Enhanced HER Efficiency of Monolayer MoS2 via S Vacancies and Nano-Cones Array Induced Strain Engineering.

Molybdenum disulfide (MoS2 ) has gained significant attention as a promising catalyst for hydrogen evolution reaction (HER). The catalytic performance of MoS2 can be enhanced by either altering its structure or regulating external conditions. In this study, a novel approach combining the introduction of sulfur vacancy (VS ) and biaxial tensile strain to create more active sites and modulate the band structure of monolayer MoS2 is proposed. To achieve the desired strain level, nano-cones (NCs) array substrates facilely fabricated by dip-pen nanolithography (DPN) are employed. The magnitude of the applied tensile strain can be finely tuned via adjusting the height of the NCs. Furthermore, on-chip electrochemical devices are constructed based on artificial structures, enabling precise optimization of HER performance of MoS2 through the synergistic effect of VS and strain. Combined with the d-band theory, it reveals that the HER properties of VS -MoS2 are highly dependent on the degree of tensile strain. This study presents a promising avenue for the design and preparation of high-performance 2D catalysts for energy conversion and storage applications.

Amplified spontaneous emission from DCJTB encapsulated in mesostructured composite silica SBA-15.

Amplified spontaneous emission (ASE) characteristics of a red dye 4-(Dicyanomethylene)-2-t-butyl-6-(1,1,7,7- etramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) encapsulated in a highly ordered mesoporous SBA-15 were studied. The mesoporous composite silica film loaded with organic dye has been successfully synthesized by a solgel reaction process and a simple postgrafting method at room temperature. The spectrum narrowing phenomena has been observed when the composite film is pumped at λp=532 nm by a Nd:YAG ed laser. There is a substantial reduction in the full width at half-maximum of the emitting light, which is one of the signatures of the presence of ASE. The ASE threshold and net gain, respectively, reached 0.03 mJ pulse-1 and 34.7 cm-1 for the DCJTB encapsulated in mesoporous SBA-15 film. The optimized ASE properties owe much to the effects of the better spatial confinement of the molecules in the ordered mesoporous structure of the host SBA-15.

Truthful Incentive Mechanisms for Social Cost Minimization in Mobile Crowdsourcing Systems.

With the emergence of new technologies, mobile devices are capable of undertaking computational and sensing tasks. A large number of users with these mobile devices promote the formation of the Mobile Crowdsourcing Systems (MCSs). Within a MCS, each mobile device can contribute to the crowdsourcing platform and get rewards from it. In order to achieve better performance, it is important to design a mechanism that can attract enough participants with mobile devices and then allocate the tasks among participants efficiently. In this paper, we are interested in the investigation of tasks allocation and price determination in MCSs. Two truthful auction mechanisms are proposed for different working patterns. A Vickrey-Clarke-Groves (VCG)-based auction mechanism is proposed to the continuous working pattern, and a suboptimal auction mechanism is introduced for the discontinuous working pattern. Further analysis shows that the proposed mechanisms have the properties of individual rationality and computational efficiencies. Experimental results suggest that both mechanisms guarantee all the mobile users bidding with their truthful values and the optimal maximal social cost can be achieved in the VCG-based auction mechanism.

Immunogenicity of an adenovirus-vectored bivalent vaccine against wild type SARS-CoV-2 and Omicron variants in a murine model.

