Direct electrodeposition of gold nanoparticles onto indium/tin oxide film coated glass and its application for electrochemical biosensor

A novel electrochemical deposition method for growth of gold nanoparticles (GNPs) on indium tin oxide (ITO) thin film coated glass was investigated. The resulting electrode surface was characterized by SEM, UV–Vis spectroscopy and electrochemical methods. The GNPs directly attached on the electrode surface with a quasi-spherical shape and their sizes of diameters were in the range of 20–35 nm with a quite symmetric distribution. With increasing electrodeposition cycles of cyclic voltammetry, the density of GNPs on ITO electrode surface was increased. The potential utility of the GNPs modified ITO electrode was investigated. Superoxide dismutase (SOD) was successfully immobilized on GNPs modified ITO electrode and the direct electron transfer between enzyme and electrode surface realized. The enzyme electrode exhibited a rapid and high response to superoxide anion.     

A novel microchip based on indium tin oxide coated glass for contactless conductivity detection

A microfluidic chip manufactured from glass substrate and indium tin oxide (ITO) coated glass use for contactless conductivity detection was developed. The detecting electrodes were fabricated by screen-printing and chemical etching methods using an ITO-coated glass wafer. Then, the glass substrate containing separation channels was bonded with the bare side of the processed ITO-coated glass, thus producing an electrophoresis chip integrated with contactless conductivity detector. The prepared microchip displayed considerable stability and reproducibility. Sensitive response was obtained at optimal conditions (including the gap between electrodes, excitation frequency, and excitation voltage). The feasibility of this microfluidic device was examined by detection of inorganic ions, and further demonstrated by the quantification of aminopyrine and caffeine in a compound pharmaceutical. The two ingredients can be completely separated within 1 min. The detection limits were 8 μg mL⁻¹ and 3 μg mL⁻¹, respectively; with the correlation coefficient of 0.996-0.998 in the linear range from 10 μg mL⁻¹ to 800 μg mL⁻¹. The results have showed that the present method is sensitive, reliable and fast.     

Direct electrodeposition of gold nanoparticles onto indium tin oxide film coated glass: Application to the detection of arsenic(III).

Gold nanoparticle modified indium tin oxide (ITO) film coated glass electrodes were prepared for the first time through direct electrochemical deposition from 0.5 M H2SO4 containing 0.1 mM HAuCl4. The resulting electrode surfaces were characterized with AFM. Cyclic voltammetry and linear sweep voltammetry (LSV) of arsenic(III) on the modified electrodes were performed. After optimization, a LOD of 5 +/- 0.2 ppb was obtained with 60 s deposition at -0.6 V (vs. SCE) in 1 M HNO3 using LSV.     

Aqueous solution route to high-aspect-ratio zinc oxide nanostructures on indium tin oxide substrates

High-aspect-ratio ZnO nanowires and nanotubes are formed on indium tin oxide (ITO) substrates using a three-step route at low temperatures. The three steps, including successive ionic layer absorption and reaction (SILAR) deposition of the ZnO seed layer, hydrothermal annealing of the seed layer, and chemical bath deposition (CBD) of the one-dimensional (1D) ZnO nanostructures, are all conducted in aqueous solutions at temperatures below 120 degrees C. Both the hydrothermal annealing of the SILAR seed layer and the low-concentration precursor solution employed in the CBD process are crucial in order to synthesize the uniform and high-aspect-ratio ZnO nanostructures on the ITO substrate. TEM analyses reveal that both the nanowire and the nanotube possess the single-crystal structure and are grown along [001] direction. Room-temperature cathodoluminescence spectrum of the 1D ZnO nanostructures shows a sharp ultraviolet emission at 375 nm and a broad green-band emission.     

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.     

