Plasmonic polydopamine-modified TiO_(2)nanotube substrates for surface-assisted laser desorption/ionization mass spectrometry imaging

Mass spectrometry imaging(MSI)has made the spatio-chemical characterization of a broad range of small-molecule metabolites within biological tissues possible.However,available matrix-assisted laser desorption/ionization mass spectrometry(MALDI-MS)suffers from severe background interferences in low-mass ranges and inhomogeneous matrix deposition.Thus,surface-assisted LDI-MS(SALDI-MS)has been an attractive alternative for high-sensitivity detection and imaging of small biomolecules.In this study,we construct a new composite substrate,hydrophobic polydopamine(hPDA)-modified TiO_(2)nanotube(TDNT)coated with plasmonic gold nanoparticle(AuNP-hPDA-TDNT),as a dual-polarity SALDI substrate using an easy and cost-effective fabrication approach.Benefitting from the synergistic effects of TDNT semiconductor and plasmonic PDA modification,this SALDI substrate exhibits superior performance for dual-polarity detection of a vast diversity of small molecules.Highly reduced background interferences,lower detection limits,and spot-to-spot repeatability can be achieved using AuNP-hPDA-TDNT substrates.Due to its unique imprinting performance,various metabolites and lipids can be visualized within jatropha integerrima petals,ginkgo leaves,strawberry fruits,and latent fingerprints.More valuably,the universality of this matrix-free substrate is demonstrated for mapping spatial distribution of lipids within mouse brain tissue sections.Considered together,this AuNP-hPDA-TDNT material is expected to be a promising SALDI substrate in various fields,especially in nanomaterial development and life sciences.

Recent Advances in Surface-Assisted Laser Desorption/Ionization Mass Spectrometry and Its Imaging for Small Molecules

Mass spectrometry imaging(MSI)has provided a new perspective on acquiring spatial information of multiple molecules in various samples.Among the different ionization methods,matrix-assisted laser desorption/ionization(MALDI)has been widely utilized for detecting macromolecules,with difficulty for small molecules(m/z<700 Da)due to the matrix interference or ionization suppression.In the past two decades,surface-assisted laser desorption/ionization mass spectrometry(SALDI-MS)gives rise to lots of attention on account of its unique performances,especially in untargeted analysis of small molecules.Selecting an appropriate substrate is a precondition for SALDI-MS and offers the possibility for SALDI-MS imaging(SALDI-MSI).In the last 5 years,different kinds of nanomaterials have been widely explored as substrates including metal/metal oxide-based,carbon-based,silicon-based,metal-organic frameworks-based,covalent organic frameworksbased substrates,with growing interests on composite materials and nanomaterials with homogeneous film structure.This review highlights recent advances of various nanomaterials as SALDI substrates,and their emerging imaging applications in botanic,forensic,metabolic and pathological fields.Finally,the merits and limitations of SALDI-MS are sketched out and some recommendations of this technique and its imaging are proposed.

Morphology-controlled Tantalum Diselenide Structures as Self-optimizing Hydrogen Evolution Catalysts

Metallic layered transition metal dichalcogenides(TMDs)nanomaterials based on Group 5 transition metals are attracting substantial interests as alternative catalysts for hydrogen evolution reaction(HER).However,controllable preparation of tantalum diselenide(TaSe2)remains challenging,which has hindered the exploration on its application in HER.Herein,we develop a facile method named surface-assisted chemical vapor transport(SACVT)for controllable synthesis of TaSe2 plates and nanobelts,by regulating the molar ratio of selenium to tantalum and reaction temperature.Unique quasi-arrays and self-supported structure help TaSe2 nanobelt own more active sites and higher ability of charge transfer,so it is superior to TaSe2 plate in electrocatalytic HER.Interestingly,they both exhibit the ability to optimize their morphologies upon cycling for dramatically improved and robust electrocatalytic performance.The selfoptimized structures can increase the effective active surface by exposing more active sites on the basal-planes and edges,shorten the interlayer electron-transfer pathways at a thinned domain,and accelerate the charge transfer,which mainly derive from high basal-plane activity and weak interaction between layers of metallic TaSe2.This work provides a reliable way for controllable synthesis of different TaSe2 structures,motivating further efforts to explore new high-efficiency catalysts in the large family of metallic TMDs for electrochemical energy conversion.

A highly efficient Fe-doped Ni_(3)S_(2) electrocatalyst for overall water splitting

The development of efficient and stable electrocatalysts with earth-abundant elements for both oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)in the same electrolyte is incontrovertibly vital in water electrolysis.However,their large-scale fabrication remains a great challenge.Here,we report a self-supported electrocatalyst in the form of Fe-doped Ni_(3)S_(2) nanoparticles in-situ grown on three-dimensional(3D)conductive Fe−Ni alloy foam(Fe−Ni_(3)S_(2)/AF)by surface-assisted chemical vapor transport(SACVT)method.Homogeneous growth environment and scalability of SACVT method allow Fe−Ni3S2 nanoparticles uniformly growing on AF in large-scale.Fe−Ni_(3)S_(2)/AF exhibits high activity and durability when act as HER catalyst and OER precatalyst in alkaline media.The HER and OER overpotential at 10 mA/cm^(2) is considerably small,only 75 and 267 mV,respectively.Moreover,the electrolyzer assembled by Fe−Ni_(3)S_(2)/AF for overall water splitting exhibits a low cell voltage and high durability in long-term test.Based on experiments and theoretical calculation,the significantly enhanced activity could be originated from the incorporation of Fe,which contributed to increase the electrochemical active surface area,enhance electrical conductivity,optimize the hydrogen and H2O adsorption energy of Ni_(3)S_(2)(101)surface in HER,and form active bimetallic Ni−Fe(oxy)hydroxide in OER.The excellent durability of self-supported Fe−Ni_(3)S_(2)/AF could be benefited from the in-situ growth of Fe−Ni_(3)S_(2) nanoparticles on 3D AF,which could ensure closely mechanical adhesion between active materials and substrate,promote charge transport and increase surface area.This work provides a facile method for large-scale synthesis of electrocatalysts with high activity and long-term durability for efficient water electrolysis in alkaline media.