Dual Enzyme-Locked Activation Reporter for Accurate Liver Cancer Surveillance.

Activatable probes with a higher signal-to-background ratio and accuracy are essential for monitoring liver cancer as well as intraoperative fluorescence navigation. However, the presence of only one biomarker is usually not sufficient to meet the high requirement of a signal-to-background ratio in cancer surveillance, leading to the risk of misdiagnosis. In this work, a dual-locked activation response probe, Si-NTR-LAP, for nitroreductase and leucine aminopeptidase was reported. This dual-locked probe provides better tumor recognition and a higher signal-to-noise ratio than that of single-locked probes (Si-LAP and Si-NTR). In both the subcutaneous tumor model and the more complex orthotopic hepatocellular carcinoma model, the probe was able to identify tumor tissue with high specificity and accurately differentiate the boundaries between tumor tissue and normal tissue. Therefore, the dual-locked probe may provide a new and practical strategy for applying to real patient tumor tissue samples.

Wet Film Leveling for Promoting the Uniformity and Conductivity of Silver Nanowire Transparent Electrode.

Wet film leveling can greatly promote film uniformity. However, in the field of metal nanowire, wet film leveling is rarely mentioned. For low-viscosity inks like metal nanowire ink, how to realize wet film leveling is still unclear. Herein, we study the wet film leveling of silver nanowire ink and systematically investigate the relationship between leveling effect and influence factors: (1) there is a uniformity-promotion limit for traditional methods, while wet film leveling can break through this limit and further promote the film uniformity; (2) for wet film leveling, lowering ink's surface tension has no effect, and eliminating surface tension gradient by high-surface-tension leveling agent is the main task; (3) leveling process includes wet film destruction process and ink reflow process; (4) in the destruction process, the leveling-agent solubility and quantity dominate the leveling effect, while the influence of surface tension is little; (5) for solubility and quantity, there is a suitable range to realize optimum leveling effect, and the leveling effect exhibits a contrary relationship with the solubility in a suitable range (2-11%); (6) in the reflow process, the main influence factor is ink viscosity, and the leveling effect exhibits a contrary relationship with ink viscosity. After being leveled by 1.5% n-pentanol, the sheet resistance and sheet-resistance variation coefficient of film decrease from 38.3 Ω/sq/3.83% to 25.7 Ω/sq/1.88%. Further study reveals that the film improvement is not from the ink wettability and drying. Above theoretical results possess certain universality for film preparation by a wet process and can be used by the science and industry field.

Three-Dimensional Porous Indium Single-Atom Catalysts with Improved Accessibility for CO2 Reduction to Formate.

Single-atom catalysts (SACs) present substantial potential in electrocatalytic CO2 reduction reactions; however, inferior accessibility of single-atom sites to CO2 limits the overall CO2RR performances. Herein, we propose to improve the accessibility between In sites and CO2 through the construction of a three-dimensional (3D) porous indium single-atom catalyst (In1/NC-3D). The NaCl template-mediated synthesis strategy generates the unique 3D porous nanostructure of In1/NC-3D. Multiple characterizations validate that In1/NC-3D exhibits increased exposure of active sites and enhanced CO2 transport/adsorption capacity compared to the bulk In1/NC, thus improving accessibility of active sites to CO2. As a result, the In1/NC-3D presents superior CO2RR performance to the bulk In1/NC, with a partial current density of formate of 67.24 mA cm-2 at -1.41 V, relative to a reversible hydrogen electrode (vs RHE). The CO2RR performances with high formate selectivity at a large current density also outperform most reported In-based SACs. Importantly, the In1/NC-3D is demonstrated to maintain an FEformate of >82% at -66.83 mA·cm-2 over 21 h. This work highlights the design of a 3D porous single-atom catalyst for efficient CO2RR, promoting the development of advanced catalysts toward advanced energy conversion.

Identification and quantification of N6-methyladenosine by chemical derivatization coupled with 19F NMR spectroscopy.

