Jiuxiang Dai

Nature Communications, Published online: 01 June 2022; doi:10.1038/s41467-022-30519-w

Light: Science & Applications, Published online: 01 June 2022; doi:10.1038/s41377-022-00854-0

Light: Science & Applications, Published online: 01 June 2022; doi:10.1038/s41377-022-00850-4

Nature, Published online: 01 June 2022; doi:10.1038/s41586-022-04745-7

Nature, Published online: 01 June 2022; doi:10.1038/d41586-022-01476-7

Light: Science & Applications, Published online: 30 May 2022; doi:10.1038/s41377-022-00861-1

Light: Science & Applications, Published online: 30 May 2022; doi:10.1038/s41377-022-00855-z

This article reports the epitaxial growth of lead-free 2D Cs₃Cu₂I₅ perovskites, where the strong blue emission with a large Stocks shift and long (microsecond) lifetime is attributed to a radiative transition of self-trapped excitons. The Cs₃Cu₂I₅ photodetector reveals a high responsivity of 3.78 A W^–1 (270 nm, 5 V) with a fast characteristic (τ_rise/τ_decay ≈ 163/203 ms), outperforming congeneric UV sensors.

Abstract

The all-inorganic lead-free Cu-based halide perovskites represented by the Cs−Cu−I system, have sparked extensive interest recently due to their impressive photophysical characteristics. However, successive works on their potential application in light emission diodes and photodetectors rely on tiny polycrystals, in which the grain boundaries and defects may lead to the performance degradation of their embodied devices. Here, 2D all-inorganic perovskite Cs₃Cu₂I₅ single crystals are epitaxially grown on mica substrates, with a thickness down to 10 nm. The strong blue emission of the Cs₃Cu₂I₅ flakes may originate from the radiative transition of self-trapped excitons associated with a large Stocks shift and long (microsecond) decay time. Ultravioelt (UV) photodetectors based on individual Cs₃Cu₂I₅ nanosheets are fabricated via a swift and etching-free dry transfer approach, which reveal a high responsivity of 3.78 A W^–1 (270 nm, 5 V bias), as well as a fast response speed (τ_rise ≈163 ms, τ_decay ≈203 ms), outperforming congeneric UV sensors based on other 2D metal halide perovskites. This work therefore sheds light on the fabrication of green optoelectronic devices based on lead-free 2D perovskites, vital for the sustainable development of photoelectric technology.

A facile approach is developed for constructing high-quality metal-2D semiconductor junctions through the edge-guided electrodeposition. Cross-sectional imaging and transport measurements confirm the seamless contact of Pd with each layer of MoS₂ greatly reduces the contact barrier to ≈20 meV and contact resistance to ≈290 Ω µm and thus significantly increases the performance of FETs with Pd nanowire edge contacts.

Abstract

2D semiconductors, such as MoS₂ have emerged as promising ultrathin channel materials for the further scaling of field-effect transistors (FETs). However, the contact barrier at the metal-2D semiconductor junctions still significantly limits the device's performance. By extending the application of electrochemical deposition in 2D electronics, a distinct approach is developed for constructing metal-2D semiconductor junctions in an edge-contacted configuration through the edge-guided electrodeposition of varied metals. Both high-resolution microscopic imaging and electrical transport measurements confirm the successful creation of high-quality Pd-2D MoS₂ junctions in desired geometry by combining electrodeposition with lithographic patterning. FETs are fabricated on the obtained Pd-2D MoS₂ junctions and it is confirmed that these junctions exhibit a reduced contact barrier of ≈20 meV and extremely low contact resistance of 290 Ω µm and thus increase the averaged mobility of MoS₂ FETs to ≈108 cm² V ⁻¹ s⁻¹. This approach paves a new way for the construction of metal-semiconductor junctions and also demonstrates the great potential of the electrochemical deposition technique in 2D electronics.

Nature Materials, Published online: 31 May 2022; doi:10.1038/s41563-022-01253-x

High strains are applied to single-layer graphene by an atomic force microscopy (AFM) tip and the Raman signals are obtained simultaneously using a Raman–AFM system. Graphene is stretched up to 6.1% and the G and 2D bands of Raman signal are shifted by 277 and 660 cm⁻¹ respectively, which are unprecedented values.

Abstract

Graphene is known as a superstiff and extremely strong material. Hence, applying strains greater than 1% to graphene and simultaneously measuring changes in its physical properties has been challenging because of the limited methodologies for measuring both high strain and other physical properties. Here, Raman scattering measurement of suspended graphene under extremely high biaxial strain as large as 6.1% using an atomic force microscopy (AFM)–Raman spectroscopy measurement tool is reported. Nanoindentation is performed using AFM tips machined to have a flat top and a hole shape, resulting in a strained graphene area sufficiently large to enable the acquisition of a Raman signal. At the same time, the laser light is focused on the strained flat area of the graphene membrane. The Raman signals of the G and 2D bands of graphene are redshifted by 282 and 684 cm⁻¹, respectively, which is unprecedented for graphene. This measurement technique provides an effective methodology to measure variations in the physical properties of atomically thin materials under superhigh strain.

A direct deep ultraviolet (DUV) photolithography method, which enables fabrication of microstructures in bulk polystyrene cell culture substrates, is presented. Pipelines for generating ink-based DUV masks and micropattern virtualization further increase the remarkable straightforwardness of the process. This, combined with the high applicability, can significantly improve accessibility of this class of microfabrication techniques to a broad biological research community.