Morphological control of ZnO nanostructures by electrodeposition

We report here an electrodeposition route for the preparation of oriented and well-defined ZnO nanostructures by kinetically controlling the growth rates of various facets of the deposit by appropriate capping agents. We demonstrated that adsorption of Cl(-) takes places preferentially onto the (0001) planes to hinder the crystal growth along the c-axis, and results in the formation of platelet-like crystals. It is also shown that the morphology evolved from hexagonal tapers to hexagonal rods and rhombohedral rods by changing the compositions of the capping agents. Furthermore, strong UV emissions at 380 approximately 390 nm and negligible green bands at around 500 nm were observed, indicating that these ZnO electrodeposits are highly crystallized and of excellent optical quality.     

Surface engineering of one-dimensional tin oxide nanostructures for chemical sensors

Nanostructured materials are promising candidates for chemical sensors due to their fascinating physicochemical properties. Among various candidates, tin oxide (SnO₂) has been widely explored in gas sensing elements due to its excellent chemical stability, low cost, ease of fabrication and remarkable reproducibility. We are presenting an overview on recent investigations on 1-dimensional (1D) SnO₂ nanostructures for chemical sensing. In particular, we focus on the performance of devices based on surface engineered SnO₂ nanostructures, and on aspects of morphology, size, and functionality. The synthesis and sensing mechanism of highly selective, sensitive and stable 1D nanostructures for use in chemical sensing are discussed first. This is followed by a discussion of the relationship between the surface properties of the SnO₂ layer and the sensor performance from a thermodynamic point of view. Then, the opportunities and recent progress of chemical sensors fabricated from 1D SnO₂ heterogeneous nanostructures are discussed. Finally, we summarize current challenges in terms of improving the performance of chemical (gas) sensors using such nanostructures and suggest potential applications. Contains 101 references.

Electrodeposition and characterization of PbSe films on indium tin oxide glass substrates

Electrodeposition of lead selenide (PbSe) thin films on indium tin oxide (ITO) covered glass is described. While disodium salt of ethylenediaminetetraaceticacid was used to complex the lead ions, well crystallized, nearly stoichiometric and mirror-like PbSe films were deposited on ITO glass in potentiostatic mode using aqueous acidic electrolyte containing Pb and Se precursors at different bath temperature. The improvement of crystallinity of the PbSe films deposited at different temperature was studied using X-ray diffraction and Raman scattering. The morphology and composition of the films were characterized by scanning electron microscopy and energy disperse analysis by X-ray, respectively. The optical property of the film was studied by optical measurement techniques.     

Silver-nanoparticle-attached indium tin oxide surfaces fabricated by a seed-mediated growth approach

By applying a seed-mediated growth method that had been reported for the chemical synthesis of Ag nanorods and nanowires in aqueous solution, we successfully attached Ag nanosphere and nanorod particles to indium tin oxide (ITO) surfaces. In this method, it is characteristic that the attachment can be performed without using bridging reagents, such as 3-mercaptopropyltrimethoxysilane, but rather through a two-step immersion into the seed solution first and then into the growth solution containing AgNO(3), cetyltrimethylammonium bromide, and ascorbic acid. It was found that the formed nanostructures were very sensitive to the amount of ascorbic acid in the growth solution. Whereas Ag nanoparticles grew on the ITO surface with a moderate dispersion when the concentration of ascorbic acid in the growth solution was 0.64 mM, the formation of nanorods and nanowires was observed when the ascorbic acid concentration was increased to 0.86 mM. The attachment of Ag nanoparticles onto the ITO surfaces was strong enough for further use, e.g., as a working electrode. From electrochemical measurements, it was confirmed that the outer spheres of the Ag nanoparticles involved in the redox reaction show the typical oxidation and reduction waves of Ag. In addition, the redox behavior of [Fe(CN)(6)](3-)/[Fe(CN)(6)](4-) was improved on the Ag-nanoparticle-attached ITO (AgNP/ITO) electrode, reflecting the low electron-transfer resistivity, which is a remarkable advantage of the present fabrication without using bridging reagents. This result indicated that the Ag nanoparticles promote the electron-transfer reactions by being present on the conducting ITO surface. The AgNP/ITO electrode was examined for the reduction of the methyl viologen dication in order to discuss some features of the present fabrication.     

