Antibiotics-based effluents pose a severe threat to the natural ecosystem by acting as reservoirs for the growth of drug-resistant bacteria if untreated. Herein, a facile and scalable approach was developed to engineer photocatalysts associating reduced graphene oxide (rGO) and molybdenum disulfide (rGO@MoS2) that were used for the degradation of chloramphenicol (CAP) from contaminated water under UV-light. The hydrothermally produced rGO@MoS2 catalysts contain CO, COH, and COC functional groups that contribute to the binding of CAP onto their surface. The rGO surface modification with MoS2 layers offers a high surface area for light absorption. Results show that the rGO@MoS2 catalyst (1:1 w/w) exhibits the highest degradation efficiency (DE) of 86 % within 180 min of light exposure at neutral pH. Further, the kinetic modelling studies for CAP degradation by rGO@MoS2 1:1 showed high linearity with pseudo-first order kinetics (R-2 similar to 0.9). The isotherm modelling studies correspond to Langmuir isotherm (R-2 similar to 0.99), suggesting monolayer-type interaction of CAP with the photocatalyst surface during photodegradation. Furthermore, the mechanism of degradation elucidated using scavenging experiments showed the involvement of both holes (h(+)) and electrons (e(-)) that contribute to the degradation of CAP by generating reactive oxygen species (ROS) like OH center dot and O-2(center dot-) radicals. The applicability of the rGO@MoS2 photocatalyst towards the degradation of CAP was tested in Ganga water, wherein a similar similar to 86 % CAP removal was observed. Furthermore, the photocatalyst was found to be stable and could be reused five times. Overall, these findings demonstrate the usefulness of the rGO@MoS2 1:1 composite as an efficient photocatalyst that can be used for the degradation of harmful organic pollutants from water bodies to provide a safer and cleaner environment.

Red-emitting phosphors are essential to achieve sustainable white-light-emitting diodes (WLEDs) for lighting and indoor plant growth. Materials with negative thermal expansion (NTE) can overcome the critical problem of the thermal quenching (TQ) of photoluminescence (PL). In this regard, we report a Sc2Mo3O12:Sm3+ (SMO:Sm3+) reddish-orange emitting phosphor with no TQ up to 433 K. The intense charge transfer from the SMO matrix to the dopant (O2- -> Sm3+) reinforced the absorption of ultraviolet (UV) light, in addition to intra 4f-4f blue light excitation. The site occupation of Sm3+ was investigated using extended X-ray absorption fine structure (EXAFS) spectroscopy, and X-ray absorption near edge structure (XANES) spectroscopy ruled out any contribution of Sm2+ in the PL process. Temperature-dependent XRD studies revealed strong NTE in SMO, which induced promising anti-TQ performance via intensifying the charge transfer absorption and improved structural rigidity. As a result, 591% of its intensity at room temperature was retained at 433 K resulting in a similar to 6-fold enhancement in Sm3+ emission. Moreover, we demonstrated two prototypes for lighting and indoor plant growth by fabricating the SMO:Sm3+ phosphor onto UV (280 nm) and 410 nm LED chips, respectively. The WLED offers a high color rendering index (CRI) of 84, CIE (0.33, 0.32), and correlated color temperature (CCT) of 5408 K, with a high luminous efficacy of 113 lm W-1. The LED emission bands overlap with the absorption of phytochrome, P-R, which is essential for plant growth. We further investigated the temperature-dependent cryogenic PL properties and its correlation with phase transition. These findings revealed that the lattice phase transition has minimal impact on the Sm3+ local structure and its luminescence profile. Interestingly, we discovered the green emission of the monoclinic SMO phase at liquid nitrogen temperature (-193 degrees C). The MoO42- emission diminished on phase transition from monoclinic to orthorhombic SMO at room temperature. Our results demonstrate the potential of SMO:Sm3+ phosphors for applications in lighting and indoor plant growth LEDs with anti-TQ properties.

