Coexistent VO2 (M) and VO2 (B) Polymorphous Thin Films with Multiphase-Driven Insulator-Metal Transition.

Reversible insulator-metal transition (IMT) and structure phase change in vanadium dioxide (VO2) remain vital and challenging with complex polymorphs. It is always essential to understand the polymorphs that coexist in desired VO2 materials and their IMT behaviors. Different electrical properties and lattice alignments in VO2 (M) and VO2 (B) phases have enabled the creation of versatile functional devices. Here, we present polymorphous VO2 thin films with coexistent VO2 (M) and VO2 (B) phases and phase-dependent IMT behaviors. The presence of VO2 (B) phases may induce lattice distortions in VO2 (M). The plane spacing of (011)M in the VO2 (M) phase becomes widened, and the V-V and V-O vibrations shift when more VO2 (B) phase exists in the VO2 (M) matrix. Significantly, the coexisting VO2 (B) phases promote the IMT temperature of the polymorphous VO2 thin films. We expect that such coexistent polymorphs and IMT variations would help us to understand the microstructures and IMT in the desired VO2 materials and contribute to advanced electronic transistors and optoelectronic devices.

Monolayer WS2 Lateral Homosuperlattices with Two-dimensional Periodic Localized Photoluminescence.

Homojunctions and homosuperlattices are essential structures and have been widely explored for use in advanced electronic and optoelectronic devices. However, artificially manipulating crystalline phases in two-dimensional (2D) monolayers is still challenging, especially when attempting to engineer lateral homogeneous junctions in a single monolayer of transition metal dichalcogenides (TMDs). Herein, we demonstrate a lateral homosuperlattice (MLHS) with alternating 1T and 2H domains in a 2D WS2 monolayer plane. In MLHSs, the 2H domains, which are laterally localized and isolated by potential wells, manifest junction interfaces and irradiated photoluminescence (PL) with a lateral periodic distribution in the two-dimensional plane. The studies on MLHSs here can provide further understanding of lateral homojunctions and homosuperlattices in a monolayer plane, providing an alternative route to modulate optical and electronic behaviors in TMD monolayers.

Low Deposition Temperature Amorphous ALD-Ga2O3 Thin Films and Decoration with MoS2 Multilayers toward Flexible Solar-Blind Photodetectors.

Flexible sensors and photodetectors are among the robust and powerful strategies for advanced and smart devices. Meanwhile, wide band-gap metal oxides are competitive candidates for fabricating flexible solar-blind photodetectors (SBPDs) but still challenging in both fundamental and practical fields. Here, we demonstrate the amorphous ALD-Ga2O3 (am-ALD-Ga2O3) thin films realized at a moderate temperature toward flexible SBPDs. The bandgap (Eg) of 4.88-5.04 eV depends on and changes with the thickness of am-ALD-Ga2O3 thin films during atomic layer deposition (ALD) processes. The SBPDs are fabricated with the as-grown am-ALD-Ga2O3 thin films on desired substrates and exhibit an Ilight/Idark ratio of up to ∼4.5 × 104 and dark current down to ∼10-13 A. Subsequently, decorating the ALD-Ga2O3 channels with MoS2 multilayers helps improve the photocurrent of SBPDs that worked in the deep ultraviolet region. We expect that our work will offer more opportunities to understand and exploit am-ALD-Ga2O3 thin films toward advanced flexible SBPDs and functional sensors.

Paper-based biosensor based on phenylalnine ammonia lyase hybrid nanoflowers for urinary phenylalanine measurement.

The Phenylketonuria (PKU) is an inborn defect of phenylalanine (Phe) metabolism, in which Phe accumulated in the blood causing alterations at the central nervous system. Therefore, the detection of PKU is very important for the early diagnosis of PKU patients. However, existing tests for PKU are time-consuming and require high-resource laboratories. In this study, a novel paper-based biosensor based on phenylalnine ammonia lyase (PAL) hybrid nanoflowers was constructed that provides a semi-quantitative output of the concentration of Phe from urine samples. PAL@Ca3(PO4)2 hybrid nanoflowers (PAL@NF) were first prepared using PAL and Ca2+. Synthesis conditions of the PAL@NF on the formation of the PAL@NF were optimized. The PAL@NF exhibited 90% activity recovery under optimal condition. Compared with free PAL, the PAL@NF displayed good storage stability and increased tolerance to proteolysis. After five consecutive operating cycles, the PAL@NF still retained 73% of its initial activity, indicating excellent reusability. Furthermore, the paper-based biosensor was able to detect Phe concentration in urine samples, and exhibited good linearity to the Phe concentrations in the range from 60 to 2400 µM and the response time was only about 10 min. Therefore, the paper-based biosensor can be a promising candidate as a biosensor for the detection of PKU.