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Widespread concern has been attached to the frequent occurrence of pollution by oil slicks and water-soluble pollutants in recent years. The semiconductor photocatalysis is applied to sewage treatment owing to the advantages of energy-conserving and environmental protection. However, its application is limited by the defects of not solving oil slicks and the hard recyclability. In this paper, the high specific surface area and rod-shaped CdS were prepared using template and alkali-treated methods. Next, the alkylated SiO2 and alkali-treated CdS were deposited on pure fabric by physical deposition to prepare the multifunctional superhydrophobic fabric. The specific surface area and morphology of alkali-treated CdS were tested by BET specific surface area test and field emission scanning electron microscope. Besides, oil/water separation, water contact angle, and stability test experiments were performed to determine the superhydrophobic performance. Photocatalysis degradation efficiency and cycle degradation stability of multifunctional fabric were characterized by photocatalysis degradation Rh B experiment. Consequently, the alkali-treated CdS displays a high specific surface up to 343 m2 g−1. The multifunctional fabric presents excellent superhydrophobic performance with the water contact angle up to 155°. Meanwhile, the water contact angle of multifunctional fabric is always over 150° under various circumstances (acid-base corrosion, soaking time at 100 °C and frictional numbers), indicating that the multifunctional fabric has excellent superhydrophobic stability. Moreover, the fabric also exhibits outstanding photocatalysis performance (the degradation efficiency is 94% after 3 cycles). Our work provides a feasible method for addressing oil slicks on water surface and degrading water-soluble pollutants with extensive application prospects in water resource remediation. [ABSTRACT FROM AUTHOR]

In this paper, we report a feasibility study of MuGFETs (multi-gate field effect transistors) devices using solution-based cadmium sulfide films as the semiconductor. The simulations were carried out using the commercially available ATLAS simulator. Experimental parameters for CdS were extracted from planar thin film transistors fabricated using photolithography methods. Several critical design parameters for MuGFETs devices were studied, including fin width, fin high, channel length, and CdS carrier concentration. Short-channel effects can be reasonably controlled by reducing either fin height or width. It is shown that is possible to fabricate devices that operate in depletion or enhancement mode by controlling the device structure. ION/IOFF ratio was in the range 108–1010, subthreshold slope was closely related to the geometry of the MuGFET. We also observed that as the CdS carrier concentration decreases, the on-voltage shifts to positive values. Optimized MuGFETs simulated in enhancement mode show excellent subthreshold slope, and ION/IOFF ratio ∼1010. This study demonstrates that CdS can be used to fabricate enhanced mode/depletion mode devices using solution-based semiconductors. Furthermore, all processing is kept at temperatures below 100 °C, which demonstrates that these devices can be used in flexible substrates. [ABSTRACT FROM AUTHOR]

Presence of inorganic pollutants in water reservoirs is the treating factor for human health and environment. Semiconductor quantum dots (QDs) has been regarded as one of the most efficient nanoparticles for their enhanced photocatalytic activity. Medicinal plants are the safe sources to provide green template for biosynthesis of inorganic nanoparticles such as quantum dots. In order to determine the photocatalytic and biological application of cadmium sulfide quantum dots (CdS QDs), a biosynthesis approach was employed using saffron (Crocus sativus L.) stigma extract as the green reaction substrate. The biosynthesis process was evaluated at different pH condition to obtain the most efficient CdS QDs. Characterization of prepared CdS QDs were determined through UVâ€"vis and fluorescence spectroscopy, FTIR and TEM analysis. The obtained results showed well dsispersed and uniform QDs during green synthesis at the optimum condition. The absorption and electrical properties of green synthesized CdS QDs showed the lowest energy bandgap of 2.4 at pH 11. Photocatalytic activity of CdS QDs on Rhodamine B degradation showed 92% degradation after 80 min under UV light irradiation. The antibacterial and cell cytotoxicity of green synthesized CdS QDs were assayed by disk diffusion and MTT assays respectively. Obtained results showed significant antibacterial effect of CdS QDs against gram-positive and gram-negative bacteria including B. subtilis (90%) and E. coli (96%) respectively. Moreover, cytotoxicity of prepared CdS Qds through MTT assay indicated 79% apoptosis induction on MCF-7 breast cancer cells. [ABSTRACT FROM AUTHOR]

