Characteristics of electrodeposited bismuth telluride thin films with different crystal growth by adjusting electrolyte temperature and concentration

Bismuth telluride (Bi₂Te₃) thin films were prepared with various electrolyte temperatures (10°C–70 °C) and concentrations [Bi(NO₃)₃ and TeO₂: 1.25–5.0 mM] in this study. The surface morphologies differed significantly between the experiments in which these two electrodeposition conditions were separately adjusted even though the applied current density was in the same range in both cases. At higher electrolyte temperatures, a dendrite crystal structure appeared on the film surface. However, the surface morphology did not change significantly as the electrolyte concentration increased. The dendrite crystal structure formation in the former case may have been caused by the diffusion lengths of the ions increasing with increasing electrolyte temperature. In such a state, the reactive points primarily occur at the tops of spiked areas, leading to dendrite crystal structure formation. In addition, the in-plane thermoelectric properties of Bi₂Te₃ thin films were measured at approximately 300 K. The power factor decreased drastically as the electrolyte temperature increased because of the decrease in electrical conductivity due to the dendrite crystal structure. However, the power factor did not strongly depend on the electrolyte concentration. The highest power factor [1.08 μW/(cm·K²)] was obtained at 3.75 mM. Therefore, to produce electrodeposited Bi₂Te₃ films with improved thermoelectric performances and relatively high deposition rates, the electrolyte temperature should be relatively low (30 °C) and the electrolyte concentration should be set at 3.75 mM.     

Influence of deposition conditions on nanostructured InSe thin films

In this study, nanostructured indium selenide (InSe) thin films were deposited on Indium tin oxide (ITO)-coated glass substrate using electrochemical deposition (ECD) from aqueous solution containing In(SO₄)₃.H₂O and SeO₂. The effects of deposition potential (−0.70 to −1.35 V), time (30-3600 s), temperature (25-80 °C) and pH (2.58 for A samples; 2 for B samples and 1.45 for C samples) on growth of the InSe thin films were examined in terms of their structural, morphological and optical properties. X-ray diffraction (XRD) analysis confirmed that the InSe thin films are in polycrystalline structure. It was found that the values of grain size decreased and the full width half maximum (FWHM) values increased with the increasing deposition potential. According to the absorption measurements, optical properties of the thin films varied with changes in deposition conditions. Based on the atomic force microscopy (AFM) and the scanning electron microscopy (SEM) images, surface morphology of the thin films was influenced by deposition potential and pH of the electrolyte, and non-homogeneous depositions distributed across the entire surface were observed. In addition, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and fourier transform infrared spectroscopy (FT-IR) analyses were used to further examine crystal quality, vibration, chemical binding conditions, In/Se orientation and structure of the prepared InSe thin films. When Raman results are examined, the B12 sample shows a more intensity and narrow peak at 248 cm⁻¹. XPS measurements sowed that A6 sample exhibited more growth in low potential for a long time and better film stoichiometry compared to the other three samples. Also, FT-IR studies prove the presence of InSe. According to the results, the film did not form at low temperatures and short times. However, the film formation began with the increasing deposition temperature and time at the low potential value of −0.730 V. But, it is clear that a high quality film can be obtained in cathodic potential with −1.3 V and shorter deposition time with 300 s at room temperature respectively. Overall results showed that the high quality thin films can be obtained by the ECD technique. However, deposition conditions must be sensitively adjusted to control morphology of the electrodeposited nanoparticles.     

Electrochemical Investigation of Glucose on a Highly Sensitive Nickel‐Copper Modified Pencil Graphite Electrode

Novel nickel‐copper modified pencil graphite electrode (Ni?Cu/PGE) was fabricated and used as non‐enzymatic sensor for glucose determination. Ni and copper were electrodeposited on PGE using cyclic voltammetry. Morphology and composition of the modified PGE electrode were characterized by field‐emission gun scanning electron microscopy (FEG‐SEM), energy‐dispersive X‐ray spectroscopy (EDX) and Fourier transform infrared spectroscopy (FT‐IR). Electrochemical oxidation of glucose was evaluated by cyclic voltammetry as well as by amperometry. Electrochemical measurements indicate that the Ni?Cu/PGE exhibits a high sensitivity of 2951 μA mM^?1 cm^?2, and a low detection limit of 0.99 μM which are, respectively, three times higher and twice lower than that on Ni/PGE prepared in the same conditions. Moreover, Ni?Cu/PGE exhibits a wider linear range from 1 to 10000 μM with a rapid response time within 2 s. Moreover, Ni?Cu/PGE showed a remarkable stability. The electrode was successfully applied for determination of glucose concentration in human blood without significant interference from potential endogenic interferents. The good applicability of the elaborated sensor made Ni?Cu/PGE promising for the development of effective and inexpensive non‐enzymatic glucose sensor.     

Lightweight ITO Electrodes Decorated with Gold Nanostructures for Electrochemical Applications

Gold nanostructures were fabricated on a transparent indium tin oxide (ITO) coated PET substrate by an electrodeposition technique from a potassium gold (III) chloride solution for two different types of applications. It was found that the optical transparency of lightweight ITO electrodes could be maintained by depositing isolated gold nanostructures while opening up the use of these electrodes for inner sphere electron reactions, such as hydroquinone oxidation, which are not possible at ITO electrodes. For practical applications the adhesion of gold to the ITO electrode was improved by modifying the ITO surface with 3‐mercaptopropyl‐trimethoxysilane (MPS). Compared to Au/ITO, the Au/MPS/ITO electrode showed vastly improved electrochemical activity toward various electron transfer reactions when subjected to mechanical stress. The biosensing properties of the Au/MPS/ITO electrode was also investigated by studying the detection of immobilized DNA on the Au/MPS/ITO electrode via electrochemical impedance spectroscopy (EIS).     

