Enhanced photocatalytic performance of TiO2 nanowires by substituting noble metal particles with reduced graphene oxide

Noble metal particles have been embedded in semiconductors to improve photocatalysis efficiently, but the high cost made this approach difficult to apply widely in industry. Herein titanium dioxide/reduced graphene oxide (TiO₂/rGO) nanowires in a core-shell structure were prepared. The physicochemical properties and photocatalytic performance of the specimen were characterized in comparison with TiO₂ and TiO₂/Pt nanowires. The rGO layer and Pt nanoparticles increased chemical states of the components, reduced bandgap energy of the nanowires, enhanced visible light absorption, improved conductance and capacitance significantly. The methylene blue as catalyzed by TiO₂/Pt and TiO₂/rGO nanowires was degraded to 7.9% and 8.4% in an hour, but retained 25.7% by the TiO₂ nanowires. The properties and function of TiO₂/rGO nanowires were close to those of TiO₂/Pt nanowires, while the rGO price was much lower than that of Pt, which was of great significance for the photocatalytic application of TiO₂ heterojunction materials in industry.     

Modernized H2S-treatment of TiO2 nanoparticles: Improving quantum-dot deposition for enhanced photocatalytic performance

One of the efficient strategies to enhance light harvesting capability of metal oxides nanoparticles (NPs) is to deposit low band gap metal sulfides on them via pseudo-successive ionic layer adsorption and reaction (p-SILAR). Resultant oxide-sulfide nanocomposites have a variety of applications, however there is still a need to increase the deposition of metal sulfide in the form of quantum-dots (QDs). In this work, we have successfully enhanced the deposition of QDs on TiO₂ NPs using a modernized H₂S-treatment strategy. A rotary reactor was employed for H₂S-treatment of TiO₂ NPs, ensuing higher deposition of PbS (in TiO₂–PbS) and CdS (in TiO₂–CdS) via p-SILAR. Resultantly, dye degradation of Rhodamine B increased from 63% to 75% and 72%–84%, respectively. X-ray photoelectron spectroscopy revealed the efficacy of modernized H₂S-treatment while intensive electrochemical characterization affirmed reduction in charge carrier transfer resistances due to superior deposition of PbS and CdS QDs on TiO₂ NPs.     

Synthesis of TiO2/WO3 nanoparticles via sonochemical approach for the photocatalytic degradation of methylene blue under visible light illumination

Through an ultrasound assisted method, TiO₂/WO₃ nanoparticles were synthesized at room temperature. The XRD pattern of as-prepared TiO₂/WO₃ nanoparticles matches well with that of pure monoclinic WO₃ and rutile TiO₂ nanoparticles. TEM images show that the prepared TiO₂/WO₃ nanoparticles consist of mixed square and hexagonal shape particles about 8–12 nm in diameter. The photocatalytic activity of TiO₂/WO₃ nanoparticles was tested for the degradation of a wastewater containing methylene blue (MB) under visible light illumination. The TiO₂/WO₃ nanoparticles exhibits a higher degradation rate constant (6.72 × 10⁻⁴ s⁻¹) than bare TiO₂ nanoparticles (1.72 × 10⁻⁴ s⁻¹) under similar experimental conditions.     

Nitrogen doped TiO2 nanoparticles decorated on graphene sheets for photocatalysis applications

Nitrogen doped TiO₂ nanoparticles decorated on graphene sheets are successfully synthesized by a low-temperature hydrothermal method. The resulting GR-N/TiO₂ composites are characterized by X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-Ray photoelectron spectroscopy (XPS) and Transmission Electron Microscopy (TEM). The optical properties are studied using UV–visible diffuse reflectance spectroscopy (DRS), which confirms that the spectral responses of the composite catalysts are extended to the visible-light region and show a significant reduction in band gap energy from 3.18 to 2.64 eV. Photoluminescence emission spectra verify that GR-N/TiO₂ composites possess better charge separation capability than pure TiO₂. The photocatalytic activity is tested by degradation of methyl orange (MO) dye under visible light irradiation. The results demonstrate that GR-N/TiO₂ composites can effectively photodegrade MO, showing an impressive photocatalytic enhancement over pure TiO₂. The dramatically enhanced activity of composite photocatalysts can be attributed to great adsorption of dyes, enhanced visible light absorption and efficient charge separation and transfer processes. This work may provide new insights into the design of novel composite photocatalysts system with efficient visible light activity.     