It has been predicted that high-order harmonic generation (HHG) in nanowires has the potential to scale up photon energy and harmonic yield. However, studies on HHG in nanowires are still theoretical and no relevant experimental results have been reported as yet. Our experimental observation of the high-order harmonic in cadmium sulfide nanowires (CdS NWs) excited by a mid-infrared laser is, to our knowledge, the first of such study, and it verifies some of the theoretical results. Our experimental results show that the observed harmonics are strongest when a pump laser is parallel to the nanowires. Therefore, the theoretical prediction that harmonics are strongest under the nanowires parallel to the laser field is confirmed experimentally, and this can be used to determine the orientation of the nanowire. In addition, harmonics are sensitive to the variation of pump light ellipticities. This orientation dependence opens new opportunities to access the ultrafast and strong-field physics of nanowires. [ABSTRACT FROM AUTHOR]

This paper studies the electronic transport in an individual helically twisted CdS nanowire rope, on which platinum microleads are attached by focused-ion beam deposition. The current-voltage (I -V) characteristics are nonlinear from 300 down to 60 K. Some step-like structures in the I - V curves and oscillation peaks in the differential conductance (dI/dV - V) curves have been observed even at room temperature. It proposes that the observed behaviour can be attributed to Coulomb-blockade transport in the one-dimensional CdS nanowires with diameters of 6-10 nm. [ABSTRACT FROM AUTHOR]

Herein, we report the low-temperature fabrication process and the electrical response of n-type cadmium sulfide (CdS)-based thin-film transistors (TFTs) with an Al2O3-GPTMS-polymethylmethacrylate (PMMA) hybrid dielectric gate. The TFTs with bottom-gate structure were assembled on ITO (indium-tin-oxide)-coated glass substrates employing solution processes for the deposition of both the dielectric gate and semiconductor layers. The hybrid dielectric layers were deposited by the sol-gel process and subsequently annealed at 150 °C. The FTIR and XPS analysis of the hybrid films demonstrated a proper link between Al2O3 and PMMA through the cross-linking agent 3-glycidoxy(propyltrimethoxysilane) silane (GPTMS). The surface characteristics were obtained by contact angle and atomic force microscope studies, the results show that the surface of hybrid films displays a hydrophobic behavior with a smooth surface. The CdS active layer was deposited on the hybrid dielectric gate at room temperature by a simple photochemical bath deposition using a 313 nm UV lamp. The CdS-TFTs showed outstanding electrical performance with a low threshold voltage of 1.3 V, ION/IOFF of 104, subthreshold swing of 440 mV dec−1, and remarkable high mobility value of 64.4 cm2 V−1 s−1. Ultimately, the feature of these completely solution-based CdS TFTs is the maximum processing temperature of 150 °C, and the findings of this study are very promising for potential low-cost solution-processed TFTs. [ABSTRACT FROM AUTHOR]

Substrates of wide band-gap II–VI semiconductor compounds are considered feasible for the fabrication of nanoporous matrices (NM) needed for templated growth of nanowires and nanotubes of solid-state materials promising for applications in various fields. An accessible and cost-effective approach to fabricate NM is based on electrochemical etching (ECE) which, however, depends on the electrical conductivity of the substrates. In this paper, growth of homogeneous ZnxCd1−xS single crystals, with x varying from 0 to 1, is demonstrated and the influence of chemical composition on optical and electrical properties of the crystals is identified. The feasibility of using ZnxCd1−xS alloys with x = 0–0.6 for the growth of nanopore arrays with pore diameter down to 30 nm is shown. The perspectives and limitations of the use of these semiconductor alloys for the fabrication of NM by means of ECE are discussed. [ABSTRACT FROM AUTHOR]

