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Solution‐processed inorganic perovskites cause chemical and structural defects unfavorable for photodetector application. Using a binary solvent, defects in CsPbIxBry (CPIB) perovskite are passivated with poly 4‐vinylpyridine (PVP) and Poly methyl methacrylate (PMMA) polymers. X‐ray photoelectron spectroscopy and FTIR spectra reveal a Lewis base‐acid interaction between Pb2+ and polymer, confirming the passivation of CPIB perovskite. Scanning electron microscopy analysis shows a dual‐surface morphology with microribbons and microcrystals in perovskites. After PMMA treatment, CPIB perovskite exhibits a blue shift in the bandgap (1.8 to 1.95 eV), while the PVP induced a redshift, reducing the bandgap to 1.7 eV. Blue shift in PL analysis indicates modification of grain boundaries. A higher lifetime obtained for CPIB/PVP confirms the restraint of non‐radiative recombinations. Photodetectors are fabricated with pristine CPIB, CPIB/PVP, and CPIB/PMMA perovskites. The passivated CPIB/PVP‐based photodetector exhibits a quick rise time of ≈23 ms and a decay time of ≈17 ms. It also demonstrates a remarkable photoresponsivity of 23 mA W−1, an internal quantum efficiency of 4.9%, and a detectivity of 15.0 × 1010 Jones at 10 mW cm−2 light intensity. This approach shows the potential for environmentally stable polymers to passivate inorganic perovskites for high photodetection performance. [ABSTRACT FROM AUTHOR]

In this work, γ-In2Se3 thin films were deposited on a p-type Si (p-Si) substrate using RF magnetron sputtering. The effects of Ar+ ion irradiation on structural, optical, morphological, and photodetector characteristics of γ-In2Se3 were investigated. Raman spectra analysis showed a decline in the crystallinity of hexagonal γ-In2Se3 as Ar+ ion fluence increased. XPS results revealed an increased oxygen peak intensity, indicating the incorporation of oxygen on the material’s surface. Additionally, shifts in the binding energies of In and Se peaks were observed. The optical band gap decreased from 2.13 to 1.85 eV after ion irradiation. SRIM 2008 Monte Carlo simulation revealed an Ar+ ion range of ~ 284 Å in γ-In2Se3 films. Morphological changes were insignificant at lower fluences, but grain agglomeration occurred at higher Ar+ ion fluence. EDS analysis indicated decreasing Se atomic % and increasing O with higher irradiation. Photodetectors exhibited improved performance with increased ion fluence, showing higher photoresponsivity, photosensitivity, photodetectivity, fast rise, and decay time. The present study provides insights into the material responses to radiation hardening and its promising applications in developing space-based photodetectors. [ABSTRACT FROM AUTHOR]

A long-standing question in collective cell migration has been what might be the relative advantage of forming a cluster over migrating individually. Does an increase in the size of a collectively migrating group of cells enable them to sample the chemical gradient over a greater distance because the difference between front and rear of a cluster would be greater than for single cells? We combined theoretical modeling with experiments to study collective migration of the border cells in-between nurse cells in the Drosophila egg chamber. We discovered that cluster size is positively correlated with migration speed, up to a particular point above which speed plummets. This may be due to the effect of viscous drag from surrounding nurse cells together with confinement of all of the cells within a stiff extracellular matrix. The model predicts no relationship between cluster size and velocity for cells moving on a flat surface, in contrast to movement within a 3D environment. Our analyses also suggest that the overall chemoattractant profile in the egg chamber is likely to be exponential, with the highest concentration in the oocyte. These findings provide insights into collective chemotaxis by combining theoretical modeling with experimentation.

