High-yield synthesis of quantum-confined CdS nanorods using a new dimeric cadmium(II) complex of S-benzyldithiocarbazate as single-source molecular precursor

A convenient solvothermal single-source route has been developed for the bulk synthesis of CdS nanorods using new air stable dimeric cadmium(II) complex of S-benzyldithiocarbazate, [Cd(PhCH₂SC(S)NHNH₂)Cl₂]₂, at a relatively low temperature. The decomposition of the precursor was made by heating at 160 °C in hexamethylenediamine (HMDA) to give amine capped CdS nanocrystals having yield ca. 90%; nano-dimensional rods are clearly visible in transmission electron microscope (TEM). The nanorods have been further characterized by X-ray diffraction (XRD), energy dispersed X-ray spectroscopy (EDX), FTIR and optical measurements. The structure of precursor was also established by single crystal X-ray crystallography.     

Cubic-BN nanocrystals synthesis by pulsed laser induced liquid–solid interfacial reaction

Cubic boron nitride (c-BN) nanocrystals have been synthesized by pulsed laser induced liquid–solid interfacial reaction. It is shown that the diameters of the prepared quasi-spherical c-BN nanocrystals vary from 30 to 80 nm via transmission electron microscopy (TEM). The 2θ values of the X-ray diffraction (XRD) peaks of the resultant c-BN nanocrystals are 43.16°, 74.16°, 90.08° and 136.1°, respectively, corresponding to the (1 1 1), (2 2 0), (3 1 1) and (3 3 1) crystalline planes of a c-BN phase. Fourier transform infrared (FTIR) spectroscopy has also been used to characterize the structure of boron nitride. The formation of c-BN nanocrystals upon pulsed laser ablation at the liquid–solid interface is discussed in detail.     

Mesoporous cadmium bismuth niobate (CdBi_2Nb_2O_9) nanospheres for hydrogen generation under visible light

Herein, we report visible light active mesoporous cadmium bismuth niobate(CBN) nanospheres as a photocatalyst for hydrogen(H_2) generation from copious hydrogen sulfide(H_2S). CBN has been synthesized by solid state reaction(SSR) and also using combustion method(CM) at relatively lower temperatures.The as-synthesized materials were characterized using different techniques. X-ray diffraction analysis shows the formation of single phase orthorhombic CBN. Field emission scanning electron microscopy and high resolution-transmission electron microscopy showed the particle size in the range of ~0.5–1 μm for CBN obtained by SSR and 50–70 nm size nanospheres using CM, respectively. Interestingly, nanospheres of size 50–70 nm self assembled with 5–7 nm nanoparticles were observed in case of CBN prepared by CM.The optical properties were studied using UV–visible diffuse reflectance spectroscopy and showed band gap around ~3.0 eV for SSR and 3.1 eV for CM. The slight shift in band gap of CM is due to nanocrystalline nature of material. Considering the band gap in visible region, the photocatalytic activity of CBN for hydrogen production from H_2S has been performed under visible light. CBN prepared by CM has shown utmost hydrogen evolution i.e. 6912 μmol/h/0.5 g which is much higher than CBN prepared using SSR.The enhanced photocatalytic property can be attributed to the smaller particle size, crystalline nature,high surface area and mesoporous structure of CBN prepared by combustion method. The catalyst was found to be stable, active and can be utilized for water splitting.     

Cauliflower-like CdS microspheres composed of nanocrystals and their physicochemical properties

Cauliflower-like cadmium sulfide (CdS) microspheres composed of nanocrystals have been successfully synthesized by a hydrothermal method using poly(ethylene glycol) (PEG) as the template coordination agent and characterized by a variety of methods. Our experiments confirmed that the size of the CdS microspheres could be easily modified by controlling the chain length of PEG. Powder X-ray diffraction and Raman spectroscopy measurements revealed the cubic structure of the CdS microspheres; morphological studies performed by HR-SEM and HR-TEM methods showed the cauliflower-like structure of the synthesized CdS microspheres. Each microsphere was identified to be created by the self-assembly of CdS nanocrystals and is attributed to the oriented aggregation of the CdS nanocrystals around a polymer-Cd(2+) complex spherical framework structure. X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray (EDX) analysis confirmed the stoichiometries of the CdS microspheres. Diffuse reflectance spectrum (DRS) measurements showed that increasing the PEG chain length increased the band gap value of the CdS microspheres slightly, from 1.99 to 2.06 eV. The cauliflower-like CdS microspheres could be applied to photocatalytic degradation studies.     

