Functionalized Indium Tin Oxide Research Articles

Fabrication of a label-free electrochemical cell-based biosensor for toxicity assessment of thiram

Thiram has been widely used in agriculture and may invades the food chain, posing a threat to human health. In this research, a label-free electrochemical cell-based biosensor was presented for in vitro toxicity assessment of thiram. HepG2 cells were cultured on poly-l-lysine@gold nano-flowers functionalized indium tin oxide coated glass electrode (PLL@AuNFs/ITO) to serve as biorecognition elements. AuNFs were electrodeposited on ITO to provide an enlarged specific surface area and benefited the output signal amplification. PLL was selected as an effective biocompatible coating material to facilitate cell adhesion and proliferation, thereby realizing one-step recording of electrochemical signals from thiram-treated cells. With the aid of the differential pulse voltammetry method, the fabricated biosensor was applied to assess the cytotoxicity of thiram. Results showed that the cytotoxicity measured by the fabricated biosensor exhibited a linear relationship related to thiram concentration ranging from 5 to 50 μM with a detection limit of 2.23 μM. The IC50 of thiram obtained by the biosensor was 29.5 μM, which was close to that of conventional MTT assay (30.8 μM). The effects of thiram on HepG2 cells were also investigated via SEM and flow cytometry. Meanwhile, the proposed biosensor was used to evaluate the toxicity of thiram in fruit samples. Results indicated that the toxicity of thiram cannot be ignored even at a low residual concentration in food (≤5 mg/kg). In conclusion, the developed sensor showed excellent sensitivity, stability, and reliability, which provided a great capacity for the convenient toxicity evaluation of thiram residue in food.

Determination of calreticulin using Fe3O4@AuNPs core-shell functionalized with PT(COOH)2 polymer modified electrode: A new platform for the impedimetric biosensing of cancer biomarkers

An innovative biosensing design strategy was utilized for the first time to develop a label-free and practical immunosensor for ultrasensitive analysis of calreticulin (CRT), a potential biomarker of breast carcinoma. Unlike strategies used in literature, a conjugated polymer carrying carboxyl groups on its backbone was synthesized and utilized as an immobilization matrix. This immunosensor design strategy was composed of the attachment of anti-CRT antibodies onto iron oxide nanoparticles@gold nanoparticles@poly(3-thiophenemalonic acid) polymer (Fe3O4@AuNPs@PT(COOH)2) functionalized indium tin oxide (ITO) electrode through carbodiimide coupling reaction. EIS measurement results illustrated significant changes in charge transfer resistance (Rct) on immunoreaction between anti-CRT and CRT proteins. The proposed immunosensor enabled the detection of CRT over the range of 0.02 pg/mL and 100 pg/mL with a correlation coefficient of 0.9994 under optimal conditions. The detection limit (LOD), the quantification limit (LOQ) and the sensitivity were also determined to be 8.2 fg/mL, 27.4 fg/mL and 270 kΩ fg mL−1cm2, respectively. Furthermore, it also exhibited good repeatability, excellent reproducibility, long storage stability and reusability. Experimental results analyzed with T-test to compare the means of the repeatability and reproducibility data, and F-test to the distribution of the repeatability and reproducibility data. According to T and F-tests, the experimental results achieved from the studies with the suggested immunosensor were relatively satisfactory. Furthermore, this immunosensor was tested to measure CRT levels in human serum and spiked human serum samples, and acceptable recovery rates ranging from 94.05% to 106.62% were obtained. In sum, considering its fast and easy-to-fabricate properties, this new strategy offers a potential tool for CRT biomarker detection.

Planar and Vertical Alignment of Rod-like and Bent-core Liquid Crystals Using Functionalized Indium Tin Oxide Substrates

ABSTRACT Indium tin oxide (ITO) substrates are chemically modified with bent-shaped molecules and influence of these surface immobilised molecules on the alignment of bulk liquid crystal (LC) samples has been investigated. Bent-core (BC) compounds containing a dimethylchlorosilane moiety at the end of a terminal alkyl chain and a lateral alkyl chain are successfully attached to transparent conducting ITO substrates in an end-on (ITO-BC-t) and side-on (ITO-BC-l) oriented fashion to create stable permanent self-assembled BC layers on the substrates. Surface functionalization is thoroughly characterised and aligning ability of these BC-modified ITO substrates for orientation of bulk LC sample is evaluated for nematic phase of both rod-like and BCLC samples. The BC-modified substrates are effective in aligning the rod-like compounds in vertical (ITO-BC-t), planar orientations (ITO-BC-l) and the BC compounds in homeotropic (ITO-BC-t) alignment.