Border cell migration in the Drosophila ovary has emerged as a genetically tractable model for studying collective cell movement. Over many years border cell migration was exclusively studied in fixed samples due to the inability to culture stage 9 egg chambers in vitro. Although culturing late-stage egg chambers was long feasible, stage 9 egg chambers survived only briefly outside the female body. We identified culture conditions that support stage 9 egg chamber development and sustain complete migration of border cells ex vivo. This protocol enables one to compare the dynamics of egg chamber development in wild-type and mutant egg chambers using time-lapse microscopy and taking advantage of a multiposition microscope with a motorized imaging stage. In addition, this protocol has been successfully used in combination with fluorescence resonance energy transfer biosensors, photo-activatable proteins, and pharmacological agents and can be used with wide-field or confocal microscopes in either an upright or an inverted configuration.

E-cadherin is a major homophilic cell-cell adhesion molecule that inhibits motility of individual cells on matrix. However, its contribution to migration of cells through cell-rich tissues is less clear. We developed an in vivo sensor of mechanical tension across E-cadherin molecules, which we combined with cell-type-specific RNAi, photoactivatable Rac, and morphodynamic profiling, to interrogate how E-cadherin contributes to collective migration of cells between other cells. Using the Drosophila ovary as a model, we found that adhesion between border cells and their substrate, the nurse cells, functions in a positive feedback loop with Rac and actin assembly to stabilize forward-directed protrusion and directionally persistent movement. Adhesion between individual border cells communicates direction from the lead cell to the followers. Adhesion between motile cells and polar cells holds the cluster together and polarizes each individual cell. Thus, E-cadherin is an integral component of the guidance mechanisms that orchestrate collective chemotaxis in vivo.

In this study, we investigated the effect of RF sputtering power on the structural, morphological, optical, and photodetector properties of γ-In2Se3 thin films. The In2Se3 films were deposited at 80 W, 100 W, 120 W, and 150 W and characterized using XRD, Raman spectroscopy, FE-SEM, and EDS. The XRD results showed that the rise in RF sputtering power enhanced the crystallinity of the prepared films. The formation of the γ phase of In2Se3 was confirmed by Raman spectroscopy. FE-SEM images showed that the In2Se3 films were compact, smooth, and had uniform grain growth. The increase in film thickness with RF power was observed in cross-sectional FE-SEM. The EDS analysis confirmed that as-prepared γ-In2Se3 films have stoichiometric chemical composition. The optical bandgap of the films decreased from 2.07 to 1.85 eV with an increase in RF power, which can be attributed to an increase in crystallite size due to an increase in RF power. The optoelectronic performance of the films was evaluated by fabricating γ-In2Se3 photodetectors. The photodetector fabricated at 100 W sputtering power had excellent performance. It had a detectivity of 2.5 × 108 Jones, photoresponsivity of 17 µA/W, fast rise time of 0.27 s, and decay times of 0.31 s. [ABSTRACT FROM AUTHOR]

We report the synthesis of tungsten sulfide (WS2) films using RF‐magnetron sputtering at different RF powers. X‐ray diffraction (XRD) data confirm the hexagonal crystal structure of WS2 with an average crystallite size of ∼44.54 Å. With increased RF power, the preferred orientation of WS2 crystallites shifts from (002) to (100). Linear sweep voltammetry (LSV) was used to assess the Photoelectrochemical (PEC) activity of WS2 films. The film deposited at 150 W demonstrated the highest photocurrent density of 5.44 mA/cm2. The 150 W film also showed a lower Tafel slope of ∼0.374 V/decade, indicating superior PEC activity. Mott Schottky's (MS) analysis revealed a notable shift in the flat band potential towards the negative side, suggesting a shifting of the Fermi level towards the conduction band. WS2 film grown at 150 W demonstrated a majority charge carrier density of 6.2×1021 cm−3 and a depletion layer width of 1.54 nm. The observed low charge transfer resistance of 155 Ω contributed to the enhanced PEC activity with a relaxation time constant of 37 ms. These properties suggest that WS2 can be suitable for PEC water splitting. [ABSTRACT FROM AUTHOR]