A simplistic design of a self-powered UV-photodetector device based on hybrid r-GO/GaN is demonstrated.Under zero bias, the fabricated hybrid photodetector shows a photosensivity of ∼ 85% while ohmic contact GaN photodetector with identical device structure exhibits only ∼5.3% photosensivity at 350 nm illumination (18 µW/cm 2 ). The responsivity and detectivity of the hybrid device were found to be 1.54 mA/W and 1.45×10 10 Jones (cm Hz ½ W −1 ), respectively at zero bias with fast response (60 ms), recovery time (267 ms) and excellent repeatability. Power density-dependent responsivity & detectivity revealed ultrasensitive behaviour under low light conditions. The source of observed self-powered effect in hybrid photodetector is attributed to the depletion region formed at the r-GO and GaN quasi-ohmic interface.The tremendous progress in gallium nitride (GaN) based light emitting diodes (LEDs), 1 laser diodes 2 , and other GaN based devices, namely, UV photodetector (PD) has attracted a great deal of interest from research community. 3 Being chemically inert and thermally stable, they are the most suitable for applications such as flame detection, secure space communication and ozone layer monitoring. 4,5 To match the requirements for such applications in remote and extreme environment, it is highly desirable for the UV devices to be ultrasensitive, with fast response and operate in self-powered mode. However, inherent high defect density associated with as-grown epitaxial GaN films limits its performance. 6The various schemes of metal-semiconductor (M-S) interfaces have been used to improve the UV-PDs device performance. The use of two different metal electrodes on n-GaN with modulating Schottky barrier height leads to a fast response speed but limited reverse saturation current density. 7 Earlier study has shown Schottky contact photodiode of Ni/GaN/Au with asymmetric interdigitated finger electrodes having a responsivity of 5 mA/W in self-powered mode at UV illumination. 8 Recently, Sun et al. have reported a high responsivity of 104 mA/W at zero bias voltage of interdigitated Schottky contact photodiode of Ni (80 nm) /GaN/Ti (20 nm) /Al (60 nm) device. 9 On the other hand, the use of highly transparent conductive electrodes (TCE) such as indium-tin-19 W. S. Hummers and R. E. Offeman, J. Am. Chem. Soc. 80, 1339 (1958).

Compact optical detectors with fast binary photoswitching over a broad range of wavelength are essential as an interconnect for any light‐based parallel, real‐time computing. Despite of the tremendous technological advancements yet there is no such single device available that meets the specifications. Here a multifunctional self‐powered high‐speed ultrabroadband (250–1650 nm) photodetector is reported based on graphitic carbon‐nitride (g‐C3N4)/Si hybrid 2D/3D structure. The device shows a novel binary photoswitching (change in current from positive to negative) in response to OFF/ON light illumination at small forward bias (≤0.1 V) covering 250–1350 nm. At zero bias, the device displays an extremely high ON/OFF ratio of ≈1.2 × 105 under 680 nm (49 µW cm−2) illumination. The device also shows an ultrasensitive behavior over the entire operating range at low light illuminations, with highest responsivity (1.2 A W−1), detectivity (2.8 × 1014 Jones), and external quantum efficiency (213%) at 680 nm. The response and recovery speeds are typically 0.23 and 0.60 ms, respectively, under 288 Hz light switching frequency. Dramatically improved performance of the device is attributed to the heterojunctions formed by the ultrathin g‐C3N4 nanosheets embedded in the Si surface.

