Two-dimensional ytterbium oxide nanodisks based biosensor for selective detection of urea.

Herein, we demonstrate synthesis and application of two-dimensional (2D) rectangular ytterbium oxide (Yb2O3) nanodisks via a facile hydrothermal method. The structural, morphological, compositional, crystallinity, and phase properties of as-synthesized nanodisks were carried out using several analytical techniques that showed well defined 2D rectangular nanodisks/sheet like morphologies. The average thickness and edge length of the nanosheet structures were 20 ± 5nm and 600 ± 50nm, respectively. To develop urea biosensor, glassy carbon electrodes (GCE) were modified with Yb2O3 nanodisks, followed by urease immobilization and Nafion membrane covering (GCE/Yb2O3/Urease/Nafion). The fabricated biosensor showed sensitivity of 124.84µAmM-1cm-2, wide linear range of 0.05-19mM, detection limit down to ~ 2µM, and fast response time of ~ 3s. The developed biosensor was also used for the urea detection in water samples through spike-recovery experiments, which illustrates satisfactory recoveries. In addition, the obtained desirable selectivity towards specific interfering species, long-term stability, reproducibility, and repeatability further confirm the potency of as-fabricated urea biosensor.

Mechanically exfoliated MoS2 sheet coupled with conductive polyaniline as a superior supercapacitor electrode material.

The development of electrically conductive metal sulfide-based polymer nanocomposites for energy storage materials has been a major focus by researchers to solve the energy crisis. In this study, a simple and facile method was used to construct a nanocomposite by combining a mechanically exfoliated MoS2 (M-MoS2) sheet with polyaniline (Pani) using a simple and scalable in-situ chemical oxidative polymerization method. The as-prepared nanocomposite (M-MoS2-Pani nanocomposite) was characterized further by usual basic spectroscopic techniques, such as X-ray powder diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and Brunauer-Emmett-Teller surface area analysis. The electrochemical supercapacitive characteristics of the M-MoS2-Pani nanocomposite was tested in a three-electrode assembly by obtaining cyclic voltammetric (CV) curves and galvanostatic charge-discharge (GCD) measurements. The results were compared with those of a C-MoS2-Pani nanocomposite that had been synthesized using bulk MoS2. The M-MoS2-Pani nanocomposite synthesized using exfoliated MoS2 exhibited a higher specific capacitance of 510.12Fg-1 at a current of 1Ag-1 than the C-MoS2-Pani nanocomposite (225.15Fg-1), which was synthesized using bulk C-MoS2 delivered. The enhanced electrochemical supercapacitive performance was correlated to the synergistic effect and chemical interactions between the Pani and MoS2, which provide high electrical conductivity and a sufficient empty state for electrode/electrolyte contact.

Application of pristine and doped SnO2 nanoparticles as a matrix for agro-hazardous material (organophosphate) detection.

With an increasing focus on applied research, series of single/composite materials are being investigated for device development to detect several hazardous, dangerous, and toxic molecules. Here, we report a preliminary attempt of an electrochemical sensor fabricated using pristine Ni and Cr-doped nano tin oxide material (SnO2) as a tool to detect agro-hazardous material, i.e. Organophosphate (OP, chlorpyrifos). The nanomaterial was synthesized using the solution method. Nickel and chromium were used as dopant during synthesis. The synthesized material was calcined at 1000 °C and characterized for morphological, structural, and elemental analysis that showed the formation of agglomerated nanosized particles of crystalline nature. Screen-printed films of powder obtained were used as a matrix for working electrodes in a cyclic voltammogram (CV) at various concentrations of organophosphates (0.01 to 100 ppm). The CV curves were obtained before and after the immobilization of acetylcholinesterase (AChE) on the nanomaterial matrix. An interference study was also conducted with hydroquinone to ascertain the selectivity. The preliminary study indicated that such material can be used as suitable matrix for a device that can easily detect OP to a level of 10 ppb and thus contributes to progress in terms of desired device technology for the food and agricultural-industries.

Sol­Gel Synthesis of Manganese Doped Titanium Oxide Nanoparticles for Electrochemical Sensing of Hydroquinone.