N 6-Methyladenosine (6mA) is a well-known prokaryotic DNA modification that has been shown to play epigenetic roles in eukaryotic DNA. Accurate detection and quantification of 6mA are prerequisites for molecular understanding of the impact of 6mA modification on DNA. However, the existing methods have several problems, such as high false-positive rate, time-consuming and complex operating procedures. Chemical sensors for the selective detection of 6mA modification are rarely reported in the literature. Fluorinated phenylboronic acid combined with 19F NMR analysis is an effective method for determining DNA or RNA modification. In this study, we presented a simple and fast chemical method for labelling the 6th imino group of 6mA using a boric-acid-derived probe. Besides, the trifluoromethyl group of trifluoromethyl phenylboronic acid (2a) could detect 6mA modification through 19F NMR. Combined with this sensor system, 6mA modification could be detected well and quickly in 6 types of deoxynucleoside mixtures and DNA samples. Taken together, the method developed in the current study has potential for specific detection of 6mA in biological samples.

Improving Photophysical Properties and Hydrophily of Conjugated Polymers Simultaneously by Side-Chain Modification for Near-Infrared Cell Imaging.

Conjugated polymers (CPs)-based near-infrared phototheranostics are receiving increasing attention due to their high molar extinction coefficient, wide emission wavelength, easy preparation and excellent biocompatibility. Herein, several new conjugated polymers with D2-D1-A structures were easily prepared through one-pot coupling using triphenylamine (D2) as well as thiophenes (D1) as electron donors and benzothiadiazole (A) as electron acceptors. Interesting, their optical performance and power conversion efficiency could be tuned by side chains on thiophenes (D1). The introduction of ethylenedioxy into D1 as side chain significantly improves fluorescence imaging brightness, photothermal conversion efficiency and hydrophilicity, and extends emission wavelength, which are beneficial for phototheranostic. The side chain modification provides new opportunity to design efficient phototheranostics without construction new fluorescent skeletons.

Coupling Nano and Atomic Electric Field Confinement for Robust Alkaline Oxygen Evolution.

The alkaline oxygen evolution reaction (OER) is a promising avenue for producing clean fuels and storing intermittent energy. However, challenges such as excessive OH- consumption and strong adsorption of oxygen-containing intermediates hinder the development of alkaline OER. In this study, we propose a cooperative strategy by leveraging both nano-scale and atomically local electric fields for alkaline OER, demonstrated through the synthesis of Mn single atom doped CoP nanoneedles (Mn SA-CoP NNs). Finite element method simulations and density functional theory calculations predict that the nano-scale local electric field enriches OH- around the catalyst surface, while the atomically local electric field improves *O desorption. Experimental validation using in situ attenuated total reflection infrared and Raman spectroscopy confirms the effectiveness of the nano-scale and atomically electric fields. Mn SA-CoP NNs exhibit an ultra-low overpotential of 189 mV at 10 mA cm-2 and stable operation over 100 hours at ~100 mA cm-2 during alkaline OER. This innovative strategy provides new insights for enhancing catalyst performance in energy conversion reactions.

Design and implementation of a dual aspheric integrated shaping element for a high-power fiber laser.

A dual aspheric integrated beam shaper suitable for a high-power laser situation has been designed and realized. The model for this lens was derived theoretically and the performance was evaluated using a detailed simulation. The ultrasonic vibration assisted cutting and the high-precision grinding and polishing technology were used for the processing. The surface accuracy was less than 200 nm measured with a profiler, and the roughness was smaller than 20 nm with the help of the white light interferometer. Shaping experiments were carried out, which verified that the Gaussian beam has uniform intensity distribution with a uniformity of 85.13% in the near field and converges to a point in the far field, which is exactly as expected. It thus provides an actual selection for high-power laser shaping.

Engineering a conformal optical window of a square-to-circular transition isolator.

To realize the flow visualization of shock train structures by Schlieren measurements in a square-to-circular transition isolator, a high-precision conformal optical window was manufactured by fly-cutting technology. According to the light refraction principle, the window's outer surface was iteratively optimized based on the super-elliptic curves of the internal flow channel. Through tolerance analysis and processing parameter optimization, the transmitted wavefront error (RMS value) of the finished window was 0.823λ (λ=632.8n m). Based on a z-type Schlieren apparatus, the high-precision Schlieren measurements were conducted through the window and processed by an image filtering process method. The results promote high-precision Schlieren observation towards square-to-circular transition isolators.

Identification of the Highly Active Co-N4 Coordination Motif for Selective Oxygen Reduction to Hydrogen Peroxide.

