CdS nanoparticles loaded on porous poly-melamine–formaldehyde polymer for photocatalytic dye degradation

CdS nanoparticles were loaded on a highly porous polymer of poly-melamine–formaldehyde (PMF) by a simple co-precipitation approach. Benefiting from the high specific surface area of PMF of 943 m² g^?1, the obtained CdS/PMF composite can adsorb dye molecules efficiently, which favors the subsequent photocatalytic dye degradation process. Typically, 99% of Rhodamine B could be degraded over the optimized CdS/PMF sample after 3 h visible light irradiation. Moreover, the CdS/PMF sample displays reasonable stability during the recycle runs, indicating its potential application for organic pollutants removal by photocatalysis.     

Surface-Modified CdS/ZnO Material: Single-Reactor Synthesis and Mechanism of Formation in Aqueous Solution

Method of chemical precipitation from aqueous solutions was used to cover the surface of polycrystalline ZnO nanotubes with a nanostructured CdS layer. The thus synthesized CdS/ZnO composite material was studied by the methods of X-ray diffraction analysis, electron microscopy, and optical spectroscopy. The fundamental time-related aspects of the process of CdS formation on the ZnO surface were examined. It was found that the amount of deposited CdS nanoparticles is independent of the deposition duration. The morphological specific features of ZnO nanotubes are preserved upon a prolonged keeping of ZnO in solution. The photocatalytic activity of CdS/ZnO under visible and UV light was examined in the reaction of hydroquinone oxidation. A possible mechanism of how the CdS/ZnO composite is formed in an aqueous solution in the course of growth of a layer constituted by CdS nanoparticles on the surface of ZnO nanotubes is suggested on the basis of the experimental data. It is demonstrated that the chemical-precipitation method can be used to obtain surface-active composite materials that are photoactive in the visible spectral range.     

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.     

Mechanism of the formation of photosensitive nanostructured TiO<Subscript>2</Subscript> with low content of CdS nanoparticles

A method for synthesizing a CdS/TiO₂ composite material, active in the visible region, was described. The CdS/TiO₂ composite was obtained by the sol–gel synthesis of nanostructured TiO₂ in a medium of a stable colloidal solution of CdS nanoparticles. The TiO₂ matrix produced by the sol–gel process is amorphous and contains a nanocrystalline anatase phase, the content of which depends on the Ti(OBu)₄ hydrolysis rate. The content of CdS nanoparticles forming in the colloidal solution and participating in the TiO₂ matrix sensitization is determined by the initial CdS: Ti(OBu)₄ ratio. Although the content of CdS nanoparticles in the composite is low (no more than 3 wt %), the composite demonstrates catalytic activity in the visible region, thus proving the possibility of reducing the content of toxic CdS nanoparticles in the TiO₂ matrix without decreasing the photosensitivity of the CdS/TiO₂ composite.     

Construction of inorganic nanoparticles by micro-nano-porous structure of cellulose matrix

In our previous work, the CdS nanoparticles/cellulose films exhibited significantly high photocatalytic H₂ production efficiency under visible light irradiation than the ordinary CdS photocatalyst. In present paper, the CdS nanoparticles were synthesized in situ in pores of the regenerated cellulose substrate and the porous structure of cellulose, formation of the CdS nanoparticles and interactions between CdS and cellulose matrix in the composite films were investigated deeply. The experimental results indicated that the micro-nano-porous structure of the cellulose matrix could be used easily to create inorganic nanoparticles, which supplied not only cavities for the formation of nanoparticles, but also a shell (semi-stiff cellulose molecules support the pore wall) to protect their nano-structure. When the cellulose films with porous structure at wet state were immersed into inorganic ions solution, the ions interacted immediately with the –OH groups of cellulose, and then transformed into inorganic composite via another treatment, finally inorganic nanoparticles formed during the dry. The pore size of the cellulose matrix decreased from 180 nm (at wet state) to about 18 nm (at dry state), leading to the formation of nanoparticles. The results revealed that the CdS nanoparticles with a mean particle diameter about 6 nm were dispersed well, and were immobilized tightly in the cellulose matrix, resulting in a portable photocatalyst with high efficiency for photocatalytic for H₂ evolution. This is simple and “green” pathway to prepare the organic–inorganic hybrid materials.     

