Electrokinetic patterning of colloidal particles with optical landscapes

We demonstrate an opto-electrokinetic technique for non-invasive particle manipulation on the surface of a parallel-plate indium tin oxide (ITO) electrode that is biased with an alternating current (AC) signal and illuminated with near-infrared (1064 nm) optical landscapes. This technique can generate strong microfluidic vortices at higher AC frequencies (>100 kHz) and dynamically and rapidly aggregate and pattern particle groups at low frequencies (<100 kHz).     

Colloidal deposition on remotely controlled charged micropatterned surfaces in a parallel-plate flow chamber

This article describes a method to influence colloid deposition by varying the zeta potential at microelectrodes with remotely applied electric potentials. Deposition experiments were conducted in a parallel-plate flow chamber for bulk substrates of glass, indium tin oxide (ITO), and ITO-coated glass microelectrodes in 10 and 60 mM potassium chloride solutions. Colloid deposition was found to be a function of solution chemistry and the small locally delivered electric surface potentials. Electric fields and physical surface heterogeneity can be ruled out as cause of the observed deposition. Results are reported using experimentally determined Sherwood numbers and compared to the predictions of a previously developed patch model. Minor deviations between predicted and experimental Sherwood numbers imply that physical and chemical interactions occur. Specifically, we propose that colloidal particles respond to local variations in surface potential through electrostatic interactions, altering particle streamlines flowing along the surface and ultimately the extent of deposition.     

Gold nanoparticles attached NH2+ ion implantation-modified indium tin oxide electrode: Characterization and electrochemical studies

An NH2+ ion implantation-modified indium tin oxide film was prepared and the implantation of amino groups on the indium tin oxide substrate was verified by X-ray photoelectron spectroscopy analysis.The gold nanoparticles attached surface could be obtained by self-assembly of different sized colloidal gold nanoparticles onto the NH2+ ion implantation-modified indium tin oxide surface.By scanning electron microscopy and electrochemical techniques,the as-prepared AuNPs attached NH2+ ion implantation-modified indium tin oxide electrode was characterized and compared with bare indium tin oxide electrode.Using a [Fe(CN)6]3 /[Fe(CN)6]4 redox probe,the increasingly facile heterogeneous electron transfer kinetics resulting from the attached gold nanoparticle arrays was observed.The gold nanoparticle arrays exhibited high catalytic activity toward the electro-oxidation of nitric oxide,which could provide electroanalytical application for nitric oxide sensing.     

纳米TiO_2修饰电极对鲁米诺电化学发光的增敏及TiO_2晶型的影响

该文水解合成并通过煅烧改变晶型,获得了金红石和锐钛矿两种晶型混合的二氧化钛纳米粒子。利用紫外可见分光光度法(UV-Vis)、激光粒度分析(LPSA)、X射线多晶衍射分析(XRD)和冷场发射扫描电镜(SEM)等方法对样品进行了表征。制备了以氧化铟锡(ITO)玻璃为基底的纳米TiO2修饰电极,并研究了晶型对鲁米诺电化学发光(ECL)的增敏作用的影响。结果表明,当粒径较小,经650℃煅烧处理形成混晶时,纳米TiO/ITO修饰电极对鲁米诺电化学发光的增敏效果最明显,为裸电极的7.5倍。     

Optoelectric patterning: Effect of electrode material and thickness on laser‐induced AC electrothermal flow

Rapid electrokinetic patterning (REP) is an emerging optoelectric technique that takes advantage of laser‐induced AC electrothermal flow and particle‐electrode interactions to trap and translate particles. The electrothermal flow in REP is driven by the temperature rise induced by the laser absorption in the thin electrode layer. In previous REP applications 350–700 nm indium tin oxide (ITO) layers have been used as electrodes. In this study, we show that ITO is an inefficient electrode choice as more than 92% of the irradiated laser on the ITO electrodes is transmitted without absorption. Using theoretical, computational, and experimental approaches, we demonstrate that for a given laser power the temperature rise is controlled by both the electrode material and its thickness. A 25‐nm thick Ti electrode creates an electrothermal flow of the same speed as a 700‐nm thick ITO electrode while requiring only 14% of the laser power used by ITO. These results represent an important step in the design of low‐cost portable REP systems by lowering the material cost and power consumption of the system.     