In-sensor and near-sensor computing architectures enable multiply accumulate operations to be carried out directly at the point of sensing. In-sensor architectures offer dramatic power and speed improvements over traditional von Neumann architectures by eliminating multiple analog-to-digital conversions, data storage, and data movement operations. Current in-sensor processing approaches rely on tunable sensors or additional weighting elements to perform linear functions such as multiply accumulate operations as the sensor acquires data. This work implements in-sensor computing with an oscillatory retinal neuron device that converts incident optical signals into voltage oscillations. A computing scheme is introduced based on the frequency shift of coupled oscillators that enables parallel, frequency multiplexed, nonlinear operations on the inputs. An experimentally implemented 3 × 3 focal plane array of coupled neurons shows that functions approximating edge detection, thresholding, and segmentation occur in parallel. An example of inference on handwritten digits from the MNIST database is also experimentally demonstrated with a 3 × 3 array of coupled neurons feeding into a single hidden layer neural network, approximating a liquid-state machine. Finally, the equivalent energy consumption to carry out image processing operations, including peripherals such as the Fourier transform circuits, is projected to be <20 fJ/OP, possibly reaching as low as 15 aJ/OP.

The application of negative electron affinity (NEA) photocathodes as high-frequency and high external quantum efficiency electron emission sources has gained attention due to their potential benefits in various fields, including but not limited to electronics, materials science, and microscopy. NEA photocathodes have been achieved by depositing a Cs/O surface layer on GaAs or other semiconductors [1], [2]. These devices have limited stability and require ultra-high vacuum, cluster tools for deposition and short lifetimes. To overcome these limitations, this work proposes the use of a silicon-insulator-graphene structure, Hot Electron Laser Assisted Cathode (HELAC), which is electronically tunable, air-stable, and can mimic a NEA surface under certain bias conditions. The devices explored here have exhibited an emission current of $\sim 20\mu \mathrm{A}$ under red light illumination, corresponding to a current density of 3.2 A/m 2 and an external quantum efficiency (EQE) of 0.2%. In this paper, we have described the semiconductor device physics of this device and identified approaches to improve the photocathode performance.

State-of-the art negative electron affinity cathodes are being considered as promising high-frequency photoemitters because of their reasonably high external quantum efficiency and low mean transverse energies. However, their large-scale application is still limited by their instability and complex fabrication process. In this work, we have designed and fabricated an electronically tunable hot electron laser assisted cathode using negative electron surfaces by employing a facile exsitu fabrication technique. Despite the lack of any optimization, the proof-of-concept device has demonstrated excellent air stability and an external quantum efficiency of ~0.5%. This study can provide insight into the prospects and challenges of designing novel negative electron affinity photocathodes with high quantum efficiency.

Nonlinear optical organic molecules have advanced a wide range of fields spanning from integrated photonics to biological imaging. With advances in molecular design, an emerging application is multifunctional nonlinear organic materials. Unlike conventional molecules which simply emit light through single or multi photon processes, multifunctional materials can perform multiple tasks, such as modulating the optical signal or reporting an electric field intensity. In this work, we report a multifunctional organic molecular device with electric field 'sense-and-modulate' capability. This is achieved by combining two distinct functional modules. The electric field-reporting module relies on a photo-induced electron transfer (PeT) dye, tetraphenylethylene (TPE) as a two-photon (2p) imaging agent; while the electric field-modulating module relies on the organic photoconductor, naphthalimide (NAI). To reduce cross-talk between the two modules, they are separated by a long alkyl chain. The photophysical properties and photoconductivity of the probe molecule are studied in a range of solvents and in the solid state, and the results agree with the density functional theory predictions. Specifically, 2p excitation is demonstrated, and the photoconductivity is rapid and reversible. The entire system is optically controlled, including signal read-out, and the two modules can be operated simultaneously or individually.

Hydrothermal incorporation of an MoS2 nanosheet onto ternary metal sulfide enhances the specific capacitance resulting in an asymmetric supercapacitor (CuCo2S4–MoS2//AC) with ultra-high energy density and power density as well as wide potential window.

