (ADS)

Roy, Utpal N.; Camarda, Giuseppe S.; Cui, Yonggang; Gul, Rubi; Hossain, Anwar; Yang, Ge; James, Ralph B.; Pradhan, Aswini K.; Mundle, Rajeh

2016-09-01

Aluminum (Al) doped ZnO with very high Al concentration acts as metal regarding its electrical conductivity. ZnO offers many advantages over the commonly-known metals being used today as electrode materials for nuclear detector fabrication. Often, the common metals show poor adhesion to CdZnTe or CdTe surfaces and have a tendency to peel off. In addition, there is a large mismatch of the coefficients of thermal expansion (CTE) between the metals and underlying CdZnTe, which is one of the reasons for mechanical degradation of the contact. In contrast ZnO has a close match of the CTE with CdZnTe and possesses 8-20 times higher hardness than the commonly-used metals. In this presentation, we will explore and discuss the properties of CdZnTe detectors with ZnO:Al contacts.

A suitable deposition method of CdS for high performance CdS-sensitized ZnO electrodes: Sequential chemical bath deposition

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

Chen, Haining; Li, Weiping; Liu, Huicong

2010-07-15

A suitable deposition method of CdS is necessary for the high performance CdS-sensitized ZnO electrodes. In this paper, chemical bath deposition (CBD) and sequential chemical bath deposition (S-CBD) methods were used to deposit CdS on ZnO mesoporous films for ZnO/CdS electrodes. The analysis results of XRD patterns and UV-vis spectroscopy indicated that CBD deposition method leaded to the dissolving of ZnO mesoporous films in deposition solution and thickness reduction of ZnO/CdS electrodes. Absorption in visible region by the ZnO/CdS electrodes with CdS deposition by S-CBD was enhanced as deposition cycles increased due to the stability of ZnO mesoporous films inmore » the S-CBD deposition solutions. The results of photocurrent-voltage (I-V) measurement showed that the performance of ZnO/CdS electrodes with CdS deposition by CBD first increased and then decreased as deposition time increased, and the greatest short-circuit current (J{sub sc}) was obtained at the deposition time of 4 min. The performance of ZnO/CdS electrodes with CdS deposition by S-CBD increased as deposition cycles increased, and both open-circuit voltage (V{sub oc}) and J{sub sc} were greater than those electrodes with CdS deposition by CBD when the deposition cycles of S-CBD were 10 or greater. These results indicated that S-CBD is a more suitable method for high performance ZnO/CdS electrodes. (author)« less

Differential effects of β-mercaptoethanol on CdSe/ZnS and InP/ZnS quantum dots.

PubMed

Georgin, Marcel; Carlini, Lina; Cooper, Daniel; Bradforth, Stephen E; Nadeau, Jay L

2013-07-07

The small thiol β-mercaptoethanol (BME) has been used as an anti-blinking reagent for CdSe/ZnS quantum dots (QDs), although its effects on QD photoluminescence are complex. It acts as an antioxidant as well as a hole scavenger on both CdSe and CdTe, which leads to changes in emission intensity and lifetime that vary qualitatively according to BME concentration, time of incubation, and pH of the solution. Because the band edge energies of InP/ZnS are shifted from those of CdTe and CdSe, it may be expected that thiols including BME might be unable to trap holes from these QDs. In this study, we use steady-state and time-resolved emission spectroscopy with physical fitting models combined with blinking analysis to compare the effects of different concentrations of BME on CdSe/ZnS vs. InP/ZnS QDs over time. We also find excellent correspondence between simple physical model parameters and blinking off times, a finding that will be useful for all blinking studies involving semiconductor nanoparticles. BME alters blinking in InP/ZnS QDs with a single ZnS shell, but not those with double thickness shells. The effects are similar to those seen with CdSe/ZnS, despite very different effects of BME on steady-state spectra, and highly pH-dependent.

[Effect of different organic fertilizers on bioavailability of soil Cd and Zn].

PubMed

Xie, Yun-he; Ji, Xiong-hui; Wu, Jia-mei; Huang, Juan; Guan, Di; Zhu, Jian

2015-03-01

The active effect of soil Cd and Zn and their interaction was studied in typical paddy field in south China by monitoring the contents of Cd and Zn in soil and rice in rice fields applied with pig manure, chicken manure or rice straw for 4 years continuously. The results showed that applying pig manure, chicken manure or rice straw had no significant impact on the soil total Cd content, soil available Cd content and soil Cd activity, but tended to increase the soil total Cd content and increased the soil total Zn content, soil available Zn content and Zn activity significantly. Applications of pig manure, chicken manure and rice straw all reduced the Cd content of brown rice, in order of pig manure > chicken manure > rice straw. The Cd contents of brown rice, stem and leaf in the treatment applied with pig manure were lower than in the control by 37.5%, 44.0% and 36.4%, respectively; the Cd contents of brown rice, stem and leaf in the treatment applied with chicken manure were lower than in the control by 22.5%, 33.8%, and 22.7%, respectively; the Cd content of brown rice in the treatment applied with rice straw was lower than in the control by 7.5% but its contents in stem and leaf increased by 8.2% and 22.7% , respectively. The reduction in the brown rice Cd content was mainly due to the reduction of Cd enrichment from soil to brown rice after application of pig or chicken manure, but mainly due to the reduction of Cd transportation from stem to brown rice after straw application. Applications of pig manure, chicken manure and rice straw increased Zn contents in rice stem by 53.4%, 53.4% and 13.9%, respectively, but all had no significant effect on brown rice and leaf' s Zn contents. Zn and Cd had the significant antagonistic effects in the soil and rice stem. The increase of Zn content in soil and rice stem inhibited the adsorption and accumulation of Cd in the brown rice, stem and leaf significantly, and with the increase of the proportion of Zn/Cd, the

CdTe quantum-dot-modified ZnO nanowire heterostructure

NASA Astrophysics Data System (ADS)

Shahi, Kanchana; Singh, R. S.; Singh, Ajaya Kumar; Aleksandrova, Mariya; Khenata, Rabah

2018-03-01

The effect of CdTe quantum-dot (QD) decoration on the photoluminescence (PL) behaviour of ZnO nanowire (NW) array is presented in the present work. Highly crystalline and vertically 40-50 nm diameter range and 1 µm in length aligned ZnO NWs are synthesized using low-cost method. The crystallinity and morphology of the NWs are studied by scanning electron microscopy and X-ray powder diffraction methods.Optical properties of the nanowires are studied using photo-response and PL spectroscopy. CdTe QDs are successfully synthesized on ZnO nanowire surface by dip-coating method. ZnO NWs are sensitized with CdTe QDs characterized by transmission electron microscopy, energy-dispersive X-ray spectroscopy, and PL spectroscopy. The highly quenched PL intensity indicates the charge transfer at interface between CdTe QDs and ZnO NWs and is due to the formation of type-II heterostructure between QDs and NWs. Photo-response behaviour of heterostructure of the film is also been incorporated in the present work.

``Flash'' synthesis of ``giant'' Mn-doped CdS/ZnSe/ZnS nanocrystals with ZnSe layer as hole quantum-well

NASA Astrophysics Data System (ADS)

Xu, Ruilin; Zhang, Jiayu

Usually, exciton-Mn energy transfer in Mn-doped CdS/ZnS nanocrystals (NCs) can readily outcompete the exciton trapping by an order of magnitude. However, with the accumulation of non-radiative defects in the giant shell during the rapid growth of the thick shell (up to ~20 monolayers in no more than 10 minutes), the photoluminescence (PL) quantum yield of this kind of ``giant'' NCs is significantly reduced by the accumulation of non-radiative defects during the rapid growth of thick shell. That is because the exciton-Mn energy transfer in Mn-doped CdS/ZnS NCs is significantly inhibited by the hole trapping as the major competing process, resulting from the insufficient hole-confinement in CdS/ZnS NCs. Accordingly ``flash'' synthesis of giant Mn-doped CdS/ZnSe/ZnS NCs with ZnSe layer as hole quantum-well is developed to suppress the inhibition. Meanwhile Mn2+ PL peak changes profoundly from ~620 nm to ~540 nm after addition of ZnSe layer. Studies are under the way to explore the relevant mechanisms.

CdZnTe Background Measurements at Balloon Altitudes with PoRTIA

NASA Technical Reports Server (NTRS)

Parsons, A.; Barthelmy, S.; Bartlett, L.; Gehrels, N.; Naya, J.; Stahle, C. M.; Tueller, J.; Teegarden, B.

2003-01-01

Measurements of the CdZnTe internal background at balloon altitudes are essential to determine which physical processes make the most important background contributions. We present results from CdZnTe background measurements made by PoRTIA, a small CdZnTe balloon instrument that was flown three times in three different shielding configurations. PoRTIA was passively shielded during its first flight from Palestine, Texas and actively shielded as a piggyback instrument on the GRIS balloon experiment during its second and third flights from Alice Springs, Australia, using the thick GRIS Nal anticoincidence shield. A significant CdZnTe background reduction was achieved during the third flight with PoRTIA placed completely inside the GRIS shield and blocking crystal, and thus completely surrounded by 15 cm of Nal. A unique balloon altitude background data set is provided by CdZnTe and Ge detectors simultaneously surrounded by the same thick anticoincidence shield; the presence of a single coxial Ge detector inside the shield next to PoRTIA allowed a measurement of the ambient neutron flux inside the shield throughout the flight. These neutrons interact with the detector material to produce isomeric states of the Cd, Zn and Te nuclei that radiatively decay; calculations are presented that indicate that these decays may explain most of the fully shielded CdZnTe background.

ZnO/Sn:In2O3 and ZnO/CdTe band offsets for extremely thin absorber photovoltaics

NASA Astrophysics Data System (ADS)

Kaspar, T. C.; Droubay, T.; Jaffe, J. E.

2011-12-01

Band alignments were measured by x-ray photoelectron spectroscopy for thin films of ZnO on polycrystalline Sn:In2O3 (ITO) and single crystal CdTe. Hybrid density functional theory calculations of epitaxial zinc blende ZnO(001) on CdTe(001) were performed to compare with experiment. A conduction band (CB) offset of -0.6 eV was measured for ZnO/ITO, which is larger than desired for efficient electron injection. For ZnO/CdTe, the experimental conduction band offset of 0.25 eV is smaller than the calculated value of 0.67 eV, possibly due to the TeOx layer at the ZnO/CdTe interface. The measured conduction band offset for ZnO/CdTe is favorable for photovoltaic devices.

White HDPE bottles as source of serious contamination of water samples with Ba and Zn.

PubMed

Reimann, Clemens; Grimstvedt, Andreas; Frengstad, Bjørn; Finne, Tor Erik

2007-03-15

During a recent study of surface water quality factory new white high-density polyethylene (HDPE) bottles were used for collecting the water samples. According to the established field protocol of the Geological Survey of Norway the bottles were twice carefully rinsed with water in the field prior to sampling. Several blank samples using milli-Q (ELGA) water (>18.2 MOmega) were also prepared. On checking the analytical results the blanks returned values of Ag, Ba, Sr, V, Zn and Zr. For Ba and Zn the values (c. 300 microg/l and 95 microg/l) were about 10 times above the concentrations that can be expected in natural waters. A laboratory test of the bottles demonstrated that the bottles contaminate the samples with significant amounts of Ba and Zn and some Sr. Simple acid washing of the bottles prior to use did not solve the contamination problem for Ba and Zn. The results suggest that there may exist "clean" and "dirty" HDPE bottles depending on manufacturer/production process. When collecting water samples it is mandatory to check bottles regularly as a possible source of contamination.

Characterisation of Redlen high-flux CdZnTe

NASA Astrophysics Data System (ADS)

Thomas, B.; Veale, M. C.; Wilson, M. D.; Seller, P.; Schneider, A.; Iniewski, K.

2017-12-01

CdZnTe is a promising material for the current generation of free electron laser light sources and future laser-driven γ-ray sources which require detectors capable of high flux imaging at X-ray and γ-ray energies (> 10 keV) . However, at high fluxes CdZnTe has been shown to polarise due to hole trapping, leading to poor performance. Novel Redlen CdZnTe material with improved hole transport properties has been designed for high flux applications. Small pixel CdZnTe detectors were fabricated by Redlen Technologies and flip-chip bonded to PIXIE ASICs. An XIA Digital Gamma Finder PIXIE-16 system was used to digitise each of the nine analogue signals with a timing resolution of 10 ns. Pulse shape analysis was used to extract the rise times and amplitude of signals. These were measured as a function of applied bias voltage and used to calculate the mobility (μ) and mobility-lifetime (μτ) of electrons and holes in the material for three identical detectors. The measured values of the transport properties of electrons in the high-flux-capable material was lower than previously reported for Redlen CdZnTe material (μeτe ~ 1 × 10-3 cm2V-1 and μe ~ 1000 cm2V-1s-1) while the hole transport properties were found to have improved (μhτh ~ 3 × 10-4 cm2V-1 and μh ~ 100 cm2V-1s-1).

Optical properties of ZnO/BaCO3 nanocomposites in UV and visible regions.

PubMed

Zak, Ali Khorsand; Hashim, Abdul Manaf; Darroudi, Majid

2014-01-01

Pure zinc oxide and zinc oxide/barium carbonate nanoparticles (ZnO-NPs and ZB-NPs) were synthesized by the sol-gel method. The prepared powders were characterized by X-ray diffraction (XRD), ultraviolet-visible (UV-Vis), Auger spectroscopy, and transmission electron microscopy (TEM). The XRD result showed that the ZnO and BaCO3 nanocrystals grow independently. The Auger spectroscopy proved the existence of carbon in the composites besides the Zn, Ba, and O elements. The UV-Vis spectroscopy results showed that the absorption edge of ZnO nanoparticles is redshifted by adding barium carbonate. In addition, the optical parameters including the refractive index and permittivity of the prepared samples were calculated using the UV-Vis spectra. 81.05.Dz; 78.40.Tv; 42.70.-a.

Elucidation of Two Giants: Challenges to Thick-shell Synthesis in CdSe/ZnSe and ZnSe/CdS Core/Shell Quantum Dots

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

Acharya, Krishna P.; Nguyen, Hue M.; Paulite, Melissa

2015-03-06

Core/thick-shell "giant" quantum dots (gQDs) possessing type II electronic structures exhibit suppressed blinking and diminished nonradiative Auger recombination. Here we investigate CdSe/ZnSe and ZnSe/CdS as potential new gQDs. We show theoretically and experimentally that both can exhibit partial or complete spatial separation of an excited-state electron–hole pair (i.e., type II behavior). However, we reveal that thick-shell growth is challenged by competing processes: alloying and cation exchange. We demonstrate that these can be largely avoided by choice of shelling conditions (e.g., time, temperature, and QD core identity). The resulting CdSe/ZnSe gQDs exhibit unusual single-QD properties, principally emitting from dim gray statesmore » but having high two-exciton (biexciton) emission efficiencies, whereas ZnSe/CdS gQDs show characteristic gQD blinking suppression, though only if shelling is accompanied by partial cation exchange.« less

Synthesis and characterization of Cd Cr and Zn Cd Cr layered double hydroxides intercalated with dodecyl sulfate

NASA Astrophysics Data System (ADS)

Guo, Ying; Zhang, He; Zhao, Lan; Li, Guo-Dong; Chen, Jie-Sheng; Xu, Lin

2005-06-01

Cd-Cr and Zn-Cd-Cr layered double hydroxides (CdCr-LDH and ZnCdCr-LDH) containing alkyl sulfate as the interlamellar anion have been prepared through a coprecipitation technique. The resulting compounds were characterized using X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy. Magnetic property measurements indicate that antiferromagnetic interactions occur between the chromium ions in the two compounds at low temperatures. The introduction of zinc influences the ligand field of Cr III and the Cr III-Cr III interactions in the LDH compound. It is found that both CdCr-LDH and ZnCdCr-LDH can be delaminated by dispersion in formamide, leading to translucent and stable colloidal solutions.

Surface tension modelling of liquid Cd-Sn-Zn alloys

NASA Astrophysics Data System (ADS)

Fima, Przemyslaw; Novakovic, Rada

2018-06-01

The thermodynamic model in conjunction with Butler equation and the geometric models were used for the surface tension calculation of Cd-Sn-Zn liquid alloys. Good agreement was found between the experimental data for limiting binaries and model calculations performed with Butler model. In the case of ternary alloys, the surface tension variation with Cd content is better reproduced in the case of alloys lying on vertical sections defined by high Sn to Zn molar fraction ratio. The calculated surface tension is in relatively good agreement with the available experimental data. In addition, the surface segregation of liquid ternary Cd-Sn-Zn and constituent binaries has also been calculated.

Properties of a CdZnO/ZnO multiple quantum-well light-emitting diode

NASA Astrophysics Data System (ADS)

Liu, Zhan-Hui; Zhang, Li-Li; Li, Qing-Fang; Zhang, Rong; Xie, Zi-Li; Xiu, Xiang-Qian; Liu, Bin

2016-10-01

A CdZnO/ZnO multiple quantum-well light-emitting diode (LED) structure was successfully grown by using plasma-assisted molecular beam epitaxy on a p-GaN template that had been grown by using metal-organic chemical-vapor deposition on a c-sapphire substrate. The properties of the sample were characterized by using high-resolution X-ray diffraction, transmission electron microscopy, and temperature-dependent photoluminescence measurements. The light output performance of the CdZnO/ZnO QW LED device was also investigated in detail by using I-V and electroluminescence spectral measurements. The characterization showed that our CdZnO/ZnO QW LED structure had good crystalline quality and weaker carrier localization. Owing to the heterojunction structure, the I-V curve indicated that the LED device had a higher turn-on voltage and series resistance. The EL measurement demonstrated that for our LED device's optoelectronic characteristic, the carrier-screening effect played the dominant role in the emission-energy blue-shift mechanism, and the broadening of the emission energy width was mainly ascribed to the band-filling effect. Without a special heat sinking, the L-I curve exhibited slight efficiency droop after 30 mA.

Formation of highly luminescent Zn1-xCdxSe nanocrystals using CdSe and ZnSe seeds

NASA Astrophysics Data System (ADS)

Zhang, Ruili; Yang, Ping

2013-05-01

High-quality colloidal Zn1-xCdxSe nanocrystals (NCs) with tunable photoluminescence (PL) from blue to orange were synthesized using oleic acid as a capping agent. The Zn1-xCdxSe NCs were prepared through two approaches: using CdSe or ZnSe seeds. In the case of CdSe NCs as seeds, Zn1-xCdxSe NCs were fabricated by the reaction of Zn, Cd, and Se precursors in the coordinating solvent system at high temperature. The Zn1-xCdxSe NCs revealed orange emitting. A significant blue-shift of absorption and PL spectra were observed with time, indicating the formation of ternary NCs. In contrast, Zn1-xCdxSe NCs revealed blue to green PL for ZnSe NCs as seeds. This is ascribed to an embryonic nuclei-induced alloying process. With increasing time, the Zn1-xCdxSe NCs exhibited a red-shift both in their absorption and PL spectra. This is attributed to the engineering in band gap energy via the control of NC composition. The PL properties of as-prepared alloyed NCs are comparable or even better than those for the parent binary systems. The PL peak wavelength of the Zn1-xCdxSe NCs depended strongly on reaction time and the molar ratio of Cd/Zn. The Zn1-xCdxSe NCs revealed a spherical morphology and exhibited a wurtzite structure according to transmission electron microscopy observation and an X-ray diffraction analysis.

HRTEM Analysis of Crystallographic Defects in CdZnTe Single Crystal

NASA Astrophysics Data System (ADS)

Yasar, Bengisu; Ergunt, Yasin; Kabukcuoglu, Merve Pinar; Parlak, Mehmet; Turan, Rasit; Kalay, Yunus Eren

2018-01-01

In recent years, CdZnTe has attracted much attention due to its superior electrical and structural properties for room-temperature operable gamma and x-ray detectors. However, CdZnTe (CZT) material has often suffered from crystallographic defects encountered during the growth and post-growth processes. The identification and structural characterization of these defects is crucial to synthesize defect-free CdZnTe single crystals. In this study, Cd0.95 Zn0.05 Te single crystals were grown using a three-zone vertical Bridgman system. The single crystallinity of the material was ensured by using x-ray diffraction measurements. High-resolution electron microscopy (HRTEM) was used to characterize the nano-scale defects on the CdZnTe matrix. The linear defects oriented along the ⟨211⟩ direction were examined by transmission electron microscopy (TEM) and the corresponding HRTEM image simulations were performed by using a quantitative scanning TEM simulation package.

Cluster Chemistry in Electron-Poor Ae-Pt-Cd Systems (Ae=Ca, Sr, Ba): (Sr,Ba)Pt2Cd4, Ca6Pt8Cd16, and Its Known Antitype Er6Pd16Sb8

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

Samal, Saroj L.; Gulo, Fakhili; Corbett, John D.

Three new ternary polar intermetallic compounds, cubic Ca6Pt8Cd16, and tetragonal (Sr, Ba)Pt2Cd4 have been discovered during explorations of the Ae–Pt–Cd systems. Cubic Ca6Pt8Cd16 (Fm-3m, Z = 4, a = 13.513(1) Å) contains a 3D array of separate Cd8 tetrahedral stars (TS) that are both face capped along the axes and diagonally bridged by Pt atoms to generate the 3D anionic network Cd8[Pt(1)]6/2[Pt(2)]4/8. The complementary cationic surface of the cell consists of a face-centered cube of Pt(3)@Ca6 octahedra. This structure is an ordered ternary variant of Sc11Ir4 (Sc6Ir8Sc16), a stuffed version of the close relative Na6Au7Cd16, and a network inverse ofmore » the recent Er6Sb8Pd16 (compare Ca6Pt8Cd16). The three groups of elements each occur in only one structural version. The new AePt2Cd4, Ae = Sr, Ba, are tetragonal (P42/mnm,Z = 2, a ≈ 8.30 Å, c ≈ 4.47 Å) and contain chains of edge-sharing Cd4 tetrahedra along c that are bridged by four-bonded Ba/Sr. LMTO-ASA and ICOHP calculation results and comparisons show that the major bonding (Hamilton) populations in Ca6Pt8Cd16 and Er6Sb8Pd16 come from polar Pt–Cd and Pd–Sb interactions, that Pt exhibits larger relativistic contributions than Pd, that characteristic size and orbital differences are most evident for Sb 5s, Pt8, and Pd16, and that some terms remain incomparable, Ca–Cd versus Er–Pd.« less

Zn2+ in-situ substitution behavior during the formation of BaTiO3 coatings from plasma-sprayed powders collected in liquid nitrogen

NASA Astrophysics Data System (ADS)

Liu, Zhe; Xing, Zhiguo; Wang, Haidou; Xue, Zifan; Chen, Shuying; Cui, Xiufang; Jin, Guo

2018-04-01

The dielectric performance of BaTiO3 ceramic coatings is enhanced significantly by the addition of ZnO. In this study, the maximum relative permittivity value (εr ≈ 923) was measured in BaTiO3 coatings with ZnO added at 6 wt%. The Curie temperature (Tc) was in the range of 111 °C-121 °C for all of the ZnO-modified BaTiO3 coatings. Tc shifted to low temperatures as the ZnO content increased. Detailed analyses were performed to determine the phase composition and optical band gaps of powders collected in liquid nitrogen, which showed that the Zn2+ ions were incorporated into the BaTiO3 lattice where they substituted into the Ti4+ sites, and the composite powders (BaTiO3 + 6 wt% ZnO) tolerated high temperatures in the plasma beam. In addition, some residual Zn accumulated in the grain boundary in the form of ZnO. X-ray diffraction and Raman spectroscopy showed that the substitution led to changes in the compositional and structural properties. The red shift in the optical band gap of BaTiO3 indicated that the ZnTi'' defects caused by the dopants acted as carriers in the doped BaTiO3 coatings.

Proteomic Profiling of the Interactions of Cd/Zn in the Roots of Dwarf Polish Wheat (Triticum polonicum L.)

PubMed Central

Wang, Yi; Wang, Xiaolu; Wang, Chao; Wang, Ruijiao; Peng, Fan; Xiao, Xue; Zeng, Jian; Fan, Xing; Kang, Houyang; Sha, Lina; Zhang, Haiqin; Zhou, Yonghong

2016-01-01

Cd and Zn have been shown to interact antagonistically or synergistically in various plants. In the present study of dwarf polish wheat (DPW)roots, Cd uptake was inhibited by Zn, and Zn uptake was inhibited by Cd, suggesting that Cd and Zn interact antagonistically in this plant. A study of proteomic changes showed that Cd, Zn, and Cd+Zn stresses altered the expression of 206, 303, and 190 proteins respectively. Among these, 53 proteins were altered significantly in response to all these stresses (Cd, Zn, and Cd+Zn), whereas 58, 131, and 47 proteins were altered in response to individual stresses (Cd, Zn, and Cd+Zn, respectively). Sixty-one differentially expressed proteins (DEPs) were induced in response to both Cd and Zn stresses; 33 proteins were induced in response to both Cd and Cd+Zn stresses; and 57 proteins were induced in response to both Zn and Cd+Zn stresses. These results indicate that Cd and Zn induce differential molecular responses, which result in differing interactions of Cd/Zn. A number of proteins that mainly participate in oxidation-reduction and GSH, SAM, and sucrose metabolisms were induced in response to Cd stress, but not Cd+Zn stress. This result indicates that these proteins participate in Zn inhibition of Cd uptake and ultimately cause Zn detoxification of Cd. Meanwhile, a number of proteins that mainly participate in sucrose and organic acid metabolisms and oxidation-reduction were induced in response to Zn stress but not Cd+Zn stress. This result indicates that these proteins participate in Cd inhibition of Zn uptake and ultimately cause the Cd detoxification of Zn. Other proteins induced in response to Cd, Zn, or Cd+Zn stress, participate in ribosome biogenesis, DNA metabolism, and protein folding/modification and may also participate in the differential defense mechanisms. PMID:27683584

Nonlinear optical properties of hybridized CdS/ZnS-PVP sols

NASA Astrophysics Data System (ADS)

Kulagina, A. S.; Evstropiev, S. K.; Khrebtov, A. I.

2017-11-01

Hybrid composites of CdS-core ZnS-shell nanoparticles embedded in polyvinylpyrrolidone (PVP) matrixes have been prepared and characterized. Cadmium sulfide (CdS) nanocrystals were grown in water-propanol-2 solutions containing high-molecular (Ms=1300000) polyvinylpyrrolidone (PVP) at room temperature using cadmium nitrate and sodium sulfide as the cadmium and sulfur sources, respectively. The CdS/ZnS-PVP suspensions have promising optical properties for nanocomposite films based on. Nonlinear optical properties of diluted CdS/ZnS sols were studied at 532 nm and 5 ns laser pulses by using the Z-scan technique. Dependence of the nonlinear-optical coefficients on the CdS weight has been obtained.

The quadrupole moments of Cd and Zn isotopes - an apology

NASA Astrophysics Data System (ADS)

Haas, H.; Barbosa, M. B.; Correia, J. G.

2016-12-01

In 2010 we presented an update of the nuclear quadrupole moments (Q) for the Cd and Zn isotopes, based essentially on straightforward density functional (DF) calculations (H. Haas and J.G. Correia, Hyperfine Interact 198, 133-137 (2010)). It has been apparent for some years that the standard DF procedure obviously fails, however, to reproduce the known electric-field gradient (EFG) for various systems, typical cases being Cu2O, As and Sb, and the solid halogens. Recently a cure for this deficiency has been found in the hybrid DF technique. This method is now applied to solid Cd and Zn, and the resultant quadrupole moments are about 15 % smaller than in our earlier report. Also nuclear systematics, using the recently revised values of Q for the long-lived 11/2 isomers in111Cd to129Cd, together with earlier PAD data for107,109Cd, leads to the same conclusion. In addition, EFG calculations for the cadmium dimethyl molecule further support the new values: Q(111Cd, 5/2+) = .683(20) b, Q(67Zn, gs) = .132(5) b. This implies, that the value for the atomic EFG in the 3it {P}1 state of Zn must be revised, as it has been for Cd.

Study on the effect of Cd-diffusion annealing on the electrical properties of CdZnTe

NASA Astrophysics Data System (ADS)

Wanwan, Li; Zechun, Cao; Bin, Zhang; Feng, Zhan; Hongtao, Liu; Wenbin, Sang; Jiahua, Min; Kang, Sun

2006-06-01

In order to meet the requirements for the device design of radiation detectors, CdZnTe (or Cd 1-xZn xTe) crystals grown by Vertical Bridgman Method often need subsequent annealing to increase their resistivity. The nature of this treatment is a diffusion process. Thus, it is meaningful to relate the change of resistivity to the diffusion parameters. A model correlating resistivity and conduction type of CdZnTe with the main diffusion parameter—diffusion coefficient—is put forward in this paper. Combining the model with the analysis of our experimental data, DCd=1.464×10 -10, 1.085×10 -11 and 4.167×10 -13 cm 2/s are the values of Cd self-diffusion coefficient in Cd 0.9Zn 0.1Te at 1073, 973 and 873 K, respectively. The data coincide closely with the Cd self-diffusion coefficient in CdTe provided by different authors [E.D. Jones, N.M. Stewart, Self-diffusion of cadmium in cadmium telluride, J. Crystal Growth 84 (1987) 289-294; P.M. Borsenberger, D.A. Stevenson, J. Phys. Chem. Solids 29 (1968) 1277; R.C. Whelan, D. Shaw, in: D.G. Thomas (Ed.), II -VI Semiconductor Compounds, Benjamin, New York, 1967, p. 451]. With the data, the effects of annealing time on the change of resistivity and conduction type for Cd 0.9Zn 0.1Te wafers, which are annealed in saturated Cd vapor at 1073, 973 and 873 K, were simulated, and good consistency was found. This work suggests an alternative way to obtain the diffusion coefficient in semiconductor materials and also enables ones to analyze the diffusion process quantitatively and predict the annealing results.

Spectroscopic ellipsometry studies on ZnCdO thin films with different Cd concentrations grown by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Chen, Shuai; Li, Qingxuan; Ferguson, Ian; Lin, Tao; Wan, Lingyu; Feng, Zhe Chuan; Zhu, Liping; Ye, Zhizhen

2017-11-01

A set of Zn1-xCdxO thin films with different Cd concentrations was deposited on quartz substrates by Pulsed Laser Deposition (PLD). The properties of these films were investigated by variable angle and temperature dependent spectroscopic ellipsometry (SE). The experimental Zn1-xCdxO thin films showed a red shift in the absorption edge with increasing Cd contents at room temperature. For ZnCdO films with the similar Cd concentration, it has been found that the film thickness has important effects on the optical constants (n, k). The variations of optical constants (n, k) and the band gap, E0, with temperature (T) in 25 °C-600 °C for a typical Zn0.95Cd0.05O sample were obtained. The E0 vs T relationship is described by a T- quadratic equation.

Lack of Zn inhibition of Cd accumulation by rice (Oryza sativa L.) supports non-Zn transporter uptake of Cd

USDA-ARS?s Scientific Manuscript database

Rice (Oryza sativa L.) grown on Cd contaminated soils has been linked to health problems in subsistence rice farmers in Japan and China. For other crops, normal geogenic Zn inhibits the increased uptake of Cd on contaminated soils. A study was conducted using a multi-chelator buffered nutrient sol...

Divalent metal (Ca, Cd, Mn, Zn) uptake and interactions in the aquatic insect Hydropsyche sparna.

PubMed

Poteat, Monica D; Díaz-Jaramillo, Mauricio; Buchwalter, David B

2012-05-01

Despite their ecological importance and prevalent use as ecological indicators, the trace element physiology of aquatic insects remains poorly studied. Understanding divalent metal transport processes at the water-insect interface is important because these metals may be essential (e.g. Ca), essential and potentially toxic (e.g. Zn) or non-essential and toxic (e.g. Cd). We measured accumulation kinetics of Zn and Cd across dissolved concentrations ranging 4 orders of magnitude and examined interactions with Ca and Mn in the caddisfly Hydropsyche sparna. Here, we provide evidence for at least two transport systems for both Zn and Cd, the first of which operates at concentrations below 0.8 μmol l(-1) (and is fully saturable for Zn). We observed no signs of saturation of a second lower affinity transport system at concentrations up to 8.9 μmol l(-1) Cd and 15.3 μmol l(-1) Zn. In competition studies at 0.6 μmol l(-1) Zn and Cd, the presence of Cd slowed Zn accumulation by 35% while Cd was unaffected by Zn. At extreme concentrations (listed above), Cd accumulation was unaffected by the presence of Zn whereas Zn accumulation rates were reduced by 58%. Increasing Ca from 31.1 μmol l(-1) to 1.35 mmol l(-1) resulted in only modest decreases in Cd and Zn uptake. Mn decreased adsorption of Cd and Zn to the integument but not internalization. The L-type Ca(2+) channel blockers verapamil and nifedipine and the plasma membrane Ca(2+)-ATPase inhibitor carboxyeosin had no influence on Ca, Cd or Zn accumulation rates, while Ruthenium Red, a Ca(2+)-ATPase inhibitor, significantly decreased the accumulation of all three in a concentration-dependent manner.

Atomistic tight-binding computations of the structural and optical properties of CdTe/CdX (X=S and Se)/ZnS core/shell/shell nanocrystals

NASA Astrophysics Data System (ADS)

Sukkabot, Worasak

2018-05-01

A study of CdTe/CdX (X=S and Se)/ZnS core/shell/shell nanocrystals is carried out using atomistic tight-binding theory and the configuration interaction method to provide information for applications in bioimaging, biolabeling, display devices and near-infrared electronic instruments. The calculations yield the dependences of the internal and external passivated shells on the natural behaviours of CdTe/CdX (X=S and Se)/ZnS core/shell/shell nanocrystals. The reduction of the optical band gaps is observed with increasing numbers of monolayers in the external ZnS shell due to quantum confinement. Interestingly, the optical band gaps of CdTe/CdS/ZnS core/shell/shell nanocrystals are greater than those of CdTe/CdSe/ZnS core/shell/shell nanocrystals. In the presence of an external ZnS-coated shell, electron-hole wave function overlaps, oscillation strengths, ground-state exchange energies and Stokes shift are improved, whereas ground-state coulomb energies and fine-structure splitting are reduced. The oscillation strengths, Stokes shift and fine-structure splitting are reduced with the increase in external ZnS shell thickness. The oscillation strengths, Stokes shift and fine-structure splitting of CdTe/CdS/ZnS core/shell/shell nanocrystals are larger than those of CdTe/CdSe/ZnS core/shell/shell nanocrystals. Reduction of the atomistic electron-hole interactions is observed with increasing external ZnS shell size. The strong electron-hole interactions are more probed in CdTe/CdS/ZnS core/shell/shell nanocrystals than in CdTe/CdSe/ZnS core/shell/shell nanocrystals.

On the response of alloyed ZnCdSeS quantum dot films

NASA Astrophysics Data System (ADS)

Valais, I.; Michail, C.; Fountzoula, C.; Tseles, D.; Yannakopoulos, P.; Nikolopoulos, D.; Bakas, A.; Fountos, G.; Saatsakis, G.; Sianoudis, I.; Kandarakis, I.; Panayiotakis, G.

The aim of this work was to prepare composite ZnCdSeS quantum dot (QD) flexible films and to examine their optical properties under ultraviolet excitation. PMMA/QD ZnCdSeS composite films, with emission covering the visual spectrum (480-630 nm) were prepared with concentrations 10 mg/mL and 20 mg/mL by homogenously diluting dry powder QD samples in toluene and subsequently mixing with a PMMA/MMA polymer solution to the final ZnCdSeS/Toluene mixture. Scanning electron microscopy (SEM) images of the produced films were obtained. The ZnCdSeS films were excited by ultraviolet light of varying intensities and the spectral matching with various optical detectors was estimated.

Characterization and Luminescence Properties of Color-Tunable Dy3+-Doped BaY2ZnO5 Nanophosphors

NASA Astrophysics Data System (ADS)

Sonika; Khatkar, S. P.; Khatkar, Avni; Kumar, Rajesh; Taxak, V. B.

2015-01-01

Dy3+-doped BaY2ZnO5 nanophosphors were successfully synthesized by use of a solution combustion process. The effects of sintering temperature and dysprosium concentration on the structural and luminescence characteristics of the phosphors were investigated. X-ray diffraction (XRD) analysis confirmed the formation of pure orthorhombic BaY2ZnO5 with the space group Pbnm at 1100°C. Morphological investigation revealed spherical nanoparticles with smooth surfaces. The luminescence features of the nanophosphor were studied by use of photoluminescence excitation (PLE) and photoluminescence emission (PL), with luminescence decay curves and color ( x, y) coordinates. On excitation at 355 nm, BaY2ZnO5 nanophosphor doped with trivalent dysprosium ion emits white light as a mixture of blue (4F9/2 → 6H15/2) and yellow (4F9/2 → 6H13/2) emission. Concentration quenching is explained on the basis of cross-relaxation between intermediate Dy3+ states. Thus, BaY2ZnO5:Dy3+ nanophosphor may be suitable for producing efficient white light for ultraviolet-light-emitting diodes (UV-LEDs), fluorescent lamps, and a variety of optical display panels.

Sol–gel synthesis, structure and luminescence properties of Ba{sub 2}ZnMoO{sub 6}:Eu{sup 3+} phosphors

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

Li, Yuntong; Liu, Xiaohua, E-mail: xhliuxhliu@tom.com

2015-04-15

Graphical abstract: The phosphor powders of Ba{sub 2}ZnMoO{sub 6}:Eu{sup 3+} were prepared by sol–gel method. The dependence of luminescence intensity on the Eu{sup 3+} concentration was investigated. - Highlights: • We synthesize Ba{sub 2}ZnMoO{sub 6}:Eu{sup 3+} phosphors by the sol–gel method. • The effect of temperature on the crystallinity and morphology is investigated. • The phosphor presents an intense CT band in near UV range (370–410 nm). • The concentration quenching mechanism is the exchange interaction. - Abstract: Double-perovskite Ba{sub 2}Zn{sub 1−x}MoO{sub 6}:xEu{sup 3+} (x = 0, 0.02, 0.04, 0.06, 0.08, 0.1) orange–red emitting phosphors were synthesized by using themore » sol–gel method. The crystalline structure and photoluminescence properties of the phosphors were investigated. The X-ray diffraction (XRD) patterns indicate that the structure of matrix Ba{sub 2}ZnMoO{sub 6} is cubic double-perovskite with space group Fm-3m. The Ba{sub 2}ZnMoO{sub 6}:Eu{sup 3+} phosphors present an intense broad charge transfer (CT) band absorption in near UV range (370–410 nm), which attributes to the charge transfer state of MoO{sub 6}, and performs orange–red emission of Eu{sup 3+} ({sup 5}D{sub 0} → {sup 7}F{sub 1} transition) at around 596 nm. A low concentration quenching occurs in Ba{sub 2}ZnMoO{sub 6}:Eu{sup 3+} and the optimal doping concentration is about 6 mol%. The Ba{sub 2}ZnMoO{sub 6}:Eu{sup 3+} phosphors are considered to be a promising orange–red emitting phosphor for near ultraviolet GaN-based white light emitting diode.« less

Study of extending carrier lifetime in ZnTe quantum dots coupled with ZnCdSe quantum well

NASA Astrophysics Data System (ADS)

Fan, W. C.; Chou, W. C.; Lee, J. D.; Lee, Ling; Phu, Nguyen Dang; Hoang, Luc Huy

2018-03-01

We demonstrated the growth of a self-assembled type-II ZnTe/ZnSe quantum dot (QD) structure coupled with a type-I Zn0.88Cd0.12Se/ZnSe quantum well (QW) on the (001) GaAs substrate by molecular beam epitaxy (MBE). As the spacer thickness is less than 2 nm, the carrier lifetime increasing from 20 ns to nearly 200 ns was successfully achieved. By utilizing the time-resolved photoluminescence (TRPL) and PL with different excitation power, we identify the PL emission from the coupled QDs consisting of two recombination mechanisms. One is the recombination between electrons in ZnSe barrier and holes confined within ZnTe QDs, and the other is between electrons confined in Zn0.88Cd0.12Se QW and holes confined within ZnTe QDs. According to the band diagram and power-dependent PL, both of the two recombinations reveal the type-II transition. In addition, the second recombination mechanism dominates the whole carrier recombination as the spacer thickness is less than 2 nm. A significant extension of carrier lifetime by increasing the electron and hole separation is illustrated in a type-II ZnTe/ZnSe QD structure coupling with a type-I ZnCdSe/ZnSe QW. Current sample structure could be used to increase the quantum efficient of solar cell based on the II-VI compound semiconductors.

New ternary phosphides and arsenides. Syntheses, crystal structures, physical properties of Eu{sub 2}ZnP{sub 2}, Eu{sub 2}Zn{sub 2}P{sub 3} and Eu{sub 2}Cd{sub 2}As{sub 3}

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

Wang, Jian; Xia, Sheng-Qing, E-mail: shqxia@sdu.edu.cn; Tao, Xu-Tang

2013-09-15

Three new europium pnictides Eu{sub 2}ZnP{sub 2}, Eu{sub 2}Zn{sub 2}P{sub 3} and Eu{sub 2}Cd{sub 2}As{sub 3} have been synthesized and their structures were determined by single-crystal X-ray diffraction. Eu{sub 2}ZnP{sub 2} is isotypic with Yb{sub 2}CdSb{sub 2} (Cmc2{sub 1} (No. 36); cell parameters a=4.1777(7) Å, b=15.925(3) Å, c=7.3008(12) Å), while the latter two compounds crystallize with the Ba{sub 2}Cd{sub 2}Sb{sub 3} structure type (C2/m (No. 12); cell parameters a=15.653(5)/16.402(1) Å, b=4.127(1)/4.445(4) Å, c=11.552(4)/12.311(1) Å and β=126.647(4)/126.515(7)° for Eu{sub 2}Zn{sub 2}P{sub 3} and Eu{sub 2}Cd{sub 2}As{sub 3}, respectively). Magnetic susceptibility measurements in the interval 5–300 K confirm paramagnetic behavior and effectivemore » magnetic moments characteristic of Eu{sup 2+} ([Xe] 4f{sup 7}) ground states. Temperature-dependent electrical conductivity measurements also prove that Eu{sub 2}Cd{sub 2}As{sub 3} is a semiconducting compound with a narrow band gap of 0.059 eV below 100 K. According to TG/DSC analyses, Eu{sub 2}Cd{sub 2}As{sub 3} starts to decompose at about 950 K. - Graphical abstract: A polyhedral view of the crystal structure of new pnictides Eu{sub 2}T{sub 2}Pn{sub 3} (T=Zn or Cd; Pn=P or As). Display Omitted - Highlights: • Three new ternary pnictide Zintl compounds, Eu{sub 2}ZnP{sub 2}, Eu{sub 2}Zn{sub 2}P{sub 3} and Eu{sub 2}Cd{sub 2}As{sub 3}, have been synthesized and characterized. • The europium cations are divalent and ferromagnetically coupled in both Eu{sub 2}Zn{sub 2}P{sub 3} and Eu{sub 2}Cd{sub 2}As{sub 3}. • Eu{sub 2}Cd{sub 2}As{sub 3} has a very small band gap of 0.06 eV and starts to decompose over 950 K.« less

Tracing Cd, Zn and Pb pollution sources in bivalves using isotopes

NASA Astrophysics Data System (ADS)

Shiel, A. E.; Weis, D. A.; Orians, K. J.

2010-12-01

In a multi-tracer study, Cd, Zn and Pb isotopes (MC-ICP-MS) and elemental concentrations (HR-ICP-MS) are evaluated as tools to distinguish between natural and anthropogenic sources of these metals in bivalves from western Canada (British Columbia), the eastern USA, Hawaii and France. High Cd concentrations found in BC oysters have elicited economic and health concerns. The source of these high Cd levels is unknown but thought to be largely natural. High Cd levels in BC oysters are largely attributed to the natural upwelling of Cd-rich intermediate waters in the North Pacific as the δ114/110Cd (-0.69 to -0.09‰) and δ66/64Zn (0.28 to 0.36‰) values of BC oysters fall within the range reported for North Pacific seawater. Different contributions from anthropogenic sources account for the variability of Cd isotopic compositions of BC oysters; the lightest of these oysters are from the BC mainland. These oysters also have Pb isotopic compositions that reflect primarily anthropogenic sources (e.g., leaded and unleaded automotive gasoline and smelting of Pb ores, potentially historical). On the contrary, USA East Coast bivalves exhibit relatively light Cd isotopic compositions (δ114/110Cd = -1.20 to -0.54‰; lighter than reported for North Atlantic seawater) due to the high prevalence of industry on this coast. The Pb isotopic compositions of these bivalves indicate contributions from the combustion of coal. The large variability of environmental health among coastal areas in France is reflected in the broad range of Cd isotopic compositions exhibited by French bivalves (δ114/110Cd = -1.08 to -0.20‰). Oysters and mussels from the Marennes-Oléron basin and Gironde estuary have the lightest Cd isotopic compositions of the French oysters consistent with significant historical Cd emissions from the now-closed proximal Zn smelter. In these bivalves, significant declines in the Cd levels between 1984/7 and 2004/5 are not accompanied by a significant shift in the Cd

Synthesis, optical properties and efficient photocatalytic activity of CdO/ZnO hybrid nanocomposite

NASA Astrophysics Data System (ADS)

Reddy, Ch Venkata; Babu, B.; Shim, Jaesool

2018-01-01

Pure CdO, ZnO and CdO/ZnO hybrid nanocomposite photocatalyst were synthesized using simple co-precipitation technique and studied in detail. The synthesized photocatalysts were characterized using several measurements such as X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), surface analysis (BET), diffuse reflectance UV-vis spectroscopy, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, FT-IR, TG-DTA and photoluminescence (PL). The XRD results revealed that the hexagonal and cubic crystal structure of CdO and ZnO nanoparticles. The optical response for the composite showed the presence of separate absorption signature for CdO and ZnO in the visible region at about 510 nm and 360 nm respectively. The CdO/ZnO hybrid nanocomposite photocatalyst exhibited enhanced photocatalytic degradation activity compared to pristine CdO and ZnO. The enhanced photocatalytic activity may be due to the higher specific surface area and significantly reduced the electron-hole recombination rate.

Fabrication and characterization of Cu/sub 2/S-CdZnS solar cells. Final report. Realisation et caracterisation de cellules solaires Cu/sub 2/S-CdZnS

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

Cadene, M.

Thin films of Cd sub(1-y)Zn sub y S (0 < y < 0.2) have been prepared either by thermal evaporation of the powdered solids from a single crucible, or by rapid evaporation from two crucibles. Different methods were used to characterise the films according to their structural, electrical and electron-optical properties as a function of the amount of Zn in the film. Both liquid-phase and solid-phase ion exchange processes have been used to deposit a thin film of Cu/sub 2/S on the Cd sub(1-y)Zn sub y S film to produce a p-n hetero-junction. A study of the growth of themore » Cd/sub 2/S layer has been carried out. Photocurrents and voltages have been determined for these Cu/sub 2/S-CdZnS cells.« less

Electron Transport and Minority Carrier Lifetime in HgCdSe 2013 2-6 Workshop

DTIC Science & Technology

2014-03-11

FOR PUBLIC RELEASE Alternative IR Material 0.54 0.56 0.58 0.60 0.62 0.64 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 HgSe HgTe MgS ZnS MgTe CdS...CdSe ZnSe ZnTe CdTe AlP GaP AlSb InP Ge Si GaSb InSbInAs AlAs GaAs MgSe Ba nd ga p En er gy (e V) Lattice Constant (nm) • HgCdSe is being

Role of ZnO photoanode nanostructures and sensitizer deposition approaches on the photovoltaic properties of CdS/CdSe and CdS1-xSex quantum dot-sensitized solar cells

NASA Astrophysics Data System (ADS)

Şişman, İlkay; Tekir, Oktay; Karaca, Hüseyin

2017-02-01

Hierarchical bundle-like ZnO nanorod arrays (BNRs) were synthesized by a one-pot hydrothermal method based on two consecutive temperature steps for cascade CdS/CdSe and ternary CdS1-xSex alloy quantum dot-sensitized solar cells (QDSSCs) as photoanode. The CdS/CdSe and CdS1-xSex QDs were deposited on the surface of the ZnO BNRs by conventional and modified successive ionic-layer adsorption and reaction (SILAR) methods, respectively. Using the ZnO BNRs/CdS/CdSe photoanode, the power conversion efficiency reaches 2.08%, which is 1.8 times higher than that of pristine ZnO nanorods/CdS/CdSe photoanode, while by applying ZnO BNRs/CdS1-xSex, the power conversion efficiency improves 2.52%. The remarkably improved photovoltaic performance is mainly derived from the bundle-like nanorod arrays structure, which increases the QDs loading amount and the scattering effect for light absorption, and the appropriate conduction band energy, sufficient Se amount and well coverage of the ternary CdS1-xSex QDs result in enhanced photogenerated electron injection, high light absorption and reduced recombination, respectively. As a result, ZnO BNRs/CdS1-xSex combination can significantly improve performance of QDSSCs.

Theoretical Determination of Optimal Material Parameters for ZnCdTe/ZnCdSe Quantum Dot Intermediate Band Solar Cells

NASA Astrophysics Data System (ADS)

Imperato, C. M.; Ranepura, G. A.; Deych, L. I.; Kuskovsky, I. L.

2018-03-01

Intermediate band solar cells (IBSCs) are designed to enhance the photovoltaic efficiency significantly over that of a single-junction solar cell as determined by the Shockley-Queisser limit. In this work we present calculations to determine parameters of type-II Zn1-xCdxTe/Zn1-yCdySe quantum dots (QDs) grown on the InP substrate suitable for IBSCs. The calculations are done via the self-consistent variational method, accounting for the disk form of the QDs, presence of the strained ZnSe interfacial layer, and under conditions of a strain-free device structure. We show that to achieve the required parameters relatively thick QDs are required. Barriers must contain Cd concentration in the range of 35-44%, while Cd concentration in QD can vary widely from 0% to 70%, depending on their thickness to achieve the intermediate band energies in the range of 0.50-0.73 eV. It is also shown that the results are weakly dependent on the barrier thickness.

Microwave Characterization of Ba-Substituted PZT and ZnO Thin Films.

PubMed

Tierno, Davide; Dekkers, Matthijn; Wittendorp, Paul; Sun, Xiao; Bayer, Samuel C; King, Seth T; Van Elshocht, Sven; Heyns, Marc; Radu, Iuliana P; Adelmann, Christoph

2018-05-01

The microwave dielectric properties of (Ba 0.1 Pb 0.9 )(Zr 0.52 Ti 0.48 )O 3 (BPZT) and ZnO thin films with thicknesses below were investigated. No significant dielectric relaxation was observed for both BPZT and ZnO up to 30 GHz. The intrinsic dielectric constant of BPZT was as high as 980 at 30 GHz. The absence of strong dielectric dispersion and loss peaks in the studied frequency range can be linked to the small grain diameters in these ultrathin films.

Excitons emissions and Raman scattering of ZnO nanoparticles embedded in BaF2 matrices by reactive magnetron sputtering.

PubMed

Zang, C H; Su, J F; Liu, Y C; Tang, C J; Fang, S J; Zhang, D M; Zhang, Y S

2011-11-01

ZnO nanoparticles embedded in BaF2 matrix were fabricated by rf magnetic sputtering technology. The optical properties of high quality ZnO nanoparticles, thermally post treated in a N2 atmosphere, were investigated by temperature-dependence photoluminescence measurement. Free exciton and localized exciton were observed at the low temperature. Free exciton peak was at 3.374 eV and localized exciton peak was at 3.420 eV, dominating the PL spectrum at 77 K. Free exciton transition was observed at 3.310 eV at room temperature, whereas the localized exciton transition was at 3.378 eV. The multiple-phonon Raman scattering spectrum showed that ZnO nanoparticles embedded in BaF2 matrix had a large deformation energy originated from lattice mismatch between ZnO and BaF2 matrix. Analysis of the fitting results from the temperature dependence of FWHM of ZnO exciton illustrated that the large value of gamma(ph) was good qualitative agreement with the large deformation potential.

Up-conversion luminescence properties and energy transfer of Tm{sup 3+}/Yb{sup 3+} co-doped BaLa{sub 2}ZnO{sub 5}

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

Xie, Jing; Mei, Lefu, E-mail: mlf@cugb.edu.cn; Deng, Junru

2015-11-15

Tm{sup 3+}/Yb{sup 3+} co-doped BaLa{sub 2}ZnO{sub 5} up-conversion (UC) phosphors were successfully synthesized by high temperature solid-state reaction method. The X-ray diffraction (XRD) results show that synthesized phosphor co-doped with 0.75% Tm/10% Yb has the optimum pure phase of BaLa{sub 2}ZnO{sub 5} among different co-doping concentrations. The structure of BaLa{sub 2}ZnO{sub 5}:0.75% Tm/10% Yb phosphor was refined by the Rietveld method and results show the decreased unit cell parameters and cell volume after doping Tm{sup 3+}/Yb{sup 3+}, indicating that Tm{sup 3+}/Yb{sup 3+} have successfully replaced La{sup 3+}. Under excitation at 980 nm, Tm{sup 3+}/Yb{sup 3+} co-doped BaLa{sub 2}ZnO{sub 5} phosphorsmore » present bright blue emission near 478 nm generated by the {sup 1}G{sub 4}→{sup 3}H{sub 6} transition and weak red emissions around 653 nm and 692 nm generated by the {sup 1}G{sub 4}→{sup 3}F{sub 4} and {sup 3}F{sub 3}→{sup 3}H{sub 6} transitions of Tm{sup 3+}, respectively. The UC luminescence properties of BaLa{sub 2}ZnO{sub 5} phosphors co-doped with different Tm{sup 3+}/Yb{sup 3+} concentrations were investigated, and the related UC mechanisms of Tm{sup 3+}/Yb{sup 3+} co-doped BaLa{sub 2}ZnO{sub 5} depending on pump power were studied in detail. - Graphical abstract: Up-conversion luminescence of BaLa{sub 2}ZnO{sub 5}:Tm{sup 3+}/Yb{sup 3+} and its crystal structure and up-conversion mechanisms. - Highlights: • Up-conversion phosphors BaLa{sub 2}ZnO{sub 5} co-doped with Tm{sup 3+}/Yb{sup 3+} were synthesized by high temperature solid-state reaction method. • The crystal structure of BaLa{sub 2}ZnO{sub 5} and the changes of cell parameters and volume of BaLa{sub 2}ZnO{sub 5} after doping Tm{sup 3+} and Yb{sup 3+} have been discussed. • Up-conversion luminescence properties and energy transfer between Tm{sup 3+} and Yb{sup 3+} in BaLa{sub 2}ZnO{sub 5} have been discussed in detail.« less

Nanostructure CdS/ZnO heterojunction configuration for photocatalytic degradation of Methylene blue

NASA Astrophysics Data System (ADS)

Velanganni, S.; Pravinraj, S.; Immanuel, P.; Thiruneelakandan, R.

2018-04-01

In the present manuscript, thin films of Zinc Oxide (ZnO) have been deposited on a FTO substrate using a simple successive ionic layer adsorption and reaction (SILAR) and chemical bath deposition (CBD) method. Cadmium Sulphide (CdS) nanoparticles are sensitized over ZnO thin films using SILAR method. The synthesized nanostructured CdS/ZnO heterojunction thin films was characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), High resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), UV-Vis spectroscopy and Raman spectroscopy techniques. The band gap of CdS nanoparticles over ZnO nanostructure was found to be about 3.20 eV. The photocatalytic activities of the deposited CdS/ZnO thin films were evaluated by the degradation of methylene blue (MB) in an aqueous solution under sun light irradiation.

Progress in the Development of CdTe and CdZnTe Semiconductor Radiation Detectors for Astrophysical and Medical Applications

PubMed Central

Sordo, Stefano Del; Abbene, Leonardo; Caroli, Ezio; Mancini, Anna Maria; Zappettini, Andrea; Ubertini, Pietro

2009-01-01

Over the last decade, cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) wide band gap semiconductors have attracted increasing interest as X-ray and gamma ray detectors. Among the traditional high performance spectrometers based on silicon (Si) and germanium (Ge), CdTe and CdZnTe detectors show high detection efficiency and good room temperature performance and are well suited for the development of compact and reliable detection systems. In this paper, we review the current status of research in the development of CdTe and CdZnTe detectors by a comprehensive survey on the material properties, the device characteristics, the different techniques for improving the overall detector performance and some major applications. Astrophysical and medical applications are discussed, pointing out the ongoing Italian research activities on the development of these detectors. PMID:22412323

Synthesis of CdSe/ZnS and CdTe/ZnS Quantum Dots: Refined Digestive Ripening

DOE PAGES

Cingarapu, Sreeram; Yang, Zhiqiang; Sorensen, Christopher M.; ...

2012-01-01

We report synthesis of CdSe and CdTe quantum dots (QDs) from the bulk CdSe and CdTe material by evaporation/co-condensation using the solvated metal atom dispersion (SMAD) technique and refined digestive ripening. The outcomes of this new process are (1) the reduction of digestive ripening time by employing ligands (trioctylphosphine oxide (TOPO) and oleylamine (OA)) as capping agent as well as digestive ripening solvent, (2) ability to tune the photoluminescence (PL) from 410 nm to 670 nm, (3) demonstrate the ability of SMAD synthesis technique for other semiconductors (CdTe), (4) direct comparison of CdSe QDs growth with CdTe QDs growth based on digestivemore » ripening times, and (5) enhanced PL quantum yield (QY) of CdSe QDs and CdTe QDs upon covering with a ZnS shell. Further, the merit of this synthesis is the use of bulk CdSe and CdTe as the starting materials, which avoids usage of toxic organometallic compounds, eliminates the hot injection procedure, and size selective precipitation processes. It also allows the possibility of scale up. These QDs were characterized by UV-vis, photoluminescence (PL), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and powder XRD.« less

Formation and characterization of ZnS/CdS nanocomposite materials into porous silicon

NASA Astrophysics Data System (ADS)

Xue, Tao; Lv, Xiao-yi; Jia, Zhen-hong; Hou, Jun-wei; Jian, Ji-kang

2008-11-01

ZnS/CdS were deposited by chemical vapor deposition (CVD) technique on porous silicon substrates formed by electrochemical anodization of n-type (100) silicon wafer. The optical properties of ZnS/CdS porous silicon composite materials are studied. The results showed that new luminescence characteristics such as strong and stable visible-light emissions with different colors were observed from the ZnS/CdS-PS nanocomposite materials at room temperature.