Photoelectrochemical sensing for hydroquinone based on gold nanoparticle-modified indium tin oxide glass electrode

Gold nanoparticles (GNPs) were deposited directly onto the surface of indium tin oxide (ITO) thin film-coated glass by electrochemical method. It was used as a photoanode in a photoelectrochemical (PEC) cell for sensitive detection of hydroquinone (HQ) at an applied bias potential of 0.15 V vs. saturated calomel electrode. This heterostructure showed dramatically enhanced PEC properties due to the introduction of the Au/ITO interface. Under the irradiation, the marked photocurrent response was observed at the GNPs/ITO photoelectrode compared with bare ITO electrode. The anodic photocurrent could be further largely enhanced by HQ. A new PEC strategy for sensitive detection of HQ at a relative low potential was developed. The linear range for HQ determination was 0.25 to 150 μM, with a detection limit of 0.1 μM. The sensitivity on the GNPs/ITO electrode at the irradiation was ~ 3.3 times higher than that in dark. These results demonstrate that the simple GNPs/ITO electrodes have great potential for PEC analysis application.     

Electrodeposition of large size gold nanoparticles on indium tin oxide glass and application as refractive index sensor

Large size gold nanoparticles (GNPs) were directly deposited onto the indium tin oxide (ITO) glass surface by cyclic voltammetric method. The GNPs on ITO substrate were characterized by means of scanning electron microscopy (SEM), UV–vis spectroscopy and X-ray diffraction (XRD). The nucleation and growth steps were controllable in the GNPs deposition procedure. The addition of chloride ion in the electrolysis affected the size and density of GNPs on the ITO surface. The response of refractive index for various organic solvents was also investigated. The sensitivity of refractive index increased as GNPs became larger.     

Controlled growth of metallic inverse opals by electrodeposition

The kinetics of nickel electrodeposition through a template of ordered polystyrene spheres is addressed experimentally and applied to prepare a series of metallic inverse opals with a non-integer number of layers. The observed layer-by-layer growth is discussed in terms of subsequently increasing disorder of the growth front. Reflection and transmission spectra of the samples demonstrate that the key optical features of these photonic crystals are most pronounced when the thickness does not essentially exceed two layers. The intensities and band positions can be additionally tuned by varying the height of the metal coating continuously, not discretely. These findings are confirmed semi-quantitatively by means of computational modeling of the spectra. Specific deposition current transients for in situ control of geometric parameters are discussed.     

Seed-mediated growth of palladium nanocrystals on indium tin oxide surfaces and their applicability as modified electrodes

Palladium nanoparticles (PdNPs) were successfully attached and grown on an indium tin oxide (ITO) surface using a seed-mediated growth method, i.e., via a simple two-step immersion of the ITO substrate into the seed and growth solutions. After the growth treatment for 24 h, PdNPs grew up to 60-80 nm, exhibiting crystal-like appearances and accompanying the formation of short rodlike nanocrystals as a minor product. Thus prepared PdNPs tend to stick each other, so that the dense gathering of PdNPs was observed on the ITO surfaces. Due to the dense attachment, the PdNPs directly attached to the ITO (PdNP/ITO) electrode had a significantly lowered charge-transfer resistivity compared with that of a bare ITO, and the redox reaction of [Fe(CN)6]3-/[Fe(CN)6]4- was observed as reversible in 0.1 M phosphate buffer solution. The electrocatalytic property of PdNPs was confirmed for the reduction of oxygen. In addition, some typical responses were observed in 0.5 M H2SO4 with the PdNP/ITO electrode, reflecting both the characteristics of NPs and the thin layer in nanoscale. The present preparation method of PdNP-attached surfaces would be promising for catalytic applications as well as electrochemical uses.     

Determination of fluoride and tin in fluoride-doped tin oxide films on glass

Time-consuming fusion and pyrohydrolysis methods for quantifying fluoride and tin in fluoride-doped tin oxide films on glass are replaced by a simple electrolytic reduction for sample preparation. The unusual conductivity of these films enables solutions to be produced in which fluoride can be quantified by ion chromatography. Tin is quantified in the original sample by x-ray fluorescence spectrometry. Electrolytic reduction and the fusion/pyrohydrolysis methods are compared for films with Sn/F ratios of 10–40 (71–183 μg cm^?2 tin and 0.54–2.8 μ cm^?2 fluoride). The Sn/F ratios and precision are similar for the two methods. The older method only yields the tin/fluoride ratio; the electrolytic method gives results as mass per unit area and requires much less time per sample.     