BACKGROUND: The emergence and rapid spread of new mutant strains of SARS-CoV-2 necessitate the development of a new generation vaccine capable of neutralizing a broad range of variants. When the SARS-CoV-2 Omicron variant emerged, individuals in China had already received an inactivated (INA) or a type 5 adenovirus-vectored (Ad5) SARS-CoV-2 vaccine targeting the wild-type virus. We have recently developed a bivalent recombinant type 5 vaccine targeting both the wild-type strain and the Omicron variant (Ad5-nCoV/O). The objectives of this study were to assess the immunogenicity of the bivalent vaccine as a booster against both the wild type and the Omicron variant. METHODS: In the single immunization model, mice received one intramuscular immunization with monovalent or bivalent Ad5-vectored vaccines targeting both wild-type SARS-CoV-2 and Omicron variants. In the prime-boost model, mice were primed intramuscularly with an INA or Ad5-vectored vaccine targeting wild-type SARS-CoV-2, and then boosted intramuscularly or intranasally with heterologous or homologous INA or monovalent or bivalent Ad5-vectored vaccines targeting both wild-type SARS-CoV-2 and Omicron variants. The vaccine-induced antibody responses and cellular immune responses were measured using ELISA, pseudovirus-based neutralization assays, the intracellular cytokine staining (ICS) and ELISpot. RESULTS: Single-dose prime vaccination with the monovalent and bivalent vaccines elicited robust antibody responses and CD4 + and CD8 + cellular responses against the spike protein of WT and Omicron SARS-CoV-2. Both intramuscular and intranasal boost vaccination with the bivalent Ad5-nCoV/O following a prime with INA or Ad5-vectored vaccines induced strong serum neutralization antibody responses to both wild type and Omicron variants. A heterologous prime-boost vaccination elicited greater neutralization antibody responses than a homologous prime-boost vaccination when mice were boosted with Ad5-vectored vaccines following a prime with INA. Intranasal boost also resulted in significant mucosal IgA responses. CONCLUSION: The bivalent vaccine Ad5-nCoV/O exhibited robust immunogenicity, inducing broad-spectrum cross-neutralizing antibodies and cellular immune responses against both wild type and Omicron variants of SARS-CoV-2. The results demonstrated the potential of the bivalent vaccine in addressing the challenges posed by emerging SARS-CoV-2 Omicron variants.

Space-confined and substrate-directed synthesis of transition-metal dichalcogenide nanostructures with tunable dimensionality.

Atomically thin transition-metal dichalcogenide (TMDC) nanostructures are predicted to exhibit novel physical properties that make them attractive candidates for the fabrication of electronic and optoelectronic devices. However, TMDCs tend to grow in the form of two-dimensional nanoplates (NPs) rather than one-dimensional nanoribbons (NRs) due to their native layered structure. Herein, we have developed a space-confined and substrate-directed chemical vapor deposition strategy for the controllable synthesis of WS2, WSe2, MoSe2, MoS2, WS2(1-x)Se2x NPs and NRs. TMDC NRs with lengths ranging from several micrometers to 100 µm have been obtained and the widths of TMDC NRs can be effectively tuned. Moreover, we found that TMDC NRs show different growth behaviors on van der Waals (vdW) and non-vdW substrates. The micro-nano structures, optical and electronic properties of synthesized TMDC NRs have been systematically investigated. This approach provides a general strategy for controllable synthesis of TMDC NRs, which makes these materials easily accessible as functional building blocks for novel optoelectronic devices.

Electrospinning Fabricating Au/TiO2 Network-like Nanofibers as Visible Light Activated Photocatalyst.

Exploiting photocatalysts with characteristics of low cost, high reactivity and easy recovery offer great potentials for complete elimination of toxic chemicals and environmental remediation. In this work, Au/TiO2 network-like nanofibers were fabricated using a facile electrospinning technique followed by calcinations in air. Photocatalytic tests indicate that the Au/TiO2 network-like nanofibers possess an excellent photodegradation rate of rhodamine B (RB) under UV, visible and natural light radiation. The enhanced photocatalytic activity can be attributed to the plasmonic resonance absorption of Au nanoparticles, and photogenerated electrons and holes are effectively separated by the Au/TiO2 heterojunction structures. Furthermore, the three-dimensional network structure can provide a large number of active sites for RB degradation.

Random lasing in human tissues embedded with organic dyes for cancer diagnosis.

Various nanostructures found in biological organisms are often complex and they exhibit unique optical functions. This study surprisingly found that typical random lasing occurs in cancerous human tissues embedded with the nanotextured organic dye 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7- tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB). Hematoxylin and eosin stain images show that there are more laser resonators in cancerous tissues, caused by a large number of disordered scatters. It is also noteworthy that the random lasing thresholds were found to relate to the tumor malignancy grade. Consequently, the resulting typical random lasing resonators differ between cancerous tissues in different malignancy grades. Further studies are warranted to investigate tissue optical spectroscopy in the field of cancer diagnostics.