The cadmium sulphide (CdS) film is grown on cadmium telluride (CdTe) nanorods (NRs) arrays by different methods such as chemical bath deposition (CBD), magnetron sputtering (MS), and homogenous precipitation (HP) techniques. The impact of various deposition methods is explored in detail on the growth of CdTe/CdS composite film, the CdTe/CdS interface property, and solar cell efficiency. Compared to the CBD and HP methods, the MS method can improve the growth of the CdS on CdTe NRs with high crystalline quality. The device based on the CdS film prepared by the MS method demonstrates excellent photovoltaic performance, which has the potential for applications in solar cells. [ABSTRACT FROM AUTHOR]

Nanowires and nanotubes could become important building blocks in advanced photonic systems owing to their fascinating optoelectronic properties and high compatibility with versatile chemical synthetic methods. Many intriguing studies have been enabled by applying these nanostructures in the construction of various types of active and passive photonic components. Successful examples are the recent demonstration of semiconductor and plasmonic lasers based on CdS nanowires (Duan et al 2003 Nature421 241–5, Oulton et al 2009 Nature461 629–32, Ma et al 2010 Nature Mater.10 110–13), which generate and deliver intense coherent light down to and even below the diffraction-limited scale. Here in this paper, by carrying out a numerical investigation of a novel hybrid plasmonic structure that consists of a CdS nanotube sitting above a metal substrate separated by a nanometric MgF2 layer, we show theoretically that nanotube-based plasmonic structures can also act as highly efficient lasing sources. Optical properties of such a laser configuration including modal behaviour and the lasing threshold is investigated with regard to the variation of key geometrical parameters. Simulation results reveal that the employment of a CdS nanotube may result in improved optical performance compared with the conventional CdS-nanowire-based plasmon laser. Reduced lasing threshold with mitigated modal loss can be achieved simultaneously under carefully engineered geometries. We also explore the feasibility of combining nanowire- and nanotube-based active and passive components for on-chip integrations. As a simple demonstration, monolithic integration of a CdS nanotube laser with a CdS-nanowire-based passive component is shown numerically on a single chip. We expect that these studies could lay the foundations for nanotube- and nanowire-based hybrid integrated photonic components and circuits. [ABSTRACT FROM AUTHOR]

A novel photo-impedance (hybrid photocapacitive-photoresistive) sensor for visible light employs gated cadmium sulfide photoresistance connecting two fixed capacitances. The changes of the photoresistance and of the metal–insulator (dielectric)-semiconductor (MIS) under illumination affect the overall device capacitance. The MIS and photoresistor frequency dispersion allows for increasing the dynamic range by measuring the capacitance response at lower frequencies. By making this device a part of the tank circuit of a radio frequency oscillator, the information on illumination intensity can be relayed as the signal frequency and detected remotely. [ABSTRACT FROM AUTHOR]

The authors report the successful site-specific deposition of cadmium sulfide (CdS) using a focused electron beam and a liquid-phase solution of cadmium salts and thiourea as the primary reagents. Nanostructures with a minimum feature size of 84 nm are patterned with little to no extraneous deposition. The composition and phase of the CdS nanostructures is investigated by energy dispersive x-ray spectroscopy, transmission electron microscopy and photoluminescence spectroscopy. Critically, these results demonstrate one-step patterning of a semiconducting material from a multi-reagent liquid precursor. [ABSTRACT FROM AUTHOR]

Cadmium sulphide (CdS) and cadmium telluride (CdTe) thin films are deposited by electron beam evaporation. Atomic force microscopy (AFM) reveals that the root mean square (RMS) roughness values of the CdS films increase as substrate temperature increases. The optical band gap values of CdS films increase slightly with the increase in the substrate temperature, in a range of 2.42–2.48 eV. The result of Hall effect measurement suggests that the carrier concentration decreases as the substrate temperature increases, making the resistivity of the CdS films increase. CdTe films annealed at 300°C show that their lowest transmittances are due to their largest packing densities. The electrical characteristics of CdS/CdTe thin film solar cells are investigated in dark conditions and under illumination. Typical rectifying and photovoltaic properties are obtained. [ABSTRACT FROM AUTHOR]