Here we report development of a hydroquinone (HQ) electrochemical sensor using nanosized manganese doped titanium oxide as a composite material. The nanomaterial was synthesized with sol gel method using calculated amount of Mn and Ti atoms resulting into a composite metal oxide. Morphological observations indicated a uniform particle size and shape distribution with almost spherical shape and size of about 20­30 nm. While structural analysis indicated formation of mixed phase of TiO2 and MnO forming MnTiO3. The synthesized nanomaterial was used as a matrix for fabrication of hydroquinone electrochemical sensor and tested over a wide range from 2 mM to 10 mM. The developed electrochemical sensor exhibited sensitivity of 2.96 µA mM⁻¹ (23.55 µA mM⁻¹ cm⁻²) with a detection limit of 7.5 µM, which is rarely reported for such composite nanomaterial.

Tailoring the Optoelectronic Properties of Nano-Metal Oxides Using Anthocyanins and Lanthanide.

Here we report a simple and effective method in tailoring the optoelectronic properties of semi-conducting metal oxide for suitable device application. Sol-gel synthesis was used to synthesize manganese doped TiO2 nanopowder and commercially available TiO2 nanopowder was used as reference material. Thick films of these powder were screen printed on FTO coated glass and annealed at 450 degrees C in ambient air. Separately, 60 µL of neodymium chloride prepared from neodymium oxide, 60 µL of ruthenium based commercial dye (N719) and 60 µL of extracts of calendula orange and dog flower were used as sensitizer to improve the photoconductance properties. Elemental analysis confirmed synthesis of composite material of Mn and TiO2. Morphological observation showed a uniform particles of 25 to 50 nm diameter. Optoelectronic properties were studied by using thick films of these powders as working electrode as a function of wavelength from 430 to 750 nm and the cyclic voltammogram were obtained by scanning potential from -1.5 V to +1.5 V at the illumination intensity of 1000 Wm(-2). Sensitization resulted in additional absorption and functional bands. Oxidation peak current was found decreasing with increasing wavelength. Sensitization with flower extract resulted in increased oxidation current at higher wavelength indicating the improved photoconduction in comparison with N719 and neodymium.

Relief of Oxidative Stress Using Curcumin and Glutathione Functionalized ZnO Nanoparticles in HEK-293 Cell Line.

To elucidate the effect of zinc oxide nanoparticles (ZnO-NPs) with different surface modifications in relieving the oxidative stress in cultured human embryonic kidney cells (HEK-293) following investigation was performed. Oxidative stress was artificially induced by hydrogen peroxide in HEK-293 cell culture and its management was studied. Alkyl amines modified ZnO-NPs with curcumin and reduced glutathione (GSH) functionalization was used in managing oxidative stress and had shown promising results. ZnO-NPs used in this study were synthesized via non-aqueous sol-gel method and FESEM characterisation showed them of spherical shape of about 20-50 nm size with amine, curcumin and GSH functionalization. UV-visible and FTIR spectroscopic characterizations confirmed functionalization of ZnO-NPs. Decrease in oxidative stress was found with the dose-dependent culture of HEK-293 cells with these functionalized ZnO-NPs. Cell viability and morphology, as observed using AFM and inverted microscope, was retained with the prescribed dosages of the functionalized nanoparticles while at higher dosages they caused cytotoxicity and death. Diethylamine (DEA) modified ZnO-NPs and their functionalization with GSH and curcumin were found more effective in managing oxidative stress in cells. Present study could help in designing economical and bio-compatible functionalized non-toxic nanoparticles designed for managing oxidative stress leading to possible therapeutical and medicinal uses.

A Label-Free Photoluminescence Genosensor Using Nanostructured Magnesium Oxide for Cholera Detection.

