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Rose bengal-integrated electrospun PAN nanofibers displayed high antimicrobial efficacy against both Gram-negative Escherichia coli and Gram-positive Bacillus subtilis bacteria under white light irradiation. This methodology offers a feasible strategy for water disinfection.

A quantitative approach was developed to systematically evaluate the antimicrobial activity of CuWO4/CuS hybrid composites. This approach offers a new way to search for effective combinations of two or more semiconductors for pathogen disinfection.

2D heterostructures offer new opportunities for harnessing a wider range of the solar spectrum in high-performance photovoltaic devices. Here, we explore a type-II p–n heterojunction, by exploiting air-stable tellurene (Te) in combination with MoS2, to study its charge transfer for photovoltaic applications. The charge transfer of MoS2/Te heterojunction is confirmed by photoluminescence spectroscopy, Raman spectroscopy and Kelvin probe force microscopy. The exciton binding energy for MoS2/Te heterojunction is estimated to be around 10 meV, which is much lower than that for monolayer MoS2. This strategy can be exploited to develop next-generation intrinsically ultrathin light-harvesting devices.

This study investigates the phase-controlled growth of flakes and films of 2D MoTe2 by atmospheric-pressure chemical vapor deposition and presents a thorough understanding on the growth mechanism.

Bismuth oxyselenide (Bi2O2Se) has recently emerged as a promising 2-D material for high-performance electronic and optoelectronic applications. However, its true potential is yet to be explored for chemical sensing applications. The present investigation highlights the first demonstration of a Bi2O2Se nanosheets-based sensor for nonenzymatic electrochemical detection of hydrogen peroxide (H2O2). A solution-phase method is employed to synthesize Bi2O2Se nanosheets. Cyclic voltammetry is performed to study the quantitative detection of H2O2 with a reduction potential of –0.68 V versus Ag/AgCl in nitrogen-saturated 0.1 M PBS (pH 7.4). The Bi2O2Se nanosheets-based H2O2 sensor shows efficient detection of H2O2 in the range of 50–500 μM with a sensitivity of 100 μA mA−1 cm−2, and negligible interference was observed for most of the common interferents such as NaCl, ascorbic acid, uric acid, and dopamine. Furthermore, the applicability of this electrochemical approach for practical applications is confirmed by the observation of concentration-dependent effect of H2O2 on the reduction current in artificial sweat, making Bi2O2Se nanosheets a compelling electrocatalyst candidate for the development of new wearable glucose sensors.

MXenes have attracted great attention as promising substrates for surface-enhanced Raman scattering (SERS) applications. However, the underlying SERS mechanism has not been a focus of any investigation. Herein, we report the first systematic experimental study on the SERS activity of titanium carbide (Ti3C2TX) nanosheets with thicknesses ranging from 5 to 120 nm, using methylene blue (MB) as a probe molecule. The experimental and mathematical modeling results show that the Raman enhancement factor (EF) increases monotonically with the increasing thickness of Ti3C2TX nanosheets; however, it falls drastically around a sheet thickness of 0.8 and 1.0 μm under 532 and 633 nm laser excitations, respectively. The Raman EF reaches a maximum value around a thickness of 2.0 μm, suggesting that a maximum EF can be achieved with a 2.0 μm-thick Ti3C2TX film substrate. The thickness dependence of the Raman enhancement can be accounted for by the adsorption and intercalation of MB molecules into the interlayer spacing of Ti3C2TX. Furthermore, by combining experimental observations and numerical calculation, we confirm that the charge-transfer mechanism is dominantly responsible for Raman enhancement on Ti3C2TX. Additionally, we report an observation of resonance coupling of charge transfer and molecular transition as a contributing factor to the higher EF obtained with a 633 nm laser excitation. Taken together, these findings have significant implications for cost and performance optimization in designing MXene-based SERS substrates for next-generation chemical and biological sensing platforms.

