Enhanced Photocatalytic Degradation Activity of 2-D Graphitic Carbon Nitride-SnO2 Nanohybrids.

In this paper, we report on the facile synthesis of graphitic carbon nitride (g-C3N4)-tin oxide (SnO2) nanohybrid as an efficient photocatalyst prepared via sol-gel method. SnO2 nanoparticles are pointcontacted with g-C3N4. The results of physio-chemical characterizations such as SEM-EDAX, XRD, BET, FT-IR and UV-DRS spectra reveal the successful formation and integration of nanohybrid. The photocatalytic activity has been studied by using methylene-blue as a model dye for degradation. It has been observed that the pseudo-first order rate constant was increased up to 1.78 times compared with pure SnO2. The enhanced photocatalytic activity was ascribed from the inhibition of electron-hole recombination where g-C3N4 nanosheets acts as an electron receiver from SnO2 via point contact. This mechanism is further verified via photoluminescence spectra. Our results prominently show new insights and potential applications of g-C3N4-SnO2 nanohybrids in the waste water treatment and environmental remediation sectors.

Enhanced Photocatalytic Properties of Nanostructured WO3 Semiconductor-Photocatalyst Prepared via Hydrothermal Method.

Ground and distilled water-mediated tungsten trioxide (WO3) nanostructures are prepared via hydrothermal approach. The physical and surface chemical properties of catalyst are analyzed using XRD, SEM-EDAX, HR-TEM, FT-IR, UV-DRS, Zeta potential and photoluminescence spectroscopy. It is confirmed that ground water has high impacts on the materials properties such as crystallinity and morphology. HR-TEM results proved the transformation of single crystalline to polycrystalline for sample W1 and W3 respectively. The photocatalytic efficiency of the various catalyst was analyzed by the degradation of methylene blue as a probe dye-molecule which was monitored by UV-vis spectroscopy. The decolorization efficiency was observed as 1.14 times maximized in distilled water prepared catalyst when compared with ground water prepared catalyst. Moreover, the persulfate activation was found as 2.3 fold amplified in distilled water prepared catalyst when compared with other catalyst. On the development of various water-assisted WO3 semiconductor photocatalysis, this work can provide new insights into the design of novel photocatalyst for potential applications in the energy and environmental remediation sectors.

Influence of Morphology and Common Oxidants on the Photocatalytic Property of ß-SnWO4 Nanoparticles.

In this paper, we report a simple, cost effective and surfactant-free method for synthesizing different morphology of ß-SnWO4 with irregular, spherical, flake-like and leaf-like structures by using sonochemical method followed by calcination. A well dispersed and highly crystalline ß-SnWO4 crystallites with various sizes have been prepared. The samples were characterized by using X-ray diffraction (XRD), scanning electron microscope (SEM), UV-vis spectroscopy, particle size and Zeta potential analyser. The SEM images reveal the successful preparation of an irregular, spherical, flake-like and leaf-like structure of ß-SnWO4. The absorption maximum of as-prepared different structures of ß-SnWO4 was observed in visible region. The degradation efficiency was found to be increased in leaf-like structures compared to irregular, spherical and flake-like structures of ß-SnWO4. Further, an enhanced photocatalytic effect was observed in leaf-like ß-SnWO4 nanoparticles while the common oxidants such as peroxomonosulphate (PMS), peroxodisulphate (PDS) and hydrogen peroxide (H2O2) were added. The degradation efficiency of these oxidants was found in the order of PMS > H2O2 > PDS. Generally these oxidants act as electron scavengers. From our experimental results, it is found that maximum efficiency of 93% was achieved when PMS was added. This shows the vital role of common oxidants in photocatalytic characteristics and their future applications in waste-water treatment.

Facile Synthesis of Vanadium-Pentoxide Nanoparticles and Study on Their Electrochemical, Photocatalytic Properties.

Vanadium pentoxide (V2O5) nanoparticles were synthesized via an anionic, cationic and non-ionic surfactant-assisted hydrothermal method. The synthesized nanoparticles were characterized by using powder X-ray diffractometer, Scanning Electron Microscope, High Resolution Transmission Electron Microscope and UV-Vis spectroscopy. The experimental results confirm the formation of vanadium pentoxide nanoparticles. Vanadium pentoxide crystalline nanoparticles were prepared from various surfactants named Sodium Dodecyl Sulphate (SDS), Cetyl Trimethyl Ammonium Bromide (CTAB) and Triton-X, resulting the crystallite size of 61.6 nm, 27.5 nm and 46 nm respectively. From the electrochemical studies, it is found that vanadium pentoxide prepared with CTAB exhibit good cycle stability when compared with other two samples. Also the ionic-conducting behavior of the materials was investigated by using impedance analysis. In addition, the photocatalytic studies were performed and found better photocatalytic efficiency in V2O5 prepared with SDS, obtained through the degradation of MO dye under UV light irradiation. Our results show that Vanadium pentoxide can be a suitable candidate for photocatalytic application and as electrode in development of futuristic supercapacitors. Also this can be employed in various environmental eco-friendly applications.

