Dissolution-Induced Surface Reconstruction of Ni0.95 Pt0.05 Si/p-Si Photocathode for Efficient Photoelectrochemical H2 Production.

Metal silicide/Si photoelectrodes have demonstrated significant potential for application in photoelectrochemical (PEC) water splitting to produce H2 . To achieve an efficient and economical hydrogen evolution reaction (HER), a paramount consideration lies in attaining exceptional catalytic activity on the metal silicide surface with minimal use of noble metals. Here, this study presents the design and construction of a novel Ni0.95 Pt0.05 Si/p-Si photocathode. Dopant segregation is used to achieve a Schottky barrier height as high as 1.0 eV and a high photovoltage of 420 mV. To achieve superior electrocatalytic activity for HER, a dissolution-induced surface reconstruction (SR) strategy is proposed to in situ convert surface Ni0.95 Pt0.05 Si to highly active Pt2 Si. The resulting SR Ni0.95 Pt0.05 Si/p-Si photocathode exhibits excellent HER performance with an onset potential of 0.45 V (vs RHE) and a high maximum photocurrent density of 40.5 mA cm-2 and a remarkable applied bias photon-to-current efficiency (ABPE) of 5.3% under simulated AM 1.5 (100 mW cm-2 ) illumination. The anti-corrosion silicide layer effectively protects Si, ensuring excellent stability of the SR Ni0.95 Pt0.05 Si/p-Si photoelectrode. This study highlights the potential for achieving efficient PEC HER using bimetallic silicide/Si photocathodes with reduced Pt consumption, offering an auspicious perspective for the cost-effective conversion of solar energy to chemical energy.

Tracking mitochondrial Cu(I) fluctuations through a ratiometric fluorescent probe in AD model cells: Towards understanding how AßOs induce mitochondrial Cu(I) dyshomeostasis.

Mitochondrial copper signaling pathway plays a role in Alzheimer's disease (AD), especially in relevant Amyloid-ß oligomers (AßOs) neurotoxicity and mitochondrial dysfunction. Clarifying the relationship between mitochondrial copper homeostasis and both of mitochondrial dysfunction and AßOs neurotoxicity is important for understanding AD pathogenesis. Herein, we designed and synthesized a ratiometric fluorescent probe CHC-NS4 for Cu(I). CHC-NS4 possesses excellent ratiometric response, high selectivity to Cu(I) and specific ability to target mitochondria. Under mitochondrial dysfunction induced by oligomycin, mitochondrial Cu(I) levels gradually increased, which may be related to inhibition of ATP7A-mediated Cu(I) exportation and/or high expression of COX. On this basis, CHC-NS4 was further utilized to visualize the fluctuations of mitochondrial Cu(I) levels during progression of AD model cells induced by AßOs. It was found that mitochondrial Cu(I) levels were gradually elevated during the AD progression, which depended on not only AßOs concentration but also incubation time. Moreover, endocytosis maybe served as a prime pathway mode for mitochondrial Cu(I) dyshomeostasis induced by AßOs during AD progression. These results have provided a novel inspiration into mitochondrial copper biology in AD pathogenesis.

Photoelectrocatalytic Utilization of CO2 : A Big Show of Si-based Photoelectrodes.

CO2 is a greenhouse gas that contributes to environmental deterioration; however, it can also be utilized as an abundant C1 resource for the production of valuable chemicals. Solar-driven photoelectrocatalytic (PEC) CO2 utilization represents an advanced technology for the resourcing of CO2 . The key to achieving PEC CO2 utilization lies in high-performance semiconductor photoelectrodes. Si-based photoelectrodes have attracted increasing attention in the field of PEC CO2 utilization due to their suitable band gap (1.1 eV), high carrier mobility, low cost, and abundance on Earth. There are two pathways to PEC CO2 utilization using Si-based photoelectrodes: direct reduction of CO2 into small molecule fuels and chemicals, and fixation of CO2 with organic substrates to generate high-value chemicals. The efficiency and product selectivity of PEC CO2 utilization depends on the structures of the photoelectrodes as well as the composition, morphology, and size of the catalysts. In recent years, significant and influential progress has been made in utilizing Si-based photoelectrodes for PEC CO2 utilization. This review summarizes the latest research achievements in Si-based PEC CO2 utilization, with a particular emphasis on the mechanistic understanding of CO2 reduction and fixation, which will inspire future developments in this field.