Nanostructured Mesoporous Carbon Based Electrochemical Biosensor for Efficient Detection of Swine Flu

AbstractIn the serum sample of swine flu patients, the novel Serum Amyloid A (SAA) protein has been secreted in higher concentration (49.4±14.1 μg mL−1) with respect tothe normal subject (12.2±15.0 μg mL−1), so SAA protein has been used in swine flu diagnosis. In present work, we developed nanostructured mesoporous carbon (mPC) based electrochemical biosensor for the swine flu detection. The mPC was synthesized through the thermal decomposition process, and with 3‐aminopropyltriethoxy silane (APTES), amine functionalization of mPC was carried out. The obtained product was further deposited onto the functionalized indium tin oxide (ITO) coated glass electrode using electrophoretic deposition unit with 40V DC voltage for 150 sec. Next, biofunctionalization with monoclonal anti‐SAA antibodies (anti‐SAA) was carried out onto the APTES/mPC/ITO electrode by EDC‐NHS covalent chemistry and bovine serum albumin (BSA) was used to block non‐specific binding sites. The structural and morphological, characterization of the mPC and fabricated electrodes were investigated using X‐ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and Fourier‐transform infrared spectroscopy. However, surface area and porosity analysis were investigated via Brauner‐Emmett‐Teller technique. Next, the electrochemical characterization and response studies were performed by cyclic voltammetry technique. The fabricated biosensing platform (BSA/anti‐SAA/APTES/mPC/ITO) exhibited excellent sensitivity of 1.69 μA mL μg−1 cm−2, wider linear detection range between 30–70 μg mL−1 with a limit of detection of 3.1 μg mL−1. The biosensing performance of the fabricated biosensing platform was also investigated in artificial serum samples and showed a good correlation with the obtained electrochemical response.

The role of amine in the sequestration of As (III) on functionalized indium tin oxide

The influence of arsenite (As(III)) adsorption on 3-amino-propyl phosphonic-acid (3APPA) has been investigated using X-ray photoemission spectroscopy (XPS), vibrational IR and Raman spectroscopy. The functional amino group on 3APPA appears to play a significant role in the adsorption mechanism. Results of a combined experimental and theoretical investigation provide a comprehensive picture of the geometry and vibrational properties of 3APPA monolayers after interaction with arsenite. Experimental and scaled calculated IR properties display good agreement for the model case where NH2 groups, located as pendant groups on 3APPA surface, interact with the adsorbed As-O network. A charge transfer to the As-O moiety is also indicated by XPS measurements and ionization potential maps generated by DFT. Thus, 3APPA, as a functionalized bio-adsorbant, shows promise towards detection and remediation of As(III) in contaminated wastewater.

A label-free immunosensor for sensitive detection of RACK 1 cancer biomarker based on conjugated polymer modified ITO electrode

A new flexible biosensor based on conjugated polymer functionalized indium tin oxide (ITO) sheet was fabricated for Receptor for Activated C Kinase 1 (RACK 1) determination. Poly(3-thiophene acetic acid) (P(Thi-Ac)) was used as an immobilization matrix for construction of RACK 1 immunosensor. This polymer had a great number of carboxyl groups on its end site and these carboxyl ends provided anchoring points to the anti-RACK 1 antibodies. Anti-RACK 1 antibodies were covalently attached on the ITO electrode and recognized the RACK 1 antigens. Electrochemical characterizations were made by employing electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. Additionally, single frequency impedance method (SFI) was applied to follow the specific biointeraction between antibody and antigen. As a result of specific biointeraction, the designed immunosensor exhibited a wide linear detection range between 0.01 pg/mL and 2 pg/mL RACK 1 with a detection limit of 3.1 fg/mL. Scanning electron microscopy and atomic force microscopy analyses were employed for electrode surface morphology investigation. The designed RACK 1 biosensor had good repeatability (5.73 %, RSD), excellent reproducibility (2.5 %, RSD), long storage-stability and reusable property. In addition, the fabricated RACK 1 biosensor was applied to determine RACK 1 concentration in human serums and the recovery was ranging from 98.79%–100.22%. This work illustrated a new tool to construct a sensitive and low-cost disposable biosensor for applications in clinical monitoring.

