In this study, we have established an efficient method to develop a solution-processed ultraviolet (UV) sensor with easy fabrication, a high response, and cost-effectiveness. Aiming at this, we developed a platform to utilize the synergistic effect of a hybrid network comprising a conducting polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and inorganic and organic UV sensitive materials, titanium dioxide (TiO2) nanoparticles and carbon quantum dots (CQDs):TiO2 nanocomposites, respectively. With the addition of the organic solvent dimethyl sulfoxide (DMSO) to the nanocomposites, the structural architecture of the hybrid film was altered, leading to the enhancement of the overall responsivity and conductivity of the sensor. The structural modifications in the hybrid film were confirmed through Raman spectroscopy, whereby peak shifts were detected. The hybrid film was fabricated on the silicon wafer (p-type) by using a simple drop-cast technique. Upon the illumination of UV radiation on the hybrid film, the change in conductivity was measured for light and dark modes. The proposed sensors demonstrated responsivity of 48.6% and response and recovery times of 235 and 360 s, respectively, for UV on/off cycles, which was substantially greater than that of the pristine PEDOT:PSS films, whose responsivity was 7.27% and response and recovery times of 753 and 856 s, respectively. The proposed sensor can be used in UV sensing applications for the detection of skin cancer, premature aging, and several other UV-induced skin ailments.

Atomic scale crystallographic structures of a quantum crystals depend on substrate, interfacial strain, defects, surface functionalities etc., which make it challenging to precisely control. To achieve high quality material, UHV conditions are prerequisite, which makes it costly. Naturally occurring 2D materials have tremendous significance in this regard. White lead, having weak interlayer coupling and easily found in natural ores have never been exfoliated. Keeping the novelty in mind, one needs to explore its physical as well as chemical behaviour and look out for appropriate applications. We for the first time, therefore, have sonochemically exfoliated white lead, and established its physical and chemical behaviour. We have also blended it with graphene oxide and explored its gas sensing applications and found the hybrid system to be very selective for NH 3 gas. White lead, a naturally occurring 2D material; has been exfoliated for the first time and its hybrid with graphene oxide has been explored for gas sensing. Graphical abstract White lead, a naturally occurring 2D material; has been exfoliated for the first time and its hybrid with graphene oxide has been explored for gas sensing.

Quantum flatland i.e., the family of two dimensional (2D) quantum materials has become increscent and has already encompassed elemental atomic sheets (Xenes), 2D transition metal dichalcogenides (TMDCs), 2D metal nitrides/carbides/carbonitrides (MXenes), 2D metal oxides, 2D metal phosphides, 2D metal halides, 2D mixed oxides, etc. and still new members are being explored. Owing to the occurrence of various structural phases of each 2D material and each exhibiting a unique electronic structure; bestows distinct physical and chemical properties. In the early years, world record electronic mobility and fractional quantum Hall effect of graphene attracted attention. Thanks to excellent electronic mobility, and extreme sensitivity of their electronic structures towards the adjacent environment, 2D materials have been employed as various ultrafast precision sensors such as gas/fire/light/strain sensors and in trace-level molecular detectors and disease diagnosis. 2D materials, their doped versions, and their hetero layers and hybrids have been successfully employed in electronic/photonic/optoelectronic/spintronic and straintronic chips. In recent times, quantum behavior such as the existence of a superconducting phase in moiré hetero layers, the feasibility of hyperbolic photonic metamaterials, mechanical metamaterials with negative Poisson ratio, and potential usage in second/third harmonic generation and electromagnetic shields, etc. have raised the expectations further. High surface area, excellent young's moduli, and anchoring/coupling capability bolster hopes for their usage as nanofillers in polymers, glass, and soft metals. Even though lab-scale demonstrations have been showcased, large-scale applications such as solar cells, LEDs, flat panel displays, hybrid energy storage, catalysis (including water splitting and CO2 reduction), etc. will catch up. While new members of the flatland family will be invented, new methods of large-scale synthesis of defect-free crystals will be explored and novel applications will emerge, it is expected. Achieving a high level of in-plane doping in 2D materials without adding defects is a challenge to work on. Development of understanding of inter-layer coupling and its effects on electron injection/excited state electron transfer at the 2D-2D interfaces will lead to future generation heterolayer devices and sensors.

