Room-Temperature High-Performance Photodetector and Phototransistor Based on PdSe2/ZnIn2S4 Alloy Heterojunctions.

Various semiconductor devices have been developed based on 2D heterojunction materials owing to their distinctive optoelectronic properties. However, to achieve efficient charge transfer at their interface remains a major challenge. Herein, an alloy heterojunction concept is proposed. The sulfur vacancies in ZnIn2S4 are filled with selenium atoms of PdSe2. This chemically bonded heterojunction can significantly enhance the separation of photocarriers, providing notable advantages in the field of photoelectric conversion. As a demonstration, a two-terminal photodetector based on the PdSe2/ZnIn2S4 heterojunction materials is fabricated. The photodetector exhibits stable operation in ambient conditions, showcasing superior performance in terms of large photocurrent, high responsivity (48.8 mA W-1) and detectivity (1.98 × 1011 Jones). To further validate the excellent optoelectronic performance of the heterojunction, a tri-terminal phototransistor is also fabricated. Benefiting from gate voltage modulation, the photocurrent is amplified to milliampere level, and the responsivity is increased to 229.14 mA W-1. These findings collectively demonstrate the significant potential of the chemically bonded PdSe2/ZnIn2S4 alloy heterojunction for future optoelectronic applications.

Design of a dynamic multi-topological charge graphene orbital angular momentum metalens.

Traditional OAM generation devices are bulky and can generally only create OAM with one specific topological charge. Although metasurface-based devices have overcome the volume limitations, no tunable metasurface-based OAM generators have been demonstrated to date. Here, a dynamically tunable multi-topological charge OAM generator based on an ultrathin integrable graphene metalens is demonstrated by simulation using the detour phase technique and spatial multiplexing. Different topological charges can be designed on different focal planes. Stretching the OAM graphene metalens allows the focal plane and the topological values to be changed dynamically. This design method paves an innovative route toward miniaturization and integrating OAM beam-type photonic devices for practical applications.

Advanced Optical Information Encryption Enabled by Polychromatic and Stimuli-Responsive Luminescence of Sb-Doped Double Perovskites.

The smart materials with multi-color and stimuli-responsive luminescence are very promising for next generation of optical information encryption and anti-counterfeiting, but these materials are still scarce. Herein, a multi-level information encryption strategy is developed based on the polychromatic emission of Sb-doped double perovskite powders (SDPPs). Cs2NaInCl6:Sb, Cs2KInCl6:Sb, and Cs2AgInCl6:Sb synthesized through coprecipitation methods exhibit broadband emissions with bright blue, cyan, and orange colors, respectively. The information transmitted by specific SDPP is encrypted when different SDPPs are mixed. The confidential information can be decrypted by selecting the corresponding narrowband filter. Then, an encrypted quick response (QR) code with improved security is demonstrated based on this multi-channel selection strategy. Moreover, the three types of SDPPs exhibit three different water-triggered luminescence switching behaviors. The confidential information represented by Cs2NaInCl6:Sb can be erased/recovered through a simple water spray/drying. Whereas, the information collected from the green channel is permanently erased by moisture, which fundamentally avoids information leakage. Therefore, different encryption schemes can be designed to meet a variety of encryption requirements. The multicolor and stimuli-responsive luminescence greatly enrich the flexibility of optical information encryption, which leaps the level of security and confidentiality.

A Varifocal Graphene Metalens for Broadband Zoom Imaging Covering the Entire Visible Region.

The ever-increasing demand for miniaturized optical systems has placed stringent requirements on the core element: lenses. Developing ultrathin flat lenses with a varifocal capability and broadband spectral response is critical for diverse applications, but remains challenging and has been the focus of intensive research. The recent demonstration of tunable focal length for a single wavelength with metalenses marked an important milestone for transforming the complex and bulky tunable lens kit into a single flat lens. However, achieving color imaging with desired tunability over the entire visible spectrum essential for practical applications still remains elusive. Here we propose and demonstrate experimentally a broadband varifocal graphene metalens (250 nm in thickness) covering the entire visible spectrum. It is able to simultaneously tune the focal lengths for different wavelengths continuously. By laterally stretching the lens, an over 20% focal length tuning range can be achieved for red (650 nm), green (550 nm), and blue (450 nm) light as three example wavelengths. Zoom imaging of different objects located along the axial direction has been demonstrated at these wavelengths by simply controlling the stretch ratio of the graphene metalens. This broadband graphene zoom lens enables enormous applications in miniaturized imaging devices such as cell phones, wearable displays, and compact optical or communication systems with multi-color-channel functionalities.

Integrative QTL Identification, Fine Mapping and Candidate Gene Analysis of a Major Locus qLTG3a for Seed Low-Temperature Germinability in Rice.

Low-temperature germinability (LTG) is an important agronomic trait that can affect the planting time, planting area, and grain yield of staple crops, such as rice. However, the genetic mechanism of LTG is still unclear. In this study, a multi-parental permanent population with 208 single segment substitution lines (SSSLs) was used to conduct a genetic dissection for LTG across four cropping seasons. LTG was a typical quantitative trait with a high combined broad-sense heritability of 0.71. By comparison with the recipient parent, Huajingxian74, 24 SSSLs were identified as carrying LTG QTLs, which were further merged into integrated QTLs with shorter genetic distances by substitution mapping. Finally, 14 LTG QTLs were mapped on ten chromosomes, including seven positive-effect and seven negative-effect QTLs, with additive effect contributions ranging from 19.2 to 39.9%. qLTG3a, a main-effect and novel QTL, was confirmed by bulk segregant analysis using an F2 segregating population, and five key recombinants were selected to develop F3 populations for progeny testing. Marker-trait association analysis fine mapped qLTG3a to a 332.7-kb physical region between markers M6026 and M6341. Within this interval, 40 annotated genes were revealed, and three genes (Os03g0213300, Os03g0214400, and Os03g0214600) were considered as pivotal candidate genes for qLTG3a based on their sequence variations and expression patterns. Besides low temperature, qLTG3a can also enhance seed germination under standard temperature and osmotic stress. In summary, this study identified some genetic factors regulating LTG and opened a new window for breeding elite direct-seeded rice varieties. It will help reduce the climate risk in the production process of rice, which is of great significance to ensuring food security.