Amorphous Ni-Mo-B-O Bifunctional Electrocatalyst for Simultaneous Production of Hydrogen and Value-added Chemicals.

Hydrogen evolution reaction (HER) coupled with biomass conversion is a sustainable route to produce clean energy H2 and value-added chemicals simultaneously. Herein, an amorphous Ni-Mo-B-O bifunctional electrocatalyst was synthesized through a facile electrodeposition method and employed as a cathode for HER to produce H2 and as an anode for the conversion of hydroxymethylfurfural (HMF) to furandicarboxylic acid (FDCA). Besides leading to the formation of amorphous structures, the introduction of Mo and B can increase the electron density and optimize the electronic structure of the electrocatalyst, thus substantially increasing the catalytic activity of the catalyst. After continuous reaction at a constant potential of 0.58 V vs. Hg/HgO for 8 hours, the conversion of HMF reached 98.86 %, and the selectivity of the target product FDCA was as high as 92.97 %. Finally, a two-electrolyzer system was constructed using the amorphous Ni-Mo-B-O as both cathode and anode to achieve simultaneous H2 production in the cathode chamber and FDCA production in the anode chamber at a low voltage. This work presents a promising strategy for the design and synthesis of high-performance non-noble metal electrocatalysts for efficient and cost-effective H2 production.

Fluorescence Enhancement Method for Aptamer-Templated Silver Nanoclusters and Its Application in the Construction of a ß-Amyloid Oligomer Sensor.

DNA-templated silver nanoclusters (DNA-AgNCs) have attracted significant attention due to their unique fluorescence properties. However, so far, the relatively low quantum yields of the DNA-AgNCs and the complex design of DNA-AgNC-based sensors have limited their application in biosensing or bioimaging. Herein, we report a novel fluorescence enhancement method. The ß-Amyloid Oligomer (AßO) aptamer (AptAßO) with A10/T10 at its 3' end can be directly used as the template to fabricate the AgNCs. When the AgNCs were hybridized with the complementary strand that has 12 bases suspended at its 3' terminal, being the same or complementary to the A/T at the 3' end of the AptAßO, and two-base mismatches in the complementary region of the aptamer excluded A10/T10, a dramatic fluorescence enhancement (maximum: ∼500-fold; maximum quantum yield: 31.5%) can be realized. The fluorescence enhancement should result from the aggregation-induced emission of the AgNCs, which can be attributed to forming the reticular structure of the hybridized product. To some extent, the method developed in this work is extendable. The fluorescence enhancement was also realized from the thrombin aptamer-templated AgNCs through designing the aptamer and the corresponding complementary strand according to the method. Based on the fluorescence enhancement of the AptAßO-templated AgNCs, an "on-off" fluorescence sensor was constructed for the sensitive and selective detection of AßO. This work provides a rational strategy to realize fluorescence enhancement for the aptamer-templated AgNCs and design an aptamer-based fluorescence sensor.

Single nanowire-based fluorescence lifetime thermometer for simultaneous measurement of intra- and extra-cellular temperatures.

A silicon nanowire-based fluorescence lifetime thermometer (NWFLT) was fabricated for the simultaneous measurement of intra- and extra-cellular temperatures. Using the NWFLT, an obvious heterogeneity of the temperature was found along the longitude direction of the NWFLT, especially between the inside and outside of the cell.

Simultaneous Monitoring of the Adenosine Triphosphate Levels in the Cytoplasm and Nucleus of a Single Cell with a Single Nanowire-Based Fluorescent Biosensor.

Simultaneous monitoring of the ATP levels at various sites of a single cell is crucial for revealing the ATP-related processes and diseases. In this work, we rationally fabricated single nanowire-based fluorescence biosensors, by which the ATP levels of the cytoplasm and nucleus in a single cell can be simultaneously monitored with a high spatial resolution. Utilizing the as-fabricated single nanowire biosensor, we demonstrated that the ATP levels of the cytoplasm were around 20-30% lower than that of the nucleus in both L929 and HeLa cells. Observing the ATP fluctuation of the cytoplasm and nucleus of the L929 and HeLa cells stimulated by Ca2+, oligomycin, or under cisplatin-induced apoptosis, we found that the ATP levels at two cellular sites exhibited discriminative changes, revealing the different mechanisms of the ATP at these two cellular sites in response to the stimulations.

Ultrahigh Modulation Enhancement in All-Optical Si-Based THz Modulators Integrated with Gold Nanobipyramids.