Lead-free metal halide perovskites have attracted great attention as light harvesters due to their promising optoelectronic and photovoltaic properties. In this investigation, we have successfully synthesized thermally stable cubic phase cesium tin chloride (CsSnCl3) perovskite nanocrystals with improved surface morphology by adopting a rapid hot-injection technique. The excellent crystalline quality of these cubic shaped nanocrystals was confirmed by high-resolution transmission electron microscopy imaging. The binding of organic ligands on the surface of the sample was identified and characterized using nuclear magnetic resonance spectroscopy. UV-visible spectroscopy confirmed that the CsSnCl3 nanocrystals have a direct band gap of ∼2.98 eV, which was further confirmed using steady-state photoluminescence spectroscopy. The band edge positions calculated using the Mulliken electronegativity approach predicted the potential photocatalytic capability of the as-prepared nanocrystals, which was then experimentally corroborated through the photodegradation of rhodamine-B dye under both visible and UV-visible irradiation. Our theoretical calculations employing experimentally obtained structural parameters within the generalized gradient approximation (GGA) and GGA+U methods demonstrated a 90% accurate estimation of the experimentally observed optical band gap when Ueff = 6 eV was considered. The ratio of the effective mass of the hole and electron expressed as was also calculated for Ueff = 6 eV. Based on this theoretical calculation and experimental observation of the photocatalytic performance of CsSnCl3 nanocrystals, we have proposed a rational interpretation of the "D" value. We think that a "D" value of either much smaller or much larger than 1 is an indication of the low recombination rate of the photogenerated electron-hole pairs and the high photocatalytic efficiency of the photocatalyst. We believe that this comprehensive investigation might be helpful for the large-scale synthesis of thermally stable cubic CsSnCl3 nanocrystals and also for a greater understanding of their potential in photocatalytic, photovoltaic and other prominent optoelectronic applications.

Fabrication of heterogeneous photocatalysts has received increasing research interest due to their potential applications for the degradation of organic pollutants in wastewater and evolution of carbon-free hydrogen fuel via water splitting. Here, we report the photodegradation and photocatalytic hydrogen generation abilities of nanostructured LaFeO3-MoS2 photocatalyst synthesized by facile hydrothermal technique. Prior to conducting photocatalytic experiments, structural, morphological and optical properties of the nanocomposite were extensively investigated using X-ray diffraction analysis, field emission scanning electron microscopy and UV-visible spectroscopy, respectively. Nanostructured LaFeO3-MoS2 photodegraded similar to 96% of rhodamine B dye within only 150 minutes which is considerably higher than that of LaFeO3 and commercial Degussa P25 titania nanoparticles. The LaFeO3-MoS2 nanocomposite also exhibited significantly enhanced photocatalytic efficiency in the decomposition of a colorless probe pollutant, ciprofloxacin eliminating the possibility of the dye-sensitization effect. Moreover, LaFeO3-MoS2 demonstrated superior photocatalytic activity towards solar hydrogen evolution via water splitting. Considering the band structures and contribution of reactive species, a direct Z-scheme photocatalytic mechanism is proposed to rationalize the superior photocatalytic behavior of LaFeO3-MoS2 nanocomposite.

Lead-free double perovskites are overtaking single perovskites as solar harvesting materials due to their superior stability, excellent catalytic efficiency and minimal toxicity. In this investigation, we have synthesized double perovskite Gd2FeCrO6 (GFCO) nanoparticles for the first time via a facile sol-gel technique to investigate their structural, magnetic and optical properties. The double perovskite GFCO crystallized in monoclinic structure with P2(1)/n space group. The Fe/Cr-O bond length was calculated as similar to 1.95 angstrom from the Raman spectrum which was consistent with the value, similar to 1.99 angstrom obtained from X-ray diffraction analysis. The average size of the nanoparticles was determined to be similar to 70 nm by both field emission scanning electron microscopy and transmission electron microscopy. The existence of mixed valence states of Fe and Cr was confirmed by X-ray photoelectron spectroscopy. The zero field cooled (ZFC) and field cooled (FC) curves largely diverged below 20 K. A downturn was observed in the ZFC curve at 15 K which corresponds to an antiferromagnetic, Neel transition. The narrow magnetic hysteresis loop recorded at 5 K was nearly saturated and demonstrated an asymmetric shift along the magnetic field axis indicating the concurrence of ferromagnetic and antiferromagnetic domains in GFCO nanoparticles. The UV-visible and photoluminescence spectroscopic analyses unveiled the semiconducting nature of nanostructured GFCO with an optical band gap of 2.0 eV. The as-synthesized thermally stable lead-free GFCO semiconductor might be a potential perovskite material to be employed in photocatalytic and related solar energy applications due to its ability to absorb the visible spectrum of the solar light. (C) 2021 Elsevier B.V. All rights reserved.