Diffraction-limited imaging with monolayer 2D material-based ultrathin flat lenses.

Ultrathin flat optics allow control of light at the subwavelength scale that is unmatched by traditional refractive optics. To approach the atomically thin limit, the use of 2D materials is an attractive possibility due to their high refractive indices. However, achievement of diffraction-limited focusing and imaging is challenged by their thickness-limited spatial resolution and focusing efficiency. Here we report a universal method to transform 2D monolayers into ultrathin flat lenses. Femtosecond laser direct writing was applied to generate local scattering media inside a monolayer, which overcomes the longstanding challenge of obtaining sufficient phase or amplitude modulation in atomically thin 2D materials. We achieved highly efficient 3D focusing with subwavelength resolution and diffraction-limited imaging. The high focusing performance even allows diffraction-limited imaging at different focal positions with varying magnifications. Our work paves the way for downscaling of optical devices using 2D materials and reports an unprecedented approach for fabricating ultrathin imaging devices.

LncRNA H19 Overexpression Activates Wnt Signaling to Maintain the Hair Follicle Regeneration Potential of Dermal Papilla Cells.

Androgenetic alopecia (AGA) is a common hair loss disorder resulting in seriously abnormal social interaction and psychological disorders. Transplantation with autologous dermal papilla cells represents a prospective therapy. However, the ability of dermal papilla cells to induce hair follicle development is lost upon cell culturing. Long non-coding RNAs (lncRNAs) are an important class of genes involved in various biological functions, are aberrantly expressed in disease and may play roles in the regulation of Wnt signaling, a critical pathway in maintaining the hair follicle-inducing capability of dermal papilla cells. Examination of dermal papilla cells by lncRNA microarray revealed that H19 was highly expressed in early passage dermal papilla cells compared with late-passage dermal papilla cells. In this study, we constructed H19-overexpressing dermal papilla cells to examine the role of H19 on hair follicle inductivity. Dermal papilla cells infected with lentivirus encoding H19 maintained their cell shape, and continued to display both multiple-layer aggregation and hair follicle-inducing ability upon prolonged culture. H19 exerted these effects through inducing miR-29a to activate Wnt signaling by directly downregulating the expression of Wnt suppressors, including DKK1, Kremen2, and sFRP2, thereby forming a novel regulatory feedback loop between H19 and miR-29a to maintain hair follicle- inducing potential. These results suggest that lncRNA H19 maintains the hair follicle-inducing ability of dermal papilla cells through activation of the Wnt pathway and could be a target for treatment of androgenetic alopecia.

Resilient Graphene Ultrathin Flat Lens in Aerospace, Chemical, and Biological Harsh Environments.

The development of ultrathin flat lenses has revolutionized the lens technologies and holds great promise for miniaturizing the conventional lens system in integrated photonic applications. In certain applications, the lenses are required to operate in harsh and/or extreme environments, for example aerospace, chemical, and biological environments. Under such circumstances, it is critical that the ultrathin flat lenses can be resilient and preserve their outstanding performance. However, the majority of the demonstrated ultrathin flat lenses are based on metal or semiconductor materials that have poor chemical, thermal, and UV stability, which limit their applications. Herein, we experimentally demonstrate a graphene ultrathin flat lens that can be applied in harsh environments for different applications, including a low Earth orbit space environment, strong corrosive chemical environments (pH = 0 and pH = 14), and biochemical environment. The graphene lenses have extraordinary environmental stability and can maintain a high level of structural integrity and outstanding focusing performance under different test conditions. Thus, it opens tremendous practical application opportunities for ultrathin flat lenses.

Spatially Modulating the Fluorescence Color of Mixed-Halide Perovskite Nanoplatelets through Direct Femtosecond Laser Writing.

Lead halide perovskites are widely applied in not only photovoltaics but also on-chip light sources and photon detection. To promote the incorporation of perovskite into integrated devices, microscale color patterning flexibility is a very important step. Here, we demonstrate spatially resolved modulation of the fluorescence of nanoplatelets (NPs) by femtosecond direct laser writing (fs-DLW). As the perovskite NP for the fs-DLW pattern is specially designed with a gradual bromide-iodide composition along the depth, the replacement of iodide ions by bromide ions can be activated under a controlled laser pulse and fluorescence is thus modulated from red to green. The effect of processing depth and NP thickness on fluorescence modulation is systemically investigated. The as-grown thick NP (thickness ≈ 500 nm) mainly exhibits a 690 nm emission from the bottom iodine-rich phase. After halide substitution induced by fs-DLW, a new fluorescence peak appears in the wavelength range of 540-600 nm; the peak position and intensity are controlled by the DLW conditions. The fluorescent color is spatially modulated from red to green, enabling microscale-resolved multicolor emission. Compared with other currently available techniques, microscale color patterning via fs-DLW is a straightforward mask-free one-step operation, yielding high spatial resolution and enabling three-dimensional patterning by the multiple-photon method. We demonstrate that arbitrary patterns can be drawn on a wide range of perovskite NPs, implying the potential applications in microencryption, sensors, multicolor displays, lasers, and light-emitting devices.