Latest ArticlesThe exploration of novel photo/thermal-responsive nonvolatile memorizers will be beneficial for energy-saving memories. Herein, new <110> -oriented perovskites using single template melamine, i.e., [(MLAI-H2)(PbX4)] (X = Br (α-1), Cl (α-2), MLAI = melamine) have been prepared and their structures upon irradiation of visible light have been investigated. They have been fabricated as nonvolatile memory devices with structures of ITO/[(MLAI-H2)(PbX4)]/PMMA/Ag (device-1: X = Br, device-2: X = Cl), which can exhibit unique visible light-triggered binary nonvolatile memory performances. Interestingly, the silent or working status can be monitored by visible chromisms. Furthermore, the light-triggered binary resistive switching mechanisms of these ITO/[(MLAI-H2)(PbX4)]/PMMA/Ag memory devices have been clarified in terms of EPR, fluorescence, and single-crystal structural analysis. The presence of light-activated traps in <110> -oriented [(MLAI-H2)(PbX4)] perovskites are dominated in the appearance of light-triggered resistive switching behaviors, based on which the inverted internal electrical fields can be established. According to the structural analysis, the more distorted PbX6 octahedra, higher corrugated <110> -oriented perovskite sheets, and more condensed organic-inorganic packing in Br-containing perovskite are beneficial for the stabilization of light-activated traps, which lead to the better resistive switching behavior of device-1. This work can pave a new avenue for the establishment of novel energy-saving nonvolatile memorizers used in aerospace or military industries.
Many evolved biomolecular functions such as ion pumping or redox catalysis rely on controlled charge transport through the polypeptide matrix, which can be regulated by shifts in molecular protonation states and dependent supramolecular packing modes in response to environmental cues. However, the exact roles of such dynamic, non-covalent interactions in peptide charge transport have remained elusive. To tackle this challenge, here we report the modulation of charge transport in a series of lysine (Lys)-substituted hepta-glycine (Gly) peptide self-assembled monolayers (SAMs) on template-striped gold (AuTS) bottom electrodes with eutectic gallium-indium (EGaIn) liquid metal top electrodes. We demonstrate systematic modulation of hydrogen bonding and more general electrostatic interactions by shifting the position of the charged Lys-residue and creating different protonation patterns by changing the environmental pH in the AuTS/peptide//GaOx/EGaIn junctions. The effective modulation is evidenced by current density–voltage (J-V) measurements combined with SAM characterization using ultraviolet photoelectron spectroscopy (UPS) and angle-resolved X-ray photoelectron spectroscopy (ARXPS), polarization modulation–infrared reflection-absorption spectroscopy (PM-IRRAS), and molecular dynamics (MD) simulations. Decreasing the hydrogen bonding inside the peptide SAMs and increasing the electrostatic interactions by environmental counterions amplifies the charge transport differently with Lys-position, which means that the sensitive electrical response of peptide SAMs can be tuned by the peptide sequence. Our results provide insights into the relationship between molecular design and in situ modulation of charge transport properties for the development of bionanoelectronics.
Metal-organic frameworks (MOFs) with large specific surface area, considerable pore volume, controllable structure, and high concentration of active metal sites have been applied widely in researches like catalysis and sensing. However, potential applications of MOFs in both photocatalysis and luminescence sensors are facing major challenges arising from their severe charge recombination, low utilization of solar energy, low quantum yield, limited charge transfer between the metal ions/clusters and the ligand. Recent studies revealed that rational introduction of carbon dots (CDs) with excellent optical properties, unique quantum confinement and high conductivity can greatly enhance the functions of MOFs. In this paper, typical synthesis methods of these CD-MOF composites as well as their potential applications in photocatalysis and sensing are reviewed with emphasis. Representative examples of these CD-MOF composites are discussed, and key features and advantages of CD-MOF composites that will facilitate future applications are highlighted.