Herein we report enhanced photocatalytic degradation of methylene blue by a novel composite material, which consists of cellulose acetate (CA), polyvinylpyrrolidone (PVP), and TiO2 nanofibers prepared by one-pot electrospinning. This study describes a strategy for in situ synthesis of TiO2 nanofibers within a porous two-polymer electrospun nanofiber membrane. A hybrid composite that utilizes both the absorptive properties of CA and the photocatalytic oxidative properties of TiO2 was created. TiO2 nanofibers were created by electrospinning a bipolymer system consisting of PVP and CA with titanium isopropoxide (TIP) in a mixture of acetic acid, acetone and N, N-dimethylacetamide. Pores were introduced by dissolving PVP to increase surface area and enhanced access to TiO2 and CA. Small sheets of this material were able to show substantial degradation of methylene blue (10–5 M) in as little as one day. In four days, the porous membrane exhibited approximately 200% enhancement in its removal efficiency of methylene blue, as compared with the as-synthesized CA/PVP/TiO2 and the PVP/TiO2 nanofiber sheets. This study offers a robust method for synthesis of this two-polymer material with variable quantities of TIP and demonstrates the potential applicability of electrospun hybrid polymer/TiO2 nanofiber composites as thin fibrous catalytic surfaces.

Recently, a zipper two-dimensional (2D) material Bi2O2Se belonging to the layered bismuth oxychalcogenide (Bi2O2X: X = S, Se, Te) family, has emerged as an alternate candidate to van der Waals 2D materials for high-performance electronic and optoelectronic applications. This hints towards exploring the other members of the Bi2O2X family for their true potential and bismuth oxysulfide (Bi2O2S) could be the next member for such applications. Here, we demonstrate for the first time, the scalable room-temperature chemical synthesis and near-infrared (NIR) photodetection of ultrathin Bi2O2S nanosheets. The thickness of the freestanding nanosheets was around 2-3 nm with a lateral dimension of ∼80-100 nm. A solution-processed NIR photodetector was fabricated from ultrathin Bi2O2S nanosheets. The photodetector showed high performance, under 785 nm laser illumination, with a photoresponsivity of 4 A W-1, an external quantum efficiency of 630%, and a normalized photocurrent-to-dark-current ratio of 1.3 × 1010 per watt with a fast response time of 100 ms. Taken together, the findings suggest that Bi2O2S nanosheets could be a promising alternative 2D material for next-generation large-area flexible electronic and optoelectronic devices.

Transition metal carbides (MXenes) are an emerging family of highly conductive two-dimensional materials with additional functional properties introduced by surface terminations. Further modification of the surface terminations makes MXenes even more appealing for practical applications. Herein, we report a facile and environmentally benign synthesis of reduced Ti3C2Tx MXene (r-Ti3C2Tx) via a simple treatment with L-ascorbic acid at room temperature. r-Ti3C2Tx shows a six-fold increase in electrical conductivity, from 471 ± 49 for regular Ti3C2Tx to 2819 ± 306 S m−1 for the reduced version. Additionally, we show an enhanced oxidation stability of r-Ti3C2Tx as compared to regular Ti3C2Tx. An examination of the surface-enhanced Raman scattering (SERS) activity reveals that the SERS enhancement factor of r-Ti3C2Tx is an order of magnitude higher than that of regular Ti3C2Tx. The improved SERS activity of r-Ti3C2Tx is attributed to the charge transfer interaction between the MXene surface and probe molecules, re-enforced by an increased electronic density of states (DOS) at the Fermi level of r-Ti3C2Tx. The findings of this study suggest that reduced MXene could be a superior choice over regular MXene, especially for the applications that employ high electronic conductivity, such as electrode materials for batteries and supercapacitors, photodetectors, and SERS-based sensors.