Preparation and Electromagnetic Properties of Composites of Hollow Glass Microspheres Coated with NiFe2O4 Nanoparticles

"The composites of hollow glass microspheres coated with NiFe2O4 nanoparticles were prepared using polyacrylamide gel method. The structural characteristics, morphology and electromagnetic properties of the composite powders with different weight percent of glass microspheres (15%, 40%, and 65%) were obtained by X-ray diffraction, scanning electron microscope, infrared spectroscopy and HP8510 network analyzer. The results indicated that the phase structure of composite powders was the mixtures of nickel ferrite, quartz, and mullite. The peak intensity for nickel ferrite decreased rapidly and for mullite increased remarkably with the increasing amount of microspheres. A pure spinel structure of NiFe2O4 formed on the glass microspheres at 600 oC. A uniform and continuous NiFe2O4-coating was obtained when the content of microspheres was 40%. A great amount of NiFe2O4 particle size is less than 80 nm. The composite with a content of 40% microspheres exhibits better dielectric and magnetic loss properties which are useful to absorb more electromagnetic wave. It can be a kind of good and light electromagnetic wave absorbing material in the X-band."     

内嵌硫化镉与上转换纳米颗粒的二氧化钛复合纳米管用于近红外光驱动光催化

由于近红外光在太阳光谱中占44%,因此,近红外光驱动的光催化剂的研制具有十分重要的意义.上转换发光材料可将低能量的近红外光子转换为高能光子,这种高能光子可以通过构建荧光共振转移系统将能量转移并活化量子效率较高的半导体材料,对于太阳能的转化利用具有潜在的应用前景.在本文中,通过胶体化学的过程在电纺丝制备的内嵌CdS纳米颗粒以及上转换荧光纳米颗粒(UCNPs)的二氧化硅复合纳米纤维表面外延生长一层二氧化钛层,通过高温煅烧得到二氧化钛复合纳米管.我们通过二氧化硅结构将CdS纳米颗粒与上转换荧光纳米颗粒紧紧束缚在一起,实现较高的荧光共振能量转移.而且,选择β-NaYF4:Yb(30%),Tm(0.5%)@NaYF4:Yb(20%),Er(2%)作为纳米能量转换器,替代以前研究工作中使用的β-NaYF4:Yb(30%),Tm(0.5%)或者β-NaYF4:Yb(30%),Tm(0.5%)@NaYF4纳米颗粒,来进一步提高近红外光的转换效率.通过透射电子显微镜照片很清楚的观察到制备的TiO2复合纳米管内部内嵌有大量的CdS与上转换纳米颗粒.通过X-射线衍射以及X-射线光电子能谱能仪器对产物的物相以及表面的化学组成进行了细致的表征.结果显示,通过本实验方法已经成功获得了TiO2复合纳米管.用稳态与瞬态荧光仪研究了最终样品的荧光性质.研究结果揭示,与上转换纳米颗粒以及二氧化硅复合纳米纤维相比,复合二氧化钛纳米管可以将上转换荧光纳米颗粒的(UV-Vis)部分荧光完全淬灭了.特别是,铒离子的荧光(650 nm)也被有效淬灭转移,说明本研究采用β-NaYF4:Yb(30%),Tm(0.5%)@NaYF4:Yb(20%),Er(2%)纳米能量转换器,可以提高近红外光的转换效率,紫外-可见吸收光谱证实,这种二氧化钛纳米管在紫外-可见光区中的吸收光谱与β-NaYF4:Yb(30%),Tm(0.5%)@NaYF4:Yb(20%),Er(2%)纳米颗粒的荧光光谱具有较大的重叠,使得上转换荧光纳米颗粒与CdS以及二氧化钛组分之间的荧光共振转移的效率大大提高,进而会显著提高光催化的效果.以罗丹明染料作为污染物为模型,我们研究了罗丹明染料在氙灯下或者近红外光光照下的光催化分解实验.研究结果表明,90%的罗丹明染料分子在20 min内就被降解掉,效率高于其它的近红外光催化剂.上转换荧光纳米颗粒的能量转换效率可以得到大幅度提高,本研究工作中制备的光催化剂利用太阳能的效率将会得到极大提高,在未来为能源危机以及环境保护提供一种可供选择的方法与技术.     