Investigation of transfer characteristics of high performance graphene flakes.

In this article, we attempted a study on field effect transport characteristics of graphene flakes. These graphene flakes were exfoliated by mechanical peeling-off technique and the electrical contacts were patterned by photo-lithographic method. Graphene devices have shown better transfer characteristics which was obtained even in low-voltage (< 5 V). Back-gated graphene transistors were patterned on oxidized silicon wafers. A clear n-type to p-type transition at Dirac point and higher electron drain-current modulation in positive back-gate field with current minimum (the Dirac point) were observed at V(GS) = -1.7 V. The carrier mobility was determined from the measured transconductance. The transconductance of the graphene transistors was observed as high as 18.6 microS with a channel length of 68 microm. A maximum electron mobility of 1870 +/- 143 cm2/V x s and hole mobility of 1050 +/- 35 cm2/V x s were achieved at a drain bias 2.1 V which are comparatively higher values among reported for mechanically exfoliated graphene using lithographic method. The fabricated devices also sustained with high-current density for 40 hr in continuous operation without any change in device resistance, which could be applied for robust wiring applications.

Observation of nonvolatile resistive memory switching characteristics in Ag/graphene-oxide/Ag devices.

In this paper, we report highly stable and bipolar resistive switching effects of Ag/Graphene oxide thinfilm/Ag devices. The graphene-oxide (GO) thinfilms were prepared on Ag/SiO2/Si substrates by spin-coating technique. The Ag/GO/Ag devices showed a steady and bipolar resistive switching characteristic. The resistance switching from low resistance state (LRS) and high resistance state (HRS) with the resistance ratio of HRS to LRS of about 10 which was attained at a voltage bias of 0.1 V. Based on the filamentary conduction model, the dominant conduction mechanism of switching effect was well explained. Our results show GO can be a promising candidate for future development of nonvolatile memory devices.

Evaluation of Antimicrobial and Antibiofilm Activity of Citrus medica Fruit Juice Based Carbon Dots against Pseudomonas aeruginosa.

Pseudomonas aeruginosa (P. aeruginosa) is one of the common immortal pathogens that cause intense chronic infections in low-immunity patients, significantly evading the immune system and suppressing the respiratory system. This work reports on the synthesis of prominent members of the carbon family, carbon quantum dots (CQDs), from a natural carbon precursor, Citrus medica (C. medica) fruit, and their inhibiting property against P. aeruginosa. CQDs synthesized by the conventional hydrothermal method with an average particle size of 4.5 nm exhibit renowned antimicrobial properties. To enhance the properties of the CQDs, nitrogen was doped using ammonium hydroxide as a nitrogen source, and absorption and fluorescence studies and the elemental composition of CQDs were also reported. CQDs potentially inhibited the growth of bacteria at the lowest concentration level of 1.25% (v/v). Similarly, CQDs moderately inhibited biofilm formation at the concentration level of 0.07% (v/v) for both clinical and control strains of P. aeruginosa. A fluorescence microscopy study revealed that the treated strain shows a moderately reduced biofilm formation when compared to the control strain of P. aeruginosa PAO1.

Raman Spectroscopy-Assisted Characterization of Nanoform MoS2 Thin Film Transistor.

In this paper, we report the simple preparation and investigation of electrical transport properties of nanoform MoS2 thin film transistor (TFT) devices. MoS2 nanoparticles were synthesized by using the hydrothermal method. The physiochemical characterizations such as UV-vis, Fourier transform infrared, X-ray diffraction, and Raman spectroscopy studies were performed. Spin-coating was used to make the thin film on which silver electrodes were made. We observed nonlinear current-voltage (I-V) characteristics; however, the symmetricity was found in the I-V curve which confirms the no formation of the Schottky barrier between thin film and electrodes. Transistor transfer characteristics reveal that the TFT device is n-doped as more drain current modulation is observed when the positive gate voltage is applied. The relationship between gate-current and gate voltage studies concludes that there is no leakage gate current in the TFT device which further confirms the good reliability of transfer characteristics of a device. The device mobility was calculated as ~10.2 cm2/Vs, and the same was explained with plausible reason supported with Raman spectra analysis.

Ferroelectric-semiconductor BaTiO3-Ag2O nanohybrid as an efficient piezo-photocatalytic material.

