Direct electrochemistry of hemoglobin and its biosensing for hydrogen peroxide on TiO2–polystyrene nanofilms

Nanofilms of titanium dioxide (TiO₂) nanoparticles that mediate the assembly of polystyrene (PS) nanoparticles for immobilizing hemoglobin (Hb) on carbon ionic liquid electrode have been developed. Fourier transform infrared spectroscopy shows that Hb retains its native structure in TiO₂–PS nanofilms. Scanning electron microscopy reveals that the nanofilms possess uniform morphology and Hb is immobilized on the surface of the nanofilms. Electrochemical investigation of the biosensor indicates that the direct electrochemistry of hemoglobin is realized on the nanofilms, and there is a formal potential of ?0.320 V in deaerated buffer solutions; the biosensor shows good electrocatalytic activity toward the reduction of hydrogen peroxide with a linear range from 0.5 to 640 μM, a detection limit of 0.2 μM (S/N = 3) and a sensitivity of 103 μA mM^?1. Thus, the nanofilms will have potential application in the design of novel electrochemical biosensors.     

P3HT修饰一维有序壳核式CdS/ZnO纳米棒阵列复合膜的光电化学性能

采用电化学方法在铟锡氧化物(ITO)导电玻璃上制备了高度有序的ZnO纳米棒阵列, 在ZnO纳米棒阵列上先后电化学沉积CdS纳米晶膜及聚3-己基噻吩(P3HT)薄膜得到P3HT修饰的一维有序壳核式CdS/ZnO纳米阵列结构, 并通过扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)、能量散射X射线(EDX)等表征手段证实了该结构的形成. 以此纳米结构薄膜为光阳极组装新型半导体敏化太阳电池, 研究了CdS纳米晶膜的厚度和P3HT薄膜的沉积对电池光伏性能的影响, 初步探讨了电荷在电池结构中的传输机理, 结果表明, CdS纳米晶膜和P3HT薄膜的沉积有效地拓宽了光阳极的光吸收范围, 实验中电池的光电转换效率最高达到1.08%.     

ITO/TiO2表面电沉积CdS纳米粒子及其薄膜的光电性能

采用阴极恒电位沉积方法, 在TiO2表面沉积制备出CdS纳米粒子. XRD和SEM测试结果表明, CdS粒子的结构以六方晶相为主, 粒径分布均匀, 表面形貌呈菜花状. 通过调节沉积电位和沉积时间等因素在一定程度上可以控制CdS纳米粒子的生长. 随着沉积电位变负, CdS粒子的粒径逐渐减小. 沉积时间越短, 粒子粒径越小. 紫外-可见吸收光谱测试结果表明, 不同条件下制备出来的CdS粒子表现出一定的量子尺寸效应. 此外, 沉积条件也会影响ITO/TiO2/CdS复合半导体薄膜的光电性能.     

Synthesis and Characterization of CdS Nanoparticles via Cyclic Microwave from Cadmium Oxalate

The present study reports synthesis and characterization of CdS nanoparticles prepared by cyclic microwave route with the use of [Cd(C₂O₄)·3H₂O] powder as a precursor. The products, with an average size ~15 nm, were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray microanalysis, thermogravimetric analysis, transmission electron microscopy and Fourier transform infrared spectroscopy. Optical property of obtained product was investigated by photoluminescence spectroscopy. The prepared nanostructures displayed a very strong luminescence at 528 nm (2.34 eV) at room temperature.     

The influence of water–organic solvent composition on the morphology and luminescent properties of CdS nanoparticles obtained by chemical precipitation

Cadmium sulfide (CdS) nanoparticles have been obtained by chemical precipitation onto the surface of single-crystalline silicon from an aqueous solution of ammonia, cadmium chloride (CdCl₂), and thiourea, as well as from water–DMSO and water–DMF mixtures with the same concentrations of the reagents. According to data of atomic force microscopy, the samples obtained from the aqueous solution consist of individual nanoparticles and agglomerates thereof with sizes of no larger than 1 µm. Materials obtained from the water–organic mixtures are distinguished by the aggregation of CdS nanoparticles into threadlike chains. The length of the formed curved chains and the size of CdS nanoparticles composing them depend on the nature and amount of an organic component of a mixture. Atomic force microscopy, transmission electron microscopy, and photoluminescence spectroscopy data have shown that the average size of CdS nanoparticles is 2–2.5 nm depending on solvent composition.     