Miniaturized heterolayered flexible functional chips are essential part of electronic/excitonic/spintronic/renewable energy devices. Pivotal to functional devices consisting of van der Waal stacks is the synergy amongst constituent layers, however, the current techniques such as sequential CVD growth, direct micromechanical transfer or wet chemical transfer are mostly limited due to imperfect interfaces, as results of atomic diffusion, or metallic remnants and bubbles at the interface. Realization of out-of-plane chemical bonding between 2D heterolayers would result in new class of materials i.e. 2+δ dimensional materials which would be significantly suitable for out-of-plane carrier transport and hence prompt response in prospective devices. Here we report our discovery of the use of extreme electric field at the focal hot-spot during microwave reaction and exotic thermomechanical conditions during the solvothermal reaction to synthesize 2+δ dimensional materials. We found the interlayer distance reduces with the increase in electric field in microwave treatment and effective pressure in solvothermal treatment. When inter-layer distance matches with the theoretical equilibrium inter-layer distance, chemical bond forms. We found that pz-pz chemical bonds e.g. C-B and C-N in G-BN case, Mo-N, and Mo-B in MoS2-BN case between component layers were evidenced via X-ray photoelectron spectroscopy. New vibrational peaks in Raman spectra (~1320 cm-1 for the G-BN system and ~365 cm-1 for the MoS2-BN system) have been recorded. We also observed tunable mid-gap formation, along with diodic (knee voltage ~0.7 V, breakdown voltage ~1.8 V) interface in RGO-RBNO system, band gap engineering. In MoS2-BN system, after the processing, the effective band gap was turned to be 2.7 eV at equilibrium distance of 3.3 Å and 2.9 eV at 2.7 Å, indicating the formation of 1T metallic phase due to exotic conditions of processing. Simulation hints at stacking dependent interfacial charge and potential drops. We anticipate our strategy for 2+δ dimensional materials to be a starting point for heterostructures in many nanomaterials-based devices and emerging applications.

Borophene, the lightest among all Xenes, possesses extreme electronic mobility along with high carrier density and high Young's modulus. To accomplish device-quality borophene, novel approaches of realization of monolayers need to be urgently explored. In this work, micromechanical exfoliation is discovered to result in mono- and few-layered borophene of device quality. Borophene sheets are successfully fabricated down to monolayer thickness. Distinct crystallographic phases of borophene viz. XRD study reveals crystallographic phase transition from rhombohedral to several other eigen phases of borophene. The role of the destination substrates is held crucial in determining the final phase of the transferred sheet. The exfoliation energy is calculated by density functional theory. Molecular dynamics simulations are used to simulate the exfoliation process. Heterolayers of borophene, with black phosphorene (BP) or with molybdenum disulfide (MoS2 ) atomic sheets, are found to result in photoexcited coupling quantum states. Gold-coated borophene bestows promising anchoring capability for surface-enhanced Raman spectroscopy (SERS). Successful demonstration of the electronic behavior of micromechanically exfoliated borophene and excitonic behavior of borophene-based heterolayers will guide future generation devices not only in electronics and excitonics, but also in thermal management, electronic packaging, hydrogen storage, hybrid energy storage, and clean energy solutions.

Worldwide infections and fatalities caused by the SARS-CoV-2 virus and its variants responsible for COVID-19 have significantly impeded the economic growth of many nations. People in many nations have lost their livelihoods, it has severely impacted international relations and, most importantly, health infrastructures across the world have been tormented. This pandemic has already left footprints on human psychology, traits, and priorities and is certainly going to lead towards a new world order in the future. As always, science and technology have come to the rescue of the human race. The prevention of infection by instant and repeated cleaning of surfaces that are most likely to be touched in daily life and sanitization drives using medically prescribed sanitizers and UV irradiation of textiles are the first steps to breaking the chain of transmission. However, the real challenge is to develop and uplift medical infrastructure, such as diagnostic tools capable of prompt diagnosis and instant and economic medical treatment that is available to the masses. Two-dimensional (2D) materials, such as graphene, are atomic sheets that have been in the news for quite some time due to their unprecedented electronic mobilities, high thermal conductivity, appreciable thermal stability, excellent anchoring capabilities, optical transparency, mechanical flexibility, and a unique capability to integrate with arbitrary surfaces. These attributes of 2D materials make them lucrative for use as an active material platform for authentic and prompt (within minutes) disease diagnosis via electrical or optical diagnostic tools or via electrochemical diagnosis. We present the opportunities provided by 2D materials as a platform for SARS-CoV-2 diagnosis.