Ultrasensitive mercury(II) ion detection by europium(III)-doped cadmium sulfide composite nanoparticles

With the biomolecule glutathione (GSH) as a capping ligand, Eu³⁺-doped cadmium sulfide composite nanoparticles were successfully synthesized through a straightforward one-pot process. An efficient fluorescence energy transfer system with CdS nanoparticles as energy donor and Eu³⁺ ions as energy accepter was developed. As a result of specific interaction, the fluorescence intensity of Eu³⁺-doped CdS nanoparticles is obviously reduced in the presence of Hg²⁺. Moreover, the long fluorescent lifetime and large Stoke's shift of europium complex permit sensitive fluorescence detection. Under the optimal conditions, the fluorescence intensity of Eu³⁺ at 614 nm decreased linearly with the concentration of Hg²⁺ ranging from 10 nmol L⁻¹ to 1500 nmol L⁻¹, the limit of detection for Hg²⁺ was 0.25 nmol L⁻¹. In addition to high stability and reproducibility, the composite nanoparticles show a unique selectivity towards Hg²⁺ ion with respect to common coexisting cations. Moreover, the developed method was applied to the detection of trace Hg²⁺ in aqueous solutions. The probable mechanism of reaction between Eu³⁺-doped CdS composite nanoparticles and Hg²⁺ was also discussed.     

Effect of the Spherical Silica Surface on the Photoluminescence of the Loaded CdS Nanoparticles

CdS nanoparticles were formed on the surface of silica microspheres by the improved layer‐by‐layer self‐assembled technique. High‐resolution electron microscope (HRTEM) image and energy dispersive x‐ray analysis (EDX) confirmed formation of a quasi‐continuous CdS nanoparticles film on the silica microspheres. The results of UV‐vis and fluorescence spectra display that the spherical silica surface has a great effect on the photoluminescence of the loaded CdS nanoparticles. In contrast to the CdS nanoparticles powder, the composite can exhibit the emission ascribed to the band gap transition when the CdS nanoparticles film is relatively thick. This phenomenon is probably due to an enhancement of the crystallinity of CdS nanoparticles induced by the silica spheres.     

Synthesis of a hybrid material from CdS nanoparticles and carbon nanotubes

A method for synthesis of a hybrid material from CdS nanoparticles and carbon nanotubes (CNT) by the precipitation of CdS nanoparticles on the CNT surface from an aqueous solution containing the Cd^II salt, thiourea, and ammonia was developed. The dependences of the size of particles formed on the CNT on the temperature of the solution and the duration of precipitation were observed. The degree of imperfection of the CNT surface exerts a substantial effect on the density of the precipitated CdS particles.     

CdS Reinforced with CoSX/NiCo-LDH Core-shell Co-catalyst Demonstrate High Photocatalytic Hydrogen Evolution and Durability in Anhydrous Ethanol

At present, inefficient charge separation of single photocatalyst impedes the development of photocatalytic hydrogen evolution. In this work, the CoS_X/NiCo-LDH core-shell co-catalyst was cleverly designed, which exhibit high activity and high stability of hydrogen evolution in anhydrous ethanol system when coupled with CdS. Under visible light (λ≥420 nm) irradiation, the 3 %Co/NiCo/CdS composite photocatalyst exhibits a surprisingly high photocatalytic hydrogen evolution rate of 20.67 mmol g⁻¹ h⁻¹, which is 59 times than that of the original CdS. Continuous light for 20 h still showed good cycle stability. In addition, the 3 %Co/NiCo/CdS composite catalyst also shows good hydrogen evolution performance under the Na₂S/Na₂SO₃ and lactic acid system. The fluorescence (PL), ultraviolet-visible diffuse reflectance (UV-vis) and photoelectrochemical tests show that the coupling of CdS and CoS_X/NiCo-LDH not only accelerates the effective transfer of charges, but also greatly increases the absorption range of CdS to visible light. Therefore, the hydrogen evolution activity of the composite photocatalyst has been significantly improved. This work will provide new insights for the construction of new co-catalysts and the development of composite catalysts for hydrogen evolution in multiple systems.     