In‐Situ Growth and Immobilization of CdS Nanoparticles onto Functionalized MoS2: Preparation,Characterization and Fabrication of Photoelectrochemical Cells

A facile strategy for the controllable growth of CdS nanoparticles at the periphery of MoS₂ en route the preparation of electron donor‐acceptor nanoensembles is developed. Precisely, the carboxylic group of α‐lipoic acid, as addend of the modified MoS₂ obtained upon 1,2‐dithiolane functionalization, was employed as anchor site for the in situ preparation and immobilization of the CdS nanoparticles in an one‐pot two‐step process. The newly prepared MoS₂/CdS hybrid material was characterized by complementary spectroscopic, thermal and microscopy imaging means. Absorption spectroscopy was employed to register the formation of MoS₂/CdS, by observing a broad shoulder centered at 420 nm due to CdS nanoparticles, while the excitonic bands of MoS₂ were also evident. Moreover, based on the efficient quenching of the characteristic fluorescence emission of CdS at 725 nm by the presence of MoS₂, strong electronic interactions at the excited state between the two species within the ensemble were identified. Photoelectrochemical assays of MoS₂/CdS thin‐film electrodes revealed a prompt, steady and reproducible anodic photoresponse during repeated on‐off cycles of illumination. A significant zero‐current photopotential of ?540 mV and an anodic photocurrent of 1 μA were observed, underlining improved charge‐separation and electron transport from CdS to MoS₂. The superior performance of the charge‐transfer processes in MoS₂/CdS is of direct interest for the fabrication of photoelectrochemical and optoelectronic devices.     

Preparation and characterization of crack-free sol–gel based SiO2–TiO2 hybrid nanoparticle film

Owing to the diverse potential applications of hybrid silica–titania thin films, the synthesis and characterization of these films have been carried out with a special focus on application as a medium index layer for multilayered functional coatings. For synthesis, tetraethylorthosilicate and titanium tetraisopropoxide were chosen as precursors for the formation of silica-titania hybrid thin films/nano-composites through an in situ sol–gel process. These films were sequentially obtained on Cu substrate utilizing spin coating. The hybrids were characterized by field emission scanning electron microscope, energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction, atomic force microscopy and Fourier transform infrared spectroscopy (FTIR). Field emission scanning electron microscope morphology displayed a smooth, densified and crack- free layer of silica-titania hybrid nanoparticles in the range of 20–71 nm after calcinations at low temperature of 300ºC for 1 h. X-ray diffraction pattern confirms the phases of titania with higher crystallinity and phase transformation at low temperature. The prepared films were uniform with low 8.852 nm RMS value. The stoichiometry of films was confirmed by EDX results. The FTIR spectroscopy indicated the establishment of heterogeneous chemical bonding between the Ti and Si surfaces through oxygen.     

Fabrication of PES-based nanofiltration membrane modified by composite PAA-co-PMMA-g-ZnA nanoparticles

In the current research, nanocomposite polyethersulfone-based nanofiltration membranes were prepared by composite PAA-co-PMMA-g-ZnA nanoparticles. NF membranes were fabricated by phase inversion through casting solution technique. The effect of composite PAA-co-PMMA-g-ZnA nanoparticles concentration into the casting solution on physicochemical characteristics of membrane was studied. Scanning optical microscopy images showed uniform particle distribution for the membranes. Scanning electron microscopy images also demonstrated that membrane porosity was enhanced by increase in nanoparticles content ratio. The membrane surface 3D images showed smooth surface for the membranes filled with 0.05, 0.1 and 0.5 wt% nanoparticles. The contact angle results exhibited that membrane hydrophilicity was improved significantly by using of NPs in membrane matrix. The contact angle was decreased from 65.38° for PES membrane to 48.33° for membrane filled with 0.5 wt% nanoparticles. The water permeability was reduced initially by addition of 0.05 wt% nanoparticles into the casting solution and then increased by more nanoparticles loading rate (0.1 wt%). The water permeability was decreased again by more increase in nanoparticles loading range from 0.5 to 1 wt%. The salt rejection was improved strongly from 68.4 % for PES to 88.58 % for membrane filled with 0.5 wt% nanoparticles. The membranes mechanical strength was increased sharply from 2835.5 to 3337.3 kPa with addition of nanoparticles into the casting solution.     