Nanomaterial-based photoluminescence (PL) diagnostic devices offer fast and highly sensitive detection of pesticides, DNA, and toxic agents. Here we report a label-free PL genosensor for sensitive detection of Vibrio cholerae that is based on a DNA hybridization strategy utilizing nanostructured magnesium oxide (nMgO; size >30 nm) particles. The morphology and size of the synthesized nMgO were determined by transmission electron microscopic (TEM) studies. The probe DNA (pDNA) was conjugated with nMgO and characterized by X-ray photoelectron and Fourier transform infrared spectroscopic techniques. The target complementary genomic DNA (cDNA) isolated from clinical samples of V. cholerae was subjected to DNA hybridization studies using the pDNA-nMgO complex and detection of the cDNA was accomplished by measuring changes in PL intensity. The PL peak intensity measured at 700 nm (red emission) increases with the increase in cDNA concentration. A linear range of response in the developed PL genosensor was observed from 100 to 500 ng/µL with a sensitivity of 1.306 emi/ng, detection limit of 3.133 ng/µL and a regression coefficient (R(2)) of 0.987. These results show that this ultrasensitive PL genosensor has the potential for applications in the clinical diagnosis of cholera.

Fabrication and characterization of a highly sensitive hydroquinone chemical sensor based on iron-doped ZnO nanorods.

Herein, we report the development of a simple and highly sensitive hydroquinone (HQ) chemical sensor based on an electrochemically activated iron-doped (Fe-doped) zinc oxide nanorod (ZnO NR) modified screen-printed electrode (SPE). The Fe-doped ZnO NRs were prepared using a hydrothermal process and their morphological, crystal, compositional and optical properties were characterized in detail. The detailed characterizations showed that the NRs are densely grown, well-crystalline and possess a wurtzite hexagonal phase. The fabricated HQ electrochemical sensor exhibited high sensitivity of 18.60 µA mM(-1) cm(-2) and a very low experimental detection limit of 0.51 µM. Our results demonstrate that simply prepared doped ZnO nanomaterials are promising candidates to fabricate highly sensitive electrochemical sensors.

Electrochemical enzyme-less urea sensor based on nano-tin oxide synthesized by hydrothermal technique.

Nano-Tin oxide was synthesized using hydrothermal method at 150 °C for 6 h and then thin films were deposited by electrophoretic method at an optimized voltage of 100 V for 5 min on electropolished aluminum substrate. Spherical particles of about 30-50 nm diameters are observed with partial agglomeration when observed under electron microscope, which are tetragonal rutile structure. XPS results showed peaks related to Sn 4d, Sn 3d, O 1s & C 1s with spin-orbit splitting of 8.4 eV for Sn 3d. Feasibility studies of enzyme less urea sensing characteristics of nano-tin oxide thin films are exhibited herein. The deposited films have been used for enzyme less urea sensing from 1 to 20 mM concentration in buffer solution. The sensors were characterized electrochemically to obtain cyclic voltammogram as a function of urea concentration and scan rate. The sensitivity is estimated as 18.9 µA/mM below 5 mM and 2.31 µA/mM above 5 mM with a limit of detection of 0.6 mM.

Thermal, creep-recovery and viscoelastic behavior of high density polyethylene/hydroxyapatite nano particles for bone substitutes: effects of gamma radiation.

BACKGROUND: High Density Polyethylene (HDPE) is one of the most often used polymers in biomedical applications. The limitations of HDPE are its visco-elastic behavior, low modulus and poor bioactivity. To improve HDPE properties, HA nanoparticles can be added to form polymer composite that can be used as alternatives to metals for bone substitutes and orthopaedic implant applications. METHOD: In our previous work (BioMedical Engineering OnLine 2013), different ratios of HDPE/HA nanocomposites were prepared using melt blending in a co-rotating intermeshing twin screw extruder. The accelerated aging effects on the tensile properties and torsional viscoelastic behavior (storage modulus (G') and Loss modulus (G")) at 80°C of irradiated and non-irradiated HDPE/HA was investigated. Also the thermal behavior of HDPE/HA were studied. In this study, the effects of gamma irradiation on the tensile viscoelastic behavior (storage modulus (E') and Loss modulus (E")) at 25°C examined for HDPE/HA nanocomposites at different frequencies using Dynamic Mechanical Analysis (DMA). The DMA was also used to analyze creep-recovery and relaxation properties of the nanocomposites. To analyze the thermal behavior of the HDPE/HA nanocomposite, Differential Scanning Calorimetry (DSC) was used. RESULTS: The microscopic examination of the cryogenically fractured surface revealed a reasonable distribution of HA nanoparticles in the HDPE matrix. The DMA showed that the tensile storage and loss modulus increases with increasing the HA nanoparticles ratio and the test frequency. The creep-recovery behavior improves with increasing the HA nanoparticle content. Finally, the results indicated that the crystallinity, viscoelastic, creep recovery and relaxation behavior of HDPE nanocomposite improved due to gamma irradiation. CONCLUSION: Based on the experimental results, it is found that prepared HDPE nanocomposite properties improved due to the addition of HA nanoparticles and irradiation. So, the prepared HDPE/HA nanocomposite appears to have fairly good comprehensive properties that make it a good candidate as bone substitute.

