Development and Analytical Evaluation of a Point-of-Care Electrochemical Biosensor for Rapid and Accurate SARS-CoV-2 Detection.

The COVID-19 pandemic has underscored the critical need for rapid and accurate screening and diagnostic methods for potential respiratory viruses. Existing COVID-19 diagnostic approaches face limitations either in terms of turnaround time or accuracy. In this study, we present an electrochemical biosensor that offers nearly instantaneous and precise SARS-CoV-2 detection, suitable for point-of-care and environmental monitoring applications.

Formation of CuInGaS Thin Films through a Solution Approach: Nonlinear Variation of Fermi Energy and Band Gap Bowing.

We report the formation of CuInGaS (CIGS) thin films through a solution approach, namely, successive ionic layer adsorption and reaction (SILAR) technique. The obtained films possessed a high degree of crystallinity indicating the efficacy of the deposition process in forming CIGS films. A series of alloys have evidenced band gap bowing, that is, the optical band gap does not follow a linear relationship with the composition; the band gap of an intermediate compound is higher than that is interpolated from a linear relationship or Vegard's law.

Necessity of Quantifying Urbach Energy through Scanning Tunneling Spectroscopy.

In this Letter, we introduce scanning tunneling spectroscopy (STS) to quantify the Urbach energy () in disordered semiconductors. The technique enabled us to gain precise information on the extending component of conduction and valence band-edges responsible for Urbach tailing, ; such information has been obtained from the width of band-energy-histograms drawn from STS studies at many different points. STS, as a probing method at the microscopic scale to derive , is in contrast to commonly employed optical spectroscopy studies which provide information at the macroscopic scale.

Origin of bandgap bowing in CsNaAgBiCldouble perovskite solid-state alloys: a paradigm through scanning tunneling spectroscopy.

Bandgap bowing has recently been emerged as an effective strategy toward band-engineering in metal halide perovskites. In this work, we report extensive studies on the bowing phenomenon in CsNaBiCldouble perovskite upon alloying with silver at the sodium site. Through optical spectroscopy, composition-dependent bandgap in CsNaAgBiCl(0 ⩽⩽ 1) evidenced bandgap bowing with an upward-concave nature.

Reverse bandgap-bowing in nickel-cadmium sulfide alloys (NiCdS) and its origin.

We present evolution of band energies in α-NiS when alloyed with a cationic doping through isovalent cadmium (Cd). Optical bandgap of nickel-cadmium sulfide (NiCdS) alloys, as a deviation from the linear relationship or Vegard's law, have exhibited a reverse bandgap-bowing in the form of downward-concave dependence. Such a phenomenon, which manifests as a negative value of bowing coefficient (), is uncommon in chalcogenide alloys.

Gas-Induced Confinement-Deconfinement Interplay in Organic-Inorganic Hybrid Perovskite Thin Film Results in Systematic Band Modulation.

Gas-induced growth of organic-inorganic hybrid perovskites, especially methylammonium lead iodide (MAPbI), has shown interesting properties and applications in the area of optoelectronics. In this report, we introduce a method of gas-induced band gap engineering of thin films of MAPbI due to systematic dimensional confinement-deconfinement along the crystallographic axis of growing MAPbI. Interestingly, such a restricted growth phenomenon was observed when the hexylammonium lead iodide (two-dimensional hybrid perovskite) film was exposed to methylamine gas instead of the conventional PbI film-methylamine gas precursor pair.

Tin(IV) Substitution in (CHNH)SbI: Toward Low-Band-Gap Defect-Ordered Hybrid Perovskite Solar Cells.

The prevailing issue of wide optical gap in defect-ordered hybrid iodide perovskites has been addressed in this effort by heterovalent substitution at the metal site. With the introduction of Sn in the (CHNH)SbI structure, we have successfully lowered the pristine optical gap (2 eV) of the perovskite to a close-to optimum one (1.55 eV).

p-i-n heterojunctions with BiFeO3 perovskite nanoparticles and p- and n-type oxides: photovoltaic properties.

We formed p-i-n heterojunctions based on a thin film of BiFeO3 nanoparticles. The perovskite acting as an intrinsic semiconductor was sandwiched between a p-type and an n-type oxide semiconductor as hole- and electron-collecting layer, respectively, making the heterojunction act as an all-inorganic oxide p-i-n device. We have characterized the perovskite and carrier collecting materials, such as NiO and MoO3 nanoparticles as p-type materials and ZnO nanoparticles as the n-type material, with scanning tunneling spectroscopy; from the spectrum of the density of states, we could locate the band edges to infer the nature of the active semiconductor materials.