Sensitization of Mn with CdS nanoparticles via electrochemical deposition technique for photocurrent enhancement of nanomaterial’s-sensitized photoelectrochemical cells

A photoconversion efficiency of 2.12% was obtained under visible light illumination by nanostructure-sensitized photoelectrochemical cells using Mn/CdS as sensitizer loaded on TiO₂ nanotube arrays (NTAs) (Mn/CdS/TiO₂). Sensitization of Mn on CdS nanoparticles pre-loaded on TiO₂ NTAs was carried out by a two-step electrodeposition method. Compared with unsensitized TiO₂ NTAs, the photocurrent had increased from 0.03 to 4.12 for Mn/CdS/TiO₂ prepared at 1 min. The effects of deposited Mn on the physical, chemical, and photoelectrochemical properties of the CdS/TiO₂ NTAs nanostructure were investigated by using UV–visible diffuse reflectance spectroscopy, X-ray diffractometry, and field-emission scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. The photoelectrochemical analysis was examined in a three-electrode system under a halogen illumination by using the prepared film as the photo-anode.     

Preparation and Optoelectronic Property of a SnO2/CdS Nanocomposite Based on the Flowerlike Clusters of SnO2 Nanorods

A SnO₂/CdS nanocomposite based on the flowerlike clusters of SnO₂ nanorods was prepared and characterized with x-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM) and EDX analysis. The SEM and TEM images show the nanocomposite is composed of CdS nanoparticles and flowerlike clusters of SnO₂ nanorods. The UV–vis spectrum of the nanocomposite displays a new absorption band in the region of 350 to 530 nm, compared with that of the flowerlike clusters of SnO₂ nanorods. The measurement of optoelectronic property indicates that the photoresponse of the composite is extended into the visible region and the incident photon-to-current conversion efficiency (IPCE) of the composite is up to 6.5 in the range of 400 to 440 nm. These phenomena ought to be ascribed to the special nanostructure of the SnO₂/CdS composite obtained.     

Silver Metallic Nanoparticles with Surface Plasmon Resonance: Synthesis and Characterizations

Silver nanoparticles were synthesized by the reduction of the silver nitrate (AgNO₃) using the latex copolymer in ethanol solution under microwave (MW) heating. The reaction parameters such as silver precursor concentration (from 0.005 to 0.1 g/l) and MW power (200–800 W) significantly affect the formation rate, shape, size and distribution of the silver nanoparticles. A significant reduction of irradiation time was observed when the MW energy is compared to conventional thermal reduction processes. The prepared silver nanoparticles show uniform and stable sizes from 5 to 11 nm, which can be stored at room temperature for approximately 12 months without any visible change. These peculiarities indicate that the latex copolymer is a good stabilizer for the silver nanoparticles. The optical properties, morphology, and crystalline structure of the silver-latex copolymer nanocomposites were characterized by the Ultraviolet–Visible spectroscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The study of the TEM images at high magnifications identified the silver nanoparticles as face-centered cubic (fcc) structure with spherical and hexagonal shapes.     

Synthesis, structural and photocatalytic studies of Mn-doped CdS nanoparticles

Mn-doped CdS nanoparticles (Cd_1?x Mn _x S; where x = 0.00–0.10) were synthesized by a chemical precipitation method. The synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscope, transmission electron microscope (TEM), and UV–Vis spectrometer. The XRD and TEM measurements show that the size of crystallites is in the range of 10–40 nm. Optical measurements indicated a red shift in the absorption band edge upon Mn doping. The direct allowed band gaps of undoped and Mn-doped CdS nanoparticles measured by UV–Vis spectrometer were 2.3 and 2.4 eV at 400 °C, respectively. Photocatalytic activities of CdS and Mn-doped CdS were evaluated by irradiating the solution to ultraviolet light and taking methyl orange (MO) as organic dye. It was found that 5 mol% Mn-doped CdS bleaches MO much faster than undoped CdS upon its exposure to the ultraviolet light. The experiment demonstrated that the photo-degradation efficiency of 5 mol% Mn-doped CdS was significantly higher than that of undoped CdS.     

