通过类比Rice-Ramsperger-Kassel-Marcus理论再议Marcus的电子转移速率：关于线性和非线性溶剂化情形的统一形式

R. A. Marcus在他开拓性的工作中,考察了溶剂化效应对电子转移过程的影响,并给出了著名的非绝热电子转移速率公式. 本文基于热力学溶剂化势能面的分析,从Rice-Ramsperger-Kassel-Marcus理论的角度重新考察了Marcus的公式. 由类比Rice-Ramsperger-Kassel-Marcus得到的理论,不仅可以适用于线性溶剂化的情形并得到Marcus的速率公式,也同样可以用于非线性溶剂化的情形. 在非线性溶剂化的情形下,会存在溶剂化势能面的多点交叉. 本文平行地考察了Fermi黄金规则给出的相应结果,并对比本工作中所提出的Rice-Ramsperger-Kassel-Marcus类似理论进行了批判性的讨论. 作为例释,考察了二次型溶剂化的情形. 对于这种情形,物理上存在良好的描述方案.     

基于低压补气的变转速冷藏系统的性能研究

针对冷库运行过程中出现的压缩机排气温度高、系统性能衰减等问题,设计并搭建了基于平行流换热器的低压补气冷藏系统实验台对冷藏系统在低压补气和不补气状态下压缩机转速对冷藏系统综合性能的影响进行了分析.结果 表明:随着压缩机转速的增加,两种工况下压缩机排气温度都会增加,在补气模式下排气温度增加了5％,在不补气模式下增加了7.8％;冷藏系统的制冷量也会随之增大,在补气模式下制冷量增加了43％,在不补气模式下增加了25.9％,低压补气模式下增加的制冷量更大一些;压缩机功率随转速的增加而增大,且两种模式下增幅接近,在补气模式下压缩机功率增加了27.44％,在不补气模式下增加了27.34％;另外随着转速的增大系统COP呈现先增大后减小的趋势,在转速为3500 r/min处趋于稳定.     

Au-Nanoparticle-Array/Aligned-Ag-Nanowire-Based Flexible Dual Plasmonic Substrate for Sensitive Surface-Enhanced Raman Scattering Detection

The fabrication of flexible surface-enhanced Raman scattering (SERS) substrates for sensitive detection on uneven or irregular surfaces is challenging. In this study, a flexible dual plasmonic SERS (FDPS) substrate rationally constructed using Au nanoparticle (AuNP) arrays/aligned Ag nanowires (AgNWs) and elastic polyurethane (PU) is demonstrated. It exhibits high sensitivity (detection limit of 10⁻⁸ m for melamine and 10⁻¹⁰ m for malachite green) and excellent reproducibility. The well-designed structure of AuNP arrays/aligned AgNWs fabricated using block copolymer self-assembly and oil–water–air interfacial self-assembly successfully enhances the electromagnetic field through plasmonic coupling. In addition, the FDPS substrate retains a high SERS sensitivity after exposure to air at room temperature for 30 days because of the high stability of AuNP arrays and antioxidation characteristic of the PU covered on the aligned AgNWs. Even after undergoing stretching, bending, and twisting for 100 cycles, the FDPS substrate maintains a stable SERS activity owing to the introduction of the elastic PU. This study demonstrates a potential application of SERS detection under practical conditions for irregular surfaces and may be helpful in the development of flexible sensors.     

金属和非金属原子间协同效应调控气体小分子的吸附特性研究

采用基于密度泛函理论方法系统地研究了单个NO和CO小分子在非金属(B和N)与金属Ni原子共掺杂石墨烯(Bx-Ny-gra-Ni,x+y=0,1,2,3)表面的吸附特性,分析了吸附气体小分子的几何结构,吸附能,电荷转移量以及引起体系磁性变化等情况.研究结果表明：NO和CO倾向于吸附在Ni原子的顶位,B和N掺杂原子的数量和比例能够有效地调制小分子的吸附强度;与吸附的CO分子相比,Bx-Ny-gra-Ni表面吸附的NO分子能获得较多的电荷,进而表现出高的稳定性.此外,利用吸附的气体小分子与衬底间相互作用强度和灵敏性的差异、以及引起反应衬底的磁性变化将为设计石墨烯基气敏、催化和电子器件提供重要参考.     

垂直各向异性Ho3Fe5O12薄膜的外延生长与其异质结构的自旋输运

垂直磁各向异性稀土-铁-石榴石纳米薄膜在自旋电子学中具有重要应用前景.本文使用溅射方法在(111)取向掺杂钇钪的钆镓石榴石(Gd_0.63Y_2.37Sc₂Ga₃O₁₂,GYSGG)单晶衬底上外延生长了2—100 nm厚的钬铁石榴石(Ho₃Fe₅O₁₂,HoIG)薄膜,并进一步在HoIG上沉积了3 nm Pt薄膜.测量了室温下HoIG的磁各向异性和HoIG/Pt异质结构的自旋相关输运性质.结果显示,厚度薄至2 nm的HoIG薄膜(小于2个单胞层)在室温仍具有铁磁性,且由于外延应变,2—60 nm厚HoIG薄膜都具有很强的垂直磁各向异性,有效垂直各向异性场最大达350 mT;异质结构样品表现出非常可观的反常霍尔效应和“自旋霍尔/各向异性”磁电阻效应,前者在HoIG厚度小于4 nm时开始缓慢下降,而后者当HoIG厚度小于7 nm时急剧减小,说明相较于反常霍尔效应,磁电阻效应对HoIG的体磁性相对更加敏感;此外,自旋相关热电压随HoIG厚度减薄在整个厚度范围以指数方式下降,说明遵从热激化磁振子运动规律的自旋塞贝克效应是其主要贡献者.本文结果表明HoIG纳米薄膜具有可调控的垂直磁各向异性,厚度大于4 nm的HoIG/Pt异质结构具有高效的自旋界面交换作用,是自旋电子学应用发展的一个重要候选材料.     