We report the growth of continuous large area bilayer films of MoS2 on different substrates by pulsed laser deposition (PLD). The growth parameters for PLD were modified in such a way that results in bilayer 2D-MoS2 films on both c-Al2O3 (0001) (sapphire) and SiO2/Si (SO) substrates. The bilayer large area crystalline nature of growth in the 2 H-phase is determined by Raman spectroscopy. Cross-sectional transmission electron microscopy confirms the distinct thinnest ordered layered structure of MoS2. Chemical analysis reveals an almost stoichiometric 2 H-phase on both the substrates. The photoluminescence intensities of both the films match very well with those of the corresponding exfoliated flakes, as well as chemical vapor deposited (CVD) films as reported in the literature. The in-situ post growth annealing with optimal film thickness acts as a solid phase epitaxy process which provides continuous crystalline layers with a smooth interface and regulates the photoluminescence properties. In contrast, the PLD grown MoS2 monolayer shows poor crystalline quality and non-uniform coverage compared to that with the exfoliated and CVD grown films.

Integration of two-dimensional reduced graphene oxide (rGO) with conventional Si semiconductor offers novel strategies for realizing broadband photodiode with enhanced device performance. In this quest, we have synthesized large bandgap rGO and fabricated metal-free broadband (300-1100 nm) back-to-back connected np-pn hybrid photodetector utilizing drop casted n-rGO/p + -Si heterojunctions with high performance in NIR region (830 nm). With controlled illumination, the device exhibited a peak responsivity of 16.7 A W −1 and peak detectivity of 2.56×10 12 Jones under 830 nm illumination (11 μW cm −2 ) at 1 V applied bias with fast response (∼460 μs) and recovery time (∼446 μs). The fabricated device demonstrated excellent repeatability, durability and photoswitching behavior with high external quantum efficiency (∼2.5×10 3 %), along with ultrasensitive behavior at low light conditions.

We have demonstrated a heterojunction photodetector (PD) based on reduced graphene oxide (r-GO) and metal−organic chemical vapor deposition (MOCVD)-grown gallium nitride (GaN) that can sense very low light intensities in the above-band-gap and below-band-gap regimes, showing no and high photoconductive gains, respectively. The current− voltage characteristics of the device transforms from quasi photoconductive to photodiode behavior once the illumination wavelength is in the below-band-gap regime. The device exhibits a very low dark current of 0.85 pA at zero bias. In the selfpowered mode with low-light conditions (∼0.38 μW/cm 2 ) at 360 nm illumination, the light-to-dark current (I Light /I Dark ) ratio, responsivity (R λ ), specific detectivity (D*), and external quantum efficiency (EQE) of the fabricated PD were calculated to be ∼1 × 10 4 , 0.22 A/W, 1.486 × 10 14 Jones (cm Hz 1/2 W −1 ), and 77%, respectively. The response and recovery time of the PD were typically 485 and 886 μs, respectively under 280 Hz light switching frequency at zero bias. The device also shows significant photoconductive response with a typical persistent photoconductivity behavior at an applied bias of 5 V with extremely large I Light /I Dark ratio of ∼10 7 at 360 nm (∼0.15 mW/cm 2 ). The R λ , D*, and EQE were found to be 529 A/W, 4.25 × 10 16 Jones, and ∼2 × 10 5 %, respectively, for 360 nm illumination under low-light conditions (∼0.38 μW/cm 2 ), at 5 V applied bias. The extraordinary performance of the device in both photovoltaic and photoconductive modes makes r-GO/GaN heterojunction scheme suitable for dual-mode low-light UV−visible applications.