Electrosynthesis of hydrogen peroxide (H2O2) through oxygen reduction reaction (ORR) is an environment-friendly and sustainable route for obtaining a fundamental product in the chemical industry. Co-N4 single-atom catalysts (SAC) have sparkled attention for being highly active in both 2e- ORR, leading to H2O2 and 4e- ORR, in which H2O is the main product. However, there is still a lack of fundamental insights into the structure-function relationship between CoN4 and the ORR mechanism over this family of catalysts. Here, by combining theoretical simulation and experiments, we unveil that pyrrole-type CoN4 (Co-N SACDp) is mainly responsible for the 2e- ORR, while pyridine-type CoN4 catalyzes the 4e- ORR. Indeed, Co-N SACDp exhibits a remarkable H2O2 selectivity of 94% and a superb H2O2 yield of 2032 mg for 90 h in a flow cell, outperforming most reported catalysts in acid media. Theoretical analysis and experimental investigations confirm that Co-N SACDp─with weakening O2/HOO* interaction─boosts the H2O2 production.

Self-calibration interferometric stitching test method for cylindrical surfaces.

The surface figure accuracy requirement of cylindrical surfaces widely used in rotors of gyroscope, spindles of ultra-precision machine tools and high-energy laser systems is nearly 0.1 µm. Cylindricity measuring instrument that obtains 1-D profile result cannot be utilized for deterministic figuring methods. Interferometric stitching test for cylindrical surfaces utilizes a CGH of which the system error will accumulated to unacceptable extent for large aperture/angular aperture that require many subapertures. To this end, a self-calibration interferometric stitching method for cylindrical surfaces is proposed. The mathematical model of cylindrical surface figure and the completeness condition of self-calibration stitching test of cylindrical surfaces were analyzed theoretically. The effects of shear/stitching motion error and the subapertures lattice on the self-calibration test results were analyzed. Further, a self-calibration interferometric stitching algorithm that can theoretically recover all the necessary components of the system error for testing cylindrical surfaces was proposed. Simulations and experiments on a shaft were conducted to validate the feasibility.

Quasi-absolute interferometric testing of cylinders.

A three-step quasi-absolute testing method for optical cylinders is proposed in this Letter. Three measurements are taken at the so-called cat's eye position and confocal null testing positions with a computer-generated hologram (CGH) rotated around the axis parallel to that of the cylinder. The quasi-absolute surface error of the cylinder is obtained by simple operations including addition/subtraction and flip of the datasets. The uncertainty is traceable to an optical flat. Two different CGHs are used for a convex cylinder and give consistent quasi-absolute testing results of the surface error, which experimentally validates the method.

Scanning measurement of surface error and thickness variation of the hemispherical resonator.

Hemispherical resonant gyroscopes (HRGs) are solid-state vibration gyroscopes with the highest precision and are widely used in the aerospace field. The core part of the gyroscope is the resonator, which is a thin-walled hemispherical shell. Surface error and thickness variation of a hemispherical shell causes frequency splitting, which degrades the performance of the HRG. In order to guide the mass leveling of hemispherical resonator, this paper presents a new method for scanning measurement of the surface error and thickness variation of hemispherical resonators. First, a multi-axis platform is designed for noncontact sensor scanning measurements along the meridian and latitudinal lines of the hemispherical resonator. Second, the error model of the measurement system is established. The surface error of the standard sphere is measured to calibrate and compensate for the assembly errors of the measuring device. In addition, the identification accuracy of assembly errors and the influence of assembly errors on thickness measurement are simulated by a computer. Finally, the surface error and thickness variation of the hemispherical resonators are measured. The method is experimentally demonstrated and validated with a wavefront interferometry test. The results show that the method can achieve high precision and high repeatability, which is instructive for assessment of the machining error and further evaluation of the hemispherical resonator.

Integrative design and processing of a conformal optical window pair in a cylindrical isolator.

In order to perform the flow visualization of a shock train structure by the schlieren imaging method in the cylindrical isolator, to the best of our knowledge, a novel integrative design and processing scheme of an aluminum alloy pipe with an acrylic conformal optical window pair are proposed. The optical ray tracing and wavefront correction methods were applied to design the inner cylindrical surfaces and outer aspherical cylindrical surfaces of the optical window pair for parallel light correction based on the conjoint analysis with the processing capability. Under the tolerance analysis and the optimization of the machining path, the integrative model was fabricated on a three-axis computer numerical control machine using two-axis turning and fast tool servo machining. The wavefront aberration (peak-to-valley value) and wavefront aberration (RMS) of the optical window pair were corrected within 12.189 and 2.658λ (λ=632.8nm) in the observation area which met the requirements of high-precision schlieren observation.