Highly sensitive electrochemical sensor for Sudan I based on graphene decorated with mesoporous TiO2

A sensor for the highly sensitive determination of Sudan I based on the amplified electrochemical response of mesoporous TiO₂-decorated graphene (GN–TiO₂) was fabricated. The nanoparticles of TiO₂ arrayed densely and uniformly on the GN sheets, as confirmed by field emission scanning electron microscopy and transmission electron microscopy images. The electrochemical behavior of Sudan I at this sensor was studied in detail, showing that this sensor exhibited electrocatalytic activity for the oxidation of Sudan I because of the significant peak current enhancement and the lowering of oxidation overpotential. Furthermore, the experimental parameters including supporting electrolyte, volume of GN–TiO₂ suspension on electrode surface, accumulation potential, and time were optimized and the electrochemical reaction mechanism of Sudan I on this sensor was investigated. The linear range is from 3.3 nM to 0.66 μM, and the limit of detection is estimated to be 0.60 nM. At last, the sensor was used to determine Sudan I in food sample extracts, which are in good agreement with the results obtained by chromatographic method.     

EMI shielding effectiveness of graphene decorated with graphene quantum dots and silver nanoparticles reinforced PVDF nanocomposites

Graphene decorated with graphene quantum dots (G-D-GQDs) have been successfully synthesized using solvothermal cutting of graphene oxide. The incorporation of G-D-GQDs in polyvinyledene fluoride (PVDF) matrix shows the total EMI shielding effectiveness (SE_T) of 31 dB at 8 GHz. The main mechanism of high EMI shielding effectiveness is reflection and absorption of EM radiation. The high absorption of EM radiation is due to tunneling of electrons from GQDs. Further, decoration of G-D-GQDs with conducting Ag nanoparticles (G-D-GQDsAg) enhances the SE_T value to 43 dB at 8 GHz of PVDF/G-D-GQDsAg nanocomposite, due to increase in electrical conductivity of PVDF/G-D-GQDsAg nanocomposite and enhanced dispersion of G-D-GQDsAg in PVDF matrix. The incorporation of G-D-GQDs and G-D-GQDsAg in PVDF matrix also increases the thermal stability and crystallinity of PVDF. The increase in thermal stability and crystallinity are more for PVDF/G-D-GQDsAg nanocomposite as compare to PVDF/G-D-GQDs nanocomposite, due to better dispersion of G-D-GQDsAg in PVDF matrix. Thus, PVDF/G-D-GQDsAg nanocomposite having high SE_T value can shield 99.9% of electromagnetic radiation in X-band range, which make it suitable for EMI shielding application for consumer electronic equipment’s.     

Silver nanoparticles decorated on a three-dimensional graphene scaffold for electrochemical applications

Silver metal nanoparticles were decorated by electron beam evaporation on graphene foam (GF) grown by chemical vapour deposition. X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy, and atomic force microscopy were used to investigate the structure and morphology of the graphene foam/silver nanoparticles (GF/Ag). Both samples were tested as electrodes for supercapacitors. The GF/Ag exhibited a significantly higher capacitive performance, including a specific capacitance value of (~110 Fg⁻¹) and excellent cyclability in a three-electrode electrochemical cell. These results demonstrate that graphene foam could be an excellent platform for metal particles for investigating improved electrochemical performance.     