Abstract

Tissue-culture-ware polystyrene is the gold standard for in vitro cell culture. While microengineering techniques can create advanced cell microenvironments in polystyrene, they require specialized equipment and reagents, which hinder their accessibility for most biological researchers. An economical and easily accessible method is developed and validated for fabricating microstructures directly in polystyrene with sizes approaching subcellular dimensions while requiring minimal processing time. The process involves deep ultraviolet irradiation through a shadow mask or ink pattern using inexpensive, handheld devices followed by selective chemical development with common reagents to generate micropatterns with depths/heights between 5 and 10 µm, which can be used to guide cell behavior. The remarkable straightforwardness of the process enables this class of microengineering techniques to be broadly accessible to diverse research communities.

Nature Communications, Published online: 30 May 2022; doi:10.1038/s41467-022-30516-z

Nature Electronics, Published online: 30 May 2022; doi:10.1038/s41928-022-00766-2

This work reports the programmable information encryption by 2D van der Waals rare-earth material ErOCl based on the editable electric-tunable photoluminescence (PL). The correct information encoded in PL outputs can be tactfully decrypted from the PL intensity ratio of two thermal coupling transitions (²H_11/2–⁴I_15/2 and ⁴S_3/2–⁴I_15/2), which has been applied to ASCII codes and images encryption with high-security.

Abstract

High-security encryption has always been important in economic and military fields as well as in daily life. 2D van der Waals (vdW) rare-earth (RE) materials have advantages in photoluminescence (PL) modulation to achieve high-security encryption because of their multiple sharp emission peaks, which will facilitate the multimode regulation for high-security encryption of programmable information. Here, programmable information encryption has been achieved by applying 2D vdW ErOCl via the editable electric-tunable PL. The correct information encoded in PL outputs can be tactfully decrypted from the PL intensity ratio of ²H_11/2–⁴I_15/2 and ⁴S_3/2–⁴I_15/2 transitions. This strategy for ASCII codes and images encryption with high-security is demonstrated. This novel approach, PL modulation of 2D vdW RE material based on programmable electric inputs, will mark a new path to achieve high-security encryption.

BiOX/Bi/BiOX (X = Cl, Br) double-side nanosheet array catalyst, with vertically aligned BiOX nanosheets symmetrically grown on the two sides of horizontal Bi nanoplates, is constructed by a facile solvothermal route in the absence of any substrates. It shows enhanced photo(electro)catalytic performance in the selective oxidation of PhCH₂OH to PhCHO and hydrogen and oxygen evolution.

Abstract

Array-structured photocatalysts, featuring unique transport properties of charge carriers and special texture structures, have captured widespread interest in photocatalytic and/or photoelectrocatalytic applications. However, the fabrication of arrays usually suffers from complicated synthetic routes and the indispensable use of substrates. Herein, a novel BiOX/Bi/BiOX (X = Cl, Br) double-side nanosheet array catalyst, with vertically aligned BiOX nanosheets symmetrically grown on the two sides of horizontal Bi nanoplates, is first constructed by a facile solution-phase solvothermal route in the absence of any substrates. Both l-cysteine and ethylene glycol are found to play critical roles in the formation of Bi nanoplates and the growth of BiOX nanosheets. Thanks to the synergism of double-side metal-semiconductor array, BiOX/Bi/BiOX presents significantly boosted performance for photocatalytic selective oxidation of benzyl alcohol to benzaldehyde, far surpassing Bi/BiOX and pristine BiOX. Additionally, BiOX/Bi/BiOX also exhibits superior photoelectrocatalytic performance with excellent hydrogen and oxygen evolution reaction activity. The electrochemical analysis and photoluminescence results reveal that the middle Bi nanoplate can function as a fast transport channel for photogenerated electrons, significantly accelerating the separation of photogenerated carriers. This work provides a general substrate-free strategy to construct array catalysts with double-side structure and reveals the outstanding advantages toward improved photocatalysis.

An electrically and optically switchable logic operation encryption based on the photoluminescence (PL) ratio of ZnTe is developed. Two PL emissions can be selectively regulated by the electric and optical fields due to different responses of band-edge emission and defect emission. This work provides a design for the creation of logic operation encryption and holds great promise for high-security encryption.

Abstract

Logic operation encryption is emerging as a novel cryptographic mode, protecting logic operation from being attacked and tampered, and is a modern extension of conventional encryption system. However, the existing encryption methods are not conducive to the logic operation encryption due to the complexity, signal mode, and non-adjustability of their design. Herein, an advanced logic operation encryption method is designed via the photoluminescence ratio of ZnTe, and the electrically and optically switchable NAND (Not AND) and NOR (Not OR) encryption based on this method is implemented. Two photoluminescence emissions can be selectively regulated by the gate voltage and excitation laser based on the different responses of band-edge emission and defect emission. This novel approach will shed light on the development of high-security encryption and computer information protection.

Publication date: July–August 2022

Source: Materials Today, Volume 57

Author(s): Yanfang Niu, Xiao Yang, Jiajia Li, Yi Zeng, Keliang Liu, Wang Wan, Junlong Liao, Mengxiao Wei, Sen Li, Junning Zhang, Zhejun Chong, Xin Du, Zhongze Gu

Nature Electronics, Published online: 27 May 2022; doi:10.1038/s41928-022-00780-4

Nature Electronics, Published online: 27 May 2022; doi:10.1038/s41928-022-00781-3

Nature Electronics, Published online: 27 May 2022; doi:10.1038/s41928-022-00783-1