Optical regulation strategy with the aid of hybrid materials can significantly optimize the performance of terahertz devices. Gold nanobipyramids (AuNBPs) with synthetical tunability to the near-infrared band show strong local field enhancement, which improves optical coupling at the interface and benefits the modulation performance. We design AuNBPs-integrated terahertz modulators with multiple structured surfaces and demonstrate that introducing AuNBPs can effectively enhance their modulation depths. In particular, an ultrahigh modulation enhancement of 1 order of magnitude can be achieved in the AuNBPs hybrid metamaterials accompanied by the multifunctional modulation characteristics. By application of the coupled Lorentz oscillator model, the theoretical calculation suggests that the optical regulation with AuNBPs originates from increased damping rate and higher coupling coefficient under pump excitation. Additionally, a terahertz spatial light modulator is constructed to demonstrate multiple imaging display and consume extremely low power, which is promising for the potential application in spatial and frequency selective imaging.

Sensitive and Stable Thermometer Based on the Long Fluorescence Lifetime of Au Nanoclusters for Mitochondria.

Detecting the temperature of intracellular mitochondria with high sensitivity and stability is crucial to understanding the cellular metabolism and revealing the processes of mitochondria-related physiology. In this paper, employing the long fluorescence lifetime of modified Au nanoclusters (mAuNCs) by 4-(carboxybutyl) triphenylphosphonium bromide, we developed a fluorescence lifetime thermometer with high sensitivity and stability for the temperature of the intracellular mitochondria. A high relative temperature sensitivity of 2.8% and excellent photostability were achieved from the present thermometer. After incubation with L929 cells, the mAuNCs could be endocytosed into the cells and targeted the mitochondria, and the temperature changes at the L929 cells' mitochondria, which were stimulated by carbonyl cyanide 3-chlorophenylhydrazone and Ca2+, were successfully detected via the fluorescence lifetime images of the mAuNCs. Furthermore, utilizing the mAuNCs, we clarified the effect of Mg2+ on the temperature of the intracellular mitochondria. The strategy of employing a material with a long fluorescence lifetime and remarkable stability to fabricate the fluorescence lifetime thermometer for mitochondria can be used to design various thermometers for other organelles.

A general configurational strategy to quencher-free aptasensors.

The aptasensor, developed from the aptamer, has aroused wide concern in recent years owing to its high sensitivity and specificity. However, the quenching unit involved in the most of the aptasensors is indispensable to the fabrication of an aptasensor, which would undoubtedly increase the complexity of the device. In this study, a facile strategy was developed for construction of the quencher-free aptasensors, in which the quenching units can be omitted, and only an aptamer strand and a fluorophore are necessary. Distinguishable from the configuration of the traditional ones, the aptasensors developed in this work rationally employed the intrinsic quenching abilities of the analytes to directly regulate the fluorescence of the fluorophore. Furthermore, the aptamer strand as a discriminatory unit efficiently captured the corresponding analytes to around the fluorophores. As a result, the fluorescence of the aptasensor can be significantly sensitive to the analytes. The generality of the current design is evidenced by the successful fabrication of seven quencher-free aptasensors for Cu2+, Ag+, Hg2+, ATP and dopamine through 6-FAM labeling aptamers of Cu2+, Ag+, Hg2+, ATP, dopamine, 5-TAMRA and ROX labeling aptamers of Cu2+. Present strategy endows an aptasensor with a simple structure, high selectivity and fine sensitivity. The configuration of the quencher-free aptasensors fabricated in this work can be readily utilized for more aptasensors.

Metal Silicidation in Conjunction with Dopant Segregation: A Promising Strategy for Fabricating High-Performance Silicon-Based Photoanodes.

Silicon (Si)-based Schottky junction photoelectrodes have attracted considerable attention for photoelectrochemical (PEC) water splitting in recent years. To realize highly efficient Si-based Schottky junction photoelectrodes, the critical challenge is to enable the photoelectrodes to not only have a high Schottky barrier height (SBH), by which a high photovoltage can be obtained, but also ensure an efficient charge transport. Here, we propose and demonstrate a strategy to fabricate a high-performance NiSi/n-Si Schottky junction photoanode by metal silicidation in conjunction with dopant segregation (DS). The metal silicidation produces photoanodes with a high-quality NiSi/Si interface without a disordered SiO2 layer, which ensures highly efficient charge transport, and thus a high saturated photocurrent density of 33 mA cm-2 was attained for the photoanode. The subsequent DS gives the photoanodes a high SBH of 0.94 eV through the introduction of electric dipoles at the NiSi/n-Si interface. As a result, a high photovoltage and favorable onset potential of 1.03 V vs RHE was achieved. In addition, the strong alkali corrosion resistance of NiSi also endows the photoanode with a high stability during PEC operation in 1 M KOH. Our work provides a universal strategy to fabricate metal-silicide/Si Schottky junction photoelectrodes for high-performance PEC water splitting.