This paper presents the development of spring supported based single-axis MEMS capacitive accelerometer. The accelerometer is based on the transverse axis capacitance sensing, and the study has been carried out to determine the effects on the structure resonance frequency, proof mass displacements, and change is capacitance if the number of spring fold increases. COMSOL (version 5.1) multiphysics software, the MEMS capacitive accelerometer is designed to approximate its dynamic characteristics and is simulated in the finite element domain. Basically, the detection of displacement, acceleration, and acceleration producing force is done by the help of an extremely tinny micro meter device attached with comb structures.

Even though transition metal dichalcogenides (TMDCs) are deemed to be novel photonic and optoelectronic 2D materials, the visible band gap being often limited to monolayer, hampers their potential in niche applications due to fabrication challenges. Uncontrollable defects and degraded functionalities at elevated temperature and under extreme environments further restrict their prospects. To address such limitations, the discovery of a new 2D material, α-PbO is reported. Micromechanical as well as sonochemical exfoliation of 2D atomic sheets of α-PbO are demonstrated and its optical behavior is investigated. Spectroscopic investigations indicate layer dependent band gaps. In particular, even multilayered PbO sheets exhibit visible band gap > 2 eV (direct) which is rare among semiconducting 2D materials. The emission lifetime of multilayer PbO atomic sheets is 7 ns (dim light) as compared to the monolayer which gives 2.5 ns lifetime and an intense light. Density functional theory calculations of layer dependent band structure of α-PbO matches well with experimental results. Experimental findings suggest that PbO atomic sheets exhibit hydrophobic nature, thermal robustness, microwave stability, anti-corrosive behaviour and acid resistance. This new low-cost, abundant and robust 2D material is expected to find many applications in the fields of electronics, optoelectronics, sensors, photocatalysis and energy storage.

The role of defects on laser-excited photoluminescence of various ZnO nanostructures has been investigated. The study shows that defects present in ZnO nanostructures, specially Zn-related defects play a crucial role in determining the laser-excited photoluminescence intensity (LEI). ZnO nanoparticles as well as nanorods (NR) annealed in oxygen atmosphere exhibit remarkable enhancement in LEI. A similar enhancement is also shown by Al-doped ZnO NR.

Nanomechanical properties of indium nanowires like structures fabricated on quartz substrate by trench template technique, measured using nanoindentation. The hardness and elastic modulus of wires were measured and compared with the values of indium thin film. Displacement burst observed while indenting the nanowire. 'Wire-only hardness' obtained using Korsunsky model from composite hardness. Nanowires have exhibited almost same modulus as indium thin film but considerable changes were observed in hardness value.

DC electric-field mediated nanocrystallization of thermally evaporated silicon thin films with nickel as seed/cap layer has been attempted in complete absence of any external heat input. When 60 nm Si thin film coated onto 5 nm Ni thin film was treated by a direct current (DC) electric field (up to 3.3 kV/cm up to 5 minutes) after the deposition, amorphous silicon thin films became nanocrystalline (6–10 nm). Silicon nanograins (average diameter 90 nm) grow to larger sizes (average diameter 240 nm) with sharpening of grain size distribution. Huge grain growth (4-fold increase) has been observed when nickel was used as cap layer (5 nm Ni/60 nm Si). XRD data show the signature of nickel silicide formation on the surface in nickel cap layer case. Field treatment has changed the optical absorption edge (shifts left in nm units) and the refractive index of silicon thin film when nickel was used as under layer, and an almost negligible effect on the optical properties has been observed when nickel was used as cap layer.

Surfaces of single crystal [311] silicon, germanium and GaAs were nanostructured by a DC electric field (0.1-1.5 kV/cm). Spark threshold was found to be 1.33, 0.66 and 0.33 kV/cm for GaAs, silicon and germanium, respectively. Field nanostructuring results in the formation of nanoparticles of grain size in the range of 30-200 nm showed the nanoparticle size increasing with the increase in field value. Electric field treatment of the silicon surface gives rise to a lack of long-range crystalline order for surfaces. The effect of such a nanostructuring process is to make more absorbing and surface-oxidised nanocrystalline photoluminescent surfaces. Electric field treatment gives rise to local and directional nanostructuring.