Antimicrobial activity of T4 bacteriophage conjugated indium tin oxide surfaces

We report the antimicrobial activity of bare and surface functionalized indium tin oxide (ITO) conjugated with T4 bacteriophage towards E. coli. A ∼ 103-fold reduction (99.9%) in the bacterial concentration was achieved within 2 h exposure of E. coli to the bare as well as the amine, carboxylic and methyl functionalized ITO/T4 surfaces. Despite the known differences in bacteriophage loading of these ITO/T4 systems, the almost identical extent of antimicrobial activity of all of the ITO/T4 systems resulted from the release of a comparable amount of infective T4 from the systems. As anticipated, a single dose of immobilized bacteriophage was sufficient to eliminate further surge of bacterial population. Upon the 2 h eradication of the ‘1st batch’ of E. coli population, all of the ITO/T4 systems, each system with 102-fold more suspended bacteriophage (due to propagation of the phage at the expense of the ‘1st batch’ E. coli death), reduced the ‘2nd batch’ of E. coli concentration by ∼104-fold in just 30 min, suggesting the potential of immobilized bacteriophage systems as solution to the issues of antimicrobial agent depletion. All of the ITO/T4 systems maintained their antimicrobial activity in the presence of model food components. The antimicrobial activity was however, affected by pH; at pH 5 whereby the bacteria’s growth was physiologically inhibited, generally no reduction in E. coli concentration was detected. The present work provides an understanding of the mode of antimicrobial activity exhibited by an immobilized bacteriophage based substrate and demonstrates efficacy in the presence of food components.

Adsorption kinetics of phosphonic acids and proteins on functionalized Indium tin oxide surfaces using electrochemical impedance spectroscopy

Phosphonic acids (PAs) are known to have a spontaneous affinity for chemisorption onto several metal oxide surfaces. The self – assembled monolayer (SAM) of phosphonates provides a platform for further surface modifications using biomolecules that can be adopted for the development of sensors and biosensors. With this in view, we studied adsorption kinetics of different phosphonic acids of short chain lengths such as phosphonopropionic acid (PPA), aminobenzylphosphonic acid (ABPA), benzylphosphonic acid (BPA), butylphosphonic acid (BuPA), and a long chain decylphosphonic acid (DecPA) on ITO surface using electrochemical impedance spectroscopy (EIS) at short and long time scales. The dependence of solution concentration on formation kinetics is studied and the existences of two discrete kinetics were revealed. We show from our studies that the rate of adsorption is controlled by diffusion at small time scales. Further, the phosphonic acid modified surface is also used as a substrate for the adsorption of cytochromeC (CytC) (a heme protein) and urease (an enzyme) and the kinetics of their adsorption has been studied.

A new strategy to develop the disposable label-free immunosensor with electrochemiluminescent probing

In this paper, a new strategy to prepare the label-free immunosensor signaling with the electrochemiluminescence (ECL) of luminol will be reported. The gold nano-particles (AuNPs) functionalized indium tin oxide coated glass is used as the substrate for antibody immobilization. These AuNPs also improve the ECL behavior of luminol. This strategy for immunosensor construction is simple, fast, cheap, and with no requirements of expensive apparatus. For validating the practicability of this new strategy, with methamphetamine (MA) as target model, an MA sensor was built by immobilizing the MA-antibody onto the surface of previously mentioned substrate. The ECL intensity on resultant sensor, after the direct immuno-interaction, decreased proportional to the concentration of MA in a wide linear range from 2 to 500ngmL−1 with a detection limit of 0.3ngmL−1. This proposed sensor is sensitive, specific, stable and reliable. It has been successfully applied to detect the MA in spiked human serums.

Surface assembly of nano-metal organic framework on amine functionalized indium tin oxide substrate for impedimetric sensing of parathion

The present paper reports the assembly and pesticide sensing application of a nanometal organic framework [Cd(atc)(H2O)2]n (‘atc’=2-aminoterephthalic acid). The assembly of the NMOF film has been achieved by sequential dipping of a 2-aminobenzylamine (2-ABA) modified indium tin oxide (ITO) slide in organic linker ‘atc’ and metal ion ‘Cd2+’ solutions. The different structural and morphological characteristics of the NMOF thin film have been characterized. The availability of pendent –COOH functional groups on the assembled NMOF film is exploited to synthesize a pesticide immunosensor by conjugating the NMOF film with anti-parathion antibody. This immunosensor has been explored for the electrochemical impedance spectroscopy (EIS) based analysis of parathion in the concentration range of 0.1–20ng/mL. The proposed detection is specific with respect to other organophosphate compounds, e.g. malathion, paraoxon, fenitrothion, monochrotophos and dichlorovos. The proposed sensor shows the detection limit of 0.1ng/mL and it is applicable for analysis of parathion in a rice sample. The sensor's performance is validated by comparting the obtained results with gas chromatographic data.