Self-assembly of active IrO2 colloid catalyst on an ITO electrode for efficient electrochemical water oxidation

Active catalysts for water oxidation to evolve O(2) are required for the construction of artificial photosynthetic devices that are expected to be promising energy-providing systems in the future. The citrate-stabilized IrO(2) colloid was self-assembled onto an indium tin oxide (ITO) electrode to form a monolayer of the colloidal IrO(2) particles when it was dipped in the colloid solution. The self-assembly could be achieved by a chemical interaction between carboxylate groups on the citrate stabilizer and hydroxyl groups on the ITO surface to form ester bonds. Efficient electrocatalysis for water oxidation was demonstrated using the electrode modified by the self-assembled IrO(2) colloid to yield the highest turnover frequency ((2.3-2.5) x 10(4) h(-1)) of IrO(2) in the hitherto-reported catalysts for electrochemical water oxidation.     

Surface-enhanced Raman spectroscopy using silver nanoparticles on a precoated microscope slide

A chemical reduction method was applied to deposit nano silver particles on a frosted microscope slide, precoated with indium tin oxide. The substrate was used to collect the surface-enhanced Raman spectrum of N1'-ethyl indirubin monooxime (EIM), a potential chemical for pharmaceutical application. From the observed surface-enhanced Raman scattering (SERS) spectrum, EIM might interact with silver surface through the lone pair electrons of the oxime nitrogen atoms. Crystal violet (CV) and p-nitrobenzoic acid (PNBA) were also used to test the SERS probe capability of the substrate. The surface morphorlogy of the substrate has been characterized by using scanning electron microscope (SEM) and atomic force microscope (AFM). The elementary composition was identified with Edex and X-ray element scanning.     

Development of a new contactless dielectrophoresis system for active particle manipulation using movable liquid electrodes

This study presents a new DEP manipulation technique using a movable liquid electrode, which allows manipulation of particles by actively controlling the locations of electrodes and applying on–off electric input signals. This DEP system consists of mercury as a movable liquid electrode, indium tin oxide (ITO)‐coated glass, SU‐8‐based microchannels for electrode passages, and a PDMS medium chamber. A simple squeezing method was introduced to build a thin PDMS layer at the bottom of the medium chamber to create a contactless DEP system. To determine the operating conditions, the DEP force and the friction force were analytically compared for a single cell. In addition, an appropriate frequency range for effective DEP manipulation was chosen based on an estimation of the Clausius–Mossotti factor and the effective complex permittivity of the yeast cell using the concentric shell model. With this system, we demonstrated the active manipulation of yeast cells, and measured the collection efficiency and the dielectrophoretic velocity of cells for different AC electric field strengths and applied frequencies. The experimental results showed that the maximum collection efficiency reached was approximately 90%, and the dielectrophoretic velocity increased with increasing frequency and attained the maximum value of 10.85 ± 0.95 μm/s at 100 kHz, above which it decreased.     

Electrowetting of superhydrophobic ZnO nanorods

This paper reports the electrowetting properties of ZnO nanorods. These nanorods were grown on indium tin oxide (ITO) substrates using different liquid-phase deposition techniques and hydrophobized with sputtered Teflon. The surfaces display superhydrophobic properties. When the applied voltages are less than 35 V, the contact angle change is small and exhibits instant reversibility. For higher voltages, larger contact angle changes were observed. However, the surface was not reversible after removing the applied voltage and required mechanical agitation to return to its initial superhydrophobic state.     