Synthesis of nanocrystalline CdS from cadmium(II) complex of S-benzyl dithiocarbazate as a precursor

The single X-ray crystal structure of the cadmium(II)–S-benzyl dithiocarbazate (SBDTC) complex, [Cd(SBDTC)Cl₂]₂, is reported. The compound has been found to be an effective single-source precursor for the preparation of CdS nanocrystals (NCs) via solvothermal method. CdS NCs including spheres and rods were prepared at a relatively low temperature by thermolysis of the precursor using chelating solvent like ethylene glycol (EG), ethylenediamine (EN), hydrazine hydrate (HH) or in a mixture of EG and EN. The influence of solvent, temperature and reaction time was investigated on the size and morphology of the NCs. Use of EG afforded spherical CdS NCs while EN uniquely yielded rod-shaped NCs, and mixture of spheres and rods are obtained from the mixture of EN and EG with a ratio 0.2 (v/v: EN/EG). UV–visible spectroscopy established pronounced quantum confinement with enhanced band gap and XRD analyses revealed hexagonal crystal phase for so obtained CdS NCs. The NCs were also characterized by transmission electron microscopy (TEM), photoluminescence spectroscopy (PL), energy-dispersive X-ray spectroscopy (EDS) and FTIR. The possible formation mechanism for the anisotropic growth of NCs was also discussed.     

Ag2S quantum dot-sensitized solar cells

We present a new photosensitizer – Ag₂S quantum dots (QDs) – for solar cells. The QDs were grown by the successive ionic layer adsorption and reaction deposition method. The assembled Ag₂S-QD solar cells yield a best power conversion efficiency of 1.70% and a short-circuit current of 1.54 mA/cm² under 10.8% sun. The solar cells have a maximal external quantum efficiency (EQE) of 50% at λ = 530 nm and an average EQE of ～ 42% over the spectral range of 400–1000 nm. The effective photovoltaic range covers the visible and near-infrared spectral regions and is ～ 2–4 times broader than that of the cadmium chalcogenide systems — CdS and CdSe. The results show that Ag₂S QDs can be used as a highly efficient and broadband sensitizer for solar cells.     

Studies of nanoparticulate cadmium sulfide in amphiphilic polymaleic acid octadecanol ester Langmuir-Blodgett films

The reversed micelles of CdS nanoparticles capped with oligomer–polymaleic acid octadecanol ester (PMAO) were synthesized by a colloid chemical method in an aqueous system. The chemical ratio of PMAO between the carboxylic group and the hydrocarbon chain was controlled to 1.5 : 1. The PMAO-capped CdS nanoparticles were transferred on to CaF₂ and Si substrates by the Langmuir–Blodgett (LB) technique. Surface pressure–area isotherms indicated that PMAO-capped CdS nanoparticles could form a stable monolayer on the water subphase. The measurement of FTIR and small angle X-ray diffraction showed that the reversed micelles of PMAO-capped CdS nanoparticles were formed with a uniform size and order in LB films. The photoluminescence properties of PMAO-capped CdS both in the solution and in the LB film indicated that the photoluminescence peaks of reversed micelles obviously changed as a result of the energy transfer from PMAO to CdS and the interaction between clusters.     

Synthesis of hybrid solar cells using CdS nanowire array grown on conductive glass substrates

High-density CdS nanowire (NW) arrays were successfully grown on fluorine-doped tin oxide (FTO)-coated glass substrates by vapor–liquid–solid (VLS) mechanism at a remarkably reduced temperature of ～450 °C. Bi catalyst layer and polyvinyl alcohol (PVA) played a major role in the low-temperature synthesis of high-quality CdS NW arrays. CdS NWs were defect free single crystalline Wurtzite crystals and they were 50–100 nm and 2–5 μm in diameter and length, respectively. CdS NWs were combined with poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), a conjugated polymer to form organic–inorganic hybrid structures. The UV–visible light absorption and emission behavior of MEH-PPV/CdS hybrids was investigated and their potential to be used as photovoltaic cells was demonstrated.     