Discovery of an Ultra-rapid and Sensitive Lysosomal Fluorescence Lipophagy Process.

Non-invasive dynamic tracking of lysosomes and their interactions with other organelles is important for the study of lysosomal function and related diseases. However, many fluorescent dyes developed so far to target lysosomes cannot be used to monitor these processes due to the high concentrations required for imaging, long cell penetration times, and non-ideal photostability. In this regard, we synthesized three lysosomal targeting probes with large Stokes shifts, good stability, and high brightness. The Q-P-ARh dye, developed by us for the first time, can stain lysosomes at ultra-low concentrations (1.0 nM) without affecting the physiological functions of the lysosomes. More importantly, its excellent anti-interference ability and ultrafast lysosomal staining ability (within 1.0 min) clearly monitored the entire dynamic process of lipophagy. Ultimately, this method can greatly contribute to the study of autophagy pathways. This novel fluorescence platform shows great promise for the development of biological probes for application in pathological environments.

Unveiling the Proton-Feeding Effect in Sulfur-Doped Fe-N-C Single-Atom Catalyst for Enhanced CO2 Electroreduction.

Heteroatom-doping in metal-nitrogen-carbon single-atom catalysts (SACs) is considered a powerful strategy to promote the electrocatalytic CO2 reduction reaction (CO2 RR), but the origin of enhanced catalytic activity is still elusive. Here, we disclose that sulfur doping induces an obvious proton-feeding effect for CO2 RR. The model SAC catalyst with sulfur doping in the second-shell of FeN4 (Fe1 -NSC) was verified by X-ray absorption spectroscopy and aberration-corrected scanning transmission electron microscopy. Fe1 -NSC exhibits superior CO2 RR performance compared to sulfur-free FeN4 and most reported Fe-based SACs, with a maximum CO Faradaic efficiency of 98.6 % and turnover frequency of 1197 h-1 . Kinetic analysis and in situ characterizations confirm that sulfur doping accelerates H2 O activation and feeds sufficient protons for promoting CO2 conversion to *COOH, which is also corroborated by the theoretical results. This work deepens the understanding of the CO2 RR mechanism based on SAC catalysts.

Optimizing Hydrogen Binding on Ru Sites with RuCo Alloy Nanosheets for Efficient Alkaline Hydrogen Evolution.

Ruthenium (Ru)-based catalysts, with considerable performance and desirable cost, are becoming highly interesting candidates to replace platinum (Pt) in the alkaline hydrogen evolution reaction (HER). The hydrogen binding at Ru sites (Ru-H) is an important factor limiting the HER activity. Herein, density functional theory (DFT) simulations show that the essence of Ru-H binding energy is the strong interaction between the 4 d z 2 orbital of Ru and the 1s orbital of H. The charge transfer between Ru sites and substrates (Co and Ni) causes the appropriate downward shift of the 4 d z 2 -band center of Ru, which results in a Gibbs free energy of 0.022 eV for H* in the RuCo system, much lower than the 0.133 eV in the pure Ru system. This theoretical prediction has been experimentally confirmed using RuCo alloy-nanosheets (RuCo ANSs). They were prepared via a fast co-precipitation method followed with a mild electrochemical reduction. Structure characterizations reveal that the Ru atoms are embedded into the Co substrate as isolated active sites with a planar symmetric and Z-direction asymmetric coordination structure, obtaining an optimal 4 d z 2 modulated electronic structure. Hydrogen sensor and temperature program desorption (TPD) tests demonstrate the enhanced Ru-H interactions in RuCo ANSs compared to those in pure Ru nanoparticles. As a result, the RuCo ANSs reach an ultra-low overpotential of 10 mV at 10 mA cm-2 and a Tafel slope of 20.6 mV dec-1 in 1 M KOH, outperforming that of the commercial Pt/C. This holistic work provides a new insight to promote alkaline HER by optimizing the metal-H binding energy of active sites.

Interferometric stitching method for testing cylindrical surfaces with large apertures.