materials to form heterostructures due to the improved functionality of electronic and optoelectronic devices. [1][2][3][4][5][6] The 2D material-based devices can have a revolutionizing impact on technology covering from vacuum photodetection and photovoltaics to optical modulators and high speed data communication. [7][8][9][10][11][12][13][14][15][16] Predominantly through vertical transport of photogenerated carriers, the hybrid structures allow us to overcome the inherent persistent photoconductivity (PPC), where photocurrent of the host material generally persists for a long duration even after the illumination is removed, generally observed in the compound III-nitride semiconductor materials. [17][18][19][20][21] Usually PPC occurs due to the presence of donor and acceptor states closer to the conduction band minimum (CBM) and valence band maximum (VBM), which provides a large number of electron and hole trap states in the host material, respectively. Alternatively, with an introduction of intrinsic semiconductor materials, the PPC could be reduced as the donor and acceptor states show a shift from the CBM and VBM edges toward the midgap positions, which facilitate fast recombination time in comparison to the transit time of photo generated carriers through host materials. This has resulted in high speed operation in photoconductive mode. [22] In particular, GaN integrated with reduced-graphene oxide (r-GO) is a promising heterostructure for achieving improved device characteristics such as low dark current, high spectral responsivity, and high response speed. [17] 2D r-GO makes an optically active heterojunction with GaN. The emphasis so far has been given on r-GO/GaN heterostructure operating in the photovoltaic mode where the photogenerated carriers are swiftly swept across the depletion region predominantly via vertical transport. However, in the photoconductive mode operation, where the photogenerated carriers traverse across the host materials under the influence of an external bias exceeding the built-in-field of the heterostructure device, suffers either from high leakage current and/or PPC due to inherently negatively charged defects rich GaN. [23] The intentional/unintentional doping of suitable species can cause compensation of free New generation of hybrid photodetectors may provide the optimal solution for compact, highly sensitive, durable, and reliable broadband ultraviolet (BUV) sensors. A high-performance dual-mode BUV photodetector based on melding of highly resistive GaN and reduced graphene oxide is reported. Under zero bias, the device exhibits a sub-picoampere dark current, high light-to-dark current (I Light /I Dark ) ratio of ≈3.8 × 10 3 and high BUV-visible rejection ratio (≈1.8 × 10 2 ) with fast rise and fall times. The photodetector displays remarkable stability when subject to extreme operating conditions. The photoresponse of the detector shows a dark current of ≈2.41 nA at ± 200 V bias, I Light /I Dark ratio of ≈200 and high BUV-vis rejection ratio (≈7 × 10 2 ). The response ...

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Though tetanus is an old disease with well known medicines, its complications are still a serious issue worldwide. Tetanus is mainly due to a powerful neurotoxin, tetanolysin-O, produced by a Gram positive anaerobic bacterium, Clostridium tetani. The toxin has a thiol-activated cytolysin which causes lysis of human platelets, lysosomes and a variety of subcellular membranes. The existing therapy seems to have challenged as available vaccines are not so effective and the bacteria developed resistance to many drugs. Computer aided approach is a novel platform to screen drug targets and design potential inhibitors. The three dimensional structure of the toxin is essential for structure based drug design. But the structure of tetanolysin-O is not available in its native form. Moreover, the interaction and pharmacological activities of current drugs against tetanolysin-O is not clear. Hence, there is need for three dimensional model of the toxin. The model was generated by homology modeling using crystal structure of perfringolysin-O, chain-A (PDB ID: 1PFO) as the template. The modeled structure has 22.7% α helices, 27.51% β sheets and 41.75% random coils. A thiol-activated cytolysin was predicted in the region of 105 to 1579, which acts as a functional domain of the toxin. The hypothetical model showed the backbone root mean square deviation (RMSD) value of 0.6 Å and the model was validated by ProCheck. The Ramachandran plot of the model accounts for 92.3% residues in the most allowed region. The model was further refined by various tools and deposited to Protein Model Database (PMDB ID: PM0077550). The model was used as the drug target and the interaction of various lead molecules with protein was studied by molecular docking. We have selected phytoligands based on literatures and pharmacophoric studies. The efficiency of herbal compounds and chemical leads was compared. Our study concluded that herbal derivatives such as berberine (7, 8, 13, 13a-tetradehydro-9,10-dimethoxy-2,3 [methylenebis(oxy)] berbinium), curcumin ((1E,6E)-1,7-bis (4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione), coumarin (2H-chromen-2-one), catechol (Benzene-1,2-diol) and diosphenol (2-hydroxy-3-methyl-6-propan-2-ylcyclohex-2-en-1-one) are the best inhibitors compared to known chemicals. Hence, these leads can be used as potential inhibitors against tetanolysin.