Glucose sensor based on copper oxide nanostructures.

CuO spheres composed of finely arranged nanobricks were synthesized by simple and facile hydrothermal process and used as efficient electron mediators for the fabrication of highly sensitive non-enzymatic glucose sensor. The CuO spheres were synthesized at low-temperature of -30 degrees C and characterized in terms of their morphological, compositional, and structural properties. The morphological investigations revealed that the synthesized CuO powder possess spherical shapes and made of several CuO nanobricks. The detailed structural characterizations exhibited that the synthesized CuO spheres are nanocrystalline and possessing monoclinic structure. The fabricated glucose sensor based on CuO spheres exhibits a high sensitivity of -164.2523 microA mM(-1) cm(-2) and experimental detection limit of -39 microM with a quick response time of -10.0 s. The presented work shows that the easily prepared CuO nanomaterials can be used as efficient electron mediators for the fabrication of high sensitive non-enzymatic glucose sensors.

Magnesium oxide grafted carbon nanotubes based impedimetric genosensor for biomedical application.

Nanostructured magnesium oxide (size<10nm) grafted carboxyl (COOH) functionalized multi-walled carbon nanotubes (nMgO-cMWCNTs) deposited electrophoretically onto indium tin oxide (ITO) coated glass electrode and have been utilized for Vibrio cholerae detection. Aminated 23 bases single stranded DNA (NH2-ssDNA) probe sequence (O1 gene) of V. cholerae has been covalently functionalized onto nMgO-cMWCNTs/ITO electrode surface using EDC-NHS chemistry. This DNA functionalized MgO grafted cMWCNTs electrode has been characterized using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical techniques. The results of XPS studies reveal that sufficient O-C=O groups present at the nMgO-cMWCNTs surface are utilized for DNA binding. The results of hybridization studies conducted with fragmented target DNA (ftDNA) of V. cholerae using electrochemical impedance spectroscopy (EIS) reveal sensitivity as 3.87 Ω ng(-1) cm(-2), detection limit of ~21.70 ng µL(-1) in the linear range of 100-500 ng µL(-1) and stability of about 120 days. The proposed DNA functionalized nMgO-cMWCNTs nanomatrix provides a novel impedimetric platform for the fabrication of a compact genosensor device for biomedical application.

Tin oxide quantum dot based DNA sensor for pathogen detection.

We report the application of nano crystalline tin oxide quantum dots (SnO2-QDs) for electrochemical detection of Vibrio cholerae based on DNA hybridization technique. SnO2-QDs (- 1-5 nm) have been synthesized by laser ablation technique in liquid (LAL) and electrophoretically deposited onto hydrolyzed surface of indium tin oxide (ITO) coated glass electrode. A single stranded oligonucleotide probe (23 bases) have been designed form the virulent gene sequence of V. cholerae and has been immobilized onto SnO2-QDs/ITO surface for the fabrication of ssDNA/SnO2-QDs/ITO bioelectrode and these bioelectrode have been further used for DNA hybridization (dsDNA/SnO2-QDs/ITO). The electrochemical response studies have been carried out with different concentration genomic DNA (100-500 ng/microL), which indicated that SnO2 provides an effective surface to bind with the phosphate group of DNA, thus resulting in an enhanced electron transport. The hybridized electrode exhibits linear response with regression coefficient (R) 0.974, high sensitivity 35.20 nA/ng/cm2, low detection limit (31.5 ng/microL), faster response time (3 s) and high stability of 0-120 days when stored under refrigerated conditions.

