Govindhan Maduraiveeran

Potential Sensing Platform of Silver Nanoparticles Embedded in Functionalized Silicate Shell for Nitroaromatic Compounds

A simple and new method to grow a pentagonally twinned structure of silver-silicate core-shell nanoparticles in aqueous environment at room temperature and its application in nitrobenzene (NB) sensing is described here. Silver-silicate core-shell nanoparticles were obtained by one-step synthesis using N-[3-(trimethoxysilyl)propyl]-ethylene diamine (EDAS) as a reducing/stabilizing agent and cetyltrimethylammonium bromide (CTAB) as the growing agent for the growth of silver nanoparticles (Ag(nps)). The silver-silicate core-shell nanoparticles were characterized by high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), scanning electron microscope (SEM), UV-visible absorption, emission, excitation, and electrochemical measurements. The electrochemical studies of silver-silicate core-shell nanoparticles modified electrode showed the silver nanoparticles oxidation potential and their corresponding reduction potential at 0.24 and -0.16 V, respectively. The optical and electrochemical applications silicate-shell stabilized silver nanoparticles were established toward nitrobenzene. The optical sensing of nitrobenzene by silver-silicate core-shell nanoparticles studied using absorption and emission spectral methods showed experimentally determined lowest detection limits (LOD) of 1 and 10 microM, respectively. Silver-silicate core-shell nanoparticles showed excellent electrocatalytic activity toward the reduction of nitrobenzene. The electrochemical sensor showed the lowest detection limit (LOD) of 2.5 nM toward nitrobenzene sensing.

Electrochemical sensor and biosensor platforms based on advanced nanomaterials for biological and biomedical applications

Introduction of novel functional nanomaterials and analytical technologies signify a foremost possibility for the advance of electrochemical sensor and biosensor platforms/devices for a broad series of applications including biological, biomedical, biotechnological, clinical and medical diagnostics, environmental and health monitoring, and food industries. The design of sensitive and selective electrochemical biological sensor platforms are accomplished conceivably by offering new surface modifications, microfabrication techniques, and diverse nanomaterials with unique properties for in vivo and in vitro medical analysis via relating a sensibly planned electrode/solution interface. The advantageous attributes such as low-cost, miniaturization, energy efficient, easy fabrication, online monitoring, and the simultaneous sensing capability are the driving force towards continued growth of electrochemical biosensing platforms, which have fascinated the interdisciplinary research arenas spanning chemistry, material science, biological science, and medical industries. The electrochemical biosensor platforms have potential applications in the early-stage detection and diagnosis of disease as stout and tunable diagnostic and therapeutic systems. The key aim of this review is to emphasize the newest development in the design of sensing and biosensing platforms based on functional nanomaterials for biological and biomedical applications. High sensitivity and selectivity, fast response, and excellent durability in biological media are all critical aspects which will also be wisely addressed. Potential applications of electrochemical sensor and biosensor platforms based on advanced functional nanomaterials for neuroscience diagnostics, clinical, point-of-care diagnostics and medical industries are also concisely presented.

Hierarchical oxygen-implanted MoS2 nanoparticle decorated graphene for the non-enzymatic electrochemical sensing of hydrogen peroxide in alkaline media

Owing to the extensive applications of hydrogen peroxide (H2O2) in biological, environmental and chemical engineering, it is of great importance to investigate sensitive and selective sensing platform towards the detection of H2O2. Herein, oxygen-implanted MoS2 nanoparticles decorated graphene nanocomposite is synthesized via a facile one-pot solvothermal method for the sensitive detection of H2O2 in alkaline media. The structure and morphology of the MoS2/graphene nanocomposites were systematically characterized, showing that Mo-O bonds are formed and oxygen is implanted into the crystal structure in the nanocomposite. As a result, the MoS2/graphene composite exhibited enhanced electron transfer kinetics and excellent electro-reduction performance towards H2O2 in alkaline media. Under optimum conditions, the fabricated sensor demonstrated a wide linear response towards H2O2 in the range of 0.25-16mM with a low detection limit of 0.12μM and high sensitivity of 269.7μAmM-1cm-2. Besides, the constructed sensor presented a good selectivity to H2O2 with the presence of other interfering species. Therefore, the proposed sensor was successfully applied for the detection and determination of H2O2 in real sample, indicating great potential for the practical applications.

Enhanced sensing of mercuric ions based on dinucleotide-functionalized silver nanoparticles