Wide emission-tunable CdTeSe/ZnSe/ZnS core–shell quantum dots and their conjugation with E. coli O-157

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

Zhou, Haifeng; Zhou, Guangjun, E-mail: gjzhou@sdu.edu.cn; Zhou, Juan

2015-05-15

Highlights: • QDs with variety morphology were obtained via an injection controlled process. • 3-D PL spectra of core–shell QDs show different excitation wavelength dependence. • The PL intensity of QDs with ZnSe transition layer increases dramatically. • Core–shell QDs were processed into aqueous phase and conjugated with E. coli O-157. - Abstract: Wide emission-tunable and different morphological alloyed CdTeSe quantum dots (QDs), CdTeSe/ZnS and CdTeSe/ZnSe/ZnS core–shell QDs were successfully synthesized via an injection controlled process. The effect of injection procedure and reaction temperature were systematically discussed and the growth mechanism was proposed. Most efficient PL wavelength was correlated withmore » reaction time and temperature. The 3-D PL spectra of spherical bare CdTeSe and core–shell QDs with different passivation showed different excitation wavelength dependency. The PL intensity of CdTeSe/ZnSe/ZnS core–shell QDs increased greatly in comparison with that of CdTeSe and CdTeSe/ZnSe QDs. ZnSe transition layer played an important role in improving the PL intensity by providing a smoothened interface and gradient band offsets. The core–shell QDs were transferred into aqueous phase and successfully conjugated with Escherichia coli O-157. The proposed phase-transfer and bio-labeling strategy may be applicable to various QDs with different compositions.« less

Zn/Cd ratios and cadmium isotope evidence for the classification of lead-zinc deposits

PubMed Central

Wen, Hanjie; Zhu, Chuanwei; Zhang, Yuxu; Cloquet, Christophe; Fan, Haifeng; Fu, Shaohong

2016-01-01

Lead-zinc deposits are often difficult to classify because clear criteria are lacking. In recent years, new tools, such as Cd and Zn isotopes, have been used to better understand the ore-formation processes and to classify Pb-Zn deposits. Herein, we investigate Cd concentrations, Cd isotope systematics and Zn/Cd ratios in sphalerite from nine Pb-Zn deposits divided into high-temperature systems (e.g., porphyry), low-temperature systems (e.g., Mississippi Valley type [MVT]) and exhalative systems (e.g., sedimentary exhalative [SEDEX]). Our results showed little evidence of fractionation in the high-temperature systems. In the low-temperature systems, Cd concentrations were the highest, but were also highly variable, a result consistent with the higher fractionation of Cd at low temperatures. The δ114/110Cd values in low-temperature systems were enriched in heavier isotopes (mean of 0.32 ± 0.31‰). Exhalative systems had the lowest Cd concentrations, with a mean δ114/110Cd value of 0.12 ± 0.50‰. We thus conclude that different ore-formation systems result in different characteristic Cd concentrations and fraction levels and that low-temperature processes lead to the most significant fractionation of Cd. Therefore, Cd distribution and isotopic studies can support better understanding of the geochemistry of ore-formation processes and the classification of Pb-Zn deposits. PMID:27121538

Solution processable RGO-CdZnS composite for solar light responsive photocatalytic degradation of 4-Nitrophenol

NASA Astrophysics Data System (ADS)

Ibrahim, Sk; Chakraborty, Koushik; Pal, Tanusri; Ghosh, Surajit

2017-05-01

We report the one pot single step synthesis and characterization of solution processable reduced graphene oxide (RGO) - cadmium zinc sulfide (CdZnS) nanocomposite materials. The composite was characterized structurally and morphologically by XRD and TEM studies. The reduction of GO in RGO-CdZnS composite, was confirmed by XPS and Raman spectroscopy. The photocatalytic activity of the RGO-CdZnS composite was investigated towards the degradation of 4-Nitrophenol. A notable increase of photocatalytic efficiency of RGO-CdZnS compare to controlled CdZnS was observed. Here RGO plays a crucial role to efficient photo induced charge separation from the CdZnS, and decreases the electron-hole recombination probability and subsequently enhanced the photocatalytic activity of the RGO-CdZnS composite material under simulated solar light irradiation. This work highlights the potential application of RGO-based materials in the field of photocatalytic degradation of organic water pollutant.

Structural and Optical Studies of ZnCdSe/ZnSe/ZnMgSSe Separate Confinement Heterostructures with Different Buffer Layers

NASA Astrophysics Data System (ADS)

Tu, Ru-Chin; Su, Yan-Kuin; Huang, Ying-Sheng; Chen, Giin-Sang; Chou, Shu-Tsun

1998-09-01

Detailed structural and optical studies of ZnCdSe/ZnSe/ZnMgSSe separate confinementheterostructures (SCH) grown on ZnSe, ZnSe/ZnSSe strained-layer superlattices (SLS),and GaAs buffer layers at the II VI/GaAs interface have been carried out by employingtransmission electron microscopy, variable temperature photoluminescence (PL), andcontactless electroreflectance (CER) measurements. A significant improvement onthe defect reduction and the optical quality has been observed by using either theZnSe/ZnSSe SLS or GaAs as the buffer layers when compared to that of the sample usingonly ZnSe as the buffer layer. However, the sample grown with the SLS buffer layersreveals a room temperature PL intensity higher than that of the sample grown witha GaAs buffer layer, which may still suffer from the great ionic differences betweenthe II V and III V atoms. Using 15 K CER spectra, we have also studied variousexcitonic transitions originating from strained Zn0.80Cd0.20Se/ZnSe single quantumwell in SCH with different buffer layers. An analysis of the CER spectra has ledto the identification of various excitonic transitions, mnH (L), between the mthconduction band state and the nth heavy (light)-hole band state. An excellentagreement between experiments and theoretical calculations based on the envelopefunction approximation model has been achieved.

High spatial resolution correlated investigation of Zn segregation to stacking faults in ZnTe/CdSe nanostructures

NASA Astrophysics Data System (ADS)

Bonef, Bastien; Grenier, Adeline; Gerard, Lionel; Jouneau, Pierre-Henri; André, Regis; Blavette, Didier; Bougerol, Catherine

2018-02-01

The correlative use of atom probe tomography (APT) and energy dispersive x-ray spectroscopy in scanning transmission electron microscopy (STEM) allows us to characterize the structure of ZnTe/CdSe superlattices at the nanometre scale. Both techniques reveal the segregation of zinc along [111] stacking faults in CdSe layers, which is interpreted as a manifestation of the Suzuki effect. Quantitative measurements reveal a zinc enrichment around 9 at. % correlated with a depletion of cadmium in the stacking faults. Raw concentration data were corrected so as to account for the limited spatial resolution of both STEM and APT techniques. A simple calculation reveals that the stacking faults are almost saturated in Zn atoms (˜66 at. % of Zn) at the expense of Cd that is depleted.

Growth of CdZnTe Crystals for Radiation Detector Applications by Directional Solidification

NASA Technical Reports Server (NTRS)

Su, Ching-Hua

2014-01-01

Advances in Cadmium Zinc Telluride (Cd(sub 1-x)Zn(sub x)Te) growth techniques are needed for the production of large-scale arrays of gamma and x-ray astronomy. The research objective is to develop crystal growth recipes and techniques to obtain large, high quality CdZnTe single crystal with reduced defects, such as charge trapping, twinning, and tellurium precipitates, which degrade the performance of CdZnTe and, at the same time, to increase the yield of usable material from the CdZnTe ingot. A low gravity material experiment, "Crystal Growth of Ternary Compound Semiconductors in Low Gravity Environment", will be performed in the Material Science Research Rack (MSRR) on International Space Station (ISS). One section of the flight experiment is the melt growth of CdZnTe ternary compounds. This talk will focus on the ground-based studies on the growth of Cd(sub 0.80)Zn(sub 0.20)Te crystals for radiation detector applications by directional solidification. In this investigation, we have improved the properties that are most critical for the detector applications (electrical properties and crystalline quality): a) Electrical resistivity: use high purity starting materials (with reproducible impurity levels) and controlled Cd over pressure during growth to reproducibly balance the impurity levels and Cd vacancy concentration b) Crystalline quality: use ultra-clean growth ampoule (no wetting after growth), optimized thermal profile and ampoule design, as well as a technique for supercool reduction to growth large single crystal with high crystalline quality

On the possibility of room temperature ferromagnetism on chunk-shape BaSnO3/ZnO core/shell nanostructures

NASA Astrophysics Data System (ADS)

Rajamanickam, N.; Jayakumar, K.; Ramachandran, K.

2018-04-01

Core/shell BaSnO3/ZnO (BS-ZO) nanostructures were prepared by oxalate precipitation method and wet-chemical method. BaSnO3 (BSO) cubic perovskite structure and ZnO hexagonal wurtzite structure were confirmed by X-ray diffraction (XRD). The crystallite sizes is 23 nm, 29 nm and 27 nm for BSO, ZnO and BS-ZO, respectively. Chunk-shape and cuboids morphology observed from scanning electron microscopy (SEM) analysis. The magnetic properties were studied by VSM for bare and core-shell nano systems and the room temperature ferromagnetism observed for core-shell nanostructures. The BSO/ZnO shows enhanced coercivity and saturated magnetization as compared with BSO and ZnO nanostructures.

Photoluminescent enhancement of CdSe/Cd(1-x) Zn(x)S quantum dots by hexadecylamine at room temperature.

PubMed

Yang, Jie; Yang, Ping

2012-09-01

CdSe/Cd(1-x) Zn(x)S core/shell quantum dots (QDs) were fabricated in 1-octadecene via a two step synthesis. CdSe cores were first prepared using CdO, trioctylphosphine (TOP) selenium, and stearic acid. Subsquently, a Cd(1-x) Zn(x)S shell coating was carried out using zinc acetate dihydrate, cadmium acetate dihydrate, TOPS, and hexadecylamine (HDA) starting materials in the friendly organic system under relatively low temperature. The absorption and photoluminescence (PL) spectra have a significant red shift after the coverage of Cd(1-x)Zn(x)S shell on CdSe cores. The X-ray diffraction analysis of samples confirmed the formation of core/shell structure. The PL quantum yields (QYs) of CdSe/Cd(1-x)Zn(x)S QDs were improved gradually with time at room temperature. This is ascribed to the surface passivation of HDA to the QDs during store. This phenomenon was confirmed by the Fourier transform infrared spectrum of samples. Namely, HDA does not capped on the surface of as-prepared QDs, in which a low PL QYs was observed (less than 10%). Being storing for certain time, HDA attached to the surface of the QDs, in which the PL QYs increased (up to 31%) and the full width at half maximum of PL spectra decreased. Moreover, the fluorescence decay curve of the core/shell QDs is closer to a biexponential decay profile and has a longer average PL lifetime. The variation of average PL lifetime also indicated the influence of HDA during store.

Synthesis, spectral and thermal studies of pyridyl adducts of Zn(II) and Cd(II) dithiocarbamates, and their use as single source precursors for ZnS and CdS nanoparticles.

PubMed

Onwudiwe, Damian C; Strydom, Christien A; Oluwafemi, Oluwatobi S; Hosten, Eric; Jordaan, Anine

2014-06-21

The synthesis, spectroscopic characterisation, and thermal studies of pyridyl adducts of Zn(II) and Cd(II) complexes of N-ethyl-N-phenyl dithiocarbamate, represented as [ZnL2py] and [CdL2py2], are reported. Single-crystal X-ray structural analysis of the Zn compound showed that it is five-coordinate with four sulphurs from dithiocarbamate and one nitrogen from pyridine in a distorted square pyramidal geometry. The thermogravimetric studies indicate that the zinc and cadmium compounds undergo fast weight loss, and the temperature at maximum rate of decomposition is at 277 °C and 265 °C respectively, to give the metal (Zn or Cd) sulphide residues. These compounds were used as single molecule precursors to produce nanocrystalline MS (M = Zn, Cd) after thermolysis in hexadecylamine. The morphological and optical properties of the resulting MS nanocrystallites were investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV-Vis absorption and photoluminescence (PL) spectroscopy, and powdered X-ray diffraction (XRD). By varying the growth time, the temporal evolution of the optical properties and morphology of the nanocrystals were investigated.

ZnO/CdS bi-layer nanostructures photoelectrode for dye-sensitized solar cells

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

Dalal, Paresh V., E-mail: paresh10dalal@gmail.com; Deshpande, Milind P., E-mail: vishwadeshpande@yahoo.co.in; Solanki, Bharat G., E-mail: bhrt.solanki17@gmail.com

2016-05-06

Simple chemical deposition method for the synthesis of ZnO/CdS bilayer photoelectrode on fluorine doped tin oxide (FTO) coated glass substrate in aqueous medium at low temperature (< 373K) is described. The different preparative parameters such as deposition time, bath temperature, concentration of precursor solution and, pH of the bath etc. were optimized. Nanograined ZnO was deposited on FTO coated glass substrates by dip-coating method, whereas CdS nanorods were successfully synthesized on pre-deposited ZnO film by Chemical Bath Deposition (CBD) method. The Photovoltaic properties of FTO/ZnO/CdS bilayer photo electrodes were also studied. A maximum short circuit current density of 9.1 mA cm-2more » and conversion efficiency 1.05% are observed for ZnO/CdS-10min. Layer, which supports fast electron injection kinetics due to hetero structured nanorod, while minimum values of 0.53mA cm-2 and 0.01% respectively are observed for only ZnO deposited layer.« less

Crystallisation of Ba1-xSrxZn2Si2O7 from BaO/SrO/ZnO/SiO2 glass with different ZrO2 and TiO2 concentrations

NASA Astrophysics Data System (ADS)

Vladislavova, Liliya; Kracker, Michael; Zscheckel, Tilman; Thieme, Christian; Rüssel, Christian

2018-04-01

The effect of different nucleation agents such as ZrO2 and TiO2 was investigated for a first time with respect to their crystallisation behaviour in the glass system BaO-SrO-ZnO-SiO2. In all studied glasses, a Ba1-xSrxZn2Si2O7 (0.1 ≤ x ≤ 0.9) solid solution crystallized. This phase was first described in 2015 to possess a similar structure as the high temperature phase of BaZn2Si2O7 and a thermal expansion close to zero or even negative. It may find applications e.g. as cook panels, telescope mirrors, and furnace windows. Kinetic parameters of the crystallisation process were determined by supplying different heating rates in a differential scanning calorimeter (DSC). The results were evaluated using the equations of Ozawa and Kissinger with respect to the activation energies. Furthermore, the Ozawa method was used for the determination of Avrami parameters, which provides further information on the nucleation and crystallisation processes. Scanning electron microscopy including electron backscatter diffraction (EBSD) was used to characterise the microstructure, to determine the crystallite size and the crystal orientation. For the characterisation of the occurring crystalline phases, X-ray diffraction was used.

Growth of CdZnTe Crystals the Bridgman Technique with Controlled Overpressures of Cd

NASA Technical Reports Server (NTRS)

Su, Ching-Hu; Lehoczky, S. L.

2008-01-01

Cd(1-x)Zn(x)Te crystals with x = 0.15 and 0.20, were grown in this study by closed-ampoule directional solidification (Bridgman) technique with a controlled Cd overpressure. The growth ampoule was made of quartz with inner diameter from 20 to 40 mm and a tapered length of 2.5 cm at the growth tip. Both unseeded and seeded growths were performed with total material charges up to 400 g. After the loading of starting CdZnTe material, a typical amount of 2 g of Cd was also loaded inside a Cd reservoir basket, which was attached beneath the seal-off cup. The ampoule was sealed off under a vacuum below lxl0(exp -5) Torr. The sealed ampoule was placed inside a 4-zone Bridgman furnace - a Cd reservoir zone with a heat-pipe furnace liner on the top, followed by a hot zone, a booster heating zone and a cold zone at the bottom. The Cd zone was typically 300 to 400 C below the hot zone setting. High resistivity material has been obtained without any intentional dopants but has been reproducibly obtained with In doping. The crystalline and the electrical properties of the crystals will be reported.

Obtaining Large Columnar CdTe Grains and Long Lifetime on CdSe, MgZnO, or CdS Layers

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

Amarasinghe, Mahisha; Colegrove, Eric M; Moseley, John

CdTe solar cells have reached efficiencies comparable to multicrystalline silicon and produce electricity at costs competitive with traditional energy sources. Recent efficiency gains have come partly from shifting from the traditional CdS window layer to new materials such as CdSe and MgZnO, yet substantial headroom still exists to improve performance. Thin film technologies including Cu(In,Ga)Se2, perovskites, Cu2ZnSn(S,Se)4, and CdTe inherently have many grain boundaries that can form recombination centers and impede carrier transport; however, grain boundary engineering has been difficult and not practical. In this work, it is demonstrated that wide columnar grains reaching through the entire CdTe layer canmore » be achieved by aggressive postdeposition CdTe recrystallization. This reduces the grain structure constraints imposed by nucleation on nanocrystalline window layers and enables diverse window layers to be selected for other properties critical for electro-optical applications. Computational simulations indicate that increasing grain size from 1 to 7 um can be equivalent to decreasing grain-boundary recombination velocity by three orders of magnitude. Here, large high-quality grains enable CdTe lifetimes exceeding 50 ns.« less

Calcium uptake in aquatic insects: influences of phylogeny and metals (Cd and Zn).

PubMed

Poteat, Monica D; Buchwalter, David B

2014-04-01

Calcium sequestration in the hypo-osmotic freshwater environment is imperative in maintaining calcium homeostasis in freshwater aquatic organisms. This uptake process is reported to have the unintended consequence of potentially toxic heavy metal (Cd, Zn) uptake in a variety of aquatic species. However, calcium uptake remains poorly understood in aquatic insects, the dominant invertebrate faunal group in most freshwater ecosystems. Here, we examined Ca uptake and interactions with heavy metals (Cd, Zn) at low ambient Ca levels (12.5 μmol l(-1)) in 12 aquatic insect species within Ephemerellidae (mayfly) and Hydropsychidae (caddisfly), two families differentially responsive to trace metal pollution. We found Ca uptake varied 70-fold across the 12 species studied. Body mass and clade (family) were found to significantly influence both Ca uptake and adsorption (P≤0.05). Zn and Cd uptake rate constants (ku) exhibited a strong correlation (r=0.96, P<0.0001), suggesting a shared transport system. Ca uptake failed to significantly correlate with either Zn or Cd ku values. Further, neither Zn nor Cd exhibited inhibitory effects toward Ca uptake. In fact, we saw evidence of modest stimulation of Ca uptake rates in some metal treatments. This work suggests that insects generally differ from other freshwater taxa in that aqueous Ca uptake does not appear to be compromised by Cd or Zn exposure. It is important to understand the trace metal and major ion physiology of aquatic insects because of their ecological importance and widespread use as ecological indicators.

Linear and nonlinear optical discussions of nanostructured Zn-doped CdO thin films

NASA Astrophysics Data System (ADS)

Yahia, I. S.; Salem, G. F.; Iqbal, Javed; Yakuphanoglu, F.

2017-04-01

Here, we report the doping effect of zinc (Zn) on the physical properties of cadmium oxide (CdO) at various concentrations (1, 2, 3 and 4 wt% of Zn). The studied samples were prepared using sol-gel in addition with sol gel spin coating technique. The structural, optical and dispersive properties were compared with the already reported work in the literature. The structural properties were observed by using atomic force microscopy (AFM). The AFM images show that the grain size decreases with increasing the concentration of Zn. The highest value of average cluster size (78. 71 nm) was found at 1% and the lowest (60.23 nm) when the doping concentration of Zn was 4%. Similar trend was observed in the roughness of the doped thin film when the Zn concentration was increased. The optical properties were examined using Shimadzu UV-Vis-NIR spectrophotometer and we found that the optical band gap of the un-doped CdO and the Zn-doped CdO thin films increases from 2.54 to 2.62 eV as the Zn concentration is increased from 1% to 4%. Also, the optical dispersion parameters (Eo, Ed, n2∞, λ0 and So) were calculated and discussed. We observed that the refractive index dispersion of undoped CdO and the Zn-doped CdO thin films follow the single oscillator model. Finally, spectroscopic method has been exploited to analyze the 3rd order non-linear optical susceptibility χ (3) and nonlinear refractive index n (2).

Resistivity dependence on Zn concentration in semi-insulating (Cd,Zn)Te

NASA Astrophysics Data System (ADS)

Fiederle, Michael; Fauler, Alex; Babentsov, Vladimir N.; Franc, Jan; Benz, Klaus Werner

2003-01-01

The resistivity dependence on Zn concentration had been investigated in semi-insulating (Cd,Zn)Te crystals grown by the vertical Bridgman method. A coorelation between the zinc concentration and the resistivity distribution could be found. The obtained resistivity was in the interval of 2 ×109-1010 Ω cm as expected from the model of compensation. The main deep compensating levels detected by Photo Induced Current Transient Spectroscopy (PICTS) were at 0.64 +/- 0.02 eV and close the middle of the band gap at 0.80 +/- 0.02 eV.

Optical Properties of ZnCdS:I Orange and ZnSTe:I White Thin Film Phosphor for High Ra White LED

NASA Astrophysics Data System (ADS)

Fujii, Satoshi; Tasaki, Norio; Shinomura, Naohiko; Kurai, Satoshi; Yamada, Yoichi; Taguchi, Tsunemasa

In order to develop visible thin film phosphors, we have for the first time prepared ZnCdS and ZnSTe doped with Iodine (I) using low-pressure MOCVD method. ZnCdS:I, of which Cd composition was calibrated to match the lattice constant to that of substrate and the band gap to absorption peak, showed a orange broad emission consist of yellow near band edge emission and red SA emission. Isoelectronic Te in ZnS indicates strong blue-green emissions, whilst I donor impurity in ZnS shows strong red SA emissions. A typical ZnSTe:I thin film shows two broad emission bands locating at around 500 and 680 nm, respectively, indicating Ra˜90. It was shown that high Ra thin film phosphor can be realized by single material (ZnSTe:I), and that MOCVD method is capable for controlling the thickness and doping profile to obtain uniform white emission pattern.

ZnO/Ag/CdO nanocomposite for visible light-induced photocatalytic degradation of industrial textile effluents.

PubMed

Saravanan, R; Mansoob Khan, M; Gupta, Vinod Kumar; Mosquera, E; Gracia, F; Narayanan, V; Stephen, A

2015-08-15

A ternary ZnO/Ag/CdO nanocomposite was synthesized using thermal decomposition method. The resulting nanocomposite was characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, UV-Vis spectroscopy, and X-ray photoelectron spectroscopy. The ZnO/Ag/CdO nanocomposite exhibited enhanced photocatalytic activity under visible light irradiation for the degradation of methyl orange and methylene blue compared with binary ZnO/Ag and ZnO/CdO nanocomposites. The ZnO/Ag/CdO nanocomposite was also used for the degradation of the industrial textile effluent (real sample analysis) and degraded more than 90% in 210 min under visible light irradiation. The small size, high surface area and synergistic effect in the ZnO/Ag/CdO nanocomposite is responsible for high photocatalytic activity. These results also showed that the Ag nanoparticles induced visible light activity and facilitated efficient charge separation in the ZnO/Ag/CdO nanocomposite, thereby improving the photocatalytic performance. Copyright © 2015 Elsevier Inc. All rights reserved.

Novel optical properties of CdS:Zn rocksalt system (a theoretical study)

NASA Astrophysics Data System (ADS)

Khan, M. Junaid Iqbal; Nauman Usmani, M.; Kanwal, Zarfishan

2017-11-01

In present computational study, we focus on optical properties of Zn doped CdS for 1  ×  1  ×  2 and 2  ×  2  ×  2 supercell configurations. Cd atoms are substituted with Zn atoms and results for optical properties demonstrate different trends due to interaction of Zn with S atoms. The study has been performed by PBE-GGA approach using Wien2K within framework of DFT. TDOS and PDOS represent that S-3p states are responsible for conduction. For large supercell configuration, a tremendous change in optical properties has been observed due to different bonding. Optical absorption tends to increase in visible range which supports candidacy of Zn doped CdS for enhanced optoelectronic and nanotechnology applications.

Ba(1-x)Sr(x)Zn2Si2O7--A new family of materials with negative and very high thermal expansion.

PubMed

Thieme, Christian; Görls, Helmar; Rüssel, Christian

2015-12-15

The compound BaZn2Si2O7 shows a high coefficient of thermal expansion up to a temperature of 280 °C, then a transition to a high temperature phase is observed. This high temperature phase exhibits negative thermal expansion. If Ba(2+) is successively replaced by Sr(2+), a new phase with a structure, similar to that of the high temperature phase of BaZn2Si2O7, forms. At the composition Ba0.8Sr0.2Zn2Si2O7, this new phase is completely stabilized. The crystal structure was determined with single crystal X-ray diffraction using the composition Ba0.6Sr0.4Zn2Si2O7, which crystallizes in the orthorhombic space group Cmcm. The negative thermal expansion is a result of motions and distortions inside the crystal lattice, especially inside the chains of ZnO4 tetrahedra. Dilatometry and high temperature X-ray powder diffraction were used to verify the negative thermal expansion. Coefficients of thermal expansion partially smaller than -10·10(-6) K(-1) were measured.

Facile preparation and characterization of ZnCdS nanocrystals for interfacial applications in photovoltaic devices.

PubMed

Duan, Chenghao; Luo, Weining; Jiu, Tonggang; Li, Jiangsheng; Wang, Yao; Lu, Fushen

2018-02-15

Recently, ZnCdS nanocrystals (NCs) have attracted intense attention because of their specific optical properties and electrical characteristics. In this paper, a green and facile solution method is reported for the preparation of ZnCdS nanocrystals using dimethylsulfoxide as small molecular ligands. The ZnCdS nanocrystals are used as an interface modification material in the photovoltaic devices. It is found that the modification of ZnCdS on TiO 2 surface not only suppresses the recombination loss of carriers but also reduces the series resistance of TiO 2 /active layer. Consequently, both of the short circuit current (J sc ) and the fill factor (FF) of the solar cells were significantly improved. Power conversion efficiency (PCE) of 7.75% based on TiO 2 /ZnCdS was achieved in contrast to 6.65% of the reference devices based on pure TiO 2 film in organic solar cells. Furthermore, the PCE of perovskite solar cells based on TiO 2 /ZnCdS was observed with 8.3% enhancement compared to that of pure TiO 2 -based ones. Copyright © 2017 Elsevier Inc. All rights reserved.

Noise in CdZnTe detectors

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

Luke, P. N.; Amman, M.; Lee J. S.

2000-10-10

Noise in CdZnTe devices with different electrode configurations was investigated. Measurements on devices with guard-ring electrode structures showed that surface leakage current does not produce any significant noise. The parallel white noise component of the devices appeared to be generated by the bulk current alone, even though the surface current was substantially higher. This implies that reducing the surface leakage current of a CdZnTe detector may not necessarily result in a significant improvement in noise performance. The noise generated by the bulk current is also observed to be below full shot noise. This partial suppression of shot noise may bemore » the result of Coulomb interaction between carriers or carrier trapping. Devices with coplanar strip electrodes were observed to produce a 1/f noise term at the preamplifier output. Higher levels of this 1/f noise were observed with decreasing gap widths between electrodes. The level of this 1/f noise appeared to be independent of bias voltage and leakage current but was substantially reduced after certain surface treatments.« less

Contactless electroreflectance study of strained Zn0.79Cd0.21Se/ZnSe double quantum wells

NASA Astrophysics Data System (ADS)

Tu, R. C.; Su, Y. K.; Lin, D. Y.; Li, C. F.; Huang, Y. S.; Lan, W. H.; Tu, S. L.; Chang, S. J.; Chou, S. C.; Chou, W. C.

1998-01-01

We have studied various excitonic transitions of strained Zn0.79Cd0.21Se/ZnSe double quantum wells, grown by molecular beam epitaxy on (100) GaAs substrates, using contactless electroreflectance (CER) at 15 and 300 K. A number of intersub-band transitions in the CER spectra from the sample have been observed. An analysis of the CER spectra has led to the identification of various excitonic transitions, mnH(L), between the mth conduction band state and the nth heavy (light)-hole band state. The conduction-band offset Qc is used as an adjustable parameter to study the band offset in the strained Zn0.79Cd0.21Se/ZnSe system. The value of Qc is determined to be 0.67±0.03.

Subcellular compartmentalization of Cd and Zn in two bivalves. II. Significance of trophically available metal (TAM)

USGS Publications Warehouse

Wallace, W.G.; Luoma, S.N.

2003-01-01

This paper examines how the subcellular partitioning of Cd and Zn in the bivalves Macoma balthica and Potamocorbula amurensis may affect the trophic transfer of metal to predators. Results show that the partitioning of metals to organelles, 'enzymes' and metallothioneins (MT) comprise a subcellular compartment containing trophically available metal (TAM; i.e. metal trophically available to predators), and that because this partitioning varies with species, animal size and metal, TAM is similarly influenced. Clams from San Francisco Bay, California, were exposed for 14 d to 3.5 ??g 1-1 Cd and 20.5 ??g 1-1 Zn, including 109Cd and 65Zn as radiotracers, and were used in feeding experiments with grass shrimp Palaemon macrodatylus, or used to investigate the subcellular partitioning of metal. Grass shrimp fed Cd-contaminated P. amurensis absorbed ???60% of ingested Cd, which was in accordance with the partitioning of Cd to the bivalve's TAM compartment (i.e. Cd associated with organelles, 'enzymes' and MT); a similar relationship was found in previous studies with grass shrimp fed Cd-contaminated oligochaetes. Thus, TAM may be used as a tool to predict the trophic transfer of at least Cd. Subcellular fractionation revealed that ???34% of both the Cd and Zn accumulated by M. balthica was associated with TAM, while partitioning to TAM in P. amurensis was metal-dependent (???60% for TAM-Cd%, ???73% for TAM-Zn%). The greater TAM-Cd% of P. amurensis than M. balthica is due to preferential binding of Cd to MT and 'enzymes', while enhanced TAM-Zn% of P. amurensis results from a greater binding of Zn to organelles. TAM for most species-metal combinations was size-dependent, decreasing with increased clam size. Based on field data, it is estimated that of the 2 bivalves, P. amurensis poses the greater threat of Cd exposure to predators because of higher tissue concentrations and greater partitioning as TAM; exposure of Zn to predators would be similar between these species.

Sandwiched ZnO@Au@CdS nanorod arrays with enhanced visible-light-driven photocatalytical performance

NASA Astrophysics Data System (ADS)

Ren, Shoutian; Wang, Yingying; Fan, Guanghua; Gao, Renxi; Liu, Wenjun

2017-11-01

The development of high-performance photocatalysts is central to efforts focused on taking advantage of solar energy to overcome environmental and energy crises. Integrating different functional materials artfully into nanostructures can deliver more efficient photocatalytic activity. Here, sandwiched ZnO@Au@CdS nanorod films were synthesized via successive ZnO nanorod electrodeposition, Au sputtering and CdS electrodeposition. The as-synthesized composites were characterized by UV-vis spectrophotometer, x-ray diffractometer, scanning and transmission electron microscopy. Their photocatalytic activity was assessed by degrading Rhodamine B solution under visible light irradiation. ZnO@Au@CdS exhibited better photocatalytic performance than ZnO@CdS throughout the visible light region, and the corresponding enhancement factor of Au nanoparticles was measured as a function of CdS loading amount, and it could reach 190% with CdS deposition for 1 min. The normalized rate constant could reach 0.387 h-1 for ZnO@Au@CdS-1min, which was equivalent to or better than results in reference photocatalysts. The enhancement mechanism of Au nanoparticles was estimated by comparing the monochromatic photocatalytic action spectra with the absorption spectrum of ZnO@Au@CdS, and it was mainly determined by incident photon energy. With selective excitation of Au nanoparticles by incident photons, the excited hot electrons in Au NPs are transferred to the conduction band of ZnO to boost photocatalytic reaction. With selective excitation of CdS, the enhanced interband absorption of CdS and relay station effect of Au nanoparticles should be responsible for the enhanced photocatalytic performance. Our work not only opens the door to the design of efficient supported photocatalysts, but also helps to understand the enhancement mechanism of LSPR effect on the photoelectric conversion of semiconductors.

MBE Growth of HgCdTe on Large-Area Si and CdZnTe Wafers for SWIR, MWIR and LWIR Detection

NASA Astrophysics Data System (ADS)

Reddy, M.; Peterson, J. M.; Lofgreen, D. D.; Franklin, J. A.; Vang, T.; Smith, E. P. G.; Wehner, J. G. A.; Kasai, I.; Bangs, J. W.; Johnson, S. M.

2008-09-01

Molecular beam epitaxy (MBE) growth of HgCdTe on large-size Si (211) and CdZnTe (211)B substrates is critical to meet the demands of extremely uniform and highly functional third-generation infrared (IR) focal-panel arrays (FPAs). We have described here the importance of wafer maps of HgCdTe thickness, composition, and the macrodefects across the wafer not only to qualify material properties against design specifications but also to diagnose and classify the MBE-growth-related issues on large-area wafers. The paper presents HgCdTe growth with exceptionally uniform composition and thickness and record low macrodefect density on large Si wafers up to 6-in in diameter for the detection of short-wave (SW), mid-wave (MW), and long-wave (LW) IR radiation. We have also proposed a cost-effective approach to use the growth of HgCdTe on low-cost Si substrates to isolate the growth- and substrate-related problems that one occasionally comes across with the CdZnTe substrates and tune the growth parameters such as growth rate, cutoff wavelength ( λ cutoff) and doping parameters before proceeding with the growth on costly large-area CdZnTe substrates. In this way, we demonstrated HgCdTe growth on large CdZnTe substrates of size 7 cm × 7 cm with excellent uniformity and low macrodefect density.

Broadband near-infrared downconversion luminescence in Yb3+-doped BaZn2(BO3)2

NASA Astrophysics Data System (ADS)

Yu, Hua; Deng, Degang; Su, Weitao; Li, Chenxia; Xu, Shiqing

2018-06-01

BaZn2(BO3)2 self-activated phosphors were prepared by the conventional high temperature solid-state method. The PL spectra of BaZn2(BO3)2 powders prepared under reductive and air atmosphere consist of a weak ultraviolet emission band (∼410 nm) and a broad emission band which were centered at ∼ 500 and 545 nm, respectively. According to the spectral analysis and EPR results, the green and yellow emissions may arise from the transitions of photo-generated electron close to the conduction band to the deeply trapped hole in single ionized oxygen vacancy (V+ o) centers and single negatively charged interstitial oxygen ion (O- i), respectively. An efficient broadband near-infrared (NIR) quantum cutting was demonstrated in Yb3+ doped BaZn2(BO3)2 phosphor. Upon excitation with an ultraviolet photon at 375 nm, the emissions of two NIR photons at 983 nm from Yb3+ ions were achieved. The dependences of the visible and NIR emissions, the decay lifetime, the energy transfer efficiency, and the quantum efficiency on the Yb3+ doping content were investigated in detail. The results indicated that the maximum energy transfer and the corresponding downconversion quantum efficiency could reach between 68.5% and 168.5%.

19.5%-Efficient CuIn1-xGaxSe2 Photovoltaic Cells Using A Cd-Zn-S Buffer Layer

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

Bhattacharya. R. N.

2008-01-01

CuIn1-xGaxSe2 (CIGS) solar cell junctions prepared by chemical-bath-deposited (CBD) Zn1-xCdxS (CdZnS), ZnS, and CdS buffer layers are discussed. A 19.52%-efficient, CIGS-based, thin-film photovoltaic device has been fabricated using a single-layer CBD CdZnS buffer layer. The mechanism that creates extensive hydroxide and oxide impurities in CBD-ZnS and CBD-CdZnS thin films (compared to CBD-CdS thin film) is presented.

Acute Toxicity of Ternary Cd-Cu-Ni and Cd-Ni-Zn Mixtures to Daphnia magna: Dominant Metal Pairs Change along a Concentration Gradient.

PubMed

Traudt, Elizabeth M; Ranville, James F; Meyer, Joseph S

2017-04-18

Multiple metals are usually present in surface waters, sometimes leading to toxicity that currently is difficult to predict due to potentially non-additive mixture toxicity. Previous toxicity tests with Daphnia magna exposed to binary mixtures of Ni combined with Cd, Cu, or Zn demonstrated that Ni and Zn strongly protect against Cd toxicity, but Cu-Ni toxicity is more than additive, and Ni-Zn toxicity is slightly less than additive. To consider multiple metal-metal interactions, we exposed D. magna neonates to Cd, Cu, Ni, or Zn alone and in ternary Cd-Cu-Ni and Cd-Ni-Zn combinations in standard 48 h lethality tests. In these ternary mixtures, two metals were held constant, while the third metal was varied through a series that ranged from nonlethal to lethal concentrations. In Cd-Cu-Ni mixtures, the toxicity was less than additive, additive, or more than additive, depending on the concentration (or ion activity) of the varied metal and the additivity model (concentration-addition or independent-action) used to predict toxicity. In Cd-Ni-Zn mixtures, the toxicity was less than additive or approximately additive, depending on the concentration (or ion activity) of the varied metal but independent of the additivity model. These results demonstrate that complex interactions of potentially competing toxicity-controlling mechanisms can occur in ternary-metal mixtures but might be predicted by mechanistic bioavailability-based toxicity models.

Controlling superstructural ordering in the clathrate-I Ba 8 M 16 P 30 (M = Cu, Zn) through the formation of metal–metal bonds

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

Dolyniuk, J.; Whitfield, P. S.; Lee, K.

2017-01-01

Order–disorder–order phase transitions in the clathrate-I Ba8Cu16P30 were induced and controlled by aliovalent substitutions of Zn into the framework. Unaltered Ba8Cu16P30 crystallizes in an ordered orthorhombic (Pbcn) clathrate-I superstructure that maintains complete segregation of metal and phosphorus atoms over 23 different crystallographic positions in the clathrate framework. The driving force for the formation of this Pbcn superstructure is the avoidance of Cu–Cu bonds. This superstructure is preserved upon aliovalent substitution of Zn for Cu in Ba8Cu16-xZnxP30 with 0 < x < 1.6 (10% Zn/Mtotal), but vanishes at greater substitution concentrations. Higher Zn concentrations (up to 35% Zn/Mtotal) resulted in themore » additional substitution of Zn for P in Ba8M16+yP30-y (M = Cu, Zn) with 0 ≤ y ≤ 1. This causes the formation of Cu–Zn bonds in the framework, leading to a collapse of the orthorhombic superstructure into the more common cubic subcell of clathrate-I (Pm[3 with combining macron]n). In the resulting cubic phases, each clathrate framework position is jointly occupied by three different elements: Cu, Zn, and P. Detailed structural characterization of the Ba–Cu–Zn–P clathrates-I via single crystal X-ray diffraction, joint synchrotron X-ray and neutron powder diffractions, pair distribution function analysis, electron diffraction and high-resolution electron microscopy, along with elemental analysis, indicates that local ordering is present in the cubic clathrate framework, suggesting the evolution of Cu–Zn bonds. For the compounds with the highest Zn content, a disorder–order transformation is detected due to the formation of another superstructure with trigonal symmetry and Cu–Zn bonds in the clathrate-I framework. It is shown that small changes in the composition, synthesis, and crystal structure have significant impacts on the structural and transport properties of Zn-substituted Ba8Cu16P30.« less

Development of BaO-ZnO-B2O3 glasses as a radiation shielding material

NASA Astrophysics Data System (ADS)

Chanthima, N.; Kaewkhao, J.; Limkitjaroenporn, P.; Tuscharoen, S.; Kothan, S.; Tungjai, M.; Kaewjaeng, S.; Sarachai, S.; Limsuwan, P.

2017-08-01

The effects of the BaO on the optical, physical and radiation shielding properties of the xBaO: 20ZnO: (80-x)B2O3, where x=5, 10, 15, 20 and 25 mol%, were investigated. The glasses were developed by the conventional melt-quenching technique at 1400 °C with high purity chemicals of H3BO3, ZnO, and BaSO4. The optical transparency of the glasses indicated that the glasses samples were high, as observed by visual inspections. The mass attenuation coefficients (μm), the effective atomic numbers (Zeff), and the effective electron densities (Ne) were increased with the increase of BaO concentrations, and the decrease of gamma-ray energy. The developed glass samples were investigated and compared with the shielding concretes and glasses in terms of half value layer (HVL). The overall results demonstrated that the developed glasses had good shielding properties, and highly practical potentials in the environmental friendly radiation shielding materials without an additional of Pb.

New Fluoride-arsenide Diluted Magnetic Semiconductor (Ba,K)F(Zn,Mn)As with Independent Spin and Charge Doping

NASA Astrophysics Data System (ADS)

Chen, Bijuan; Deng, Zheng; Li, Wenmin; Gao, Moran; Liu, Qingqing; Gu, C. Z.; Hu, F. X.; Shen, B. G.; Frandsen, Benjamin; Cheung, Sky; Lian, Liu; Uemura, Yasutomo J.; Ding, Cui; Guo, Shengli; Ning, Fanlong; Munsie, Timothy J. S.; Wilson, Murray Neff; Cai, Yipeng; Luke, Graeme; Guguchia, Zurab; Yonezawa, Shingo; Li, Zhi; Jin, Changqing

2016-11-01

We report the discovery of a new fluoride-arsenide bulk diluted magnetic semiconductor (Ba,K)F(Zn,Mn)As with the tetragonal ZrCuSiAs-type structure which is identical to that of the “1111” iron-based superconductors. The joint hole doping via (Ba,K) substitution & spin doping via (Zn,Mn) substitution results in ferromagnetic order with Curie temperature up to 30 K and demonstrates that the ferromagnetic interactions between the localized spins are mediated by the carriers. Muon spin relaxation measurements confirm the intrinsic nature of the long range magnetic order in the entire volume in the ferromagnetic phase. This is the first time that a diluted magnetic semiconductor with decoupled spin and charge doping is achieved in a fluoride compound. Comparing to the isostructure oxide counterpart of LaOZnSb, the fluoride DMS (Ba,K)F(Zn,Mn)As shows much improved semiconductive behavior that would be benefit for further application developments.

Photoelectrochemical performance of NiO-coated ZnO-CdS core-shell photoanode

NASA Astrophysics Data System (ADS)

Iyengar, Pranit; Das, Chandan; Balasubramaniam, K. R.

2017-03-01

A nano-structured core-shell ZnO-CdS photoanode device with a mesoporous NiO co-catalyst layer was fabricated using solution-processing methods. The growth of the sparse ZnO nano-rod film with a thickness of ca. 930 nm was achieved by optimizing parameters such as the thickness of the ZnO seed layer, choice of Zn precursor salt and the salt concentration. CdS was then coated by a combination of spin coating and spin SILAR (Successive Ionic Layer Adsorption and Reaction) methods to completely fill the interspace of ZnO nano-rods. The uniform CdS surface facilitated the growth of a continuous mesoporous NiO layer. Upon illumination of 100 mW·cm-2 AM 1.5 G radiation the device exhibits stable photocurrents of 2.15 mA·cm-2 at 1.23 V and 0.92 mA·cm-2 at 0.00 V versus RHE, which are significantly higher as compared to the bare ZnO-CdS device. The excellent performance of the device can be ascribed to the higher visible region absorption by CdS, and effective separation of the photogenerated charge carriers due to the suitable band alignment and nanostructuring. Additionally, the mesoporous NiO overlayer offered a larger contact area with the electrolyte and promoted the kinetics enabling higher and stable photocurrent even till the 35th min. of testing.

Ba{sub 3}ZnTa{sub 2-x}Nb{sub x}O{sub 9} and Ba{sub 3}MgTa{sub 2-x}Nb{sub x}O{sub 9} (0{<=}x{<=}1): synthesis, structure and dielectric properties

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

Thirumal, M.; Jawahar, I.N.; Surendiran, K.P.

2002-11-20

Oxides belonging to the families Ba{sub 3}ZnTa{sub 2-x}Nb{sub x}O{sub 9} and Ba{sub 3}MgTa{sub 2-x}Nb{sub x}O{sub 9} were synthesized by the solid state reaction route. Sintering temperatures of 1300 deg. C led to oxides with disordered (cubic) perovskite structure. However, on sintering at 1425 deg. C hexagonally ordered structures were obtained for Ba{sub 3}MgTa{sub 2-x}Nb{sub x}O{sub 9} over the entire range (0{<=}x{<=}1) of composition, while for Ba{sub 3}ZnTa{sub 2-x}Nb{sub x}O{sub 9} the ordered structure exists in a limited range (0{<=}x{<=}0.5). The dielectric constant is close to 30 for the Ba{sub 3}ZnTa{sub 2-x}Nb{sub x}O{sub 9} family of oxides while the Mg analoguesmore » have lower dielectric constant of {approx}18 in the range 50 Hz to 500 kHz. At microwave frequencies (5-7 GHz) dielectric constant increases with increase in niobium concentration (22-26) for Ba{sub 3}ZnTa{sub 2-x}Nb{sub x}O{sub 9}; for Ba{sub 3}MgTa{sub 2-x}Nb{sub x}O{sub 9} it varies between 12 and 14. The 'Zn' compounds have much higher quality factors and lower temperature coefficient of resonant frequency compared to the 'Mg' analogues.« less

The study and characteristics of ZnO/CdS nanocomposite and its application on nanoantibacterial activities

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

Ali, Tinku; Tripathi, P.; Ahammed, Nashiruddin

We have studied the structural and optical properties of ZnO/CdS nanocomposite and its application on nanoantibacterial activities. In this paper, we have used X-ray diffraction, Transmission electron microscope (TEM) and Energy dispersive X-ray spectroscopy (EDX) techniques in order to know about the structural and optical properties of synthesized ZnO/CdS nanocomposite. After TEM and EDX analysis it has been confirmed that the shape of this nanocomposite is hexagonal and it has no impurity. The optical absorption spectra of pure ZnO and ZnO/CdS nanocomposite have been presented by UV-Visible Spectrometer and the estimated band gap from absorption peak has been found tomore » be 3.36 and 3.74 eV respectively. Antibacterial activity of ZnO/CdS nanocomposite was evaluated by using standard zone of inhibition (ZOI) microbiology assay. The synthesized ZnO/CdS showed promising antibacterial activity against Staphylococcus aureus in dose dependent manner.« less

X-ray photoemission studies of Zn doped Cu 1- xTl xBa 2Ca 2Cu 3- yZn yO 10- δ ( y = 0, 2.65) superconductors

NASA Astrophysics Data System (ADS)

Khan, Nawazish A.; Mumtaz, M.; Ahadian, M. M.; Iraji-zad, Azam

2007-03-01

The X-ray photoemission (XPS) measurements of Cu 1- xTl xBa 2Ca 2Cu 3- yZn yO 10- δ ( y = 0, 2.65) superconductors have been performed and compared. These studies revealed that the charge state of thallium in the Cu 0.5Tl 0.5Ba 2O 4- δ charge reservoir layer in Zn doped samples is Tl 1+, while it is a mix of Tl 1+ and Tl 2+ in Zn free samples. The binding energy of Ba atoms in the Zn doped samples is shifted to higher energy, which when considered along with the presence of Tl 1+ suggested that it more efficiently directed the carriers to ZnO 2 and CuO 2 planes. The evidence of improved inter-plane coupling witnessed in X-ray diffraction is also confirmed by XPS measurements of Ca atoms in the Zn doped samples. The shift of the valance band spectrum in these Zn doped samples to higher energies suggested that the electrons at the top edge of the valance band were tied to a higher binding energy (relative to samples without Zn doping), which most likely resulted in a much lower energy state of the system in the superconducting state. The stronger superconducting state arising out of these effects is witnessed in the form of increased Tc( R = 0), Jc and the extent of diamagnetism in the final compound.

CdZnTe Image Detectors for Hard-X-Ray Telescopes

NASA Technical Reports Server (NTRS)

Chen, C. M. Hubert; Cook, Walter R.; Harrison, Fiona A.; Lin, Jiao Y. Y.; Mao, Peter H.; Schindler, Stephen M.

2005-01-01

Arrays of CdZnTe photodetectors and associated electronic circuitry have been built and tested in a continuing effort to develop focal-plane image sensor systems for hard-x-ray telescopes. Each array contains 24 by 44 pixels at a pitch of 498 m. The detector designs are optimized to obtain low power demand with high spectral resolution in the photon- energy range of 5 to 100 keV. More precisely, each detector array is a hybrid of a CdZnTe photodetector array and an application-specific integrated circuit (ASIC) containing an array of amplifiers in the same pixel pattern as that of the detectors. The array is fabricated on a single crystal of CdZnTe having dimensions of 23.6 by 12.9 by 2 mm. The detector-array cathode is a monolithic platinum contact. On the anode plane, the contact metal is patterned into the aforementioned pixel array, surrounded by a guard ring that is 1 mm wide on three sides and is 0.1 mm wide on the fourth side so that two such detector arrays can be placed side-by-side to form a roughly square sensor area with minimal dead area between them. Figure 1 shows two anode patterns. One pattern features larger pixel anode contacts, with a 30-m gap between them. The other pattern features smaller pixel anode contacts plus a contact for a shaping electrode in the form of a grid that separates all the pixels. In operation, the grid is held at a potential intermediate between the cathode and anode potentials to steer electric charges toward the anode in order to reduce the loss of charges in the inter-anode gaps. The CdZnTe photodetector array is mechanically and electrically connected to the ASIC (see Figure 2), either by use of indium bump bonds or by use of conductive epoxy bumps on the CdZnTe array joined to gold bumps on the ASIC. Hence, the output of each pixel detector is fed to its own amplifier chain.

Magnesium effects on CdSe self-assembled quantum dot formation on Zn xCd yMg 1-x-ySe layers

NASA Astrophysics Data System (ADS)

Noemi Perez-Paz, M.; Lu, Hong; Shen, Aidong; Jean Mary, F.; Akins, Daniel; Tamargo, Maria C.

2006-09-01

Optical and morphological studies are used to investigate the effects of chemical composition and, in particular, the magnesium content of the Zn xCd yMg 1-x-ySe barrier layers on the size, density and uniformity of CdSe self-assembled quantum dots (QDs). A reduction of the uncapped QD size, as well as a blue shift of the capped QD photoluminescence peak position by increasing Mg concentration in the Zn xCd yMg 1-x-ySe barrier has been demonstrated by changing the Mg cell temperature during growth. In addition, a more uniform and more densely packed QD layer has been observed with an increase of the MgSe fraction in the Zn xCd yMg 1-x-ySe barrier layer using three-dimensional topographic atomic force microscopy images of the surface of uncapped QDs. Results point to Mg as a chemical factor that induces QD formation, either by increasing the density of atomic steps or/and by changing the energy of the Zn xCd yMg 1-x-ySe surface.

Purification of CdZnTe by electromigration

NASA Astrophysics Data System (ADS)

Kim, K.; Kim, Sangsu; Hong, Jinki; Lee, Jinseo; Hong, Taekwon; Bolotnikov, A. E.; Camarda, G. S.; James, R. B.

2015-04-01

Electro-migration of ionized/electrically active impurities in CdZnTe (CZT) was successfully demonstrated at elevated temperature with an electric field of 20 V/mm. Copper, which exists in positively charged states, electro-migrated at a speed of 15 μm/h in an electric field of 20 V/mm. A notable variation in impurity concentration along the growth direction with the segregation tendency of the impurities was observed in an electro-migrated CZT boule. Notably, both Ga and Fe, which exist in positively charged states, exhibited the opposite distribution to that of their segregation tendency in Cd(Zn)Te. A CZT detector fabricated from the middle portion of the electro-migrated CZT boule showed an improved mobility-lifetime product of 0.91 × 10-2 cm2/V, compared with that of 1.4 × 10-3 cm2/V, observed in an as-grown (non-electro-migrated) CZT detector. The optimum radiation detector material would have minimum concentration of deep traps required for compensation.

Controllable synthesis of ZnxCd1-xS@ZnO core-shell nanorods with enhanced photocatalytic activity.

PubMed

Xie, Shilei; Lu, Xihong; Zhai, Teng; Gan, Jiayong; Li, Wei; Xu, Ming; Yu, Minghao; Zhang, Yuan-Ming; Tong, Yexiang

2012-07-17

We report the synthesis of Zn(x)Cd(1-x)S@ZnO nanorod arrays via a facile two-step process and the implementation of these core-shell nanorods as an environmental friendly and recyclable photocatalyst for methyl orange degradation. The band gap of Zn(x)Cd(1-x)S@ZnO core-shell nanorods can be readily tunable by adjusting the ratio of Zn/Cd during the synthesis. These Zn(x)Cd(1-x)S@ZnO core-shell nanorods exhibit a high photocatalytic activity and good stability in the degradation of the methyl orange. Moreover, these films grown on FTO substrates make the collection and recycle of the photocatalyst easier. These findings may open new opportunities for the design of effective, stable, and easy-recyclable photocatalytic materials.

Ba2ZnWO6:Sm3+ as promising orange-red emitting phosphors: Photoluminescence properties and energy transfer process

NASA Astrophysics Data System (ADS)

Chen, Peng; Hu, Wenyuan; Yang, Dingming; Zhu, Jiayi; Zhang, Jing; Wu, Yadong

2018-02-01

Novel orange-red emitting phosphors, Ba2Zn1-xWO6:xSm3+ (x = 0.03, 0.04, 0.05, 0.06 and 0.07) (BZW:Sm3+), were prepared using a high-temperature solid-state reaction method. Their crystal structure and photoluminescence properties were characterized and the mechanism of energy transfers between Ba2ZnWO6 and Sm3+ elucidated in detail. It was found that the phosphors had a cubic structure with space group Fm 3 bar m . They can be excited by near-ultraviolet light, and the characteristic emissions of Sm3+ ions are observed at 564 nm, 598 nm and 645 nm, corresponding to 4G5/2 → 6H5/2, 4G5/2 → 6H7/2 and 4G5/2 → 6H9/2 transitions, respectively. The 4G5/2 → 6H9/2 transitions shows the greatest intensity, which indicates that Sm3+ ions occupy the noncentrosymmetric sites. The optimal doping concentration of Sm3+ ions in Ba2ZnWO6 is about 5 mol% and the phenomenon of concentration quenching occurs when the content of Sm3+ ions exceeds 5 mol%. All results show that the Ba2ZnWO6:Sm3+ phosphor holds great promise for use in high-quality white light-emitting diodes.

Structural and magnetic properties of Ni-Zn doped BaM nanocomposite via citrate precursor

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

Rana, Kush; Thakur, Preeti; Thakur, Atul, E-mail: atulphysics@gmail.com

2016-05-23

Ni-Zn substituted M-type barium ferrite nanocomposite has been prepared via citrate precursor method. Nanocomposite having composition BaNi{sub 0.5}Zn{sub 0.5}Fe{sub 11}O{sub 19} was sintered at 900°C for 3hrs and characterized by using different characterization techniques. X-ray diffraction (XRD) confirmed the formation of double phase with most prominent peak at (114). Average crystallite size for pure BaM and BNZFO were found to be 36 nm & 45 nm. Field emission scanning electron microscopy (FESEM) confirmed the formation of hexagonal platelets with a layered structure. Magnetic properties of these samples were investigated by using vibrating sample magnetometer (VSM). Magnetic parameters like saturation magnetization (M{sub s}),more » coericivity (H{sub c}) and squareness ratio (SQR) of nanocomposite were found to be 60 emu/g, 3663 Oe and 0.6163 respectively. These values were noticed to be higher as compared to pure BaM. Enhanced magnetic properties of nanocomposite were strongly dependent on exchange coupling. Therefore these properties make this nanocomposite a suitable candidate for magnetic recording and high frequency applications.« less

Extending the spectral range of CdSe/ZnSe quantum wells by strain engineering

NASA Astrophysics Data System (ADS)

Finke, A.; Ruth, M.; Scholz, S.; Ludwig, A.; Wieck, A. D.; Reuter, D.; Pawlis, A.

2015-01-01

We demonstrate efficient room-temperature photoluminescence and spectral tuning of epitaxially grown ZnSe/CdSe quantum well structures almost over the whole visible spectrum (470-600 nm wavelength). The key element to achieve the observed high quantum efficiency and enormous tuning range was the implementation of a special strain engineering technique, which allows us to suppress substantial lattice relaxation of CdSe on ZnSe. Previous studies indicated that a CdSe coverage exceeding 3 ML on ZnSe results in the formation of extensive lattice defects and complete quenching of the photoluminescence at low and room temperature. In contrast, our approach of strain engineering enables the deposition of planar CdSe quantum wells with a thickness ranging from 1 to 6 ML with excellent optical properties. We attribute the observed experimental features to a controllable strain compensation effect that is present in an alternating system of tensile and compressively strained epitaxial layers and supported this model by calculations of the transition energies of the ZnSe/CdSe quantum wells.

Photoluminescence studies on Cd(1-x)Zn(x)S:Mn2+ nanocrystals.

PubMed

Sethi, Ruchi; Kumar, Lokendra; Pandey, A C

2009-09-01

Highly monodispersed, undoped and doped with Mn2+, binary and ternary (CdS, ZnS, Cd(1-x)Zn(x)S) compound semiconductor nanocrystals have been synthesized by co-precipitation method using citric acid as a stabilizer. As prepared sample are characterized by X-ray diffraction, Small angle X-ray scattering, Transmission electron microscope, Optical absorption and Photoluminescence spectroscopy, for their optical and structural properties. X-ray diffraction, Small angle X-ray scattering and Transmission electron microscope results confirm the preparation of monodispersed nanocrystals. Photoluminescence studies show a significant blue shift in the wavelength with an increasing concentration of Zn in alloy nanocrystals.

Purification, growth, and characterization of Zn(x)Cd(1-x)Se crystals

NASA Astrophysics Data System (ADS)

Silberman, E.; Burger, A.; Chen, W.; Henderson, D. O.; Morgan, S. H.; Springer, John M.; Yao, Y.

The purification of starting materials which were used in the growth of Zn(x)Cd(1-x)Se (x = 0.2) single crystals using the traveling solution method (TSM) is reported. Up to 13 cm long single crystals and as grown resistivities of 6 x 10(exp 12) ohm/cm could be achieved. Infrared and Raman spectra of Zn(0.2)Cd(0.8)Se are also presented and discussed.

Purification, growth, and characterization of Zn(x)Cd(1-x)Se crystals

NASA Technical Reports Server (NTRS)

Silberman, E.; Burger, A.; Chen, W.; Henderson, D. O.; Morgan, S. H.; Springer, John M.; Yao, Y.

1989-01-01

The purification of starting materials which were used in the growth of Zn(x)Cd(1-x)Se (x = 0.2) single crystals using the traveling solution method (TSM) is reported. Up to 13 cm long single crystals and as grown resistivities of 6 x 10(exp 12) ohm/cm could be achieved. Infrared and Raman spectra of Zn(0.2)Cd(0.8)Se are also presented and discussed.

Electrochemiluminescence assay of Cu2+ by using one-step electrodeposition synthesized CdS/ZnS quantum dots.