Core-level interatomic resonant Auger in isolated molecules can take place when the photon energy is tuned to a resonant core-level excitation of an atom neighbouring the electron-emitter atom, provided that the emitter atom has smaller ionization energy of core electrons than the resonant energy. A multi-atomic nature of the Auger is a molecular analogue of multi-atom resonant photoemission (MARPE) observed in a condensed phase. This phenomenon in linear molecules, NO and CS2, has been explored by means of a photoelectron-fragment-ion-fragment-ion multi-coincidence velocity mapping technique. The N 1s (S 2p) photoionization experiments have been conducted at the O 1s ? p* (C 1s ? p*) resonance energy and at the off-resonance one, in which photoelectron angular distributions were obtained with respect to the recoil axis of the fragment ions produced by an Auger decay following the core-level photoemission. A resonance enhancement was observed along the photon polarization direction and this effect strongly depends on the relative geometry of the polarization vector and the recoil axis. By comparing the N 1s photoemission of NO with the S 2p photoemission of CS2, it is shown that the resonance enhancement also depends on the core-orbital characters that participate in the process. Such phenomenon should be considered to be general and the present results of the simplest system thus shed new light on photoemission studies for both isolated molecules and condensed systems consisting of different elements. [ABSTRACT FROM AUTHOR]

The valence band offset (VBO) at the interface CdS/Cu2ZnSnS4 was investigated by x-ray photoelectron spectroscopy (XPS). The VBO was measured by two different procedures: an indirect method involving the measurements of the core levels together with the XPS bulk valence band (VB) spectra and a direct method involving the analysis of XPS VB spectra at the interface. The indirect method resulted in a VBO value of (-1.20 ± 0.14) eV while the direct method returned a similar value of (-1.24 ± 0.06) eV but affected by a lower uncertainty. The conduction band offset (CBO) was calculated from the measured VBO values. These two measured values of the VBO allowed us to calculate the CBO, giving (-0.30 ± 0.14) eV and (-0.34 ± 0.06) eV, respectively. These values show that the CBO has a cliff-like behaviour which could be one of the reasons for the Voc limitation in the CdS/CZTS solar cells. [ABSTRACT FROM AUTHOR]

In this paper, CdSe nanocrystal dissolution in an aqueous solution was studied. It was found that light is a key factor affecting the dissolution of nanocrystals. In the presence of light, the electrons generated from CdSe nanocrystals reduce water to hydrogen and hydroxide ions (OH [?] ) while photo-generated holes oxidize CdSe to Cd2 + and elemental Se. The dissolution was accelerated in an acidic medium while moderate alkalinity (pH = 10.3) can slow down the dissolution possibly due to precipitation of nanocrystals. This study has strong implications for the use of these crystals in aqueous environments (bioimaging and dye-sensitized solar cells). [ABSTRACT FROM AUTHOR]

The implantation and growth of metal nanoparticles on graphene nanosheets (GNS) leads directly to severe damage to the regular structure of the graphene sheets, which disrupts the extended p conjugation, resulting in an impaired device performance. In this paper, we describe a facile approach for achieving the lossless formation of graphene composite decorated with tiny cadmium sulfide quantum dots (QDs) with excellent nonlinear optical properties by using benzyl mercaptan (BM) as the interlinker. The mercapto substituent of BM binds to the CdS QDs during their nucleation and growth process, and then the phenyl comes into contact with the GNS via the p-p stacking interaction. Using this strategy, CdS QDs with an average diameter of 3 nm are uniformly dispersed over the surface of graphene, and the resulting QD-graphene composite exhibits excellent optical limiting properties, mainly contributed by nonlinear scattering and nonlinear absorption, upon both 532 and 1064 nm excitations, in the nanosecond laser pulse regime. [ABSTRACT FROM AUTHOR]

The electronic structure of CdS nanorods doped with manganese ions in the magnetic field is calculated based on the effective-mass theory, the conduction and valence subbands are found to be non-degenerate in Mn-doped CdS nanorods, the split energies of the valence subbands increase as the increment of the concentration of manganese ions. The possible transitions between the six lowest conduction subbands and the eight highest valence subbands are presented, the optical circularly polarized properties of each transition are also labelled. Through the calculation, it is found that the optical transitions can be influenced by the concentration of manganese ions and the applied magnetic field, and the radiative intensity of the transition in Mn-doped CdS nanorods increases with the increase in the manganese ions. [ABSTRACT FROM AUTHOR]

