Mechanical properties of the plasma-enhanced magnetron sputtering Si-C-N coatings

The mechanical properties of plasma-enhanced magnetron sputtering Si-C-N hard coatings with various compositions are characterized. The effect of chemical composition on the microstructure and properties of coating is investigated. The results show that the microstructure and mechanical properties of Si-C-N coatings are very sensitive to chemical composition. The nanocrystalline/amorphous composite structure is beneficial to the coating's mechanical properties. It also reveals that Si-C-N coating with low Si and high C concentrations has the highest hardness (≥40 GPa) and the best wear property with dry friction coefficient about 0.2.     

Dense Packing on Uniform Lattices

We study the Hard Core Model on the graphs G obtained from Archimedean tilings i.e. configurations in {0,1} ^G with the nearest neighbor 1’s forbidden. Our particular aim in choosing these graphs is to obtain insight to the geometry of the densest packings in a uniform discrete set-up. We establish density bounds, optimal configurations reaching them in all cases, and introduce a probabilistic cellular automaton that generates the legal configurations. Its rule involves a parameter which can be naturally characterized as packing pressure. It can have a critical value but from packing point of view just as interesting are the noncritical cases. These phenomena are related to the exponential size of the set of densest packings and more specifically whether these packings are maximally symmetric, simple laminated or essentially random packings. Research partially supported by The Finnish Academy of Science and Letters.     

Preparation of hard magnetic materials in thin film form

We report on the preparation, by means of pulsed laser ablation deposition, of trilayers of nominal composition Cr/SmCo₅/Cr//Si with thicknesses in the order of 250/240/125 nm, respectively. According to the results of the structural, chemical and magnetic characterizations performed in our as-deposited samples, the Sm–Co layer was structurally amorphous, exhibited abrupt compositional interfaces with the capping and buffering layers, and coercivities of a few hundreds of Oe. Magnetic hardness was developed upon submitting the samples to current anneals under vacuum at temperatures in the range of 540–670 °C. The hardening process was followed in detail by correlating the phase distribution, the nature of the interlayer atomic diffusion processes, the occurrence of textures and the temperature dependence of the coercive force. From our results we conclude about (i) the occurrence of a large degree of Co diffusion/segregation, which results in the detection, from the diffraction and magnetometric results, of the presence of CoCr alloys in the treated samples, and (ii) the close correlation, evidenced from the fits of the temperature dependence of the coercive force to the micromagnetic model, between the coercivity optimization and the crystallinity enhancement of the SmCo₅ grains.     

Annealing dependence of magnetic properties in nanostructured Sm0.5Y0.5Co5

Nanocrystalline Sm_0.5Y_0.5Co₅ powders with high coercivity H_C and enhanced remanence M_r were prepared by mechanical milling and subsequent annealing. Annealing temperatures T ranging from 973 to 1173 K, and times t ranging from 1 to 5 min were used. X-ray diffraction (XRD) and DC-magnetization measurements were carried out to study the microstructure and magnetic properties of these samples. XRD patterns demonstrate that the average grain size D of the nanocrystalline powders depends on the annealing temperature T and time t: D ranges from 11 nm (for T=973 K and t=1 min) to 93 nm (for T=1173 K and t=5 min). Magnetic measurements performed at room temperature indicate high coercivity values (H_C>955 kA/m), and enhanced remanence (M_r/M_max>0.5) for all samples. A strong annealing-induced grain size dependence of these magnetic properties was found.     

Magnetic properties of YCo5 (70%wt)+Y2Co17 (30%wt) nanocomposite powders at low temperatures

Nanostructured YCo₅ (70%wt)+Y₂Co₁₇ (30%wt) composite powders were prepared by mechanical milling and subsequent annealing at 1073 K for 1.5 min. The average grain size D of the YCo₅ and Y₂Co₁₇ phases, obtained from XRD data, was 14 and 12 nm, respectively. The temperature dependence of the magnetic properties was studied by DC magnetization measurements at temperatures T ranging from 3 to 300 K. Hysteresis loops (H_max=70 kOe) show that both the coercivity H_C and the squareness σ_r/σ_max are temperature-dependent. The coercivity increases from 12 kOe at room temperature to 18 kOe at T=3 K. The observed enhanced remanence (σ_r/σ_max>0.5) indicates that a strong exchange coupling is present at all temperatures used in this study. The maximum magnetization σ_max changes little with temperature and has a value of about 70% of the effective saturation magnetization of the title compound.     

