Metal Oxide Heteronanostructures Prepared by Electrospinning for the Humidity Detection: Fundamentals and Perspectives

Humidity is a critical environmental parameter for several production processes and its control/monitoring is of great importance in maintaining the quality of goods and products. In this context, metallic oxide ceramic nanostructures are materials of great technological interest in the fabrication of moisture sensors because they have good chemical/structural stability and high surface area/volume ratio. The electrical response of these sensors relates to the chemisorbed and physisorbed layers of water molecules on the surface of the ceramic particles and to the capillary condensation of water in the microscopic pores between the particles. Based on these aspects, this work presents the fundamentals, electrical/electronic properties, influence of dopants, novel preparation procedure by electrospinning and perspectives of application of TiO2:WO3 metal oxide heteronanostructures as humidity sensors.

Fine-tuning electronic structure of N-doped graphitic carbon-supported Co-and Fe-incorporated Mo_(2)C to achieve ultrahigh electrochemical water oxidation activity

Mo_(2)C is an excellent electrocatalyst for hydrogen evolution reaction(HER).However,Mo_(2)C is a poor electrocatalyst for oxygen evolution reaction(OER).Herein,two different elements,namely Co and Fe,are incorporated in Mo_(2)C that,therefore,has a finely tuned electronic structure,which is not achievable by incorporation of any one of the metals.Consequently,the resulting electrocatalyst Co_(0.8)Fe_(0.2)-Mo_(2)C-80 displayed excellent OER catalytic performance,which is evidenced by a low overpotential of 214.0(and 246.5)mV to attain a current density of 10(and 50)mA cm^(-2),an ultralow Tafel slope of 38.4 mV dec^(-1),and longterm stability in alkaline medium.Theoretical data demonstrates that Co_(0.8)Fe_(0.2)-Mo_(2)C-80 requires the lowest overpotential(1.00 V)for OER and Co centers to be the active sites.The ultrahigh catalytic performance of the electrocatalyst is attributed to the excellent intrinsic catalytic activity due to high Brunauer-Emmett-Teller specific surface area,large electrochemically active surface area,small Tafel slope,and low chargetransfer resistance.

Modular divergent creation of dual-cocatalysts integrated semiconducting sulfide nanotriads for enhanced photocatalytic hydrogen evolution

Heteronanostructures(HNs)with precise components and interfaces are important for many applications,such as designing efficient and robust solar-to-fuel catalysts via integrating specific semiconductors with favorable band alignments.However,rationally endowing such features with rigorous framework control remains a synthetic bottleneck.Herein,we report a modular divergent creation of dual-cocatalysts integrated semiconducting sulfide nanotriads(NTds),comprising both isolated Pd_(x)S oxidation(ox)and MoS_(2) reduction(red)domains within each single CdS counterpart,which exhibit superior photocatalytic activity and stability for hydrogen evolution reaction(HER).The stepwise constructed Pd_(x)S_((ox))−CdS−MoS_(2(red)) NTds possess dualinterfaces facilitating continuous charge separation and segregated active sites accelerating redox reactions,respectively,achieving the HER rate up to 9 mmol·h^(−1)·g^(−1),which is about 60 times higher than that of bare CdS,and show no evidence of deactivation after long-term cycling.This design principle and transformation protocol provide predictable retrosynthetic pathways to HNs with increased degree of complexity and more elaborate functionalities that are otherwise inaccessible.

Resonant enhancement of second harmonic generation in etchless thin film lithium niobate heteronanostructure

Lithium niobate has received interest in nonlinear frequency conversion due to its wide transparency window,from ultraviolet to mid-infrared spectral regions,and large second-order nonlinear susceptibility.However,its nanostructure is generally difficult to etch,resulting in low-Q resonance and lossy nanostructures for second harmonic generation.By applying the concept of bound states in the continuum,we performed theoretical and experimental investigations on high-Q resonant etchless thin-film lithium niobate with Si O_(2) nanostructures on top for highly efficient second harmonic generation.In the fabricated nanostructured devices,a resonance with a Q factor of 980 leads to the strong enhancement of second harmonic generation by over 1500 times compared with that in unpatterned lithium niobate thin film.Although the pump slightly deviates from central resonance,an absolute conversion efficiency of 6.87×10^(-7) can be achieved with the fundamental pump peak intensity of 44.65 MW/cm^(2),thus contributing to the normalized conversion efficiency of 1.54×10^(-5)cm^(2)/GW.Our work establishes an etchless lithium niobate device for various applications,such as integrated nonlinear nanophotonics,terahertz frequency generation,and quantum information processing.