PubMed

Zhao, Guanhui; Li, Xiaojian; Zhao, Yongbei; Li, Yueyuan; Cao, Wei; Wei, Qin

2017-08-21

A sensitive and selective method was proposed to detect Cu 2+ based on the electrochemiluminescence quenching of CdS/ZnS quantum dots (QDs). Herein, CdS/ZnS QDs were one-step electrodeposited directly on a gold electrode from an electrolyte (containing Cd(NO 3 ) 2 , Zn(NO 3 ) 2 , EDTA and Na 2 S 2 O 3 ) by cycling the potential from 0 to -1.8 V. The prepared CdS/ZnS QDs exhibited excellent solubility and strong and stable cathodic ECL activity. Meanwhile, Nafion was used to immobilize CdS/ZnS QDs. The quenching effect of Cu 2+ on the cathodic ECL of CdS/ZnS QDs was found to be selective and concentration dependent. The linear range for Cu 2+ detection was from 2.5 nM to 200 nM with a detection limit of 0.95 nM. Furthermore, the designed method for the detection of Cu 2+ can provide a reference for the detection of other heavy metal ions.

Positron annihilation spectroscopy of vacancy-related defects in CdTe:Cl and CdZnTe:Ge at different stoichiometry deviations

PubMed Central

Šedivý, L.; Čížek, J.; Belas, E.; Grill, R.; Melikhova, O.

2016-01-01

Positron annihilation spectroscopy (PAS) was used to examine the effect of defined Cd-rich and Te-rich annealing on point defects in Cl-doped CdTe and Ge-doped CdZnTe semi-insulating single crystals. The as-grown crystals contain open-volume defects connected with Cd vacancies . It was found that the Cd vacancies agglomerate into clusters coupled with Cl in CdTe:Cl, and in CdZnTe:Ge they are coupled with Ge donors. While annealing in Cd pressure reduces of the density, subsequent annealing in Te pressure restores . The CdTe:Cl contains negatively-charged shallow traps interpreted as Rydberg states of A-centres and representing the major positron trapping sites at low temperature. Positrons confined in the shallow traps exhibit lifetime, which is shorter than the CdTe bulk lifetime. Interpretation of the PAS data was successfully combined with electrical resistivity, Hall effect measurements and chemical analysis, and allowed us to determine the principal point defect densities. PMID:26860684

InP/ZnS as a safer alternative to CdSe/ZnS core/shell quantum dots: in vitro and in vivo toxicity assessment

NASA Astrophysics Data System (ADS)

Brunetti, Virgilio; Chibli, Hicham; Fiammengo, Roberto; Galeone, Antonio; Malvindi, Maria Ada; Vecchio, Giuseppe; Cingolani, Roberto; Nadeau, Jay L.; Pompa, Pier Paolo

2012-12-01

We show that water soluble InP/ZnS core/shell QDs are a safer alternative to CdSe/ZnS QDs for biological applications, by comparing their toxicity in vitro (cell culture) and in vivo (animal model Drosophila). By choosing QDs with comparable physical and chemical properties, we find that cellular uptake and localization are practically identical for these two nanomaterials. Toxicity of CdSe/ZnS QDs appears to be related to the release of poisonous Cd2+ ions and indeed we show that there is leaching of Cd2+ ions from the particle core despite the two-layer ZnS shell. Since an almost identical amount of In(iii) ions is observed to leach from the core of InP/ZnS QDs, their very low toxicity as revealed in this study hints at a much lower intrinsic toxicity of indium compared to cadmium.

InP/ZnS as a safer alternative to CdSe/ZnS core/shell quantum dots: in vitro and in vivo toxicity assessment.

PubMed

Brunetti, Virgilio; Chibli, Hicham; Fiammengo, Roberto; Galeone, Antonio; Malvindi, Maria Ada; Vecchio, Giuseppe; Cingolani, Roberto; Nadeau, Jay L; Pompa, Pier Paolo

2013-01-07

We show that water soluble InP/ZnS core/shell QDs are a safer alternative to CdSe/ZnS QDs for biological applications, by comparing their toxicity in vitro (cell culture) and in vivo (animal model Drosophila). By choosing QDs with comparable physical and chemical properties, we find that cellular uptake and localization are practically identical for these two nanomaterials. Toxicity of CdSe/ZnS QDs appears to be related to the release of poisonous Cd(2+) ions and indeed we show that there is leaching of Cd(2+) ions from the particle core despite the two-layer ZnS shell. Since an almost identical amount of In(III) ions is observed to leach from the core of InP/ZnS QDs, their very low toxicity as revealed in this study hints at a much lower intrinsic toxicity of indium compared to cadmium.

Facile synthesis and luminescence characteristics of high-quality CdS: Eu/ZnS core/shell nanocrystals with biocompatibility.

PubMed

Zhang, Kexin; Zhang, Rui; Yu, Yaxin; Sun, Shuqing

2012-04-01

In this paper, we report a facile method to synthesize high quality CdS: Eu nanocrystals (NCs) and CdS: Eu/ZnS NCs with strong photoluminescence (PL). The influence of various experimental variables including the concentration of Eu3+ ions, the reaction time and the reaction temperature were investigated systematically. In addition, the PL properties of CdS: Eu NCs exhibited pH sensitive. Under the acid condition, pH value of the CdS: Eu NCs solution played an important role in determining PL emission intensity. However, under the alkaline condition, the obtained CdS: Eu NCs exhibited a tunable PL emission wavelength (from 490 nm to 610 nm) when pH value was adjusted from pH 7 to 10. After coating with ZnS shell, the CdS: Eu/ZnS NCs showed enhanced PL intensity compare with one of the CdS: Eu NCs. The CdS: Eu NCs and CdS: Eu/ZnS NCs were characterized by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). In addition, the biocompatibility of these NCs was measured by hemolytic test, which indicated that CdS: Eu/ZnS NCs were more biocompatible than CdS: Eu NCs at the same conditions. It can be expected that CdS: Eu/ZnS NCs are promising biolabeling materials.

Synthesis and growth mechanism of Zn0.5Cd0.5S nanohexagon dendrite

NASA Astrophysics Data System (ADS)

Yu, Wen; Fang, Pengfei; Wang, Shaojie

2014-12-01

Hierarchical Zn0.5Cd0.5S nanohexagon dendrites were synthesized by a one-step hydrothermal method. The Zn0.5Cd0.5S nanohexagon dendrites were made up of nanohexagons with a side length of about 90 nm. The nanohexagons were regularly arranged forming as embranchments which were parallel to each other along certain hexagonal directions. Furthermore, these embranchments made up primary trunks shaping as dendrites. The growth mechanism of Zn0.5Cd0.5S nanohexagon dendrites was proposed in which molecular soft template and lowest energy principle played key roles. By adjusting the composition of the reactants, a series of ZnxCd1-xS solid solutions could be obtained. The morphology of the synthesized ZnxCd1-xS depended much on the x value. The UV-vis spectra absorb edges of the ZnxCd1-xS samples continuously shifted indicating the changes of the band gap.

CdTe/ZnS quantum dots as fluorescent probes for ammonium determination.

PubMed

Yi, Kui-Yu

2016-06-01

Novel CdTe/ZnS quantum dot (QD) probes based on the quenching effect were proposed for the simple, rapid, and specific determination of ammonium in aqueous solutions. The QDs were modified using 3-mercaptopropionic acid, and the fluorescence responses of the CdTe/ZnS QD probes to ammonium were detected through regularity quenching. The quenching levels of the CdTe/ZnS QDs and ammonium concentration showed a good linear relationship between 4.0 × 10(-6) and 5.0 × 10(-4) mol/L; the detection limit was 3.0 × 10(-7) mol/L. Ammonium contents in synthetic explosion soil samples were measured to determine the practical applications of the QD probes and a probable quenching mechanism was described. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Structural and photoluminescence investigations of Sm{sup 3+} doped BaY{sub 2}ZnO{sub 5} nanophosphors

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

Chahar, Sangeeta; Taxak, V.B.; Dalal, Mandeep

2016-05-15

Highlights: • BaY{sub 2(1−x)}Sm{sub 2x}ZnO{sub 5} nanophosphors have been synthesized via solution combustion. • The nanophosphors have been characterized by XRD, TEM and PL spectroscopy. • The crystal structure reveals influence of doping on lattice parameters. • This nanophosphor executes orange–red emission under near UV excitation. - Abstract: BaY{sub 2}ZnO{sub 5}:Sm{sup 3+} nanophosphor was successfully synthesized using solution combustion process. XRD and photoluminescence (PL) techniques were used to analyze the structural and photoluminescence properties. Morphological study of the thermally stable powder was carried out using transmission electron microscope (TEM). Rietveld refinement technique has been used to analyze the samples qualitativelymore » as well as quantitatively. X-Ray diffraction analysis confirms that the highly crystalline single phased Sm{sup 3+} doped BaY{sub 2}ZnO{sub 5} nanophosphor crystallizes in orthorhombic lattice with Pbnm space group. The average particle size lies in the range 80–90 nm with spherical morphology. The photoluminescence excitation at 411 nm yields an intense orange–red emission centered at 610 nm due to {sup 4}G{sub 5/2}–{sup 6}H{sub 7/2} transition. The concentration dependent luminescent behavior of BaY{sub 2(1−x)}Sm{sub 2x}ZnO{sub 5} nanophosphor shows that the optimum concentration for best luminescence is 3 mol%. These results indicate that these nanophosphors find potential applications in the field of phosphor-converted white LED systems.« less

Study of electrostatically self-assembled thin films of CdS and ZnS nanoparticle semiconductors

NASA Astrophysics Data System (ADS)

Suryajaya

In this work, CdS and ZnS semiconducting colloid nanoparticles coated with organic shell, containing either SO[3-] or NH[2+] groups, were deposited as thin films using the technique of electrostatic self-assembly. The films produced were characterized with UV-vis spectroscopy and spectroscopic ellipsometry - for optical properties; atomic force microscopy (AFM) - for morphology study; mercury probe - for electrical characterisation; and photon counter - for electroluminescence study. UV-vis spectra show a substantial blue shift of the main absorption band of both CdS and ZnS, either in the form of solutions or films, with respect to the bulk materials. The calculation of nanoparticles' radii yields the value of about 1.8 nm for both CdS and ZnS.The fitting of standard ellipsometry data gave the thicknesses (d) of nanoparticle layers of around 5 nm for both CdS and ZnS which corresponds well to the size of particles evaluated from UV-vis spectral data if an additional thickness of the organic shell is taken into account. The values of refractive index (n) and extinction coefficient (k) obtained were about 2.28 and 0.7 at 633 nm wavelength, for both CdS and ZnS.Using total internal reflection (TIRE), the process of alternative deposition of poly-allylamine hydrochloride (PAH) and CdS (or ZnS) layers could be monitored in-situ. The dynamic scan shows that the adsorption kinetic of the first layer of PAH or nanoparticles was slower than that of the next layer. The fitting of TIRE spectra gavethicknesses of about 7 nm and 12 nm for CdS and ZnS, respectively. It supports the suggestion of the formation of three-dimensional aggregates of semiconductor nanoparticles intercalated with polyelectrolyte.AFM images show the formation of large aggregates of nanoparticles, about 40-50 nm, for the films deposited from original colloid solutions, while smaller aggregates, about 12-20 nm, were obtained if the colloid solutions were diluted.Current-voltage (I-V) and capacitance

Geometrical Characteristics of Cd-Rich Inclusion Defects in CdZnTe Materials

NASA Astrophysics Data System (ADS)

Xu, Chao; Sheng, Fengfeng; Yang, Jianrong

2017-08-01

The geometrical characteristics of Cd-rich inclusion defects in CdZnTe crystals have been investigated by infrared transmission (IRT) microscopy and chemical etching methods, revealing that they are composed of a Cd-rich inclusion core zone with high dislocation density and defect extension belts. Based on the experimental results, the orientation and shape of these belts were determined, showing that their extension directions in three-dimensional (3-D) space are along <211> crystal orientation. To explain the observed IRT images of Cd-rich inclusion defects, a 3-D model with plate-shaped structure for dislocation extension belts is proposed. Greyscale IRT images of dislocation extension belts thus depend on their absorption layer thickness. Assuming that defects can be discerned by IRT microscopy only when their absorption layer thickness is greater than twice that of the plate-shaped dislocation extension belts, this 3-D defect model can rationalize the IRT images of Cd-rich inclusion defects.

Synthesis and structural, optical and thermal properties of CdS:Zn2+ nanoparticles

NASA Astrophysics Data System (ADS)

Muruganandam, S.; Anbalagan, G.; Murugadoss, G.

2014-12-01

Undoped and Zn (1-5, 10 %) -doped CdS nanoparticles were successfully synthesized by chemical method and polyvinylpyrrolidone was used as capping agent. The morphology and crystalline structure of the samples were studied by transmission electron microscopy and X-ray diffraction. The average particle size of the spherical nanoparticles determined by these techniques was of the order of 2.5-6 nm. The functional groups of the capping agent on CdS:Zn2+ surface were identified by FT-IR study. The band gap of the nanoparticles was calculated using UV-visible absorption spectra and the result showed that the band gap values were dramatically blue shifted from the bulk CdS. The optimum concentration of the doping ions was selected through absorption study. Photoluminescence of the CdS:Zn2+ nanoparticle showed strong blue and green emission. The thermal properties of the nanoparticles were analyzed by thermogravimetric-differential thermal analysis.

Purification of CdZnTe by Electromigration

DOE PAGES

Kim, K.; Kim, Sangsu; Hong, Jinki; ...

2015-04-14

Electro-migration of ionized/electrically active impurities in CdZnTe (CZT) was successfully demonstrated at elevated temperature with an electric field of 20 V/mm. Copper, which exists in positively charged states, electro-migrated at a speed of 15 lm/h in an electric field of 20 V/mm. A notable variation in impurity concentration along the growth direction with the segregation tendency of the impurities was observed in an electro-migrated CZT boule. Notably, both Ga and Fe, which exist in positively charged states, exhibited the opposite distribution to that of their segregation tendency in Cd(Zn)Te. Furthermore, a CZT detector fabricated from the middle portion of themore » electromigrated CZT boule showed an improved mobility-lifetime product of 0.91 10 -2 cm 2 /V, compared to that of 1.4 10 -3 cm 2 /V, observed in an as-grown (non-electro-migrated) CZT detector. The optimum radiation detector material would have minimum concentration of deep traps required for compensation.« less

Multifold polar states in Zn-doped Sr0.9Ba0.1TiO3 ceramics

NASA Astrophysics Data System (ADS)

Guo, Yan-Yan; Guo, Yun-Jun; Wei, Tong; Liu, Jun-Ming

2015-12-01

We investigate the effect of Zn doping on the dielectricity and ferroelectricity of a series of polycrystalline Sr0.9-xZnxBa0.1TiO3 (0.0% ≤ x ≤ 5.0%) ceramics. It is surprisingly observed that the Zn doping will produce the multifold polar states, i.e., the Zn-doped ceramic will convert a reduced polar state into an enhanced polar state, and eventually into a stabilized polar state with increasing the doping level x. It is revealed that in the background of quantum fluctuations, the competition between the Zn-doping-induced lattice contraction and the Ba-doping-induced lattice expansion is responsible for both the reduced polar state and the enhanced polar state coming into being. Also, the addition of the antiferrodistortive effect, which is the antipolar interaction originating from the opposite tilted-TiO6 octahedra rotation, represents the core physics behind the stabilized polar state. Project supported by the National Natural Science Foundation of China (Grant Nos. 11304158, 51431006, 51102277, and 11104118), the Scientific Research Foundation of Nanjing University of Posts and Telecommunications, China (Grant No. NY213020), and the Qing Lan Project of Jiangsu Province, China.

The effects of deep level traps on the electrical properties of semi-insulating CdZnTe

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

Zha, Gangqiang; Yang, Jian; Xu, Lingyan

2014-01-28

Deep level traps have considerable effects on the electrical properties and radiation detection performance of high resistivity CdZnTe. A deep-trap model for high resistivity CdZnTe was proposed in this paper. The high resistivity mechanism and the electrical properties were analyzed based on this model. High resistivity CdZnTe with high trap ionization energy E{sub t} can withstand high bias voltages. The leakage current is dependent on both the deep traps and the shallow impurities. The performance of a CdZnTe radiation detector will deteriorate at low temperatures, and the way in which sub-bandgap light excitation could improve the low temperature performance canmore » be explained using the deep trap model.« less

The composition effect on the thermal and optical properties across CdZnTe crystals

NASA Astrophysics Data System (ADS)

Strzałkowski, K.

2016-11-01

Cd1-x Zn x Te mixed crystals investigated in this work were grown from the melt using the vertical Bridgman-Stockbarger method in the whole range of composition 0  <  x  <  1 that is from one binary crystal (CdTe) to another (ZnTe). The real composition of grown crystals was measured with the SEM/EDS method along the growth axis. The segregation coefficient of Zn in a CdTe matrix has been evaluated as being close to unity. The energy gap as a function of the composition was determined from transmission spectroscopy. Thanks to that, the bowing parameter of this ternary alloy was found to be 0.458. In this work the systematical study of thermal properties of Cd1-x Zn x Te alloys from one binary crystal (CdTe) to another (ZnTe) grown by the vertical Bridgman technique were undertaken for the first time. The thermal diffusivity and effusivity of the investigated crystals were derived from the experimental data and allowed the thermal conductivity to be calculated. Diagrams of the thermal conductivity versus composition were analyzed applying the model for mixed semiconducting crystals given by Sadao Adachi. Thanks to that, the contribution of the thermal resistivity arising from the lattice disorder to the total resistivity of the crystal has been determined.

BA71ΔCD2: a New Recombinant Live Attenuated African Swine Fever Virus with Cross-Protective Capabilities.

PubMed

Monteagudo, Paula L; Lacasta, Anna; López, Elisabeth; Bosch, Laia; Collado, Javier; Pina-Pedrero, Sonia; Correa-Fiz, Florencia; Accensi, Francesc; Navas, María Jesús; Vidal, Enric; Bustos, María J; Rodríguez, Javier M; Gallei, Andreas; Nikolin, Veljko; Salas, María L; Rodríguez, Fernando

2017-11-01

African swine fever is a highly contagious viral disease of mandatory declaration to the World Organization for Animal Health (OIE). The lack of available vaccines makes its control difficult; thus, African swine fever virus (ASFV) represents a major threat to the swine industry. Inactivated vaccines do not confer solid protection against ASFV. Conversely, live attenuated viruses (LAV), either naturally isolated or obtained by genetic manipulation, have demonstrated reliable protection against homologous ASFV strains, although little or no protection has been demonstrated against heterologous viruses. Safety concerns are a major issue for the use of ASFV attenuated vaccine candidates and have hampered their implementation in the field so far. While trying to develop safer and efficient ASFV vaccines, we found that the deletion of the viral CD2v (EP402R) gene highly attenuated the virulent BA71 strain in vivo Inoculation of pigs with the deletion mutant virus BA71ΔCD2 conferred protection not only against lethal challenge with the parental BA71 but also against the heterologous E75 (both genotype I strains). The protection induced was dose dependent, and the cross-protection observed in vivo correlated with the ability of BA71ΔCD2 to induce specific CD8 + T cells capable of recognizing both BA71 and E75 viruses in vitro Interestingly, 100% of the pigs immunized with BA71ΔCD2 also survived lethal challenge with Georgia 2007/1, the genotype II strain of ASFV currently circulating in continental Europe. These results open new avenues to design ASFV cross-protective vaccines, essential to fight ASFV in areas where the virus is endemic and where multiple viruses are circulating. IMPORTANCE African swine fever virus (ASFV) remains enzootic in most countries of Sub-Saharan Africa, today representing a major threat for the development of their swine industry. The uncontrolled presence of ASFV has favored its periodic exportation to other countries, the last event being

BA71ΔCD2: a New Recombinant Live Attenuated African Swine Fever Virus with Cross-Protective Capabilities

PubMed Central

Monteagudo, Paula L.; Lacasta, Anna; López, Elisabeth; Bosch, Laia; Collado, Javier; Pina-Pedrero, Sonia; Correa-Fiz, Florencia; Accensi, Francesc; Navas, María Jesús; Vidal, Enric; Bustos, María J.; Rodríguez, Javier M.; Gallei, Andreas; Nikolin, Veljko; Salas, María L.

2017-01-01

ABSTRACT African swine fever is a highly contagious viral disease of mandatory declaration to the World Organization for Animal Health (OIE). The lack of available vaccines makes its control difficult; thus, African swine fever virus (ASFV) represents a major threat to the swine industry. Inactivated vaccines do not confer solid protection against ASFV. Conversely, live attenuated viruses (LAV), either naturally isolated or obtained by genetic manipulation, have demonstrated reliable protection against homologous ASFV strains, although little or no protection has been demonstrated against heterologous viruses. Safety concerns are a major issue for the use of ASFV attenuated vaccine candidates and have hampered their implementation in the field so far. While trying to develop safer and efficient ASFV vaccines, we found that the deletion of the viral CD2v (EP402R) gene highly attenuated the virulent BA71 strain in vivo. Inoculation of pigs with the deletion mutant virus BA71ΔCD2 conferred protection not only against lethal challenge with the parental BA71 but also against the heterologous E75 (both genotype I strains). The protection induced was dose dependent, and the cross-protection observed in vivo correlated with the ability of BA71ΔCD2 to induce specific CD8+ T cells capable of recognizing both BA71 and E75 viruses in vitro. Interestingly, 100% of the pigs immunized with BA71ΔCD2 also survived lethal challenge with Georgia 2007/1, the genotype II strain of ASFV currently circulating in continental Europe. These results open new avenues to design ASFV cross-protective vaccines, essential to fight ASFV in areas where the virus is endemic and where multiple viruses are circulating. IMPORTANCE African swine fever virus (ASFV) remains enzootic in most countries of Sub-Saharan Africa, today representing a major threat for the development of their swine industry. The uncontrolled presence of ASFV has favored its periodic exportation to other countries, the last

In vivo biodistribution and behavior of CdTe/ZnS quantum dots.

PubMed

Zhao, Yan; Zhang, Yue; Qin, Gaofeng; Cheng, Jinjun; Zeng, Wenhao; Liu, Shuchen; Kong, Hui; Wang, Xueqian; Wang, Qingguo; Qu, Huihua

2017-01-01

The unique features of quantum dots (QDs) make them desirable fluorescent tags for cell and developmental biology applications that require long-term, multitarget, and highly sensitive imaging. In this work, we imaged fluorescent cadmium telluride/zinc sulfide (CdTe/ZnS) QDs in organs, tissues, and cells, and analyzed the mechanism of their lymphatic uptake and cellular distribution. We observed that the fluorescent CdTe/ZnS QDs were internalized by lymph nodes in four cell lines from different tissue sources. We obtained the fluorescence intensity-QD concentrations curve by quantitative analysis. Our results demonstrate that cells containing QDs can complete mitosis normally and that distribution of QDs was uniform across cell types and involved the vesicular transport system, including the endoplasmic reticulum. This capacity for CdTe/ZnS QD targeting provides insights into the applicability and limitations of fluorescent QDs for imaging biological specimens.

ZnO nanosheet arrays constructed on weaved titanium wire for CdS-sensitized solar cells

PubMed Central

2014-01-01

Ordered ZnO nanosheet arrays were grown on weaved titanium wires by a low-temperature hydrothermal method. CdS nanoparticles were deposited onto the ZnO nanosheet arrays using the successive ionic layer adsorption and reaction method to make a photoanode. Nanoparticle-sensitized solar cells were assembled using these CdS/ZnO nanostructured photoanodes, and their photovoltaic performance was studied systematically. The best light-to-electricity conversion efficiency was obtained to be 2.17% under 100 mW/cm2 illumination, and a remarkable short-circuit photocurrent density of approximately 20.1 mA/cm2 was recorded, which could attribute to the relatively direct pathways for transportation of electrons provided by ZnO nanosheet arrays as well as the direct contact between ZnO and weaved titanium wires. These results indicate that CdS/ZnO nanostructures on weaved titanium wires would open a novel possibility for applications of low-cost solar cells. PMID:24618047

Zn–Se–Cd–S Interlayer Formation at the CdS/Cu 2 ZnSnSe 4 Thin-Film Solar Cell Interface

DOE PAGES

Bär, Marcus; Repins, Ingrid; Weinhardt, Lothar; ...

2017-06-14

The chemical structure of the CdS/Cu 2ZnSnSe 4 (CZTSe) interface was studied by a combination of electron and X-ray spectroscopies with varying surface sensitivity. We find the CdS chemical bath deposition causes a 'redistribution' of elements in the proximity of the CdS/CZTSe interface. In detail, our data suggest that Zn and Se from the Zn-terminated CZTSe absorber and Cd and S from the buffer layer form a Zn-Se-Cd-S interlayer. Here, we find direct indications for the presence of Cd-S, Cd-Se, and Cd-Se-Zn bonds at the buffer/absorber interface. Thus, we propose the formation of a mixed Cd(S,Se)-(Cd,Zn)Se interlayer. We also suggestmore » the underlying chemical mechanism is an ion exchange mediated by the amine complexes present in the chemical bath.« less

Do Cd, Cu, Ni, Pb, and Zn biomagnify in aquatic ecosystems?

PubMed

Cardwell, Rick D; Deforest, David K; Brix, Kevin V; Adams, William J

2013-01-01

In this review, we sought to assess from a study of the literature whether five in organic metals (viz., cadmium, copper, lead, nickel, and zinc) bio magnify in aquatic food webs. We also examined whether accumulated metals were toxic to consumers/predators and whether the essential metals (Cu and Zn and possibly Ni) behaved differently from non-essential ones (Cd and Pb). Biomagnification potential was indexed by the magnitude of single and multiple trophic transfers in food chains. In this analysis, we used three lines of evidence-laboratory empirical, biokinetic modeling, and field studies-to make assessments. Trophic transfer factors, calculatedfrom lab studies, field studies, and biokinetic modeling, were generally congruent.Results indicated that Cd, Cu, Pb, and Zn generally do not biomagnify in food chains consisting of primary producers, macro invertebrate consumers, and fish occupying TL 3 and higher. However, bio magnification of Zn (TTFs of 1-2) is possible for circumstances in which dietary Zn concentrations are below those required for metabolism. Cd, Cu, Ni, and Zn may biomagnify in specific marine food chains consisting of bivalves, herbivorous gastropods, and barnacles at TL2 and carnivorous gastropods at TL3. There was an inverse relationship between TTF and exposure concentration for Cd, Cu, Pb, and Zn, a finding that is consistent with previous reviews of bioconcentration factors and bioaccumulation factors for metals. Our analysis also failed to demonstrate a relationship between the magnitude of TTFsand dietary toxicity to consumer organisms. Consequently, we conclude that TTFs for the metals examined are not an inherently useful predictor of potential hazard(i.e., toxic potential) to aquatic organisms. This review identified several uncertainties or data gaps, such as the relatively limited data available for nickel, reliance upon highly structured food chains in laboratory studies compared to the unstructured food webs found in nature, and

Phosphine-free synthesis and characterization of type-II ZnSe/CdS core-shell quantum dots

NASA Astrophysics Data System (ADS)

Ghasemzadeh, Roghayyeh; Armanmehr, Mohammad Hasan; Abedi, Mohammad; Fateh, Davood Sadeghi; Bahreini, Zaker

2018-01-01

A phosphine-free route for synthesis of type-II ZnSe/CdS core-shell quantum dots, using green, low cost and environmentally friendly reagents and phosphine-free solvents such as 1-octadecene (ODE) and liquid paraffin has been reported. Hot-injection technique has been used for the synthesis of ZnSe core quantum dots. The CdS shell quantum dots prepared by reaction of CdO precursor and S powder in 1-octadecene (ODE). The ZnSe/CdS core-shell quantum dots were synthesized via successive ion layer adsorption and reaction (SILAR) technique. The characterization of produced quantum dots were performed by absorption and fluorescence spectroscopy, X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). The results showed the formation of type-II ZnSe/CdS core-shell quantum dots with FWHM 32 nm and uniform size distribution.

Point defects in Cd(Zn)Te and TlBr: Theory

NASA Astrophysics Data System (ADS)

Lordi, Vincenzo

2013-09-01

The effects of various crystal defects on the performances of CdTe, CdZnxTe (CZT), and TlBr for room-temperature high-energy radiation detection are examined using first-principles theoretical methods. The predictive, parameter-free, atomistic approaches used provide fundamental understanding of defect properties that are difficult to measure and also allow rapid screening of possibilities for material engineering, such as optimal doping and annealing conditions. Several recent examples from the author's work are reviewed, including: (i) accurate calculations of the thermodynamic and electronic properties of native point defects and point defect complexes in CdTe and CZT; (ii) the effects of Zn alloying on the native point defect properties in CZT; (iii) point defect diffusion and binding leading to Te clustering in Cd(Zn)Te; (iv) the profound effect of native point defects—principally vacancies—on the intrinsic material properties of TlBr, particularly its electronic and ionic conductivity; and (v) a study on doping TlBr to independently control the electronic and ionic conductivity.

The bipyridine adducts of N-phenyldithiocarbamato complexes of Zn(II) and Cd(II); synthesis, spectral, thermal decomposition studies and use as precursors for ZnS and CdS nanoparticles

NASA Astrophysics Data System (ADS)

Onwudiwe, Damian C.; Strydom, Christien A.

2015-01-01

Bipyridine adducts of N-phenyldithiocarbamato complexes, [ML12L2] (M = Cd(II), Zn(II); L1 = N-phenyldithiocarbamate, L2 = 2,2‧ bipyridine), have been synthesized and characterised. The decomposition of these complexes to metal sulphides has been investigated by thermogravimetric analysis (TGA). The complexes were used as single-source precursors to synthesize MS (M = Zn, Cd) nanoparticles (NPs) passivated by hexadecyl amine (HDA). The growth of the nanoparticles was carried out at two different temperatures: 180 and 220 °C, and the optical and structural properties of the nanoparticles were studied using UV-Vis spectroscopy, photoluminescence spectroscopy (PL), transmission emission microscopy (TEM) and powdered X-ray diffraction (p-XRD). Nanoparticles, whose average diameters are 2.90 and 3.54 nm for ZnS, and 8.96 and 9.76 nm for CdS grown at 180 and 220 °C respectively, were obtained.

Fast Neutron Detection using Pixelated CdZnTe Spectrometers

DOE PAGES

Streicher, Michael; Goodman, David; Zhu, Yuefeng; ...

2017-05-29

One important important signature of special nuclear materials (SNM) are fast neutrons. Fast neutrons have a low natural background rate and readily penetrate high atomic number materials which easily shield gamma-ray signatures. Thus, fast neutrons provide a complementary signal to gamma rays for detecting shielded SNM. Scattering kinematics dictate that a large nucleus (such as Cd or Te) will recoil with small kinetic energy after an elastic collision with a fast neutron. Charge carrier recombination and quenching further reduce the recorded energy deposited. Thus, the energy threshold of CdZnTe detectors must be very low in order to sense the smallmore » signals from these recoils. Here, the threshold was reduced to less than 5 keVee to demonstrate that the 5.9 keV x-ray line from 55Fe could be separated from electronic noise. Elastic scattering neutron interactions were observed as small energy depositions (less than 20 keVee) using digitally-sampled pulse waveforms from pixelated CdZnTe detectors. Characteristic gamma-ray lines from inelastic neutron scattering were also observed.« less

Fast Neutron Detection Using Pixelated CdZnTe Spectrometers

NASA Astrophysics Data System (ADS)

Streicher, Michael; Goodman, David; Zhu, Yuefeng; Brown, Steven; Kiff, Scott; He, Zhong

2017-07-01

Fast neutrons are an important signature of special nuclear materials (SNMs). They have a low natural background rate and readily penetrate high atomic number materials that easily shield gamma-ray signatures. Therefore, they provide a complementary signal to gamma rays for detecting shielded SNM. Scattering kinematics dictate that a large nucleus (such as Cd or Te) will recoil with small kinetic energy after an elastic collision with a fast neutron. Charge carrier recombination and quenching further reduce the recorded energy deposited. Thus, the energy threshold of CdZnTe detectors must be very low in order to sense the small signals from these recoils. In this paper, the threshold was reduced to less than 5 keVee to demonstrate that the 5.9-keV X-ray line from 55Fe could be separated from electronic noise. Elastic scattering neutron interactions were observed as small energy depositions (less than 20 keVee) using digitally sampled pulse waveforms from pixelated CdZnTe detectors. Characteristic gamma-ray lines from inelastic neutron scattering were also observed.

Electrochemiluminescence energy transfer-promoted ultrasensitive immunoassay using near-infrared-emitting CdSeTe/CdS/ZnS quantum dots and gold nanorods

PubMed Central

Li, Lingling; Chen, Ying; Lu, Qian; Ji, Jing; Shen, Yuanyuan; Xu, Mi; Fei, Rong; Yang, Guohai; Zhang, Kui; Zhang, Jian-Rong; Zhu, Jun-Jie

2013-01-01

The marriage of energy transfer with electrochemiluminescence has produced a new technology named electrochemiluminescence energy transfer (ECL-ET), which can realize effective and sensitive detection of biomolecules. To obtain optimal ECL-ET efficiency, perfect energy overlapped donor/acceptor pair is of great importance. Herein, we present a sensitive ECL-ET based immunosensor for the detection of tumor markers, using energy tunable CdSeTe/CdS/ZnS double shell quantum dots (QDs) and gold nanorods (GNRs) as the donor and acceptor, respectively. Firstly a facile microwave-assisted strategy for the synthesis of green- to near-infrared-emitting CdSeTe/CdS/ZnS QDs with time- and component-tunable photoluminescence was proposed. And, on the basis of the adjustable optical properties of both CdSeTe/CdS/ZnS QDs and GNRs, excellent overlap between donor emission and acceptor absorption can be obtained to ensure effective ECL-ET quenching, thus improving the sensing sensitivity. This method represents a novel approach for versatile detection of biomolecules at low concentrations. PMID:23524874

Crystal structure characteristics, dielectric loss, and vibrational spectra of Zn-rich non-stoichiometric Ba[(Zn1/3Nb2/3)1-x Zn x ]O3 ceramics

NASA Astrophysics Data System (ADS)

Li, Jianzhu; Xing, Chao; Qiao, Hengyang; Chen, Huiling; Yang, Jun; Dong, Helei; Shi, Feng

2017-07-01

Zn-Rich non-stoichiometric Ba(Zn1/3Nb2/3)1-x Zn x O3 (BZNZ) (x  =  0.01, 0.02, 0.03, 0.04) ceramics were prepared by the solid-state reaction method at 1500 °C for 2 h. The crystal structures and morphologies were analyzed by x-ray diffraction (XRD) and scanning electron microscopy. The vibration modes were obtained by Raman scattering spectroscopy and Fourier transform far-infrared (FTIR) reflectance spectroscopy. Rietveld refinement was performed for the XRD data. The relationship between crystal structures, dielectric properties, and phonon modes was analyzed in detail. XRD results show that the main phase is Ba(Zn1/3Nb2/3)O3. The Raman results displayed that the ordering structure of BZNZ transformed from 1:2 to 1:1 when x changed from 0.02 to 0.04, and the dielectric losses have a positive correlation with the full width at half maximum values of the A 1g(O) and E g(O) modes. The FTIR spectra were analyzed by the Kramers-Krönig method to obtain the real parts (ɛ‧) and the imaginary parts (ɛ″) of the dielectric constant. When x  =  0.02, the sample possesses uniform grains with clear boundaries and the lowest dielectric loss value (tanδ  =  5.5  ×  10‒4) due to the largest packing fraction.

Exploring Cd-Zn-O-S alloys for improved buffer layers in thin-film photovoltaics

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

Varley, J. B.; Lordi, V.; He, X.

Here, to compete with existing and more mature solar cell technologies such as crystalline Si, thin-film photovoltaics require optimization of every aspect in the device heterostructure to reach maximum efficiencies and cost effectiveness. For absorbers like CdTe, Cu(In,Ga)Se 2 (CIGSe), and Cu 2ZnSn(S,Se) 4 (CZTSSe), improving the n-type buffer layer partner beyond conventional CdS is one avenue that can reduce photocurrent losses and improve overall performance. Here, we use first-principles calculations based on hybrid functionals to explore alloys spanning the Cd-, Zn-, O-, and S-containing phase space to identify compositions that may be superior to common buffers like pure CdSmore » or Zn(O,S). We address issues highly correlated with device performance such as lattice-matching for improved buffer-absorber epitaxy and interface quality, dopability, the band gap for reduced absorption losses in the buffer, and the conduction-band offsets shown to facilitate improved charge separation from photoexcited carriers. We supplement our analysis with device-level simulations as parameterized from our calculations and real devices to assess our conclusions of low-Zn and O content buffers showing improved performance with respect to CdS buffers.« less

Exploring Cd-Zn-O-S alloys for improved buffer layers in thin-film photovoltaics

DOE PAGES

Varley, J. B.; Lordi, V.; He, X.; ...

2017-07-17

Here, to compete with existing and more mature solar cell technologies such as crystalline Si, thin-film photovoltaics require optimization of every aspect in the device heterostructure to reach maximum efficiencies and cost effectiveness. For absorbers like CdTe, Cu(In,Ga)Se 2 (CIGSe), and Cu 2ZnSn(S,Se) 4 (CZTSSe), improving the n-type buffer layer partner beyond conventional CdS is one avenue that can reduce photocurrent losses and improve overall performance. Here, we use first-principles calculations based on hybrid functionals to explore alloys spanning the Cd-, Zn-, O-, and S-containing phase space to identify compositions that may be superior to common buffers like pure CdSmore » or Zn(O,S). We address issues highly correlated with device performance such as lattice-matching for improved buffer-absorber epitaxy and interface quality, dopability, the band gap for reduced absorption losses in the buffer, and the conduction-band offsets shown to facilitate improved charge separation from photoexcited carriers. We supplement our analysis with device-level simulations as parameterized from our calculations and real devices to assess our conclusions of low-Zn and O content buffers showing improved performance with respect to CdS buffers.« less

The bipyridine adducts of N-phenyldithiocarbamato complexes of Zn(II) and Cd(II); synthesis, spectral, thermal decomposition studies and use as precursors for ZnS and CdS nanoparticles.

PubMed

Onwudiwe, Damian C; Strydom, Christien A

2015-01-25

Bipyridine adducts of N-phenyldithiocarbamato complexes, [ML(1)2L(2)] (M=Cd(II), Zn(II); L(1)=N-phenyldithiocarbamate, L(2)=2,2' bipyridine), have been synthesized and characterised. The decomposition of these complexes to metal sulphides has been investigated by thermogravimetric analysis (TGA). The complexes were used as single-source precursors to synthesize MS (M=Zn, Cd) nanoparticles (NPs) passivated by hexadecyl amine (HDA). The growth of the nanoparticles was carried out at two different temperatures: 180 and 220 °C, and the optical and structural properties of the nanoparticles were studied using UV-Vis spectroscopy, photoluminescence spectroscopy (PL), transmission emission microscopy (TEM) and powdered X-ray diffraction (p-XRD). Nanoparticles, whose average diameters are 2.90 and 3.54 nm for ZnS, and 8.96 and 9.76 nm for CdS grown at 180 and 220 °C respectively, were obtained. Copyright © 2014 Elsevier B.V. All rights reserved.

Comparison of temperature sensing of the luminescent upconversion and ZnCdS nanoparticles

NASA Astrophysics Data System (ADS)

Yanina, I. Yu.; Volkova, E. K.; Sagaidachnaya, E. A.; Konyukhova, J. G.; Kochubey, V. I.; Tuchin, V. V.

2018-02-01

The luminescence spectra of upconversion nanoparticles (UCNPs) and ZnCdS nanoparticles (ZnCdSNPs) were measured and analyzed in a wide temperature range: from room to human body and further to a hyperthermic temperature resulting in tissue morphology change. The results show that the luminescence signal of UCNPs and ZnCdSNPs placed within the tissue is reasonably good sensitive to temperature change and accompanied by phase transitions of lipid structures of adipose tissue. The most likely that the multiple phase transitions are associated with the different components of fat cells, such as phospholipids of cell membrane and lipids of fat droplets. In the course of fat cell heating, lipids of fat droplet first transit from a crystalline form to a liquid crystal form and then to a liquid form, which is characterized by much less scattering. The results of phase transitions of lipids were observed as the changes in the slope of the temperature dependence of the intensity of luminescence of the film with nanoparticles embedded into tissue. The obtained results confirm a high sensitivity of the luminescent UCNPs and ZnCdSNPs to the temperature variations within thin tissue samples and show a strong potential for the controllable tissue thermolysis.

Abnormal temperature dependence of conductance of single Cd-doped ZnO nanowires

NASA Astrophysics Data System (ADS)

Li, Q. H.; Wan, Q.; Wang, Y. G.; Wang, T. H.

2005-06-01

Positive temperature coefficient of resistance is observed on single Cd-doped ZnO nanowires. The current along the nanowire increases linearly with the bias and saturates at large biases. The conductance is greatly enhanced either by ultraviolet illumination or infrared illumination. However, the conductance decreases with increasing temperature, in contrast to the reported temperature behavior either for ZnO nanostructures or for CdO nanoneedles. The increase of the conductance under illumination is related to surface effect and the decrease with increasing temperature to bulk effect. These results show that Cd doping does not change surface effect but affects bulk effect. Such a bulk effect could be used to realize on-chip temperature-independent varistors.

Synthesis of CdS/ZnO/graphene composite with high-efficiency photoelectrochemical activities under solar radiation

NASA Astrophysics Data System (ADS)

Han, Weijia; Ren, Long; Qi, Xiang; Liu, Yundan; Wei, Xiaolin; Huang, Zongyu; Zhong, Jianxin

2014-04-01

A novel ternary CdS/ZnO/graphene composite has been successfully prepared by loading ZnO and CdS nanoparticles in graphene nanosheets via a facile one-step hydrothermal method. The microstructures and properties have been examined by X-ray diffraction (XRD), scanning electron microscopy with an energy dispersive spectroscope (EDS), transmission electron microscopy, Raman and UV-vis diffuse reflectance spectra (DRS). The characterization results reveal that the crystalline of the composite is very well, the graphene sheets were tightly coated with ZnO and CdS nanoparticles, and the light-harvesting was effectively strengthened. Taking photoelectrochemical test, the ternary CdS/ZnO/graphene composite exhibits enhanced photocatalytic activity compared with its foundation matrix binary composites and pure ZnO and CdS. The improved photocatalytic performance can be attributed to the enhanced light absorption, the extremely efficient charge separation, as well as superior durability of the ternary composite. It is proposed that graphene-based composites by coupling graphene to suitable, multiple semiconductors can not only greatly improve the capacity for photocatalytic, but also expand the exploration and utilization of graphene-based nanocomposites for energy conversion.

Cd-doped ZnO nano crystalline thin films prepared at 723K by spray pyrolysis

NASA Astrophysics Data System (ADS)

Joishy, Sumanth; Rajendra B., V.

2018-04-01

Ternary Zn1-xCdxO(x=0.10, 0.40, 0.70 at.%) thin films of 0.025M precursor concentration have been successfully deposited on preheated (723K) glass substrates using spray pyrolysis route. The structure, morphology and optical properties of deposited films have been characterized by X-ray diffraction, Scanning Electron Microscopy (SEM) and UV-Visible spectrophotometry. X-ray diffraction study shows that the prepared films are polycrystalline in nature. 10% Cd doped ZnO film belongs to the hexagonal wurtzite system and 70% Cd doped ZnO film belongs to the cubic system, although mixed phases were formed for 40% Cd doped ZnO film. The optical transmittance spectra has shown red shift with increasing cadmium content. Optical energy band gap has been reduced with cadmium dopant.

Synthesis of Two Coumarin-Derived Schiff Bases and Investigation of theirs Selectivity for Zn2.

PubMed

Fan, Long

2017-07-01

In this study, the coumarin-derived schiff bases (HL 1 and HL 2 ) have been designed and synthesized. Upon the addition of Zn 2+ , both of them show significant fluorescence enhancement owing to inhibits PET and ESIPT process respectively. However, the receptor HL 2 response toward Cd 2+ , Mg 2+ , Ba 2+ , Ca 2+ besides Zn 2+ and exhibits fluorescence enhancement but not enough to detection of the concentration levels of Zn 2+ .

Low Temperature Photoluminescence Characterization of Orbitally Grown CdZnTe

NASA Technical Reports Server (NTRS)

Ritter, Timothy M.; Larson, D. J.

1998-01-01

The II-VI ternary alloy CdZnTe is a technologically important material because of its use as a lattice matched substrate for HgCdTe based devices. The increasingly stringent requirements on performance that must be met by such large area infrared detectors also necessitates a higher quality substrate. Such substrate material is typically grown using the Bridgman technique. Due to the nature of bulk semiconductor growth, gravitationally dependent phenomena can adversely affect crystalline quality. The most direct way to alleviate this problem is by crystal growth in a reduced gravity environment. Since it requires hours, even days, to grow a high quality crystal, an orbiting space shuttle or space station provides a superb platform on which to conduct such research. For well over ten years NASA has been studying the effects of microgravity semiconductor crystal growth. This paper reports the results of photoluminescence characterization performed on an arbitrary grown CdZnTe bulk crystal.

Electronic structure of CdSe-ZnS 2D nanoplatelets

NASA Astrophysics Data System (ADS)

Cruguel, Hervé; Livache, Clément; Martinez, Bertille; Pedetti, Silvia; Pierucci, Debora; Izquierdo, Eva; Dufour, Marion; Ithurria, Sandrine; Aubin, Hervé; Ouerghi, Abdelkarim; Lacaze, Emmanuelle; Silly, Mathieu G.; Dubertret, Benoit; Lhuillier, Emmanuel

2017-04-01

Among colloidal nanocrystals, 2D nanoplatelets (NPLs) made of cadmium chalcogenides have led to especially well controlled optical features. However, the growth of core shell heterostructures has so far been mostly focused on CdS shells, while more confined materials will be more promising to decouple the emitting quantum states of the core from their external environment. Using k.p simulation, we demonstrate that a ZnS shell reduces by a factor 10 the leakage of the wavefunction into the surrounding medium. Using X-ray photoemission (XPS), we confirm that the CdSe active layer is indeed unoxidized. Finally, we build an effective electronic spectrum for these CdSe/ZnS NPLs on an absolute energy scale which is a critical set of parameters for the future integration of this material into optoelectronic devices. We determine the work function (WF) to be 4.47 eV while the material is behaving as an n-type semiconductor.

Behaviors of heavy metals (Cd, Cu, Ni, Pb and Zn) in soil amended with composts.

PubMed

Gusiatin, Zygmunt Mariusz; Kulikowska, Dorota

2016-09-01

This study investigated how amendment with sewage sludge compost of different maturation times (3, 6, 12 months) affected metal (Cd, Cu, Ni, Pb, Zn) bioavailability, fractionation and redistribution in highly contaminated sandy clay soil. Metal transformations during long-term soil stabilization (35 months) were determined. In the contaminated soil, Cd, Ni and Zn were predominately in the exchangeable and reducible fractions, Pb in the reducible fraction and Cu in the reducible, exchangeable and oxidizable fractions. All composts decreased the bioavailability of Cd, Ni and Zn for up to 24 months, which indicates that cyclic amendment with compost is necessary. The bioavailability of Pb and Cu was not affected by compost amendment. Based on the reduced partition index (IR), metal stability in amended soil after 35 months of stabilization was in the following order: Cu > Ni = Pb > Zn > Cd. All composts were more effective in decreasing Cd, Ni and Zn bioavailability than in redistributing the metals, and increasing Cu redistribution more than that of Pb. Thus, sewage sludge compost of as little as 3 months maturation can be used for cyclic amendment of multi-metal-contaminated soil.

Structural, Electrical and Optical Properties of Cd Doped ZnO Thin Films by Reactive dc Magnetron Sputtering

NASA Astrophysics Data System (ADS)

Kumar, A. Guru Sampath; Obulapathi, L.; Sarmash, T. Sofi; Rani, D. Jhansi; Maddaiah, M.; Rao, T. Subba; Asokan, K.

2015-04-01

Thin films of cadmium (Cd) (0 wt.%, 2 wt.%, 4 wt.% and 10 wt.%) doped zinc oxide (ZnO) have been deposited on a glass substrate by reactive DC magnetron sputtering. The synthesized films are characterized by glancing angle x-ray diffraction (GAXRD), UV-Vis-NIR spectroscopy, four probe resistivity measurement, Hall measurement system, field emission-scanning electron microscopy and energy dispersive analysis by x-rays. A systematic study has been made on the structure, electrical and optical properties of Cd doped ZnO thin films as a function of Cd concentration (0 wt.%, 2 wt.%, 4 wt.% and 10 wt.%). All these films have a hexagonal wurtzite ZnO structure with (0 0 2) orientation without any Cd related phase from the GAXRD patterns. The grain size was increased and maximum appears at 4 wt.% Cd concentration. The electrical resistivity of the films decreased with the Cd doping and minimum resistivity was observed at 4 wt.% Cd concentration. UV-Vis-NIR studies showed that the optical band gap of ZnO (3.37 eV) was reduced to 3.10 eV which is at 4 wt.% Cd concentration.

Atomistic tight-binding theory of excitonic splitting energies in CdX(X = Se, S and Te)/ZnS core/shell nanocrystals

NASA Astrophysics Data System (ADS)

Sukkabot, Worasak; Pinsook, Udomsilp

2017-01-01

Using the atomistic tight-binding theory (TB) and a configuration interaction description (CI), we numerically compute the excitonic splitting of CdX(X = Se, S and Te)/ZnS core/shell nanocrystals with the objective to explain how types of the core materials and growth shell thickness can provide the detailed manipulation of the dark-dark (DD), dark-bright (DB) and bright-bright (BB) excitonic splitting, beneficial for the active application of quantum information. To analyze the splitting of the excitonic states, the optical band gaps, ground-state wave function overlaps and atomistic electron-hole interactions tend to be numerically demonstrated. Based on the atomistic computations, the single-particle and excitonic gaps are mainly reduced with the increasing ZnS shell thickness owing to the quantum confinement. In the range of the higher to lower energies, the order of the single-particle gaps is CdSe/ZnS, CdS/ZnS and CdTe/ZnS core/shell nanocrystals, while one of the excitonic gaps is CdS/ZnS, CdSe/ZnS and CdTe/ZnS core/shell nanocrystals because of the atomistic electron-hole interaction. The strongest electron-hole interactions are mainly observed in CdSe/ZnS core/shell nanocrystals. In addition, the computational results underline that the energies of the dark-dark (DD), dark-bright (DB) and bright-bright (BB) excitonic splitting are generally reduced with the increasing ZnS growth shell thickness as described by the trend of the electron-hole exchange interaction. The high-to-low splitting of the excitonic states is demonstrated in CdSe/ZnS, CdTe/ZnS and CdS/ZnS core/shell nanocrystals because of the fashion in the electron-hole exchange interaction and overlaps of the electron-hole wave functions. As the resulting calculations, it is expected that CdS/ZnS core/shell nanocrystals are the best candidates to be the source of entangled photons. Finally, the comprehensive information on the excitonic splitting can enable the use of suitable core

Concomitant Zn-Cd and Pb retention in a carbonated fluvio-glacial deposit under both static and dynamic conditions.

PubMed

Lassabatere, Laurent; Spadini, Lorenzo; Delolme, Cécile; Février, Laureline; Galvez Cloutier, Rosa; Winiarski, Thierry

2007-11-01

The chemical and physical processes involved in the retention of 10(-2)M Zn, Pb and Cd in a calcareous medium were studied under saturated dynamic (column) and static (batch) conditions. Retention in columns decreased in order: Pb>Cd approximately Zn. In the batch experiments, the same order was observed for a contact time of less than 40h and over, Pb>Cd>Zn. Stronger Pb retention is in accordance with the lower solubility of Pb carbonates. However, the equality of retained Zn and Cd does not fit the solubility constants of carbonated solids. SEM analysis revealed that heavy metals and calcareous particles are associated. Pb precipitated as individualized Zn-Cd-Ca- free carbonated crystallites. All the heavy metals were also found to be associated with calcareous particles, without any change in their porosity, pointing to a surface/lattice diffusion-controlled substitution process. Zn and Cd were always found in concomitancy, though Pb fixed separately at the particle circumferences. The Phreeqc 2.12 interactive code was used to model experimental data on the following basis: flow fractionation in the columns, precipitation of Pb as cerrusite linked to kinetically controlled calcite dissolution, and heavy metal sorption onto proton exchanging sites (presumably surface complexation onto a calcite surface). This model simulates exchanges of metals with surface protons, pH buffering and the prevention of early Zn and Cd precipitation. Both modeling and SEM analysis show a probable significant decrease of calcite dissolution along with its contamination with metals.

Solar cells based on electrodeposited thin films of ZnS, CdS, CdSSe and CdTe

NASA Astrophysics Data System (ADS)

Weerasinghe, Ajith R.

The motivations of this research were to produce increased efficiency and low-cost solar cells. The production efficiency of Si solar cells has almost reached their theoretical limit, and reducing the manufacturing cost of Si solar cells is difficult to achieve due to the high-energy usage in material purifying and processing stages. Due to the low usage of materials and input energy, thin film solar cells have the potential to reduce the costs. CdS/CdTe thin film solar cells are already the cheapest on $/W basis. The cost of CdTe solar cells can be further reduced if all the semiconducting layers are fabricated using the electrodeposition (ED) method. ED method is scalable, low in the usage of energy and raw materials. These benefits lead to the cost effective production of semiconductors. The conventional method of fabricating CdS layers produces Cd containing waste solutions routinely, which adds to the cost of solar cells.ZnS, CdS and CdS(i-X)Sex buffer and window layers and CdTe absorber layers have been successfully electrodeposited and explored under this research investigation. These layers were fully characterised using complementary techniques to evaluate the material properties. Photoelectrochemical (PEC) studies, optical absorption, X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, atomic force microscopy (AFM) and Raman spectroscopy were utilised to evaluate the material properties of these solid thin film layers. ZnS and CdS thin film layers were electrodeposited from Na-free chemical precursors to avoid the group I element (Na) to reduce deterioration of CdTe devices. Deposition parameters such as, growth substrates, temperature, pH, growth cathodic voltage, stirring rate, time and chemical concentrations were identified to fabricate the above semiconductors. To further optimise these layers, a heat treatment process specific to the material was developed. In addition

On the growth and photocatalytic activity of the vertically aligned ZnO nanorods grafted by CdS shells

NASA Astrophysics Data System (ADS)

Zirak, M.; Moradlou, O.; Bayati, M. R.; Nien, Y. T.; Moshfegh, A. Z.

2013-05-01

We have studied systematically photocatalytic properties of the vertically aligned ZnO@CdS core-shell nanorods where the features were grown through a multistep procedure including sol-gel for the formation of ZnO seed layer, hydrothermal process to grow ZnO nanorods, and successive ion layer adsorption and reaction (SILAR) process to deposit CdS nanoshells onto the ZnO nanorods. Formation of the ZnO seed layer and vertically aligned ZnO nanorods (d ∼ 40 nm) with a hexagonal cross-section was confirmed by AFM and SEM imaging. Successful capping of ZnO nanorods with homogeneous CdS nanocrystallites (∼5 nm) was ascertained by HRTEM diffraction and imaging. Optical properties of the samples were also studied using UV-vis spectrophotometry. It was found that the absorption edge of the CdS shell has a red shift when its thickness increases. Photocatalytic activity of the samples was examined by photodecomposition of methylene blue under UV and visible lights where the maximum reaction rate constant was found to be 0.012 min-1 under UV illumination and 0.007 min-1 under visible light. The difference in catalytic activities of the ZnO@CdS core-shell nanorods under UV and visible irradiations was explained based upon the electronic structure as well as the arrangement of the energy levels in the ZnO@CdS core-shells. It is shown that the structure and photocatalytic efficiency of the samples can be tuned by manipulating the SILAR variables.

Multi-terminal Two-color ZnCdSe/ZnCdMgSe Based Quantum-well Infrared Photodetector

NASA Astrophysics Data System (ADS)

Kaya, Yasin; Ravikumar, Arvind; Chen, Guopeng; Tamargo, Maria C.; Shen, Aidong; Gmachl, Claire

Target recognition and identification applications benefits from two-color infrared (IR) detectors in the mid and long-wavelength IR regions. Currently, InGaAs/AlGaAs and GaAs/AlGaAs multiple quantum wells (QWs) grown on GaAs substrate are the most commonly used two-color QW IR photodetectors (QWIPs). However, the lattice-mismatch and the buildup of strain limit the number of QWs that can be grown, in turn increasing the dark current noise, and limiting the device detectivity.In this work, we report on two-color QWIPs based on the large conduction band offset (~1.12ev) ZnCdSe/ZnCdMgSe material system lattice matched to InP. QWIPs were designed based on a bound to quasi-bound transition, centered at 4 μm and 7 μm and each QW is repeated 50 times to eliminate the high dark current and a contact layer is inserted between the two stacks of QWs for independent electrical contacts. Wafers are processed into two step rectangular mesas by lithography and wet etching. Experiments showed absorption spectra centered at 4.9 μm and 7.6 μm at 80 K and the full width at half maximums were Δλ / λ = 21 % and Δλ / λ = 23 % , respectively. Current work studies the Johnson and the background noise limited detectivities of these QWIPs. Current address: School of Earth, Energy and Environmental Sciences, Stanford, CA 94305, USA.

Interaction of Cd and Zn toxicity for Folsomia candida Willem (Collembola: Isotomidae) in relation to bioavailability in soil

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

Van Gestel, C.A.M.; Hensbergen, P.J.

1997-06-01

The use of toxicity tests in which each chemical is tested separately is inadequate for assessing the potential risk of complex mixtures of chemicals for soil ecosystems. In the present study, the effects of Cd and Zn, alone or in combination, on the survival, growth, and reproduction of the collembolan Folsomia candida were determined after 2, 4, and 6 weeks of exposure in an artificial soil. The water solubility of Cd in the soil was significantly increased by the presence of Zn, whereas Cd did not affect the water solubility of Zn. In spite of this, uptake of Cd ormore » Zn in the animals was not affected by the presence of the other metal, suggesting that water solubility does not determine the uptake of these metals in F. candida. For both Cd and Zn, reproduction was the most sensitive parameter, with 50% effective concentration (EC50) values of 51 and 683 {micro}g/g dry soil, respectively, after 6 weeks. These values corresponded with internal concentrations of 44 {micro}g Cd/g and 14 {micro}g Zn/g dry soil, respectively. Although a proper comparison of the effects of mixtures of the metals with the effects of the individual metals was sometimes hampered by the nonsimilarity of dose-response relationships, it may be concluded that the effects of the mixture of Cd and Zn on the growth of F. candida are antagonistic (EC50 significantly greater than 1.0 toxic unit), while the effects on reproduction are additive (EC50 = 1.0 toxic unit). Similar conclusions could be drawn for EC50s expressed on the basis of total and water-soluble soil concentrations as well as on the basis of internal concentrations in animals. Analysis of the combined effects of Cd and Zn at the 10% effective concentration level did not change these conclusions.« less

Luminescence of CdSe/ZnS quantum dots infiltrated into an opal matrix

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

Gruzintsev, A. N.; Emelchenko, G. A.; Masalov, V. M.