A fluorescence enhanced probe for sulfur dioxide detection and fluorescence imaging in living cellsEI北大核心CSCD

基于香豆素和苯并吡啶基团,构建了用于二氧化硫(SO_(2))高效检测的荧光探针P1,其化学结构通过核磁氢谱(^(1)H NMR)、碳谱(^(13)C NMR)和高分辨质谱(HR-MS)确证。在缓冲溶液体系中,单独的探针P1具有微弱的荧光,识别SO_(2)后荧光发射强度明显增强,能够实现对SO_(2)的专一性裸眼识别,检出限为126 nmol/L。生物应用实验结果表明,该探针具有较低的细胞毒性,可用于生物活细胞中外源性SO_(2)的荧光成像。     

Achieving Molecular Recognition of Structural Analogues in Surface-Enhanced Raman Spectroscopy: Inducing Charge and Geometry Complementarity to Mimic Molecular Docking

Molecular recognition of complex isomeric biomolecules remains challenging in surface-enhanced Raman scattering (SERS) spectroscopy due to their small Raman cross-sections and/or poor surface affinities. To date, the use of molecular probes has achieved excellent molecular sensitivities but still suffers from poor spectral specificity. Here, we induce “charge and geometry complementarity” between probe and analyte as a key strategy to achieve high spectral specificity for effective SERS molecular recognition of structural analogues. We employ 4-mercaptopyridine (MPY) as the probe, and chondroitin sulfate (CS) disaccharides with isomeric sulfation patterns as our proof-of-concept study. Our experimental and in silico studies reveal that “charge and geometry complementarity” between MPY's binding pocket and the CS sulfation patterns drives the formation of site-specific, multidentate interactions at the respective CS isomerism sites, which “locks” each CS in its analogue-specific complex geometry, akin to molecular docking events. Leveraging the resultant spectral fingerprints, we achieve > 97 % classification accuracy for 4 CSs and 5 potential structural interferences, as well as attain multiplex CS quantification with < 3 % prediction error. These insights could enable practical SERS differentiation of biologically important isomers to meet the burgeoning demand for fast-responding applications across various fields such as biodiagnostics, food and environmental surveillance.     

Expanding the Range of Bioorthogonal Tags for Multiplex Stimulated Raman Scattering Microscopy

Multiplex optical detection in live cells is challenging due to overlapping signals and poor signal-to-noise associated with some chemical reporters. To address this, the application of spectral phasor analysis to stimulated Raman scattering (SRS) microscopy for unmixing three bioorthogonal Raman probes within cells is reported. Triplex detection of a metallacarborane using the B−H stretch at 2480–2650 cm⁻¹, together with a bis-alkyne and deuterated fatty acid can be achieved within the cell-silent region of the Raman spectrum. When coupled to imaging in the high-wavenumber region of the cellular Raman spectrum, nine discrete regions of interest can be spectrally unmixed from the hyperspectral SRS dataset, demonstrating a new capability in the toolkit of multiplexed Raman imaging of live cells.     

Tailored Zwitterionic Hemicyanine Reporters for Early Diagnosis and Prognostic Assessment of Acute Renal Failure

Drug-induced renal failure (DIRF) poses a serious medical complication with high mortality risk. However, early diagnosis or prognosis of DIRF remain challenging, as current methods rely on detecting late-stage biomarkers. Herein we present a library of zwitterionic unimolecular hemicyanines (ZCs) available for constructing activatable reporters to detect DIRF since its initial stage. Zwitterionic properties of these probes are achieved through interspersedly integrating alkyl sulfonates and quaternary ammonium cations onto hemicyanine skeleton, which result in record low plasma protein binding (<5 %) and remarkable renal clearance efficiencies (≈96 %). An activatable reporter ZCRR is further developed by masking the optimal candidate ZC6 with a tetrapeptide specifically cleavable by caspase-8, an initiating indicator of apoptosis. In living mice with cisplatin-induced DIRF, systematically administered ZCRR efficiently accumulates in kidneys and responds to elevated caspase-8 for near-infrared fluorescence signals ‘turn-on’, enabling sensitive detection of intrarenal apoptosis 60 h earlier than clinical methods, and precise evaluation of apoptosis remediation effects by different medications on DIRF mice. As it's urinary excretable, ZCRR also allows for remote detection of DIRF and predicting renoprotective efficacy through in vitro optical urinalysis. This study thus presents unimolecular renal clearable scaffolds that are applicable to developing versatile activatable reporters for renal diseases management.