Recently, a zipper two-dimensional (2D) material Bi

Microbial contamination of drinking water and air is an alarming phenomenon that has attracted increasing global attention. Although many advances in microbial disinfection have been made over the years, robust, rapid, inexpensive and field-deployable strategies are still urgently needed to address this public health issue. Herein we report the preparation of antimicrobial nanofibrous membranes, which involves incorporation of highly porous electrospun polyacrylonitrile (PAN) membranes with 1-chloro-2,2,5,5-tetramethyl-4-imidazolidinone (MC) by two different approaches, namely, blend electrospinning and soaking. The functionalized membranes were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, and titrimetry, and their antimicrobial efficacies were evaluated against two bacteria (Klebsiella pneumoniae and Escherichia coli). The MC-decorated electrospun PAN membranes inactivated both bacterial strains within 2 min of contact time. Moreover, the MC-soaked PAN membrane showed excellent disinfection efficacy against aerosolized E. coli after an exposure of 30 min. The simplicity, cost-effectiveness, versatility, and scalability of the electrospinning process, together with the superior antimicrobial activity of N-halamines make it a promising solution for water disinfection, and for the inactivation of airborne microorganisms.

We, herein, report an eco-friendly low temperature route for the gram-scale synthesis of copper indium selenide nanoparticles. We have also shown the possibility of using CuInSe₂ nanoparticles in infrared photodetection by maneuvering the photoconductive property. We rationalize the long-lived trap states to be the cause for the observed photoconductive gain. It is worth noting that the photoresponse time of the device was found to be faster than 0.1 s.

We, herein, report an eco-friendly low temperature route for the gram-scale synthesis of copper indium selenide nanoparticles. We have also shown the possibility of using CuInSe₂ nanoparticles in infrared photodetection by maneuvering the photoconductive property. We rationalize the long-lived trap states to be the cause for the observed photoconductive gain. It is worth noting that the photoresponse time of the device was found to be faster than 0.1 s.

Gallium telluride (GaTe) is a layered material, which exhibits a direct bandgap (∼1.65 eV) regardless of its thickness and therefore holds great potential for integration as a core element in stretchable optomechanical and optoelectronic devices. Here, we characterize and demonstrate the elastic properties and electromechanical resonators of suspended thin GaTe nanodrums. We used atomic force microscopy to extract the Young's modulus of GaTe (average value ∼39 GPa) and to predict the resonance frequencies of suspended GaTe nanodrums of various geometries. Electromechanical resonators fabricated from suspended GaTe revealed fundamental resonance frequencies in the range of 10-25 MHz, which closely match predicted values. Therefore, this study paves the way for creating a new generation of GaTe based nanoelectromechanical devices with a direct bandgap vibrating element, which can serve as optomechanical sensors and actuators.

There has been considerable interest in the germanium and tin graphane analogues due to their potential as optoelectronic building blocks, and novel topological materials. Here, we have synthesized for the first time alloyed germanium/tin graphane analogues from the topochemical deintercalation of CaGe2–2xSn2x (x = 0–0.09) in aqueous HCl. In these two-dimensional alloys, the germanium atom is terminated with hydrogen while tin is terminated with hydroxide. With greater tin incorporation, the band gap systematically shifts from 1.59 eV in GeH down to 1.38 eV for Ge0.91Sn0.09H0.91(OH)0.09, which allows for more sensitive photodetection at lower energies. In contrast to germanane’s oxidation resistance, the Ge and Sn atoms in these graphane alloys rapidly oxidize upon exposure to air. This work demonstrates the possibility of creating functional tin-incorporated group IV graphane analogues.

Interaction of graphene, graphene oxide, and related nanocarbons with radiation gives rise to many novel properties and phenomena. Irradiation of graphene oxide in solid state or in solution by sunlight, UV radiation, or excimer laser radiation reduces it to graphene with negligible oxygen functionalities on the surface. This transformation can be exploited for nanopatterning and for large scale production of reduced graphene oxide (RGO). Laser-induced dehydrogenation of hydrogenated graphene can also be used for this purpose. All such laser-induced transformations are associated with thermal effects. RGO emits blue light on UV excitation, a feature that can be used to generate white light in combination with a yellow emitter. RGO as well as graphene nanoribbons are excellent detectors of infra-red radiation while RGO is a good UV detector.