The effect of the photonic band gap in the photonic crystal, the synthesized SiO{sub 2} opal with embedded CdSe/ZnS quantum dots, on its luminescence in the visible spectral region is studied. It is shown that the position of the photonic band gap in the luminescence and reflectance spectra for the infiltrated opal depends on the diameter of the constituent nanospheres and on the angle of recording the signal. The optimal conditions for embedding the CdSe/ZnS quantum dots from the solution into the opal matrix are determined. It is found that, for the opal-CdSe/ZnS nanocomposites, the emission intensity decreases and themore » luminescence decay time increases in the spatial directions, in which the spectral positions of the photonic band gap and the luminescence peak of the quantum dots coincide.« less

Structural, optical, and photoluminescence characterization of electron beam evaporated ZnS/CdSe nanoparticles thin films

NASA Astrophysics Data System (ADS)

Mohamed, S. H.; Ali, H. M.

2011-01-01

Structural, optical, and photoluminescence investigations of ZnS capped with CdSe films prepared by electron beam evaporation are presented. X-ray diffraction analysis revealed that the ZnS/CdSe nanoparticles films contain cubic cadmium selenide and hexagonal zinc sulfide crystals and the ZnS grain sizes increased with increasing ZnS thickness. The refractive index was evaluated in terms of envelope method, which has been suggested by Swanepoel in the transparent region. The refractive index values were found to increase with increasing ZnS thickness. However, the optical band gap and the extinction coefficient were decreased with increasing ZnS thickness. Photoluminescence (PL) investigations revealed the presence of two broad emission bands. The ZnS thickness significantly influenced the PL intensities.

Infrared LED Enhanced Spectroscopic CdZnTe Detector Working under High Fluxes of X-rays

PubMed Central

Pekárek, Jakub; Dědič, Václav; Franc, Jan; Belas, Eduard; Rejhon, Martin; Moravec, Pavel; Touš, Jan; Voltr, Josef

2016-01-01

This paper describes an application of infrared light-induced de-polarization applied on a polarized CdZnTe detector working under high radiation fluxes. We newly demonstrate the influence of a high flux of X-rays and simultaneous 1200-nm LED illumination on the spectroscopic properties of a CdZnTe detector. CdZnTe detectors operating under high radiation fluxes usually suffer from the polarization effect, which occurs due to a screening of the internal electric field by a positive space charge caused by photogenerated holes trapped at a deep level. Polarization results in the degradation of detector charge collection efficiency. We studied the spectroscopic behavior of CdZnTe under various X-ray fluxes ranging between 5×105 and 8×106 photons per mm2 per second. It was observed that polarization occurs at an X-ray flux higher than 3×106 mm−2·s−1. Using simultaneous illumination of the detector by a de-polarizing LED at 1200 nm, it was possible to recover X-ray spectra originally deformed by the polarization effect. PMID:27690024

Strong mechanical adhesion of gold electroless contacts on CdZnTe deposited by alcoholic solutions

NASA Astrophysics Data System (ADS)

Benassi, G.; Nasi, L.; Bettelli, M.; Zambelli, N.; Calestani, D.; Zappettini, A.

2017-02-01

CdZnTe crystals are nowadays employed as X-ray detectors for a number of applications, such as medical imaging, security, and environmental monitoring. One of the main difficulties connected with CdZnTe-based detector processing is the poor contact adhesion that affect bonding procedures and device long term stability. We have shown that it is possible to obtain mechanically stable contacts by common electroless deposition using alcoholic solutions instead of water solutions. The contacts show blocking current-voltage characteristic that is required for obtaining spectroscopic detectors. Nanoscale-resolved chemical analysis indicated that the improved mechanical adhesion is due to a better control of the stoichiometry of the CdZnTe layer below the contact.

Syntheses, crystal structures and photoluminescence properties of five Cd/Zn-organic frameworks

NASA Astrophysics Data System (ADS)

Li, Qing; Xue, Dong-Xu; Zhang, Yu-Feng; Zhang, Zong-Hui; Gao, Ziwei

2018-07-01

Luminescent metal-organic frameworks (MOFs) have displayed extensively potential applications for photocatalysis, photoluminescence, electroluminescence, chemical sensors et al. Herein, five new Cd/Zn-organic frameworks of [Cd(HL)C2H5OH] (1), [Cd(HL)(2,2‧-Bpy)H2O] (2), [Cd2(HL)2(Phen)2] (3), [Zn(HL)BIMB] (4), [Cd3(HL)3(4,4‧-Bpy)DMF]·(H2O) (5) have been deliberately constructed via solvothermal reactions of d10 transition metal salts, i.e. Cd(NO3)2•4H2O or Zn(NO3)2·6H2O, and a V-shaped semi-rigid organic linker of 4,4'-(hydroxymethanediyl) dibenzoic acid (H3L) along with the auxiliary poly-nitrogen ligands of 2,2‧-Bpy(2,2‧-bipyridine), Phen(phenanthroline), BIMB(1,1‧-benzene-1,4-diyldimethanediyl-bis-1H-imidazole) and 4,4‧-Bpy(4,4‧-bipyridine). The crystal structures of compounds 1-5 were precisely determined by single-crystal X-ray diffraction (SC-XRD), Powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR) and Thermogravimetic analysis (TGA). As revealed by SC-XRD, the isolated 1 presents a 2-periodic framework encompassing side-by-side channel-typed helical tubes. Compounds 2-4 display Z-shaped 1-periodic single chains, concomitant with twin chains and tubular structure, respectively. Interestingly, compound 5 demonstrates a two-fold interpenetrated 3-periodic skeleton in the presence of a rigid pillar of 4,4‧-Bpy. Additionally, photoluminescence properties of 1-5 were lastly investigated.

Electrochemical EDTA recycling after soil washing of Pb, Zn and Cd contaminated soil.

PubMed

Pociecha, Maja; Kastelec, Damijana; Lestan, Domen

2011-08-30

Recycling of chelant decreases the cost of EDTA-based soil washing. Current methods, however, are not effective when the spent soil washing solution contains more than one contaminating metal. In this study, we applied electrochemical treatment of the washing solution obtained after EDTA extraction of Pb, Zn and Cd contaminated soil. A sacrificial Al anode and stainless steel cathode in a conventional electrolytic cell at pH 10 efficiently removed Pb from the solution. The method efficiency, specific electricity and Al consumption were significantly higher for solutions with a higher initial metal concentration. Partial replacement of NaCl with KNO(3) as an electrolyte (aggressive Cl(-) are required to prevent passivisation of the Al anode) prevented EDTA degradation during the electrolysis. The addition of FeCl(3) to the acidified washing solution prior to electrolysis improved Zn removal. Using the novel method 98, 73 and 66% of Pb, Zn and Cd, respectively, were removed, while 88% of EDTA was preserved in the treated washing solution. The recycled EDTA retained 86, 84 and 85% of Pb, Zn and Cd extraction potential from contaminated soil, respectively. Copyright © 2011 Elsevier B.V. All rights reserved.

Determining provenance of marine metal pollution in French bivalves using Cd, Zn and Pb isotopes

NASA Astrophysics Data System (ADS)

Shiel, Alyssa E.; Weis, Dominique; Cossa, Daniel; Orians, Kristin J.

2013-11-01

Cadmium, Zn and Pb isotopic compositions (MC-ICP-MS) and elemental concentrations (HR-ICP-MS) have been used to distinguish between natural and anthropogenic sources of these metals in bivalves collected from the coastlines of France (English Channel, Atlantic and Mediterranean coasts). The Cd isotopic signatures (δ114Cd = -1.08‰ to -0.52‰) exhibited by bivalves from the coastlines of France, excluding those from NE France, are within the range of those exhibited by bivalves from the USA East coast (δ114Cd = -1.20‰ to -0.54‰). This indicates the high prevalence of industry, as well as the low natural contributions of Cd from North Atlantic waters in both regions. Thus, the significance of anthropogenic Cd sources is similar. These significant anthropogenic contributions are identified for bivalves with a large range in tissue Cd concentrations. Importantly, French bivalves from the Gironde estuary and Marennes-Oléron basin (regions of historic and modern importance for oyster farming, respectively) exhibited the highest Cd levels of the study. Their Cd isotopic signatures indicate historical smelting emissions remain the primary Cd source despite the cessation of local smelting activities in 1986 and subsequent remedial efforts. No significant variability is observed in the δ66Zn values of the French bivalves (∼0.53‰), with the exception of the much heavier compositions exhibited by oysters from the polluted Gironde estuary (1.19-1.27‰). Lead isotopes do not fractionate during processing like Cd and Zn. They can, therefore, be used to identify emissions from industrial processes and the consumption of unleaded gasoline and diesel fuel as metal sources to French bivalves. Cadmium and Zn isotopes are successfully used here as tracers of anthropogenic processing emissions and are combined with Pb isotope "fingerprinting" techniques to identify metal sources.

Nanoheterostructures with CdTe/ZnMgSeTe Quantum Dots for Single-Photon Emitters Grown by Molecular Beam Epitaxy

NASA Astrophysics Data System (ADS)

Sorokin, S. V.; Sedova, I. V.; Belyaev, K. G.; Rakhlin, M. V.; Yagovkina, M. A.; Toropov, A. A.; Ivanov, S. V.

2018-03-01

Data on the molecular beam epitaxy (MBE) technology, design, and luminescent properties of heterostructures with CdTe/Zn(Mg)(Se)Te quantum dots on InAs(001) substrates are presented. X-ray diffraction has been used to study short-period ZnTe/MgTe/MgSe superlattices used as wide-bandgap barriers in structures with CdTe/ZnTe quantum dots for the effective confinement of holes. It is shown that the design of these superlattices must take into account the replacement of Te atoms by selenium on MgSe/ZnTe and MgTe/MgSe heterointerfaces. Heterostructures with CdTe/Zn(Mg)(Se)Te quantum dots exhibit photoluminescence at temperatures up to 300 K. The spectra of microphotoluminescence at T = 10 K display a set of emission lines from separate CdTe/ZnTe quantum dots, the surface density of which is estimated at 1010 cm-2.

Decreasing Ni, Cu, Cd, and Zn heavy metal magnetite-bentonite nanocomposites and adsorption isotherm study

NASA Astrophysics Data System (ADS)

Eskandari, M.; Zakeri Khatir, M.; Khodadadi Darban, A.; Meshkini, M.

2018-04-01

This present study was conducted to investigate the effect of magnetite-bentonite nanocomposite on heavy metal removal from an effluent. For this purpose, magnetite-bentonite nanocomposite was prepared through the chemical method and characterized using x-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques, followed by studying the effect of produced nanocomposite on the removal of Ni2+, Cu2+, Cd2+, and Zn2+ heavy metal ions. The results showed that adsorption capacity of magnetite-bentonite nanocomposites for the studied ions is in the order of Zn2+ > Cd2+ > Cu2+ > Ni2+. Adsorption isotherms were drawn for Ni2+, Cu2+, Cd2+, and Zn2+ cations and found that cations adsorption on nanocomposite fit into Langmuir model.

Study on the mechanism of using IR illumination to improve the carrier transport performance of CdZnTe detector

NASA Astrophysics Data System (ADS)

Mao, Yifei; Zhang, Jijun; Lin, Liwen; Lai, Jianming; Min, Jiahua; Liang, Xiaoyan; Huang, Jian; Tang, Ke; Wang, Linjun

2018-04-01

Different wavelength IR light (770-1150 nm) was used to evaluate the effect of IR light on the carrier transport performance of CdZnTe detector. The effective mobility-lifetime product (μτ*) of CdZnTe achieved 10-2 cm2 V-1 when the IR wavelength was in the range of 820-920 nm, but decreased to 1 × 10-4 cm2 V-1 when the wavelength was longer than 920 nm. The mechanism about how IR light affecting the carrier transport property of CdZnTe detector was analyzed with Shockley-Read-Hall model. The defect of doubly ionized Cd vacancy ([VCd]2-) was found to be the main factor that assist IR light affecting the μτ of CdZnTe detector. The photoconductive experiment under 770-1150 nm IR illumination was carried out, and three kinds of photocurrent curve were detected and analyzed by solving the Hecht equation. The experiments demonstrated the effect of [VCd]2- defect on the carrier transport property of CdZnTe detector under IR illumination.

Core-shell solar cell fabrication using heterostructure of ZnO-nanowires arrays decorated with sputtered CdTe-nanoparticles

NASA Astrophysics Data System (ADS)

Akbarnejad, Elaheh; Dehghan Nayeri, Fatemeh; Ghoranneviss, Mahmood

2018-03-01

Core-shell heterostructures of ZnO-NWs/CdTe-NPs were fabricated through covering ZnO-NWs arrays using CdTe-NPs and the room temperature RF magnetron sputtering method. The influence of different CdTe-NPs deposition time (5, 20, 40 and 60 min) on the physical properties of core-shell heterostructures were investigated. In order to achieve the highest coverage level and a wide range of optical absorption at a visible range for a ZnO-NWs/CdTe-NPs (60 min) array, FTO/ZnO-NWs/CdTe-NPs (60 min)/Ni/Au core-shell solar cells were used. Solar cell fabrication was performed by soaking the samples in a saturated CdCl2 solution in methanol and a post-annealing treatment at 400 °C for 1 h in air which led to grain growth, the passivation of deep level defects, and the decrease of stacking faults. Short-circuit current and power conversion efficiency of the fabricated cell under illumination with visible light AM1.5 (100 mW cm-2) were 13.3 mA cm-2 and 3.41%, respectively. It was found that introducing a thin interfacial layer of CdSe to the configuration (FTO/ZnO-NWs/CdSe (10 nm)/CdTe-NPs (60 min)/Ni/Au) led to a 5.58% enhancement of photovoltaic performance of the solar cell (20.9 mA cm-2), which is 63.6% more than that of the same configuration without CdSe.

Preparation of cauliflower-like CdS/ZnS/ZnO nanostructure and its photoelectric properties

NASA Astrophysics Data System (ADS)

Liu, Zhifeng; Guo, Keying; Wang, Yun; Zheng, Xuerong; Ya, Jing; Li, Junwei; Han, Li; Liu, Zhichao; Han, Jianhua

2014-06-01

Cauliflower-like CdS/ZnS/ZnO nanostructure is fabricated via a simple hydrothermal method. Factors such as concentration of reaction solution, reaction temperature, as well as reaction time in the synthetic process are investigated, and the working mechanism of the nanostructure is suggested. Hydrogen generation efficiency of 4.69 % at 0.29 V versus saturated calomel electrode is achieved using synthesized nanostructure as electrode due to the improved absorption and appropriate energy gap structure, which is confirmed by enhanced absorption spectrum. The expected products have potential application in photoelectrochemical water splitting.

Remarkably Enhancing Green-Excitation Efficiency for Solar Energy Utilization: Red Phosphors Ba2ZnS3:Eu2+, X- Co-Doped Halide Ions (X = Cl, Br, I).

PubMed

Luo, Tingting; Du, Yun; Qiu, Zhongxian; Li, Yanmei; Wang, Xiaofang; Zhou, Wenli; Zhang, Jilin; Yu, Liping; Lian, Shixun

2017-05-15

Eu 2+ -activated Ba 2 ZnS 3 has been reported as a red phosphor with a broad emission band peaking at 650 nm under blue excitation for white-LED. In this study, Ba 2 ZnS 3 :Eu 2+ , X - (X = F, Cl, Br, I) phosphors doped with halide ions were prepared by traditional high-temperature solid-state reaction. Phase identification of powders was performed by X-ray powder diffraction analysis, confirming the existence of single-phase Ba 2 ZnS 3 crystals without dopant. The corresponding excitation spectra showed an additional broad band in the green region peaking at 550 nm when the phosphor was halogenated except by the smallest F - . It was proved that the green-excitation efficiency successively strengthened from Cl - , to Br - , to I - , which suggested larger halide ions made a greater contribution to the further splitting of the t 2g energy level of the doped Eu 2+ ions in the host Ba 2 ZnS 3 , and the optimized formula Ba 1.995 ZnS 2.82 :Eu 2+ 0.005 , I - 0.18 showed a potential application in solar spectral conversion for agricultural greenhouse and solar cell. Defect chemistry theory and crystal field theory provided insights into the key role of halide ions in enhancing green-excitation efficiency.

Electrodeposition of ZnO-doped films as window layer for Cd-free CIGS-based solar cells

NASA Astrophysics Data System (ADS)

Tsin, Fabien; Vénérosy, Amélie; Hildebrandt, Thibaud; Hariskos, Dimitrios; Naghavi, Negar; Lincot, Daniel; Rousset, Jean

2016-02-01

The Cu(In,Ga)Se2 (CIGS) thin film solar cell technology has made a steady progress within the last decade reaching efficiency up to 22.3% on laboratory scale, thus overpassing the highest efficiency for polycrystalline silicon solar cells. High efficiency CIGS modules employ a so-called buffer layer of cadmium sulfide CdS deposited by Chemical Bath Deposition (CBD), which presence and Cd-containing waste present some environmental concerns. A second potential bottleneck for CIGS technology is its window layer made of i-ZnO/ZnO:Al, which is deposited by sputtering requiring expensive vacuum equipment. A non-vacuum deposition of transparent conductive oxide (TCO) relying on simpler equipment with lower investment costs will be more economically attractive, and could increase competitiveness of CIGS-based modules with the mainstream silicon-based technologies. In the frame of Novazolar project, we have developed a low-cost aqueous solution photo assisted electrodeposition process of the ZnO-based window layer for high efficiency CIGS-based solar cells. The window layer deposition have been first optimized on classical CdS buffer layer leading to cells with efficiencies similar to those measured with the sputtered references on the same absorber (15%). The the optimized ZnO doped layer has been adapted to cadmium free devices where the CdS is replaced by chemical bath deposited zinc oxysulfide Zn(S,O) buffer layer. The effect of different growth parameters has been studied on CBD-Zn(S,O)-plated co-evaporated Cu(In,Ga)Se2 substrates provided by the Zentrum für Sonnenenergie-und Wasserstoff-Forschung (ZSW). This optimization of the electrodeposition of ZnO:Cl on CIGS/Zn(S,O) stacks led to record efficiency of 14%, while the reference cell with a sputtered (Zn,Mg)O/ZnO:Al window layer has an efficiency of 15.2%.

Extraction and isolation of the salidroside-type metabolite from zinc (Zn) and cadmium (Cd) hyperaccumulator Sedum alfredii Hance*

PubMed Central

Xing, Yan; Peng, Hong-yun; Li, Xia; Zhang, Meng-xi; Gao, Ling-ling; Yang, Xiao-e

2012-01-01

The active metabolite in the post-harvested biomass of zinc (Zn) and cadmium (Cd) hyperaccumulator Sedum alfredii Hance from phytoextraction is of great interest in China. The current study demonstrates that a salidroside-type metabolite can be yielded from the Zn/Cd hyperaccumulator S. alfredii biomass by means of sonication/ethanol extraction and macroporous resin column (AB-8 type) isolation. The concentrations of Zn and Cd in the salidroside-type metabolite were below the limitation of the national standards. PMID:23024051

Hydrothermal growth and luminescent properties of nonpolar a-plane (11 2 - 0) ZnCdO films for light-emitting diodes

NASA Astrophysics Data System (ADS)

Baik, Kwang Hyeon; Kim, Jimin; Jang, Soohwan

2018-03-01

Nonpolar a-plane ZnCdO films have been obtained on a-plane GaN using a simple low-cost hydrothermal growth method at the low temperature of 80 °C. The morphological, structural, optical, and electrical properties of a-plane ZnCdO films with various Cd contents have been investigated and compared. The photoluminescence peak of the a-plane Zn0.957Cd 0.043O film, was observed to be centered at 429 nm at 25 °C. We demonstrated a heterostructure light-emitting diode (LED) using nonpolar n-type Zn0.957Cd0.043O/p-type GaN films. The rectifying behavior of the current-voltage characteristics was observed with a turn-on voltage of 5 V. The electroluminescence of the LED showed emission peaks including 430 nm, which indicates the near-band-edge emission of a-plane Zn0.957Cd0.043O at 25 °C.

Synergistically enhanced photocatalytic hydrogen evolution performance of ZnCdS by co-loading graphene quantum dots and PdS dual cocatalysts under visible light

NASA Astrophysics Data System (ADS)

Wang, Fang; Su, Yanhong; Min, Shixiong; Li, Yanan; Lei, Yonggang; Hou, Jianhua

2018-04-01

Here, we report that the co-loading of graphene quantum dots (GQDs) and PdS dual cocatalysts on ZnCdS surface achieves a high efficiency photocatalytic H2 evolution under visible light (≥420 nm). The GQDs/ZnCdS/PdS photocatalyst was prepared by a facile two steps: hydrothermal coupling of GQDs on ZnCdS surface followed by an in-situ chemical deposition of PdS. The resulted GQDs/ZnCdS/PdS exhibits a H2 evolution rate of 517 μmol h-1, which is 15, 7, and 1.7 times higher than that of pure ZnCdS, GQDs/ZnCdS, and ZnCdS/PdS, respectively, demonstrating the synergistic effects of GQDs and PdS dual cocatalysts. A high apparent quantum efficiency (AQE) up to 22.4% can be achieved over GQDs/ZnCdS/PdS at 420 nm. GQDs/ZnCdS/PdS also has a relatively good stability. Such a considerable enhancement of photocatalytic activity was attributable to the co-loading of the GQDs and PdS as respective reduction and oxidation cocatalysts, leading to an efficient charge separation and surface reactions.

Mobility of Heavy Metals (Pb, Cd, Zn) in the Pampeano and Puelche Aquifers, Argentina: Partition and Retardation Coefficients.

PubMed

Jakomin, L M; Marbán, L; Grondona, S; Glok Galli, M; Martínez, D E

2015-09-01

The prediction about metals behaviour in soil requires knowledge on their solid-liquid partitioning. Usually it is expressed with an empirical distribution coefficient or Kd, which gives the ratio of the metal concentration in the solid phase to that in the solution. Kd values have been determined for Zn, Pb and Cd from samples representing the two most exploited aquifers in Argentina, Pampeano and Puelche, at three different locations in the province of Buenos Aires. The Pampeano aquifer presented higher Kd values than the Puelche aquifer. Comparing Kd values, different relationships could be observed: (a) Pampeano aquifer: Pb > Zn > Cd, and (b) Puelche aquifer: Pb > Cd > Zn. Kd for Cd seems to be linked to cationic exchange capacity, but solid phases precipitation can be more determining for Pb and Zn.

Improvement of the physical properties of ZnO/CdTe core-shell nanowire arrays by CdCl2 heat treatment for solar cells

PubMed Central

2014-01-01

CdTe is an important compound semiconductor for solar cells, and its use in nanowire-based heterostructures may become a critical requirement, owing to the potential scarcity of tellurium. The effects of the CdCl2 heat treatment are investigated on the physical properties of vertically aligned ZnO/CdTe core-shell nanowire arrays grown by combining chemical bath deposition with close space sublimation. It is found that recrystallization phenomena are induced by the CdCl2 heat treatment in the CdTe shell composed of nanograins: its crystallinity is improved while grain growth and texture randomization occur. The presence of a tellurium crystalline phase that may decorate grain boundaries is also revealed. The CdCl2 heat treatment further favors the chlorine doping of the CdTe shell with the formation of chlorine A-centers and can result in the passivation of grain boundaries. The absorption properties of ZnO/CdTe core-shell nanowire arrays are highly efficient, and more than 80% of the incident light can be absorbed in the spectral range of the solar irradiance. The resulting photovoltaic properties of solar cells made from ZnO/CdTe core-shell nanowire arrays covered with CuSCN/Au back-side contact are also improved after the CdCl2 heat treatment. However, recombination and trap phenomena are expected to operate, and the collection of the holes that are mainly photo-generated in the CdTe shell from the CuSCN/Au back-side contact is presumably identified as the main critical point in these solar cells. PMID:24910576

Noble-metal-free NiO@Ni-ZnO/reduced graphene oxide/CdS heterostructure for efficient photocatalytic hydrogen generation

NASA Astrophysics Data System (ADS)

Chen, Fayun; Zhang, Laijun; Wang, Xuewen; Zhang, Rongbin

2017-11-01

Noble-metal-free semiconductor materials are widely used for photocatalytic hydrogen generation because of their low cost. ZnO-based heterostructures with synergistic effects exhibit an effective photocatalytic activity. In this work, NiO@Ni-ZnO/reduced graphene oxide (rGO)/CdS heterostructures are synthesized by a multi-step method. rGO nanosheets and CdS nanoparticles were introduced into the heterostructures via a redox reaction and light-assisted growth, respectively. A novel Ni-induced electrochemical growth method was developed to prepare ZnO rods from Zn powder. NiO@Ni-ZnO/rGO/CdS heterostructures with a wide visible-light absorption range exhibited highly photocatalytic hydrogen generation rates under UV-vis and visible light irradiation. The enhanced photocatalytic activity is attributed to the Ni nanoparticles that act as cocatalysts for capturing photoexcited electrons and the improved synergistic effect between ZnO and CdS due to the rGO nanosheets acting as photoexcited carrier transport channels.

Gas-sensing performances of Cd-doped ZnO nanoparticles synthesized by a surfactant-mediated method for n-butanol gas

NASA Astrophysics Data System (ADS)

Zhao, Rongjun; Li, Kejin; Wang, Zhezhe; Xing, Xinxin; Wang, Yude

2018-01-01

Zinc oxide nanoparticles with the different Cd doping contents were prepared by with a surfactant-mediated method in this paper. The effects of Cd doping on the gas sensing properties of the ZnO nanoparticles were studied. The morphology and microstructure of as-prepared samples were characterized by X-ray diffraction (XRD); scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM), respectively. The results reveal that all the products are the high crystalline hexagonal wurtzite ZnO crystal structure. The gas-sensing characteristics of the Cd doped ZnO nanoparticles for volatile organic compounds (VOCs) were investigated. At its optimal operation temperature of 300 °C, the sensing properties of the Cd doped ZnO nanoparticles for n-butanol gas exhibit a high-performance gas sensing performances including high gas response, good selectivity, response/recovery time, and repeatability as well as stability. Especially, its response reaches 130 for 100 ppm n-butanol of ZnO nanoparticles with 2.5% Cd doping. Those values demonstrate the potential of using as-prepared Cd doped ZnO nanoparticles for n-butanol gas detection, making them to be promising candidates for practical detectors to n-butanol gas. Apart from these, the mechanism related to the advanced properties was also investigated and presented.

Zn doped CdO thin films with enhanced linear and third order nonlinear optical properties for optoelectronic applications

NASA Astrophysics Data System (ADS)

Bairy, Raghavendra; Jayarama, A.; Shivakumar, G. K.; Patil, P. S.; Bhat, K. Udaya

2018-04-01

Thin films of undoped and zinc doped CdO have been deposited on glass substrate using spray pyrolysis technique with various dopant concentrations of Zn such as 1, 5 and 10%. Influence of Zn doping on CdO thin films for the structural, morphological, optical and nonlinear optical properties are reported. XRD analysis reveals that as prepared pure and Zn doped CdO films show polycrystalline nature with face centered cubic structure. Also, Zn doping does not significantly modify the crystallinity and not much increase in the crystallite size of the film. SEM images shows grains which are uniform and grain size with increase in dopant concentration. The transmittance of the prepared CdO films recorded in the UV visible spectra and it shows 50 to 60% in the visible region. The estimated optical band gap increases from 2.60 to 2.70 eV for various dopant concentrations. The nonlinear optical absorption of Zn-doped CdO films have been measured used the Z-scan technique at a wavelength 532 nm. The nonlinear optical absorption coefficient (β), nonlinear refractive index (n2) and the third order nonlinear optical susceptibility (χ(3)) of the pure and Zn doped films were determined.

Characteristics of depth-sensing coplanar grid CdZnTe detectors

NASA Astrophysics Data System (ADS)

He, Zhong; Sturm, Ben W.

2005-12-01

The latest depth-sensing coplanar grid CdZnTe detectors have been tested. Two of these have dimensions 1.5×1.5×1.0 cm 3 and one is a cylindrical detector with 1.5 cm diameter and 1.0 cm length, all of them using the third-generation coplanar anode design. Energy resolutions of 2.0% and 2.4% FWHM at 662 keV γ-ray energies were obtained. Detector performance has been observed experimentally as a function of depth of the γ-ray interaction, and as a function of radial position near the anode surface. The measured results show the improvement of the third-generation anode design. Material uniformity of CdZnTe crystals manufactured by eV Products have been directly observed and compared on two 1.5×1.5×1.0 cm 3 detectors.

Stability of Cd 1–xZn xO yS 1–y Quaternary Alloys Assessed with First-Principles Calculations

DOE PAGES

Varley, Joel B.; He, Xiaoqing; Rockett, Angus; ...

2017-02-08

One route to decreasing the absorption in CdS buffer layers in Cu(In,Ga)Se 2 and Cu 2ZnSn(S,Se) 4 thin-film photovoltaics is by alloying. Here we use first-principles calculations based on hybrid functionals to assess the energetics and stability of quaternary Cd, Zn, O, and S (Cd 1–xZn xO yS 1–y) alloys within a regular solution model. Our results identify that full miscibility of most Cd 1–xZn xO yS 1–y compositions and even binaries like Zn(O,S) is outside typical photovoltaic processing conditions. Finally, the results suggest that the tendency for phase separation of the oxysulfides may drive the nucleation of other phasesmore » such as sulfates that have been increasingly observed in oxygenated CdS and ZnS.« less

Stability of Cd 1–xZn xO yS 1–y Quaternary Alloys Assessed with First-Principles Calculations

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

Varley, Joel B.; He, Xiaoqing; Rockett, Angus

One route to decreasing the absorption in CdS buffer layers in Cu(In,Ga)Se 2 and Cu 2ZnSn(S,Se) 4 thin-film photovoltaics is by alloying. Here we use first-principles calculations based on hybrid functionals to assess the energetics and stability of quaternary Cd, Zn, O, and S (Cd 1–xZn xO yS 1–y) alloys within a regular solution model. Our results identify that full miscibility of most Cd 1–xZn xO yS 1–y compositions and even binaries like Zn(O,S) is outside typical photovoltaic processing conditions. Finally, the results suggest that the tendency for phase separation of the oxysulfides may drive the nucleation of other phasesmore » such as sulfates that have been increasingly observed in oxygenated CdS and ZnS.« less

Subcellular compartmentalization of Cd and Zn in two bivalves. I. Significance of metal-sensitive fractions (MSF) and biologically detoxified metal (BDM)

USGS Publications Warehouse

Wallace, W.G.; Lee, B.-G.; Luoma, S.N.

2003-01-01

Many aspects of metal accumulation in aquatic invertebrates (i.e. toxicity, tolerance and trophic transfer) can be understood by examining the subcellular partitioning of accumulated metal. In this paper, we use a compartmentalization approach to interpret the significance of metal, species and size dependence in the subcellular partitioning of Cd and Zn in the bivalves Macoma balthica and Potamocorbula amurensis. Of special interest is the compartmentalization of metal as metal-sensitive fractions (MSF) (i.e. organelles and heat-sensitive proteins, termed 'enzymes' hereafter) and biologically detoxified metal (BDM) (i.e. metallothioneins [MT] and metal-rich granules [MRG]). Clams from San Francisco Bay, CA, were exposed for 14 d to seawater (20??? salinity) containing 3.5 ??g l-1 Cd and 20.5 ??g l-1 Zn, including 109Cd and 65Zn as radiotracers. Uptake was followed by 21 d of depuration. The subcellular partitioning of metal within clams was examined following exposure and loss. P. amurensis accumulated ???22x more Cd and ???2x more Zn than M. balthica. MT played an important role in the storage of Cd in P. amurensis, while organelles were the major site of Zn accumulation. In M. balthica, Cd and Zn partitioned similarly, although the pathway of detoxification was metal-specific (MRG for Cd; MRG and MT for Zn). Upon loss, M. balthica depurated ???40% of Cd with Zn being retained; P. amurensis retained Cd and depurated Zn (???40%). During efflux, Cd and Zn concentrations in the MSF compartment of both clams declined with metal either being lost from the animal or being transferred to the BDM compartment. Subcellular compartmentalization was also size-dependent, with the importance of BDM increasing with clam size; MSF decreased accordingly. We hypothesized that progressive retention of metal as BDM (i.e. MRG) with age may lead to size dependency of metal concentrations often observed in some populations of M. balthica.

Influence of Illumination on the Electrical Properties of p-(ZnMgTe/ZnTe:N)/CdTe/n-(CdTe:I)/GaAs Heterojunction Grown by Molecular Beam Epitaxy (MBE)

NASA Astrophysics Data System (ADS)

Jum'h, I.; Abd El-Sadek, M. S.; Al-Taani, H.; Yahia, I. S.; Karczewski, G.

2017-02-01

Heterostructure p-(ZnMgTe/ZnTe:N)/CdTe/n-(CdTe:I)/GaAs was evaporated using molecular beam epitaxy and investigated for photovoltaic energy conversion application. The electrical properties of the studied heterostructure were measured and characterized in order to understand the relevant electrical transport mechanisms. Electrical properties derived from the current-voltage ( I- V) characteristics of solar cells provide essential information necessary for the analysis of performance losses and device efficiency. I- V characteristics are investigated in dark conditions and under different light intensities. All the electrical and power parameters of the heterostructure were measured, calculated and explained.

Differences in Cd and Zn bioaccumulation for the flood-tolerant Salix cinerea rooting in seasonally flooded contaminated sediments.

PubMed

Vandecasteele, Bart; Laing, Gijs Du; Quataert, Paul; Tack, Filip M G

2005-04-01

Several authors suggest that a hydrological regime aiming at wetland creation is a potential management option that favours reducing bioavailability for metal-contaminated sites. The hydrological conditions on a site constitute one of the many factors that may affect the availability of potentially toxic trace metals for uptake by plants. Bioavailability of Cd, Mn and Zn on a contaminated dredged sediment landfill (DSL) with variable duration of submersion was evaluated by measuring metal concentrations in the wetland plant species Salix cinerea in field conditions. Longer submersion periods in the field caused lower Cd and Zn concentrations in the leaves in the first weeks of the growing season. Foliar Cd and Zn concentrations at the end of the growing season were highest on the initially flooded plot that emerged early in the growing season. Foliar Zn concentrations were also high at a sandy-textured oxic plot with low soil metal concentrations. Zn uptake in the leaves was markedly slower than Cd uptake for trees growing on soils with prolonged waterlogging during the growing season, pointing at a different availability. Zn availability was lowest when soil was submerged, but metal transfer from stems and twigs to leaves may mask the lower availability of Cd in submerged soils. Especially for Cd, a transfer effect from one growing season to the next season was observed: oxic conditions at the end of the previous growing season seem to determine at least partly the foliar concentrations for S. cinerea through this metal transfer mechanism. Duration of the submersion period is a key factor for bioavailability inasmuch as initially submerged soils emerging only in the second half of the growing season resulted in elevated Cd and Zn foliar concentrations at that time.

Cu-doped Cd1- x Zn x S alloy: synthesis and structural investigations

NASA Astrophysics Data System (ADS)

Yadav, Indu; Ahlawat, Dharamvir Singh; Ahlawat, Rachna

2016-03-01

Copper doped Cd1- x Zn x S ( x ≤ 1) quantum dots have been synthesized using chemical co-precipitation method. Structural investigation of the synthesized nanomaterials has been carried out by powder XRD method. The XRD results have confirmed that as-prepared Cu-doped Cd1- x Zn x S quantum dots have hexagonal structure. The average nanocrystallite size was estimated in the range 2-12 nm using Debye-Scherrer formula. The lattice constants, lattice plane, d-spacing, unit cell volume, Lorentz factor and dislocation density were also calculated from XRD data. The change in particle size was observed with the change in Zn concentration. Furthermore, FTIR spectra of the prepared samples were observed for identification of COO- and O-H functional groups. The TEM study has also reported the same size range of nanoparticles. The increase in agglomeration has been observed with the increase in Zn concentration in the prepared samples.

Investigation of site preference of Zn doped Ba{sub 3}Co{sub 2−x}Zn{sub x}Fe{sub 24}O{sub 41} by Mössbauer spectroscopy

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

Lim, Jung Tae; Kim, Chul Sung, E-mail: cskim@kookmin.ac.kr

2014-05-07

The polycrystalline Ba{sub 3}Co{sub 2−x}Zn{sub x}Fe{sub 24}O{sub 41} (x = 0.0, 0.5, 1.0) samples were prepared by using solid-state-reaction method. The crystal structures and magnetic properties of samples were investigated with x-ray diffractometer, vibrating sample magnetometer, and Mössbauer spectroscopy. The crystal structure of Ba{sub 3}Co{sub 2−x}Zn{sub x}Fe{sub 24}O{sub 41} (x = 0.0, 0.5, 1.0) samples was determined to be a hexagonal structure with P6{sub 3}/mmc space group at 295 K, and the saturation magnetization (M{sub s}) of Ba{sub 3}Co{sub 2−x}Zn{sub x}Fe{sub 24}O{sub 41} (x = 0.0, 0.5, 1.0) samples were found to be M{sub s} = 50.9, 53.1, 55.0 emu/g, respectively. From the temperature dependence of magnetizationmore » curves under 100 Oe between 4.2 and 740 K, we were able to observe the spin transition, and both spin transition temperature (T{sub s}) and Curie temperature (T{sub C}) decrease with increasing Zn concentration. Mössbauer spectra of all samples were obtained and analyzed at various temperatures ranging from 4.2 to 295 K. With ten-sextets for Fe sites corresponding to the Z-type hexagonal crystallographic sites, all spectra below T{sub C} were fitted by least-square method. In addition, from the site occupation numbers of Fe, calculated from the relative areas fitted to the Mössbauer spectra, we find that Zn ions preferentially occupy the tetrahedral sublattices of down sites.« less

A ceramic microreactor for the synthesis of water soluble CdS and CdS/ZnS nanocrystals with on-line optical characterization

NASA Astrophysics Data System (ADS)

Pedro, Sara Gómez-De; Puyol, Mar; Izquierdo, David; Salinas, Iñigo; de La Fuente, J. M.; Alonso-Chamarro, Julián

2012-02-01

In this paper, a computer controlled microreactor to synthesize water soluble CdS and CdS/ZnS nanocrystals with in situ monitoring of the reaction progress is developed. It is based on ceramic tapes and the Low-Temperature Co-fired Ceramics technology (LTCC). As well the microsystem set-up, the microreactor fluidic design has also been thoroughly optimized. The final device is based on a hydrodynamic focusing of the reagents followed by a three-dimensional micromixer. This generates monodispersed and stable CdS and core-shell CdS/ZnS nanocrystals of 4.5 and 4.2 nm, respectively, with reproducible optical properties in terms of fluorescence emission wavelengths, bandwidth, and quantum yields, which is a key requirement for their future analytical applications. The synthetic process is also controlled in real time with the integration of an optical detection system for absorbance and fluorescence measurements based on commercial miniaturized optical components. This makes possible the efficient managing of the hydrodynamic variables to obtain the desired colloidal suspension. As a result, a simple, economic, robust and portable microsystem for the well controlled synthesis of CdS and CdS/ZnS nanocrystals is presented. Moreover, the reaction takes place in aqueous medium, thus allowing the direct modular integration of this microreactor in specific analytical microsystems, which require the use of such quantum dots as labels.

Thermoelectric properties of AMg 2X 2, AZn 2Sb 2 (A = Ca, Sr, Ba; X = Sb, Bi), and Ba 2ZnX 2 (X = Sb, Bi) Zintl compounds

DOE PAGES

Sun, Jifeng; Singh, David J.

2017-04-03

In this paper, we report a theoretical investigation of the electronic structure and transport properties of eleven Zintl compounds including nine 122 phases (AMg 2X 2, AZn 2Sb 2 (A = Ca, Sr, Ba; X = Sb, Bi)) and two 212 phases (Ba 2ZnX 2 (X = Sb, Bi)). The electronic structures and electrical transport properties are studied using ab initio calculations and semi-classical Boltzmann theory within the constant relaxation time approximation. All the compounds are semiconducting. We find that the n-type 122 phases with the CaAl 2Si 2 structure type show better performance than p-type materials due to themore » multi-valley degeneracy with anisotropic carrier pockets at and near the conduction band minimum. The pocket anisotropy is beneficial in achieving high conductivity and Seebeck coefficient simultaneously. This mechanism yields substantial improvement in the power factor. Finally, the general performance of 212 phases is inferior to that of the 122 phases, with the Ba 2ZnSb 2 compound showing better performance.« less

Accumulation of Cd, Cu and Zn in shoots of maize (Zea mays L.) exposed to 0.8 or 20 nM Cd during vegetative growth and the relation with xylem sap composition.

PubMed

Nguyen, C; Soulier, A J; Masson, P; Bussière, S; Cornu, J Y

2016-02-01

This work focuses on the exposure of maize plants to nanomolar concentrations of Cd, which is relevant for agricultural soils cropped with food and feed plants. Maize plants were cultivated in nutrient solution at 0.8 or 20 nM Cd during the vegetative growth stages. No significant hormesis or toxic effects of Cd were observed on maize growth, but a decrease in the allocation of Cd to shoots between the 0.8 and 20 nM Cd exposures revealed that the plants already responded to these low concentrations of Cd according to a shoot Cd excluder strategy. The Cd, Cu and Zn concentrations in shoots decreased with time as the result of an early decrease in the root/shoot ratio and of a decrease in the coefficient of allocation to aboveground for Zn and Cd at 20 nM. As a consequence, shoots of young plants were richer in micronutrients Cu and Zn but also in toxic Cd. The rate of delivery of Cd, Cu and Zn from xylem sap was successfully used to predict the time course of concentrations of Cd, Cu and Zn in the shoot. However, it overestimated the actual concentrations of Cd in the shoot, presumably because the reallocation of this trace element from shoots back to roots was not taken into account.

Luminescence of polyethylene glycol coated CdSeTe/ZnS and InP/ZnS nanoparticles in the presence of copper cations.

PubMed

Beaune, Grégory; Tamang, Sudarsan; Bernardin, Aude; Bayle-Guillemaud, Pascale; Fenel, Daphna; Schoehn, Guy; Vinet, Françoise; Reiss, Peter; Texier, Isabelle

2011-08-22

The use of click chemistry for quantum dot (QD) functionalization could be very promising for the development of bioconjugates dedicated to in vivo applications. Alkyne-azide ligation usually requires copper(I) catalysis. The luminescence response of CdSeTe/ZnS nanoparticles coated with polyethylene glycol (PEG) is studied in the presence of copper cations, and compared to that of InP/ZnS QDs coated with mercaptoundecanoic acid (MUA). The quenching mechanisms appear different. Luminescence quenching occurs without any wavelength shift in the absorption and emission spectra for the CdSeTe/ZnS/PEG nanocrystals. In this case, the presence of copper in the ZnS shell is evidenced by energy-filtered transmission electron microscopy (EF-TEM). By contrast, in the case of InP/ZnS/MUA nanocrystals, a redshift of the excitation and emission spectra, accompanied by an increase in absorbance and a decrease in photoluminescence, is observed. For CdSeTe/ZnS/PEG nanocrystals, PL quenching is enhanced for QDs with 1) smaller inorganic-core diameter, 2) thinner PEG shell, and 3) hydroxyl terminal groups. Whereas copper-induced PL quenching can be interesting for the design of sensitive cation sensors, copper-free click reactions should be used for the efficient functionalization of nanocrystals dedicated to bioapplications, in order to achieve highly luminescent QD bioconjugates. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A comparative analysis of green synthesis approach starch capped metal oxides (ZnO & CdO) nanoparticles and its bacterial activity

NASA Astrophysics Data System (ADS)

Vidhya, K.; Devarajan, V. P.; Viswanathan, C.; Nataraj, D.; Bhoopathi, G.

2013-06-01

In this study, we have investigated the bacterial activity of starch capped ZnO & CdO NPs. The NPs were prepared through green technique under room temperature and then obtained samples were characterized by using XRD and PL techniques. XRD pattern confirms the crystal nature it shows hexagonal structure for ZnO NPs and monoclinic structure for CdO NPs and their average particle size is ±20 nm. Further, the optical properties of NPs were investigated using PL technique in which the starch capped ZnO NPs shows maximum emission at 440 nm whereas starch capped CdO NPs shows maximum emission at 545 nm. Finally, toxic test was performed with E.coli bacteria and their results were investigated. Hence, starch capped ZnO NPs induced less killing effect when compared with starch capped CdO NPs. Therefore, we conclude that the starch capped ZnO NPs may be less toxic to microorganisms when compared with starch capped CdO NPs. In addition, starch capped ZnO NPs is also suitable for anti-microbial activity.

Constructing Cd0.5Zn0.5S@ZIF-8 nanocomposites through self-assembly strategy to enhance Cr(VI) photocatalytic reduction.

PubMed

Qiu, Jianhao; Zhang, Xiong-Fei; Zhang, Xingguang; Feng, Yi; Li, Yuxin; Yang, Lvye; Lu, Haiqiang; Yao, Jianfeng

2018-05-05

A novel and highly efficient photocatalyst of Cd 0.5 Zn 0.5 S@ZIF-8 nanocomposite has been developed by a facile self-assembly strategy. This is the first report on the application of Cd x Zn 1-x S and metal-organic framework (MOF) nanocomposite as photocatalysts for the reduction of Cr(VI). The resulting Cd 0.5 Zn 0.5 S@ZIF-8 exhibited higher photocatalytic activity than that of pristine Cd 0.5 Zn 0.5 S and ZIF-8. Particularly, the CZS@Z60 composite with 60 wt% of ZIF-8 exhibited a photocatalytic activity that is about 1.6 times as high as that of Cd 0.5 Zn 0.5 S. The dominant reason for the improved photocatalytic reduction potential is proved to be the newly-formed interfacial SZn bonds that firmly connect Cd 0.5 Zn 0.5 S and ZIF-8 and substantially improve the separation efficiency of photo-excited electrons and holes. The newly-formed chemical bonds are confirmed by XPS analyses, and the prolonged lifetime of photo-excited electrons is evidenced by the electrochemical measurement of photocurrent, which shows that the photocurrent on Cd 0.5 Zn 0.5 S@ZIF-8 is much higher than that of Cd 0.5 Zn 0.5 S and ZIF-8. This study clearly demonstrates that the MOF-based composite nanomaterials hold great promises for applications in the field of environmental remediation and for design of novel photocatalytic materials. Copyright © 2018 Elsevier B.V. All rights reserved.

Electron-beam pumped laser structures based on MBE grown {ZnCdSe}/{ZnSe} superlattices

NASA Astrophysics Data System (ADS)

Kozlovsky, V. I.; Shcherbakov, E. A.; Dianov, E. M.; Krysa, A. B.; Nasibov, A. S.; Trubenko, P. A.

1996-02-01

Cathodoluminescence (CL), photoreflection (PR), phototransmission (PT) of single and multiquantum wells (MQWs) and strain layer {ZnCdSe}/{ZnSe} superlattices (SLs) grown by molecular beam epitaxy (MBE) were studied. An increase of the Stokes shift with the number of quantum wells (QWs) and the appearance of new lines in CL and PT spectra were observed. Room temperature (RT) vertical-cavity surface-emitting laser (VCSEL) operation was achieved by using the SL structures. Output power up to 2.2 W in single longitudinal mode with λ = 493 nm was obtained. Cut facet laser wavelength of the same SL structure was 502 nm.

Wet Pretreatment-Induced Modification of Cu(In,Ga)Se2/Cd-Free ZnTiO Buffer Interface.

PubMed

Hwang, Suhwan; Larina, Liudmila; Lee, Hojin; Kim, Suncheul; Choi, Kyoung Soon; Jeon, Cheolho; Ahn, Byung Tae; Shin, Byungha

2018-06-20

We report a novel Cd-free ZnTiO buffer layer deposited by atomic layer deposition for Cu(In,Ga)Se 2 (CIGS) solar cells. Wet pretreatments of the CIGS absorbers with NH 4 OH, H 2 O, and/or aqueous solution of Cd 2+ ions were explored to improve the quality of the CIGS/ZnTiO interface, and their effects on the chemical state of the absorber and the final performance of Cd-free CIGS devices were investigated. X-ray photoelectron spectroscopy (XPS) analysis revealed that the aqueous solution etched away sodium compounds accumulated on the CIGS surface, which was found to be detrimental for solar cell operation. Wet treatment with NH 4 OH solution led to a reduced photocurrent, which was attributed to the thinning (or removal) of an ordered vacancy compound (OVC) layer on the CIGS surface as evidenced by an increased Cu XPS peak intensity after the NH 4 OH treatment. However, the addition of Cd 2+ ions to the NH 4 OH aqueous solution suppressed the etching of the OVC by NH 4 OH, explaining why such a negative effect of NH 4 OH is not present in the conventional chemical bath deposition of CdS. The band alignment at the CIGS/ZnTiO interface was quantified using XPS depth profile measurements. A small cliff-like conduction band offset of -0.11 eV was identified at the interface, which indicates room for further improvement of efficiency of the CIGS/ZnTiO solar cells once the band alignment is altered to a slight spike by inserting a passivation layer with a higher conduction band edge than ZnTiO. Combination of the small cliff conduction band offset at the interface, removal of the Na compound via water, and surface doping by Cd ions allowed the application of ZnTiO buffer to CIGS treated with Cd solutions, exhibiting an efficiency of 80% compared to that of a reference CIGS solar cell treated with the CdS.

Structure refinement of Zn and Pr-doped Y-Ba-Cu-oxides

NASA Astrophysics Data System (ADS)

Naik, M. S.; Sarode, P. R.; Priolkar, K. R.; Prabhu, R. B.

2018-05-01

Superconducting compounds of composition Y0.9 Pr0.1Ba2 [Cu1-yZny]3O7-δ (0 ≤ y ≤ 0.10) have been synthesized. The structure of these materials has been studied using powder X-ray diffraction technique and refinement has been carried out by using Rietveld refinement procedure. It has been shown that all these compounds crystallize in orthorhombic structure with slight change in c parameter. Increase of parameter O(2) and decrease of parameter O(3)suggest the changes in the Cu-O2 plane of these orthorhombic materials on Zn substitution.

The influence of annealing temperature on the interface and photovoltaic properties of CdS/CdSe quantum dots sensitized ZnO nanorods solar cells.

PubMed

Qiu, Xiaofeng; Chen, Ling; Gong, Haibo; Zhu, Min; Han, Jun; Zi, Min; Yang, Xiaopeng; Ji, Changjian; Cao, Bingqiang

2014-09-15

Arrays of ZnO/CdS/CdSe core/shell nanocables with different annealing temperatures have been investigated for CdS/CdSe quantum dots sensitized solar cells (QDSSCs). CdS/CdSe quantum dots were synthesized on the surface of ZnO nanorods that serve as the scaffold via a simple ion-exchange approach. The uniform microstructure was verified by scanning electron microscope and transmission electron microscope. UV-Visible absorption spectrum and Raman spectroscopy analysis indicated noticeable influence of annealing temperature on the interface structural and optical properties of the CdS/CdSe layers. Particularly, the relationship between annealing temperatures and photovoltaic performance of the corresponding QDSSCs was investigated employing photovoltaic conversion, quantum efficiency and electrochemical impedance spectra. It is demonstrated that higher cell efficiency can be obtained by optimizing the annealing temperature through extending the photoresponse range and improving QD layer crystal quality. Copyright © 2014 Elsevier Inc. All rights reserved.

CdS/ZnS core-shell nanocrystal photosensitizers for visible to UV upconversion.

PubMed

Gray, Victor; Xia, Pan; Huang, Zhiyuan; Moses, Emily; Fast, Alexander; Fishman, Dmitry A; Vullev, Valentine I; Abrahamsson, Maria; Moth-Poulsen, Kasper; Lee Tang, Ming

2017-08-01

Herein we report the first example of nanocrystal (NC) sensitized triplet-triplet annihilation based photon upconversion from the visible to ultraviolet (vis-to-UV). Many photocatalyzed reactions, such as water splitting, require UV photons in order to function efficiently. Upconversion is one possible means of extending the usable range of photons into the visible. Vis-to-UV upconversion is achieved with CdS/ZnS core-shell NCs as the sensitizer and 2,5-diphenyloxazole (PPO) as annihilator and emitter. The ZnS shell was crucial in order to achieve any appreciable upconversion. From time resolved photoluminescence and transient absorption measurements we conclude that the ZnS shell affects the NC and triplet energy transfer (TET) from NC to PPO in two distinct ways. Upon ZnS growth the surface traps are passivated thus increasing the TET. The shell, however, also acts as a tunneling barrier for TET, reducing the efficiency. This leads to an optimal shell thickness where the upconversion quantum yield ( Φ ' UC ) is maximized. Here the maximum Φ ' UC was determined to be 5.2 ± 0.5% for 4 monolayers of ZnS shell on CdS NCs.

Cd-free buffer layer materials on Cu2ZnSn(SxSe1-x)4: Band alignments with ZnO, ZnS, and In2S3

NASA Astrophysics Data System (ADS)

Barkhouse, D. Aaron R.; Haight, Richard; Sakai, Noriyuki; Hiroi, Homare; Sugimoto, Hiroki; Mitzi, David B.

2012-05-01

The heterojunctions formed between Cu2ZnSn(SxSe1-x)4 (CZTSSe) and three Cd-free n-type buffers, ZnS, ZnO, and In2S3, were studied using femtosecond ultraviolet photoemission and photovoltage spectroscopy. The electronic properties including the Fermi level location at the interface, band bending in the CZTSSe substrate, and valence and conduction band offsets were determined and correlated with device properties. We also describe a method for determining the band bending in the buffer layer and demonstrate this for the In2S3/CZTSSe system. The chemical bath deposited In2S3 buffer is found to have near optimal conduction band offset (0.15 eV), enabling the demonstration of Cd-free In2S3/CZTSSe solar cells with 7.6% power conversion efficiency.

Surface Passivation of CdZnTe Detector by Hydrogen Peroxide Solution Etching

NASA Technical Reports Server (NTRS)

Hayes, M.; Chen, H.; Chattopadhyay, K.; Burger, A.; James, R. B.

1998-01-01

The spectral resolution of room temperature nuclear radiation detectors such as CdZnTe is usually limited by the presence of conducting surface species that increase the surface leakage current. Studies have shown that the leakage current can be reduced by proper surface preparation. In this study, we try to optimize the performance of CdZnTe detector by etching the detector with hydrogen peroxide solution as function of concentration and etching time. The passivation effect that hydrogen peroxide introduces have been investigated by current-voltage (I-V) measurement on both parallel strips and metal-semiconductor-metal configurations. The improvements on the spectral response of Fe-55 and 241Am due to hydrogen peroxide treatment are presented and discussed.

[Cd, Cu, Zn and Pb contents and forms in soils and rapeseeds around Wuhu Plant].

PubMed

Wang, Xingming; Liu, Dengyi; Tu, Junfang; Li, Zheng; Wang, Youbao

2005-10-01

The study showed that around Wuhu Plant, soil Cd, Zn and Pb mainly existed in Fe-Mn oxide form, and Cu in residual form, with the percentage of 31.81%, 39.83%, 53.79%, and 46.24%, respectively. Soil exchangeable Cd and Pb had a higher proportion (23.47% and 16.32%) than soil exchangeable Cu and Zn (3.14% and 0.54%). The correlations between soil heavy metals and their forms, as well as their transformation to available form were different. Different heavy metals had different accumulation trends in rapeseed and its hull. Cu easily accumulated in hull, while Cd, Zn and Pb had a higher accumulation in seed. The accumulation rate of heavy metals in rapeseed and hull was also different, being the highest for Cd. There was a significantly negative correlation (P < 0.05) between the accumulation rate of heavy metals and their contents in soil. In rapeseed, Cd, Cu and Pb were mainly in sodium hydroxide form, with the percentage of 32.50%, 22.94% and 34.69%, respectively, while Zn was mainly in EDTA form, with a percentage of 45.97. The existed forms of heavy metals in rapeseed probably affected their toxicity, but the toxicity to human food could not be inferred from this research, and needed to be studied further. There was a weak relation between heavy metals contents and their existed forms in rapeseed.

White random lasing in mixture of ZnSe, CdS and CdSSe micropowders

NASA Astrophysics Data System (ADS)

Alyamani, A. Y.; Leanenia, M. S.; Alanazi, L. M.; Aljohani, M. M.; Aljariwi, A. A.; Rzheutski, M. V.; Lutsenko, E. V.; Yablonskii, G. P.

2016-03-01

Room temperature random lasing with white light emission in a mixture of AIIBVI semiconductor powders was achieved for the first time. The scattering gain media was formed by the mixture of closely packed active micron sized crystallites of ZnSe, CdS, CdSSe semiconductors. The micropowders were produced by grinding bulk crystals of each compound. Optical excitation was performed by 10-nanosecond pulses of tuned Ti:Al2O3-laser at 390 nm. The lasing in the mixture of semiconductor powders was achieved simultaneously at four wavelengths in blue, green, yellow and red spectral regions after exceeding the threshold excitation power density. A drastic integral intensity increase, spectrum narrowing and appearance of mode structure accompanied the laser action. ZnSe crystallites produce the laser light at about 460 nm while CdS particles - at about 520 nm. Two types of CdSSe semiconductor micropowders with different sulfur content lase at 580 nm and 660 nm. The threshold excitation power densities for all laser lines in the emission spectrum are approximately the same of about 0.9 MW/cm2. The sum of the emission spectrum of the mixture of the micropowders forms white light with high brightness. Lasing is due to an appearance of random feedback for amplified radiation in the active medium of closely packed light scattering crystallites. The presented results may find their applications for visualization systems, lighting technology, data transmission, medicine as biosensors and in identification systems. The key feature of random lasers is low cost of its production and possibility to be deposited on any type of surface.

Recovery of zinc and cadmium from spent batteries using Cyphos IL 102 via solvent extraction route and synthesis of Zn and Cd oxide nanoparticles.