Multiwalled carbon nanotubes decorated with nitrogen, palladium co-doped TiO2 (MWCNT/N, Pd co-doped TiO2) for visible light photocatalytic degradation of Eosin Yellow in water

Multiwalled carbon nanotube (MWCNT/N), Pd co-doped TiO₂ nanocomposites were prepared by calcining the hydrolysis products of the reaction of titanium isopropoxide, Ti(OC₃H₇)₄ containing multiwalled carbon nanotubes with aqueous ammonia. The prepared samples were characterised by Fourier transform infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis, diffuse reflectance UV?CVis spectrophotometry (DRUV?CVis), XRD, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). DRUV?CVis analysis confirmed the red shift in the absorption edge at lower MWCNT percentages. SEM and TEM images showed the complete coverage of the MWCNTs with clusters of anatase TiO₂ at low MWCNT percentages. Higher MWCNT levels led to their aggregation and consequently poor coverage by N, Pd co-doped TiO₂. The photocatalytic activities of the nanocomposites were monitored by photodegradation of Eosin Yellow under simulated solar and visible light irradiation (???>?450?nm). Irradiation with simulated solar radiation gave higher dye-degradation rates compared to visible radiation. The optimum MWCNT weight percentage in the composites was found to be 0.5. High degradation-rate constants of 3.42?×?10^?2 and 5.18?×?10^?3?min^?1 were realised for the 0.5% MWCNT/N, Pd co-doped TiO₂ composite, using simulated solar light and visible light, respectively.     

Buckling of hybrid nanocomposites with embedded graphene and carbon nanotubes

With the aid of atomistic multiscale modelling and analytical approaches, buckling strength has been determined for carbon nanofibres/epoxy composite systems. Various nanofibres configurations considered are single walled carbon nano tube (SWCNT) and single layer graphene sheet (SLGS) and SLGS/SWCNT hybrid systems. Computationally, both eigen-value and non-linear large deformation-based methods have been employed to calculate the buckling strength. The non-linear computational model generated here takes into account of complex features such as debonding between polymer and filler (delamination under compression), nonlinearity in the polymer, strain-based damage criteria for the matrix, contact between fillers and interlocking of distorted filler surfaces with polymer. The effect of bridging nanofibres with an interlinking compound on the buckling strength of nano-composites has also been presented here. Computed enhancement in buckling strength of the polymer system due to nano reinforcement is found to be in the range of experimental and molecular dynamics based results available in open literature. The findings of this work indicate that carbon based nanofillers enhance the buckling strength of host polymers through various local failure mechanisms.     

Visible-light photocatalytic degradation of methylene blue with laser-induced Ag/ZnO nanoparticles

The preparation of Ag doped ZnO nanoparticles conducted through the method of laser-induction is presented in this work. The Ag/ZnO nanoparticles attained from various weight percentages of added AgNO₃ relative to ZnO were applied under visible-light irradiation for evaluating the heterogeneous photocatalytic degradations of methylene blue (MB) solutions. It was shown that the catalytic behavior of Ag/ZnO nanoparticles in the visible-light range is notably improved through the Ag deposition onto ZnO nanoparticles by the method of laser-induction with a maximum effectiveness of 92% degradation. The properties of the nanoparticles were characterized by the employments of UV-vis spectroscopy (UV-vis), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and selected-area electron diffraction (SAED).     

Sonochemical synthesis of nickel-manganous oxide nanocrumbs decorated partially reduced graphene oxide for efficient electrochemical reduction of metronidazole

In the present work, we report on the synthesis of crump-like nickel manganous oxide nanoparticles decorated partially reduced graphene oxide (NiMnO@pr-GO) nanocomposite through high-intensity ultrasonic bath sonication (ultrasonic frequency = 37 kHz and power = 150 W). The NiMnO@pr-GO nanocomposite modified glassy carbon electrode (GCE) was then employed for the electrochemical reduction of detrimental metronidazole (MNZ). The crystalline phase and formation of the NiMnO@pr-GO nanocomposites were confirmed by X-ray diffraction and other spectroscopic techniques. The cyclic voltammetry results demonstrate that this NiMnO@pr-GO nanocomposite modified GCE has a lower reduction potential and higher catalytic activity towards MNZ than do NiMnO and GO modified GCEs. Under optimized conditions, the fabricated NiMnO@pr-GO electrode can detect metronidazole over a wide linear range with a lower limit of detection of 90 nM. The sensitivity of the sensor was 1.22 µA µM^-1cm⁻² and was found to have excellent selectivity and durability for the detection of MNZ.     