Cylindrical surfaces widely used in high-energy laser systems can have nearly semi-meter-scale dimensions, and aperture angles can exceed R/3. State-of-the-art interferometric stitching test methods involve stitching only along the arc direction, and the reported dimensions of ∼50 × 50 mm2 are far smaller than those required in high-energy laser systems. To rectify this limitation, an interferometric stitching method for cylindrical surfaces with large apertures is proposed. Moreover, a subaperture stitching algorithm that can stitch along both the linear and arc directions is developed. An interferometric stitching workstation equipped with a six-axis motion stage and a series of computer-generated holograms is established, where cylindrical surfaces with R/# values as large as R/0.5 and apertures up to 700 mm can be tested based on the theoretical analysis. A convex cylindrical surface with a 350 × 380 mm2 aperture is tested to validate the proposed method's feasibility in enlarging the testable aperture of cylindrical surfaces significantly from Ф50 mm to Ф700 mm, thereby promoting the application of large cylindrical surfaces in high-energy laser systems.

Atomically Dispersed s-Block Magnesium Sites for Electroreduction of CO2 to CO.

Atomically dispersed transition metal sites have been extensively studied for CO2 electroreduction reaction (CO2 RR) to CO due to their robust CO2 activation ability. However, the strong hybridization between directionally localized d orbits and CO vastly limits CO desorption and thus the activities of atomically dispersed transition metal sites. In contrast, s-block metal sites possess nondirectionally delocalized 3s orbits and hence weak CO adsorption ability, providing a promising way to solve the suffered CO desorption issue. Herein, we constructed atomically dispersed magnesium atoms embedded in graphitic carbon nitride (Mg-C3 N4 ) through a facile heat treatment for CO2 RR. Theoretical calculations show that the CO desorption on Mg sites is easier than that on Fe and Co sites. This theoretical prediction is demonstrated by experimental CO temperature program desorption and in situ attenuated total reflection infrared spectroscopy. As a result, Mg-C3 N4 exhibits a high turnover frequency of ≈18 000 per hour in H-cell and a large current density of -300 mA cm-2 in flow cell, under a high CO Faradaic efficiency ≥90 % in KHCO3 electrolyte. This work sheds a new light on s-block metal sites for efficient CO2 RR to CO.

Chemical Identification of Catalytically Active Sites on Oxygen-doped Carbon Nanosheet to Decipher the High Activity for Electro-synthesis Hydrogen Peroxide.

Electrochemical production of hydrogen peroxide (H2 O2 ) through two-electron (2 e- ) oxygen reduction reaction (ORR) is an on-site and clean route. Oxygen-doped carbon materials with high ORR activity and H2 O2 selectivity have been considered as the promising catalysts, however, there is still a lack of direct experimental evidence to identify true active sites at the complex carbon surface. Herein, we propose a chemical titration strategy to decipher the oxygen-doped carbon nanosheet (OCNS900 ) catalyst for 2 e- ORR. The OCNS900 exhibits outstanding 2 e- ORR performances with onset potential of 0.825 V (vs. RHE), mass activity of 14.5 A g-1 at 0.75 V (vs. RHE) and H2 O2 production rate of 770 mmol g-1 h-1 in flow cell, surpassing most reported carbon catalysts. Through selective chemical titration of C=O, C-OH, and COOH groups, we found that C=O species contributed to the most electrocatalytic activity and were the most active sites for 2 e- ORR, which were corroborated by theoretical calculations.

A flexible, room-temperature and solution-processible copper nanowire based transparent electrode protected by reduced graphene oxide exhibiting high performance and improved stability.

Advances in flexible electronic and optoelectronic devices have caused higher requirements for fabricating high-performance and low cost flexible transparent conductive electrodes (TCEs). Copper nanowires (Cu NWs) possess excellent electrical and optical properties, but the large contact resistance and poor stability limit their practical application in optoelectronic devices. In this work, we report a robust, convenient and environment-friendly method to assemble copper nanowires/reduced graphene oxide (Cu NWs/rGO) TCEs with enhanced conductivity, flexibility and stability at room temperature. The NaBH4 treatment was used to remove the organics and oxides on the surface of Cu NWs, and the graphene oxide (GO) capping layer was also effectively reduced at the same time. The best Cu NWs/rGO composite TCEs show a good optical-electrical performance with a sheet resistance of ∼50 Ω/sq and transmittance of 83% as well as superior mechanical flexibility. The oxidation resistance of Cu NWs in normal environment and even at a relatively high temperature has also been greatly improved. Additionally, the Cu NWs/rGO TCEs based heaters presented high saturation temperature and rapid response time under a low voltage. The high-performance composite Cu NWs TCEs with good stability are expected to be applied in various types of flexible optoelectronic devices.