PubMed

Singh, Rashmi; Mahandra, Harshit; Gupta, Bina

2017-09-01

The overall aim of this study is to separate and recover zinc and cadmium from spent batteries. For this purpose Cyphos IL 102 diluted in toluene was employed for the extraction and recovery of Zn and Cd from Zn-C and Ni-Cd batteries leach liquor. The influence of extractant concentration for the leach liquors of Zn-C (0.01-0.05mol/L) and Ni-Cd (0.04-0.20mol/L) batteries has been investigated. Composition of the leach liquor obtained from Zn-C/Ni-Cd spent batteries is Zn - 2.18g/L, Mn - 4.59g/L, Fe - 4.0×10 -3 g/L, Ni - 0.2×10 -3 g/L/Cd - 4.28g/L, Ni - 0.896×10 -1 g/L, Fe - 0.148g/L, Co - 3.77×10 -3 g/L, respectively. Two stage counter current extraction at A/O 1:1 and 3:2 with 0.04mol/L and 0.2mol/L Cyphos IL 102 for Zn and Cd, respectively provide more than 99.0% extraction of both the metal ions with almost negligible extraction of associated metal ions. A stripping efficiency of around 99.0% for Zn and Cd was obtained at O/A 1:1 using 1.0mol/L HNO 3 in two and three counter current stages, respectively. ZnO and CdO were also synthesized using the loaded organic phase and characterized using XRD, FE-SEM and EDX techniques. XRD peaks of ZnO and CdO correspond to zincite and monteponite, respectively. The average particle size was ∼27.0nm and ∼37.0nm for ZnO and CdO, respectively. The EDX analysis of ZnO and CdO shows almost 1:1 atomic percentage. Copyright © 2017. Published by Elsevier Ltd.

Transcriptional up-regulation of genes involved in photosynthesis of the Zn/Cd hyperaccumulator Sedum alfredii in response to zinc and cadmium.

PubMed

Tang, Lu; Yao, Aijun; Ming Yuan; Tang, Yetao; Liu, Jian; Liu, Xi; Qiu, Rongliang

2016-12-01

Zinc (Zn) and cadmium (Cd) are two closely related chemical elements with very different biological roles in photosynthesis. Zinc plays unique biochemical functions in photosynthesis. Previous studies suggested that in some Zn/Cd hyperaccumulators, many steps in photosynthesis may be Cd tolerant or even Cd stimulated. Using RNA-seq data, we found not only that Cd and Zn both up-regulated the CA1 gene, which encodes a β class carbonic anhydrase (CA) in chloroplasts, but that a large number of other Zn up-regulated genes in the photosynthetic pathway were also significantly up-regulated by Cd in leaves of the Zn/Cd hyperaccumulator Sedum alfredii. These genes also include chloroplast genes involved in transcription and translation (rps18 and rps14), electron transport and ATP synthesis (atpF and ccsA), Photosystem II (PSBI, PSBM, PSBK, PSBZ/YCF9, PSBO-1, PSBQ, LHCB1.1, LHCB1.4, LHCB2.1, LHCB4.3 and LHCB6) and Photosystem I (PSAE-1, PSAF, PSAH2, LHCA1 and LHCA4). Cadmium and Zn also up-regulated the VAR1 gene, which encodes the ATP-dependent zinc metalloprotease FTSH 5 (a member of the FtsH family), and the DAG gene, which influences chloroplast differentiation and plastid development, and the CP29 gene, which supports RNA processing in chloroplasts and has a potential role in signal-dependent co-regulation of chloroplast genes. Further morphological parameters (dry biomass, cross-sectional thickness, chloroplast size, chlorophyll content) and chlorophyll fluorescence parameters confirmed that leaf photosynthesis of S. alfredii responded to Cd much as it did to Zn, which will contribute to our understanding of the positive effects of Zn and Cd on growth of this plant. Copyright © 2016 Elsevier Ltd. All rights reserved.

Oxygen vacancies promoted interfacial charge carrier transfer of CdS/ZnO heterostructure for photocatalytic hydrogen generation.

PubMed

Xie, Ying Peng; Yang, Yongqiang; Wang, Guosheng; Liu, Gang

2017-10-01

The solid-state Z-scheme trinary/binary heterostructures show the advantage of utilizing the high-energy photogenerated charge carriers in photocatalysis. However, the key factors controlling such Z-scheme in the binary heterostructures are still unclear. In this paper, we showed that oxygen vacancies could act as an interface electron transfer mediator to promote the direct Z-scheme charge transfer process in binary semiconductor heterostructures of CdS/ZnS. Increasing the concentration of surface oxygen vacancies of ZnO crystal can greatly enhance photocatalytic hydrogen generation of CdS/ZnO heterostructure. This was attributed to the strengthened direct Z-scheme charge transfer process in CdS/ZnO, as evidenced by steady-state/time-resolved photoluminescence spectroscopy and selective photodeposition of metal particles on the heterostructure. Copyright © 2017 Elsevier Inc. All rights reserved.

Visible Light-Induced Degradation of Methylene Blue in the Presence of Photocatalytic ZnS and CdS Nanoparticles

PubMed Central

Soltani, Nayereh; Saion, Elias; Hussein, Mohd Zobir; Erfani, Maryam; Abedini, Alam; Bahmanrokh, Ghazaleh; Navasery, Manizheh; Vaziri, Parisa

2012-01-01

ZnS and CdS nanoparticles were prepared by a simple microwave irradiation method under mild conditions. The obtained nanoparticles were characterized by XRD, TEM and EDX. The results indicated that high purity of nanosized ZnS and CdS was successfully obtained with cubic and hexagonal crystalline structures, respectively. The band gap energies of ZnS and CdS nanoparticles were estimated using UV-visible absorption spectra to be about 4.22 and 2.64 eV, respectively. Photocatalytic degradation of methylene blue was carried out using physical mixtures of ZnS and CdS nanoparticles under a 500-W halogen lamp of visible light irradiation. The residual concentration of methylene blue solution was monitored using UV-visible absorption spectrometry. From the study of the variation in composition of ZnS:CdS, a composition of 1:4 (by weight) was found to be very efficient for degradation of methylene blue. In this case the degradation efficiency of the photocatalyst nanoparticles after 6 h irradiation time was about 73% with a reaction rate of 3.61 × 10−3 min−1. Higher degradation efficiency and reaction rate were achieved by increasing the amount of photocatalyst and initial pH of the solution. PMID:23202896

A ceramic microreactor for the synthesis of water soluble CdS and CdS/ZnS nanocrystals with on-line optical characterization.

PubMed

Gómez-de Pedro, Sara; Puyol, Mar; Izquierdo, David; Salinas, Iñigo; de la Fuente, J M; Alonso-Chamarro, Julián

2012-02-21

In this paper, a computer controlled microreactor to synthesize water soluble CdS and CdS/ZnS nanocrystals with in situ monitoring of the reaction progress is developed. It is based on ceramic tapes and the Low-Temperature Co-fired Ceramics technology (LTCC). As well the microsystem set-up, the microreactor fluidic design has also been thoroughly optimized. The final device is based on a hydrodynamic focusing of the reagents followed by a three-dimensional micromixer. This generates monodispersed and stable CdS and core-shell CdS/ZnS nanocrystals of 4.5 and 4.2 nm, respectively, with reproducible optical properties in terms of fluorescence emission wavelengths, bandwidth, and quantum yields, which is a key requirement for their future analytical applications. The synthetic process is also controlled in real time with the integration of an optical detection system for absorbance and fluorescence measurements based on commercial miniaturized optical components. This makes possible the efficient managing of the hydrodynamic variables to obtain the desired colloidal suspension. As a result, a simple, economic, robust and portable microsystem for the well controlled synthesis of CdS and CdS/ZnS nanocrystals is presented. Moreover, the reaction takes place in aqueous medium, thus allowing the direct modular integration of this microreactor in specific analytical microsystems, which require the use of such quantum dots as labels. This journal is © The Royal Society of Chemistry 2012

Blocking the Formation of Zn2+/Dye Complexes in Dye-Sensitized Solar Cells by Inserting CdS Quantum Dots into Sandwich Layer

NASA Astrophysics Data System (ADS)

Sun, Yunfei; Liu, Chunling; Yang, Lili; Wei, Maobin; Lv, Shiquan; Sui, Yingrui; Cao, Jian; Chen, Gang; Yang, Jinghai

2018-06-01

ZnO NRAs are grown on ITO substrates by a simple chemical method. CdS QDs were deposited on ZnO NRAs by SILAR. N719 was synthesized by dipping method. J-V analysis indicates that by inserting a layer of CdS QDs, the conversion efficiency of DSSCs was improved obviously. The device with CdS QDs shows the higher conversion efficiency due to the three reasons: (1) CdS QDs enhanced adsorption spectra of DSSCs in the visible region; (2) CdS QDs block the formation of Zn2+/dye complex, it is beneficial for electros transport from dye to ZnO photoanode. It is the key to obtain higher conversion efficiency; (3) FRET dynamics exists by the introduction of CdS QDs.

Thiolate-Capped CdSe/ZnS Core-Shell Quantum Dots for the Sensitive Detection of Glucose.

PubMed

Abd Rahman, Samsulida; Ariffin, Nurhayati; Yusof, Nor Azah; Abdullah, Jaafar; Mohammad, Faruq; Ahmad Zubir, Zuhana; Nik Abd Aziz, Nik Mohd Azmi

2017-07-01

A semiconducting water-soluble core-shell quantum dots (QDs) system capped with thiolated ligand was used in this study for the sensitive detection of glucose in aqueous samples. The QDs selected are of CdSe-coated ZnS and were prepared in house based on a hot injection technique. The formation of ZnS shell at the outer surface of CdSe core was made via a specific process namely, SILAR (successive ionic layer adsorption and reaction). The distribution, morphology, and optical characteristics of the prepared core-shell QDs were assessed by transmission electron microscopy (TEM) and spectrofluorescence, respectively. From the analysis, the results show that the mean particle size of prepared QDs is in the range of 10-12 nm and that the optimum emission condition was displayed at 620 nm. Further, the prepared CdSe/ZnS core shell QDs were modified by means of a room temperature ligand-exchange method that involves six organic ligands, L -cysteine, L -histidine, thio-glycolic acid (TGA or mercapto-acetic acid, MAA), mercapto-propionic acid (MPA), mercapto-succinic acid (MSA), and mercapto-undecanoic acid (MUA). This process was chosen in order to maintain a very dense water solubilizing environment around the QDs surface. From the analysis, the results show that the CdSe/ZnS capped with TGA (CdSe/ZnS-TGA) exhibited the strongest fluorescence emission as compared to others; hence, it was tested further for the glucose detection after their treatment with glucose oxidase (GOx) and horseradish peroxidase (HRP) enzymes. Here in this study, the glucose detection is based on the fluorescence quenching effect of the QDs, which is correlated to the oxidative reactions occurred between the conjugated enzymes and glucose. From the analysis of results, it can be inferred that the resultant GOx:HRP/CdSe/ZnS-TGA QDs system can be a suitable platform for the fluorescence-based determination of glucose in the real samples.

Optical and AFM study of electrostatically assembled films of CdS and ZnS colloid nanoparticles

NASA Astrophysics Data System (ADS)

Suryajaya; Nabok, A.; Davis, F.; Hassan, A.; Higson, S. P. J.; Evans-Freeman, J.

2008-05-01

CdS and ZnS semiconducting colloid nanoparticles coated with the organic shell, containing either SO 3- or NH 2+ groups, were prepared using the aqueous phase synthesis. The multilayer films of CdS (or ZnS) were deposited onto glass, quartz and silicon substrates using the technique of electrostatic self-assembly. The films produced were characterized with UV-vis spectroscopy, spectroscopic ellipsometry and atomic force microscopy. A substantial blue shift of the main absorption band with respect to the bulk materials was found for both CdS and ZnS films. The Efros equation in the effective mass approximation (EMA) theoretical model allowed the evaluation of the nanoparticle radius of 1.8 nm, which corresponds well to the ellipsometry results. AFM shows the formation of larger aggregates of nanoparticles on solid surfaces.

The Fate of Polyol-Made ZnO and CdS Nanoparticles in Seine River Water (Paris, France).

PubMed

da Rocha, Alice; Sivry, Yann; Gelabert, Alexandre; Beji, Zyed; Benedetti, Marc F; Menguy, Nicolas; Brayner, Roberta

2015-05-01

This study aims to characterize nanoparticles with different compositions and structures as well as seeing their evolutions over time in a natural environment such as Seine river water (Paris, France). Face centered cubic (fcc) and hexagonal (hcp) CdS as well as hexagonal (hcp) ZnO nanoparticles were synthesized by the Polyol method. CdS nanoparticles (i) cfc structure: are agglomerated, present 100 nm length with heterogeneous diameter and 10 m2 g(-1) specific surface area (S(g)) from Brunauer Emett and Teller (BET) measurements; (ii) hcp structure: 20 nm and S(g) = 67 m2 g(-1). ZnO hcp nanoparticles presents 50 nm length and 15 nm diameter and S(g) = 54 m2 g(-1). These results are in agreement with X-ray diffraction (XRD), and small angle X-ray scattering (SAXs). After 48 h interaction with Seine river water, cryo-TEM analysis showed that ZnO nanoparticles form spherical agglomerates with 300 nm diameter; CdS nanoparticles (fcc) are agglomerated presenting large diameters (> 500 nm); and CdS nanoparticles (hcp) are not agglomerated and present the same characteristics of the starting material. After 168h of contact with Seine river water, CdS (fcc) presents only 14% of dissolution, CdS (hcp) presents both 60% dissolution and 30% reprecipitation in a cadmium carbonate form and finally almost 90% of ZnO nanoparticles are dissolved.

High-K (Ba0.8Bi0.2)(Zn0.1Ti0.9)O3 ceramics for high-temperature capacitor applications.

PubMed

Raengthon, Natthaphon; Cann, David P

2011-09-01

Solid solutions of BaTiO(3)-Bi(Zn(1/2)Ti(1/2))O(3) were investigated for high-temperature capacitor applications. Compositions close to 0.8BaTiO(3)-0.2Bi(Zn(1/2)Ti(1/2))O(3) revealed pseudo-cubic symmetry and showed a linear dielectric response. The existence of a nearly flat temperature dependence of the relative permittivity over the temperature range of 100 to 350°C was also obtained. In this study, the effects of cation non-stoichiometry and doping were investigated in an attempt to optimize the insulation resistance for high-temperature applications. The dielectric response of (Ba(0.8)-xBi(0.2))(Zn(0.1)Ti(0.9)) O(3) ceramics where 0 ≤ X ≤ 0.08, as well as ZrO2- and Mn(2)O(3)-doped ceramics were studied. The optimum compositions exhibited a relative permittivity in excess of 1150 with a low loss tangent (tan δ < 0.05) that persisted up to a temperature of 460δC. The temperature dependence of resistivity also revealed the improved insulation resistance of Ba-deficient compositions. Additionally, we suggest that an ionic conduction mechanism is responsible for the degradation of resistivity at high temperatures. The temperature coefficient of permittivity ((τ)K) and the RC time constant were also investigated.

Ultrafast light matter interaction in CdSe/ZnS core-shell quantum dots

NASA Astrophysics Data System (ADS)

Yadav, Rajesh Kumar; Sharma, Rituraj; Mondal, Anirban; Adarsh, K. V.

2018-04-01

Core-shell quantum dot are imperative for carrier (electron and holes) confinement in core/shell, which provides a stage to explore the linear and nonlinear optical phenomena at the nanoscalelimit. Here we present a comprehensive study of ultrafast excitation dynamics and nonlinear optical absorption of CdSe/ZnS core shell quantum dot with the help of ultrafast spectroscopy. Pump-probe and time-resolved measurements revealed the drop of trapping at CdSe surface due to the presence of the ZnS shell, which makes more efficient photoluminescence. We have carried out femtosecond transient absorption studies of the CdSe/ZnS core-shell quantum dot by irradiation with 400 nm laser light, monitoring the transients in the visible region. The optical nonlinearity of the core-shell quantum dot studied by using the Z-scan technique with 120 fs pulses at the wavelengths of 800 nm. The value of two photon absorption coefficients (β) of core-shell QDs extracted as80cm/GW, and it shows excellent benchmark for the optical limiting onset of 2.5GW/cm2 with the low limiting differential transmittance of 0.10, that is an order of magnitude better than graphene based materials.

Enhanced removal of Zn(2+) or Cd(2+) by the flocculating Chlorella vulgaris JSC-7.

PubMed

Alam, Md Asraful; Wan, Chun; Zhao, Xin-Qing; Chen, Li-Jie; Chang, Jo-Shu; Bai, Feng-Wu

2015-05-30

Microalgae are attracting attention due to their potentials in mitigating CO2 emissions and removing environmental pollutants. However, harvesting microalgal biomass from diluted cultures is one of the bottlenecks for developing economically viable processes for this purpose. Microalgal cells can be harvested by cost-effective sedimentation when flocculating strains are used. In this study, the removal of Zn(2+) and Cd(2+) by the flocculating Chlorella vulgaris JSC-7 was studied. The experimental results indicated that more than 80% Zn(2+) and 60% Cd(2+) were removed by the microalgal culture within 3 days in the presence up to 20.0mg/L Zn(2+) and 4.0mg/L Cd(2+), respectively, which were much higher than that observed with the culture of the non-flocculating C. vulgaris CNW11. Furthermore, the mechanism underlying this phenomenon was explored by investigating the effect of Zn(2+) and Cd(2+) on the growth and metabolic activities of the microalgal strains. It was found that the flocculation of the microalga improved its growth, synthesis of photosynthetic pigments and antioxidation activity under the stressful conditions, indicating a better tolerance to the heavy metal ions for a potential in removing them more efficiently from contaminated wastewaters, together with a bioremediation of other nutritional components contributed to the eutrophication of aquatic ecosystems. Copyright © 2015 Elsevier B.V. All rights reserved.

Hysteretic Characteristics of Pulsed Laser Deposited 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3/ZnO Bilayers.

PubMed

Silva, J P B; Wang, J; Koster, G; Rijnders, G; Negrea, R F; Ghica, C; Sekhar, K C; Moreira, J Agostinho; Gomes, M J M

2018-05-02

In the present work, we study the hysteretic behavior in the electric-field-dependent capacitance and the current characteristics of 0.5Ba(Zr 0.2 Ti 0.8 )O 3 -0.5(Ba 0.7 Ca 0.3 )TiO 3 (BCZT)/ZnO bilayers deposited on 0.7 wt % Nb-doped (001)-SrTiO 3 (Nb:STO) substrates in a metal-ferroelectric-semiconductor (MFS) configuration. The X-ray diffraction measurements show that the BCZT and ZnO layers are highly oriented along the c-axis and have a single perovskite and wurtzite phases, respectively, whereas high-resolution transmission electron microscopy revealed very sharp Nb:STO/BCZT/ZnO interfaces. The capacitance-electric field ( C- E) characteristics of the bilayers exhibit a memory window of 47 kV/cm and a capacitance decrease of 22%, at a negative bias. The later result is explained by the formation of a depletion region in the ZnO layer. Moreover, an unusual resistive switching (RS) behavior is observed in the BCZT films, where the RS ratio can be 500 times enhanced in the BCZT/ZnO bilayers. The RS enhancement can be understood by the barrier potential profile modulation at the depletion region, in the BCZT/ZnO junction, via ferroelectric polarization switching of the BCZT layer. This work builds a bridge between the hysteretic behavior observed either in the C- E and current-electric field characteristics on a MFS structure.

Magnetic field insensitive photoluminescence decay of ZnSe/CdS core/shell type-II colloidal quantum dots

NASA Astrophysics Data System (ADS)

Lee, Woojin; Park, Seongho; Murayama, Akihiro; Lee, Jong-soo; Kyhm, Kwangseuk

2018-06-01

We have synthesized ZnSe/CdS core/shell type-II colloidal quantum dots, where an electron and a hole are separated in the CdS shell and the ZnSe core, respectively. Our theoretical model has revealed that absorbance spectrum of bare ZnSe quantum dots in 2 nm radius becomes broadened with a large redshift (∼1.15 eV) when the electron in ZnSe core is separated by 3.2 nm CdS shell. Also, we found that our type-II QDs are insensitive to an external magnetic field up to 5 T in terms of central emission energy, degree of polarization, and photoluminescence decay time. This can be attributed to the electron–hole charge separation in a type-II structure, whereby the suppressed exchange interaction gives rise to a magnetic insensitivity with a small energy difference between the bright and dark exciton states.

Syntheses, structures and photoelectric properties of a series of Cd(II)/Zn(II) coordination polymers and coordination supramolecules

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

Jin Jing; Han Xiao; Meng Qin

2013-01-15

Five Cd(II)/Zn(II) complexes [Cd(1,2-bdc)(pz){sub 2}(H{sub 2}O)]{sub n} (1), [Cd1Cd2(btec)(H{sub 2}O){sub 6}]{sub n} (2), [Cd(3,4-pdc) (H{sub 2}O)]{sub n} (3), [Zn(2,5-pdc)(H{sub 2}O){sub 4}]{center_dot}2H{sub 2}O (4) and {l_brace} [Zn(2,5-pdc)(H{sub 2}O){sub 2}]{center_dot}H{sub 2}O{r_brace} {sub n} (5) (H{sub 2}bdc=1,2-benzenedicarboxylic acid, pz=pyrazole, H{sub 4}btec=1,2,4,5-benzenetetracarboxylic acid, H{sub 2}pdc=pyridine-dicarboxylic acid) were hydrothermally synthesized and characterized by single-crystal X-ray diffraction, surface photovoltage spectroscopy, XRD, TG analysis, IR and UV-vis spectra and elemental analysis. Structural analyses show that complexes 1-3 are 1D, 2D and 3D Cd(II) coordination polymers, respectively. Complex 4 is a mononuclear Zn(II) complex. Complex 5 is a 3D Zn(II) coordination polymer. The surface photoelectric properties of complexesmore » were investigated by SPS. The results indicate that all complexes exhibit photoelectric responses in the range of 300-600 nm, which reveals that they all possess certain photoelectric conversion properties. By the comparative analyses, it can be found that the species and coordination micro-environment of central metal ion, the species and property of ligands affect the intensity and scope of photoelectric response. - Graphical abstract: Five Cd(II)/Zn(II) complexes have been hydrothermally synthesized and characterized. The photoelectric properties were studied with SPS. The species and coordination micro-environment of central metal ion, the species and property of ligands all affect the photoelectric responses. Highlights: Black-Right-Pointing-Pointer Five Cd/Zn complexes have been synthesized and characterized. Black-Right-Pointing-Pointer The SPS results indicate they possess obvious photoelectric conversion property. Black-Right-Pointing-Pointer The species and coordination environment of central metal ion affect SPS. Black-Right-Pointing-Pointer The species and property of ligands

Impact of Antibody Bioconjugation on Emission and Energy Band Profile of CdSeTe/ZnS Quantum Dots

NASA Astrophysics Data System (ADS)

Torchynska, T. V.; Gomez, J. A. Jaramillo; Polupan, G.; Macotela, L. G. Vega

2018-03-01

The variation of the photoluminescence (PL) and Raman scattering spectra of CdSeTe/ZnS quantum dots (QDs) on conjugation to an antibody has been investigated. Two types of CdSeTe/ZnS QD with different emission wavelength (705 nm and 800 nm) were studied comparatively before and after conjugation to anti-pseudorabies virus antibody (AB). Nonconjugated QDs were characterized by Gaussian-type PL bands. PL shifts to higher energy and asymmetric shape of PL bands was detected in PL spectra of bioconjugated QDs. The surface-enhanced Raman scattering effect was exhibited by the bioconjugated CdSeTe/ZnS QDs, indicating that the excitation light used in the Raman study generated electric dipoles in the AB molecules. The optical bandgap of the CdSeTe core was calculated numerically as a function of its radius based on an effective mass approximation model. The energy band diagrams for non- and bioconjugated CdSeTe/ZnS QDs were obtained, revealing a type II quantum well in the CdSeTe core. The calculations show that AB dipoles, excited in the bioconjugated QDs, stimulate a change in the energy band diagram of the QDs that alters the PL spectrum. These results could be useful for improving the sensitivity of QD biosensors.

Coexistence of strongly and weakly confined energy levels in (Cd,Zn)Se quantum dots: Tailoring the near-band-edge and defect-levels for white light emission

NASA Astrophysics Data System (ADS)

Das, Tapan Kumar; Ilaiyaraja, P.; Sudakar, C.

2017-05-01

We demonstrate white light emission (WLE) from (Cd,Zn)Se system, which is a composite of Zn alloyed CdSe quantum dot and ZnSe-amorphous (ZnSe-a) phase. Detailed structural and photoluminescence emission studies on pure CdSe and (Cd,Zn)Se show cubic zinc blende structure in the size range of 2.5 to 5 nm. (Cd,Zn)Se quantum dots (QDs) also have a significant fraction of ZnSe-a phase. The near-band-edge green-emission in crystalline CdSe and (Cd,Zn)Se is tunable between 500 to 600 nm. The (Cd,Zn)Se system also exhibits a broad, deep defect level (DL) red-emission in the range 600 to 750 nm and a sharp ZnSe near-band-edge blue-emission (ZS-NBE) between 445 to 465 nm. While DL and CdSe near-band-edge (CS-NBE) emissions significantly shift with the size of QD due to strong confinement effect, the ZS-NBE show minimal change in peak position indicating a weak confinement effect. The intensities of ZS-NBE and DL emissions also exhibit a strong dependence on the QD size. A gamut of emission colors is obtained by combining the CS-NBE with the ZS-NBE emission and broad DL emission in (Cd,Zn)Se system. Interestingly, we find the convergence of Commission Internationale de l'Eclairage (CIE) coordinates towards the white light with increasing Zn concentration in CdSe. We demonstrate by combining these three emissions in a proper weight ratio WLE can be achieved. Cd1-yZnySe (y = 0. 5; QD size ˜4.9 nm) alloy with a maximum quantum yield of 57% exhibits CIE coordinates of (0.39, 0.4), color rendering index (CRI) of 82, correlated color temperature (CCT) of 3922 K, and Duv of 0.0078 which is very promising for white light applications.

How does contamination of rice soils with Cd and Zn cause high incidence of human Cd disease in subsistence rice farmers?

USDA-ARS?s Scientific Manuscript database

Rice (Oryza sativa L.) grown on Zn mine waste contaminated soils has caused unequivocal Cd effects on kidney and occasional bone disease (itai-itai) in subsistence rice farmers, but high intake of Cd from other foods has not caused similar effects. Research has clarified two important topics about ...

Effect of Cu(II), Cd(II) and Zn(II) on Pb(II) biosorption by algae Gelidium-derived materials.

PubMed

Vilar, Vítor J P; Botelho, Cidália M S; Boaventura, Rui A R

2008-06-15

Biosorption of Pb(II), Cu(II), Cd(II) and Zn(II) from binary metal solutions onto the algae Gelidium sesquipedale, an algal industrial waste and a waste-based composite material was investigated at pH 5.3, in a batch system. Binary Pb(II)/Cu(II), Pb(II)/Cd(II) and Pb(II)/Zn(II) solutions have been tested. For the same equilibrium concentrations of both metal ions (1 mmol l(-1)), approximately 66, 85 and 86% of the total uptake capacity of the biosorbents is taken by lead ions in the systems Pb(II)/Cu(II), Pb(II)/Cd(II) and Pb(II)/Zn(II), respectively. Two-metal results were fitted to a discrete and a continuous model, showing the inhibition of the primary metal biosorption by the co-cation. The model parameters suggest that Cd(II) and Zn(II) have the same decreasing effect on the Pb(II) uptake capacity. The uptake of Pb(II) was highly sensitive to the presence of Cu(II). From the discrete model it was possible to obtain the Langmuir affinity constant for Pb(II) biosorption. The presence of the co-cations decreases the apparent affinity of Pb(II). The experimental results were successfully fitted by the continuous model, at different pH values, for each biosorbent. The following sequence for the equilibrium affinity constants was found: Pb>Cu>Cd approximately Zn.

Cultivar and Metal-Specific Effects of Endophytic Bacteria in Helianthus tuberosus Exposed to Cd and Zn

PubMed Central

Thijs, Sofie; Lobo, Mª Carmen; Weyens, Nele; Pérez-Sanz, Araceli

2017-01-01

Plant growth promoting endophytic bacteria (PGPB) isolated from Brassica napus were inoculated in two cultivars of Helianthus tuberosus (VR and D19) growing on sand supplemented with 0.1 mM Cd or 1 mM Zn. Plant growth, concentrations of metals and thiobarbituric acid (TBA) reactive compounds were determined. Colonization of roots of H. tuberosus D19 by Pseudomonas sp. 262 was evaluated using confocal laser scanning microscopy. Pseudomonas sp. 228, Serratia sp. 246 and Pseudomonas sp. 262 significantly enhanced growth of H. tuberosus D19 exposed to Cd or Zn. Pseudomonas sp. 228 significantly increased Cd concentrations in roots. Serratia sp. 246, and Pseudomonas sp. 256 and 228 resulted in significantly decreased contents of TBA reactive compounds in roots of Zn exposed D19 plants. Growth improvement and decrease of metal-induced stress were more pronounced in D19 than in VR. Pseudomonas sp. 262-green fluorescent protein (GFP) colonized the root epidermis/exodermis and also inside root hairs, indicating that an endophytic interaction was established. H. tuberosus D19 inoculated with Pseudomonas sp. 228, Serratia sp. 246 and Pseudomonas sp. 262 holds promise for sustainable biomass production in combination with phytoremediation on Cd and Zn contaminated soils. PMID:28934107

Cultivar and Metal-Specific Effects of Endophytic Bacteria in Helianthus tuberosus Exposed to Cd and Zn.

PubMed

Montalbán, Blanca; Thijs, Sofie; Lobo, Mª Carmen; Weyens, Nele; Ameloot, Marcel; Vangronsveld, Jaco; Pérez-Sanz, Araceli

2017-09-21

Plant growth promoting endophytic bacteria (PGPB) isolated from Brassica napus were inoculated in two cultivars of Helianthus tuberosus (VR and D19) growing on sand supplemented with 0.1 mM Cd or 1 mM Zn. Plant growth, concentrations of metals and thiobarbituric acid (TBA) reactive compounds were determined. Colonization of roots of H. tuberosus D19 by Pseudomonas sp. 262 was evaluated using confocal laser scanning microscopy. Pseudomonas sp. 228, Serratia sp. 246 and Pseudomonas sp. 262 significantly enhanced growth of H. tuberosus D19 exposed to Cd or Zn. Pseudomonas sp. 228 significantly increased Cd concentrations in roots. Serratia sp. 246, and Pseudomonas sp. 256 and 228 resulted in significantly decreased contents of TBA reactive compounds in roots of Zn exposed D19 plants. Growth improvement and decrease of metal-induced stress were more pronounced in D19 than in VR. Pseudomonas sp. 262 - green fluorescent protein (GFP) colonized the root epidermis/exodermis and also inside root hairs, indicating that an endophytic interaction was established. H. tuberosus D19 inoculated with Pseudomonas sp. 228, Serratia sp. 246 and Pseudomonas sp. 262 holds promise for sustainable biomass production in combination with phytoremediation on Cd and Zn contaminated soils.

Transparent conducting ZnO-CdO mixed oxide thin films grown by the sol-gel method.

PubMed

Pathak, Trilok K; Rajput, Jeevitesh K; Kumar, Vinod; Purohit, L P; Swart, H C; Kroon, R E

2017-02-01

Mixed oxides of zinc and cadmium with different proportions were deposited on ordinary glass substrates using the sol-gel spin coating method under optimized deposition conditions using zinc acetate dihydrate and cadmium acetate dihydrate as precursors. X-ray diffraction patterns confirmed the polycrystalline nature of the films. A combination of cubic CdO and hexagonal wurtzite ZnO phases was observed. The oxidation states of Zn, Cd and O in the deposited films were determined by X-ray photoelectron spectroscopic studies. Surface morphology was studied by scanning electron microscopy and atomic force microscopy. The compositional analysis of the thin films was studied by secondary ion mass spectroscopy. The transmittance of the thin films was measured in the range 300-800nm and the optical bandgap was calculated using Tauc's plot method. The bandgap decreased from 3.15eV to 2.15eV with increasing CdO content. The light emission properties of the ZnO:CdO thin films were studied by photoluminescence spectra recorded at room temperature. The current-voltage characteristics were also assessed and showed ohmic behaviour. The resistance decreased with increasing CdO content. Copyright © 2016 Elsevier Inc. All rights reserved.

Energy dispersive CdTe and CdZnTe detectors for spectral clinical CT and NDT applications

NASA Astrophysics Data System (ADS)

Barber, W. C.; Wessel, J. C.; Nygard, E.; Iwanczyk, J. S.

2015-06-01

We are developing room temperature compound semiconductor detectors for applications in energy-resolved high-flux single x-ray photon-counting spectral computed tomography (CT), including functional imaging with nanoparticle contrast agents for medical applications and non-destructive testing (NDT) for security applications. Energy-resolved photon-counting can provide reduced patient dose through optimal energy weighting for a particular imaging task in CT, functional contrast enhancement through spectroscopic imaging of metal nanoparticles in CT, and compositional analysis through multiple basis function material decomposition in CT and NDT. These applications produce high input count rates from an x-ray generator delivered to the detector. Therefore, in order to achieve energy-resolved single photon counting in these applications, a high output count rate (OCR) for an energy-dispersive detector must be achieved at the required spatial resolution and across the required dynamic range for the application. The required performance in terms of the OCR, spatial resolution, and dynamic range must be obtained with sufficient field of view (FOV) for the application thus requiring the tiling of pixel arrays and scanning techniques. Room temperature cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) compound semiconductors, operating as direct conversion x-ray sensors, can provide the required speed when connected to application specific integrated circuits (ASICs) operating at fast peaking times with multiple fixed thresholds per pixel provided the sensors are designed for rapid signal formation across the x-ray energy ranges of the application at the required energy and spatial resolutions, and at a sufficiently high detective quantum efficiency (DQE). We have developed high-flux energy-resolved photon-counting x-ray imaging array sensors using pixellated CdTe and CdZnTe semiconductors optimized for clinical CT and security NDT. We have also fabricated high

Energy dispersive CdTe and CdZnTe detectors for spectral clinical CT and NDT applications

PubMed Central

Barber, W. C.; Wessel, J. C.; Nygard, E.; Iwanczyk, J. S.

2014-01-01

We are developing room temperature compound semiconductor detectors for applications in energy-resolved high-flux single x-ray photon-counting spectral computed tomography (CT), including functional imaging with nanoparticle contrast agents for medical applications and non destructive testing (NDT) for security applications. Energy-resolved photon-counting can provide reduced patient dose through optimal energy weighting for a particular imaging task in CT, functional contrast enhancement through spectroscopic imaging of metal nanoparticles in CT, and compositional analysis through multiple basis function material decomposition in CT and NDT. These applications produce high input count rates from an x-ray generator delivered to the detector. Therefore, in order to achieve energy-resolved single photon counting in these applications, a high output count rate (OCR) for an energy-dispersive detector must be achieved at the required spatial resolution and across the required dynamic range for the application. The required performance in terms of the OCR, spatial resolution, and dynamic range must be obtained with sufficient field of view (FOV) for the application thus requiring the tiling of pixel arrays and scanning techniques. Room temperature cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) compound semiconductors, operating as direct conversion x-ray sensors, can provide the required speed when connected to application specific integrated circuits (ASICs) operating at fast peaking times with multiple fixed thresholds per pixel provided the sensors are designed for rapid signal formation across the x-ray energy ranges of the application at the required energy and spatial resolutions, and at a sufficiently high detective quantum efficiency (DQE). We have developed high-flux energy-resolved photon-counting x-ray imaging array sensors using pixellated CdTe and CdZnTe semiconductors optimized for clinical CT and security NDT. We have also fabricated high

Energy dispersive CdTe and CdZnTe detectors for spectral clinical CT and NDT applications.

PubMed

Barber, W C; Wessel, J C; Nygard, E; Iwanczyk, J S

2015-06-01

We are developing room temperature compound semiconductor detectors for applications in energy-resolved high-flux single x-ray photon-counting spectral computed tomography (CT), including functional imaging with nanoparticle contrast agents for medical applications and non destructive testing (NDT) for security applications. Energy-resolved photon-counting can provide reduced patient dose through optimal energy weighting for a particular imaging task in CT, functional contrast enhancement through spectroscopic imaging of metal nanoparticles in CT, and compositional analysis through multiple basis function material decomposition in CT and NDT. These applications produce high input count rates from an x-ray generator delivered to the detector. Therefore, in order to achieve energy-resolved single photon counting in these applications, a high output count rate (OCR) for an energy-dispersive detector must be achieved at the required spatial resolution and across the required dynamic range for the application. The required performance in terms of the OCR, spatial resolution, and dynamic range must be obtained with sufficient field of view (FOV) for the application thus requiring the tiling of pixel arrays and scanning techniques. Room temperature cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) compound semiconductors, operating as direct conversion x-ray sensors, can provide the required speed when connected to application specific integrated circuits (ASICs) operating at fast peaking times with multiple fixed thresholds per pixel provided the sensors are designed for rapid signal formation across the x-ray energy ranges of the application at the required energy and spatial resolutions, and at a sufficiently high detective quantum efficiency (DQE). We have developed high-flux energy-resolved photon-counting x-ray imaging array sensors using pixellated CdTe and CdZnTe semiconductors optimized for clinical CT and security NDT. We have also fabricated high

First-Principles Study of the Structural, Optical, Dynamical and Thermodynamic Properties of BaZnO2 Under Pressure

NASA Astrophysics Data System (ADS)

Wang, Yi-Xian; Hu, Cui-E.; Chen, Yang-Mei; Cheng, Yan; Ji, Guang-Fu

2016-11-01

The structural, optical, dynamical, and thermodynamic properties of BaZnO2 under pressure are studied based on the density functional theory. The calculated structural parameters are consistent with the available experimental data. In the ground state, the electronic band structure and density of states indicate that BaZnO2 is an insulator with a direct gap of 2.2 eV. The Mulliken charges are also analyzed to characterize the bonding property. After the structural relaxation, the optical properties are studied. It is found that the dielectric function of E Vert x and EVert y are isotropic, whereas the EVert x and EVert z are anisotropic. The effect of pressure on the energy-loss function in the ultraviolet region becomes more obvious as the pressure increases. Furthermore, the dynamical properties under different pressures are investigated using the finite displacement method. We find that the P3121 phase of BaZnO2 is dynamically stable under the pressure ranging from 0 GPa to 30 GPa. The phonon dispersion curves, phonon density of states, vibrational modes and atoms that contribute to these vibrations at {{\\varvec{Γ }}} point under different pressures are also reported in this work. Finally, by employing the quasi-harmonic approximation, the thermodynamic properties such as the temperature dependence of the thermal expansion coefficient, specific heat, entropy and Gibbs free energy under different pressures are investigated. It is found that the influences of the temperature on the heat capacity are much more significant than that of the pressure on it.

Zn(x)Cd(1-x)Se nanomultipods with tunable band gaps: synthesis and first-principles calculations.

PubMed

Wei, Hao; Su, Yanjie; Han, Ziyi; Li, Tongtong; Ren, Xinglong; Yang, Zhi; Wei, Liangming; Cong, Fengsong; Zhang, Yafei

2013-06-14

In this paper, we demonstrate that ZnxCd1-xSe nanomultipods can be synthesized via a facile and nontoxic solution-based method. Interesting aspects of composition, morphology and optical properties were deeply explored. The value of Zn/(Zn+Cd) could be altered across the entire range from 0.08 to 0.86 by varying the ratio of cation precursor contents. The band gap energy could be linearly tuned from 1.88 to 2.48 eV with respect to the value of Zn/(Zn+Cd). The experiment also showed that oleylamine played a dominant role in the formation of multipod structure. A possible growth mechanism was further suggested. First-principles calculations of band gap energy and density of states in the Vienna ab initio simulation package code were performed to verify the experimental variation tendency of the band gap. Computational results indicated that dissimilarities of electronic band structures and orbital constitutions determined the tunable band gap of the as-synthesized nanomultipod, which might be promising for versatile applications in relevant areas of solar cells, biomedicine, sensors, catalysts and so on.

Prediction of Ba, Mn and Zn for tropical soils using iron oxides and magnetic susceptibility

NASA Astrophysics Data System (ADS)

Marques Júnior, José; Arantes Camargo, Livia; Reynaldo Ferracciú Alleoni, Luís; Tadeu Pereira, Gener; De Bortoli Teixeira, Daniel; Santos Rabelo de Souza Bahia, Angelica

2017-04-01

Agricultural activity is an important source of potentially toxic elements (PTEs) in soil worldwide but particularly in heavily farmed areas. Spatial distribution characterization of PTE contents in farming areas is crucial to assess further environmental impacts caused by soil contamination. Designing prediction models become quite useful to characterize the spatial variability of continuous variables, as it allows prediction of soil attributes that might be difficult to attain in a large number of samples through conventional methods. This study aimed to evaluate, in three geomorphic surfaces of Oxisols, the capacity for predicting PTEs (Ba, Mn, Zn) and their spatial variability using iron oxides and magnetic susceptibility (MS). Soil samples were collected from three geomorphic surfaces and analyzed for chemical, physical, mineralogical properties, as well as magnetic susceptibility (MS). PTE prediction models were calibrated by multiple linear regression (MLR). MLR calibration accuracy was evaluated using the coefficient of determination (R2). PTE spatial distribution maps were built using the values calculated by the calibrated models that reached the best accuracy by means of geostatistics. The high correlations between the attributes clay, MS, hematite (Hm), iron oxides extracted by sodium dithionite-citrate-bicarbonate (Fed), and iron oxides extracted using acid ammonium oxalate (Feo) with the elements Ba, Mn, and Zn enabled them to be selected as predictors for PTEs. Stepwise multiple linear regression showed that MS and Fed were the best PTE predictors individually, as they promoted no significant increase in R2 when two or more attributes were considered together. The MS-calibrated models for Ba, Mn, and Zn prediction exhibited R2 values of 0.88, 0.66, and 0.55, respectively. These are promising results since MS is a fast, cheap, and non-destructive tool, allowing the prediction of a large number of samples, which in turn enables detailed mapping of

Synthesis and effect of Sr substitution on fluorescence of new Ba 2-xSr xZnS 3: Eu 2+ red phosphor: Considerable enhancement of emission intensity

NASA Astrophysics Data System (ADS)

Lee, Chi-Woo; Petrykin, Valery; Kakihana, Masato

2009-01-01

A series of 0.5 mol% Eu 2+-activated Ba 2-xSr xZnS 3 phosphor materials were synthesized using precursors prepared by the polymerizable complex method and their fluorescent properties were studied for the first time. It was found that Sr substitution for Ba leads to the considerable improvement of internal quantum efficiency and emission intensity in these materials compared to Ba 2ZnS 3, while emission peak wavelength exhibits a blue shift from 680 to 660 nm. Rietveld refinement of crystal structure of sample with x=0.7 suggests that Sr ions preferentially occupy one of two Ba sites in this compound. Such a structural re-arrangement might be responsible for the observed quantum efficiency dependence on Sr concentration.

Sol-gel synthesis of Cu-doped p-CdS nanoparticles and their analysis as p-CdS/n-ZnO thin film photodiode

NASA Astrophysics Data System (ADS)

Arya, Sandeep; Sharma, Asha; Singh, Bikram; Riyas, Mohammad; Bandhoria, Pankaj; Aatif, Mohammad; Gupta, Vinay

2018-05-01

Copper (Cu) doped p-CdS nanoparticles have been synthesized via sol-gel method. The as-synthesized nanoparticles were successfully characterized and implemented for fabrication of Glass/ITO/n-ZnO/p-CdS/Al thin film photodiode. The fabricated device is tested for small (-1 V to +1 V) bias voltage. Results verified that the junction leakage current within the dark is very small. During reverse bias condition, the maximum amount of photocurrent is obtained under illumination of 100 μW/cm2. Electrical characterizations confirmed that the external quantum efficiency (EQE), gain and responsivity of n-ZnO/p-CdS photodiode show improved photo response than conventional p-type materials for such a small bias voltage. It is therefore revealed that the Cu-doped CdS nanoparticles is an efficient p-type material for fabrication of thin film photo-devices.

Progress in the Development of CdZnTe Unipolar Detectors for Different Anode Geometries and Data Corrections

PubMed Central

Zhang, Qiushi; Zhang, Congzhe; Lu, Yanye; Yang, Kun; Ren, Qiushi

2013-01-01

CdZnTe detectors have been under development for the past two decades, providing good stopping power for gamma rays, lightweight camera heads and improved energy resolution. However, the performance of this type of detector is limited primarily by incomplete charge collection problems resulting from charge carriers trapping. This paper is a review of the progress in the development of CdZnTe unipolar detectors with some data correction techniques for improving performance of the detectors. We will first briefly review the relevant theories. Thereafter, two aspects of the techniques for overcoming the hole trapping issue are summarized, including irradiation direction configuration and pulse shape correction methods. CdZnTe detectors of different geometries are discussed in detail, covering the principal of the electrode geometry design, the design and performance characteristics, some detector prototypes development and special correction techniques to improve the energy resolution. Finally, the state of art development of 3-D position sensing and Compton imaging technique are also discussed. Spectroscopic performance of CdZnTe semiconductor detector will be greatly improved even to approach the statistical limit on energy resolution with the combination of some of these techniques. PMID:23429509

Dielectric properties of Ba0.6Sr0.4TiO3-La(B0.5Ti0.5)O3 (B=Mg, Zn) ceramics.

PubMed

Xu, Yebin; Liu, Ting; He, Yanyan; Yuan, Xiao

2009-11-01

Ba(0.6)Sr(0.4)TiO(3)-La(B(0.5)Ti(0.5))O(3) (B = Mg, Zn) ceramics were prepared by a solid-state reaction method, and their microwave dielectric characteristics and tunability were investigated. The ferroelectric-dielectric solid solutions with cubic perovskite structures were obtained for compositions of 10 to 60 mol% La(Mg(0.5)Ti(0.5))O(3) and 10 to 50 mol% La(Zn(0.5)Ti(0.5))O(3). With the increase of linear oxide dielectric content, the dielectric constant and tunability were decreased and Qf was increased. Ba(0.6)Sr(0.4)TiO(3)-La(Mg(0.5)Ti(0.5))O(3) has better dielectric properties than Ba(0.6)Sr(0.4)TiO(3)-La(Zn(0.5)Ti(0.5))O(3). 0.9Ba(0.6)Sr(0.4)TiO(3)-0.1La(Mg(0.5)Ti(0.5))O(3) has a dielectric constant epsilon = 338.2, Qf = 979 GHz and a tunability of was 3.7% at 100 kHz under 1.67 kV/mm. The Qf value of 0.5Ba(0.6)Sr(0.4)TiO(3)- 0.5La(Mg(0.5)Ti(0.5))O(3) reached 9367 GHz, but the tunable properties were lost.

Tunable luminescent emission characterization of type-I and type-II systems in CdS-ZnSe core-shell nanoparticles: Raman and photoluminescence study.

PubMed

Ca, Nguyen Xuan; Lien, V T K; Nghia, N X; Chi, T T K; Phan, The-Long

2015-11-06

We used wet chemical methods to synthesize core-shell nanocrystalline samples CdS(d)/ZnSe N , where d = 3-6 nm and N = 1-5 are the size of CdS cores and the number of monolayers grown on the cores, respectively. By annealing typical CdS(d)/ZnSe N samples (with d = 3 and 6 nm and N = 2) at 300 °C for various times t an = 10-600 min, we created an intermediate layer composed of Zn1-x Cd x Se and Cd1-x Zn x S alloys with various thicknesses. The formation of core-shell structures and intermediate layers was monitored by Raman scattering and UV-vis absorption spectrometers. Careful photoluminescence studies revealed that the as-prepared CdS(d)/ZnSe N samples with d = 5 nm and N = 2-4, and the annealed samples CdS(3 nm)/ZnSe2 with t an ≤ 60 min and CdS(6 nm)/ZnSe2 with t an ≤ 180 min, show the emission characteristics of type-II systems. Meanwhile, the other samples show the emission characteristics of type-I systems. These results prove that the partial separation of photoexcited carriers between the core and shell is dependent strongly on the engineered core-shell nanostructures, meaning the sizes of the core, shell, and intermediate layers. With the tunable luminescence properties, CdS-ZnSe-based core-shell materials are considered as promising candidates for multiple-exciton generation and single-photon sources.

A facile synthesis of Zn(x)Cd(1-x)S/CNTs nanocomposite photocatalyst for H2 production.

PubMed

Wang, Lei; Yao, Zhongping; Jia, Fangzhou; Chen, Bin; Jiang, Zhaohua

2013-07-21

The sulfide solid solution has become a promising and important visible-light-responsive photocatalyst for hydrogen production nowadays. Zn(x)Cd(1-x)S/CNT nanocomposites were synthesized to improve the dispersion, adjust the energy band gap, and enhance the separation of the photogenerated electrons and holes. The as-prepared photocatalysts were characterized by scanning electron-microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-visible diffuse reflectance spectra (UV-visible), respectively. And the effects of CNTs on structure, composition and optical absorption property of the sulfide solid solutions were investigated along with their inherent relationships. For Zn0.83Cd0.17S/CNTs, sulfide solid solution is assembled along the CNTs orderly, with a diameter of 100 nm or so. XPS analysis shows that there is bonding effect between the solid solutions and the CNTs due to the strong adsorption of Zn(2+) and Cd(2+) on the surface of CNTs. There are two obvious absorption edges for Zn0.83Cd0.17S/CNTs, corresponding to two kinds of sulfide solid solutions with different molar ratios of Zn/Cd. The hybridization of solid solutions with CNTs makes the absorption spectrum red shift. The photocatalytic property was evaluated by splitting Na2S + Na2SO3 solution into H2, and the highest rate of H2 evolution of 6.03 mmol h(-1) g(-1) was achieved over Zn0.83Cd0.17S/CNTs. The high activity of photocatalytic H2 production is attributed to the following factors: (1) the optimum band gap and a moderate position of the conduction band (which needs to match the irradiation spectrum of the Xe lamp best), (2) the efficient separation of photogenerated electrons and holes by hybridization, and (3) the improvement of the dispersion of nanocomposites by assembling along the CNTs as well.

Down-top nanofabrication of binary (CdO)x (ZnO)1-x nanoparticles and their antibacterial activity.

PubMed

Al-Hada, Naif Mohammed; Mohamed Kamari, Halimah; Abdullah, Che Azurahanim Che; Saion, Elias; Shaari, Abdul H; Talib, Zainal Abidin; Matori, Khamirul Amin

2017-01-01

In the present study, binary oxide (cadmium oxide [CdO]) x (zinc oxide [ZnO]) 1-x nanoparticles (NPs) at different concentrations of precursor in calcination temperature were prepared using thermal treatment technique. Cadmium and zinc nitrates (source of cadmium and zinc) with polyvinylpyrrolidone (capping agent) have been used to prepare (CdO) x (ZnO) 1-x NPs samples. The sample was characterized by X-ray diffraction (XRD), scanning electron microscopy, energy-dispersive X-ray (EDX), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy. XRD patterns analysis revealed that NPs were formed after calcination, which showed a cubic and hexagonal crystalline structure of (CdO) x (ZnO) 1-x NPs. The phase analysis using EDX spectroscopy and FTIR spectroscopy confirmed the presence of Cd and Zn as the original compounds of prepared (CdO) x (ZnO) 1-x NP samples. The average particle size of the samples increased from 14 to 33 nm as the concentration of precursor increased from x=0.20 to x=0.80, as observed by TEM results. The surface composition and valance state of the prepared product NPs were determined by X-ray photoelectron spectroscopy (XPS) analyses. Diffuse UV-visible reflectance spectra were used to determine the optical band gap through the Kubelka-Munk equation; the energy band gap was found to decrease for CdO from 2.92 to 2.82 eV and for ZnO from 3.22 to 3.11 eV with increasing x value. Additionally, photoluminescence (PL) spectra revealed that the intensity in PL increased with an increase in particle size. In addition, the antibacterial activity of binary oxide NP was carried out in vitro against Escherichia coli ATCC 25922 Gram (-ve), Salmonella choleraesuis ATCC 10708, and Bacillus subtilis UPMC 1175 Gram (+ve). This study indicated that the zone of inhibition of 21 mm has good antibacterial activity toward the Gram-positive B. subtilis UPMC 1175.

Effects of added Zn, Ni and Cd on desert shrubs grown in desert soil

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

Patel, P.M.; Wallace, A.; Romney, E.M.

1980-01-01

Desert shrubs - Ambrosia dumosa, Lycium andersonii, Larrea tridenata, and Ephedra nevadensis wre grown in a glasshouse in desert (calcarous) soil with different levels of added Zn, Ni, and Cd. The objective was to study effects of the metals on growth and yield and uptake and translocation of metals in desert plant species which are common in the Mojave Desert (areas of Nevada and southeast California). Zinc and Cd considerably decreased yields of all four species. Yields of E. nevadensis were increased by Ni at 250 and 500 mg/kg applied to desert soil. Ephedra nevadensis was more tolerant of Nimore » than were the other three desert shrubs. Some interactions were observed among various elements: manganese concentration was increased in shrubs by Zn. Particularly, application of Ni reduced the concentrations of Zn and Mn over the control.« less

Evolutionary patterns in trace metal (cd and zn) efflux capacity in aquatic organisms.

PubMed

Poteat, Monica D; Garland, Theodore; Fisher, Nicholas S; Wang, Wen-Xiong; Buchwalter, David B

2013-07-16

The ability to eliminate (efflux) metals is a physiological trait that acts as a major driver of bioaccumulation differences among species. This species-specific trait plays a large role in determining the metal loads that species will need to detoxify to persist in chronically contaminated environments and, therefore, contributes significantly to differences in environmental sensitivity among species. To develop a better understanding of how efflux varies within and among taxonomic groupings, we compared Cd and Zn efflux rate constants (ke values) among members of two species-rich aquatic insect families, Ephemerellidae and Hydropsychidae, and discovered that ke values strongly covaried across species. This relationship allowed us to successfully predict Zn efflux from Cd data gathered from aquatic species belonging to other insect orders and families. We then performed a broader, comparative analysis of Cd and Zn ke values from existing data for arthropods, mollusks, annelids, and chordates (77 species total) and found significant phylogenetic patterns. Taxonomic groups exhibited marked variability in ke magnitudes and ranges, suggesting that some groups are more constrained than others in their abilities to eliminate metals. Understanding broader patterns of variability can lead to more rational extrapolations across species and improved protectiveness in water-quality criteria and ecological assessment.

Synthesis and characterization of CdSe/ZnS quantum dots conjugated with poly (ethylene glycol) diamine

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

Bharti, Shivani; Tripathi, S. K., E-mail: surya@pu.ac.in; Kaur, Gurvir

2015-08-28

Bio-functionalization or surface modification is an important technique to obtain biocompatibility in semiconductor nanoparticles for biomedical applications. In this study semiconductor core/shell quantum dots of CdSe/ZnS have been prepared by chemical reduction method and then further PEGylated using Poly(ethylene glycol) diamine of M{sub w} 2000. They were characterized by UV-vis spectroscopy & Fourier transform infrared spectroscopy. The results reveals the successful PEGylation of CdSe/ZnS quantum dots.

Homogeneity of CdZnTe detectors

NASA Astrophysics Data System (ADS)

Hermon, H.; Schieber, M.; James, R. B.; Lund, J.; Antolak, A. J.; Morse, D. H.; Kolesnikov, N. N. P.; Ivanov, Y. N.; Goorsky, M. S.; Yoon, H.; Toney, J.; Schlesinger, T. E.

1998-02-01

We describe the current state of nuclear radiation detectors produced from single crystals of Cd 1- xZn xTe(CZT), with 0.04 < x < 0.4, grown by the vertical high pressure Bridgman (VHPB) method. The crystals investigated were grown commercially both in the USA and at the Institute of Solid State Physics, Chernogolska, Russia. The CZT was evaluated by Sandia National Laboratories and the UCLA and CMU groups using proton-induced X-ray emission (PIXE), X-ray diffraction (XRD), photoluminescence (PL), infrared (IR) transmission microscopy, leakage current measurements and response to nuclear radiation. We discuss the homogeneity of the various CZT crystals based on the results from these measurement techniques.

Investigation of magnetic order in SmTr2Zn20 (Tr=Fe ,Co,Ru) and SmTr2Cd20 (Tr=Ni ,Pd)

NASA Astrophysics Data System (ADS)

Yazici, D.; White, B. D.; Ho, P.-C.; Kanchanavatee, N.; Huang, K.; Friedman, A. J.; Wong, A. S.; Burnett, V. W.; Dilley, N. R.; Maple, M. B.

2014-10-01

Single crystals of the "cage compounds" SmTr2Zn20 (Tr=Fe, Co, Ru) and SmTr2Cd20 (Tr=Ni, Pd) have been investigated by means of electrical resistivity, magnetization, and specific-heat measurements. The compounds SmFe2Zn20,SmRu2Zn20, and SmNi2Cd20 exhibit ferromagnetic order with Curie temperatures of TC=47.4, 7.6, and 7.5 K, respectively, whereas SmPd2Cd20 is an antiferromagnet with a Néel temperature of TN=3.4 K. No evidence for magnetic order is observed in SmCo2Zn20 down to 110 mK. The Sommerfeld coefficients γ are found to be 57 mJ /molK2 for SmFe2Zn20,79.5 mJ /molK2 for SmCo2Zn20,258 mJ /molK2 for SmRu2Zn20,165 mJ /molK2 for SmNi2Cd20, and 208 mJ /molK2 for SmPd2Cd20. Enhanced values of γ and a quadratic temperature dependence of the electrical resistivity at low temperature for SmRu2Zn20 and SmPd2Cd20 suggest an enhancement of the quasiparticle masses due to hybridization between localized 4f and conduction electron states.

Geospatial Mapping of Pb, Cr, Cu, Zn, Cd, and Sb in Urban Soil, Cd. Juarez, Chihuahua, Mexico

NASA Astrophysics Data System (ADS)

Amaya, M. A.; Grimida, S. E.; Elkekli, A. R.; Aldouri, R. K.; Benedict, B. A.; Pingitore, N. E., Jr.