Robust liquid-core nanocapsules as biocompatible and precise ratiometric fluorescent thermometers for living cells.

Intracellular thermometry with favorable biocompatibility and precision is essential for insight into temperature-related cellular events. Here, liquid-core nanocapsule ratiometric fluorescent thermometers (LCN-RFTs) were prepared by encapsulating thermosensitive organic fluorophores (N,N'-di(2-ethylhexyl)-3,4,9,10-perylene tetracarboxylic diimide, DEH-PDI) with hydrophobic solvent (2,2,4-trimethylpentane, TMP) into polystyrene/silica hybrid nanoshells. As the fluorescent thermosensitive unit of the LCN-RFT, the TMP solution of DEH-PDI was responsible for the fluorescence response to temperature. Benefitting from the hydrophilic nanoshells, the LCN-RFTs exhibited favorable anti-interference and biocompatibility. Furthermore, the LCN-RFTs showed an excellent precision of 0.02 °C-0.10 °C in a simulated physiological environment from 10.00 °C to 90.00 °C, and were employed to realize intracellular thermometry with an outstanding precision of 0.06 °C-0.14 °C. This work provides a feasible method of using hydrophobic organic fluorophores for intracellular thermometry by encapsulating them into nanocapsules.

A Single Silicon Nanowire-Based Ratiometric Biosensor for Ca2+ at Various Locations in a Neuron.

Ionic calcium (Ca2+) is an important second messenger in cells, particularly in the neuron. A deficiency or excess of Ca2+ would lead to neuronal apoptosis and further injury to the brain. For accurate analysis of intracellular Ca2+, a single silicon nanowire (SiNW)-based ratiometric biosensor was constructed by simultaneously anchoring Ru(bpy)2(mcbpy-O-Su-ester)(PF6)2, as a reference molecule, and Fluo-3, as a response molecule, onto the surface of a single SiNW. The SiNW-based biosensor exhibits high sensitivity and favorable selectivity for detecting Ca2+. With the assistance of a micromanipulator and laser scanning confocal microscope, two single SiNW sensors were placed in the body and the neurites of an individual neuron to detect Ca2+. The difference between the concentrations of Ca2+ in the body and neurites was identified. The results from the present study provide new insights into Ca2+ in neurons at a high spatial resolution, and the strategy used in this study provides a new opportunity to investigate cellular metabolism by combining the advantages of a single-cell detection technique and physiology.

An ultrasensitive ratiometric fluorescent thermometer based on frustrated static excimers in the physiological temperature range.

A ratiometric fluorescent thermometer (RFT) based on the frustrated static excimers (FSEs) of DEH-PDI (N,N'-di(2-ethylhexyl)-3,4,9,10-perylenetetracarboxylic diimide) was designed and synthesized. The RFT exhibited ultrahigh sensitivities, which far exceed the existing RFTs in the physiological temperature range. The RFT also showed outstanding precisions, stability, and an obvious thermochromism in the temperature range.

Bifunctional Gold Nanobipyramids for Photothermal Therapy and Temperature Monitoring.

To realize a real-time thermal feedback, monitoring the temperature of the treated tissue is critical for photothermal therapy (PTT). The poor spatial resolution and low accuracy of current methods for the detection of tissue temperature limits the application of PTT. Herein, by assembling the temperature-responsive DNA stem-loop marked with Texas red (TR) onto the surface of gold nanobipyramids (AuNBPs), a bifunctional reagent (AuNBPs-DNA-TR) was fabricated for PTT and synchronously monitoring the temperature. In this configuration, the AuNBPs not only have a high efficiency for photothermal conversion but also could be quenchers to inhibit the fluorescence of TR. During PTT, the significant photothermal effect of the AuNBPs could elevate the temperature. Meanwhile, the increase of the temperature could open the DNA stem-loop assembled on the AuNBPs and as a result enlarge the distance between the TR and AuNBPs. As a result, the TR fluorescence quenched by the AuNBPs was sensitively recovered. The fluorescence intensity (FI) of the TR could be utilized to monitor the temperature during PTT. It was found that irradiating the cancer cells cultured with the AuNBPs-DNA-TR with an 808 nm laser could distinctly increase the system temperature, while the cells could be inactivated due to the remarkable photothermal effect of the AuNBPs-DNA-TR. Meanwhile, the fluorescence of the AuNBPs-DNA-TR for the measurement of the temperature was significantly enhanced. The results indicated that the variation of the fluorescence from the AuNBPs-DNA-TR could be used as thermal feedback to monitor the effect of PTT.