In-situ monitoring of neurochemicals is of vital importance for the understanding of brain functions. Microelectrode-based photoelectrochemical (PEC) sensing has emerged as a promising tool for in vivo analysis since it inherits the merits of both optical and electrochemical methods. However, the in-situ excitation of photoactive materials on the photoelectrode in living body is still a challenge because of limited tissue penetration depth of light. To circumvent this problem, we herein developed an implantable optical fiber (OF)-based microelectrode for in vivo PEC analysis. The working electrode was constructed by coating Au film as conducting layer and CdS@ZnO as photoactive material on a micron-sized OF, which was free of the limitation of light penetration in biological tissues. Further decoration of an anti-biofouling layer on the surface made the sensor robust in biosamples. It was successfully applied for monitoring Cu2+ level in three different brain regions in the rat model of cerebral ischemia/reperfusion.
Devising a desirable adsorbent for efficiently selective capture of Ag(Ⅰ) from wastewater has attracted much attention but faced with huge challenges. Herein, a novel linear o-phenanthroline-based polymer l-PRL was prepared via chemical oxidative polymerization for the adsorption of Ag(Ⅰ). The maximum adsorption capacity for Ag(Ⅰ) by l-PRL is 325.8 mg/g at pH 0. In addition, l-PRL owes ascendant selectivity for Ag(Ⅰ) from aqueous solutions containing various interfering metal ions of Pb(Ⅱ), Co(Ⅱ), Ni(Ⅱ), Cd(Ⅱ) and Fe(Ⅲ). Multiple characterizations of FT-IR and XPS uncover that the N groups on l-PRL act as adsorption sites to coordinate with Ag(Ⅰ). Density functional theory (DFT) calculations further evidence the mechanism that l-PRL is provided with the admirable adsorptivity and selectivity for Ag(Ⅰ). It is mainly attributed to the most stable complexes of l-PRL with Ag(Ⅰ), which possesses shortest Ag-N bond length compared with other heavy metal ions. Furthermore, 93.5% of initial adsorption capacity is reserved after four continuous regeneration cycles, indicating that l-PRL is equipped with superior recyclability and durability, and l-PRL is capable of removing Ag(Ⅰ) in low-concentration actual Ag(Ⅰ)-containing wastewater completely. This study shed light on the rational design of polymer adsorbents and in-depth insight into selective removal of aqueous Ag(Ⅰ).
There is no clear consensus regarding how cells respond to hydrostatic pressure. This is largely attributable to the high heterogeneity among cell types and the diverse custom-made devices used in previous studies. The aim of this work was to develop a facile device that could mimic various pressure environments and then delineate the cellular response to pressure stimulus. The device described here achieved both stable and periodic pressurization without oxygen deprivation. The biological utility of the device was assessed using human umbilical vein endothelial cells. We found more stereoscopic nuclear morphology and re-distribution of lamin A/C under high hydrostatic pressure compared to control cells. Mass spectrometry-based proteomics analysis showed significant changes in mitochondria-related pathways. Western blot analysis confirmed that high hydrostatic pressure induced a tendency toward mitochondrial fusion. Increased mitochondrial activity was observed as well. In conclusion, this device can be readily applied in biological research and extend our understanding of cellular mechano-sensation and the associated changes in mitochondrial behaviors.
The regulation of the basic properties of atom-economic catalysts at the atomic scale and atomic-level insights into the underlying mechanism of catalysis are less explored. We engineer the surface of vertical immobilized MoS2 on dispersible TiO2 nanofibers via atomic subtraction to precisely manipulate active sites at the atomic level. The photocatalytic performances of TiO2@MoS2 after H2 reduction towards the hydrogen production under visible light irradiation (> 420 nm) are about 4 times that of TiO2@MoS2 before H2 reduction. Importantly, the enhanced stability of TiO2@MoS2 lasts for at least 30 h. Promising catalytic activity that is attributed to omnidirectional exposed active sites located defects, edges, corners that are transformed from the subtractive atomic sites could be exhumed comprehensively. This work will provide an intriguing and effective approach on tuning electronic structures for optimizing the catalytic activity at the atomic level by atom elimination strategy. To get rid of a few atomics on the surface of atomically-thin MoS2 nanosheet could be a prudent avenue for enabling the basal plane of MoS2 catalytically active.