We have synthesized Gd$_{2}$FeCrO$_{6}$ (GFCO) double perovskite which is crystallized in a monoclinic structure with P2$_{1}/$n space group. The UV-visible and photoluminescence spectroscopic analyses confirmed its direct bandgap semiconducting nature. Employing experimentally obtained structural parameters in first-principles calculation, we report the spin-polarized electronic band structure, charge carrier effective mass, density of states, electronic charge density distribution and optical absorption property of the GFCO double perovskite. The effects of on-site d-d Coulomb interaction energy (U$_{eff}$) on the electronic and optical properties were investigated by applying a range of Hubbard U$_{eff}$ parameters from 0 to 6 eV to the Fe-3d and Cr-3d orbitals within the generalized gradient approximation (GGA) and GGA+U methods. When we applied U$_{eff}$ in the range of 1 to 5 eV, both the up-spin and down-spin band structures were observed to be direct. The charge carrier effective masses were also found to enhance gradually from U$_{eff} =$ 1 eV to 5 eV, but, these values were anomalous for U$_{eff} =$ 0 and 6 eV. These results suggest that U$_{eff}$ should be limited within the range of 1 to 5 eV to calculate the structural, electronic and optical properties of GFCO double perovskite. We observed that considering U$_{eff} =$ 3 eV, the theoretically calculated optical band gap 1.99 eV matched well with the experimentally obtained value 2.0 eV. The outcomes of our finding imply that the U$_{eff}$ value of 3 eV most accurately localized the Fe-3d and Cr-3d orbitals of GFCO keeping the effect of self-interaction error from the other orbitals almost negligible. Therefore, we may recommend U$_{eff} =$ 3 eV for first-principles calculation of the electronic and optical properties of GFCO double perovskite that might have potential in photocatalytic and related solar energy applications.

We report the effect of temperature on the crystallographic structure and magnetic properties of ultrasonically prepared nanostructured Nd0.7Sr0.3MnO3 perovskite manganite. The crystal structure of as-synthesized nanoparticles remains unaltered over a wide scanning temperature range. Temperature dependent magnetization measurements demonstrate that the Curie temperature (Tc) of Nd0.7Sr0.3MnO3 nanoparticles is in the range of 211 K–220 K under largely varying applied magnetic fields. Below Tc, the soft ferromagnetic nature of these nanoparticles is confirmed by the field-dependent magnetization measurements. The absence of the charge-ordered state is also revealed in this nanomanganite down to 20 K, which is strikingly different from analogous Nd–Sr based nanocrystals. The experimentally observed effective paramagnetic moment and saturation magnetic moment have matched quite well with the values calculated theoretically. The Tc values up to a temperature of 220 K, nearly perfect ferromagnetically ordered Mn ions below Tc, high saturation magnetization, and magnetic softness of synthesized nanostructured Nd0.7Sr0.3MnO3 manganite can be associated with their good crystallinity as well as the nominal internal and surface disorder effect owing to intermediate particle size (∼75 nm to 150 nm). Our investigation elucidates the promising potential of nanocrystalline Nd0.7Sr0.3MnO3 particles for numerous technological applications.

We have synthesized MoS2 incorporated α-Fe2O3/ZnO nanocomposites by adapting a facile hydrothermal synthesis process. The effect of incorporating ultrasonically exfoliated few-layer MoS2 nanosheets on the solar-light driven photocatalytic performance of α-Fe2O3/ZnO photocatalyst nanocomposites has been demonstrated. Structural, morphological and optical characteristics of the as-synthesized nanomaterials are comprehensively investigated and analyzed by performing Rietveld refinement of powder X-ray diffraction patterns, field emission scanning electron microscopy and UV-visible spectroscopy, respectively. The photoluminescence spectra of the as-prepared nanocomposites elucidate that the recombination of photogenerated electron-hole pairs is highly suppressed due to incorporation of MoS2 nanosheets. Notably, the ultrasonicated MoS2 incorporated α-Fe2O3/ZnO nanocomposite manifests 91% and 83% efficiency in degradation of rhodamine B dye and antibiotic ciprofloxacin respectively under solar illumination. Active species trapping experiments reveal that the hydroxyl (˙OH) radicals play a significant role in RhB degradation. Likewise the dye degradation efficiency, the amount of hydrogen produced by this nanocomposite via photocatalytic water splitting is also considerably higher as compared to both non-ultrasonicated MoS2 incorporated α-Fe2O3/ZnO and α-Fe2O3/ZnO nanocomposites as well as Degussa P25 titania nanoparticles. This indicates the promising potential of the incorporation of ultrasonicated MoS2 with α-Fe2O3/ZnO nanocomposites for the generation of carbon-free hydrogen by water splitting. The substantial increase in the photocatalytic efficiency of α-Fe2O3/ZnO after incorporation of ultrasonicated MoS2 can be attributed to its favorable band structure, large surface to volume ratio, effective segregation and migration of photogenerated electron-hole pairs at the interface of heterojunctions and the plethora of exposed active edge sites provided by the few-layer MoS2 nanosheets.