Direct electrochemistry study of glucose oxidase on Pt nanoparticle-modified aligned carbon nanotubes electrode by the assistance of chitosan–CdS and its biosensoring for glucose

Aligned carbon nanotubes (ACNTs) electrode has been developed for the direct protein electrochemistry and enzyme-biosensor study involving two types of nanoparticles. Pt nanoparticles (Pt_nano) were electro-modified on the ACNTs’ each tube, greatly increasing the electrode surface area for locating protein and also its electronic transfer ability. Glucose oxidase (GOD) with chitosan (CS) and CdS nanoparticles electrochemically coated on each tube of ACNTs–Pt_nano by the electrodeposition reaction of CS when pH value passing its pKa. The CdS nanoparticles between ACNTs electrode and GOD have stimulated the GOD’s direct electron transfer during its redox reaction of FAD/FADH₂. The CS–GOD–CdS/ACNTs–Pt_nano electrode also offer sensitive response to the substrate of glucose with detection limit of 46.8 μM (S/N = 3) and apparent Michaelis–Menten constant of 11.86 mM.     

CdS thin film: Synthesis and characterization

CdS thin films have been deposited by dip technique using succinic acid as a complexing agent. The structural characterizations of films have been studied by X-ray diffraction. X-ray diffraction pattern prove crystallinity of the deposited films that crystallize in the cubic phase of CdS. The films show high absorption and band gap value which were found to be 2.58 eV. The specific conductivity of the film was found to be in the order of 10^?7 (Ω cm)^?1.     

Greatly enhanced electrochemiluminescence of CdS nanocrystals upon heating in the presence of ammonia

CdS nanocrystals (NCs) usually exhibit very weak electrochemiluminescence (ECL) emission. It is showed that when CdS NCs were treated by heating in the presence of ammonia (heated-CdS–NH₃), greatly enhanced ECL was observed. The ECL of the heated-CdS–NH₃ modified glassy carbon electrode (heated-CdS–NH₃/GCE) in phosphate buffer solution (pH 7.0) containing 0.1 M K₂S₂O₈ was ca. 310 times higher than that of CdS/GCE. The treatment caused the changes in the morphology and surface electronic structure of CdS NCs, which facilitated the reduction process of CdS, consequently improved the quantity of the excited states (CdS*), leading to enormous enhancement in ECL.     

Influence of acid–base properties of cobalt–molybdenum catalysts supported on magnesium orthophosphates in isomerization of 3,3-dimethylbut-1-ene

Synthesis and physico-chemical characterization of a pure magnesium phosphate (MgP) prepared by coprecipitation, and MgP modified by introduction of cobalt–molybdenum (4–12 wt.% of MoO₃ with the Co/Mo ratio fixed at 0.5) have been carried out. The structural properties of these catalysts were characterized by X-ray diffraction, their textural properties were determined by N₂ adsorption–desorption isotherms and the dispersion of cobalt–molybdenum was studied by XPS spectroscopy. Their acid properties have been investigated by in situ FT-IR spectroscopy of adsorbed molecules, often, 2,6-dimethylpyridine (pK_a = 6.7), pyridine (pK_a = 5.3). Co–Mo incorporation leads to a modification in the MgP acid–base properties, especially on the acid sites type and number. Thus, lower loading of cobalt–molybdenum species decreased the number of strong Lewis acid sites whereas higher loading increased it. It was found that Lewis acid sites on magnesium phosphates play an important role in the isomerization of 3,3-dimethylbut-1-ene.The 3,3-dimethylbut-1-ene (33DMB1) conversion increases with the reaction temperature from 493 to 653 K for MgP, but decreases after 573 K for MgP supported by Co–Mo. A linear relationship between both types of acid sites and conversion values was found. The deactivation of the catalysts appears at high reaction temperature (>573 K).     