Study of poly(N,N-dimethylacrylamide)/CdS nanocomposite organic/inorganic gels

CdS nanoparticles have been synthesized and stabilized in poly(N,N-dimethylacrylamide) hydrogels. The properties of the composite material have been characterized by UV-vis spectroscopy, scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, and steady-state and time-resolved luminescence spectroscopy. This material can be obtained in three different states: swollen, shrunk, and freeze-dried. The swollen and the freeze-dried states correspond to a nanocomposite organic/inorganic (wet or dry) gel containing CdS nanoparticles of approximately 50 nm diameter while the shrunk state is a two-phase system containing CdS crystals, which precipitate forming interesting geometrical shapes.     

Photocontrolled magnetization of CdS-modified Prussian blue nanoparticles

The first photocontrollable magnetic nanoparticles containing CdS and Prussian blue (PB) have been created using reverse micelles as nanoreactors. Photoinduced electron transfer from CdS to PB in the reverse micelle changed the magnetic properties of the composite nanoparticles from ferromagnetic to paramagnetic. The magnetization in the ferromagnetic region below 4 K was substantially decreased after UV light illumination and could be restored almost to its original level by thermal treatment at room temperature. This novel strategy of designing composite nanoparticles containing photoconductive semiconductors and magnetic materials to create photoswitchable magnetic materials may open many possibilities in the development of magneto-optical devices.     

硫化镉纳米粒子的合成及发光性能

采用多元醇方法制备了硫化镉纳米粒子, 利用X射线衍射仪、透射电子显微镜和扫描电子显微镜等技术对样品的微观结构、粒径大小和形貌进行了分析. 结果表明, 所得硫化镉纳米粒子粒径均一, 形貌均为球形. 光致发光性质研究结果表明, 所得纳米粒子具有较好的蓝光发射性能.     

CdS/TiO2 composite films for methylene blue photodecomposition under visible light irradiation and non-photocorrosion of cadmium sulfide

Cadmium sulfide/titanium dioxide (CdS/TiO₂) composite films were grown on glass by the chemical bath deposition (DBQ) and sol-gel/dip coating methods, respectively, in order to increase the photocatalytic activity of TiO₂ in photodegradation processes. The influence of the CdS deposition time on the morphology, optical absorption, and phononic modes of the composites were examined. Scanning electron microscopy (SEM) images showed clearly the CdS deposit on the TiO₂ surface. The absorbance spectra indicated that the absorption of composites depends on the CdS deposition time and the absorption edges are shifted to the visible range. Micro Raman spectra exhibited the phonons associated with the TiO₂ anatase and the longitudinal optic (LO) phonon of CdS whose intensity increases with the CdS deposition time. Photodegradation of methylene blue (MB) under visible light irradiation was observed in all films and the results were compared with those obtained with TiO₂ films. The decomposition is higher for the composite with the CdS deposition time of 15 min. This optimal deposition time allows maximal enhancement of the charge carriers transfer to TiO₂ involved in the photocatalysis. No signal associated with cadmium was detected by the atomic absorption spectroscopy (AAS), which means that the CdS photocorrosion does not occur since trap centers such as OH-Cd-S and Cl^?, which trap holes and inhibit the photocorrosion, are produced during the growth process.     

Solid state morphology and band gap studies of ETS-10 supported CdS nanoparticles

Engelhard titanosilicate (ETS-10) supported cadmium sulphide (CdS) nanoparticles were synthesized and characterized by various solid state techniques including: XRD, DR UV-Vis, TEM and FESEM. The effect of different synthesis routes of CdS nanoparticles on its physicochemical character was studied. It was observed that CdS nanoparticles prepared by both in situ sulphur reduction (CdS-IS) and reverse micelle (CdS-RM) methods showed similar roperties. However, CdS-IS nanoparticles are more feasible and economically practical. The reflectance measurements of the as-synthesized CdS nanoparticles are apparently blue-shifted compared to bulk CdS. This phenomenon of blue-shifted absorption edge has been ascribed to an increase in bandgap energy with a decrease in particle sizes. The bandgap of the as-synthesized CdS samples was calculated from the linear correlation of [F(R) hν]² and hν. The bandgap of CdS in ETS-10 was noticeably slightly reduced when compared with the as-synthesized CdS (8 nm) due to the formation of cluster arrays on the pores of ETS-10.     