Electrochemical sensing of CO by gold particles electrodeposited on indium tin oxide substrate

The gold submicroparticles (AuSMPs) electrodeposited on indium tin oxide (ITO) were used to develop an electrochemical method for determining the concentration of CO in gas phase. We demonstrated that the peak current for CO oxidation in cyclic voltammetry (CV) is proportionally dependent on the gas phase concentration of CO. Experimental results are in good agreements with the theoretical predictions over a wide concentration regime, providing a solid foundation for the quantitatively sensing of CO at AuSMPs/ITO electrodes.     

In situ chemical reductive growth of platinum nanoparticles on indium tin oxide surfaces and their electrochemical applications

Platinum nanoparticles directly attached to indium tin oxide (PtNP/ITO) were successfully fabricated by using an in situ chemical reductive growth method. In this method, PtNPs could be grown on the ITO surface via the one-step immersion into the growth solution containing PtCl4(2-) and ascorbic acid. The attached and grown PtNPs were spherical having an agglomerated nanostructure composed of small nanoclusters. From the morphological changes depending on the growth time, which were observed with an FE-SEM, PtNPs were found to be grown via the progressive nucleation mechanism. As the characteristics of the PtNP/ITO were those of a working electrode, it was found that the charge transfer resisivity was significantly lowered due to the grown PtNPs. Hence, for a typical redox system of [Fe(CN)6]3-/[Fe(CN)6]4-, the PtNP/ITO electrode exhibited the electrochemical responses similar to those of the bulk Pt electrode. Furthermore, it was clarified that the PtNP/ITO electrode had significant electrocatalytic properties for the oxygen reduction and methanol oxidation. The present PtNPs that had the agglomerated nanostructure may be promising for a new type of electrode material.     

Generic top-functionalization of patterned antifouling zwitterionic polymers on indium tin oxide

This paper presents a novel surface engineering approach that combines photochemical grafting and surface-initiated atom transfer radical polymerization (SI-ATRP) to attach zwitterionic polymer brushes onto indium tin oxide (ITO) substrates. The photochemically grafted hydroxyl-terminated organic layer serves as an excellent platform for initiator attachment, and the zwitterionic polymer generated via subsequent SI-ATRP exhibits very good antifouling properties. Patterned polymer coatings can be obtained when the surface with covalently attached initiator was subjected to photomasked UV-irradiation, in which the C-Br bond that is present in the initiator was broken upon exposure to UV light. A further, highly versatile top-functionalization of the zwitterionic polymer brush was achieved by a strain-promoted alkyne-azide cycloaddition, without compromising its antifouling property. The attached bioligand (here: biotin) enables the specific immobilization of target proteins in a spatially confined fashion, pointing to future applications of this approach in the design of micropatterned sensing platforms on ITO substrates.     

Development of silver/gold nanocages onto indium tin oxide glass as a reagentless plasmonic mercury sensor

We demonstrate the utilization of silver/gold nanocages (Ag/Au NCs) deposited onto transparent indium tin oxide (ITO) film glass as the basis of a reagentless, simple and inexpensive mercury probe. The localized surface plasmon resonance (LSPR) peak wavelength was located at ∼800 nm. By utilizing the redox reaction between Hg²⁺ ions and Ag atoms that existed in Ag/Au NCs, the LSPR peak of Ag/Au NCs was blue-shifted. Thus, we develop an optical sensing probe for the detection of Hg²⁺ ions. The LSPR peak changes were lineally proportional to the concentration of Hg²⁺ ions over the range from 10 ppb to 0.5 ppm. The detection limit was ∼5 ppb. This plasmonic probe shows good selectivity and high sensitivity. The proposed optical probe is successfully applied to the sensing of Hg²⁺ in real samples.