Synthesis of covellite (CuS) from the elements

A one-step, corrosion-assisted reaction was developed to synthesize copper sulfide (CuS) from elemental copper and sulfur in water at 60 °C. The as-prepared polycrystalline CuS consists of polyhedral-shaped 2–3 μm crystallites. CuS forms by the oxidation of copper metal in the presence of sulfur, whereas in the presence of water, a continuous solid-state reaction occurs without passivation by the product.     

A facile synthetic strategy for mesoporous crystalline copper–polyaniline composite

A facile and novel strategy for preparing mesoporous crystalline copper–polyaniline composite is reported wherein the reaction is carried out at room temperature using copper nitrate as the oxidizing agent and methanol as the solvent. The composite obtained as a precipitate has been characterized using UV–visible absorption spectroscopy (UV–vis), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption–desorption method, Barrett–Joyner–Halenda (BJH) method, Brunauer–Emmett–Teller method (BET) and thermogravimetric analysis (TGA). The XRD studies in conjunction with the BJH method reveals that the composite has crystalline nature with a mesoporous structure and has a diameter of 3.5 nm. The specific surface area of copper–polyaniline composite is estimated to be as high as 63.2 m² g^?1 using the BET surface area plot. The characterization of the filtrate indicates the presence of pernigraniline with a very small weight percent of copper.     

Characterization of CdS nanoparticles formed and aggregated in stearic acid Langmuir–Blodgett films by atomic force microscopy

Alternate films, which are composed of stearic acid and CdS nanoparticles were synthesized by exposing Langmuir–Blodgett (LB) films of cadmium stearate (CdSt₂) to H₂S gas at a pressure of 1 Torr. The changes of surface morphology of film with the increased reaction time were directly observed by atomic force microscopy for the first time. Before being exposed to H₂S, the surface of CdSt₂ LB film was homogeneous from microscale down to nanoscale, and it was observed that CdSt₂ molecules formed a well orderly rectangular herringbone lattice structure on the molecular scale. However, after being exposed to H₂S the ordered CdSt₂ molecules gradually changed into a disordered state, and eventually the LB film surface became rough with the apparent feature of bulk structures on the nanoscale. This change in the morphology can be attributed to the aggregation of buried CdS nanoparticles within LB films, which has been confirmed by a structured UV–visible absorption spectrum where the absorption edge is red-shifted about 0.7 eV with respect to bulk CdS. Finally, the aggregation mechanism of CdS in the LB film was analyzed.     

Influence of crystal size on the electron–phonon coupling in ZnO nanocrystals investigated by Raman spectroscopy

We have synthesized ZnO nanocrystals of different sizes (25–41 nm) using the sol–gel method and characterized them using different techniques such as: transmission electron microscopy (TEM) and X-ray diffraction (XRD). Raman spectra of different sizes of ZnO nanocrystals were recorded at two excitation wavelengths, 514 and 647 nm, in the spectral range 300–1200 cm⁻¹. The vibrational modes were assigned on the basis of group theory analysis. The influence of mean crystallite size on the strength of the electron–phonon coupling is experimentally estimated by the variation of relative intensities of second order Raman band and the first order Raman band for ZnO nanocrystals of different sizes. We found that the intensity ratio of the 2E₂ and 1E₂ Raman bands decreases almost linearly for both excitation wavelengths with decreasing crystallite size, which reveals that the Fröhlich interaction plays a dominant role in the electron–phonon coupling of the ZnO nanocrystals.     

Chemical bath deposition of CdS quantum dots on vertically aligned ZnO nanorods for quantum dots-sensitized solar cells

Formation of CdS quantum dots (Q dots) on the vertically aligned ZnO nanorods electrode was carried out by chemical bath deposition. The diameter and thickness of ZnO nanorods are ～100–150 nm and ～1.6 μm, respectively, and CdS Q dots on ZnO nanorods have a diameter of smaller than 15 nm. In application of the Q dots-sensitized solar cells, composite film exhibited a power conversion efficiency of 0.54% under air mass 1.5 condition (80 mW/cm²), and incident-photon-to-current conversion efficiency showed 18.6%.     