Facile sonochemical synthesis of rutile-type titanium dioxide microspheres decorated graphene oxide composite for efficient electrochemical sensor

In this reports the facile and green synthesis of rutile-type titanium dioxide nanoparticles decorated graphene oxide nanocomposite via the ultrasonication process (frequency: 50 kHz, Power: 100 W/cm² and Ultrasonic type: Ti-horn). Because, the sonochemical synthesis method is simple, non-explosive and harmless method than other conventional technique. Furthermore, the synthesized material was characterized by various analytical techniques including FESEM, EDX, XRD, EIS and electrochemical methods. Then, the synthesized TiO₂ MPs@GOS composite was applied for the electrocatalytic detection of theophylline (TPL) using CV and amperometric (current-time) techniques. Captivatingly, the modified sensor has excellent electrocatalytic performance with the wider linear range from 0.02 to 209.6 µM towards the determination of theophylline and the LOD and sensitivity of the modified sensor was calculated as 13.26 nM and 1.183 μA·µM⁻¹·cm⁻², respectively. In addition, a selectivity, reproducibility and stability of the TiO₂ MPs@GOS modified GCE were analyzed towards the determination of theophylline molecule. Finally, the real time application of TiO₂ MPs@GOS modified theophylline sensor was established in serum and drug samples.     

Enhanced electrochemical performances of LiNi0.5Co0.2Mn0.3O2 cathode material co-coated by graphene/TiO2

The electrochemical performances of LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523) layered cathode material, such as poor rate capacity and cycling stability caused by undesirable intrinsic conductivity and low rate of lithium ion transportation, are not fairly good especially at elevated rate and cut-off voltage. To improve these properties, in this study, the co-coating layer of graphene and TiO₂ was constructed on NCM523 surface. The graphene/TiO₂ coating layer could effectively prevent hydrofluoric acid (HF) attacks, suppress the side reaction, accelerate the lithium ion diffusion and facilitate the electron migration. The enhancement of cycle performance and rate capacity was contributed to the uniform co-modified surface, interacting each other and thus exhibiting synergistic effects.     

石墨烯与二氧化氮的吸附特性研究

由于石墨烯的二维结构以及其超高的比表面积,因此石墨烯可以感应到一个分子量级的变化,这使得其在气体传感方面具有很大的优势。文章通过计算和分析了石墨烯与二氧化氮的系统的能带结构,态密度和电荷分布情况来说明石墨烯吸附二氧化氮后的特性变化。这有助于进一步了解了石墨烯的特性,同时进一步推动石墨烯传感的发展。     

石墨烯与二氧化氮的吸附特性研究

由于石墨烯的二维结构以及其超高的比表面积,因此石墨烯可以感应到一个分子量级的变化,这使得其在气体传感方面具有很大的优势.文章通过计算和分析了石墨烯与二氧化氮的系统的能带结构,态密度和电荷分布情况来说明石墨烯吸附二氧化氮后的特性变化.这有助于进一步了解了石墨烯的特性,同时进一步推动石墨烯传感的发展.     

A simple method for large-scale preparation of ZnS nanoribbon film and its photocatalytic activity for dye degradation

ZnS nanoribbon film has been successfully prepared by solvothermal treating of Zn foil and S powder in hydrazine hydrate without any surfactant and post-high temperature treatment. The prepared samples were characterized by XRD, SEM and PL. Results show that the obtained films were with high crystallinity and uniformity. The obtained samples were used as a photocatalyst for degradation of dye X-3B, and results show that the dye can be photocatalytically degraded with high rate by as-prepared ZnS nanoribbon film under UV light irradiation.     