Silver Nanowire-Based Fluorescence Thermometer for a Single Cell.

A fluorescence thermometer based on silver nanowires (AgNWs) is realized by assembling Texas Red (TR)-marked thermal-sensitive DNA stem-loops (TR-DNA stem-loop) on the surface of AgNWs. Temperature configures the structure of the TR-DNA stem-loop and resultantly adjusts the energy transfer between TR and the AgNWs, which could sensitively control the fluorescence intensity of the thermometer. The thermometer is sensitive to the temperature ranging from 30 to 40 °C with the sensitivity of 2.6%/°C. Under the assistance of laser confocal microscopy, a temperature change within a single cell was observed by the monofilament AgNW-based thermometer.

DNA nanostructure-based fluorescence thermometer with silver nanoclusters.

DNA nanostructure-based fluorescence thermometers were fabricated by linking fluorescent silver nanoclusters (AgNCs) and guanine-rich（G-rich）DNA chains via a thermally sensitive DNA stem-loop at terminals 5' and 3'. Variations of temperature alter the distance between the AgNCs and G-rich DNA chain, affecting the interaction between them. As a result, the intensity of fluorescence emission from the AgNCs at 636 nm can be sensitively modulated. It was found that the intensity of such red emission is more temperature sensitive than the equivalent green emission at 543 nm; sensitivity of -3.6%/°C was achieved. Through variation of the melting temperature of the DNA stem-loop, the response temperature range of the thermometers could be readily adjusted. Novel DNA nanostructure-based fluorescence thermometers as described in this work are anticipated to be able to measure the temperature of biological systems at small scales-even a single cell.

Enhancing the Photovoltage of Ni/ n-Si Photoanode for Water Oxidation through a Rapid Thermal Process.

The Ni in the Ni/ n-Si photoanode can not only protect Si from corrosion, but also catalyze the water oxidation reaction. However, the high density of interface states at the Ni/ n-Si interface could pin the Fermi level of silicon, which will lower the Schottky barrier height of the Ni/ n-Si. As a result, a low photovoltage and consequent high onset potential of Ni/ n-Si photoanode for water oxidation were generated. In this study, the interfacial states of the Ni/ n-Si photoanodes were efficiently diminished through a rapid thermal process (RTP). Calculated from the Mott-Schottky plots, the Schottky barrier height of Ni/ n-Si was increased from 0.58 to 0.78 eV after RTP. Under the illumination of 100 mW cm-2 of the Xe lamp, the onset potential of the Ni/ n-Si photoanode for water oxidation was negatively shifted for 150 mV after RTP. Besides, the RTP-treated Ni/ n-Si photoanode exhibited a high stability during the PEC water oxidation of 8 h in 1 M KOH solution.

Si-H induced synthesis of Si/Cu2O nanowire arrays for photoelectrochemical water splitting.

We report a facile and low-cost method to synthesize Si/Cu2O heterojunction nanowire arrays, without SiOx, at the Si/Cu2O interface. The reductive Si-H bonds on the surface of Si nanowires plays a key role in situ by reducing Cu(II) ions to Cu2O nanocubes and avoiding the SiOx interface layer. Different pH values would vary the electrochemical potential of reactions and as a result, different products would be formed. Utilized as a photoanode for water splitting, Si/Cu2O nanowire arrays exhibit good photoelectrochemical performance.

The Formation of Defect-Pairs for Highly Efficient Visible-Light Catalysts.

Highly efficient visible-light catalysts are achieved through forming defect-pairs in TiO2 nanocrystals. This study therefore proposes that fine-tuning the chemical scheme consisting of charge-compensated defect-pairs in balanced concentrations is a key missing step for realizing outstanding photocatalytic performance. This research benefits photocatalytic applications and also provides new insight into the significance of defect chemistry for functionalizing materials.