Microwave-radiated synthesis of gold nanoparticles/carbon nanotubes composites and its application to voltammetric detection of trace mercury(II)

Gold nanoparticles/carbon nanotubes (Au-NPs/CNTs) composites were rapidly synthesized by microwave radiation, and firstly applied for the determination of trace mercury(II) by anodic stripping voltammetry (ASV). The structure and composition of the synthesized Au-NPs/CNTs nanocomposites were characterized by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), UV–vis absorption spectroscopy and cyclic voltammetry. Au-NPs/CNTs nanocomposites modified glassy carbon electrode (Au-NPs/CNTs/GCE) exhibited excellent performance for Hg(II) analysis. A wide linear range (5 × 10⁻¹⁰–1.25 × 10⁻⁶ mol/L) and good repeatability (relative standard deviation of 1.84%) were obtained for Hg(II) detection. The limit of detection was found to be 3 × 10⁻¹⁰ mol/L (0.06 μg/L) at 2 min accumulation, while the World Health Organization’s guideline value of mercury for drinking water is 1 μg/L, suggesting the proposed method may have practical utility.     

Influence of Calcination on the Properties of Nickel Oxide-Samarium Doped Ceria Carbonate (NiO-SDCC) Composite Anodes

Apart from its composition, the starting powder properties such as particle size potentially affect the triple phase boundary and the electrochemical performance. Calcination process has been identified as one of the factors that influence the particle size of the composite anode powders. This study investigates the correlation between calcination temperature and properties (i.e., chemical, physical, and thermal) of NiO–samarium-doped ceria carbonate (SDCC) composite anodes. NiO–SDCC composite anode powder was prepared with NiO and SDCC through high-energy ball milling. The resultant composite powder was subjected to calcination at various temperatures ranging from 600 °C to 800 °C. Characterizations of the composite anode were performed through X-ray diffraction (XRD), Fourier transform infrared spectroscopy, energy dispersive spectroscopy, field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), dilatometry, and porosity measurements. The composite anodes exhibited good chemical compatibility during XRD after calcination and sintering. The FTIR result verified the existence of carbonates in all the composite anodes. The increment in calcination temperature from 600 °C to 800 °C resulted in the growth of nanoscale particles, as evidenced by the FESEM micrographs and crystallite size. Nonetheless, the porosity obtained remained within the acceptable range for a good anodic reaction (20% to 40%). The TGA results showed gradual mass loss in the range of 400 °C to 600 °C (within the low-temperature solid oxide fuel cell region). The composite anodes calcined at 600 °C and 700 °C revealed a good thermal expansion coefficient that matches that of the SDCC electrolyte.     

Thin films composed of irregular micro-block arrays of closely packed CdS nanoparticles for enhanced photoelectrochemical performance

CdS is a very important semiconductor, and various micro-/nano-structured forms of CdS have been fabricated with the aim of improving its photoelectrochemical performance. We report here for the first time the preparation of a CdS film consisting of irregular micro-block arrays of closely packed CdS nanoparticles. It performs outstandingly well as a photoanode because it possesses the advantages of both arrays and nanoparticles. This CdS film is prepared simply by a combination of reaction and assembly at the gas/liquid interface (RAG/L) with successive ionic layer adsorption and reaction (SILAR), requiring no templates or expensive equipment. In this approach, the nanopores in the film of loosely aggregated CdS nanoparticles produced by RAG/L are filled by CdS nanoparticles via SILAR, forming a compact CdS film. Network micro-cracks form in the compact CdS film due to calcination caused by differential thermal expansion compared with the substrate, and these cut the CdS film into irregular micro-block arrays. This micro-/nano-structure in the prepared CdS film improves its capacity for visible light absorption, facilitates the generation/separation of excited charges, and enhances mass transfer. In an alkaline solution of methanol, the prepared CdS film exhibits the highest saturation photocurrent density (6.5 mA cm^− 2) ever reported on CdS-based photoanodes under visible light illumination.