Preparation of bimetal incorporated TiO2 photocatalytic nano-powders by flame method and their photocatalytic reactivity for the degradation of diluted 2-propanol

Bimetal incorporated TiO₂ photocatalysts (FeZn–TiO₂) prepared by a flame method showed high photocatalytic activity for the degradation of 2-propanol dissolved in water as compared with mono-metal incorporated or unincorporated TiO₂. By using this flame method, parameters such as uniform particle size, crystallinity as well as the anatase and rutile phase ratio (anatase/rutile) could be controlled without calcination of the catalysts at high temperatures, the parameters being important to achieve a high photocatalytic activity. The presence of a small amount of bimetals such as Fe and Zn plays a vital role as a catalyst in the formation of highly crystalline, small and uniform size particles with defined anatase/rutile phase ratio of around 60/40, this being similar to that of P-25 which is well known as a highly active photocatalyst.     

Enhanced photocatalytic performance of ultrasound treated GO/TiO2 composite for photocatalytic degradation of salicylic acid under sunlight illumination

The current research work deals with the preparation of TiO₂ and GO/TiO₂ composite by simple, chemical, cost effective hydrothermal method. Graphene oxide (GO) is prepared by modified Hummer’s method. Dispersion of GO is achieved by an ultrasonic cleaning bath for 1 h. using a power of 200 W and at a frequency of 40 kHz. The prepared catalyst material is characterized by different characterization techniques. XRD study confirms the prepared material is polycrystalline in nature. The synthesized TiO₂ and GO/TiO₂ photocatalyst materials are used to study the photocatalytic degradation of salicylic acid under sunlight illumination. GO/TiO₂ composite shows superior photocatalytic activity than TiO₂. GO/TiO₂ composite shows 57% degradation of salicylic acid. Mineralization of salicylic acid is studied using chemical oxygen demand.     

Sonophotocatalytic degradation of sodium diclofenac using low power ultrasound and micro sized TiO2

The nonsteroidal anti-inflammatory drug sodium diclofenac (DC) is an emerging water pollutant which resists conventional wastewater treatments. Here the sonophotocatalytic degradation of DC was carried out using micrometric TiO₂ (both pristine and Ag-decorated), UV-A irradiation and 20 kHz pulsed ultrasound. Sonophotocatalytic tests were compared with photolysis, sonolysis, sonophotolysis, sonocatalysis and photocatalysis data performed in the same conditions. A synergy index of over 2 was determined for tests with pristine TiO₂, while values close to 1.3 were observed for Ag-TiO₂. Reaction intermediates were studied by HPLC–MS, showing degradation mechanisms activated by hydroxyl radicals. Similar pathways were identified for photocatalytic and sonophotocatalytic tests, although the latter led to more oxidized compounds. Different reactor configurations (static and dynamic set ups) were studied. Sequential and simultaneous application of UV light and ultrasound led to similar performance. The role of water matrix was investigated using ultrapure and drinking water, showing marked detrimental effects of electrolytes on the DC degradation. Overall, the combined treatment proved more efficient than photocatalysis alone especially in demanding working conditions, like in drinking water matrices.     

Manipulation of inherent characteristics of graphene through N and Mg atom co-doping; a DFT study

First-principles calculations were performed to investigate the structural, electronic, magnetic and optical properties of nitrogen (N) and magnesium (Mg) atom co-doped graphene systems. We observed that, N and Mg atom co-doping in graphene, introduces half-metallic properties in the electronic structure of graphene, introduces ferromagnetism behavior along with new trends in optical properties of graphene. Doping site and concentration of N and Mg atoms in graphene was changed and resulting effects of these changes on aforementioned properties were investigated. Through density of states plots we observed that, Mg atom sp orbitals mainly induced magnetic moments in graphene. It was revealed that, N/Mg atoms substitution in graphene introduces a red shift in absorption spectrum towards visible range and a finite absorption coefficient quantity value in 0 to 3 eV and 7 to 11 eV energy intervals is also produced, that is unavailable for absorption spectrum of intrinsic graphene. Moreover, N/Mg atoms co-doping produces increment in the reflectivity parameter of graphene in low lying energy region, while producing diminishing behavior in the higher energy range. These results offer a possibility to tune electronic, magnetic and optical characteristics of graphene sufficiently for utilization in graphene based spintronic and optoelectronic devices.