A very simple one-pot synthesis of nicotinamide adenine dinucleotide (NAD)-functionalized silver nanoparticles in an aqueous solution at room temperature without hazardous reducing agents wherein NADH is employed as the functional molecule for highly selective optical sensing of mercuric ions (Hg2+) in an aqueous solution based on an absorption and emission method, with a detection limit of 0.02 nM. NADH was used as the reducing and stabilizing agent for the formation and stabilization of silver nanoparticles, and cetyltrimethylammonium bromide (CTAB) was used as the growth agent for the silver nanoparticles. The NADH-stabilized silver nanoparticles were used as an optical sensor for the detection of mercuric ions. The potential sensing ability of these synthesized silver nanoparticles is utilized to design an absorption and emission-based sensor platform for mercuric ions with high sensitivity and selectivity in the presence of other interfering metal cations, including Pb2+, Cd2+, Ce2+, Cu2+, Ni2+, Li+, Na+, K+ and Ca2+. The facile biomolecule-assisted synthesis of anisotropically structured silver nanoparticles and the direct detection of mercuric ions at the nano-molar concentration level in the presence of other interfering metal ions in water are the main advantages of the present system. The ultrasensitive nature of the sensing platform is ascribed to the NAD-functionalized anisotropic silver nanostructures. The present optical sensor is very simple to prepare, cost effective, and time saving; no external assemblies are attached on the surface of the silver nanoparticles. This method does not require the use of organic co-solvents, enzymatic reactions, light-sensitive dye molecules, lengthy protocols, surface modification of nanoparticles, or sophisticated instrumentation, thereby overcoming most of the limitations of conventional methods.

Electrical conductivity measurements of bacterial nanowires from Pseudomonas aeruginosa

The extracellular appendages of bacteria (flagella) that transfer electrons to electrodes are called bacterial nanowires. This study focuses on the isolation and separation of nanowires that are attached via Pseudomonas aeruginosa bacterial culture. The size and roughness of separated nanowires were measured using transmission electron microscopy (TEM) and atomic force microscopy (AFM), respectively. The obtained bacterial nanowires indicated a clear image of bacterial nanowires measuring 16 nm in diameter. The formation of bacterial nanowires was confirmed by microscopic studies (AFM and TEM) and the conductivity nature of bacterial nanowire was investigated by electrochemical techniques. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), which are nondestructive voltammetry techniques, suggest that bacterial nanowires could be the source of electrons—which may be used in various applications, for example, microbial fuel cells, biosensors, organic solar cells, and bioelectronic devices. Routine analysis of electron transfer between bacterial nanowires and the electrode was performed, providing insight into the extracellular electron transfer (EET) to the electrode. CV revealed the catalytic electron transferability of bacterial nanowires and electrodes and showed excellent redox activities. CV and EIS studies showed that bacterial nanowires can charge the surface by producing and storing sufficient electrons, behave as a capacitor, and have features consistent with EET. Finally, electrochemical studies confirmed the development of bacterial nanowires with EET. This study suggests that bacterial nanowires can be used to fabricate biomolecular sensors and nanoelectronic devices.

Silver nanoparticles embedded three dimensional silicate sol–gel matrix modified electrode for nitrite sensor application

A simple amperometric sensor was fabricated by using silver nanoparticles (Agnps) embedded three dimensional silicate sol–gel (SG) matrix (SG–Agnps). The silver nanoparticles stabilised by SH functionalised 3–D silicate sol–gel network was coated on the glassy carbon electrode and used for the determination of nitrite ion in 0.1 M PBS (pH 7.2). The prepared silver nanoparticles–silicate sol–gel (SG–Agnps) modified electrode was characterised by UV–visible absorption spectroscopy, scanning electron microscopy (SEM) and electrochemical method. The electrochemical behaviour of SG–Agnps modified electrode was studied by using potassium ferricyanide as a redox marker to probe the tunable kinetic barrier of the dispersed silver nanoparticles in silicate sol–gel matrix. The SG–Agnps film was used as nanomaterials comprised electrochemical device for direct electrocatalysis and amperometric sensing of nitrite ion. The silver nanoparticles embedded silicate sol–gel film showed good stability and sensitivity with an experimental amperometric detection limit of 4 M. The fabrication of SG–Agnps modified electrode was very simple and it showed fast amperometric response and reproducible results for nitrite sensing.

Nanomaterial-based environmental sensing platforms using state-of-the-art electroanalytical strategies

AbstractElectroanalytical techniques have been extensively employed in the advancement of sensor platforms based on nanomaterials owing to their rapid response, high sensitivity, and selectivity. It is of immense significance for the swift and sensitive detection of environmental pollutants or contaminants such as a major group of unregulated chemicals such as heavy metals, inorganic anions, phenolic compounds, pesticides, and chemical warfare reagents, which may cumulatively resource severe harm to human health and environmental. These environmental pollutants are regularly obtained from a large group of unmaintained compounds/complexes, containing industry, human, and animal fecal waste; natural toxins; drinking water disinfection by-products; personal care products; pharmaceuticals; food materials through food preparation and packaging processes, etc. The present minireview will display various concepts and advancements of electroanalytical techniques and their potential applications in environmental sensing. The introduction of novel electroanalytical tools and nanostructured electrode surfaces may demonstrate even higher sensitive and selective sensor platforms. Electroanalytical methods possess passionate importance in the analytical research community, and they serve as ideal tactics, which display several features such as rapid response, robustness, high selectivity and sensitivity, cost-effective miniaturization, and the perspective for online monitoring towards environmental, food, and biomedical applications. The advancement and prospects for the applications of electroanalytical techniques using nanomaterials in the design of environmental sensor platforms will also be discussed. Graphical abstractThis review presents the concepts and insights of various electroanalytical techniques and their potential applications in the design of electrochemical sensor and biosensor platforms.