2015-12-01

Population-based random stratified sampling of the city of Cd. Juarez, Chihuahua, Mexico provided 500 city blocks for study. We collected soil from the public space (where present) in front of each house on a selected block; equal measured small volumes of these were combined to produce a composite sample for analysis. Such composite samples (1) decrease, by an order of magnitude, laboratory processing and analysis costs, and (2) smooth the data to represent blocks as averages of individual houses. Retention of the unanalyzed samples of the individual houses permits their later analysis should the composites suggest further study of individual houses on an anomalous block. Elemental analysis of 10 mg pressed powders was performed on a Panalytical Epsilon5 EDS-XRF, via 8 secondary targets and 12 USGS and NIST multi-element rock standards. The mean and (range) of concentration for Pb was 43 (13-550) ppm; for Cr, 31 (1.8-76); for Cu, 22 (6-550); for Zn 84 (42-415) ppm; for Cd, 1.9 (0.1-6.2); and for Sb, 5.9 (2.7-29). The old urban core of Cd. Juarez was marked by high levels of Pb, Cr, Cu, and Zn, and, to a smaller degree, of Cd and Sb. This pattern mirrors that of contiguous El Paso, Texas, USA, directly across the narrow Rio Grande. Businesses, industrial facilities, transportation (both railroads and highways), traditional "downtown" shopping, and old residential districts cluster in this urban core. A Pb-Cu-Zn smelter, which operated for more than a century until 1999, is present in the US adjacent to the Rio Grande, about two km away from downtown Cd. Juarez. Thus the city has been subject to both traditional metal sources (e.g., leaded gasoline, highway debris) and smelter emissions. The poplation of Cd. Juarez has exploded in the last few decades to some 1.5 million inhabitants due both to natural growth and in-migration from rural districts for economic opportunity. Most of this growth has been accommodated by radial expansion of the city into the surrounding

Unique dielectric features of a ceramic-semiconductor nanocomposite MgNb2O6 + 0.25Zn0.5Cd0.5S

NASA Astrophysics Data System (ADS)

Pukazhselvan, D.; Selvaraj, Nivas Babu; Bdikin, Igor; Saravanan, R. Sakthi Sudar; Jakka, Suresh Kumar; Soares, M. J.; Fagg, Duncan Paul

2017-12-01

The present communication deals with the optical/dielectric characteristics of MgNb2O6 + 0.25Zn0.5Cd0.5S nanocomposite (10-30 nm) mixture. Zn0.5Cd0.5S (size ∼10 nm) was synthesized by microwave assisted solvo-thermal method. Monophase magnesium niobate (MN) nanoparticles (10-20 nm) were synthesized in a single step by mechanochemical treatment of MgO + Nb2O5 under dry N2 atmosphere. The nanocomposite, MgNb2O6 + 0.25Zn0.5Cd0.5S, was prepared by mechanical admixing of MgNb2O6 and Zn0.5Cd0.5S taken in 4:1 molar ratio. The photoluminescence study shows violet, yellow and orange-red emissions by the MgNb2O6 + 0.25Zn0.5Cd0.5S composite. The observed dielectric constant value (ε) for MgNb2O6 + 0.25Zn0.5Cd0.5S is only 4.7, which is ∼5 times smaller than the ε value of MgNb2O6 while a dielectric loss for the composite being closer to zero ensures promising commercial applications.

Band engineering in core/shell ZnTe/CdSe for photovoltage and efficiency enhancement in exciplex quantum dot sensitized solar cells.

PubMed

Jiao, Shuang; Shen, Qing; Mora-Seró, Iván; Wang, Jin; Pan, Zhenxiao; Zhao, Ke; Kuga, Yuki; Zhong, Xinhua; Bisquert, Juan

2015-01-27

Even though previously reported CdTe/CdSe type-II core/shell QD sensitizers possess intrinsic superior optoelectronic properties (such as wide absorption range, fast charge separation, and slow charge recombination) in serving as light absorbers, the efficiency of the resultant solar cell is still limited by the relatively low photovoltage. To further enhance photovoltage and cell efficiency accordingly, ZnTe/CdSe type-II core/shell QDs with much larger conduction band (CB) offset in comparison with that of CdTe/CdSe (1.22 eV vs 0.27 eV) are adopted as sensitizers in the construction of quantum dot sensitized solar cells (QDSCs). The augment of band offset produces an increase of the charge accumulation across the QD/TiO2 interface under illumination and induces stronger dipole effects, therefore bringing forward an upward shift of the TiO2 CB edge after sensitization and resulting in enhancement of the photovoltage of the resultant cell devices. The variation of relative chemical capacitance, Cμ, between ZnTe/CdSe and reference CdTe/CdSe cells extracted from impedance spectroscopy (IS) characterization under dark and illumination conditions clearly demonstrates that, under light irradiation conditions, the sensitization of ZnTe/CdSe QDs upshifts the CB edge of TiO2 by the level of ∼ 50 mV related to that in the reference cell and results in the enhancement of V(oc) of the corresponding cell devices. In addition, charge extraction measurements have also confirmed the photovoltage enhancement in the ZnTe/CdSe cell related to reference CdTe/CdSe cell. Furthermore, transient grating (TG) measurements have revealed a faster electron injection rate for the ZnTe/CdSe-based QDSCs in comparison with the CdSe cells. The resultant ZnTe/CdSe QD-based QDSCs exhibit a champion power conversion efficiency of 7.17% and a certified efficiency of 6.82% under AM 1.5 G full one sun illumination, which is, as far as we know, one of the highest efficiencies for liquid-junction QDSCs.

CdSe/ZnS Quantum Dots trigger DNA repair and antioxidant enzyme systems in Medicago sativa cells in suspension culture

PubMed Central

2013-01-01

Background Nanoparticles appear to be promising devices for application in the agriculture and food industries, but information regarding the response of plants to contact with nano-devices is scarce. Toxic effects may be imposed depending on the type and concentration of nanoparticle as well as time of exposure. A number of mechanisms may underlie the ability of nanoparticles to cause genotoxicity, besides the activation of ROS scavenging mechanisms. In a previous study, we showed that plant cells accumulate 3-Mercaptopropanoic acid-CdSe/ZnS quantum dots (MPA-CdSe/ZnS QD) in their cytosol and nucleus and increased production of ROS in a dose dependent manner when exposed to QD and that a concentration of 10 nM should be cyto-compatible. Results When Medicago sativa cells were exposed to 10, 50 and 100 nM MPA-CdSe/ZnS QD a correspondent increase in the activity of Superoxide dismutase, Catalase and Glutathione reductase was registered. Different versions of the COMET assay were used to assess the genotoxicity of MPA-CdSe/ZnS QD. The number of DNA single and double strand breaks increased with increasing concentrations of MPA-CdSe/ZnS QD. At the highest concentrations, tested purine bases were more oxidized than the pyrimidine ones. The transcription of the DNA repair enzymes Formamidopyrimidine DNA glycosylase, Tyrosyl-DNA phosphodiesterase I and DNA Topoisomerase I was up-regulated in the presence of increasing concentrations of MPA-CdSe/ZnS QD. Conclusions Concentrations as low as 10 nM MPA-CdSe/ZnS Quantum Dots are cytotoxic and genotoxic to plant cells, although not lethal. This sets a limit for the concentrations to be used when practical applications using nanodevices of this type on plants are being considered. This work describes for the first time the genotoxic effect of Quantum Dots in plant cells and demonstrates that both the DNA repair genes (Tdp1β, Top1β and Fpg) and the ROS scavenging mechanisms are activated when MPA-CdSe/ZnS QD contact M. sativa

Photosensitization of ZnO nanowires with CdSe quantum dots for photovoltaic devices.

PubMed

Leschkies, Kurtis S; Divakar, Ramachandran; Basu, Joysurya; Enache-Pommer, Emil; Boercker, Janice E; Carter, C Barry; Kortshagen, Uwe R; Norris, David J; Aydil, Eray S

2007-06-01

We combine CdSe semiconductor nanocrystals (or quantum dots) and single-crystal ZnO nanowires to demonstrate a new type of quantum-dot-sensitized solar cell. An array of ZnO nanowires was grown vertically from a fluorine-doped tin oxide conducting substrate. CdSe quantum dots, capped with mercaptopropionic acid, were attached to the surface of the nanowires. When illuminated with visible light, the excited CdSe quantum dots injected electrons across the quantum dot-nanowire interface. The morphology of the nanowires then provided the photoinjected electrons with a direct electrical pathway to the photoanode. With a liquid electrolyte as the hole transport medium, quantum-dot-sensitized nanowire solar cells exhibited short-circuit currents ranging from 1 to 2 mA/cm2 and open-circuit voltages of 0.5-0.6 V when illuminated with 100 mW/cm2 simulated AM1.5 spectrum. Internal quantum efficiencies as high as 50-60% were also obtained.

Core–shell interaction and its impact on the optical absorption of pure and doped core-shell CdSe/ZnSe nanoclusters

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

Wang, Xinqin; Cui, Yingqi; Zeng, Qun

The structural, electronic, and optical properties of core-shell nanoclusters, (CdSe){sub x}@(CdSe){sub y} and their Zn-substituted complexes of x = 2–4 and y = 16–28, were studied with density functional theory calculations. The substitution was applied in the cores, the shells, and/or the whole clusters. All these clusters are characterized by their core-shell structures in which the core-shell interaction was found different from those in core or in shell, as reflected by their bondlengths, volumes, and binding energies. Moreover, the core and shell combine together to compose a new cluster with electronic and optical properties different from those of separated individuals,more » as reflected by their HOMO-LUMO gaps and optical absorptions. With the substitution of Cd by Zn, the structural, electronic, and optical properties of clusters change regularly. The binding energy increases with Zn content, attributed to the strong Zn–Se bonding. For the same core/shell, the structure with a CdSe shell/core has a narrower gap than that with a ZnSe shell/core. The optical absorption spectra also change accordingly with Zn substitution. The peaks blueshift with increasing Zn concentration, accompanying with shape variations in case large number of Cd atoms are substituted. Our calculations reveal the core-shell interaction and its influence on the electronic and optical properties of the core-shell clusters, suggesting a composition–structure–property relationship for the design of core-shell CdSe and ZnSe nanoclusters.« less

Comparison of the surfaces and interfaces formed for sputter and electroless deposited gold contacts on CdZnTe

NASA Astrophysics Data System (ADS)

Bell, Steven J.; Baker, Mark A.; Duarte, Diana D.; Schneider, Andreas; Seller, Paul; Sellin, Paul J.; Veale, Matthew C.; Wilson, Matthew D.

2018-01-01

Cadmium zinc telluride (CdZnTe) is a leading sensor material for spectroscopic X/γ-ray imaging in the fields of homeland security, medical imaging, industrial analysis and astrophysics. The metal-semiconductor interface formed during contact deposition is of fundamental importance to the spectroscopic performance of the detector and is primarily determined by the deposition method. A multi-technique analysis of the metal-semiconductor interface formed by sputter and electroless deposition of gold onto (111) aligned CdZnTe is presented. Focused ion beam (FIB) cross section imaging, X-ray photoelectron spectroscopy (XPS) depth profiling and current-voltage (IV) analysis have been applied to determine the structural, chemical and electronic properties of the gold contacts. In a novel approach, principal component analysis has been employed on the XPS depth profiles to extract detailed chemical state information from different depths within the profile. It was found that electroless deposition forms a complicated, graded interface comprised of tellurium oxide, gold/gold telluride particulates, and cadmium chloride. This compared with a sharp transition from surface gold to bulk CdZnTe observed for the interface formed by sputter deposition. The electronic (IV) response for the detector with electroless deposited contacts was symmetric, but was asymmetric for the detector with sputtered gold contacts. This is due to the electroless deposition degrading the difference between the Cd- and Te-faces of the CdZnTe (111) crystal, whilst these differences are maintained for the sputter deposited gold contacts. This work represents an important step in the optimisation of the metal-semiconductor interface which currently is a limiting factor in the development of high resolution CdZnTe detectors.

SILAR controlled CdSe nanoparticles sensitized ZnO nanorods photoanode for solar cell application: Electrolyte effect.

PubMed

Nikam, Pratibha R; Baviskar, Prashant K; Majumder, Sutripto; Sali, Jaydeep V; Sankapal, Babasaheb R

2018-08-15

Controlled growth of different sizes of cadmium selenide (CdSe) nanoparticles over well aligned ZnO nanorods have been performed using successive ionic layer adsorption and reaction (SILAR) technique at room temperature (27 °C) in order to form nano heterostructure solar cells. Deposition of compact layer of zinc oxide (ZnO) by SILAR technique on fluorine doped tin oxide (FTO) coated glass substrate followed by growth of vertically aligned ZnO nanorods array using chemical bath deposition (CBD) at low temperature (<100 °C). Different characterization techniques viz. X-ray diffractometer, UV-Vis spectrophotometer, field emission scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy have been used to know the structural, optical, morphological and compositional properties of synthesized nano heterostructure. The photovoltaic performance of the cells with variation in SILAR cycles for CdSe and with use of different electrolytes have been recorded as J-V characteristics and the maximum conversion efficiency of 0.63% have been attained with ferro/ferri cyanide electrolyte for 12 cycles CdSe coating over 1-D ZnO nanorods. Copyright © 2018 Elsevier Inc. All rights reserved.

Effect of Te inclusions in CdZnTe crystals at different temperatures

NASA Astrophysics Data System (ADS)

Hossain, A.; Bolotnikov, A. E.; Camarda, G. S.; Gul, R.; Kim, K.-H.; Cui, Y.; Yang, G.; Xu, L.; James, R. B.

2011-02-01

CdZnTe crystals often exhibit nonuniformities due to the presence of Te inclusions and dislocations. High concentrations of such defects in these crystals generally entail severe charge-trapping, a major problem in ensuring the device's satisfactory performance. In this study, we employed a high-intensity, high-spatial-resolution synchrotron x-ray beam as the ideal tool to generate charges by focusing it over the large Te inclusions, and then observing the carrier's response at room- and at low-temperatures. A high spatial 5-μm resolution raster scan revealed the fine details of the presence of extended defects, like Te inclusions and dislocations in the CdZnTe crystals. A noticeable change was observed in the efficiency of electron charge collection at low temperature (1 °C), but it was hardly altered at room-temperature.

Effects of sub-bandgap illumination on electrical properties and detector performances of CdZnTe:In

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

Xu, Lingyan; Jie, Wanqi, E-mail: jwq@nwpu.edu.cn; Zha, Gangqiang, E-mail: zha-gq@hotmail.com

2014-06-09

The effects of sub-bandgap illumination on electrical properties of CdZnTe:In crystals and spectroscopic performances of the fabricated detectors were discussed. The excitation process of charge carriers through thermal and optical transitions at the deep trap could be described by the modified Shockley-Read-Hall model. The ionization probability of the deep donor shows an increase under illumination, which should be responsible for the variation of electrical properties within CdZnTe bulk materials with infrared (IR) irradiation. By applying Ohm's law, diffusion model and interfacial layer-thermionic-diffusion theory, we obtain the decrease of bulk resistivity and the increase of space charge density in the illuminatedmore » crystals. Moreover, the illumination induced ionization will further contribute to improving carrier transport property and charge collection efficiency. Consequently, the application of IR irradiation in the standard working environment is of great significance to improve the spectroscopic characteristics of CdZnTe radiation detectors.« less

Synthesis and luminescence characterization of Y2 BaZnO5 :RE (RE = Eu3+ , Tb3+ , Pr3+ and Sm3+ ) phosphors.

PubMed

Taikar, D R; Joshi, C P; Moharil, S V

2017-09-01

Modified synthesis and luminescence of Y 2 BaZnO 5 phosphors activated with the rare earths (RE) Eu 3 + , Tb 3 + , Pr 3 + and Sm 3 + are reported. RE 2 BaZnO 5 phosphors have attracted attention because of their interesting magnetic and optical properties; and are usually prepared using a two-step solid-state reaction. In the first step, carbonates or similar precursors are thoroughly mixed and heated at 900°C to decompose them to oxides. To eliminate the unwanted phases like BaRE 2 O 4 , the resulting powders are reheated at 1100°C for a long time. We prepared Y 2 BaZnO 5 phosphors activated with various activators by replacing the first step with combustion synthesis. The photoluminescence results are presented. The photoluminescence results for Eu 3 + , Tb 3 + and Pr 3 + are in good agreement with the literature. However, photoluminescence emission from Sm 3 + has not been documented previously. The excitation spectrum of Eu 3 + is dominated by a charge transfer band around 261 nm, and an additional band around 238 nm is always present, irrespective of the type of activator. The presence of this band for all these different types of activators was interpreted as host absorption. Copyright © 2016 John Wiley & Sons, Ltd.

Investigations on the structural, morphological, optical and electrical properties of undoped and nanosized Zn-doped CdS thin films prepared by a simplified spray technique

NASA Astrophysics Data System (ADS)

Anbarasi, M.; Nagarethinam, V. S.; Balu, A. R.

2014-12-01

CdS and Zn-doped CdS (CdS:Zn) thin films have been deposited on glass substrates by spray pyrolysis technique using a perfume atomizer. The influence of Zn incorporation on the structural, morphological, optical and electrical properties of the films has been studied. All the films exhibit hexagonal phase with (0 0 2) as preferential orientation. A shift of the (0 0 2) diffraction peak towards higher diffraction angle is observed with increased Zn doping. The optical studies confirmed that the transparency increases as Zn doping level increases and the film coated with 2 at.% Zn doping has the maximum transmittance of about 90 %. The sheet resistance (R sh ) decreases as the Zn-doping level increases and a minimum value of 1.113 × 103 Ω/sq is obtained for the film coated with 8 at.% Zn dopant. The CdS film coated with 8 at.% Zn dopant has the best structural, morphological and electrical properties.

Photoelectrochemical determination of tert-butylhydroquinone in edible oil samples employing CdSe/ZnS quantum dots and LiTCNE.

PubMed

Monteiro, Thatyara Oliveira; Tanaka, Auro Atsushi; Damos, Flávio Santos; Luz, Rita de Cássia Silva

2017-07-15

A novel photoelectrochemical sensor was developed for determination of tert-butyl-hydroquinone (TBHQ) in edible vegetable oils, based on CdSe/ZnS core-shell quantum dots sensitized with lithium tetracyanoethylenide (LiTCNE). The CdSe/ZnS/LiTCNE photoelectrochemical sensor presented a TBHQ photocurrent about 13-fold higher and a charge transfer resistance 62-fold lower than observed for a CdSe/ZnS sensor. The photoelectrochemical sensor showed selectivity to TBHQ, with a high photocurrent for this antioxidant compared to the photocurrent responses for other phenolic antioxidants. The CdSe/ZnS/LiTCNE photoelectrochemical sensor presented a linear range from 0.6 to 250μmolL -1 , sensitivity of 0.012μALμmol -1 , and a limit of detection of 0.21μmolL -1 for TBHQ, under optimized experimental conditions. The sensor was successfully employed in the analysis of edible oil samples, with recoveries of between 98.25% and 99.83% achieved. Copyright © 2017 Elsevier Ltd. All rights reserved.

Superconductivity at different T{sub c} in CdBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub y}

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

Balchev, N.; Lovchinov, V.; Gattef, E.

1995-06-01

A Cd analogue of the Tl and Hg n=3 series with nominal composition CdBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub y} has been synthesized. The samples were superconducting according to magnetic susceptibility measurements. The critical temperature was 103 or 107 K depending on the preparation conditions. The EDX analysis revealed the presence of Cd-1111, Cd-1121, and Cd-2333 as minor phases. The observed diamagnetic effects were attributed to the different T{sub c} of these phases.

The salen based chemosensors for highly selective recognition of Zn2+ ion.

PubMed

Zhu, Wenkai; Du, LongChao; Li, Wensheng; Zuo, Jinyan; Shan, Jingrui

2018-06-03

Two novel salen based chemosensors have been successfully synthesized. UV-vis absorption, fluorescence emission spectroscopy and cyclic voltammetry (CV) were exploited to investigate their recognition toward various metal ions, including Na + , K + , Mg 2+ , Al 3+ , Zn 2+ , Ag + , Pb 2+ , Co 2+ , Li + , Ba 2+ , Ca 2+ , Cd 2+ , La 3+ , Cu 2+ and Mn 2+ ions. The results indicated that the sensor L1 and L2 exhibited highly selective and sensitive recognition for Zn 2+ ions. The binding stoichiometry ratio of L1-Zn 2+ /L2-Zn 2+ were recognized as 4:1 by the method of Job's plot. Meanwhile, this investigation is confirmed by 1 H NMR. These results indicated that L1 and L2 can be applied as chemosensor for the detection of Zn 2+ ion. Copyright © 2018 Elsevier B.V. All rights reserved.

Down-top nanofabrication of binary (CdO)x (ZnO)1–x nanoparticles and their antibacterial activity

PubMed Central

Al-Hada, Naif Mohammed; Mohamed Kamari, Halimah; Abdullah, Che Azurahanim Che; Saion, Elias; Shaari, Abdul H; Talib, Zainal Abidin; Matori, Khamirul Amin

2017-01-01

In the present study, binary oxide (cadmium oxide [CdO])x (zinc oxide [ZnO])1–x nanoparticles (NPs) at different concentrations of precursor in calcination temperature were prepared using thermal treatment technique. Cadmium and zinc nitrates (source of cadmium and zinc) with polyvinylpyrrolidone (capping agent) have been used to prepare (CdO)x (ZnO)1–x NPs samples. The sample was characterized by X-ray diffraction (XRD), scanning electron microscopy, energy-dispersive X-ray (EDX), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy. XRD patterns analysis revealed that NPs were formed after calcination, which showed a cubic and hexagonal crystalline structure of (CdO)x (ZnO)1–x NPs. The phase analysis using EDX spectroscopy and FTIR spectroscopy confirmed the presence of Cd and Zn as the original compounds of prepared (CdO)x (ZnO)1–x NP samples. The average particle size of the samples increased from 14 to 33 nm as the concentration of precursor increased from x=0.20 to x=0.80, as observed by TEM results. The surface composition and valance state of the prepared product NPs were determined by X-ray photoelectron spectroscopy (XPS) analyses. Diffuse UV–visible reflectance spectra were used to determine the optical band gap through the Kubelka–Munk equation; the energy band gap was found to decrease for CdO from 2.92 to 2.82 eV and for ZnO from 3.22 to 3.11 eV with increasing x value. Additionally, photoluminescence (PL) spectra revealed that the intensity in PL increased with an increase in particle size. In addition, the antibacterial activity of binary oxide NP was carried out in vitro against Escherichia coli ATCC 25922 Gram (−ve), Salmonella choleraesuis ATCC 10708, and Bacillus subtilis UPMC 1175 Gram (+ve). This study indicated that the zone of inhibition of 21 mm has good antibacterial activity toward the Gram-positive B. subtilis UPMC 1175. PMID:29200844

Segregation formation, thermal and electronic properties of ternary cubic CdZnTe clusters: MD simulations and DFT calculations

NASA Astrophysics Data System (ADS)

Kurban, Mustafa; Erkoç, Şakir

2017-04-01

Surface and core formation, thermal and electronic properties of ternary cubic CdZnTe clusters are investigated by using classical molecular dynamics (MD) simulations and density functional theory (DFT) calculations. In this work, MD simulations of the CdZnTe clusters are performed by means of LAMMPS by using bond order potential (BOP). MD simulations are carried out at different temperatures to study the segregation phenomena of Cd, Zn and Te atoms, and deviation of clusters and heat capacity. After that, using optimized geometries obtained, excess charge on atoms, dipole moments, highest occupied molecular orbitals, lowest unoccupied molecular orbitals, HOMO-LUMO gaps (Eg) , total energies, spin density and the density of states (DOS) have been calculated with DFT. Simulation results such as heat capacity and segregation formation are compared with experimental bulk and theoretical results.

Synthesis and coordination chemistry of TpC*MI complexes where M=Mg, Ca, Sr, Ba and Zn and TpC*=tris[3-(2-methoxy-1,1-dimethyl)pyrazolyl]hydroborate.

PubMed

Chisholm, Malcolm H; Gallucci, Judith C; Yaman, Gulsah

2009-01-14

Reactions involving MI2 where M=Mg, Ca, Sr, Ba or Zn and M'TpC* where M'=Na or Tl and TpC*=tris[3-methoxy-1,1-dimethyl)pyrazolyl]hydroborate in tetrahydrofuran are described leading to the isolation and characterization of the complexes TpC*MgI, , TpC*CaI, , TpC*SrI, , TpC*SrI(THF), , TpC*BaI, , TpC*BaI(pz*H), , where pz*H=3-(2-methoxyl-1,1-dimethyl)pyrazole, TpC*BaI.1/2toluene, and TpC*ZnI, . The compounds , , , , and have been characterized by single-crystal X-ray crystallography. Compounds and are isostructural and are salt-like containing kappa6-TpM+ cations and I- anions. In all other structures, the iodide is bound to the metal and TpC* is kappa6 bonded to the group 2 M(2+) ions. Reactions involving TpC*CaI, , and sodium or lithium alkoxides or amides failed to yield the amide or alkoxide calcium TpC* derivative, though related reactions involving TpC*ZnI, , and KOSiMe3 proceeded quantitatively to yield kappa3TpC*ZnOSiMe3, , which was also structurally characterized and shown to have the kappa3-TpC* bound ligand.

Sensitivity of Four Cyanobacterial Isolates from Tropical Freshwaters to Environmentally Realistic Concentrations of Cr(6+), Cd(2+) and Zn(2.).

PubMed

Munagamage, Thilini; Rathnayake, I V N; Pathiratne, A; Megharaj, Mallavarapu

2016-06-01

Sensitivity of four tropical cyanobacteria viz. Coelosphaerium sp., Synechococcus sp., Oscillatoria sp. and Chroococcus sp. to environmentally relevant concentrations of Cr(6+), Cd(2+) and Zn(2+)was assessed based on fluorescence change as a proxy for growth reduction. At 24 h exposure, the growth reduction inthe cyanobacteria followed the order: Zn(2+) < Cr(6+) ≤ Cd(2+). Of the four cyanobacteria, Synechococcus was the most sensitive for Cr(6+), where as Chroococcus was the most sensitive for Cd(2+)and Zn(2+). Sensitivity was gradually decreased by 96 h implying the acquisition of tolerance by cyanobacteria to heavy metal ions with prolonged exposure.

CdS/CdSe quantum dots and ZnPc dye co-sensitized solar cells with Au nanoparticles/graphene oxide as efficient modified layer.

PubMed

Chen, Cong; Cheng, Yu; Jin, Junjie; Dai, Qilin; Song, Hongwei

2016-10-15

Co-sensitization by using two or more sensitizers with complementary absorption spectra to expand the spectral response range is an effective approach to enhance device performance of quantum dot sensitized solar cells (QDSSCs). To improve the light-harvesting in the visible/near-infrared (NIR) region, organic dye zinc phthalocyanine (ZnPc) was combined with CdS/CdSe quantum dots (QDs) for co-sensitized solar cells based on ZnO inverse opals (IOs) as photoanode. The resulting co-sensitized device shows an efficient panchromatic spectral response feature to ∼750nm and presents an overall conversion efficiency of 4.01%, which is superior to that of the individual ZnPc-sensitized solar cells and CdS/CdSe-sensitized solar cells. Meanwhile, an Au nanoparticles/graphene oxide (Au NPs/GO) composite layer was successfully prepared to modify Cu2S counter electrode for the co-sensitized solar cells. Reducing the carrier recombination process by GO and catalytic process of Au NPs leads to increased power conversion efficiency(PCE) from 4.01 to 4.60% and sustainable stability remains ∼85% of its original value after 60min light exposure. In this paper, introduction of the organic dyes as co-sensitizer and Au NPs/GO as counter electrode modified layer has been proved to be an effective route to improve the performance of QDSSCs. Copyright © 2016 Elsevier Inc. All rights reserved.

Novel ZnO:Al contacts to CdZnTe for X- and gamma-ray detectors

PubMed Central

Roy, U. N.; Mundle, R. M.; Camarda, G. S.; Cui, Y.; Gul, R.; Hossain, A.; Yang, G.; Pradhan, A. K.; James, R. B.

2016-01-01

CdZnTe (CZT) has made a significant impact as a material for room-temperature nuclear-radiation detectors due to its potential impact in applications related to nonproliferation, homeland security, medical imaging, and gamma-ray telescopes. In all such applications, common metals, such as gold, platinum and indium, have been used as electrodes for fabricating the detectors. Because of the large mismatch in the thermal-expansion coefficient between the metal contacts and CZT, the contacts can undergo stress and mechanical degradation, which is the main cause for device instability over the long term. Here, we report for the first time on our use of Al-doped ZnO as the preferred electrode for such detectors. The material was selected because of its better contact properties compared to those of the metals commonly used today. Comparisons were conducted for the detector properties using different contacts, and improvements in the performances of ZnO:Al-coated detectors are described in this paper. These studies show that Al:ZnO contacts to CZT radiation detectors offer the potential of becoming a transformative replacement for the common metallic contacts due to the dramatic improvements in the performance of detectors and improved long-term stability. PMID:27216387

Bioleaching of spent Zn-Mn or Ni-Cd batteries by Aspergillus species.

PubMed

Kim, Min-Ji; Seo, Ja-Yeon; Choi, Yong-Seok; Kim, Gyu-Hyeok

2016-05-01

This research explores the recovery of metals from spent Zn-Mn or Ni-Cd batteries by a bioleaching using six Aspergillus species. Two different nutrients, malt extract and sucrose, were used to produce different types of organic acids. Oxalic acid and citric acid were shown to be the dominant organic acid in malt extract and sucrose media, respectively. In the bioleaching, the metal removal was higher in sucrose media than malt extract. All species, except A. niger KUC5254, showed more than 90% removal of metals from Zn-Mn battery. For Ni-Cd battery, more than 95% of metals was extracted by A. niger KUC5254 and A. tubingensis KUC5037. As a result, A. tubingensis KUC5037 which is a non-ochratoxigenic fungus was considered to have the greatest potential for improving the safety and efficiency of the bioleaching. Copyright © 2015 Elsevier Ltd. All rights reserved.

Conduction band position tuning and Ga-doping in (Cd,Zn)S alloy thin films

DOE PAGES

Baranowski, Lauryn L.; Christensen, Steven; Welch, Adam W.; ...

2017-02-13

In recent years, the number of novel photovoltaic absorber materials under exploration has rapidly increased. However, to reap the most benefit from these new absorbers, alternative device structures and components must also be considered. In particular, the choice of a heterojunction partner, or contact layer, is critical to device optimization. In this work, we explore alternative n-type contact layer candidates that could be widely applicable to a variety of new absorbers. We use theory to calculate the band edge tuning provided by a variety of II-VI alloy systems, and select the (Cd,Zn)S system as one that affords a wide rangemore » of conduction band tuning. The synthesis of (Cd,Zn)S alloys is explored using atomic layer deposition, which afforded precise compositional control and produced crystalline thin films. The predicted tuning of the band gap and conduction band minimum is confirmed through X-ray photoelectron spectroscopy and optical absorption measurements. In addition, we investigated Ga-doping in Cd 0.6Zn 0.4S films to decrease their series resistance when used as contact layers in photovoltaic devices. In conclusion, this study provides a framework for exploring and optimizing alternative contact layer materials, which will prove critical to the success of new PV absorbers.« less

Experimental and Theoretical Investigations of Infrared Multiple Photon Dissociation Spectra of Aspartic Acid Complexes with Zn2+ and Cd2.

PubMed

Boles, Georgia C; Hightower, Randy L; Coates, Rebecca A; McNary, Christopher P; Berden, Giel; Oomens, Jos; Armentrout, P B

2018-04-12

Complexes of aspartic acid (Asp) cationized with Zn 2+ : Zn(Asp-H) + , Zn(Asp-H) + (ACN) where ACN = acetonitrile, and Zn(Asp-H) + (Asp); as well as with Cd 2+ , CdCl + (Asp), were examined by infrared multiple photon dissociation (IRMPD) action spectroscopy using light generated from a free electron laser. A series of low-energy conformers for each complex was found using quantum chemical calculations to identify the structures formed experimentally. The main binding motif observed for the heavy-metal complex, CdCl + (Asp)[N,CO,CO s ], is a charge-solvated, tridentate structure, where the metal center binds to the backbone amino group and carbonyl oxygens of the backbone and side-chain carboxylic acids. Likewise, the deprotonated Zn(Asp-H) + (ACN) and Zn(Asp-H) + (Asp) complexes show comparable [N,CO - ,CO s ](ACN) and [N,CO - ,CO s ][N,CO,CO s ] coordinations, respectively. Interestingly, there was only minor spectral evidence for the analogous Zn(Asp-H) + [N,CO - ,CO s ] binding motif, even though this species is predicted to be the lowest-energy conformer. Instead, rearrangement and partial dissociation of the amino acid are observed, as spectral features most consistent with the experimental spectrum are exhibited by a four-coordinate Zn(Asp-NH 4 ) + [CO 2 - ,CO s ](NH 3 ) complex. Analysis of the mechanistic pathway leading from the predicted lowest-energy conformer to the isobaric deaminated complex is explored theoretically. Further, comparison of the current work to that of Zn 2+ and Cd 2+ complexes of asparagine (Asn) allows additional conclusions regarding populated conformers and effects of carboxamide versus carboxylic acid binding to be drawn.

3-D Spatial Resolution of 350 μm Pitch Pixelated CdZnTe Detectors for Imaging Applications.

PubMed

Yin, Yongzhi; Chen, Ximeng; Wu, Heyu; Komarov, Sergey; Garson, Alfred; Li, Qiang; Guo, Qingzhen; Krawczynski, Henric; Meng, Ling-Jian; Tai, Yuan-Chuan

2013-02-01

We are currently investigating the feasibility of using highly pixelated Cadmium Zinc Telluride (CdZnTe) detectors for sub-500 μ m resolution PET imaging applications. A 20 mm × 20 mm × 5 mm CdZnTe substrate was fabricated with 350 μ m pitch pixels (250 μ m anode pixels with 100 μ m gap) and coplanar cathode. Charge sharing among the pixels of a 350 μ m pitch detector was studied using collimated 122 keV and 511 keV gamma ray sources. For a 350 μ m pitch CdZnTe detector, scatter plots of the charge signal of two neighboring pixels clearly show more charge sharing when the collimated beam hits the gap between adjacent pixels. Using collimated Co-57 and Ge-68 sources, we measured the count profiles and estimated the intrinsic spatial resolution of 350 μ m pitch detector biased at -1000 V. Depth of interaction was analyzed based on two methods, i.e., cathode/anode ratio and electron drift time, in both 122 keV and 511 keV measurements. For single-pixel photopeak events, a linear correlation between cathode/anode ratio and electron drift time was shown, which would be useful for estimating the DOI information and preserving image resolution in CdZnTe PET imaging applications.

3-D Spatial Resolution of 350 μm Pitch Pixelated CdZnTe Detectors for Imaging Applications

PubMed Central

Yin, Yongzhi; Chen, Ximeng; Wu, Heyu; Komarov, Sergey; Garson, Alfred; Li, Qiang; Guo, Qingzhen; Krawczynski, Henric; Meng, Ling-Jian; Tai, Yuan-Chuan

2016-01-01

We are currently investigating the feasibility of using highly pixelated Cadmium Zinc Telluride (CdZnTe) detectors for sub-500 μm resolution PET imaging applications. A 20 mm × 20 mm × 5 mm CdZnTe substrate was fabricated with 350 μm pitch pixels (250 μm anode pixels with 100 μm gap) and coplanar cathode. Charge sharing among the pixels of a 350 μm pitch detector was studied using collimated 122 keV and 511 keV gamma ray sources. For a 350 μm pitch CdZnTe detector, scatter plots of the charge signal of two neighboring pixels clearly show more charge sharing when the collimated beam hits the gap between adjacent pixels. Using collimated Co-57 and Ge-68 sources, we measured the count profiles and estimated the intrinsic spatial resolution of 350 μm pitch detector biased at −1000 V. Depth of interaction was analyzed based on two methods, i.e., cathode/anode ratio and electron drift time, in both 122 keV and 511 keV measurements. For single-pixel photopeak events, a linear correlation between cathode/anode ratio and electron drift time was shown, which would be useful for estimating the DOI information and preserving image resolution in CdZnTe PET imaging applications. PMID:28250476

Metal pollution (Cd, Pb, Zn, and As) in agricultural soils and soybean, Glycine max, in southern China.

PubMed

Zhao, Yunyun; Fang, Xiaolong; Mu, Yinghui; Cheng, Yanbo; Ma, Qibin; Nian, Hai; Yang, Cunyi

2014-04-01

Crops produced on metal-polluted agricultural soils may lead to chronic toxicity to humans via the food chain. To assess metal pollution in agricultural soils and soybean in southern China, 30 soybean grain samples and 17 soybean-field soil samples were collected from 17 sites in southern China, and metal concentrations of samples were analyzed by graphite furnace atomic absorption spectrophotometer. The integrated pollution index was used to evaluate if the samples were contaminated by Cd, Pb, Zn and As. Results showed that Cd concentration of 12 samples, Pb concentration of 2 samples, Zn concentration of 2 samples, and As concentrations of 2 samples were above the maximum permissible levels in soils. The integrated pollution index indicated that 11 of 17 soil samples were polluted by metals. Metal concentrations in soybean grain samples ranged from 0.11 to 0.91 mg kg(-1) for Cd; 0.34 to 2.83 mg kg(-1) for Pb; 42 to 88 mg kg(-1) for Zn; and 0.26 to 5.07 mg kg(-1) for As, which means all 30 soybean grain samples were polluted by Pb, Pb/Cd, Cd/Pb/As or Pb/As. Taken together, our study provides evidence that metal pollution is an important concern in agricultural soils and soybeans in southern China.

Mechanochemical approach for the capping of mixed core CdS/ZnS nanocrystals: Elimination of cadmium toxicity.

PubMed

Bujňáková, Zdenka; Baláž, Matej; Dutková, Erika; Baláž, Peter; Kello, Martin; Mojžišová, Gabriela; Mojžiš, Ján; Vilková, Mária; Imrich, Ján; Psotka, Miroslav

2017-01-15

The wet mechanochemical procedure for the capping of the CdS and CdS/ZnS quantum dot nanocrystals is reported. l-cysteine and polyvinylpyrrolidone (PVP) were used as capping agents. When using l-cysteine, the dissolution of cadmium(II) was almost none for CdS/ZnS nanocrystals. Moreover, prepared CdS- and CdS/ZnS-cysteine nanosuspensions exhibited unimodal particle size distributions with very good stability, which was further supported by the zeta potential measurements. The Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy showed the successful embedment of cysteine into the structure of the nanocrystals. Additionally, the optical properties were examined, and the results showed that the cysteine nanosuspension has promising fluorescence properties. On the other hand, PVP was not determined to be a very suitable capping agent for the present system. In this case, the release of cadmium(II) was higher in comparison to the l-cysteine capped samples. The nanosuspensions were successfully used for in vitro studies on selected cancer cell lines. Using fluorescence microscopy, it was evidenced that the nanocrystals enter the cell and that they can serve as imaging agents in biomedical applications. Copyright © 2016. Published by Elsevier Inc.

White-light-controlled resistive switching in ZnO/BaTiO3/C multilayer layer at room temperature

NASA Astrophysics Data System (ADS)

Wang, Junshuai; Liang, Dandan; Wu, Liangchen; Li, Xiaoping; Chen, Peng

2018-07-01

The bipolar resistance switching effect is observed in ZnO/BaTiO3/C structure. The resistance switching behavior can be modulated by white light. The resistance switch states and threshold voltage can be changed when subjected to white light. This research can help explore multi-functional materials and applications in nonvolatile memory device.

Evaluation of the incorporation ratio of ZnO, PbO and CdO into cement clinker.

PubMed

Barros, A M; Tenório, J A S; Espinosa, D C R

2004-08-09

Zinc, lead, and cadmium are minor elements that might be brought by wastes to the cement kilns. This work studies the incorporation ratio of ZnO, PbO, and CdO when they are added to the clinker raw material. The cement raw material used in this work was prepared by mixing pure compounds, this choice was made to avoid the effect of other elements and provide a better understanding of the behavior of these metals during the clinkering process. The samples contained additions of 0.05, 0.10, 0.30, 0.50, 0.80 and 1.00 wt.% of a specific oxide (ZnO, PbO, or CdO) to the clinker raw-meal. The chlorine influence in the ZnO incorporation ratio was also evaluated. A device to simulate the thermal cycle imposed on the charge during the clinker production was used to evaluate the incorporation ratio of these oxides as well as thermogravimetric tests. The products of the tests in the simulator device were submitted to X-ray fluorescence chemical analysis or energy disperse scanning (EDS) microprobe analysis. The results led to the conclusions that the evaporation of Zn in cements kilns is due to the chlorine content and the Pb and Cd incorporation ratio stands around 50 wt.%.

Photoluminescence dynamics of Co-doped Zn 1- xCd xSe and ZnS xSe 1- xcrystals

NASA Astrophysics Data System (ADS)

Born, H.; Thurian, P.; Surkova, T.; Hoffmann, A.; Busse, W.; Gumlich, H.-E.; Broser, I.; Giriat, W.

1998-02-01

Intra-shell d-d relaxation processes of Co 2+ centres are investigated by means of time-integrated and time-resolved photoluminescence spectroscopy. The composition dependence of the luminescence and the decay of the Co L-line in ZnCdSe and ZnSSe alloys is presented for the first time. Additionally, new Co-related infrared luminescence lines were observed near 1.6 eV. Taking into account the energy position of the L-line and the relaxation dynamics of the green and the infrared luminescence, the L-line is explained as an internal doublet-quartet d-d transition of the Co-centres.

Reduction of surface leakage current by surface passivation of CdZn Te and other materials using hyperthermal oxygen atoms

DOEpatents

Hoffbauer, Mark A.; Prettyman, Thomas H.

2001-01-01

Reduction of surface leakage current by surface passivation of Cd.sub.1-x Zn.sub.x Te and other materials using hyperthermal oxygen atoms. Surface effects are important in the performance of CdZnTe room-temperature radiation detectors used as spectrometers since the dark current is often dominated by surface leakage. A process using high-kinetic-energy, neutral oxygen atoms (.about.3 eV) to treat the surface of CdZnTe detectors at or near ambient temperatures is described. Improvements in detector performance include significantly reduced leakage current which results in lower detector noise and greater energy resolution for radiation measurements of gamma- and X-rays, thereby increasing the accuracy and sensitivity of measurements of radionuclides having complex gamma-ray spectra, including special nuclear materials.

Co-sensitization of ZnO by CdS quantum dots in natural dye-sensitized solar cells with polymeric electrolytes to improve the cell stability

NASA Astrophysics Data System (ADS)

Junhom, W.; Magaraphan, R.

2015-05-01

The CdS quantum dots (QDs) were deposited on ZnO layer by chemical bath deposition method to absorb light in the shorter wavelength region and used as photoanode in the dye sensitized solar cell (DSSCs) with natural dye extracted from Noni leaves. Microstructures of CdS-ZnO from various dipping time were characterized by XRD, FE-SEM and EDX. The results showed that the CdS is hexagonal structure and the amount of CdS increases when the dipping time increases. The maximal conversion efficiency of 0.292% was achieved by the DSSCs based on CdS QDs-sensitized ZnO film obtained from 9 min-dipping time. Furthermore, the stability of DSSCs was improved by using polymeric electrolyte. Poly (acrylic acid) (PAA) and Polyacrylamide (PAM) were introduced to CdS QDs-sensitized ZnO film from 9 min-dipping time. Each polymeric electrolyte was prepared by swelling from 0.1-2.0 %w in H2O. The maximal conversion efficiency of 0.207% was achieved for DSSCs based on CdS QDs-sensitized ZnO film with PAM 1.0% and the conversion efficiency was decreased 25% when it was left for1 hr.

Efficiency of several leaching reagents on removal of Cu, Pb, Cd, and Zn from highly contaminated paddy soil.

PubMed

Gao, Ruili; Zhu, Pengfei; Guo, Guangguang; Hu, Hongqing; Zhu, Jun; Fu, Qingling

2016-11-01

The efficiency of five different single leaching reagents (tartaric acid (TA), citric acid (CA), CaCl 2 , FeCl 3 , EDTA) and two different composite leaching reagents (CA + FeCl 3 , CA + EDTA) on removing Cu, Pb, Zn, and Cd from contaminated paddy soil in Hunan Province (in China) was studied. The results indicated that the efficiencies of CA, FeCl 3 , and EDTA on extracting Cu, Pb, Cd, and Zn from soil were greater than that of TA and CaCl 2 , and their extraction efficiencies were EDTA ≥ FeCl 3 > CA. The efficiencies of CA + FeCl 3 on extracting Cu, Pb, Cd, and Zn were higher than that of single CA or FeCl 3 . The 25 mmol L -1 CA + 20 mmol L -1 FeCl 3 was a promising composite leaching reagent for paddy soil, and it could remove Cu (57.6 %), Pb (59.3 %), Cd (84.8 %), and Zn (28.0 %), respectively. With the same amount of leaching reagent, the efficiency of continuous leaching by several times was higher than that by once. In addition, the easily reducible and oxidizable fractions of heavy metals showed significant decrease during the process of leaching.

Adsorption of Cd, Cu and Zn from aqueous solutions onto ferronickel slag under different potentially toxic metal combination.

PubMed

Park, Jong-Hwan; Kim, Seong-Heon; Kang, Se-Won; Kang, Byung-Hwa; Cho, Ju-Sik; Heo, Jong-Soo; Delaune, Ronald D; Ok, Yong Sik; Seo, Dong-Cheol

2016-01-01

Adsorption characteristics of potentially toxic metals in single- and multi-metal forms onto ferronickel slag were evaluated. Competitive sorption of metals by ferronickel slag has never been reported previously. The maximum adsorption capacities of toxic metals on ferronickel were in the order of Cd (10.2 mg g(-1)) > Cu (8.4 mg g(-1)) > Zn (4.4 mg g(-1)) in the single-metal adsorption isotherm and Cu (6.1 mg g(-1)) > Cd (2.3 mg g(-1)) > Zn (0.3 mg g(-1)) in the multi-metal adsorption isotherm. In comparison with single-metal adsorption isotherm, the reduction rates of maximum toxic metal adsorption capacity in the multi-metal adsorption isotherm were in the following order of Zn (93%) > Cd (78%) > Cu (27%). The Freundlich isotherm provides a slightly better fit than the Langmuir isotherm equation using ferronickel slag for potentially toxic metal adsorption. Multi-metal adsorption behaviors differed from single-metal adsorption due to competition, based on data obtained from Freundlich and Langmuir adsorption models and three-dimensional simulation. Especially, Cd and Zn were easily exchanged and substituted by Cu during multi-metal adsorption. Further competitive adsorption studies are necessary in order to accurately estimate adsorption capacity of ferronickel slag for potentially toxic metals in natural environments.

Interatomic potentials for Cd, Zn, and Hg from absorption spectra

NASA Astrophysics Data System (ADS)

Su, Ching-Hua; Liao, Pok-Kai; Huang, Yu; Liou, Shian-Shyang; Brebrick, R. F.

1984-07-01

The absorption coefficient has been measured over a 65 nm range in the red wing of the 213.8 nm line for Zn vapor at 1000 °C. It has also been measured in the blue wing and over a 60 nm range in the red wing of the 228.7 nm line for Cd vapor at five temperatures between 642 and 955 °C and over a 75 nm range in the red wing of the 253.7 nm line for Hg vapor at five temperatures between 460 and 860 °C. These data are analyzed in terms of the statistical theory of broadening. Oscillator strengths of 1.42±0.01 and 1.61±0.06 are obtained for, respectively, the Cd line and the Zn line. Pair potentials for both the ground and lowest excited state are also obtained in all three cases. For Cd this is done assuming no functional form and then assuming Lennard-Jones potentials. Both methods agree and give a ground state minimum of -47.5 meV at 0.482 nm separation and an excited state minimum of -1.06 eV at 0.410 nm. A functional form is required for the less extensive Zn data and the Lennard-Jones form leads to a range of possibilities including ground and excited state minima of -56 meV at 0.400 nm and -1.30 eV at 0.330 nm, respectively, which are in fair agreement with the theoretical calculations. For Hg the experiments indicate a single excited state and a ground state with a minimum of -55 meV. Assuming no functional form for the pair potentials, taking the excited state as doubly degenerate, and assuming the transition probability from the ground to excited state is one-sixth of the free atom value gives points along the ground and excited state potentials that join smoothly with other experimental results and agree well with the calculation of Baylis for the ground state.

Chemical behavior of Cu, Zn, Cd, and Pb in a eutrophic reservoir: speciation and complexation capacity.

PubMed

Tonietto, Alessandra Emanuele; Lombardi, Ana Teresa; Choueri, Rodrigo Brasil; Vieira, Armando Augusto Henriques

2015-10-01

This research aimed at evaluating cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn) speciation in water samples as well as determining water quality parameters (alkalinity, chlorophyll a, chloride, conductivity, dissolved organic carbon, dissolved oxygen, inorganic carbon, nitrate, pH, total suspended solids, and water temperature) in a eutrophic reservoir. This was performed through calculation of free metal ions using the chemical equilibrium software MINEQL+ 4.61, determination of labile, dissolved, and total metal concentrations via differential pulse anodic stripping voltammetry, and determination of complexed metal by the difference between the total concentration of dissolved and labile metal. Additionally, ligand complexation capacities (CC), such as the strength of the association of metals-ligands (logK'ML) and ligand concentrations (C L) were calculated via Ruzic's linearization method. Water samples were taken in winter and summer, and the results showed that for total and dissolved metals, Zn > Cu > Pb > Cd concentration. In general, higher concentrations of Cu and Zn remained complexed with the dissolved fraction, while Pb was mostly complexed with particulate materials. Chemical equilibrium modeling (MINEQL+) showed that Zn(2+) and Cd(2+) dominated the labile species, while Cu and Pb were complexed with carbonates. Zinc was a unique metal for which a direct relation between dissolved species with labile and complexed forms was obtained. The CC for ligands indicated a higher C L for Cu, followed by Pb, Zn, and Cd in decreasing amounts. Nevertheless, the strength of the association of all metals and their respective ligands was similar. Factor analysis with principal component analysis as the extraction procedure confirmed seasonal effects on water quality parameters and metal speciation. Total, dissolved, and complexed Cu and total, dissolved, complexed, and labile Pb species were all higher in winter, whereas in summer, Zn was mostly present in the

Producibility improvements suggested by a validated process model of seeded CdZnTe vertical Bridgman growth

NASA Astrophysics Data System (ADS)

Larson, David J., Jr.; Casagrande, Louis G.; Di Marzio, Don; Levy, Alan; Carlson, Frederick M.; Lee, Taipao; Black, David R.; Wu, Jun; Dudley, Michael

1994-07-01

We have successfully validated theoretical models of seeded vertical Bridgman-Stockbarger CdZnTe crystal growth and post-solidification processing, using in-situ thermal monitoring and innovative material characterization techniques. The models predict the thermal gradients, interface shape, fluid flow and solute redistribution during solidification, as well as the distributions of accumulated excess stress that causes defect generation and redistribution. Data from the furnace and ampoule wall have validated predictions from the thermal model. Results are compared to predictions of the thermal and thermo-solutal models. We explain the measured initial, change-of-rate, and terminal compositional transients as well as the macrosegregation. Macro and micro-defect distributions have been imaged on CdZnTe wafers from 40 mm diameter boules. Superposition of topographic defect images and predicted excess stress patterns suggests the origin of some frequently encountered defects, particularly on a macro scale, to result from the applied and accumulated stress fields and the anisotropic nature of the CdZnTe crystal. Implications of these findings with respect to producibility are discussed.

Preparation and optical properties of TeO2-BaO-ZnO-ZnF2 fluoro-tellurite glass for mid-infrared fiber Raman laser applications

NASA Astrophysics Data System (ADS)

Li, Jie; Xiao, Xusheng; Gu, Shaoxuan; Xu, Yantao; Zhou, Zhiguang; Guo, Haitao

2017-04-01

A serial of novel fluoro-tellurite glasses with compositions of 60TeO2-20BaO-(20-x)ZnO-xZnF2 (x = 0, 2, 4, 5 and 6 mol%) were prepared. The compositional dependences of glass structural evaluation, Raman gain coefficient, UV-Vis transmission spectrum, IR transmission spectrum, linear refractive index and third-order nonlinearity were analyzed. The results showed that the addition of 6 mol% ZnF2 can further improve the Raman gain coefficient to as well as 52 × 10-11 cm/W and effectively decrease around 73% and 57% absorption coefficients respectively caused by free Osbnd H groups (@3.3 μm) and hydrogen-bonded Osbnd H groups (@4.5 μm) in glass. Addition of ZnF2 does not change the UV-Vis absorption edge, optical band gap energy and infrared region cut-off edge almost, while the linear refraction index and ultrafast third-nonlinearity show unmonotonic changes. These novel fluoro-tellurite glasses may be suitable candidates for using in mid-infrared Raman fiber laser and/or amplifier.

Bioleaching mechanism of Zn, Pb, In, Ag, Cd and As from Pb/Zn smelting slag by autotrophic bacteria.

PubMed

Wang, Jia; Huang, Qifei; Li, Ting; Xin, Baoping; Chen, Shi; Guo, Xingming; Liu, Changhao; Li, Yuping

2015-08-15

A few studies have focused on release of valuable/toxic metals from Pb/Zn smelting slag by heterotrophic bioleaching using expensive yeast extract as an energy source. The high leaching cost greatly limits the practical potential of the method. In this work, autotrophic bioleaching using cheap sulfur or/and pyrite as energy matter was firstly applied to tackle the smelting slag and the bioleaching mechanisms were explained. The results indicated autotrophic bioleaching can solubilize valuable/toxic metals from slag, yielding maximum extraction efficiencies of 90% for Zn, 86% for Cd and 71% for In, although the extraction efficiencies of Pb, As and Ag were poor. The bioleaching performance of Zn, Cd and Pb was independent of leaching system, and leaching mechanism was acid dissolution. A maximum efficiency of 25% for As was achieved by acid dissolution in sulfursulfur oxidizing bacteria (S-SOB), but the formation of FeAsO4 reduced extraction efficiency in mixed energy source - mixed culture (MS-MC). Combined works of acid dissolution and Fe(3+) oxidation in MS-MC was responsible for the highest extraction efficiency of 71% for In. Ag was present in the slag as refractory AgPb4(AsO4)3 and AgFe2S3, so extraction did not occur. Copyright © 2015 Elsevier Ltd. All rights reserved.

Investigation of magnetic order in SmTr2Zn20 (Tr = Fe, Co, Ru) and SmTr2Cd20 (Tr = Ni, Pd)

NASA Astrophysics Data System (ADS)

Yazici, Duygu; White, B. D.; Ho, P.-C.; Kanchanavatee, N.; Huang, K.; Dilley, N. R.; Maple, M. B.

2015-03-01

Single crystals of the cage compounds Sm Tr 2Zn20 (Tr = Fe, Co, Ru) and Sm Tr 2Cd20 (Tr = Ni, Pd) have been investigated by means of electrical resistivity, magnetization, and specific heat measurements. The compounds SmFe2Zn20, SmRu2Zn20,andSmNi2Cd20 exhibit ferromagnetic order with Curie temperatures of TC = 47.4 K, 7.6 K, and 7.5 K, respectively, whereas SmPd2Cd20 is an antiferromagnet with a Néel temperature of TN = 3.4 K. No evidence for magnetic order is observed in SmCo2Zn20 down to 110 mK. The Sommerfeld coefficients γ are found to be 57 mJ/mol-K2 for SmFe2Zn20, 79.5 mJ/mol-K2 for SmCo2Zn20, 258 mJ/mol-K2 for SmRu2Zn20, 165 mJ/mol-K2 for SmNi2Cd20, and 208 mJ/mol-K2 for SmPd2Cd20. Enhanced values of Sommerfeld coefficients γ and a quadratic temperature dependence of the electrical resistivity at low temperature for SmRu2Zn20andSmPd2Cd20 suggest an enhancement of the quasiparticle masses due to hybridization between localized 4 f and conduction electron states. Research at UCSD was supported by the U.S. DOE under Grant No. DE-FG02-04-ER46105 and the U.S. NSF under Award Grant No. DMR 1206553. Research at California State University, Fresno was supported by the U.S. NSF under Grant No. DMR 1104544.

Transparent conducting ZnO-CdO thin films deposited by e-beam evaporation technique

NASA Astrophysics Data System (ADS)

Mohamed, H. A.; Ali, H. M.; Mohamed, S. H.; Abd El-Raheem, M. M.

2006-04-01

Thin films of Zn{1-x} Cd{x}O with x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5 at.% were deposited by electron-beam evaporation technique. It has been found that, for as-deposited films, both the transmittance and electrical resistivity decreased with increasing the Cd content. To improve the optical and electrical properties of these films, the effect of annealing temperature and time were taken into consideration for Zn{1-x} Cd{x}O film with x = 0.2. It was found that, the optical transmittance and the electrical conductivity were improved significantly with increasing the time of annealing. At fixed temperature of 300 °C, the transmittance increased with increasing the time of annealing and reached its maximum values of 81% in the visible region and 94% in the NIR region at annealing time of 120 min. The low electrical resistivity of 3.6 × 10-3 Ω cm was achieved at the same conditions. Other parameters named free carrier concentrations, refractive index, extinction coefficient, plasma frequency, and relaxation time were studied as a function of annealing temperature and time for 20% Cd content.

Effect of thickness on physical properties of electron beam vacuum evaporated CdZnTe thin films for tandem solar cells

NASA Astrophysics Data System (ADS)

Chander, Subhash; Dhaka, M. S.

2016-10-01

The thickness and physical properties of electron beam vacuum evaporated CdZnTe thin films have been optimized in the present work. The films of thickness 300 nm and 400 nm were deposited on ITO coated glass substrates and subjected to different characterization tools like X-ray diffraction (XRD), UV-Vis spectrophotometer, source meter and scanning electron microscopy (SEM) to investigate the structural, optical, electrical and surface morphological properties respectively. The XRD results show that the as-deposited CdZnTe thin films have zinc blende cubic structure and polycrystalline in nature with preferred orientation (111). Different structural parameters are also evaluated and discussed. The optical study reveals that the optical transition is found to be direct and energy band gap is decreased for higher thickness. The transmittance is found to increase with thickness and red shift observed which is suitable for CdZnTe films as an absorber layer in tandem solar cells. The current-voltage characteristics of deposited films show linear behavior in both forward and reverse directions as well as the conductivity is increased for higher film thickness. The SEM studies show that the as-deposited CdZnTe thin films are found to be homogeneous, uniform, small circle-shaped grains and free from crystal defects. The experimental results confirm that the film thickness plays an important role to optimize the physical properties of CdZnTe thin films for tandem solar cell applications as an absorber layer.

Influence of reactive sulfide (AVS) and supplementary food on Ag, Cd and Zn bioaccumulation in the marine polychaete Neanthes arenaceodentata

USGS Publications Warehouse

Lee, J.-S.; Lee, B.-G.; Yoo, H.; Koh, C.-H.; Luoma, S.N.

2001-01-01

A laboratory bioassay determined the relative contribution of various pathways of Ag, Cd and Zn bioaccumulation in the marine polychaete Neanthes arenaceodentata exposed to moderately contaminated sediments. Juvenile worms were exposed for 25 d to experimental sediments containing 5 different reactive sulfide (acid volatile sulfides, AVS) concentrations (1 to 30 ??mol g-1), but with constant Ag, Cd, and Zn concentrations of 0.1, 0.1 and 7 ??mol g-1, respectively. The sediments were supplemented with contaminated food (TetraMin??) containing 3 levels of Ag-Cd-Zn (uncontaminated, 1?? or 5??1 metal concentrations in the contaminated sediment). The results suggest that bioaccumulation of Ag, Cd and Zn in the worms occurred predominantly from ingestion of contaminated sediments and contaminated supplementary food. AVS or dissolved metals (in porewater and overlying water) had a minor effect on bioaccumulation of the 3 metals in most of the treatments. The contribution to uptake from the dissolved source was most important in the most oxic sediments, with maximum contributions of 8% for Ag, 30% for Cd and 20% for Zn bioaccumulation. Sediment bioassays where uncontaminated supplemental food is added could seriously underestimate metal exposures in an equilibrated system; N. arenaceodentata feeding on uncontaminated food would be exposed to 40-60% less metal than if the food source was equilibrated (as occurs in nature). Overall, the results show that pathways of metal exposure are dynamically linked in contaminated sediments and shift as external geochemical characteristics and internal biological attributes vary.