The Sensitized Solid‐Phase Electrochemiluminescence of Electrodeposited Poly‐Luminol/Aniline on AuAg/TiO2 Nanohybrid Functionalized Electrode for Flow Injection Analysis

AbstractIn this study, a copolymer of luminol with aniline is electrochemically deposited onto the AuAg/TiO2 nanohybrid functionalized indium tin oxide coated glass. It is used as a reagentless electrochemiluminescent (ECL) electrode for flow‐injection‐analysis (FIA). The properties of this solid phase ECL electrode are characterized by cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy etc. It has stronger ECL emission, sensitive response for target analytes and excellent stability. The so‐prepared ECL electrode shows sensitive response to reactive oxygen species thereafter to be applied for determination of hydrogen peroxide with FIA mode. Under optimized conditions, a mass detection limit of 0.822 pg of hydrogen peroxide was obtained. Thus the hydrogen peroxide residues in samples were detected with satisfactory result.

Development of a nanocomposite system and its application in biosensors construction

Abstract The present work describes the development of a nanocomposite system and its application in construction of a new amperometric biosensor applied in the determination of total polyphenolic content from propolis extracts. The nanocomposite system was based on covalent immobilization of laccase on functionalized indium tin oxide nanoparticles and it was morphologically and structural characterized. The casting of the developed nanocomposite system on the surface of a screen-printed electrode was used for biosensor fabrication. The analytical performance characteristics of the settled biosensor were determined for rosmarinic acid, caffeic acid and catechol (as laccase specific substrate). The linearity was obtained in the range of 1.06×10−6 − 1.50×10−5 mol L−1 for rosmarinic acid, 1.90×10−7 − 2.80×10−6 mol L−1 for caffeic acid and 1.66×10−6 − 7.00×10−6 mol L−1 for catechol. A good sensitivity of amperometric biosensor 141.15 nA µmol−1 L−1 and fair detection limit 7.08×10−8 mol L−1 were obtained for caffeic acid. The results obtained for polyphenolic content of propolis extracts were compared with the chromatographic data obtained by liquid-chromatography with diode array detection.

Interplay of cleaning and de-doping in oxygen plasma treated high work function indium tin oxide (ITO)

Indium tin oxide (ITO) is extensively used as a transparent electrode in photovoltaic cells and organic light emitting diodes. High surface work function (WF) of ITO is a crucial parameter for enhanced device performance. The ITO WF is usually around 4.3eV without any surface treatment. With surface treatments ITO WF, as high as 5.4eV has been reported. We designed a surface treatment method with which we achieved substantially high ITO surface work function of over 6.1eV. We observed changes in valence electronic structure and core levels, apart from surface cleaning. We also investigated interface formation of copper phthalocyanine (CuPc) on the high WF ITO. In the proximity of the interface the highest occupied energy level of CuPc was observed to be almost pinned to the Fermi level. We fabricated three simple devices with no to high treatment. The device results were observed to be consistent with the findings of electronic energy level alignment.

A simple two-step method to fabricate highly transparent ITO/polymer nanocomposite films

Transparent functional indium tin oxide (ITO)/polymer nanocomposite films were fabricated via a simple approach with two steps. Firstly, the functional monodisperse ITO nanoparticles were synthesized via a facile nonaqueous solvothermal method using bifunctional chemical agent (N-methyl-pyrrolidone, NMP) as the reaction solvent and surface modifier. Secondly, the ITO/acrylics polyurethane (PUA) nanocomposite films were fabricated by a simple sol-solution mixing method without any further surface modification step as often employed traditionally. Flower-like ITO nanoclusters with about 45nm in diameter were mono-dispersed in ethyl acetate and each nanocluster was assembled by nearly spherical nanoparticles with primary size of 7–9nm in diameter. The ITO nanoclusters exhibited an excellent dispersibility in polymer matrix of PUA, remaining their original size without any further agglomeration. When the loading content of ITO nanoclusters reached to 5wt%, the transparent functional nanocomposite film featured a high transparency more than 85% in the visible light region (at 550nm), meanwhile cutting off near-infrared radiation about 50% at 1500nm and blocking UV ray about 45% at 350nm. It could be potential for transparent functional coating materials applications.