Photoelectrochemical performance of dye and semiconductor sensitization on 1-D hollow hexagonal ZnO rods: A comparative study

One-dimensional hollow hexagonal ZnO rods (1-D HHZRs) were grown onto the SnO₂: F (FTO) coated glass substrates by using two-step deposition techniques. Initially, the ZnO seed layer was coated onto the FTO which was followed by hydrothermal route in order to grow 1-D HHZRs. These 1-D HHZRs were decorated with Eosin-Y dye and CdS semiconductor nanoparticles (NPs) by using a chemical routes like dip coating and successive ionic layer absorption reaction (SILAR) technique, respectively to improve its photoelectrochemical (PEC) performance. The structural, morphological, optical and electrochemical characterizations of the thin films were analyzed by various sophisticated instruments. X-ray diffraction (XRD) pattern corroborated the phase formation of ZnO and CdS with the hexagonal and cubic crystal structure, respectively. 1-D HHZRs films were obtained by scanning electron microscopy (SEM) with rod diameter of about 1.47 μm. Furthermore, SEM image clearly showed the CdS NPs covered 1-D HHZRs. The direct optical bandgap energy of the samples were estimated to be 3.28, 3.24 and 3.03 eV. CdS NPs-sensitized 1-D HHZRs samples showed hydrophilic nature for water contact angle, which is advantageous for the better improvement in the PEC performance as compared with pristine and dye-sensitized 1-D HHZRs.     

Preparation of gold nanoislands on various functionalized polymer-modified glass and ITO for electrochemical characterization of monolayer assembly of alkanethiols

Nanometer dimension of citrate-capped gold nanoparticles can be firmly bound with various functionalized polymer-modified glass plate and indium tin oxide (ITO) substrates. Herein we report 3-aminopropyltriethoxysilane, polyvinyl pyridine, polyethylene imines, etc. as binding agents to modify these substrates to stabilize the charged colloidal gold nanoparticles through electrostatic stabilization of gold nanoparticles. When gold nanoparticles pretreated substrate are exposed into the seeding growth solution, the preadsorbed gold nanoparticles grow further and then form nanoislands of gold on glass and ITO substrates. The formation of nanoislands on microscope glass slide and ITO was monitored with UV-visible spectroscopy, cyclic voltammetry, and atomic force microscopy methods. The gold nanoislands and gold nanoparticles pretreated substrates can be used as platform to study the self-assembling behavior of long chain alkanethiols such as C₁₂SH, C₁₆SH, and C₁₈SH. The binding, coverage, and electron transfer characteristics of monolayer assembly on modified gold nanoisland and nanoparticles modified substrates are studied using electrochemical studies. The gold substrates can be prepared by this method, which is simple and reproducible and can be applied to various sensor and electrocatalytic applications.     

Simple and low temperature preparation and characterization of CdS nanoparticles as a highly efficient photocatalyst in presence of a low-cost ionic liquid

A simple and low temperature method is proposed for preparation of CdS nanoparticles in presence of 1-ethyl-3-methylimidazolium ethyl sulfate, [EMIM] [EtSO₄], a room-temperature ionic liquid (RTIL). The powder X-ray diffraction (XRD) studies display that the products are excellently crystallized in the form of cubic structure and size of the nanparticles prepared in presence of the RTIL is smaller than that prepared in water. Energy dispersive X-ray spectroscopy (EDX) investigations reveal that the products are very pure and nearly stoichiometric. The results obtained by scanning electron microscopy (SEM) demonstrate that the CdS nanoparticles prepared in presence of the RTIL have lower tendency for aggregation relative to the prepared sample in water. Diffuse reflectance spectra (DRS) of the product prepared in the neat RTIL, shows 1.52 eV blue shift relative to bulk CdS, which can be attributed to quantum confinement effect of the CdS nanoparticles. A possible formation mechanism for CdS nanoparticles in presence of the RTIL is presented. Photocatalytic activity of the CdS nanoparticles towards photodegradation of methylene blue (MB) using UV and visible lights was performed. The results demonstrate that observed firstorder rate constant for photodegradation of MB on CdS nanoparticles prepared in the neat RTIL are about 20 and 6 times greater than the prepared sample in water using visible and UV lights, respectively.     