Cd1-xZnxS nanocrystals are prepared by a co-precipitation method with different atomic fractions of Zn. The texture, structural transformation and optical properties with increasing x value in Cd1-xZnxS are studied with scanning electron microscopy, electron diffraction patterning, and absorption spectra respectively. Quantum confinement in a strained CdS/Cd1-xZnxS related nanodot with various Zn content values is investigated theoretically. Binding energies on exciton bound CdS/CdxZn1-xS quantum dot are computed, with consideration of the internal electric field induced by the spontaneous and piezoelectric polarizations, and thereby the interband emission energy is calculated as a function of the dot radius. The optical band gap from the UV absorption spectrum is compared with the interband emission energy computed theoretically. Our results show that the average diameter of composite nanoparticles ranges from 3 nm to 6 nm. The X-ray diffraction pattern shows that all the peaks shift towards the higher diffracting angles with an increase in Zn content. The lattice constant gradually decreases as the Zn content increases. The strong absorption edge shifts towards the lower wavelength region and hence the band gap of the films increases as the Zn content increases. The values of the absorption edge are found to shift towards the shorter wave length region and hence the direct band gap energy varies from 2.5 eV for the CdS film and 3.5 eV for the ZnS film. Our numerical results are in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

One-dimensional flexible solar cells were fabricated through vertical growth of ZnO nanowires on freestanding carbon fibers and subsequent deposition of CdS quantum dots (QDs). Under light illumination, excitons were generated in the CdS QDs and dissociated in the ZnO/CdS interface. Photoelectrochemical characterization indicates that fiber quantum dot-sensitized solar cells (QDSCs) could effectively absorb visible light and convert it to electric energy. The photoelectrochemical performance was enhanced after the deposition of a ZnS passivating layer on the CF/ZnO/CdS surface. The highest conversion efficiency of about 0.006% was achieved by the fiber QDSCs. A higher conversion efficiency was expected to be achieved after some important parameters and cell structure were optimized and improved. [ABSTRACT FROM AUTHOR]

CdS/TiO2 heterojunction film used as a photoanode has attracted much attention in the past few years due to its good visible light photocatalytic activity. However, CdS/TiO2 films prepared by conventional methods (successive ionic layer adsorption and reaction, chemical bath deposition and electrodeposition) show numerous grain boundaries in the CdS layer and an imperfect contact at the heterojunction interface. In this study, we designed a phase transformation method to fabricate CdS/TiO2 nanorod heterojunction films. The characterization results showed that the CdS layer with fewer grain boundaries was conformally coated on the TiO2 nanorod surface and the formation mechanism has been explained in this manuscript. Moreover, the prepared CdS/TiO2 films show a high photocatalytic activity and the photocurrent density is as high as 9.65 mA cm−2 at 0.80 V versus RHE. It may be attributed to fewer grain boundaries and a compact heterojunction contact, which can effectively improve charge separation and transportation. [ABSTRACT FROM AUTHOR]

A novel method of fabricating chemical bath deposited CdS thin films (CBD-CdS) by using electrodeposited CdS (ED-CdS) as a seed layer is reported. The resulting thin, compact, uniform and adherent seed-assisted CdS films (ED/CBD-CdS) show enhanced effective surface area compared to both ED-CdS and CBD-CdS. The phase of these CdS films was determined to be hexagonal. The fabricated ED/CBD-CdS films show higher photoelectrochemical (PEC) cell efficiency than either ED-CdS and CBD-CdS thin films. Carrier concentration and flat band potential values for ED/CBD-CdS systems are also found to be superior compared to both ED-CdS and CBD-CdS systems. [ABSTRACT FROM AUTHOR]

