Highly selective non-enzymatic electrochemical sensor based on a titanium dioxide nanowire-poly(3-aminophenyl boronic acid)-gold nanoparticle ternary nanocomposite.

A novel three component (titanium dioxide nanowire (TiO2 NW), poly(3-aminophenyl boronic acid) (PAPBA) and gold nanoparticles (Au NPs)) based ternary nanocomposite (TNC) (designated as TiO2 NW/PAPBA-Au TNC) was prepared by a simple two-stage synthetic approach and utilized for the fabrication of a non-enzymatic (enzyme-free) glucose (NEG) sensor. In stage 2, the PAPBA-Au NC was formed by oxidative polymerization of 3-APBA using HAuCl4 as oxidant on the surface of pre-synthesized TiO2 NW via electrospinning (stage 1). The formation of PAPBA-Au NC as the shell on the surface of the TiO2 NW (core) was confirmed by field emission scanning electron microscopy (FE-SEM). Notably, we obtained a good peak to peak separation, and a high peak current for the redox Fe(CN)6 3-/4- process indicating excellent electron transfer capability at the glassy carbon electrode (GCE)/TiO2 NW/PAPBA-Au TNC interface. Also, the fabricated TiO2 NW/PAPBA-Au TNC provides excellent electrocatalytic activity towards glucose detection in neutral (pH = 7.0) phosphate buffer solution. The detection of glucose was monitored using differential pulse voltammetry. The obtained sensitivity and detection limits are superior to many of the TiO2 based enzymatic and non-enzymatic glucose sensors reported in the literature. Furthermore, the TiO2 NW/PAPBA-Au TNC sensor is preferred because of its high selectivity to glucose in the presence of co-existing interfering substances and practical application for monitoring glucose in human blood serum samples.

Enhanced photoelectrochemical biosensing performances for graphene (2D) - Titanium dioxide nanowire (1D) heterojunction polymer conductive nanosponges.

In this work, an efficient photoelectrochemical (PEC) biosensing platform has been designed and developed based on graphene (G) through modifying it into an electroconductive polymer nanosponge (EPNS) and with the incorporation of titanium dioxide nanowires (TiO2 NW) (designated as TiO2 (G) NW@EPNS). Functioning as an efficient immobilization matrix for immobilization of the enzyme Cytochrome C (Cyt C), TiO2 (G) NW@EPNS delivers features for an efficient PEC biosensor, such as fast kinetics of direct electron transfer (DET) to the electrode and effective separation of photogenerated holes and electrons. TiO2 (G) NW@EPNS exhibited DET to the electrode with a highly heterogeneous electron transfer rate constant of 6.29±0.002s-1. The existence of TiO2, G and EPNS in conjunction facilitates DET between the electrode surface and the protein. The fabricated PEC nitrite ion (NO2-) biosensor showed superior analytical performances such as wide linear range (0.5-9000µM), lowest detection limit (0.225mM) and excellent specificity for NO2- in the presence other interferences at a very low bias potential (-0.11V). This study opens up the feasibility of fabricating a PEC biosensor for any analyte using a matrix comprising of G and a photoactive material and EPNS, because these components synergistically contribute to effective immobilization of on enzyme, DET to the electrode and simple read-out under the light.

A novel bismuth oxychloride-graphene hybrid nanosheets based non-enzymatic photoelectrochemical glucose sensing platform for high performances.

A novel non-enzymatic photoelectrochemical (PEC) glucose sensor was first constructed based on the unique two-dimensional (2D) bismuth oxychloride-graphene nanohybrid sheets (BiOCl-G NHS). We have utilized a facile hydrothermal approach for the preparation of BiOCl-G NHS. Results from cyclic voltammetric and differential pulse voltammetric measurements revealed that the BiOCl-G NHS electrode is capable of generating photocurrent for glucose when its surface is irradiated with a light source (wavelength=365nm). The photocurrents produced for the presence of glucose at the bias potential of +0.50V showed a linear dependence on glucose concentration in the range between 0.5 and 10mM and had a detection limit of 0.22mM. The PEC detection of glucose at BiOCl-G NHS was not influenced by the presence of other common interfering species. The glucose levels, as determined by the BiOCl-G NHS sensor, agreed well with those obtained by the commercial glucometers. This novel non-enzymatic PEC glucose sensor exhibited good performances, such as a wider concentration range (500µM-10mM), high sensitivity (1.878µMmM-1cm-2 (500µM-2mM) and 127.2µMmM-1cm-2 (2mM-10mM)), good selectivity, reproducibility (RSD=2.4%) and applicability to real sample (human serum).