Template‐Synthesized Vertical Needle Array as Injection Platform for Microalgae

Increasing numbers of studies in the past few decades have demonstrated vertically‐oriented nanoneedles arrays (NNAs) as innovative tools to interrogate and manipulate biological cells, where the needles are inserted into the cells as functional probes for high‐throughput detection and biomolecule delivery. However, majority of these studies use mammalian cells: leaving NNA application to plant cells still in its infancy and largely unexplored. This paper highlights our contributions in exploring the utility of NNAs to microalgae – a diverse group of aquatic, photosynthetic organisms studied intensively as bio‐factories for producing high‐value‐added products such as fuels and pharmaceuticals. Microalgal strain development processes have long suffered from the hard cell wall that surrounds the cell and inhibits delivery of foreign materials into the cell. Conically‐shaped, metallic NNAs were developed with template synthesis that successfully penetrate through the cell wall barrier and achieve material injection – using the widely studied model microalga, Chlamydomonas reinhardtii. Earlier works from mammalian cells are introduced and discussed to clarify the framework established in this field, while recent studies of both mammalian and microalgal cells are also referenced to examine the trends, challenges, and future perspectives of NNA application to microalgae.     

电化学沉积制备纳米结构铜电极及其葡萄糖检测性能

利用电化学沉积法制备了高电活性的纳米结构铜电极材料, 采用扫描电子显微镜和电化学方法分别对电极表面形貌和电化学性能进行了表征, 研究了实验参数对葡萄糖电氧化活性的影响. 结果表明, 改变沉积条件可以调控沉积铜的形貌及电催化活性. 在最佳条件下制备的铜纳米结构电极对葡萄糖检测的灵敏度为1310 μA·L/mmol, 检出限为5.0×10^-7 mol/L(S/N=3).     

Direct analysis of reference biofluids by coupled in situ electrodeposition-electrothermal atomic absorption spectrometry

The application of coupled in situ electrodeposition-electrothermal atomic absorption spectrometry (ED-ETAAS) to the determination of Pb in biological standard reference materials is described. In situ electrodeposition at a cell voltage of 3.0 V from 25-μl samples onto electrodeposited Pd is used to quantitatively separate the analyte from blood and urine matrices. With subsequent withdrawal of spent electrolyte, this overcomes the atomisation problems inherent with high salt and organic contents. ED-ETAAS is applied with minimal sample pre-treatment (acidification). The electrolysis process aids decomposition of the organic matrix, and the release of trace elements. Evolution of H₂ at the cathode counters fouling of the Pd modifier surface. The palladium deposit is renewed in situ for each determination. For AMI certified lyophilised blood, diluted 1+3 with 0.1 M HCl (18.1 μg/l Pb), the R.S.D. was 3.0% (peak height; n=5) and the detection limit (3 σ_blank; n=5) was 1.5 μg/l. Results for certified blood samples were AMI 72.3±4.3 μg/l (certified 76.2±7.6 μg/l) and Seronorm 34.2±2.0 μg/l (36±4 μg/l). The result for NIST SRM 2670 normal urine acidified to 1% HNO₃ was 8.1±0.6 μg/l (recommended value 10 μg/l).     

碳纳米管/铜纳米结构电极材料在葡萄糖检测中的应用

利用电化学沉积法制备了碳纳米管/铜纳米结构电极材料, 采用扫描电子显微镜和电化学方法对电极表面的形貌和电化学性质进行了表征. 结果表明, 碳纳米管/铜纳米结构电极材料具有较大的电化学活性表面积、 高稳定性、 良好的导电性以及高葡萄糖电氧化活性, 有望用于葡萄糖的检测.     

电沉积铁族薄膜的磁性圆二色研究

采用循环伏安法在GaAs(100)单晶表面电沉积了铁族金属单质薄膜. 扫描电子显微镜(SEM)结果显示, Fe族金属薄膜的晶粒较小, 薄膜平整度较高。通过X射线衍射(XRD)谱分析了Fe, Co, Ni在GaAs(100)晶面上的外延生长. 使用磁光克尔效应装置研究了Fe族金属薄膜的宏观磁性, 用同步辐射圆偏振软X射线测量了铁族单质磁性薄膜的吸收谱, 获得了X射线磁性圆二色谱, 并通过加和定则计算了磁性薄膜中Fe族金属原子的轨道磁距和自旋磁矩.     

自组装纳米金膜上铂微/纳结构电催化剂的制备及性能

基于纳米金(AuNP)表面基团的静电自组装作用制备了多层有序的纳米金超薄膜. 研究了自组装纳米金超薄膜上铂微/纳结构催化剂(Pt/AuNP)的制备过程. 考察了沉积电位和沉积时间对甲酸电氧化活性的影响, 确定了最佳沉积电位为0 V, 最佳沉积时间为600 s. 同时对比考察了Pt/AuNP/PE/GCE, AuNP/PE/GCE和纯Pt电极在0.1 mol/L H2SO4介质中对甲酸电氧化活性以及载体对沉积物形态和甲酸氧化活性的影响. 研究结果表明, 纳米金组装体对铂的电沉积有明显的促进作用; Pt/AuNP/PE/GCE对甲酸的电氧化有很好的电催化性能.