Uncovering upconversion photoluminescence in layered PbI above room temperature.

As a van der Waals (vdW) layered semiconductor material, lead iodide (PbI) possessing a direct bandgap with strong photoluminescence emission in visible range has gained wide attention in applications of photonic and optoelectronic devices. Here, upconversion photoluminescence (UPL) in exfoliated PbI flakes is demonstrated at room temperature and elevated temperatures. The linear power dependence of UPL emission with 532 nm excitation suggests the one-photon involved multiphonon-assisted UPL emission process, which is revealed by the temperature-dependent UPL emission measurement.

Multifractality in Surface Potential for Cancer Diagnosis.

Recent advances in high-resolution biomedical imaging have improved cancer diagnosis, focusing on morphological, electrical, and biochemical properties of cells and tissues, scaling from cell clusters down to the molecular level. Multiscale imaging revealed high complexity that requires advanced data processing methods of multifractal analysis. We performed label-free multiscale imaging of surface potential variations in human ovarian cancer cells using Kelvin probe force microscopy (KPFM).

Quantum plasmonic two-dimensional WS-MoS heterojunction.

Two-dimensional heterostructures have recently gained broad interest due to potential applications in optoelectronic devices. Their reduced dimensionality leads to novel physical effects beyond conventional bulk electronics. However, the optical properties of the 2D lateral heterojunctions have not been completely characterized due to the limited spatial resolution, requiring nano-optical techniques beyond the diffraction limit.

Ultrafast-UV laser integrating cavity device for inactivation of SARS-CoV-2 and other viruses.

Ultraviolet (UV) irradiation-based methods used for viral inactivation have provided an important avenue targeting severe acute respiratory-syndrome coronavirus-2 (SARS-CoV-2) virus. A major problem with state-of-the-art UV inactivation technology is that it is based on UV lamps, which have limited efficiency, require high power, large doses, and long irradiation times. These drawbacks limit the use of UV lamps in air filtering systems and other applications.

Coupling nanobubbles in 2D lateral heterostructures.

Two-dimensional transition metal dichalcogenides provide flexible platforms for nanophotonic engineering due to their exceptional mechanical and optoelectronic properties. For example, continuous band gap tunability has been achieved in 2D TMDs by elastic strain engineering. Localized elastic deformations in nanobubbles behave as "artificial atoms" with a spatially varying band gap resulting in funnelling of excitons and photocarriers.

Tip-Enhanced Photoluminescence of Freestanding Lateral Heterobubbles.

Two-dimensional (2D) semiconducting materials have promising applications in flexible optoelectronics, nanophotonics, and sensing based on the broad tunability of their optical and electronic properties. 2D nanobubbles form exciton funnels due to localized strain that can be used as local emitters for information processing. Their nanoscale optical characterization requires the use of near-field scanning probe microscopy (SPM).

Bandgap Engineering in 2D Lateral Heterostructures of Transition Metal Dichalcogenides via Controlled Alloying.

2D heterostructures made of transition metal dichalcogenides (TMD) have emerged as potential building blocks for new-generation 2D electronics due to their interesting physical properties at the interfaces. The bandgap, work function, and optical constants are composition dependent, and the spectrum of applications can be expanded by producing alloy-based heterostructures. Herein, the successful synthesis of monolayer and bilayer lateral heterostructures, based on ternary alloys of MoS Se -WS Se , is reported by modifying the ratio of the source precursors; the bandgaps of both materials in the heterostructure are continuously tuned in the entire range of chalcogen compositions.

Point-of-care detection, characterization, and removal of chocolate bloom using a handheld Raman spectrometer.

Chocolate bloom is an off-white coating on the surface of chocolate products due to the altered distribution of the ingredients. Bloom reduces the shelf-life of chocolate and affects its visual and tactile quality, all of which are serious concerns for chocolate manufacturers and consumers. The automated, rapid, and noninvasive point-of-care detection of chocolate bloom has been an essential but challenging problem.

Fluorescence imaging of stained red blood cells with simultaneous resonance Raman photostability analysis.

Optical spectroscopic imaging of biological systems has important applications in medical diagnosis, biochemistry, and image-guided surgery. Vibrational spectroscopy, such as Raman scattering, provides high chemical selectivity but is limited by weak signals and a large fluorescence background. Fluorescence imaging is often used by introducing specific dyes in biological systems to label different system parts and to increase the image contrast.