A new technique for preparing macroporous inorganic composite material

Macroporous CdS/SiO₂ was prepared with a new approach in which at first CdS nanoparticles were deposited on polymer microbeads without surfactant, then core-shell composite was self-assembled with sedimentation-aggregation, and at last macroporous material was obtained by the removal of the template. The results show that the morphology of core-shell composite could be tailored by the polymer template and the concentration of the reactant, and the shell thickness could be altered by the temperature and the aging time. This new idea was an effective method to prepare other macroporous composite with large-scale.     

TiO_2/CdS/Ru(bpy)_2(NCS)_2作为太阳电池光阳极的探讨

将 Cd S纳米粒子复合在 Ti O2 纳米多孔膜上 ,用染料 Ru( bpy) 2 ( NCS) 2 对此复合半导体纳米膜电极进行敏化 ,测量了不同 Cd S复合量的 ITO/Ti O2 /Cd S/Ru( bpy) 2 ( NCS) 2 光阳极组成光电池的能量转换效率 .实验证明 ,ITO/Ti O2 /Cd S/Ru( bpy) 2 ( NCS) 2 作为太阳电池光阳极的能量转换效率与 Ti O2 /Cd S复合半导体中 Cd S的含量有关 .当 Cd S复合时间为 5 min的电池的短路电流为 5 .2 3A/m2 ,开路电压为 0 .71 6 V,能量转换效率为 0 .77% .     

CdS-containing nano-assemblies of double hydrophilic block copolymers in water

Two samples of poly(sodium(sulfamate-carboxylate)isoprene)-block-poly(ethylene oxide) copolymer (SCIEO-1 and SCIEO-2) differing in molecular weight and relative length of polyelectrolyte blocks have been used as templates for the synthesis of cadmium sulfide (CdS) nanoparticles in aqueous media. The double-hydrophilic copolymer SCIEO has very high 1D charge density, and its polymer chain structure mimics that of polysaccharide heparin. It is soluble in aqueous media, but the addition of cadmium acetate (Cd(Ac)₂) to its aqueous solution causes the formation of micellar aggregates with Cd²⁺containing insoluble cores above the threshold Cd²⁺ concentration. The trapped Cd²⁺ ions can be chemically transformed to CdS nanoparticles. The stability of hybrid SCIEO/CdS micelles depends on the ratio of PEO-to-SCI lengths: it was found that the SCIEO-2 copolymer with sufficiently long PEO block behaves as an effective stabilizer for the synthesis of CdS nanoparticles embedded in micelles, while SCIEO-1 does not. The morphology of aggregates varies with the Cd-to-SCI ratios and ranges from spherical to mixture of spherical and necklace-like micellar aggregates. A number of experimental techniques including static and dynamic light scattering, fluorescence correlation spectroscopy, atomic force and transmission electron microscopy, UV-vis, and fluorescence spectroscopy were employed for the characterization of both CdS containing hybrid micelles and embedded CdS nanoparticles.     

An improved pyrolysis route to synthesize carbon-coated CdS quantum dots with fluorescence enhancement effect

Well-dispersed carbon-coated CdS (CdS@C) quantum dots were successfully prepared via the improved pyrolysis of bis(1-dodecanethiol)-cadmium(II) under nitrogen atmosphere. This simple method effectively solved the sintered problem resulted from conventional pyrolysis process. The experimental results indicated that most of the as-prepared nanoparticles displayed well-defined core-shell structures. The CdS cores with diameter of ∼5 nm exhibited hexagonal crystal phase, the carbon shells with thickness of ∼2 nm acted as a good dispersion medium to prevent CdS particles from aggregation, and together with CdS effectively formed a monodisperse CdS@Carbon nanocomposite. This composite presented a remarkable fluorescence enhancement effect, which indicated that the prepared nanoparticles might be a promising photoresponsive material or biosensor. This improved pyrolysis method might also offer a facile way to prepare other carbon-coated semiconductor nanostructures.