Manganese-doped CdS/ZnS quantum dots have been used as energy donors in a Förster-like resonance energy transfer (FRET) process to enhance the effective lifetime of organic fluorophores. It was possible to tune the effective lifetime of the fluorophores by about six orders of magnitude from the nanosecond (ns) up to the millisecond (ms) region. Undoped and Mn-doped CdS/ZnS quantum dots functionalized with different dye molecules were selected as a model system for investigating the multiple energy transfer process and the specific interaction between Mn ions and the attached dye molecules. While the lifetime of the free dye molecules was about 5 ns, their linking to undoped CdS/ZnS quantum dots led to a long effective lifetime of about 150 ns, following a non-exponential transient. Manganese-doped core–shell quantum dots further enhanced the long-lasting decay time of the dye to several ms. This opens up a pathway to analyse different fluorophores in the time domain with equal spectral emissions. Such lifetime multiplexing would be an interesting alternative to the commonly used spectral multiplexing in fluorescence detection schemes. [ABSTRACT FROM AUTHOR]

In this study, device modeling and simulation are conducted to explain the effects of each layer thickness and temperature on the performance of ZnO/CdS/CIS thin film solar cells. Also, the thicknesses of the CIS and CdS absorber layers are considered in this work theoretically and experimentally. The calculations of solar cell performances are based on the solutions of the well-known three coupling equations: the continuity equation for holes and electrons and the Poisson equation. Our simulated results show that the efficiency increases by reducing the CdS thickness. Increasing the CIS thickness can increase the efficiency but it needs more materials. The efficiency is more than 19% for a CIS layer with a thickness of 2 μm. CIS nanoparticles are prepared via the polyol route and purified through centrifugation and precipitation processes. Then nanoparticles are dispersed to obtain stable inks that could be directly used for thin-film deposition via spin coating. We also obtain x-ray diffraction (XRD) peak intensities and absorption spectra for CIS experimentally. Finally, absorption spectra for the CdS window layer in several deposition times are investigated experimentally. [ABSTRACT FROM AUTHOR]

The first-principles calculations based on density functional theory combined with cluster expansion techniques and Monte Carlo (MC) simulations were used to study the phase diagrams of both wurtzite (WZ) and zinc-blende (ZB) Cd1–xZnxS alloys. All formation energies are positive for WZ and ZB Cd1–xZnxS alloys, which means that the Cd1–xZnxS alloys are unstable and have a tendency to phase separation. For WZ and ZB Cd1–xZnxS alloys, the consolute temperatures are 655 K and 604 K, respectively, and they both have an asymmetric miscibility gap. We obtained the spatial distributions of Cd and Zn atoms in WZ and ZB Cd0.5Zn0.5S alloys at different temperatures by MC simulations. We found that both WZ and ZB phases of Cd0.5Zn0.5S alloy exhibit phase segregation of Cd and Zn atoms at low temperature, which is consistent with the phase diagrams. [ABSTRACT FROM AUTHOR]

We demonstrate that optical absorption spectra of CdS thin films in the visible/near ultraviolet range can be precisely described by four different contributions of electron transitions from Γ points of three branches of the valence band maxima (Γ7, Γ9, Γ7′,) to the lowest two minima in the conduction band (Γe, Γe′), in accordance with the theoretical results of the work (Lew Yan Voon et al 1996 Phys. Rev. B 53 10703). By using the method of successive extractions of different contributions in the absorption coefficient (α), four contributions have been found, attributed to the following electron transitions: (Γ7′  →  Γe), (Γ9  →  Γe), (Γ7  →  Γe) and (Γ7  →  Γe′). Corresponding bandgaps for films annealed at 400 °C in CdCl2 obtained in this work are 2.20 eV, 2.30 eV, 2.43 eV and 3.88 eV, that are close to the theoretical values for bulk CdS 2.24 eV, 2.28 eV, 2.43 eV and 3.8 eV. Bandgaps for as grown films are somehow higher because of the confinement effect in microcrystals of a smaller size. For the films annealed in air due to creation of Cd vacancies, the bandgap decreases down from the bulk values; thus, the values of bandgaps for films annealed at 400 °C in air are: 1.82 eV, 2.11 eV, 2.25 eV and 3.87 eV. Strong absorption onset, considered as the fundamental absorption edge, corresponds to direct allowed transitions (Γ7  →  Γe′) at photon energies of about 3.8 eV. Absorption due to direct allowed transitions (Γ7  →  Γe) at photon energies of about 2.3 eV are usually reported as the optical bandgap of CdS saturates at relatively low values α  ≈  5   ×   104 cm−1. [ABSTRACT FROM AUTHOR]