Although many plasmonic nanosenosrs have been established for the detection of mercury(Ⅱ) (Hg2+), few of them is feasible for analyzing natural samples with very complex matrices because of insufficient method selectivity. To address this challenge, we propose an epitaxial and lattice-mismatch approach to the synthesis of a unique Au/Ag2S dimeric nanostructure, which consists of an Au segment with excellent plasmonic characteristics, and a highly stable Ag2S portion with minimum solubility product (Ksp(Ag2S) = 6.3 × 10−50). The detection relies on the chemical conversion of Ag2S to HgS when reacting with Hg2+, resulting in a red shift in the absorption band of the connecting Au NPs. The concurrent color changes of the solution from gray purple to dark green and finally to navy correlate well with Hg2+ concentration, thus enables UV–vis quantitation and a naked-eye readout of the Hg2+ concentration. This method exhibits superior selectivity towards Hg2+ over other interfering ions tested because Hg2+ is the only ion that can react with Ag2S to form HgS with even smaller solubility product (Ksp(HgS) = 4 × 10−53). The detection limit of this method is 1.21 µmol/L, calculated by the signal-to-noise of 3. The practicability of the method was verified by analyzing the Hg2+ in sewage water samples without sample pretreatment with satisfactory recoveries (93.1%-102.8%) and relative standard deviations (1.38%-2.89%). We believe this method holds great potential for on-the-spot detection of Hg2+ in environmental water samples with complex matrices.
A variety of luminol derivatives with N- and O-substitution have been synthesized with broad functional group tolerance. O-esterification has been demonstrated for the first time as a promising way to prepare enhanced CL reagents for sensing hemin, bloodstain and horseradish peroxidase (HRP). The most effective analogue with a deuterated acetyl group exhibited greater potential than luminol for bloodstain imaging and HRP imaging in western blotting (WB). In addition, O-etherification can greatly suppress CL signal that has been applied to design a CL probe for β-glucosidase (β-Glu). This study offers important and useful information regarding the luminol modification and shows great potential to use O-substituted analogues for enhanced CL analysis.
Hydrophilic interaction liquid chromatography (HILIC) has been recognized as an effective strategy for glycopeptide enrichment. Hydrophilic materials pave the way to solve the limit of low enrichment capacity and poor selectivity. The present study is the first attempt to combine chitosan (CS) and L-cysteine (L-Cys) to design a novel hydrophilic material focusing on glycopeptide enrichment. CS containing a large number of hydrophilic amino and hydroxyl groups has unique chemical properties, which makes it a very attractive biomaterial for glycopeptide enrichment. The excellent hydrophilicity of zwitterionic molecule L-Cys inspires the idea of anchoring L-Cys onto CS to design a novel hydrophilic material (named as Fe3O4@CS@Au-L-Cys) for the capture of low abundance glycopeptides. To be specific, Au nanoparticles (Au NPs) was introduced into CS-coated Fe3O4 via electrostatic interaction and served as bridges to anchor L-Cys onto the surface of CS through strong Au-S bond interaction. The prepared Fe3O4@CS@Au-L-Cys exhibited strong affinity, low detection limit (0.5 fmol/µL HRP), high selectivity (HRP/BSA with a molar ratio of 1:1000) for glycopeptides. Moreover, successful application of glycopeptide enrichment in human serum and saliva by Fe3O4@CS@Au-L-Cys was achieved. A satisfactory data set indicates that Fe3O4@CS@Au-L-Cys has promising potential in the application of glycopeptide enrichment in real complex bio-samples and for related glycoproteome research.
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