Layer-by-layer assembly sensitive electrochemical sensor for selectively probing l-histidine based on molecular imprinting sol–gel at functionalized indium tin oxide electrode

A novel sensitive and selective imprinted electrochemical sensor was successfully constructed for the direct detection of l -histidine by combination of a molecular imprinting film and multi-walled carbon nanotubes (MWNTs). The sensor was fabricated onto an indium tin oxide (ITO) electrode via stepwise modification of MWNTs and a thin film of molecularly imprinted polymers (MIPs) via sol–gel technology. The introduced MWNTs exhibited noticeable enhancement on the sensitivity of the MIPs sensor. Meanwhile, the molecularly imprinted film displayed high sensitivity and excellent selectivity for the target molecule l -histidine. The proposed imprinted sensor was characterized by using scanning electron microscope (SEM) and electrochemical methods involving cyclic voltammetry (CV), differential pulse voltammetry (DPV) and amperometric i–t curve. A linear ranging from 2.0 μmol L −1 to 1.0 mmol L −1 for the detection of l -histidine was observed with the detection limit of 5.8 × 10 −9 mol L −1 for S/N = 3. This imprinted electrochemical sensor was successfully employed to detect l -histidine in human blood serum.

Electrochemical Sensor for trans‐Resveratrol Determination Based on Indium Tin Oxide Electrode Modified with Molecularly Imprinted Self‐Assembled Films

AbstractA voltammetric sensor for sensitive and specific determination of trans‐resveratrol (RES) were prepared based on immobilization of an RES‐imprinted film on the surface of functionalized Indium Tin Oxide (ITO) electrode, which was modified with γ‐methacyloxypropyl trimethoxysilane (γ‐MPS). Cyclic Voltammetry (CV) was presented to extract RES from the molecularly imprinted polymer film and RES were extracted rapidly and completely. The binding performance of the imprinted electrode with the template RES were investigated using differential pulse voltammetry (DPV). The results showed that the imprinted ITO film can give selective recognition to the template RES over that of structurally analogous molecules. A linear response to RES in the concentration range of 2.0×10−6 M to 2.0×10−5 M was observed with a correlation coefficient of 0.992, and the detection limit of the electrochemical sensor was 8.0×10−7 M. Whereas, binding to the reference nonimprinted electrode, made in the same way but without the addition of template RES, there was almost no response to RES.

Sensitive Biomimetic Sensor Based on Molecular Imprinting at Functionalized Indium Tin Oxide Electrodes

AbstractWe initially report an electrochemical sensing platform based on molecularly imprinted polymers (MIPs) at functionalized Indium Tin Oxide Electrodes (ITO). In this research, aminopropyl‐derivatized organosilane aminopropyltriethoxysilane (APTES), which plays the role of functional monomers for template recognition, was firstly self‐assembled on an ITO electrode and then dopamine‐imprinted sol was spin‐coated on the modified surface. APTES which can interact with template dopamine (DA) through hydrogen bonds brought more binding sites located closely to the surface of the ITO electrode, thus made the prepared sensor more sensitive for DA detection. Potential scanning is presented to extract DA from the modified film, thus DA can rapidly and completely leach out. The affinity and selectivity of the resulting biomimetic sensor were characterized using cyclic voltammetry (CV). It exhibited an increased affinity for DA over that of structurally related molecules, the anodic current for DA oxidation depended on the concentration of DA in the linear range from 2×10−6 M to 0.8×10−3 M with a correlation coefficient of 0.9927. In contrast, DA‐templated film prepared under identical conditions on a bare ITO showed obviously lower response toward dopamine in solution. It should be noted that potential scanning is a very effective approach for DA extraction, and surface modification of the electrochemical transducer with functional monomers is responsible for the development of MIPs‐based highly sensitive biomimetic sensor.

Silver nanoparticles coated with adenine: preparation, self-assembly and application insurface-enhanced Raman scattering

We describe herein the preparation of silver nanoparticles (AgNPs) usingnucleobase adenine as protecting agent through the in situ chemical reduction ofAgNO3 with NaBH4 in an aqueous medium at room temperature. As-prepared AgNPs were characterized byUV–visible spectra, transmission electron microscopy and x-ray photoelectronspectroscopy. All these data confirmed the formation of AgNPs. On thebasis of electrostatic interactions between as-prepared AgNPs and anionicpolyelectrolyte poly(sodium 4-styrenesulfonate) (PSS), we successfully fabricated(PSS/AgNP)n (n = 0–9) multilayers on a 3-mercaptopropyltrimethoxysilane/AgNP functionalizedindium tin oxide (ITO) substrate via the layer-by-layer self-assembly techniqueand characterized as-formed multilayers with UV–visible spectra. Furthermore,these ITO substrates coated with multilayers of different thickness wereinvestigated as surface-enhanced Raman scattering (SERS)-active substrates usingp-aminothiophenol as a probe molecule, implying that these multilayers substrates may bepromising for a new type of SERS-active substrate.