A series of CdS/Si heterostructures were prepared through growing B-doped CdS thin films on silicon nanoporous pillar array (Si-NPA) by a chemical bath deposition (CBD) method. The experimental data show that B-doping concentration of CdS thin films could be tuned effectively through controlling the mole ratio of [B]/[Cd] of the initial CBD solution without causing obvious variation of the crystal phase and surface morphology of CdS/Si-NPA. Both the electrical rectification and photovoltaic parameters of CdS/Si-NPA show strong dependence upon B-doping concentration, and the optimal characteristics are achieved for the samples prepared with [B]/[Cd] = 0.01. Compared with CdS/Si-NPA solar cells without B-doping, an increment over 300 times for energy conversion efficiency is realized. The mechanism for the efficiency increment is analyzed based on the effect of B-doping on the band structure of CdS/Si-NPA. These results indicate that B-doping might be an effective path for promoting the device performance of solar cells based on CdS/Si-NPA. [ABSTRACT FROM AUTHOR]

Excitons are one of the most important fundamental quasi-particles, and are involved in a variety of processes forming the basis of a wide range of opto-electronic and photonic devices based on II–VI semiconductor nanowires and nanobelts, such as light-emitting diodes, photovoltaic cells, photodetectors and nanolasers. A clear understanding of their properties and unveiling the potential engineering for excitons is of particular importance for the design and optimization of nanoscale opto-electronic and photonic devices. Herein, we present a comprehensive review on discussing the fundamental behaviours of the excitons in one-dimensional (1D) II–VI semiconductor nanomaterials (nanowires and nanobelts). We will start with a focus on the unique properties (origin, generation, etc) and dynamics of excitons and exciton complexes in the II–VI semiconductor nanowires and nanobelts. Then we move to the recent progress on the excitonic response in 1D nanomaterials and focus on the tailoring and engineering of excitonic properties through rational controlling of the physical parameters and conditions, intrinsically and extrinsically. These include (1) exciton–exciton interaction, which is important for 1D nanomaterial nanolasing; (2) exciton–phonon interaction, which has interesting applications for laser cooling; and (3) exciton–plasmon interaction, which is the cornerstone towards the realization of plasmonic lasers. The potential of electric field, morphology and size control for excitonic properties is also discussed. Unveiling and controlling excitonic properties in II–VI semiconductor nanowires and nanobelts would promote the development of 1D nanoscience and nanotechnology. [ABSTRACT FROM AUTHOR]

UV-VIS photodetectors using an interdigital configuration, with zinc oxide (ZnO) and cadmium sulfide (CdS) semiconductors deposited by pulsed laser deposition, were fabricated with a maximum processing temperature of 100 °C. Without any further post-growth annealing, the photodetectors are compatible with flexible and transparent substrates. Aluminum (Al) and indium tin oxide (ITO) were investigated as contacts. Focusing on underwater communications, the impact of metal contact (ITO versus Al) was investigated to determine the maximum responsivity using a laser with a 405 nm wavelength. As expected, the responsivity increases for reduced metal finger separation. This is a consequence of reduced carrier transit time for shorter finger separation. For ITO, the highest responsivities for both films (ZnO and CdS) were ∼3 A W−1 at 5 V. On the other hand, for Al contacts, the maximum responsivities at 5 V were ∼0.1 A W−1 and 0.7 A W−1 for CdS and ZnO, respectively. [ABSTRACT FROM AUTHOR]

Thin film transistors (TFTs) with a bottom-gate configuration were fabricated using a photolithography process with chemically bath deposited (CBD) cadmium sulfide (CdS) films as the active channel. Thermal annealing in hydrogen was used to improve electrical stability and performance of the resulting CdS TFTs. Hydrogen thermal treatments results in significant VT instability (VT shift) improvement while increasing the Ion/Ioff ratio without degrading carrier mobility. It is demonstrated that after annealing VT shift and Ion/Ioff improves from 10 V to 4.6 V and from 105 to 109, respectively. Carrier mobility remains in the order of 14.5 cm2 V s−1. The reduced VT shift and performance is attributed to a reduction in oxygen species in the CdS after hydrogen annealing, as evaluated by Fourier transform infrared spectroscopy (FTIR). [ABSTRACT FROM AUTHOR]