Electrochemical deposition of silver nanoparticles in multiwalled carbon nanotube-alumina-coated silica for surface-enhanced Raman scattering-active substrates

The work presents a novel surface-enhanced Raman scattering (SERS)-active surface prepared by electrochemical deposition of silver nanoparticles in multiwalled carbon nanotube (MWCNT)–alumina-coated silica (ACS) nanocomposite. The formation of Ag nanoparticles in MWCNT–ACS nanocomposite was investigated by scanning electron microscopy. It shows that Ag nanoparticles with a diameter of about 100–200 nm in the MWCNT–ACS nanocomposite and some Ag nanoparticles aggregated to form interconnected aggregates. The Ag–MWCNT–ACS-coated indium tin oxide substrate has a considerable effect on the Raman spectra with improvements of more than four times of magnitude as compared with the Ag-coated indium tin oxide substrate. The present methodology demonstrates that the composite composed of Ag, MWCNT, and ACS is suitable for potential plasmonic devices.     

电泳沉积制备ZnO-C60和ZnO-MWCNT合涂层电极及其光电性质

在氧化铟锡( ITO)导电玻璃表面电泳沉积制备ZnO-C60和ZnO-MWCNT复合涂层电极,经后续热处理增强其结合强度,通过SEM观察2种电极复合涂层的表面形貌,并使用CHI 705电化学分析仪和PMI-E电致化学发光系统测定其光电性质.结果表明,ZnO-C60复合涂层电极具有较高的稳定性,在可见光辐照下,该电极显示...     

Polypeptide-mediated silica growth on indium tin oxide surfaces

Herein, we describe the formation of silica structures on indium tin oxide (ITO) surfaces using poly-L-lysine (PLL) to template the condensation of silicic acid. Precisely controlled electrostatic fields were used to preposition PLL onto ITO surfaces. Subsequent polypeptide-mediated silicification resulted in the formation of silica with concentration gradients that followed the pattern of the externally applied electrostatic field used in the deposition of the PLL. The resulting silica structures were securely attached to the ITO surface. The technique described here offers an inexpensive and rapid method for the deposition of polypeptides on surfaces.     

Photoinduced thermal copper reduction onto gold nanocrystals under potentiostatic control

We study the photoreduction of adsorbed copper ions onto Au nanoparticles, on an indium tin oxide (ITO) electrode in an aqueous electrochemical cell, as a function of applied voltage and laser intensity. The photocurrent is a nonlinear function of laser intensity and increases sharply with cathodic voltage in the underpotential deposition region. The photoreduction is attributed to laser heating of the Au nanoparticles rather than "hot electron" processes. Numerical simulation of the Butler-Volmer kinetic equation using experimental parameters predicts a several orders of magnitude increase in current for a temperature rise of a few Kelvin.     

Optical transmittance of indium tin oxide nanoparticles prepared by laser-induced fragmentation in water

Laser-induced fragmentation of indium tin oxide nanoparticles was performed in water by laser irradiation with various laser energies. Fragmentation of the nanoparticles proceeded with increased laser energy. The fragmented nanoparticles showed high transmittance in the visible region and lower transmittance in the ultraviolet and infrared regions. The optical band gap of the fragmented nanoparticles increased with decreasing average particle size. The increase of the band gap was possibly caused by the Burstein-Moss effect due to the increasing concentration of carriers generated by the surface defects of the oxygen vacancies on smaller nanoparticles.     

One-step Growth of Hierarchical Nanotreelike TiO_2 on ITO without Template and Its Application in Gas Sensor

In this work, a distinctive hierarchical tree-like rutile TiO_2 architecture growing directly on the conductive surface of indium tin oxide(ITO) conductive glass substrates was successfully prepared via a facile one-step hydrothermal process, where titanium butoxide used as Ti source and HCl as an acidic medium solution. The as-obtained products were characterized by X-ray diffraction(XRD), field emission scanning electron microscopy(FE-SEM), transmission electron microscopy(TEM), selected area electron diffraction(SAED) and applied in gas sensor. The characterization of FE-SEM indicates that the morphology of the products can be controlled by regulating solution acidity, the amount of titanium butoxide, reaction time, addition agents, and so on. The gas sensing test shows that the sensor fabricated with 3D nanotree-like rutile TiO_2 has higher gas response towards CH3 COCH3 gas than those with 1 D rod-like TiO_2 or common TiO_2 precipitate, indicating that the 3D nanotree-like architectures may be promising gas sensitive materials.     