Bulk polycrystalline samples of Gd-doped La2-xGdxSrMn2O7 (x = 0.3, 0.6) double-layered perovskite manganites were synthesized in air by conventional solid-state reaction and then annealed at 600 degrees C in inert (N-2) atmosphere. Rietveld refined powder X-ray diffraction patterns show impurity peaks for samples synthesized in air, whereas annealing completely removes the undesired peaks in the lightly doped (15% Gd) sample and partially removes them in the heavily doped (30% Gd) sample. The morphology was improved in both samples due to annealing. Magnetic hysteresis loops demonstrate enhanced magnetic softness for the lightly doped manganite. Its saturation magnetization at room temperature at 10 kOe is 50 emu/g, and is increased to 53 emu/g after heat treatment. Heat treatment also decreases its coercive field and remanent magnetization. These properties indicate that 15% Gd-doped La(1.7)Gd(0.3)SrMn(2)O(7 )manganite may be used in applications where magnetic softness is desired.

We have demonstrated a facile one-step ultrasound driven exfoliation technique for the synthesis of few-layer MoS2 nanosheets from bulk MoS2 powder with a yield of almost 60%. Structural, morphological and optical characterizations of non-ultrasonicated and ultrasonicated MoS2 are carried out in nominally identical conditions to make a direct comparison between their properties. The Rietveld refined powder x-ray diffraction patterns elucidate the semiconducting 2 H phase of MoS2 nanosheets without any structural deformation caused by ultrasonication. Field emission scanning electron microscopy ensures the successful formation of ultrathin MoS2 nanosheets having thickness in the range of 8–15 nm. The ultrasonicated MoS2 nanosheets demonstrate considerably higher absorbance in the visible spectra compared to their non-ultrasonicated counterpart. A slight enhancement is observed in the optical indirect bandgap of exfoliated MoS2 nanosheets which is further confirmed by first-principles calculations. The photoluminescence spectroscopy reveals the enhanced potential of ultrasonicated MoS2 to suppress photogenerated carrier recombination phenomenon. The ultrasonicated MoS2 manifests considerably better performance in photocatalytic degradation of rhodamine B (RhB) dye under visible light irradiation as compared to non-ultrasonicated MoS2. Further, addition of H2O2 in the solution has enabled ultrasonicated MoS2 nanosheets to photodegrade 100% of RhB dye within only 1 h and 40 min. The outcome of our investigation suggests that this ultrasound assisted exfoliation technique can be effectively employed as a rapid and efficient route for the large-scale synthesis of few-layer ultrathin MoS2 nanosheets with superior photocatalytic performance. The synthesized MoS2 nanosheets may further lead to engineering heterogeneous structures of different photocatalysts having promising potential for numerous applications.

In recent years Eye gaze tracking (EGT) has emerged as an attractive alternative to conventional communication modes. Gaze estimation can be effectively used in human-computer interaction, assistive devices for motor-disabled persons, autonomous robot control systems, safe car driving, diagnosis of diseases and even in human sentiment assessment. Implementation in any of these areas however mostly depends on the efficiency of detection algorithm along with usability and robustness of detection process. In this context we have proposed a Convolutional Neural Network (CNN) architecture to estimate the eye gaze direction from detected eyes which outperforms all other state of the art results for Eye-Chimera dataset. The overall accuracies are 90.21% and 99.19% for Eye-Chimera and HPEG datasets respectively. This paper also introduces a new dataset EGDC for which proposed algorithm finds 86.93% accuracy. We have developed a real-time eye gaze controlled robotic car as a prototype for possible implementations of our algorithm.