Biocompatible nanostructured magnesium oxide-chitosan platform for genosensing application.

A novel organic-inorganic platform comprising of chitosan (CH) modified nanostructured magnesium oxide (nanoMgO) has been electrophoretically deposited on the indium-tin-oxide (ITO) substrate. The single stranded probe DNA (ssDNA) sequence of Vibrio cholerae has been covalently functionalized onto CH-nanoMgO/ITO surface. The cytotoxicity assay of nanoMgO particles, examined using human intestinal cell line (INT 407), reveals no significant cytotoxicity at the given doses in the range of 50-350 µg/mL. The X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and various microscopic techniques have been employed for the structural and morphological analysis of the fabricated electrodes. The electrochemical response studies of ssDNA and fragmented genomic DNA hybridized electrode (dsGDNA/CH-nanoMgO/ITO) have been carried out using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The dsGDNA/CH-nanoMgO/ITO bioelectrode exhibits a linear response in the range 100-500 ng/µL with improved sensitivity of 36.72 nA/ng/cm(2), faster response time of 3s and high stability of 3-4 months under refrigerated condition. The lower detection limit of fabricated genosensor has been estimated as 35.20 ng/µL and it shows good reproducibility/repeatability.

Enhanced photocatalytic properties of nanoclustered P-doped TiO2 films deposited by advanced atmospheric plasma jet.

A facile preparation of P-doped TiO2 nanoclusters onto fluorine-doped tin oxide (FTO) glass by an advanced atmospheric plasma jet (AAP jet) is reported here. Titanium tetrachloride (TiCl4) and phosphorus trichloride (PCl3) were used as precursors. Radio frequencies were used to generate plasma at fix powder with Argon as carrier gas. Films were deposited at 500 degrees C for 10 minutes. For comparison, as-prepared, annealed and deposited at 500 degrees C samples were studied for chemical/physical properties by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Optical properties were studied by using UV-Vis spectroscopy which indicated a reduction in optical band with P-doping. The rhodamine B (Rh-B) degradation by P-doped TiO2 deposited at 500 degrees C showed enhanced degradation efficiency than that of annealed TiO2. The suggested deposition method appears to be suitable for the synthesis of photocatalyst with proper control over dopants.

Photoconducting properties of a unit nanostructure of ZnO assembled between microelectrodes.

The photoconducting properties of a unit microflower of zinc oxide are investigated as a function of wavelength from UV to IR region at constant illumination intensity. Synthesized flowers were trapped in 2 microm gap, between pre-prepared gold microelectrodes, using AC dielectrophoresis. Photocurrent drastically increases upon illumination in the UV region, whereas it gradually reduces when irradiated in visible and IR region. Higher photoconductivity in UV region is correlated to band to band transition upon illumination. In visible region, deep level transitions are expected which intern exhibits comparatively low photocurrent. Photoconduction in IR region is only due to the adsorbed surface oxygen species. This investigation suggests the potential application of ZnO nanostructures for various optoelectronic device applications.

Understanding the effect of flower extracts on the photoconducting properties of nanostructured TiO2.