The synthesis of water-soluble quantum dots (QDs) in aqueous phase has received much attention recently. To date various kinds of QDs such as CdTe, CdSe, CdTe/CdS and CdSe/ZnS have been synthesized by aqueous methods. However, generally poor-quality QDs (photoluminescent quantum yield (PLQY) lower than 30%) are obtained via this method and the 3-mercaptopropionic acid stabilizer is notorious for its toxicity and awful odor. Here we introduce a novel thiol ligand, N-acetyl-l-cysteine, as an ideal stabilizer that is successfully employed to synthesize high-quality CdTe/CdS/ZnS QDs via a simple aqueous phase. The core/shell/shell structures of the CdTe/CdS/ZnS QDs were verified by x-ray photoelectron spectroscopy, energy dispersive x-ray spectroscopy, x-ray powder diffraction and transmission electron microscopy. These QDs not only possess a high PLQY but also have excellent photostability and favorable biocompatibility, which is vital for many biological applications. This type of water-dispersed QD is a promising candidate for fluorescent probes in biological and medical fields. [ABSTRACT FROM AUTHOR]

The effect of oxygen adsorption and desorption on the photoconducting gain, spectral dependence of quantum efficiency and optical switching was studied in CdS nanorods with diameters of 20, 50 and 100 nm. These were found to have an increasing degree of crystallinity and consequently a decreasing overall density of defects leading to better stoichiometry being maintained. These properties, along with the complete depletion of electrons from the nanorod volume and oxygen induced passivation of defects, resulted in: (i) a large difference in photoconducting gain, (ii) reversal of the photoconducting behaviour on annealing in oxygen and a vacuum, and (iii) onset of an absorption edge in the spectral dependence of quantum efficiency on oxygen annealing in 20 nm diameter nanorods in comparison to the normal photoconducting behaviour expected from an n-type semiconductor observed in 50 and 100 nm diameter nanorods. Single CdS nanorod devices show stable I–V characteristics in dark and light conditions under a wide temperature range and the effect of oxygen and vacuum annealing can be clearly observed. The oxygen induced defect passivation observed in this study is important for the application of compound semiconductor nanorods in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Bioconjugated CdS nanoparticles capped with L-cysteine molecules are prepared by an aqueous route. A new source of sulfur that is a complex of hydrazine hydrate-sulfur is used to develop the aqueous synthesis of these nanoparticles. The change in volume ratio of sulfur and cadmium ions with a fixed molarity of capping molecules, as prepared colloids exhibits different colours. These nanoparticles are characterized by optical absorption, photoluminescence, FTIR, x-ray diffraction and transmission electron microscopic measurements. It is observed that the present technique yields nanoparticles that are spherical in shape whose size ranges from 1.7 to 3.39 nm (estimated from optical absorption). The resulting colloids are highly stable (for more than a few months) and exhibit high quantum yield for fluorescence (close to 34%). This demonstrates that the present route of synthesis is simple and easily scalable to prepare highly fluorescent and biologically important nanoparticles of CdS. [ABSTRACT FROM AUTHOR]

Bulk heterojunction (BHJ) photovoltaic (PV) cells have been prepared by vacuum co-deposition of inorganic cadmium sulfide (CdS) and organic zinc phthalocyanine (PcZn) materials. Characteristics of the BHJ cells were compared with the cells based on vacuum evaporated bilayer CdS/PcZn heterojunctions, and it was found that the BHJ structure possesses higher PV performance due to higher interface area at which excitons can dissociate. Variation of the component ratio in the BHJ devices and comparison of their photocurrent spectra allowed us to distinguish the contribution of CdS, CdS/PcZn interface and PcZn to the PV response. The mechanism of charge transport was attributed to the model of space-charge-limited current with traps; however, the concentration of traps was different in the bilayer and BHJ structures. [ABSTRACT FROM AUTHOR]