Inorganic and organic semiconductor devices are generally viewed as distinct and separate technologies. Herein we report a hybrid inorganic-organic light-emitting device employing the use of an air stable polymer, Poly (9,9-dioctylfluorene-alt-benzothiadiazole) as a p-type layer to create a heterojunction, avoiding the use of p-type GaN, which is difficult to grow, being prone to the complex and expensive fabrication techniques that characterises it. I-V characteristics of the GaN-polymer heterojunction fabricated by us exhibits excellent rectification. The luminescence onset voltage is typically about 8-10 V. The device emits yellowish white electroluminescence with CIE coordinates (0.42, 0.44). (C) 2011 Elsevier B.V. All rights reserved.

The use of reduced graphene oxide (RGO) and graphene nanoribbons (GNRs) as infrared photodetectors is explored, based on recent results dealing with solar cells, light-emitting devices, photodetectors, and ultrafast lasers. IR detection is demonstrated by both RGO and GNRs (see image) in terms of the time-resolved photocurrent and photoresponse. The responsivity of the detectors and their functioning are presented.

Room-temperature sensing characteristics for H2, ethanol, NH3, H2S and water have been investigated with thick-film sensors based on GaN nanoparticles, prepared by a simple chemical route. In general, GaN nanoparticles exhibit satisfactory sensor properties for these gases and vapors even at room temperature. The sensitivity for ethanol is found to be highest, the sensitivity and recovery times being smallest. Gas sensor properties of GaN seem to be related to intrinsic defects, which act as sorption sites for the gas molecules.

Alloyed Ge/Sn graphane analogues are prepared by topochemical deintercalation of CaGe2-2xSn2x (x = 0—0.09) in conc.

Hybrid organic/inorganic van der Waals solid TiS2(en) is prepared by solvothermal reaction of a sulfur solution in en mixed with a TiCl4 solution in PhCl (Teflon cup in evacuated Parr reactor, 200—220 °C, 5 d) followed by purification via repeated recrystallization of the gel-like product and centrifugation.

Negative differential resistance (NDR) has been observed for the first time above room temperature in gallium nitride nanocrystals synthesized by a simple chemical route. Current-voltage characteristics have been used to investigate this effect through a metal-semiconductor-metal (M-S-M) configuration on SiO2. The NDR effect is reversible and reproducible through many cycles. The threshold voltage is approximately 7 V above room temperature.

The synthesis of germanane (GeH) has opened the door for covalently functionalizable 2D materials in electronics. Herein, we demonstrate that GeH can be electronically doped by incorporating stoichiometric equivalents of phosphorus dopant atoms into the CaGe2 precursor. The electronic properties of these doped materials show significant atmospheric sensitivity, and we observe a reduction in resistance by up to three orders of magnitude when doped samples are measured in water-containing atmospheres. This variation in resistance is a result of water activation of the phosphorus dopants. Transport measurements in different contact geometries show a significant anisotropy between in-plane and out-of-plane resistances, with a much larger out-of-plane resistance. These measurements along with finite element modeling results predict that the current distribution in top-contacted crystals is restricted to only the topmost, water activated crystal layers. Taken together, these results pave the way for future electronic and optoelectronic applications utilizing group IV graphane analogues.

Corrigendum to ‘‘Electroluminescence from GaN-polymer heterojunction’’ [J. Lumin. 131 (2011) 2612–2615] Basant Chitara , Nidhi Lal , S.B. Krupanidhi , C.N.R. Rao a,b a Materials Research Centre, Indian Institute of Science, Bangalore 560012, India b International Centre for Materials Science and CSIR Centre for Excellence in Chemistry, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore 560064, India

Electronic properties of graphene have been studied more extensively than its photonic applications, in spite of its exciting optical properties. Recent results on solar cells, light emitting diodes and photodetectors show its true potential in photonics and optoelectronics. Here, we have explored the use of reduced graphene oxide as a candidate for solution processed ultraviolet photodetectors. UV detection is demonstrated by reduced graphene oxide in terms of time resolved photocurrent as well as photoresponse. The responsivity of the detectors is found to be 0.12 A/W with an external quantum efficiency of 40%. (C) 2011 American Institute of Physics. [doi:10.1063/1.3640222]