Excimer laser irradiation at ambient temperature has been employed to produce nanostructured silicon surfaces. Nanoindentation was used to investigate the nanomechanical properties of the deformed surfaces as a function of laser parameters, such as the angle of incidence and number of laser pulses at a fixed laser fluence of 5 J cm-2. A single-crystal silicon [311] surface was severely damaged by laser irradiation and became nanocrystalline with an enhanced porosity. The resulting laser-treated surface consisted of nanometer-sized particles. The pore size was controlled by adjusting the angle of incidence and the number of laser pulses, and varied from nanometers to microns. The extent of nanocrystallinity was large for the surfaces irradiated at a small angle of incidence and by a high number of pulses, as confirmed by x-ray diffraction and Raman spectroscopy. The angle of incidence had a stronger effect on the structure and nanomechanical properties than the number of laser pulses.

Nanotechnology has been a revolutionary thrust in recent years of development of science and technology for its broad appeal for employing a novel idea for relevant technological applications in particular and for mass-scale production and marketing as common man commodity in general. An interesting aspect of this emergent technology is that it involves scientific research community and relevant industries alike. Top-down and bottom-up approaches are two broad division of production of nanoscale materials in general. However, both the approaches have their own limits as far as large-scale production and cost involved are concerned. Therefore, novel new techniques are desired to be developed to optimize production and cost. Directed self-assembly seems to be a promising technique in this regard; which can work as a bridge between the top-down and bottom-up approaches. This article reviews how directed self-assembly as a technique has grown up and outlines its future prospects.

Surfaces of thoroughly cleaned [311] silicon were nanostructured in air and deionised water medium by excimer laser at laser fluence of 2 J/cm(2), reprate of 1 Hz and irradiated for 100 laser pulses. Nanostructured surfaces were characterized by laser scanning confocal microscope and atomic force microscopy and it was observed that more isolated features can be achieved at nanoscale in deionised water medium. Surface roughness was found lesser in the case of water medium. For the same laser fluence and number of laser pulses used to nanostructure, red lumininescence was observed in case of air medium while green luminescence was observed for the deionized water medium.

It has been demonstrated that acid-treated graphene samples as well as reduced graphene oxide show fairly intense blue emission centered around 440 nm. Reduction of graphene oxide can be carried out either chemically or by using different types of radiations. Blue emission from graphene-based materials can be combined with the yellow emission from materials like ZnO to produce white light sources. (C) 2010 Elsevier Ltd. All rights reserved.

Controlled single step fabrication of silicon conical surface modulations on [311] silicon surface is reported utilizing KrF excimer laser [λ=248 nm] at laser fluence below ablation threshold laser fluence. When laser fluence was increased gradually from 0 to 0.2 J/cm2 for fixed 200 numbers of shots; first nanopores are observed to form at 0.1 J/cm2, then very shallow nanocones evolve as a function of laser fluence. At 0.2 J/cm2, nanoparticles are observed to form. Up to 0.15 J/cm2 the very shallow nanocone volume is smaller but increases at a fast rate with laser fluence thereafter. It is observed that the net material volume before and after the laser irradiation remains the same, a sign of the melting and resolidification without any ablation.

The effect of KrF excimer laser energy density (below and above the ablation threshold), number of shots and angle of laser incidence on the morphological reconstruction, structure and specular reflectance of Si[311] surfaces is reported. At low energy densities (0.1 to 0.3 J/cm2) laser irradiation results in a variety of nanostructures, depending on laser energy density and number of shots, such as nanopores (40-60 nm dia) and nanoparticles (40-80 nm dia). At energies greater than the laser ablation threshold (2 to 5 J/cm2) the formation of nanowires (200 nm dia, 6-8 microm length), and closely spaced silicon nanograins (100-150 nm dia) is observed. Experiments to study the effect of laser irradiation in the proximity of a fixed shape such as a linear step edge in the form of a stainless steel blade and a cylindrical cross-section Cu wire were also carried out. In both cases, linearly organized nanoparticles (150-200 nm diameter) and nanowires (60-80 nm diameter) formed close to the edge. There is a systematic degradation of long-range order with the number of shots and laser energy density as evidenced from X-ray diffraction studies. At an energy density of 2 J/cm2, and 100 shots the [311] oriented silicon surface made a transition to a randomly oriented nanocrystalline state.

We describe a novel process for the production of nanoparticles of Cu, Ag, Fe and Al which involves exploding their respective wires, triggered by large current densities in the wires. The particles are characterised by X-ray diffraction (XRD) and atomic force microscopy (AFM). Particle sizes in the range 20–100nm were obtained employing this technique. The XRD results reveal that the nanoparticles continue to retain lattice periodicity at reduced particle sizes, displaying in some cases evidence of lattice strain and preferential orientation. In the case of Fe, Mossbauer spectroscopy reveals loss of ferromagnetism as a result of the reduced size of the particles.