[Immunological balance of CD8+CD28+/CD8+CD28- T lymphocytes can predict gastrointestinal hemorrhage in patients with inflammatory bowel disease].

PubMed

Dai, Shi-Xue; Gu, Hong-Xiang; Wu, Gang; Zhong, Tao; Jian, Hong-Jian; Zhan, Yong-le; Zhang, Min-Hai; Gao, Yong; Xu, Jun; Chen, Dong-Sheng; Liao, Guang-Jie; Feng, Yan-Ling; Liu, Hong-Bo; Zou, Ying; Chi, Hong-Gang

2016-12-20

To evaluate the sensitivity and specificity of CD8 + CD28 + /CD8 + CD28 - T lymphocyte balance in predicting the gastrointestinal hemorrhage (GH) in patients with inflammatory bowel disease (IBD). Forty-nine IBD patients, including 30 with ulcerous colitis (UC) and 19 with Crohn's disease (CD), were enrolled to test peripheral blood CD8 + CD28 + and CD8 + CD28 - T cells using flow cytometry. All the patients were followed up for one year. The receiver-operating characteristic (ROC) curves were used to test the efficiency of CD8 + CD28 + /CD8 + CD28 - T lymphocyte balance to predict GH. The differences in lasting time of remission (LTR) under different factors were compared using Kaplan-Meier survival analysis, and the correlation between CD8 + T lymphocytes and the factors were analyzed. The utilization rates of immunosuppressant, steroids, and biological agent (BA) were significantly higher in CD patients than in UC patients (P=0.003, 0.043 and 0.002, respectively). The frequencies of CD8 + CD28 + T cells were obviously higher in UC patients than those in CD patients (t=3.022, P=0.004). CD8 + CD28 + T cells, CD8 + CD28 - T cells, and especially CD8 + CD28 + /CD8 + CD28 - ratio (area under curve of 0.977, P=0.000; cut-off value of 1.14 [13.95%/12.24%] with a sensitivity of 93.3% and a specificity of 91.2%) showed good efficiencies in predicting GH (P<0.01). The mean and median of LTR of IBD patients who did not receive BA or surgical treatment were significantly longer (Χ 2 =9.730, P=0.002; Χ 2 =15.981, P=0.000). CD8 + CD28 + /CD8 + CD28 - ratio was significantly related to both BA (P=0.009) and surgery (P=0.038). Both decreased CD8 + CD28 + T cells and elevated CD8 + CD28 - T cells are closely correlated with GH, and their ratio can predict the occurrence of GH with a high sensitivity and specificity and is correlated with BA and surgery at the cut-off value of 1.14.

Effect of composting on the Cd, Zn and Mn content and fractionation in feedstock mixtures with wood chips from a short-rotation coppice and bark.

PubMed

Vandecasteele, B; Willekens, K; Zwertvaegher, A; Degrande, L; Tack, F M G; Du Laing, G

2013-11-01

Micronutrient content and availability in composts may be affected by the addition of wood chips or tree bark as a bulking agent in the compost feedstock. In the first part of this study, micronutrient levels were assessed in bark and wood of poplar and willow clones in a short-rotation coppice. Large differences between species were observed in bark concentrations for Cd, Zn and Mn. In the second part of the study, we aimed to determine the effect of feedstock composition and composting on Cd, Zn and Mn concentrations and availability. By means of three composting experiments we examined the effect of (a) bark of different tree species, (b) the amount of bark, and (c) the use of bark versus wood chips. In general, compost characteristics such as pH, organic matter and nutrient content varied due to differences in feedstock mixture and composting process. During the composting process, the availability of Cd, Zn and Mn decreased, although the use of willow and poplar bark or wood chips resulted in elevated total Cd, Zn or Mn concentrations in the compost. Cd concentrations in some composts even exceeded legal criteria. Cd and Zn were mainly bound in the reducible fraction extracted with 0.5M NH2OH⋅HCl. A higher acid-extractable fraction for Mn than for Cd and Zn was found. Higher Cd concentrations in the compost due to the use of bark or wood chips did not result in higher risk of Cd leaching. The results of the pH-stat experiment with gradual acidification of composts illustrated that only a strong pH decline in the compost results in higher availability of Cd, Zn and Mn. Copyright © 2013 Elsevier Ltd. All rights reserved.

The effectiveness of municipal sewage sludge application on the stabilization of Pb, Zn, and Cd in a soil contaminated from mining activities.

PubMed

Xenidis, A; Stouraiti, C; Moirou, A

2001-01-01

The effectiveness of municipal sewage sludge for the stabilisation of Pb, Zn and Cd in a heavily contaminated soil was evaluated by performing pot experiments on soil-sludge mixtures. The soil sample originated from the Montevecchio mining district, Sardinia, Italy, and presented high Pb, Zn and Cd content, as well as US EPA TCLP solubility values for Pb and Cd, which exceeded the respective regulatory limits. Sewage sludge application increased the soil pH. Stabilisation experiments showed that 10% w/w sewage sludge addition effectively reduced Pb and Cd solubilities below the TCLP regulatory limits. At the same addition rate, the EDTA extractable fraction of Pb, Zn, Cd in the treated soil was reduced by 12, 47 and 50% respectively compared with the untreated sample. The five-stage sequential extraction procedure applied on the untreated and treated soil samples, showed a remarkable shift of the metals towards more stable forms. The reducible fractions of Zn and Cd and the residual fraction of Pb were increased by 12, 20 and 18% respectively, while a corresponding decrease in the mobile fractions (exchangeable and carbonate) occurred which accounted for 14, 23 and 25% respectively.

InP/ZnSe/ZnS core-multishell quantum dots for improved luminescence efficiency

NASA Astrophysics Data System (ADS)

Greco, Tonino; Ippen, Christian; Wedel, Armin

2012-04-01

Semiconductor quantum dots (QDs) exhibit unique optical properties like size-tunable emission color, narrow emission peak, and high luminescence efficiency. QDs are therefore investigated towards their application in light-emitting devices (QLEDs), solar cells, and for bio-imaging purposes. In most cases QDs made from cadmium compounds like CdS, CdSe or CdTe are studied because of their facile and reliable synthesis. However, due to the toxicity of Cd compounds and the corresponding regulation (e.g. RoHS directive in Europe) these materials are not feasible for customer applications. Indium phosphide is considered to be the most promising alternative because of the similar band gap (InP 1.35 eV, CdSe 1.73 eV). InP QDs do not yet reach the quality of CdSe QDs, especially in terms of photoluminescence quantum yield and peak width. Typically, QDs are coated with another semiconductor material of wider band gap, often ZnS, to passivate surface defects and thus improve luminescence efficiency. Concerning CdSe QDs, multishell coatings like CdSe/CdS/ZnS or CdSe/ZnSe/ZnS have been shown to be advantageous due to the improved compatibility of lattice constants. Here we present a method to improve the luminescence efficiency of InP QDs by coating a ZnSe/ZnS multishell instead of a ZnS single shell. ZnSe exhibits an intermediate lattice constant of 5.67 Å between those of InP (5.87 Å) and ZnS (5.41 Å) and thus acts as a wetting layer. As a result, InP/ZnSe/ZnS is introduced as a new core-shell quantum dot material which shows improved photoluminescence quantum yield (up to 75 %) compared to the conventional InP/ZnS system.

Co-sensitization of ZnO by CdS quantum dots in natural dye-sensitized solar cells with polymeric electrolytes to improve the cell stability

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

Junhom, W.; Magaraphan, R.

2015-05-22

The CdS quantum dots (QDs) were deposited on ZnO layer by chemical bath deposition method to absorb light in the shorter wavelength region and used as photoanode in the dye sensitized solar cell (DSSCs) with natural dye extracted from Noni leaves. Microstructures of CdS-ZnO from various dipping time were characterized by XRD, FE-SEM and EDX. The results showed that the CdS is hexagonal structure and the amount of CdS increases when the dipping time increases. The maximal conversion efficiency of 0.292% was achieved by the DSSCs based on CdS QDs-sensitized ZnO film obtained from 9 min-dipping time. Furthermore, the stability ofmore » DSSCs was improved by using polymeric electrolyte. Poly (acrylic acid) (PAA) and Polyacrylamide (PAM) were introduced to CdS QDs-sensitized ZnO film from 9 min-dipping time. Each polymeric electrolyte was prepared by swelling from 0.1-2.0 %w in H2O. The maximal conversion efficiency of 0.207% was achieved for DSSCs based on CdS QDs-sensitized ZnO film with PAM 1.0% and the conversion efficiency was decreased 25% when it was left for1 hr.« less

Thermo-optical characterization of cadmium selenide/zinc sulfide (CdSe/ZnS) quantum dots embedded in biocompatible materials.

PubMed

Pilla, Viviane; Alves, Leandro P; Iwazaki, Adalberto N; Andrade, Acácio A; Antunes, Andrea; Munin, Egberto

2013-09-01

Cadmium selenide/zinc sulfide (CdSe/ZnS) core-shell quantum dots (QDs) embedded in biocompatible materials were thermally and optically characterized with a thermal lens (TL) technique. Transient TL measurements were performed with a mode-mismatched, dual-beam (excitation and probe) configuration. A thermo-optical study of the CdSe/ZnS QDs was performed for different core diameters (3.5, 4.0, 5.2, and 6.6 nm) in aqueous solution and synthetic saliva, and three different core diameters (2.4, 2.9, and 4.1 nm) embedded in restorative dental resin (0.025% by mass). The thermal diffusivity results are characteristic of the biocompatible matrices. The radiative quantum efficiencies for aqueous solution and biofluid materials are dependent on the core size of the CdSe/ZnS core-shell QDs. The results obtained from the fluorescence spectral measurements for the biocompatible materials support the TL results.

An ultrasensitive SiO2-encapsulated alloyed CdZnSeS quantum dot-molecular beacon nanobiosensor for norovirus.

PubMed

Adegoke, Oluwasesan; Seo, Min-Woong; Kato, Tatsuya; Kawahito, Shoji; Park, Enoch Y

2016-12-15

Ultrasensitive, rapid and selective diagnostic probes are urgently needed to overcome the limitations of traditional probes for norovirus (NV). Here, we report the detection of NV genogroup II via nucleic acid hybridization technology using a quantum dot (QD)-conjugated molecular beacon (MB) probe. To boost the sensitivity of the MB assay system, an ultrasensitive QD fluorophore with unique optical properties was synthesized, characterized and exploited as a fluorescence signal generator. Alloyed thioglycolic (TGA)-capped CdZnSeS QDs with a high photoluminescence (PL) quantum yield (QY) value of 92% were synthesized, and a modified silanization method was employed to encapsulate the thiol-capped QDs in a silica layer. The resulting highly luminescent alloyed SiO2-coated CdZnSeS QDs had a remarkable PL QY value of 98%. Transmission electron microscopy and dynamic light scattering confirmed the monodispersity of the alloyed nanocrystals, and zeta potential analysis confirmed their colloidal stability. Powder X-ray diffraction and PL lifetime measurements confirmed the surface modification of the QDs. The alloyed TGA-capped and SiO2-coated CdZnSeS QD-conjugated MB bioprobes detected extremely low concentrations of NV RNA. Ultrasensitive detection of low concentrations of NV RNA with a limit of detection (LOD) of 8.2copies/mL in human serum and a LOD of 9.3 copies/mL in buffer was achieved using the SiO2-coated CdZnSeS QD-MB probes, an increase in sensitivity of 3-fold compared with the detection limit for NV RNA using TGA-capped CdZnSeS QD-MBs. The additional merits of our detection system are rapidity, specificity and improved sensitivity over conventional molecular test probes. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Analysis on nonlinear optical properties of Cd (Zn) Se quantum dots synthesized using three different stabilizing agents

NASA Astrophysics Data System (ADS)

J, Joy Sebastian Prakash; G, Vinitha; Ramachandran, Murugesan; Rajamanickam, Karunanithi

2017-10-01

Three different stabilizing agents, namely, L-cysteine, Thioglycolic acid and cysteamine hydrochloride were used to synthesize Cd(Zn)Se quantum dots (QDs). It was characterized using UV-vis spectroscopy, x-ray diffraction (XRD) and transmission electron microscopy (TEM). The non-linear optical properties (non-linear absorption and non-linear refraction) of synthesized Cd(Zn)Se quantum dots were studied with z-scan technique using diode pumped continuous wavelaser system at a wavelength of 532 nm. Our (organic) synthesized quantum dots showed optical properties similar to the inorganic materials reported elsewhere.

Tandem Solar Cells from Solution-Processed CdTe and PbS Quantum Dots Using a ZnTe-ZnO Tunnel Junction.

PubMed

Crisp, Ryan W; Pach, Gregory F; Kurley, J Matthew; France, Ryan M; Reese, Matthew O; Nanayakkara, Sanjini U; MacLeod, Bradley A; Talapin, Dmitri V; Beard, Matthew C; Luther, Joseph M

2017-02-08

We developed a monolithic CdTe-PbS tandem solar cell architecture in which both the CdTe and PbS absorber layers are solution-processed from nanocrystal inks. Due to their tunable nature, PbS quantum dots (QDs), with a controllable band gap between 0.4 and ∼1.6 eV, are a promising candidate for a bottom absorber layer in tandem photovoltaics. In the detailed balance limit, the ideal configuration of a CdTe (E g = 1.5 eV)-PbS tandem structure assumes infinite thickness of the absorber layers and requires the PbS band gap to be 0.75 eV to theoretically achieve a power conversion efficiency (PCE) of 45%. However, modeling shows that by allowing the thickness of the CdTe layer to vary, a tandem with efficiency over 40% is achievable using bottom cell band gaps ranging from 0.68 and 1.16 eV. In a first step toward developing this technology, we explore CdTe-PbS tandem devices by developing a ZnTe-ZnO tunnel junction, which appropriately combines the two subcells in series. We examine the basic characteristics of the solar cells as a function of layer thickness and bottom-cell band gap and demonstrate open-circuit voltages in excess of 1.1 V with matched short circuit current density of 10 mA/cm 2 in prototype devices.

Tandem Solar Cells from Solution-Processed CdTe and PbS Quantum Dots Using a ZnTe–ZnO Tunnel Junction

DOE PAGES

Crisp, Ryan W.; Pach, Gregory F.; Kurley, J. Matthew; ...

2017-01-10

Here, we developed a monolithic CdTe-PbS tandem solar cell architecture in which both the CdTe and PbS absorber layers are solution-processed from nanocrystal inks. Due to their tunable nature, PbS quantum dots (QDs), with a controllable band gap between 0.4 and ~1.6 eV, are a promising candidate for a bottom absorber layer in tandem photovoltaics. In the detailed balance limit, the ideal configuration of a CdTe (E g = 1.5 eV)-PbS tandem structure assumes infinite thickness of the absorber layers and requires the PbS band gap to be 0.75 eV to theoretically achieve a power conversion efficiency (PCE) of 45%.more » But, modeling shows that by allowing the thickness of the CdTe layer to vary, a tandem with efficiency over 40% is achievable using bottom cell band gaps ranging from 0.68 and 1.16 eV. In a first step toward developing this technology, we explore CdTe-PbS tandem devices by developing a ZnTe-ZnO tunnel junction, which appropriately combines the two subcells in series. Furthermore, we examine the basic characteristics of the solar cells as a function of layer thickness and bottom-cell band gap and demonstrate open-circuit voltages in excess of 1.1 V with matched short circuit current density of 10 mA/cm 2 in prototype devices.« less

Nanowire growth and sublimation: CdTe quantum dots in ZnTe nanowires

NASA Astrophysics Data System (ADS)

Orrù, M.; Robin, E.; Den Hertog, M.; Moratis, K.; Genuist, Y.; André, R.; Ferrand, D.; Cibert, J.; Bellet-Amalric, E.

2018-04-01

The role of the sublimation of the compound and of the evaporation of the constituents from the gold nanoparticle during the growth of semiconductor nanowires is exemplified with CdTe-ZnTe heterostructures. Operating close to the upper temperature limit strongly reduces the amount of Cd present in the gold nanoparticle and the density of adatoms on the nanowire sidewalls. As a result, the growth rate is small and strongly temperature dependent, but a good control of the growth conditions allows the incorporation of quantum dots in nanowires with sharp interfaces and adjustable shape, and it minimizes the radial growth and the subsequent formation of additional CdTe clusters on the nanowire sidewalls, as confirmed by photoluminescence. Uncapped CdTe segments dissolve into the gold nanoparticle when interrupting the flux, giving rise to a bulblike (pendant-droplet) shape attributed to the Kirkendall effect.

Systematic study of the elastic, optoelectronic, and thermoelectric behavior of MRh2O4 (M = Zn, Cd) based on first principles calculations

NASA Astrophysics Data System (ADS)

Abbas, Syed Adeel; Rashid, Muhammad; Faridi, Muhammad Ayub; Saddique, Muhammad Bilal; Mahmood, Asif; Ramay, Shahid Muhammad

2018-02-01

In the present study, we performed first principles total energy calculations to explore the electronic, elastic, optical, and thermoelectric behavior of MRh2O4(M = Zn, Cd) spinel oxides. We employed Perdew-Burke-Ernzerhof-sol as well as the modified Becke and Johnson potential to compute the elastic, optoelectronic, and thermoelectric behavior of MRh2O4(M = Zn, Cd). The optical behavior was investigated by calculating the complex dielectric constant, refractive index, optical reflectivity, absorption coefficient, and optical conductivity. All of the optical parameters indicated a shift to lower energies as the atomic size increased from Zn to Cd, thereby suggesting potential applications of the spinel oxides in optoelectronic device. Moreover, the thermoelectric properties of MRh2O4(M = Zn, Cd) spinel oxides were computed in terms of the electrical conductivity (σ), Seebeck coefficient (S), thermal conductivity (k), and power factor (σS2) using the BoltzTraP code.

Zn-Ge-Sb glass composite mixed with Ba2+ ions: a high capacity anode material for Na-ion batteries

NASA Astrophysics Data System (ADS)

Ravuri, Balaji Rao; Gandi, Suman; Chinta, Srinivasa Rao

2018-06-01

(100-x)(0.7[0.625ZnO-0.375GeO2]-0.3Sb2O3)-xBaO (x = 0, 2, 4 and 6 mol%, labeled as ZGSB x ) glass anode samples are synthesized using a high-energy ball-milling method and employed as anode material for Na-ion batteries. The results on microstructures (XRD, SEM) and electrochemical properties (constant current charge/discharge tests, CV and EIS) indicated that the optimum concentration of Ba2+ ions in the Zn-Ge-Sb glass anode network exhibits the pillaring effect, which would lead to increased electrical conductivity, minimize the volume changes, cracks and voids to boost up electrochemical performance. The ZGSB4 glass anode sample exhibits good capacity retention even after 20 cycles with 95% coulombic efficiency, which is a significant trend for a successful anode network. Electrochemical performance is considerably enhanced by reducing the cut-off voltage from 2 to 1.25 V due to the disassembly of amorphous intermediate domains, optimum volume changes and increased electrical conductivity in this ZGSB x glass network.

Electrokinetic enhancement on phytoremediation in Zn, Pb, Cu and Cd contaminated soil using potato plants.

PubMed

Aboughalma, Hanssan; Bi, Ran; Schlaak, Michael

2008-07-01

The use of a combination of electrokinetic remediation and phytoremediation to decontaminate soil polluted with heavy metals has been demonstrated in a laboratory-scale experiment. Potato tubers were planted in plastic vessels filled with Zn, Pb, Cu and Cd contaminated soil and grown in a greenhouse. Three of these vessels were treated with direct current electric field (DC), three with alternative current (AC) and three remained untreated as control vessels. The soil pH varied from anode to cathode with a minimum of pH 3 near the anode and a maximum of pH 8 near the cathode in the DC treated soil profile. There was an accumulation of Zn, Cu and Cd at about 12 cm distance from anode when soil pH was 5 in the DC treated soil profile. There was no significant metal redistribution and pH variation between anode and cathode in the AC soil profile. The biomass production of the plants was 72% higher under AC treatment and 27% lower under DC treatment compared to the control. Metal accumulation was generally higher in the plant roots treated with electrical fields than the control. The overall metal uptake in plant shoots was lower under DC treatment compared to AC treatment and control, although there was a higher accumulation of Zn and Cu in the plant roots treated with electrical fields. The Zn uptake in plant shoots under AC treatment was higher compared to the control and DC treatment. Zn and Cu accumulation in the plant roots under AC and DC treatment was similar, and both were higher comparing to control. Cd content in plant roots under all three treatments was found to be higher than that in the soil. The Pb accumulation in the roots and the uptake into the shoots was lower compared to its content in the soil.

Effect of luminescence transport through adipose tissue on measurement of tissue temperature by using ZnCdS nanothermometers

NASA Astrophysics Data System (ADS)

Volkova, Elena K.; Yanina, Irina Yu.; Sagaydachnaya, Elena; Konyukhova, Julia G.; Kochubey, Vyacheslav I.; Tuchin, Valery V.

2018-02-01

The spectra of luminescence of ZnCdS nanoparticles (ZnCdS NPs) were measured and analyzed in a wide temperature range: from room to human body and further to a hyperthermic temperature resulting in tissue morphology change. The results show that the signal of luminescence of ZnCdS NPs placed within the tissue is reasonably good sensitive to temperature change and accompanied by phase transitions of lipid structures of adipose tissue. It is shown that the presence of a phase transition in adipose tissue upon its heating (polymorphic transformations of lipids) leads to a nonmonotonic temperature dependence of the intensity of luminescence for the nanoparticles introduced into adipose tissue. This is due to a change in the light scattering by the tissue. The light scattering of adipose tissue greatly distorts the results of temperature measurements. The application of these nanoparticles is possible for temperature measurements in very thin or weakly scattering samples.

Voltage-Dependent Charge Storage in Cladded Zn0.56Cd0.44Se Quantum Dot MOS Capacitors for Multibit Memory Applications

NASA Astrophysics Data System (ADS)

Khan, J.; Lingalugari, M.; Al-Amoody, F.; Jain, F.

2013-11-01

As conventional memories approach scaling limitations, new storage methods must be utilized to increase Si yield and produce higher on-chip memory density. Use of II-VI Zn0.56Cd0.44Se quantum dots (QDs) is compatible with epitaxial gate insulators such as ZnS-ZnMgS. Voltage-dependent charging effects in cladded Zn0.56Cd0.44Se QDs are presented in a conventional metal-oxide-semiconductor capacitor structure. Charge storage capabilities in Si and ZnMgS QDs have been reported by various researchers; this work is focused on II-VI material Zn0.56Cd0.44Se QDs nucleated using photoassisted microwave plasma metalorganic chemical vapor deposition. Using capacitance-voltage hysteresis characterization, the multistep charging and discharging capabilities of the QDs at room temperature are presented. Three charging states are presented within a 10 V charging voltage range. These characteristics exemplify discrete charge states in the QD layer, perfect for multibit, QD-functionalized high-density memory applications. Multiple charge states with low operating voltage provide device characteristics that can be used for multibit storage by allowing varying charges to be stored in a QD layer based on the applied "write" voltage.

Phytoremediation potential of Cd and Zn by wetland plants, Colocasia esculenta L. Schott., Cyperus malaccensis Lam. and Typha angustifolia L. grown in hydroponics.

PubMed

Chayapan, P; Kruatrachue, M; Meetam, M; Pokethitiyook, P

2015-09-01

Cadmium and zinc phytoremediation potential of wetland plants, Colocasia esculenta, Cyperus malaccensis, and Typha angustifolia, was investigated. Plants were grown for 15 days in nutrient solutions containing various concentrations of Cd (0, 5, 10, 20, 50 mg l(-1)) and Zn (0, 10, 20, 50, 100 mg l(-1)). T angustifolia was tolerant to both metals as indicated by high RGR when grown in 50 mg I(-1) Cd and 100 mg I(-1) Zn solutions. All these plants accumulated more metals in their underground parts and > 100 mg kg(-1) in their aboveground with TF values < 1. Only C. esculenta could be considered a Zn hyperaccumulator because it could concentrate > 10,000 mg kg(-1) in its aboveground parts with TF > 1. T angustifolia exhibited highest biomass production and highest Cd and Zn uptake, confirming that this plant is a suitable candidate for treating of Cd contaminated soil/sediments.

Effect of hydrogenation on the electrical and optical properties of CdZnTe substrates and HgCdTe epitaxial layers

NASA Astrophysics Data System (ADS)

Sitharaman, S.; Raman, R.; Durai, L.; Pal, Surendra; Gautam, Madhukar; Nagpal, Anjana; Kumar, Shiv; Chatterjee, S. N.; Gupta, S. C.

2005-12-01

In this paper, we report the experimental observations on the effect of plasma hydrogenation in passivating intrinsic point defects, shallow/deep levels and extended defects in low-resistivity undoped CdZnTe crystals. The optical absorption studies show transmittance improvement in the below gap absorption spectrum. Using variable temperature Hall measurement technique, the shallow defect level on which the penetrating hydrogen makes complex, has been identified. In 'compensated' n-type HgCdTe epitaxial layers, hydrogenation can improve the resistivity by two orders of magnitude.

Distribution and evolution of Zn, Cd, and Pb in Apollo 16 regolith samples and the average U-Pb ages of the parent rocks

NASA Technical Reports Server (NTRS)

Cirlin, E. H.; Housley, R. M.

1982-01-01

The concentration of surface (low temperature site) and interior (high temperature site) Cd, Zn, and Pb in 13 Apollo 16 highland fines samples, pristine rock 65325, and mare fines sample 75081 were analyzed directly from the thermal release profiles obtained by flameless atomic absorption technique (FLAA). Cd and Zn in pristine ferroan anothosite 65325, anorthositic grains of the most mature fines 65701, and basaltic rock fragments of mare fines 75081 were almost all surface Cd and Zn indicating that most volatiles were deposited on the surfaces of vugs, vesicles and microcracks during the initial cooling process. A considerable amount of interior Cd and Zn was observed in agglutinates. This result suggests that high temperature site interior volatiles originate from entrapment during the lunar maturation processes. Interior Cd found in the most mature fines sample 65701 was only about 15% of the total Cd in the sample. Interior Pb present in Apollo 16 fines samples went up to 60%. From our Cd studies we can assume that this interior Pb in highland fines samples is largely due to the radiogenic decay which occurred after the redistribution of the volatiles took place. We obtained an average age of 4.0 b.y. for the parent rocks of Apollo 16 highland regolith from our interior Pb analyses.

Removal of Pb(II), Cd(II), Cu(II), and Zn(II) by hematite nanoparticles: effect of sorbent concentration, pH, temperature, and exhaustion.

PubMed

Shipley, Heather J; Engates, Karen E; Grover, Valerie A

2013-03-01

Nanoparticles offer the potential to improve environmental treatment technologies due to their unique properties. Adsorption of metal ions (Pb(II), Cd(II), Cu(II), Zn(II)) to nanohematite was examined as a function of sorbent concentration, pH, temperature, and exhaustion. Adsorption experiments were conducted with 0.05, 0.1, and 0.5 g/L nanoparticles in a pH 8 solution and in spiked San Antonio tap water. The adsorption data showed the ability of nanohematite to remove Pb, Cd, Cu, and Zn species from solution with adsorption increasing as the nanoparticle concentration increased. At 0.5 g/L nanohematite, 100 % Pb species adsorbed, 94 % Cd species adsorbed, 89 % Cu species adsorbed and 100 % Zn species adsorbed. Adsorption kinetics for all metals tested was described by a pseudo second-order rate equation with lead having the fastest rate of adsorption. The effect of temperature on adsorption showed that Pb(II), Cu(II), and Cd(II) underwent an endothermic reaction, while Zn(II) underwent an exothermic reaction. The nanoparticles were able to simultaneously remove multiple metals species (Zn, Cd, Pb, and Cu) from both a pH 8 solution and spiked San Antonio tap water. Exhaustion experiments showed that at pH 8, exhaustion did not occur for the nanoparticles but adsorption does decrease for Cd, Cu, and Zn species but not Pb species. The strong adsorption coupled with the ability to simultaneously remove multiple metal ions offers a potential remediation method for the removal of metals from water.

Characterization of CdTe and (CdZn)Te detectors with different metal contacts

NASA Astrophysics Data System (ADS)

Pekárek, J.; Belas, E.; Grill, R.; Uxa, Å.; James, R. B.

2013-09-01

In the present work we studied an influence of different types of surface etching and surface passivation of high resistivity CdZnTe-based semiconductor detector material. The aim was to find the optimal conditions to improve the properties of metal-semiconductor contact. The main effort was to reduce the leakage current and thus get better X-ray and gamma-ray spectrum, i.e. to create a detector operating at room temperature based on this semiconductor material with sufficient energy resolution and the maximum charge collection efficiency. Individual surface treatments were characterized by I-V characteristics, spectral analysis and by determination of the profile of the internal electric field.

[Effect of quantum dots CdSe/ZnS's concentration on its fluorescence].

PubMed

Jin, Min; Huang, Yu-hua; Luo, Ji-xiang

2015-02-01

The authors measured the absorption and the fluorescence spectra of the quantum dots CdSe/ZnS with 4 nm in size at different concentration with the use of the UV-Vis absorption spectroscopy and fluorescence spectrometer. The effect of quantum dots CdSe/ZnS's concentration on its fluorescence was especially studied and its physical mechanism was analyzed. It was observed that the optimal concentration of the quantum dots CdSe/ZnS for fluorescence is 2 micromole x L(-1). When the quantum dot's concentration is over 2 micromol x L(-1), the fluorescence is decreased with the increase in the concentration. While the quantum dot's concentration is less than 2 micromol x L(-1), the fluorescence is decreased with the decrease in the concentration. There are two main reasons: (1) fluorescence quenching and 2) the competition between absorption and fluorescence. When the quantum dot's concentration is over 2 micromol x L(-1), the distance between quantum dots is so close that the fluorescence quenching is induced. The closer the distance between quantum dots is, the more serious the fluorescence quenching is induced. Also, in this case, the absorption is so large that some of the quantum dots can not be excited because the incident light can not pass through the whole sample. As a result, the fluorescence is decreased with the increase in the quantum dot's concentration. As the quantum dot's concentration is below 2 micromol x L(-1), the distance between quantum dots is far enough that no more fluorescence quenching is induced. In this case, the fluorescence is determined by the particle number per unit volume. More particle number per unit volume produces more fluorescence. Therefore, the fluorescence is decreased with the decrease in the quantum dot's concentration.

Tuning the electronic hybridization in the heavy fermion cage compound YbFe2Zn20 with Cd doping

NASA Astrophysics Data System (ADS)

Cabrera-Baez, M.; Ribeiro, R. A.; Avila, M. A.

2016-09-01

The tuning of the electronic properties of heavy fermion compounds by chemical substitution provides excellent opportunities for further understanding the physics of hybridized ions in crystal lattices. Here we present an investigation on the effects of Cd doping in flux-grown single crystals of the complex intermetallic cage compound YbFe2Zn20, which has been described as a heavy fermion with a Sommerfeld coefficient of 535 mJ mol-1 · K-2. The substitution of Cd for Zn disturbs the system by expanding the unit cell and, in this case, the size of the Zn cages that surround the Yb and Fe. With an increasing amount of Cd, the hybridization between the Yb 4f electrons and the conduction electrons is weakened, as shown by a decrease in the Sommerfeld coefficient, which should be accompanied by a valence shift of the Yb3+ due to the negative chemical pressure effect. This scenario is also supported by the low temperature DC magnetic susceptibility, which is gradually suppressed and shows an increment of the Kondo temperature, based on a shift to higher temperatures of the characteristic broad susceptibility peak. Furthermore, the DC resistivity decreases with the isoelectronic substitution of Cd for Zn, contrary to expectations in an increasingly disordered system, and implying that the valence shift is not related to charge carrier doping. The combined results demonstrate the excellent complementarity between positive physical pressure and negative chemical pressure, and point to a rich playground for exploring the physics and chemistry of strongly correlated electron systems in the general family of Zn20 compounds, despite their structural complexity.

Numerical methods for industrial vertical Bridgman growth of (Cd,Zn)Te

NASA Astrophysics Data System (ADS)

Lin, K.; Boschert, S.; Dold, P.; Benz, K. W.; Kriessl, O.; Schmidt, A.; Siebert, K. G.; Dziuk, G.

2002-04-01

This paper presents efficient numerical methods—the "inverse modeling" method and the adaptive finite element method—for optimizing the heat transport as well as for investigating the heat and mass transport under the influence of convection during crystal growth, especially near the liquid/solid interface. These methods have been applied to industrial Bridgman-furnaces for the growth of 65-75 mm diameter (Cd,Zn)Te crystals.

Solid solution partitioning of Sr2+, Ba2+, and Cd2+ to calcite

USGS Publications Warehouse

Tesoriero, A.J.; Pankow, J.F.

1996-01-01

Although solid solutions play important roles in controlling the concentrations of minor metal ions in natural waters, uncertainties regarding their compositions, thermodynamics, and kinetics usually prevent them from being considered. A range of precipitation rates was used here to study the nonequilibrium and equilibrium partitioning behaviors of Sr2+, Ba2+, and Cd2+ to calcite (CaCO3(s)). The distribution coefficient of a divalent metal ion Me2+ for partitioning from an aqueous solution into calcite is given by DMe = (XMeCO3(s)/[Me2+])/(XCaCO3(s)/[Ca 2+]). The X values are solid-phase mole fractions; the bracketed values are the aqueous molal concentrations. In agreement with prior work, at intermediate to high precipitation rates R (nmol/mg-min), DSr, DBa, and DCd were found to depend strongly on R. At low R, the values of DSr, DBa, and DCd became constant with R. At 25??C, the equilibrium values for DSr, DBa, and DCd for dilute solid solutions were estimated to be 0.021 ?? 0.003, 0.012 ?? 0.005, and 1240 ?? 300, respectively. Calculations using these values were made to illustrate the likely importance of partitioning of these ions to calcite in groundwater systems. Due to its large equilibrium DMe value, movement of Cd2+ will be strongly retarded in aquifers containing calcite; Sr2+ and Ba2+ will not be retarded nearly as much.

Facile, one-pot and scalable synthesis of highly emissive aqueous-based Ag,Ni:ZnCdS/ZnS core/shell quantum dots with high chemical and optical stability

NASA Astrophysics Data System (ADS)

Sahraei, Reza; Soheyli, Ehsan; Faraji, Zahra; Soleiman-Beigi, Mohammad

2017-11-01

We report here on a one-pot, mild and low cost aqueous-based synthetic route for the preparation of colloidally stable and highly luminescent dual-doped Ag,Ni:ZnCdS/ZnS core/shell quantum dots (QDs). The pure dopant emission of the Ni-doped core/shell QDs was found to be highly affected by the presence of a second dopant ion (Ag+). Results showed that the PL emission intensity increases while its peak position experiences an obvious blue shift with an increase in the content of Ag+ ions. Regarding the optical observations, we provide a simple scheme for absorption-recombination processes of the carriers through impurity centers. To obtain optimum conditions with a better emission characteristic, we also study the effect of different reaction parameters, such as refluxing temperature, the pH of the core and shell solution, molar ratio of the dopant ions (Ni:(Zn+Cd) and Ag:(Zn+Cd)), and concentration of the core and shell precursors. Nonetheless, the most effective parameter is the presence of the ZnS shell in a suitable amount to eliminate surface trap states and enhance their emission intensity. It can also improve the bio-compatibility of the prepared QDs by restricting the Cd2+ toxic ions inside the core of the QDs. The present suggested route also revealed the remarkable optical and chemical stability of the colloidal QDs which establishes them as a decent kind of nano-scale structure for light emitting applications, especially in biological technologies. The suggested process also has the potential to be scaled-up while maintaining the emission characteristics and structural quality necessary for industrial applications in optoelectronic devices.

Effect of the cadmium chloride treatment on RF sputtered Cd{sub 0.6}Zn{sub 0.4}Te films for application in multijunction solar cells

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

Shimpi, Tushar M., E-mail: mechanical.tushar@gmail.com; Kephart, Jason M.; Swanson, Drew E.

Single phase Cd{sub 0.6}Zn{sub 0.4}Te (CdZnTe) films of 1 μm thickness were deposited by radio frequency planar magnetron sputter deposition on commercial soda lime glass samples coated with fluorine-doped tin oxide and cadmium sulphide (CdS). The stack was then treated with cadmium chloride (CdCl{sub 2}) at different temperatures using a constant treatment time. The effect of the CdCl{sub 2} treatment was studied using optical, materials, and electrical characterization of the samples and compared with the as-deposited CdZnTe film with the same stack configuration. The band gap deduced from Tauc plots on the as-deposited CdZnTe thin film was 1.72 eV. The depositedmore » film had good crystalline quality with a preferred orientation along the {111} plane. After the CdCl{sub 2} treatment, the absorption edge shifted toward longer wavelength region and new peaks corresponding to cadmium telluride (CdTe) emerged in the x-ray diffraction pattern. This suggested loss of zinc after the CdCl{sub 2} treatment. The cross sectional transmission electron microscope images of the sample treated at 400 °C and the energy dispersive elemental maps revealed the absence of chlorine along the grain boundaries of CdZnTe and residual CdTe. The presence of chlorine in the CdTe devices plays a vital role in drastically improving the device performance which was not observed in CdZnTe samples treated with CdCl{sub 2}. The loss of zinc from the surface and incomplete recrystallization of the grains together with the presence of high densities of stacking faults were observed. The surface images using scanning electron microscopy showed that the morphology of the grains changed from small spherical shape to large grains formed due to the fusion of small grains with distinct grain boundaries visible at the higher CdCl{sub 2} treatment temperatures. The absence of chlorine along the grain boundaries, incomplete recrystallization and distinct grain boundaries is understood to cause

ZnO Hierarchical Nanostructure Photoanode in a CdS Quantum Dot-Sensitized Solar Cell

PubMed Central

Liu, Huan; Zhang, Gengmin; Sun, Wentao; Shen, Ziyong; Shi, Mingji

2015-01-01

A hierarchical array of ZnO nanocones covered with ZnO nanospikes was hydrothermally fabricated and employed as the photoanode in a CdS quantum dot-sensitized solar cell (QDSSC). This QDSSC outperformed the QDSSC based on a simple ZnO nanocone photoanode in all the four principal photovoltaic parameters. Using the hierarchical photoanode dramatically increased the short circuit current density and also slightly raised the open circuit voltage and the fill factor. As a result, the conversion efficiency of the QDSSC based on the hierarchical photoanode was more than twice that of the QDSSC based on the simple ZnO nanocone photoanode. This improvement is attributable to both the enlarged specific area of the photoanode and the reduction in the recombination of the photoexcited electrons. PMID:26379268

Facile synthesis of mercaptosuccinic acid-capped CdTe/CdS/ZnS core/double shell quantum dots with improved cell viability on different cancer cells and normal cells

NASA Astrophysics Data System (ADS)

Parani, Sundararajan; Bupesh, Giridharan; Manikandan, Elayaperumal; Pandian, Kannaiyan; Oluwafemi, Oluwatobi Samuel

2016-11-01

Water-soluble, mercaptosuccinic acid (MSA)-capped CdTe/CdS/ZnS core/double shell quantum dots (QDs) were prepared by successive growth of CdS and ZnS shells on the as-synthesized CdTe/CdSthin core/shell quantum dots. The formation of core/double shell structured QDs was investigated by ultraviolet-visible (UV-Vis) absorption and photoluminescence (PL) spectroscopy, PL decay studies, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The core/double shell QDs exhibited good photoluminescence quantum yield (PLQY) which is 70% higher than that of the parent core/shell QDs, and they are stable for months. The average particle size of the core/double shell QDs was ˜3 nm as calculated from the transmission electron microscope (TEM) images. The cytotoxicity of the QDs was evaluated on a variety of cancer cells such as HeLa, MCF-7, A549, and normal Vero cells by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) cell viability assay. The results showed that core/double shell QDs were less toxic to the cells when compared to the parent core/shell QDs. MCF-7 cells showed proliferation on incubation with QDs, and this is attributed to the metalloestrogenic activity of cadmium ions released from QDs. The core/double shell CdTe/CdS/ZnS (CSS) QDs were conjugated with transferrin and successfully employed for the biolabeling and fluorescent imaging of HeLa cells. These core/double shell QDs are highly promising fluorescent probe for cancer cell labeling and imaging applications.

Zn influence on the plasticity of Cdo{0.96}Zn{0.04}Te

NASA Astrophysics Data System (ADS)

Imhoff, D.; Zozime, A.; Triboulet, R.

1991-11-01

Compression tests were performed on CdTe and Cd{0.96}Zn{0.04}Te to elucidate the mechanism through which Zn inhibits dislocation formation and motion during CdTe crystal growth, thus leading to a decreasing of the dislocation density. Uniaxial deformation experiments performed with CdTe and CdZnTe at constant strain rate within a wide temperature range (0. 14;T_m le T le 0.87;T_m,;T_m = 1 365; K), have revealed a strong hardening effect of Zn within the whole temperature range. They also showed in CdZnTe a Portevin Le Chatelier effect between 770 K and 920 K confirmed by static strain aging experiments. Critical resolved shear stress (C.R.S.S.) values at T = 195; K and static strain aging results with CdZnTe point to size effect as the dominant interaction between Zn and dislocations. Thermal activation parameters were estimated in both materials. La déformation plastique a été utilisée comme approche des mécanismes par lesquels le zinc entrave le mouvement des dislocations au cours du processus de croissance cristalline de CdTe massif, réduisant ainsi la densité de dislocations. Les expériences de compression uniaxiale à vitesse constante, réalisées dans CdTe et CdZnTe entre 0,14 T_f et 0,87 T_f ont montré que le zinc est responsable d'un fort durcissement sur tout le domaine de températures étudié. Les expériences de déformation dans CdZnTe ont mis en évidence un phénomène du type Portevin Le Chatelier entre 770 K et 920 K, confirmé par des expériences de vieillissement statique. Les valeurs de scission critique tau_c à 195 K et les résultats des expériences de vieillissement statique dans CdZnTe sont compatibles avec un effet de taille dominant pour les interactions Zndislocations. Les paramètres d'activation thermique ont été estimés dans les deux matériaux.

Concentration and emission sources of airborne metals in particulate matter in the industrial district of Médio Paraíba, state of Rio de Janeiro, Brazil.

PubMed

Loyola, Josiane; de Almeida, Pierre Batista; Quiterio, Simone Lorena; Sousa, Célia Regina; Arbilla, Graciela; Escaleira, Viviane; de Carvalho, Maria Isabel; dos Santos Amaral Gomes da Silva, Alzira

2006-11-01

Total suspended particles and 12 airborne metals were determined in 4 sampling sites in the industrial region of Médio Paraíba, Brazil. The geometrical means for the four sampling locals were (in units of microg/m3): 65.9 in Barra Mansa, 57.3 in Jardim Paraíba (Volta Redonda), 41.7 in Resende, and 48.9 in Volta Grande (Volta Redonda). These values are lower than levels previously determined in urban and industrial locals of the Metropolitan Area of Rio de Janeiro. For metals, the higher concentrations were obtained for Ca, Zn, Al, Fe, and Mg. Ca, Zn, and Al levels are higher than those determined in other industrial areas. These three metals are used in steel manufacturing, the main economical activity of the region. Enrichment factors for Zn, Cu, Cd, and Pb are higher than 10, suggesting an industrial input. Statistical analysis show a high correlation among Ca, Mg, Zn, Cr, Al, Mn, and Fe, all of them used as raw materials in steel manufacturing and/or accumulated as industrial blast furnace slag and steelworks slag.

Sediment pollution in margins of the Lake Guaíba, Southern Brazil.

PubMed

de Andrade, Leonardo Capeleto; Tiecher, Tales; de Oliveira, Jessica Souza; Andreazza, Robson; Inda, Alberto Vasconcellos; de Oliveira Camargo, Flávio Anastácio

2017-12-02

Sediments are formed by deposition of organic and inorganic particles on depth of water bodies, being an important role in aquatic ecosystems, including destination and potential source of essential nutrients and heavy metals, which may be toxic for living organisms. The Lake Guaíba supplies water for approximately two million people and it is located in the metropolitan region of Porto Alegre, Rio Grande do Sul State, Brazil. Thus, the aim of this study was to evaluate the sediment pollution in the margins of Lake Guaíba in the vicinity of Porto Alegre city. Surface sediment was sampled in 12 sites to assess the concentration of several elements (C, N, P, Fe, Al, Ca, Mg, Na, K, Mn, Ba, Zn, V, Pb, Cu, Cr, Ni, Cd, Mo, and Se) and the mineralogical composition. Sediment in margins of Lake Guaíba presented predominantly (> 95%) sandy fraction in all samples, but with significant differences between evaluated sites. Sediments in the margins of Lake Guaíba showed indications of punctual water pollution with Pb, Cu, Cr, Ni, TOC, TKN, and P, mainly derived from urban streams that flow into the lake. In order to solve these environmental liabilities, public actions should not focus only on Guaíba, but also in the streams that flow into the lake.

Pulse shaping system research of CdZnTe radiation detector for high energy x-ray diagnostic

NASA Astrophysics Data System (ADS)

Li, Miao; Zhao, Mingkun; Ding, Keyu; Zhou, Shousen; Zhou, Benjie

2018-02-01

As one of the typical wide band-gap semiconductor materials, the CdZnTe material has high detection efficiency and excellent energy resolution for the hard X-ray and the Gamma ray. The generated signal of the CdZnTe detector needs to be transformed to the pseudo-Gaussian pulse with a small impulse-width to remove noise and improve the energy resolution by the following nuclear spectrometry data acquisition system. In this paper, the multi-stage pseudo-Gaussian shaping-filter has been investigated based on the nuclear electronic principle. The optimized circuit parameters were also obtained based on the analysis of the characteristics of the pseudo-Gaussian shaping-filter in our following simulations. Based on the simulation results, the falling-time of the output pulse was decreased and faster response time can be obtained with decreasing shaping-time τs-k. And the undershoot was also removed when the ratio of input resistors was set to 1 to 2.5. Moreover, a two stage sallen-key Gaussian shaping-filter was designed and fabricated by using a low-noise voltage feedback operation amplifier LMH6628. A detection experiment platform had been built by using the precise pulse generator CAKE831 as the imitated radiation pulse which was equivalent signal of the semiconductor CdZnTe detector. Experiment results show that the output pulse of the two stage pseudo-Gaussian shaping filter has minimum 200ns pulse width (FWHM), and the output pulse of each stage was well consistent with the simulation results. Based on the performance in our experiment, this multi-stage pseudo-Gaussian shaping-filter can reduce the event-lost caused by pile-up in the CdZnTe semiconductor detector and improve the energy resolution effectively.

Growth and characterization of metal doped and quasi mixed crystals based on ZnCd(SCN)4

NASA Astrophysics Data System (ADS)

Latha, C.; Mahadevan, C. K.; Guo, Li; Liu, Jinghe

2018-03-01

In order to understand the effect of forming hybrid crystals by doping with metallic impurities or by quasi mixing on the physicochemical properties of the basic material crystal, we have grown by the free evaporation method at room temperature and characterized (chemically, structurally, optically and electrically) un-doped and K+/Ca2+/Mn2+/Mg2+/Cu2+ doped (with 1 mol% concentration) ZnCd(SCN)4 and ZnxCd(2-x)(SCN)4 (with x = 0.0, 0.4, 0.8, 1.2, 1.6 and 2.0) single crystals. Single crystals could be grown with x = 0.0 (leading to Cd(SCN)2) but not when x = 2.0 (leading to Zn(SCN)2). Results obtained in the present study through X-ray diffraction and EDAX spectral measurements indicate the formation of the above hybrid crystals. The optical (UV-Vis-NIR spectral and SHG efficiency) measurements indicate significant changes in optical transmittance and SHG efficiency due to doping as well as quasi mixing. Dielectric measurements made in the temperature range 40-150 °C with a fixed frequency of 1 kHz indicate a normal dielectric behavior for all the eleven crystals grown. Moreover, the present study indicates an increase of dielectric constant and SHG efficiency when ZnCd(SCN)4 crystal is doped with a metallic impurity whereas a decrease of dielectric constant and SHG efficiency when quasi mixing is done.

Influence of infrared stimulation on spectroscopy characteristics of co-planar grid CdZnTe detectors

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

Fjodorov, V.; Ivanov, V.; Loutchanski, A.

It was previously found that illumination with monochromatic infrared (IR) light with wavelengths close to the absorption edge of the CdZnTe exert significant positive influence on the spectrometric characteristics of quasi-hemispherical CdZnTe detectors at room temperature. In this paper, preliminary results of IR stimulation on the spectrometric characteristics of coplanar-grid CdZnTe detectors as well as results of further studies of planar and quasi-hemispherical detectors are presented. Coplanar-grid detectors of 10 mm x 10 mm x 10 mm from Redlen Technologies and commercial available IR LEDs with different wavelengths of 800-1000 nm were used in the experiments. Influence of intensity andmore » direction of IR illumination on the detector's characteristics was studied. Analysis of signals shapes from the preamplifiers outputs at registration of alpha particles showed that IR illumination leads to a change in the shapes of these signals. This may indicate changes in electric fields distributions. An improvement in energy resolution at gamma-energy of 662 keV was observed with quasi-hemispherical and co-planar detectors at the certain levels of IR illumination intensity. The most noticeable effect of IR stimulation was observed with quasi-hemispherical detectors. It is due with optimization of charge collection conditions in the quasi-hemispherical detectors under IT stimulation. (authors)« less

Analysis of Te and TeO 2 on CdZnTe Nuclear Detectors Treated with Hydrogen Bromide and Ammonium-Based Solutions

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

Drabo, Mebougna L.; Egarievwe, Stephen U.; Okwechime, Ifechukwude O.

Surface defects caused during cutting and polishing in the fabrication of cadmium zinc telluride (CdZnTe) nuclear detectors limit their spectral performance. Chemical treatments are often used to remove surface damages and defects. In this paper, we present the analysis of Te and TeO 2 species on the surfaces of CdZnTe nuclear detectors treated with hydrogen bromide and ammonium-based solutions. The CdZnTe wafers were chemo-mechanically polished in a mixture of hydrogen bromide in hydrogen peroxide and ethylene glycol, followed by a chemical passivation in a mixture of ammonium fluoride and hydrogen peroxide solution. X-ray photoelectron spectroscopy showed significant conversion of Temore » to TeO 2, thus producing a more chemically stable surface. The resistivity of the CdZnTe samples is in the order of 1010 ohms-cm. The current for a given applied voltage increased following the passivation and decreased after a 3-hour period. Results from spectral response measurements showed that the 59.5-keV gamma-peak of Am-241 was stable under the same channel for the surface treatment processes.« less

Analysis of Te and TeO 2 on CdZnTe Nuclear Detectors Treated with Hydrogen Bromide and Ammonium-Based Solutions

DOE PAGES

Drabo, Mebougna L.; Egarievwe, Stephen U.; Okwechime, Ifechukwude O.; ...

2017-04-30

Surface defects caused during cutting and polishing in the fabrication of cadmium zinc telluride (CdZnTe) nuclear detectors limit their spectral performance. Chemical treatments are often used to remove surface damages and defects. In this paper, we present the analysis of Te and TeO 2 species on the surfaces of CdZnTe nuclear detectors treated with hydrogen bromide and ammonium-based solutions. The CdZnTe wafers were chemo-mechanically polished in a mixture of hydrogen bromide in hydrogen peroxide and ethylene glycol, followed by a chemical passivation in a mixture of ammonium fluoride and hydrogen peroxide solution. X-ray photoelectron spectroscopy showed significant conversion of Temore » to TeO 2, thus producing a more chemically stable surface. The resistivity of the CdZnTe samples is in the order of 1010 ohms-cm. The current for a given applied voltage increased following the passivation and decreased after a 3-hour period. Results from spectral response measurements showed that the 59.5-keV gamma-peak of Am-241 was stable under the same channel for the surface treatment processes.« less

Low-Cost Lattice Matching Zn(Se)Te/Si Composite Substrates for HgCdSe and Type-2 Superlattices

DTIC Science & Technology

2013-09-01

far from optimized. In similar fashion, we studied the impact of Zn/Te flux ratio during ZnTe growth. In this case , three ZnTe(100) layers were...6.1 Å, such as HgCdSe and GaSb-based type-II strained-layer superlattices. In this report, we present our findings on the systematic studies of...versus lattice parameter for several semiconductor material systems. We conducted systematic studies on the MBE growth of ZnTe on Si in both (211) and

A new fluorescent probe for distinguishing Zn2+ and Cd2+ with high sensitivity and selectivity.

PubMed

Tan, Yiqun; Gao, Junkuo; Yu, Jiancan; Wang, Ziqi; Cui, Yuanjing; Yang, Yu; Qian, Guodong

2013-08-28

A new fluorescence probe for distinguishing Zn(2+) and Cd(2+) is designed and synthesized. For the first time to our knowledge, this probe can recognize similar metal ions by coherently utilizing intramolecular charge transfer (ICT) and different electronic affinities of various metal ions, instead of by selective coordination alone, which may be interfered with and lose its selectivity easily in a complicated environment, providing a distinct recognition even by the naked eye for Zn(2+) and Cd(2+) with the sensitivity at the ppb level. This design strategy may initiate a straightforward approach for the selective detection of various metal ions with similar chemical properties in extensive applications such as environmental, industrial, and bio-science.

Colloidal synthesis of monodispersed ZnS and CdS nanocrystals from novel zinc and cadmium complexes

NASA Astrophysics Data System (ADS)

Onwudiwe, Damian C.; Mohammed, Aliyu D.; Strydom, Christien A.; Young, Desmond A.; Jordaan, Anine

2014-06-01

Monodispersed spherical and hexagonal shaped ZnS and CdS nanocrystals respectively, have been synthesized using novel heteroleptic complexes of xanthate (S2CObu) and dithiocarbamate (S2CNMePh). The nanocrystals were prepared via colloidal route and stabilized in hexadecylamine (HDA). The morphology of the as-prepared nanocrystals was characterized using transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), and powdered X-ray diffraction (p-XRD) analysis. An average diameter of 7.2 nm and 8.6 nm were obtained for the ZnS and CdS respectively. The optical properties of the nanoparticles studied by UV-vis and photoluminescence (PL) spectroscopy showed a blue shift in the absorption spectra, and band edge emission respectively.

Effect of adherent bacteria and bacterial extracellular polymers upon assimilation by Macoma balthica of sediment-bound Cd, Zn and Ag

USGS Publications Warehouse

Harvey, Ronald W.; Luoma, Samuel N.

1985-01-01

Effects of adherent bacteria and bacterial extracellular polymer (exopolymer) upon uptake of particle-bound Cd, Zn and Ag by the deposit-feeding clam Macoma balthica were studied in the laboratory. Amorphous iron oxyhydroxide and unaltered and alkaline-extracted sediments were used as model particulates in separate, controlled deposit-feeding experiments. In general, amounts of metal taken up from ingested particles varied dramatically with the nature of the particle surface. Ingestion of contaminated iron oxide particles did not contribute to overall uptake of Cd and Ag in feeding clams, but accounted for 89 to 99% of total Zn uptake. Exopolymer adsorbed on iron oxide particles caused an increase in the biological availability of particle-bound metals in the order Ag>Cd>Zn, whereas adherent bacteria up to 3.2 X 1011 g-1 had no effect upon amounts of metal taken up from ingested particulates. At the higher Cd and Ag concentrations employed (3.6 X 10-7M), feeding rates declined with increasing amounts of iron oxide-bound exopolymer, suggesting behavioral avoidance due to increased metal availability. Much of the Cd (57 %) taken up by clams feeding on unaltered estuarine sediments originated from particulates, even though particle/solute distribution of Cd (86%) was similar to that in experiments with iron oxide particles. Uptake of Cd from alkalineextracted sediments was insignificant, as it was from unamended iron oxide. However, addition of exopolymer (10 mgg-1 sediment) caused a restoration nn bioavailability of sediment-bound Cd.

Pressure-induced increase of exciton-LO-phonon coupling in a ZnCdSe/ZnSe quantum well

NASA Astrophysics Data System (ADS)

Guo, Z. Z.; Liang, X. X.; Ban, S. L.

2003-07-01

The possibility of pressure-induced increase of exciton-LO-phonon coupling in ZnCdSe/ZnSe quantum wells is studied. The ground state binding energies of the heavy hole excitons are calculated using a variational method with consideration of the electron-phonon interaction and the pressure dependence of the parameters. The results show that for quantum wells with intermediate well width, the exciton binding energy and the LO-phonon energy may coincide in the course of pressure increasing, resulting in the increase of exciton-LO-phonon coupling. It is also found that among the pressure-dependent parameters, the influence of the lattice constant is the most important one. The changes of both the effective masses and the dielectric constants have obvious effects on the exciton binding energy, but their influences are counterbalanced.

Removal of Zn or Cd and cyanide from cyanide electroplating wastes

DOEpatents

Moore, Fletcher L.

1977-05-31

A method is described for the efficient stripping of stable complexes of a selected quaternary amine and a cyanide of Zn or Cd. An alkali metal hydroxide solution such as NaOH or KOH will quantitatively strip a pregnant extract of the quaternary ammonium complex of its metal and cyanide content and regenerate a quaternary ammonium hydroxide salt which can be used for extracting further metal cyanide values.