Low-Temperature Synthesis of ITO Thin Films Using an Ultraviolet Laser for Conductive Coating on Organic Polymer Substrates

The resistivity of sol-gel-derived indium tin oxide (ITO) films effectively decreased with crystallization by exposure to a low fluence UV beam (10–20 mJ/cm²) from an ArF laser. The increase in temperature at the surface of the films was below 10°C under the irradiation condition. Thus, conductive and transparent ITO coatings were successfully obtained on polyethylene terephthalate and polyimide sheets using a sol-gel route assisted with an ultraviolet laser beam.     

A facile method of achieving low surface coverage of Au nanoparticles on an indium tin oxide electrode and its application to protein detection

Low surface coverage of Au nanoparticles on an indium tin oxide electrode for sensitive electrochemical detection was achieved using electrostatic adsorption of AuCl(4)(-) followed by reduction.     

PICA法制备用于高效液相色谱的锆胶基质柱填料

迄今 ,硅胶基质固定相在 HPLC领域仍占据主导地位 ,但由于它的 p H使用范围窄 ,尤其在碱性条件下基质逐渐溶解 ,其使用受到限制 [1] .为此 ,寻找稳定性能高的新基质成为当前色谱学研究的热点之一 ,二氧化锆因具有良好化学稳定性和机械强度而受到关注 .目前 ,制备微米级、球形和多孔二氧化锆基质柱填料的常用方法有两种 :(1 )油乳化法 (OEM) ;(2 )聚合诱导胶体凝聚法 (PICA) .OEM法操作简单 ,但制备的二氧化锆微球粒径分布宽且孔径较小 .Carr[2 ,3] ,Unger[4 ] ,Rassi[5,6 ]和 Kawahara等[7,8] 在用 OEM法制备二氧化锆微球方面做了…     

An indium tin oxide electrode modified with gold nanorods for use in potential-controlled surface plasmon resonance studies

The modification of electrodes with gold nanoparticles results in an increased electrode surface area, enhanced mass transport, and improved catalytic properties. We have extended this approach to indium tin oxide (ITO) electrodes to obtain optically transparent gold nanorod-modified electrodes which display enhanced electrochemical capabilities and have the additional advantage of showing a tunable surface plasmon resonance. The procedures for attaining high surface coverage (15 gold nanorods per square µm) of such electrodes were optimized, and the potential-dependent surface plasmon resonance was studied under controlled electrical potential. In an exemplary sensor application, we demonstrate the detection of mercury via potential-dependent formation of an Au-Hg amalgam.

ITO上AuPd合金和Au阵列图案的制备及电催化活性的SECM表征

利用电化学湿法印章技术在氧化铟锡(ITO)导电玻璃上制备AuPd合金和Au的双组分阵列图案. 采用具有微浮雕图案的琼脂糖印章存储足够多的溶液,并通过控制电沉积的时间来控制图案厚度. 应用场发射扫描电子显微镜(FE-SEM),X射线能谱分析(EDX)和原子力显微镜(AFM)分别对ITO表面上的AuPd合金和Au的形貌和组分进行表征,并通过循环伏安(CV)技术和扫描电化学显微镜(SECM)研究比较了Au和AuPd合金的催化活性. 利用扫描电化学显微镜(SECM)的针尖产生-基底收集(TG-SC)模式和氧化还原竞争(RC)模式,发现Au电极对二茂铁甲醇氧化物(FcMeOH⁺)电催化还原能力高于AuPd合金电极,而在AuPd合金上催化还原H₂O₂的能力显著高于Au.