Piezo-photocatalysis is a new concept of utilizing nanohybrids comprising piezoelectric and photocatalytic materials for enhancement in advanced oxidation process under the presence of light and mechanical energy. In this study, we explored the effectiveness of piezo-photocatalysis via examining their catalytic activity towards the degradation of azo dye (Rhodamine-B) and standard pollutant (Phenol) catalyzed by ferroelectric-semiconductor (BaTiO3-Ag2O) nanohybrids. Further, the enhancement in piezo-photocatalysis has been achieved via persulfate activation and the role of free radicals was examined by quenchers. A plausible mechanism for the improved piezo-photocatalysis of BaTiO3-Ag2O nanohybrid using persulfate activation has been discussed in detail. The removal mechanism of Rhodamine-B has been investigated using analytical techniques such as HPLC and EPR. Our experimental study demonstrated that the combination of piezo-photocatalysis with persulfate activation will provide higher reaction rate which will be beneficial towards the degradation of complex molecular pollutants derived from industrial sectors.

Nanoscale fabrication of a three-dimensional stack of graphene layers using a focused ion beam.

A top-down nanoscale stack fabrication approach involving the high-precision carving of a stack of graphene layers from a thin graphite flake via focused-ion-beam (FIB) three-dimensional (3D) etching is presented. Using this technology, etching was performed in the c-axis with the height of a few tens of nanometres. By reducing the stack height to 50 nm, a 3D stack of graphene layers coupled in a stacked manner was fabricated. The transport characteristics of the stack in the c-axis were studied and compared with the transport characteristics of the stack with a larger in-plane area and stack height value. The observed conductivity of the nanostack with a 50 nm height was one order smaller than the conductivity of the stack with a larger in-plane area and stack height value. Nonlinear current-voltage (I-V) characteristics were observed in all the studied temperatures, but the stack with a larger in-plane area and stack height value showed nonlinear characteristics only at lower temperatures. The observation of these temperature-dependent I-V characteristics was discussed in detail, and the tunneling characteristics were investigated using the Fowler-Nordheim tunneling model, which showed the best fit to the experiment data in this study.

Fabrication and characteristics of submicron stacked-junctions on thin graphite flakes.

We report on the fabrication and transport characteristics of submicron-size stacks along c-axis of thin graphite flakes. The stacks were fabricated using a three-dimensional focused-ion-beam (FIB) etching technique. The stack with in-plane area A of 0.5 microm2 showed nonlinear concave-like I-V characteristics even at 300 K; however the stack with A of > 0.5 microm2 were shown an ohmic-like I-V characteristic at 300 K for both low and high-current biasing. It turned into nonlinear characteristics when the temperature goes down. The in-plane area dependence of stack capacitance were discussed and the observed capacitance of stack with A of 0.5 microm2 is smaller than the capacitance of stack with A of 1 microm2 which causes the nonlinear I-V characteristics in stack with A of 0.5 microm2 even at 300 K.

Temperature dependence of transport anisotropy of planar-type graphite nanostructures fabricated by focused ion beam.

We report in this paper on the observation of temperature-dependent anisotropic transport behavior for planar-type nanostructures (in-plane and out-of-plane) fabricated on a thin graphite layer using a three-dimensional focused-ion-beam (FIB) etching technique. The transport characteristics were studied for several in-plane areas with sizes of 6 x 6 microm2, 6 x 4 microm2 and 6 x 2 microm2 planar-type structures/patterns and out-of-plane structures with the dimensions of 2 x 1 x 0.3 microm3. Both in-plane (rho(a)) and out-of-plane (rho(c)) resistivities are measured for these structures and the ratio of resistivity anisotropy is determined. The observed values of anisotropy ratio rho(c)/rho(a) were approximately 12.5 at 300 K and approximately 54 at 25 K. The room temperature value of rho(c)/rho(a) varies by a few orders from the values of previously reported anisotropy results of bulk pyrolytic graphite. However, the value of resistivity anisotropy increases with decreasing temperature, which is an identical behavior to bulk pyrolytic graphite. From current (I)-voltage (V) characteristics, we observed an ohmic behavior at 300 K for both low- and high-current biasing. This behavior turns into nonlinear characteristics when the temperature goes down. As these fabricated structures consist of multiple elementary junctions along the c-axis, nonlinear I-V characteristics result. The impurity assisted interlayer hopping conduction and thermal excitation of carriers play a key role in this effect.

Graphene-oxide (GO)-Fe3+ hybrid nanosheets with effective sonocatalytic degradation of Reactive Red 120 and study of their kinetics mechanism.

This work demonstrates the preparation of graphene-oxide (GO)-Fe(3+) hybrids nanosheets and their high bleaching efficiency on the dye "Reactive Red 120 (RR 120)" by using sonocatalytic degradation. Sonocatalytic degradation was enhanced by using oxidants like PMS (peroxomonosulphate), PDS (peroxodisulphate), H2O2 (hydrogen peroxide) and KIO4 (potassium periodate). Our observations manifested that the degradation of the dye "RR 120" was found to be multiplied by addition of oxidants in the order of PMS>H2O2>PDS>KIO4. The effect of inorganic ions was studied by the addition of SO4(2-), Cl(-), H2PO4(-) and HCO3(-). These results revealed that an addition of inorganic anionic decreases the degradation efficiency of RR 120 at high concentration. The trend of decreased degradation efficiency was SO(-)4