Preparation and nonlinear optical properties of Au nanoparticles doped TiO2 thin films

Nano-sized noble metal nanoparticles doped dielectric composite films with large third-order nonlinear susceptibility due to the confinement and the enhancement of local field were considered to be applied for optical information processing devices, such as optical switch or all optical logical gates. In this paper, sol–gel titania thin films doped with gold nanoparticles (AuNPs, ~10 nm in average size) were prepared. AuNPs were firstly synthesized from HAuCl₄ in aqueous solution at ~60 °C, using trisodium citrate as the reducing agent, polyvinylpyrrolidone as the stable agent; then the particle size and optical absorption spectra of the AuNPs in aqueous solutions were characterized by transmitting electron microscopy and UV–Vis–NIR spectrometry. Sol–gel 2AuNPs–100TiO₂ (in %mol) thin films (5 layers, ~1 μm in thickness) were deposited on silica glass slides by multilayer dip-coating. After heat-treated at 300–1,000 °C in air, the AuNPs–TiO₂ thin films were investigated by X-ray diffraction, scanning electron microscopy and atomic force microscopy. The nonlinear optical properties of the AuNPs–TiO₂ thin films were measured with the Z-scan technique, using a femtosecond laser (200 fs) at the wavelength of 800 nm. The third-order nonlinear refractive index and nonlinear absorption coefficient of 2AuNPs–100TiO₂ films were at the order of 10^?12 cm²/W, and the order of 10^?6 cm/W, respectively, and the third-order optical nonlinear susceptibility χ⁽³⁾ was ~6.88 × 10^?10 esu.     

Light conversion efficiency of flower like structure TiO<Subscript>2</Subscript> thin film solar cells

Flower like structure TiO₂ thin films have been grown onto ITO coated glass substrates by sol–gel method. TiO₂ nano flowers have been sensitized using CdS quantum dots prepared using simple precursors by chemical method. The assembly of CdS quantum dots with TiO₂ nano flower has been used as photo-electrode in quantum dot sensitized solar cells. The surface morphology has been studied using scanning electron microscope; it shows that the film exhibits flower like structure. The absorption spectra reveals that the absorption edge of CdS quantum dot sensitized TiO₂ nano flower shifts towards longer wavelength side when compared to the absorption edge of TiO₂ nano flower. The efficiency of the fabricated CdS quantum dot sensitized TiO₂ nano flower based solar cell is 0.66%.     

Optical and kinetic studies of CdS:Cu nanoparticles

CdS:Cu nanoparticles were successfully synthesized by a coprecipitation method using mercaptoethanol as a capping agent. Thermoluminescence (TL) spectra of CdS:Cu nanoparticles were studied for different exposure time. The synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV–Vis spectrometry. XRD and SEM measurements showed that the size of the crystallites was in the range 8–17 nm. Optical measurements indicated a blue-shift in the absorption band edge upon Cu doping. The direct allowed bandgap of undoped and Cu-doped CdS nanoparticles was 2.53 and 2.64 eV, respectively. We also calculated the kinetic parameters for Cu-doped CdS nanoparticles from the TL glow curves measured at 254, 249, and 244 °C with variation of the ultra-violet (UV) exposure time. The glow curve shows general order kinetics, and its kinetic parameters are calculated.     

Facile Microwave Approach for Synthesis of Copper–Indium Sulfide Nanoparticles and Study of Their Behavior in Solar Cell

CuInS₂ (CIS) nanoparticles (nps) were synthesized via a microwave approach by adding eight sulfur sources with a new copper precursor, [bis(acetylacetonato)copper(II)]; [Cu(acac)₂]. The products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, ultraviolet–visible and photoluminescence spectroscopy. Band gap of as-synthesized nps was 2.1 eV that showed about 0.55 eV blue shift in comparison to its bulk type. As observed in other semiconductor systems, the optical absorption blue shift is associated with quantum confinement effects. Thin film of CIS was prepared by doctor’s blade technique and solar cell made from indium transparent oxide/CIS/CdS/Pt layers. I–V characterization was investigated for this cell and fill factor, open-circuit voltage (V _oc) and short-circuit current (I _sc) were achieved.     

S/Cd物质的量比对微波水热制备CdS微晶的形貌影响及光学性能研究

采用微波水热法,以CdCl2·H2O和Na2S2O3·5H2O为镉源和硫源,在不同的S/Cd物质的量比条件下合成了CdS微晶。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、场发射扫描电子显微镜(FE-SEM)、EDS、透射电子显微镜(TEM)等对样品的物相、形貌和元素组分进行了分析。结果表明:随着S/Cd物质的量比的增大,产物CdS的形貌发生规律性变化,由四面体结构逐渐转变为准球形结构;准球形结构具有分级结构,是由更小的纳米晶组装而成;光致发光性质研究结果表明,所得的CdS微晶具有较好的蓝光发射性能。