Investigation of the limitations of the highly pixilated CdZnTe detector for PET applications

PubMed Central

Komarov, Sergey; Yin, Yongzhi; Wu, Heyu; Wen, Jie; Krawczynski, Henric; Meng, Ling-Jian; Tai, Yuan-Chuan

2016-01-01

We are investigating the feasibility of a high resolution positron emission tomography (PET) insert device based on the CdZnTe detector with 350 μm anode pixel pitch to be integrated into a conventional animal PET scanner to improve its image resolution. In this paper, we have used a simplified version of the multi pixel CdZnTe planar detector, 5 mm thick with 9 anode pixels only. This simplified 9 anode pixel structure makes it possible to carry out experiments without a complete application-specific integrated circuits readout system that is still under development. Special attention was paid to the double pixel (or charge sharing) detections. The following characteristics were obtained in experiment: energy resolution full-width-at-half-maximum (FWHM) is 7% for single pixel and 9% for double pixel photoelectric detections of 511 keV gammas; timing resolution (FWHM) from the anode signals is 30 ns for single pixel and 35 ns for double pixel detections (for photoelectric interactions only the corresponding values are 20 and 25 ns); position resolution is 350 μm in x,y-plane and ~0.4 mm in depth-of-interaction. The experimental measurements were accompanied by Monte Carlo (MC) simulations to find a limitation imposed by spatial charge distribution. Results from MC simulations suggest the limitation of the intrinsic spatial resolution of the CdZnTe detector for 511 keV photoelectric interactions is 170 μm. The interpixel interpolation cannot recover the resolution beyond the limit mentioned above for photoelectric interactions. However, it is possible to achieve higher spatial resolution using interpolation for Compton scattered events. Energy and timing resolution of the proposed 350 μm anode pixel pitch detector is no better than 0.6% FWHM at 511 keV, and 2 ns FWHM, respectively. These MC results should be used as a guide to understand the performance limits of the pixelated CdZnTe detector due to the underlying detection processes, with the understanding of

Investigation of the limitations of the highly pixilated CdZnTe detector for PET applications.

PubMed

Komarov, Sergey; Yin, Yongzhi; Wu, Heyu; Wen, Jie; Krawczynski, Henric; Meng, Ling-Jian; Tai, Yuan-Chuan

2012-11-21

We are investigating the feasibility of a high resolution positron emission tomography (PET) insert device based on the CdZnTe detector with 350 µm anode pixel pitch to be integrated into a conventional animal PET scanner to improve its image resolution. In this paper, we have used a simplified version of the multi pixel CdZnTe planar detector, 5 mm thick with 9 anode pixels only. This simplified 9 anode pixel structure makes it possible to carry out experiments without a complete application-specific integrated circuits readout system that is still under development. Special attention was paid to the double pixel (or charge sharing) detections. The following characteristics were obtained in experiment: energy resolution full-width-at-half-maximum (FWHM) is 7% for single pixel and 9% for double pixel photoelectric detections of 511 keV gammas; timing resolution (FWHM) from the anode signals is 30 ns for single pixel and 35 ns for double pixel detections (for photoelectric interactions only the corresponding values are 20 and 25 ns); position resolution is 350 µm in x,y-plane and ∼0.4 mm in depth-of-interaction. The experimental measurements were accompanied by Monte Carlo (MC) simulations to find a limitation imposed by spatial charge distribution. Results from MC simulations suggest the limitation of the intrinsic spatial resolution of the CdZnTe detector for 511 keV photoelectric interactions is 170 µm. The interpixel interpolation cannot recover the resolution beyond the limit mentioned above for photoelectric interactions. However, it is possible to achieve higher spatial resolution using interpolation for Compton scattered events. Energy and timing resolution of the proposed 350 µm anode pixel pitch detector is no better than 0.6% FWHM at 511 keV, and 2 ns FWHM, respectively. These MC results should be used as a guide to understand the performance limits of the pixelated CdZnTe detector due to the underlying detection processes, with the understanding of

Detection of pathogens using luminescent CdSe/ZnS dendron nanocrystals and a porous membrane immunofilter.

PubMed

Liu, Yongcheng; Brandon, Robert; Cate, Michael; Peng, Xiaogang; Stony, Robert; Johnson, Michael

2007-11-15

A biosensor system for detection of pathogens was developed by using CdSe/ZnS core/shell dendron nanocrystals with high efficiency and stability as fluorescence labels and a flowing chamber with a microporous immunofilter. The antibody-immobilized immunofilter captured the targeted pathogens, Escherichia coli O157:H7 as an example for bacteria and hepatitis B being a model system for viruses. The CdSe/ZnS core/shell dendron nanocrystals were conjugated with the corresponding antibodies and then passed through the microporous membrane where they attached to the membrane-antigen-antibody. The efficient and stable photoluminescence (PL) of the CdSe/ZnS nanocrystals on the formed "sandwich" structure complexes (membrane-antigen-antibody conjugated with the nanocrystals) was used as the detection means. The effects of the pore size of the membranes, buffer pH, and assay time on the detection of E. coli O157:H7 were investigated and optimized. The detectable level of this new system was as low as 2.3 CFU/mL for E. coli O157:H7 and 5 ng/mL for hepatitis B surface Ag (HBsAg). The assay time was shortened to 30 min without any enrichment and incubation.

Complex toxic effects of Cd2+, Zn2+, and acid rain on growth of kidney bean (Phaseolus vulgaris L).

PubMed

Liao, Bo-han; Liu, Hong-yu; Zeng, Qing-ru; Yu, Ping-zhong; Probst, Anne; Probst, Jean-Luc

2005-08-01

Complex toxic effects of Cd2+, Zn2+, and acid rain on growth of kidney bean (Phaseolus vulgaris L) were studied in a pot experiment by measurement of fresh weights of the plants, determination of surperoxide dismutase (SOD), peroxidase (POD), and lipid peroxidation (MDA) in the plant organs, and observation of injury symptoms. The experimental results demonstrated that all treatments of Cd2+, Zn2+, and/or acid rain significantly decreased fresh weights of kidney bean and caused toxic effects on growth of the plants, especially higher amounts of Cd2+ and Zn2+ and higher acidity of acid rain. Combination of these three pollutant factors resulted in more serious toxic effects than any single pollutant and than combinations of any two pollutants. SOD, POD, and MDA in the plant organs changed with different pollution levels, but MDA content in the leaves showed the best relationship between the pollution levels and toxic effects.

Prospective application of Leucaena leucocephala for phytoextraction of Cd and Zn and nitrogen fixation in metal polluted soils.

PubMed

Saraswat, Shweta; Rai, J P N

2011-03-01

The study deals with phytoextraction of Zn and Cd by Leucaena leucocephala grown on effluent fed and low nitrogen soils collected from S1, S2, and S3 sites, representing decreasing metal content with increasing distance from the effluent drain. Plant nitrogen fixation potential and soil micro-biochemical attributes against metal stress were also assessed. Increasing soil metal content and plant growth enhanced metal accumulation. Relatively greater amount of Zn than Cd was accumulated by L. leucocephala, which exceeded in roots with that of other parts. Remediation factor for Cd was maximum (3.6%) in S2 grown plant. Nodule numbers, their biomass, nitrogenase activity, and leghaemoglobin content were maximum in plants grown in S3 and minimum in S1 soil having maximum metals. Maximum soil organic C, total N, C(mic), and N(mic), respiration rate, ATP content, and enzymatic activities in response to phytoremediation was recorded in S3 followed by S2 and S1. Phytoremediation for a year enhanced extractable Zn and Cd by 36% and 45%, and their total removal by 20% and 30%, respectively from S2, which suggests the possible application of L. leucocephala for the remediation of metal contaminated sites and their fertility restoration by improving microbial functionalities and N-pool.

Atomistic simulations of the optical absorption of type-II CdSe/ZnTe superlattices

PubMed Central

2012-01-01

We perform accurate tight binding simulations to design type-II short-period CdSe/ZnTe superlattices suited for photovoltaic applications. Absorption calculations demonstrate a very good agreement with optical results with threshold strongly depending on the chemical species near interfaces. PMID:23031315

Metal (Cu, Cd and Zn) removal and stabilization during multiple soil washing by saponin.

PubMed

Gusiatin, Zygmunt Mariusz; Klimiuk, Ewa

2012-01-01

The influence of multiple saponin washing on copper, cadmium and zinc removal and stability in three types of soils (loamy sand, loam, silty clay) was investigated. Distribution of metals and their mobility measured as the ratio of exchangeable form to the sum of all fractions in soils was differential. After single washing the highest efficiency of metal removal was obtained in loamy sand (82-90%) and loam (67-88%), whereas the lowest in silty clay (39-62%). In loamy sand and loam metals had higher mobility factors (44-61% Cu, 60-76% Cd, and 68-84% Zn) compared to silty clay (9% Cu, 28% Cd and 36% Zn). Triplicate washing led to increase both efficiency of metal removal and percentage content of their stable forms. In consequence, fractional patterns for metals before and after treatment changed visibly as a result of their redistribution. Based on the redistribution index, the most stable metal (mainly in residual and organic fractions) after triplicate washing was Cu in loamy sand and loam. For silty clay contaminated with Cd, effective metal removal and its stabilization required a higher number of washings. Copyright © 2011 Elsevier Ltd. All rights reserved.

Solvo-thermal synthesis of a unique alkaline earth-transition Ba-Cd micro-porous coordination framework as hetero-metallic luminescent sensor for Cu2+ and real-time detection of benzaldehyde

NASA Astrophysics Data System (ADS)

Ding, Bin; Ma, Dian Xue; Zhang, Hui Min; Meng, Xin; Qiu, Rong Rong; Ren, Rong; Wu, Jie; Wu, Xiang Xia; Huo, Jian Zhong; Liu, Yuan Yuan; Shi, Xue Fang

2018-06-01

In this work a unique hetero-metallic alkaline earth-transition Ba-Cd luminescent micro-porous metal-organic framework {[BaCd(μ6-tp)1.5(μ2-Cl)(H2O) (DMF)2]·0.75H2O}n (H2tp = terephthalic acid) (1) has been prepared under solvo-thermal conditions. In 1 infinite 1D {Ba-X-Cd} (X = O, Cl) inorganic chains are linked via these full de-pronated tp2- ligands forming a unique 3D I1O2 type micro-porous coordination framework. PXRD patterns of 1 have been determined confirming pure phases of 1. Luminescence investigations suggested that 1 exhibits highly selective and sensitive sensing for trace amounts of benzaldehyde in ethanol, which provides a facile method for real-time detection of benzaldehyde. Meanwhile 1 also exhibits highly selective and sensitive sensing for Cu2+ over other cations with high quenching efficiency Ksv value 1.15 × 104 L·mol-1. As far as we know, 1 represents the first example of alkaline earth-transition hetero-metallic Ba-Cd micro-porous coordination framework as bi-functional luminescent probes for Cu2+ and benzaldehyde.

Assessing metal contamination from construction and demolition (C&D) waste used to infill wetlands: using Deroceras reticulatum (Mollusca: Gastropoda).

PubMed

Staunton, John A; Mc Donnell, Rory J; Gormally, Michael J; Williams, Chris D; Henry, Tiernan; Morrison, Liam

2014-11-01

Large quantities of construction and demolition waste (C&D) are produced globally every year, with little known about potential environmental impacts. In the present study, the slug, Deroceras reticulatum (Mollusca: Gastropoda) was used as the first biomonitor of metals (Ag, As, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Sb, Se, Ti, Tl, V and Zn) on wetlands post infilling with construction and demolition (C&D) waste. The bioaccumulation of As, Ba, Cd, Co, Sb, Se and Tl were found to be significantly elevated in slugs collected on C&D waste when compared to unimproved pastures (control sites), while Mo, Se and Sr had significantly higher concentrations in slugs collected on C&D waste when compared to known contaminated sites (mining locations), indicating the potential hazardous nature of C&D waste to biota. Identifying exact sources for these metals within the waste can be problematic, due to its heterogenic nature. Biomonitors are a useful tool for future monitoring and impact studies, facilitating policy makers and regulations in other countries regarding C&D waste infill. In addition, improving separation of C&D waste to allow increased reuse and recycling is likely to be effective in reducing the volume of waste being used as infill, subsequently decreasing potential metal contamination.

Ability of the marine bacterium Pseudomonas fluorescens BA3SM1 to counteract the toxicity of CdSe nanoparticles.

PubMed

Poirier, Isabelle; Kuhn, Lauriane; Demortière, Arnaud; Mirvaux, Boris; Hammann, Philippe; Chicher, Johana; Caplat, Christelle; Pallud, Marie; Bertrand, Martine

2016-10-04

In the marine environment, bacteria from estuarine and coastal sediments are among the first targets of nanoparticle pollution; it is therefore relevant to improve the knowledge of interactions between bacteria and nanoparticles. In this work, the response of the marine bacterium Pseudomonas fluorescens BA3SM1 to CdSe nanocrystals (CdSe NPs) of 3nm (NP3) and 8nm (NP8) in diameter was evaluated through microscopic, physiological, biochemical and proteomic approaches. Transmission electron microscopy images showed that NP3 were able to penetrate the bacteria, while NP8 were highly concentrated around the cells, embedded in large exopolysaccharides. In our experimental conditions, both CdSe NP sizes induced a decrease in respiration during the stationary growth phase, while only NP8 caused growth retardation and a decrease in pyoverdine production. Proteomic analyses highlighted that the strain responded to CdSe NP toxicity by inducing various defence mechanisms such as cell aggregation, extracellular CdSe NP sequestration, effective protection against oxidative stress, modifications of envelope organization and properties, and cadmium export. In addition, BA3SM1 presented a biosorption capacity of 1.6×10(16)NP3/g dry weight and 1.7×10(15)NP8/g dry weight. This strain therefore appears as a promising agent for NP bioremediation processes. Proteomic data are available via ProteomeXchange with identifier PXD004012. To the best of our knowledge, this is the first report focussing on the effects of CdSe colloidal nanocrystals (CdSe NPs) on a marine strain of Pseudomonas fluorescens. CdSe NPs are extensively used in the industry of renewable energies and it is regrettably expected that these pollutants will sometime soon appear in the marine environment through surface runoff, urban effluents and rivers. Bacteria living in estuarine and coastal sediments will be among the first targets of these new pollutants. The pseudomonads are frequently found in these ecosystems

Infiltration of CdTe nano crystals into a ZnO wire vertical matrix by using the isothermal closed space technique

NASA Astrophysics Data System (ADS)

Larramendi, S.; Vaillant Roca, Lidice; Saint-Gregoire, Pierre; Ferraz Dias, Johnny; Behar, Moni

2017-10-01

A ZnO nanorod structure was grown by the hydrothermal method and interpenetrated with CdTe using the isothermal closed space sublimation technique. The obtained structure was studied by using the Rutherford backscattering spectrometry (RBS), Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM). The X-ray Diffraction (XRD) technique confirmed the presence of CdTe nanocrystals (NCs) of very small size formed on the surface and in the interspaces between the ZnO nanorods. The RBS observations together with the SEM observations give information on the obtained structure. Finally the photoluminescence studies show a strong energy confinement effect on the grown CdTe NCs.

Application of quantum dots CdZnSeS / ZnS luminescence, enhanced by plasmons of silver rough surface for detection of albumin in blood facies of infected person

NASA Astrophysics Data System (ADS)

Konstantinova, E.; Zyubin, A.; Moiseeva, E.; Matveeva, K.; Slezhkin, V.; Samusev, I.; Bryukhanov, V.

2017-12-01

The study of the luminescence of CdZnSeS / ZnS quantum dots (QDs) absorbed on the rough surface of a silver film, including the energy transfer between human serum albumin molecules, isolated from the blood plasma of healthy and infected with sepsis patients, was performed by spectral-kinetic methods.

Core-shell-like Y2O3:[(Tb3+-Yb3+), Li+]/CdZnS heterostructure synthesized by super-close-space sublimation for broadband down-conversion

NASA Astrophysics Data System (ADS)

Wu, Xiaojie; Zhang, Zhenzhong; Meng, Fanzhi; Yu, Yingning; Han, Lin; Liu, Xiaojuan; Meng, Jian

2014-04-01

Combination with semiconductors is a promising approach to the realization of broadband excitation of light conversion materials based on rare earth compounds, to boost the energy efficiency of silicon solar cells. Cd1-xZnxS is a wide bandgap semiconductor with large exciton binding energy. By changing its composition, the bandgap of Cd1-xZnxS can be tuned to match the absorption of trivalent lanthanide (Ln) ions, which makes it a competent energy donor for the Ln3+-Yb3+ couple. In this work, we designed a clean route to a broadband down-converter based on a core-shell-like Y2O3:[(Tb3+-Yb3+), Li+]/Cd0.81Zn0.19S (CdZnS) heterostructure. By hot-pressing and subsequent annealing of a Y2O3:[(Tb3+-Yb3+), Li+]/CdZnS mixture, highly pure CdZnS was sublimated and deposited on the Y2O3:[(Tb3+-Yb3+), Li+] grains while maintaining the original composition of the precursor. The CdZnS shell acted as a light absorber and energy donor for the Tb3+-Yb3+ quantum cutting couple. Because the use of solvents was avoided during the formation of the heterostructures, few impurities were incorporated into the samples, and the non-radiative transition was therefore markedly suppressed. The Y2O3:[(Tb3+-Yb3+), Li+]/CdZnS heterostructures possess strong near-infrared (NIR) luminescence from Yb3+. Broadband down-conversion to the Yb3+ NIR emission was obtained in a wide range of 250-650 nm.

Relation of pH and other soil variables to concentrations of Pb, Cu, Zn, Cd, and Se in earthworms

USGS Publications Warehouse

Beyer, W.N.; Hensler, G.L.; Moore, J.

1987-01-01

Various soil treatments (clay, composted peat, superphosphate, sulfur, calcium carbonate, calcium chloride, zinc chloride, selenous acid) were added to experimental field plots to test the effect of different soil variables on the concentrations of 5 elements in earthworms (Pb, Cu, Zn, Cd, Se). Concentrations of the 5 elements were related to 9 soil variables (soil Pb, soil Cu, soil Zn, pH, organic matter, P, K, Mg, and Ca) with linear multiple regression. Lead concentrations in earthworms were positively correlated with soil Pb and soil organic matter, and negatively correlated with soil pH and soil Mg, with an R2 of 64%. Se concentrations were higher in earthworms from plots amended with Se, and Zn concentrations were higher in earthworms from plots amended with Zn. However, none of the other soil variables had important effects on the concentrations of Cu, Zn, Cd and Se in earthworms. Although some significant statistical relations were demonstrated, the values of r2 of all relations (> 20%) were so low that they had little predictive value.

Hard x-ray response of a CdZnTe ring-drift detector

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

Owens, A.; Hartog, R. den; Quarati, F.

We present the results of an experimental study of a special type of CdZnTe detector of hard x and {gamma} rays--A-drift detector. The device consists of a double ring electrode structure surrounding a central point anode with a guard plane surrounding the outer anode ring. The detector can be operated in two distinctively different modes of charge collection--pseudohemispherical and pseudodrift. We study the detector response profiles obtained by scanning the focused x-ray beam over the whole detector area, specifically the variations in count rate, peak position, and energy resolution for x rays from 10 to 100 keV. In addition, atmore » 662 keV the energy resolution was shown to be 4.8 keV, more than a factor of 2 better than for CdZnTe coplanar grid detectors. To interpret the experimental data, we derive an analytical expression for the spatial distribution of the electric field inside the detector and neglecting carrier diffusion, and identify carrier collection patterns for both modes of operation within the drift model approximation. We show that this model provides a good understanding of measured profiles.« less

Analysis of Deep and Shallow Traps in Semi-Insulating CdZnTe

DOE PAGES

Kim, Kihyun; Yoon, Yongsu; James, Ralph B.

2018-03-13

Trap levels which are deep or shallow play an important role in the electrical and the optical properties of a semiconductor; thus, a trap level analysis is very important in most semiconductor devices. Deep-level defects in CdZnTe are essential in Fermi level pinning at the middle of the bandgap and are responsible for incomplete charge collection and polarization effects. However, a deep level analysis in semi-insulating CdZnTe (CZT) is very difficult. Theoretical capacitance calculation for a metal/insulator/CZT (MIS) device with deep-level defects exhibits inflection points when the donor/acceptor level crosses the Fermi level in the surface-charge layer (SCL). Three CZTmore » samples with different resistivities, 2 × 10 4 (n-type), 2 × 10 6 (p-type), and 2 × 10 10 (p-type) Ω·cm, were used in fabricating the MIS devices. These devices showed several peaks in their capacitance measurements due to upward/downward band bending that depend on the surface potential. In conclusion, theoretical and experimental capacitance measurements were in agreement, except in the fully compensated case.« less

Analysis of Deep and Shallow Traps in Semi-Insulating CdZnTe

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

Kim, Kihyun; Yoon, Yongsu; James, Ralph B.

Trap levels which are deep or shallow play an important role in the electrical and the optical properties of a semiconductor; thus, a trap level analysis is very important in most semiconductor devices. Deep-level defects in CdZnTe are essential in Fermi level pinning at the middle of the bandgap and are responsible for incomplete charge collection and polarization effects. However, a deep level analysis in semi-insulating CdZnTe (CZT) is very difficult. Theoretical capacitance calculation for a metal/insulator/CZT (MIS) device with deep-level defects exhibits inflection points when the donor/acceptor level crosses the Fermi level in the surface-charge layer (SCL). Three CZTmore » samples with different resistivities, 2 × 10 4 (n-type), 2 × 10 6 (p-type), and 2 × 10 10 (p-type) Ω·cm, were used in fabricating the MIS devices. These devices showed several peaks in their capacitance measurements due to upward/downward band bending that depend on the surface potential. In conclusion, theoretical and experimental capacitance measurements were in agreement, except in the fully compensated case.« less

Using electrocoagulation for metal and chelant separation from washing solution after EDTA leaching of Pb, Zn and Cd contaminated soil.

PubMed

Pociecha, Maja; Lestan, Domen

2010-02-15

Electrocoagulation with an Al sacrificial anode was tested for the separation of chelant and heavy metals from a washing solution obtained after leaching Pb (3200 mg kg(-1)), Zn (1100 mg kg(-1)), and Cd (21 mg kg(-1)) contaminated soil with EDTA. In the electrochemical process, the sacrificial anode corroded to release Al(3+) which served as coagulant for precipitation of chelant and metals. A constant current density of 16-128 mAc m(-2) applied between the Al anode and the stainless-steel cathode removed up to 95% Pb, 68% Zn and 66% Cd from the soil washing solution. Approximately half of the initial EDTA remained in the washing solution after treatment, up to 16.3% of the EDTA was adsorbed on Al coagulant and precipitated, the rest of the EDTA was degraded by anodic oxidation. In a separate laboratory-scale remediation experiment, we leached a soil with 40 mmol EDTA per kg of soil and reused the washing solution (after electrocoagulation) in a closed loop. It removed 53% of Pb, 26% of Zn and 52% of Cd from the soil. The discharge solution was clear and colourless, with pH 7.52 and 170 mg L(-1) Pb, 50 mg L(-1) Zn, 1.5 mg L(-1) Cd and 11 mM EDTA.

A rapid and universal bacteria-counting approach using CdSe/ZnS/SiO2 composite nanoparticles as fluorescence probe.

PubMed

Fu, Xin; Huang, Kelong; Liu, Suqin

2010-02-01

In this paper, a rapid, simple, and sensitive method was described for detection of the total bacterial count using SiO(2)-coated CdSe/ZnS quantum dots (QDs) as a fluorescence marker that covalently coupled with bacteria using glutaraldehyde as the crosslinker. Highly luminescent CdSe/ZnS were prepared by applying cadmium oxide and zinc stearate as precursors instead of pyrophoric organometallic precursors. A reverse-microemulsion technique was used to synthesize CdSe/ZnS/SiO(2) composite nanoparticles with a SiO(2) surface coating. Our results showed that CdSe/ZnS/SiO(2) composite nanoparticles prepared with this method possessed highly luminescent, biologically functional, and monodispersive characteristics, and could successfully be covalently conjugated with the bacteria. As a demonstration, it was found that the method had higher sensitivity and could count bacteria in 3 x 10(2) CFU/mL, lower than the conventional plate counting and organic dye-based method. A linear relationship of the fluorescence peak intensity (Y) and the total bacterial count (X) was established in the range of 3 x 10(2)-10(7) CFU/mL using the equation Y = 374.82X-938.27 (R = 0.99574). The results of the determination for the total count of bacteria in seven real samples were identical with the conventional plate count method, and the standard deviation was satisfactory.

Aseptic hydroponics to assess rhamnolipid-Cd and rhamnolipid-Zn bioavailability for sunflower (Helianthus annuus): a phytoextraction mechanism study.

PubMed

Wen, Jia; McLaughlin, Mike J; Stacey, Samuel P; Kirby, Jason K

2016-11-01

The availability of cadmium (Cd) and zinc (Zn) to sunflower (Helianthus annuus) was investigated in rhamnolipid- and ethylenediaminetetraacetic acid (EDTA)-buffered solutions in order to evaluate the influence of aqueous speciation of the metals on their uptake by the plant, in relation to predictions of uptake by the free ion activity model (FIAM). Free metal ion activity was estimated using the chemical equilibrium program MINTEQ or measured by Donnan dialysis. The uptake of Cd followed the FIAM for the EDTA-buffered solution at EDTA concentrations below 0.4 μM; for the rhamnolipid-buffered solution, the uptake of both metals in roots was not markedly affected by increasing rhamnolipid concentrations in solution. This suggests rhamnolipid enhanced metal accumulation in plant roots (per unit free metal in solution) possibly through formation and uptake of lipophilic complexes. The addition of normal Ca concentrations (low millimetre range) to the rhamnolipid uptake solutions reduced Cd accumulation in shoots by inhibiting Cd translocation, whereas it significantly increased Zn accumulation in shoots. This study confirms that although rhamnolipid could enhance accumulation of Cd in plants roots at low Ca supply, it is not suitable for Cd phytoextraction in contaminated soil environments where Ca concentrations in soil solution are orders of magnitude greater than those of Cd.

Cd, Cu, Pb and Zn in clams and sediments from an impacted estuary by the oil industry in the southwestern Gulf of Mexico: concentrations and bioaccumulation factors.

PubMed

Ruelas-Inzunza, J; Spanopoulos-Zarco, P; Páez-Osuna, F

2009-12-01

With the objective of estimating the temporal variation and bioavailability of Cd, Cu, Pb and Zn in Coatzacoalcos estuary, the biota-sediment accumulation factors (BSAF) were calculated. For this purpose, surficial sediments and clams from 14 selected sites were collected during three climatic seasons. In surficial sediments, highest levels of Cd and Cu were measured during the rainy season near to the industrial area of Minatitlan, while highest concentrations of Pb and Zn were registered during the windy season in sediments collected near to the industrial area of Coatzacoalcos. Considering all the sampling seasons and bivalve species, average metal concentrations followed the order Zn > Cu > Cd > Pb. BSAF ranged from 0.01 (Pb) in Corbicula fluminea during the hot season to 25.1 (Cd) in Polymesoda caroliniana during the windy season. BSAF of Cd, Cu and Zn were higher during the windy season; in the case of Pb, the dry season was the time when such figure was more elevated. It can be stated that Polymesoda caroliniana is a net accumulator of Cd and Zn and a weak accumulator of Pb for the studied estuary.

Mechanical and magneto-electronic properties of half-metallic ferromagnetism in Ti-doped ZnSe and CdSe alloys: Ab initio study

NASA Astrophysics Data System (ADS)

El Amine Monir, Mohammed; Ullah, Hayat; Baltach, Hadj; Gulbahar Ashiq, M.; Khenata, R.

2017-11-01

In this article we have studied the structural, elastic, electronic and magnetic properties of Zn1-xTixSe and Cd1-xTixSe alloys at (x = 0.25, 0.50, 0.75) using first principles density functional theory calculations with local spin density approximation (LSDA) and generalized gradient approximation plus Hubbard parameter (GGA+U) as exchange-correlation potential. The physical properties of both alloys were investigated in the zinc-blend phase. The structural parameters at equilibrium are consistent with experimental and earlier theoretical predictions. The elastic constants are also computed and compared with the literature. The DOS curves of Zn1-xTixSe and Cd1-xTixSe alloys for all the concentrations show the existence of hybridization among Ti (3d) and Se (4p) states. The calculated exchange constants N0α(s-d) and N0β (p-d) are useful to determine the contribution in the valence band and conduction band and are also shows the magnetic character of these alloys. In addition, the p-d hybridization in the PDOS reduces local magnetic moment of Ti from its free space charge of 2 μB and results small magnetic moments on the nonmagnetic Zn, Cd and Se sites. The calculated negative values of formation energy (Ef) reveal that all the Zn1-xTixSe and Cd1-xTixSe alloys are thermodynamically stables. A larger/Smaller value of Curie temperature (TC) for all the Zn1-xTixSe and Cd1-xTixSe alloys shows the strong/low interaction among the magnetic atoms respectively.

Azurin/CdSe-ZnS-Based Bio-Nano Hybrid Structure for Nanoscale Resistive Memory Device.

PubMed

Yagati, Ajay Kumar; Lee, Taek; Choi, Jeong-Woo

2017-07-15

In the present study, we propose a method for bio-nano hybrid formation by coupling a redox metalloprotein, Azurin, with CdSe-ZnS quantum dot for the development of a nanoscale resistive memory device. The covalent interaction between the two nanomaterials enables a strong and effective binding to form an azurin/CdSe-ZnS hybrid, and also enabled better controllability to couple with electrodes to examine the memory function properties. Morphological and optical properties were performed to confirm both hybrid formations and also their individual components. Current-Voltage (I-V) measurements on the hybrid nanostructures exhibited bistable current levels towards the memory function device, that and those characteristics were unnoticeable on individual nanomaterials. The hybrids showed good retention characteristics with high stability and durability, which is a promising feature for future nanoscale memory devices.

Heavy metal (Cu, Zn, Cd and Pb) partitioning and bioaccessibility in uncontaminated and long-term contaminated soils.

PubMed

Lamb, Dane T; Ming, Hui; Megharaj, Mallavarapu; Naidu, Ravi

2009-11-15

We investigated the pore-water content and speciation of copper (Cu), zinc (Zn), cadmium (Cd) and lead (Pb) in a range of uncontaminated and long-term contaminated soils in order to establish their potential bioaccessibility to soil biota, plants and humans. Among the samples, soil pH (0.01 M CaCl(2)) ranged from 4.9 to 8.2. The total metal content of the uncontaminated soils ranged from 3.8 to 93.8 mg Cu kg(-1), 10.3 to 95 mg kg(-1) Zn, 0.1 to 1.8 mg Cd kg(-1) and 5.2 to 183 mg kg(-1) Pb, while metal content in the contaminated soils ranged from 104 to 6841 mg Cu kg(-1), 312 to 39,000 mg kg(-1) Zn, 6 to 302 mg Cd kg(-1) and 609 to 12,000 mg kg(-1) Pb. Our analysis of pore-water found the Cu concentrations to be much higher in contaminated soils than in uncontaminated soils, with the distribution coefficients (K(d)) correlating significantly with the log of dissolved organic carbon concentrations. Despite the high total metal content of the contaminated soil, Zn, Cd and Pb were not generally found at elevated levels in the pore-water with the exception of a single contaminated soil. A long period of ageing and soil weathering may have led to a substantial reduction in heavy metal concentrations in the pore-water of contaminated soils. On the other hand, Pb bioaccessibility was found to be comparatively high in Pb contaminated soils, where it tended to exceed the total Pb values by more than 80%. We conclude that, despite the extensive ageing of some contaminated soils, the bioaccessibility of Pb remains relatively high.

Hybride ZnCdCrO embedded aminated polyethersulfone nanocomposites for the development of Hg2+ ionic sensor

NASA Astrophysics Data System (ADS)

Rahman, Mohammed M.; Alenazi, Noof A.; Hussein, Mahmoud A.; Alam, M. M.; Alamry, Khalid A.; Asiri, Abdullah M.

2018-06-01

In this current study, ‑NH2 functions are introduced on Polyethersulfone (PES) by a nitration reaction then a reduction reaction to fabricate PES-NH2 materials with a better hydrophilicity property. The structure of PES-NH2 was first confirmed using proton nuclear magnetic resonance spectroscopy (1H-NMR) and Fourier transform infrared (FT-IR) spectroscopy. Then, the resultant polymer was doped with different concentrations of ZnCdCrO nanocomposites. The polymeric nanocomposites materials were characterized using FT-IR, x-ray powder diffraction (XRD), thermal analysis (TA), and energy dispersive x-ray (EDX) spectroscopy while the morphology was investigated using scanning electron microscopy (SEM). The performance PES-NH2-ZnCdCrO nanocomposites was investigated by sensor-probe towards the selective detection of Hg2+. The results showed the excellent thermal properties of PES-NH2-ZnCdCrO nanocomposites in comparison with non-doped polymer (PES-NH2). Here, Hg2+ ionic sensor was prepared using a flat glassy carbon electrode (GCE) coated with a thin-layer of PES-NH2-ZnCdCrO nanocomposites (20%) with nafion conducting nafion binder (5%). To evaluate the analytical performances of Hg2+ ion sensor, a calibration curve was drawn by plotting the current versus concentration. The sensitivity (0.6566 μAμM-1 cm‑2) and detection limit (14.46 ± 0.72 pM) are calculated using the slope of the calibration curve. It was determined the linearity (r2 = 0.9941) over the large linear dynamic range (LDR) (0.1 nM to 0.1 mM). Thus, this research approach might be an important route to the selective detection of environmental toxin (Hg2+ cation) from the aqueous system in broad scales for the safety of health care, environmental, and aquatic fields.

Simultaneous Stripping Detection of Pb(II), Cd(II) and Zn(II) Using a Bimetallic Hg-Bi/Single-Walled Carbon Nanotubes Composite Electrode

PubMed Central

Ouyang, Ruizhuo; Zhu, Zhenqian; Tatum, Clarissa E.; Chambers, James Q.; Xue, Zi-Ling

2011-01-01

A new, sensitive platform for the simultaneous electrochemical assay of Zn(II), Cd(II) and Pb(II) in aqueous solution has been developed. The platform is based on a new bimetallic Hg-Bi/single-walled carbon nanotubes (SWNTs) composite modified glassy carbon electrode (GCE), demonstrating remarkably improved performance for the anodic stripping assay of Zn(II), Cd(II) and Pb(II). The synergistic effect of Hg and Bi as well as the enlarged, activated surface and good electrical conductivity of SWNTs on GCE contribute to the enhanced activity of the proposed electrode. The analytical curves for Zn(II), Cd(II) an Pb(II) cover two linear ranges varying from 0.5 to 11 μg L-1 and 10 to 130 μg L-1 with correlation coefficients higher than 0.992. The limits of detection for Zn(II), Cd(II) are lower than 2 μg L-1 (S/N = 3). For Pb(II), moreover, there is another lower, linear range from 5 to 1100 ng L-1 with a coefficient of 0.987 and a detection limit of 0.12 ng L-1. By using the standard addition method, Zn(II), Cd(II) and Pb(II) ions in river samples were successfully determined. These results suggest that the proposed method can be applied as a simple, efficient alternative for the simultaneous monitoring of heavy metals in water samples. In addition, this method demonstrates the powerful application of carbon nanotubes in electrochemical analysis of heavy metals. PMID:21660117

Wood-derived-biochar combined with compost or iron grit for in situ stabilization of Cd, Pb, and Zn in a contaminated soil.

PubMed

Oustriere, Nadège; Marchand, Lilian; Rosette, Gabriel; Friesl-Hanl, Wolfgang; Mench, Michel

2017-03-01

In situ stabilization of Cd, Pb, and Zn in an Austrian agricultural soil contaminated by atmospheric depositions from a smelter plant was assessed with a pine bark chip-derived biochar, alone and in combination with either compost or iron grit. Biochar amendment was also trialed in an uncontaminated soil to detect any detrimental effect. The pot experiment consisted in ten soil treatments (% w/w): untreated contaminated soil (Unt); Unt soil amended with biochar alone (1%: B1; 2.5%: B2.5) and in combination: B1 and B2.5 + 5% compost (B1C and B2.5C), B1 and B2.5 + 1% iron grit (B1Z and B2.5Z); uncontaminated soil (Ctrl); Ctrl soil amended with 1 or 2.5% biochar (CtrlB1, CtrlB2.5). After a 3-month reaction period, the soil pore water (SPW) was sampled in potted soils and dwarf beans were grown for a 2-week period. The SPW Cd, Pb, and Zn concentrations decreased in all amended-contaminated soils. The biochar effects increased with its addition rate and its combination with either compost or iron grit. Shoot Cd and Zn removals by beans were reduced and shoot Cd, Pb, and Zn concentrations decreased to common values in all amended soils except the B1 soil. Decreases in the SPW Cd/Pb/Zn concentrations did not improve the root and shoot yields of plants as compared to the Ctrl soil.

The Effect of Twin Boundaries on the Spectroscopic Performance of CdZnTe Detectors

NASA Technical Reports Server (NTRS)

Parker, Bradford H.; Stahle, C. M.; Roth, D.; Babu, S.; Tueller, Jack; Powers, Edward I. (Technical Monitor)

2001-01-01

Most single grains in cadmium zinc telluride (CdZnTe) grown by the high-pressure Bridgman (HPB) technique contain multiple twin boundaries. As a consequence, twin boundaries are one of the most common macroscopic material defects found in large area (400 to 700 sq mm) CdZnTe specimens obtained from HPB ingots. Due to the prevalence of twin boundaries, understanding their effect on detector performance is key to the material selection process. Twin boundaries in several 2 mm thick large area specimens were first, documented using infrared transmission imaging. These specimens were then fabricated into either 2 mm pixel or planar detectors in order to examine the effect of the twin boundaries on detector performance. Preliminary results show that twin boundaries, which are decorated with tellurium inclusions, produce a reduction in detector efficiency and a degradation in resolution. The extent of the degradation appears to be a function of the density of tellurium inclusions.

Stacking of ZnSe/ZnCdSe Multi-Quantum Wells on GaAs (100) by Epitaxial Lift-Off

NASA Astrophysics Data System (ADS)

Eldose, N. M.; Zhu, J.; Mavridi, N.; Prior, Kevin; Moug, R. T.

2018-05-01

Here we present stacking of GaAs/ZnSe/ZnCdSe single-quantum well (QW) structures using epitaxial lift-off (ELO). Molecular beam epitaxy (MBE)-grown II-VI QW structure was lifted using our standard ELO technique. The QW structures were transferred onto glass plates and then subsequent layers stacked on top of each other to form a triple-QW structure. This was compared to an MBE-grown multiple-QW (MQW) structure of similar design. Low-temperature (77 K) photoluminescence (PL) spectroscopy was used to compare the two structures and showed no obvious degradation of the ELO stacked layer. It was observed that by stacking the single QW layer on itself we could increase the PL emission intensity beyond that of the grown MQW structure while maintaining narrow line width.

A simple structure of Cu2ZnSnS4/CdS solar cells prepared by sputtering

NASA Astrophysics Data System (ADS)

Li, Zhishan; Wang, Shurong; Ma, Xun; Yang, Min; Jiang, Zhi; Liu, Tao; Lu, Yilei; Liu, Sijia

2017-12-01

In this work, Cu2ZnSnS4 (CZTS) thin films were grown on Mo-coated Soda-lime-glass (SLG) substrates by annealing of sputtered ZnS/Sn/CuS precursors at 580 ℃ for 15 min. As a try, the CZTS solar cells were fabricated using simple structure of Mo-coated SLG/CZTS/CdS/Al and traditional structure of Mo-coated SLG/CZTS/CdS/i-ZnO/In2O3:SnO2 (ITO)/Al, respectively. The results show that the CZTS device with simple structure can achieve same level of the open circuit voltage (Voc) compared with that of traditional structure. In addition, the power conversion efficiency of 2.95% and 3.59% were obtained with simple structure and traditional structure, respectively. The CZTS solar cell with simple structure provides a promising way and an easy process to prepare high-performance CZTS thin film solar cells which is available to large-scale industrial production in the future.

Applications of Digitized 3-D Position-Sensitive CdZnTe Spectrometers for National Security and Nuclear Nonproliferation

NASA Astrophysics Data System (ADS)

Streicher, Michael W.

A nuclear weapon detonation remains one of the gravest threats to the global community. Although the likelihood of a nuclear event remains small, the economic and political ramifications of an event are vast. The surest way to reduce the probability of an incident is to account for the special nuclear materials (SNM) which can be used to produce a nuclear weapon. Materials which can be used to manufacture a radiological dispersion device ("dirty bomb") must also be monitored. Rapidly-deployable, commercially-available, room-temperature imaging gamma-ray spectrometers are improving the ability of authorities to intelligently and quickly respond to threats. New electronics which digitally-sample the radiation-induced signals in CdZnTe detectors have expanded the capabilities of these sensors. This thesis explores national security applications where digital readout of CdZnTe detectors significantly enhances capabilities. Radioactive sources can be detected more quickly using digitally-sampled CdZnTe detector due to the improved energy resolution. The excellent energy resolution also improves the accuracy of measurements of uranium enrichment and allows users to measure plutonium grade. Small differences in the recorded gamma-ray energy spectrum can be used to estimate the effective atomic number and mass thickness of materials shielding SNM sources. Improved position resolution of gamma-ray interactions through digital readout allows high resolution gamma-ray images of SNM revealing information about the source configuration. CdZnTe sensors can detect the presence of neutrons, indirectly, through measurement of gamma rays released during capture of thermal neutrons by Cd-113 or inelastic scattering with any constituent nuclei. Fast neutrons, such as those released following fission, can be directly detected through elastic scattering interactions in the detector. Neutrons are a strong indicator of fissile material, and the background neutron rate is much lower than

Conventional crops and organic amendments for Pb, Cd and Zn treatment at a severely contaminated site.

PubMed

Pichtel, J; Bradway, D J

2008-03-01

The ability of selected plants and amendments to treat Pb, Cd and Zn accumulations from a metalliferous waste disposal site was studied both in the greenhouse and field. Spinach (Spinacea oleracea), cabbage (Brassica oleracea), and a grass-legume mix (red fescue, Festuca rubra; ryegrass, Lolium perenne); and bean (Vicia faba) were grown in the greenhouse on blast furnace slag or baghouse dust amended with composted peat (CP). All plant species accumulated Pb, Cd and Zn to varying degrees. Total soil metal concentrations had a marked influence on plant uptake. Topdressing versus incorporating CP had a significant (p<0.05) effect on spinach and cabbage tissue metal concentrations. Soil Pb and Zn tended to shift towards less bioavailable forms after treatment with CP. Field plots were treated with CP, farmyard manure (FYM), or inorganic fertilizer. Dry matter production of spinach, cabbage and a grass-legume mix was greatest on either the CP or FYM treatments. Phytostabilization in combination with organic amendments may be the most appropriate technology to ensure stabilization of soil metals at this site.

Erratum: Synthesis of Cd-free InP/ZnS Quantum Dots Suitable for Biomedical Applications.

PubMed

2016-02-29

A correction was made to: Synthesis of Cd-free InP/ZnS Quantum Dots Suitable for Biomedical Applications. There was an error with an author's given name. The author's name was corrected to: Katye M. Fichter from: Kathryn M. Fichter.

Uptake and loss kinetics of Cd, Cr and Zn in the bivalves Potamocorbula amurensis and Macoma balthica: Effects of size and salinity

USGS Publications Warehouse

Lee, B.-G.; Wallace, W.G.; Luoma, S.N.

1998-01-01

Radiotracer studies were employed to quantitatively compare the biokinetics of uptake from the dissolved phase (influx rates) and loss (efflux) between 2 bivalves, Potamocorbula amurensis and Macoma balthica, and among the metals Cd, Cr and Zn. Effects of salinity on influx rate were evaluated in these 2 highly euryhaline species as were effects of animal size on uptake and loss. Metal speciation and biological attributes interacted to differentiate bioaccumulation processes among metals and between species. Influx rates of the 3 metals (??g g-1 [dry wt] d-1) increased linearly with dissolved metal concentrations. Influx rates of Zn in both clams were 3 to 4x those for Cd and 15x those for Cr. However, influx on the basis of free ion activities would be faster for Cd than for Zn. Relative influx rates among the metals were similar in the 2 bivalves. But, absolute influx rates of all 3 metals were 4 to 5x greater in P. amurensis than in M. balthica, probably because of differences in biological attributes (i.e. clearance rate or gill surface area). As salinity was reduced from 30 to 5 psu, the influx rate of Cd for P. amurensis increased 4-fold and that for M. balthica increased 6-fold, consistent with expected changes in speciation. However the influx rates of Cr in both clams also increased 2.4-fold over the same range, indicating a biological contribution to the salinity effect. Influx rates of Zn were not significantly affected by salinity. Weight specific metal influx rates (??g g-1 [dry wt] d-1) were negatively correlated with the tissue dry weight of the clams, but most rate constants determining physiological turnover of assimilated metals were not affected by clam size. The exception was the rate constant for Cd loss, which resulted in faster turnover in large M. balthica than in smaller clams. The rate constant of loss for P. amurensis increased in the order of Cd (0.011 d-1) < Zn (0.027 d-1) < Cr (0.048 d-1). This was different from the hierarchy of rate

ZnS, CdS and HgS nanoparticles via alkyl-phenyl dithiocarbamate complexes as single source precursors.

PubMed

Onwudiwe, Damian C; Ajibade, Peter A

2011-01-01

The synthesis of II-VI semiconductor nanoparticles obtained by the thermolysis of certain group 12 metal complexes as precursors is reported. Thermogravimetric analysis of the single source precursors showed sharp decomposition leading to their respective metal sulfides. The structural and optical properties of the prepared nanoparticles were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) UV-Vis and photoluminescence spectroscopy. The X-ray diffraction pattern showed that the prepared ZnS nanoparticles have a cubic sphalerite structure; the CdS indicates a hexagonal phase and the HgS show the presence of metacinnabar phase. The TEM image demonstrates that the ZnS nanoparticles are dot-shaped, the CdS and the HgS clearly showed a rice and spherical morphology respectively. The UV-Vis spectra exhibited a blue-shift with respect to that of the bulk samples which is attributed to the quantum size effect. The band gap of the samples have been calculated from absorption spectra and werefound to be about 4.33 eV (286 nm), 2.91 eV (426 nm) and 4.27 eV (290 nm) for the ZnS, CdS and HgS samples respectively.

ZnS, CdS and HgS Nanoparticles via Alkyl-Phenyl Dithiocarbamate Complexes as Single Source Precursors

PubMed Central

Onwudiwe, Damian C.; Ajibade, Peter A.

2011-01-01

The synthesis of II-VI semiconductor nanoparticles obtained by the thermolysis of certain group 12 metal complexes as precursors is reported. Thermogravimetric analysis of the single source precursors showed sharp decomposition leading to their respective metal sulfides. The structural and optical properties of the prepared nanoparticles were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) UV-Vis and photoluminescence spectroscopy. The X-ray diffraction pattern showed that the prepared ZnS nanoparticles have a cubic sphalerite structure; the CdS indicates a hexagonal phase and the HgS show the presence of metacinnabar phase. The TEM image demonstrates that the ZnS nanoparticles are dot-shaped, the CdS and the HgS clearly showed a rice and spherical morphology respectively. The UV-Vis spectra exhibited a blue-shift with respect to that of the bulk samples which is attributed to the quantum size effect. The band gap of the samples have been calculated from absorption spectra and werefound to be about 4.33 eV (286 nm), 2.91 eV (426 nm) and 4.27 eV (290 nm) for the ZnS, CdS and HgS samples respectively. PMID:22016607

An "off-on" sensor for fluoride using luminescent CdSe/ZnS quantum dots.

PubMed

Mulrooney, Ray C; Singh, Narinder; Kaur, Navneet; Callan, John F

2009-02-14

The fluorescence emission of CdSe/ZnS QDs was switched "off" when the native trioctylphosphine oxide ligands were exchanged for 1-(bis(eta(5)-cyclopentadienyl)iron)-methyl-3-(5,7-dimercapto-heptyl)-urea (); importantly, the emission of the resulting conjugate was switched "on" upon addition of fluoride ions.

Effect of alkaline material on phytotoxicity and bioavailability of Cu, Cd, Pb and Zn in stabilized sewage sludge.

PubMed

Zhang, Hongling; Ma, Guofeng; Sun, Lina; Li, Huiying

2017-07-16

The availability and phytotoxicity of heavy metals in sewage sludge is the key restrictive factor that limits sludge application. In this study, municipal sewage sludge was stabilized by alkaline slag or coal fly ash, then the leaching characteristic and fraction distributions of Cu, Cd, Pb and Zn were studied, and their effects on seed germination, root length, and plant accumulating were compared. The results showed that mixed sewage sludge with alkaline slag and coal fly ash decreased the percentage of available heavy metals in sewage sludge. The percentage of exchangeable Cu, Pb, Zn and Cd in stabilized sewage sludge (S1-S4) was 1.50-8.67 times lower than that in SS-only treatment. Leachate Cd, Cu, Pb and Zn from stabilized SS was much lower than the limit threshold. The addition of alkaline materials to SS reduced the inhibitory effect on seed germination and root growth. Pearson's correlation analysis indicated that there was a significant negative correlation between pH and available heavy metals, while a significant positive correlation between the percentage of exchangeable fraction of heavy metals, the leaching potential, tissue concentration and accumulation of heavy metal and toxicity for seed germination was observed.

Solvo-thermal synthesis of a unique alkaline earth-transition Ba-Cd micro-porous coordination framework as hetero-metallic luminescent sensor for Cu2+ and real-time detection of benzaldehyde.

PubMed

Ding, Bin; Ma, Dian Xue; Zhang, Hui Min; Meng, Xin; Qiu, Rong Rong; Ren, Rong; Wu, Jie; Wu, Xiang Xia; Huo, Jian Zhong; Liu, Yuan Yuan; Shi, Xue Fang

2018-06-15

In this work a unique hetero-metallic alkaline earth-transition Ba-Cd luminescent micro-porous metal-organic framework {[BaCd(μ 6 -tp) 1.5 (μ 2 -Cl)(H 2 O) (DMF) 2 ]·0.75H 2 O} n (H 2 tp=terephthalic acid) (1) has been prepared under solvo-thermal conditions. In 1 infinite 1D {Ba-X-Cd} (X=O, Cl) inorganic chains are linked via these full de-pronated tp 2- ligands forming a unique 3D I 1 O 2 type micro-porous coordination framework. PXRD patterns of 1 have been determined confirming pure phases of 1. Luminescence investigations suggested that 1 exhibits highly selective and sensitive sensing for trace amounts of benzaldehyde in ethanol, which provides a facile method for real-time detection of benzaldehyde. Meanwhile 1 also exhibits highly selective and sensitive sensing for Cu 2+ over other cations with high quenching efficiency K sv value 1.15×10 4 L·mol -1 . As far as we know, 1 represents the first example of alkaline earth-transition hetero-metallic Ba-Cd micro-porous coordination framework as bi-functional luminescent probes for Cu 2+ and benzaldehyde. Copyright © 2018 Elsevier B.V. All rights reserved.

Removal Efficiency of the Heavy Metals Zn(II), Pb(II) and Cd(II) by Saprolegnia delica and Trichoderma viride at Different pH Values and Temperature Degrees

PubMed Central

Hashem, Mohamed

2007-01-01

The removal efficiency of the heavy metals Zn, Pb and Cd by the zoosporic fungal species Saprolegnia delica and the terrestrial fungus Trichoderma viride, isolated from polluted water drainages in the Delta of Nile in Egypt, as affected by various ranges of pH values and different temperature degrees,was extensively investigated. The maximum removal efficiency of S. delica for Zn(II) and Cd(II) was obtained at pH 8 and for Pb(II) was at pH 6 whilst the removal efficiency of T. viride was found to be optimum at pH 6 for the three applied heavy metals. Regardless the median lethal doses of the three heavy metals, Zn recorded the highest bioaccumulation potency by S. delica at all pH values except at pH 4, followed by Pb whereas Cd showed the lowest removal potency by the fungal species and vice versa in case of T. viride. The optimum biomass dry weight production by S. delica was found when the fungus was grown in the medium treated with the heavy metal Pb at pH 6, followed by Zn at pH 8 and Cd at pH 8. The optimum biomass dry weight yield by T. viride amended with Zn,Pb and Cd was obtained at pH 6 for the three heavy metals with the maximum value at Zn. The highest yield of biomass dry weight was found when T. viride treated with Cd at all different pH values followed by Pb whilst Zn output was the lowest and this result was reversed in case of S. delica. The maximum removal efficiency and the biomass dry weight production for the three tested heavy metals was obtained at the incubation temperature 20℃ in case of S. delica while it was 25℃ for T. viride. Incubation of T. viride at higher temperatures (30℃ and 35℃) enhanced the removal efficiency of Pb and Cd than low temperatures (15℃ and 20℃) and vice versa in case of Zn removal. At all tested incubation temperatures, the maximum yield of biomass dry weight was attained at Zn treatment by the two tested fungal species. The bioaccumulation potency of S. delica for Zn was higher than that for Pb at all

Cd(1-x)Zn(x)O [0.05 ≤x≤ 0.26] synthesized by vapor-diffusion induced hydrolysis and co-nucleation from aqueous metal salt solutions.

PubMed

Schwenzer, Birgit; Neilson, James R; Jeffries, Stacie M; Morse, Daniel E

2011-02-14

Nanoparticulate Cd(1-x)Zn(x)O (x = 0, 0.05-0.26, 1) is synthesized in a simple two-step synthesis approach. Vapor-diffusion induced catalytic hydrolysis of two molecular precursors at low temperature induces co-nucleation and polycondensation to produce bimetallic layered hydroxide salts (M = Cd, Zn) as precursor materials which are subsequently converted to Cd(1-x)Zn(x)O at 400 °C. Unlike ternary materials prepared by standard co-precipitation procedures, all products presented here containing < 30 mol% Zn(2+) ions are homogeneous in elemental composition on the micrometre scale. This measured compositional homogeneity within the samples, as determined by energy dispersive spectroscopy and inductively coupled plasma spectroscopy, is a testimony to the kinetic control achieved by employing slow hydrolysis conditions. In agreement with this observation, the optical properties of the materials obey Vegard's Law for a homogeneous solid solution of Cd(1-x)Zn(x)O, where x corresponds to the values determined by inductively coupled plasma analysis, even though powder X-ray diffraction shows phase separation into a cubic mixed metal oxide phase and a hexagonal ZnO phase at all doping levels.

Zn(II) and Cd(II) coordination polymers with tri-tert-butoxysilanethiol and bipyridines. Synthesis, crystal structure and spectroscopy

NASA Astrophysics Data System (ADS)

Pladzyk, Agnieszka; Ponikiewski, Łukasz; Stanulewicz, Natalia; Hnatejko, Zbigniew

2013-12-01

Three new zinc(II) and cadmium(II) silanethiolate complexes [Zn{SSi(OtBu)3}2(μ-bpea)ṡCH3CN]n1, [Cd{SSi(OtBu)3}2(μ-bpea)ṡ2CHCl3]n2 and [Cd{SSi(OtBu)3}2(μ-bpey)ṡC7H8]n3 with two bypiridine derivatives, [bpea = 1,2-bis(4-pyridyl)ethane and bpey = 1,2-bis(4-pyridyl)ethylene] have been synthesized and structurally characterized by X-ray crystallography. Their structures and properties have also been established with elemental analysis, IR, TGA and photoluminescent studies. Complexes 1-3 exhibit one-dimensional (1D) chain structures in which [M{SSi(OtBu)3}2] (M = Zn, Cd) units are held together by bpea or bpey bridges, respectively. Complexes are stable up to 300 °C and display blue emissions.

Fabrication of ZnO/SnO2 hierarchical structures as the composite photoanodes for efficient CdS/CdSe co-sensitized solar cells

NASA Astrophysics Data System (ADS)

Lin, Yibing; Lin, Yu; Wu, Jihuai; Zhang, Xiaolong; Fang, Biaopeng

2017-03-01

The composite photoanodes based on the ZnO/SnO2 hierarchical structures with high photoelectricity properties have been successfully synthesized, and used in the CdS and CdSe quantum dots co-sensitized solar cells (QDSSCs). In this experiment, the ZnO/SnO2 nanoparticles (ZS-NP) and hierarchical nanosheets-based microflowers (ZS-MF) were prepared by the one-step hydrothermal route and the morphologies of the products were controlled by the solvent variation. An improved power conversion efficiency of 4.98% was achieved for the cell based on the ZS-MF composite photoanodes, which showed an increase of 21.8% compared to the ZS-NP photoanodes (4.09%). This result is mainly connected to the unique superiority of the three-dimensional hierarchical microflower nanostructures for light scattering and quantum dots loading, which is responsible for the increase of photocurrent values and eventual PCE.

Peculiar enhancement of the excitonic emission of CdSe/ZnSe quantum wells at ˜ 90 K when excited with a HeCd laser

NASA Astrophysics Data System (ADS)

Alfaro-Martínez, Adrián; Hernández-Calderón, Isaac

2018-02-01

The close coincidence at low temperatures of the HeCd blue laser line (442 nm, Elaser = 2.808 eV) with the ZnSe bandgap, Eg = 2.821 eV, and with the excitonic emission at ˜2.80 eV, allows the observation of peculiar effects during photoluminescence studies of CdSe/ZnSe quantum wells with a typical experimental setup. One effect is the enhancement of the excitonic emission at ˜ 90 - 100 K; the second effect is the presence of strong longitudinal optical (LO) phonon lines (in a broad temperature range) due to resonant Raman scattering. Here, we will show that the enhancement of the excitonic emission, that can be misinterpreted as caused by an intrinsic temperature dependent behavior of the quantum wells, is due to the high absorption of the blue laser light by the barriers when the ZnSe bandgap coincides with Elaser at ˜ 90 K, electron and holes produced in the barriers diffuse to the quantum wells enhancing their excitonic emission.

Performance comparison of small-pixel CdZnTe radiation detectors with gold contacts formed by sputter and electroless deposition

NASA Astrophysics Data System (ADS)

Bell, S. J.; Baker, M. A.; Duarte, D. D.; Schneider, A.; Seller, P.; Sellin, P. J.; Veale, M. C.; Wilson, M. D.

2017-06-01

Recent improvements in the growth of wide-bandgap semiconductors, such as cadmium zinc telluride (CdZnTe or CZT), has enabled spectroscopic X/γ-ray imaging detectors to be developed. These detectors have applications covering homeland security, industrial analysis, space science and medical imaging. At the Rutherford Appleton Laboratory (RAL) a promising range of spectroscopic, position sensitive, small-pixel Cd(Zn)Te detectors have been developed. The challenge now is to improve the quality of metal contacts on CdZnTe in order to meet the demanding energy and spatial resolution requirements of these applications. The choice of metal deposition method and fabrication process are of fundamental importance. Presented is a comparison of two CdZnTe detectors with contacts formed by sputter and electroless deposition. The detectors were fabricated with a 74 × 74 array of 200 μm pixels on a 250 μm pitch and bump-bonded to the HEXITEC ASIC. The X/γ-ray emissions from an 241Am source were measured to form energy spectra for comparison. It was found that the detector with contacts formed by electroless deposition produced the best uniformity and energy resolution; the best pixel produced a FWHM of 560 eV at 59.54 keV and 50% of pixels produced a FWHM better than 1.7 keV . This compared with a FWHM of 1.5 keV for the best pixel and 50% of pixels better than 4.4 keV for the detector with sputtered contacts.

Development of a Spectral Model Based on Charge Transport for the Swift/BAT 32K CdZnTe Detector Array

NASA Technical Reports Server (NTRS)