A novel multicomponent redox polymer nanobead based high performance non-enzymatic glucose sensor.

The fabrication of a highly sensitive electrochemical non-enzymatic glucose sensor based on copper nanoparticles (Cu NPs) dispersed in a graphene (G)-ferrocene (Fc) redox polymer multicomponent nanobead (MCNB) is reported. The preparation of MCNB involves three major steps, namely: i) the preparation of a poly(aniline-co-anthranilic acid)-grafted graphene (G-PANI(COOH), ii) the covalent linking of ferrocene to G-PANI(COOH) via a polyethylene imine (PEI), and iii) the electrodeposition of Cu NPs. The prepared MCNB (designated as G-PANI(COOH)-PEI-Fc/Cu-MCNB), contains a conductive G-PANI(COOH), electron mediating Fc, and electrocatalytic Cu NPs that make it suitable for ultrasensitive non-enzymatic electrochemical sensing. The morphology, structure, and electro activities of MCNB were characterized. Electrochemical measurements showed that the G-PANI(COOH)-PEI-Fc/Cu-MCNB/GCE modified electrode exhibited good electrocatalytic behavior towards the detection of glucose in a wide linear range (0.50 to 15mM), with a low detection limit (0.16mM) and high sensitivity (14.3µAmM(-1)cm(-2)). Besides, the G-PANI(COOH)-PEI-Fc/Cu-MCNB/GCE sensor electrode did not respond to the presence of electroactive interferrants (such as uric acid, ascorbic acid, and dopamine) and saccharides or carbohydrates (fructose, lactose, d-isoascorbic acid, and dextrin), demonstrating its selectivity towards glucose. The fabricated NEG sensor exhibited high precision for measuring glucose in serum samples, with an average RSD of 4.3% and results comparable to those of commercial glucose test strips. This reliability and stability of glucose sensing indicates that G-PANI(COOH)-PEI-Fc/Cu-MCNB/GCE would be a promising material for the non-enzymatic detection of glucose in physiological fluids.

Fabrication of a novel dual mode cholesterol biosensor using titanium dioxide nanowire bridged 3D graphene nanostacks.

Herein, we fabricated a novel electrochemical-photoelectrochemical (PEC) dual-mode cholesterol biosensor based on graphene (G) sheets interconnected-graphene embedded titanium nanowires (TiO2(G)-NWs) 3D nanostacks (designated as G/Ti(G) 3DNS) by exploiting the beneficial characteristics of G and TiO2-NWs to achieve good selectivity and high sensitivity for cholesterol detection. The G/Ti(G) 3DNS was fabricated by the reaction between functionalized G and TiO2(G)-NWs. Cholesterol oxidase (ChOx) was subsequently immobilized in to G/Ti(G) 3DNS using chitosan (CS) as the binder and the dual mode G/Ti(G) 3DNS/CS/ChOx biosensor was fabricated. The electro-optical properties of the G/Ti(G) 3DNS/CS/ChOx bioelectrode were characterized by cyclic voltammetry and UV-vis diffuse reflection spectroscopy. The cyclic voltammetry of immobilized ChOx showed a pair of well-defined redox peaks indicating direct electron transfer (DET) of ChOx. The amperometric reduction peak current (at -0.05V) linearly increased with increase in cholesterol concentration. The G/Ti(G) 3DNS/CS/ChOx bioelectrode was selective to cholesterol with a remarkable sensitivity (3.82µA/cm(2)mM) and a lower detection limit (6µM). Also, G/Ti(G) 3DNS/CS/ChOx functioned as photoelectrode and exhibited selective detection of cholesterol under a low bias voltage and light irradiation. Kinetic parameters, reproducibility, repeatability, storage stability and effect of temperature and pH were evaluated. We envisage that G/Ti(G) 3DNS with its prospective characteristics, would be a promising material for wide range of biosensing applications.