Here we report an easy method to improve the optoelectronic properties of commercially available TiO2 nanopowder using extracts of various flowers viz. Calendula Orange (CO), Calendula Yellow (CY), Dahlia Violet (DV), Dahlia Yellow (DY), Rabbit flower (RF), Sweet Poppy (SP), Sweet Williams (SW) and their Mixed Extracts (ME). Various analysis techniques such as UV-Vis, FTIR, FESEM, XRD, and Raman spectroscopy were used to characterize for elemental, structural and morphological properties of the unmixed/mixed TiO2 nanopowder. TiO2 nanopowder was also calcined at 550 degrees C. Thick films of the these unmixed/mixed powder were printed, using conventional screen printing method, on fluorine doped tin oxide (FTO) substrate with organic binders and dried at 45 degrees C. The photoconducting properties are investigated as a function of wavelength from ultra-violet (UV) to infra-red (IR) region at a constant illumination intensity. Photocurrent gradually decreases when irradiated from UV to IR region. In case of unmixed and uncalcined TiO2, conductance decreased continuously whereas when extracts are added, a flat region of conductance is observed. The overall effect of extracts (colour pigments) is seen as an increase in the photoconductance. Highest photoconductance is observed in case of DY flower extract. Anthocyanins, present in flowers are known to have antioxidative properties and hence can contribute in photoconduction by reducing the surface adsorbed oxygen. This investigation indicates the potential use of flower extracts for dye sensitized solar cell (DSSC).

One-pot synthesis and characterization of Nb2O5 nanopowder.

Nanosized niobium oxide powders were synthesized with a yield of approximately 87% using a simple and facile soft-chemical process. Niobium pentachloride (Nb2Cl5) was used as the precursor which was first converted into niobium ethoxide and then hydrolysed with water to synthesize niobia nanopowder. The synthesized powder was calcined at 500 degrees C for phase conversion to end-centered monoclinic as confirmed by diffraction studies and elemental analysis with a chemical composition in the ratio of Nb:O as 1:2.5. The molecular framework of Nb-O-Nb stretching and asymmetric frequency was confirmed by FT-IR, UV-visible and Raman spectroscopic studies. The size, shape and surface morphology of the powders were observed by SEM and TEM which indicated particle sizes of approximately 20 nm. The surface area of 20 m2/g, pore volume of 0.0538 cm2/g and the average pore size of 6.5 nm2 for the calcined sample were obtained with the help of nitrogen adsorption/desorption method using the Barrett-Joyner-Halenda (BJH) method which indicates that the synthesized powder can be used for catalysis and other surface sensitive applications.

A novel high yield method for dry functionalization of carbon nanotubes.

A novel and high yield (> 80%) dry method to functionalize (dry functionalization) carbon nanotubes (CNTs) using hydrothermal method, is reported here. The hydrothermal solution was prepared with HNO3, H2SO4 and H2O2 (1:3:2 vol. ratios) and reaction was carried out from 120 to 200 degrees C for 24 h. CNTs (multi wall) were kept in a way to avoid the direct contact with the solution. Treatment above 180 degrees C resulted in better functionalization of nanotubes as observed from Fourier transform infrared absorption spectroscopic (FTIR) measurements. Field emission scanning electron microscopic (FESEM) images showed that after functionalization, the nanotubes are seen with open ends, granular surface, twisted and are joined together. These clearly indicate the destruction of the graphite structure on the surface. This indicates that after treatment, CNTs reactivity has increased at the ends as well as at the side walls. X-ray Photoelectron Spectroscopic (XPS) studies show a shift in the C 1s peak position, increase in O 1s peak intensity and appearance of an N 1s peak.

Urea sensing characteristics of titanate nanotubes deposited by electrophoretic deposition method.

Urea sensing properties of titanate nanotubes (TNT) are presented here. TNT films were deposited by electrophoretic deposition (EPD) method on aluminum substrate. Prior to EPD, commercial nanoparticles of TiO2 were hydrothermally treated at 70 degrees C for 48 h after sonicating the solution for 8 h. Hydrothermal method resulted in the conversion of particles to tubular structure following the established method. Urease was covalently attached with TNT (by soaking in urease solution for 3 h). In general, conductivity of film increases after urease immobilization. The urease immobilized films were characterized for urea sensing in the concentration range of 1 mM to 500 mM. Three different sensitivity regions are observed viz. (i) lower concentrations (below 10 mM); (ii) linear region up to 100 mM and a (iii) saturation region above 100 mM. Sensors are extremely sensitive in region (i). From the elemental analyses of the films after urease immobilization, urease was found attached with TiO2, as evident by N 1s peak in the photoelectron spectra. Cyclic voltammetric studies indicated surface-confined redox couple is responsible for sensing behavior. A possible sensing mechanism is presented and discussed.