基于多域特征提取和深度学习的声源被动测距*

由于实际海洋环境中存在大量的非高斯噪声,一些基于高斯假设的传统去噪方法在实际海洋环境中性能下降甚至失效。针对非高斯噪声,如α稳定分布噪声、非平稳行船噪声下的脉冲信号的去噪与重构,该文提出一种基于深度学习的方法。去噪模型首先通过学习带噪信号短时傅里叶变换谱与残差谱之间的映射关系以去除环境噪声,之后对去噪信号的时频谱进行逆变换重构脉冲信号。仿真实验结果表明,深度学习模型在非高斯噪声环境下脉冲信号的去噪与重构任务中有着良好的表现,在实测样本上也表现出良好的泛化性,体现了一定的工程应用价值。     

Syntheses,Structures, and Photophysical Properties of Two Coordination Polymers Based on 2,3‐Dioxo‐1,2,3,4‐tetrahydroquinoxaline‐6‐carboxylic Acid

Two complexes based on the ligand 1,4‐dihydro‐2,3‐quinoxalinedione, namely [Mn(H₂L)₂(H₂O)₂]_n ( 1 ) and {[Zn₂(H₂L)₂(tz)₂] · 5H₂O}_n ( 2 ) (H₃L = 2,3‐dioxo‐1,2,3,4‐tetrahydroquinoxaline‐6‐carboxylic acid, Htz = 1,2,4‐triazole) were hydrothermally synthesized and characterized by elemental analyses, IR spectroscopy, as well as single‐crystal and powder X‐ray diffraction. Complex 1 exhibited a 1D comb‐like chain formed by H₂L^– anions linking Mn^II ions, whereas complex 2 was a 2D layer‐like structure with square‐shaped windows and outstretched arms built by combination of H₂L^– and tz^– ligands with Zn^II ions. The adjacent chains or layers connected with each other by intermolecular hydrogen bonding and π–π stacking to further extend to a 3D supermolecular framework. In addition, the thermal stabilities, luminescence properties, and optical energy gap of 1 and 2 were investigated in detail.     

Preparation of a Polymer Monolithic Column Using Ionic Liquid as Porogen and Its Application in Separations of Proteins and Small Molecules

A polymer-based monolithic column was prepared for high-performance liquid chromatography (HPLC), using ionic liquids as porogen within the confines of a stainless steel column (50 × 4.6 mm i.d.). In the process, 1-butyl-3-methylimidazolium chloride and dodecyl alcohol were used as bi-porogens, vinyl ester resin as the monomer, ethyleneglycol dimethacrylate as the crosslinker, CCl₄ as the initiator, and FeCl₂ as the catalytic agent to prepare the polymer-based monolithic column. Scanning electron microscopy, nitrogen adsorption–desorption instrument, and mercury intrusion porosimetry were used to assay the characteristics of the monolith, respectively. The optimized monolith showed uniform structure and good permeability. Then, the column was used as the stationary phase of HPLC to separate standard proteins and human plasma with gradient elution. Besides, the monolith was used to separate aromatic compounds from the mixture. The results showed that the addition of IL could effectively improve the structure of monoliths prepared by atom transfer radical polymerization technique. The results also suggested that this kind of monolith could be used as a simple, cheap and effective stationary phase for HPLC.     

Determination of Rosiglitazone by Direct Analysis in Real-Time Mass Spectrometry

The determination of rosiglitazone in dietary supplements by direct analysis in real-time mass spectrometry normally provides low repeatability. The [M+H]⁺ signal sharply decreased in the presence of strong-base and weak-acid ionic compounds because rosiglitazone decomposition occurred due to the hydrolysis of strong-base and weak-acid anions. The repeatability was improved and the influence of ionic compounds was minimized by the use of pioglitazone as an internal standard. Orbitrap mass spectrometry was used to provide high resolution in which isotopic interferences from M?+?1 of pioglitazone upon M of rosiglitazone were eliminated. This approach was used to determine rosiglitazone in tablet and dietary supplements in 1?min per sample.     

Enzyme-free colorimetric assay for mercury(II) using DNA conjugated to gold nanoparticles and strand displacement amplification

The authors describe a colorimetric method for the determination of Hg(II) ion. It is based on the color change from red to colorless as displayed by gold nanoparticle (AuNP) modified with thymine - rich DNA. Signal amplification is accomplished by free strand displacement recycling. In this strategy, Hg(II) unfolds the arch-trigger duplex due to the high affinity between Hg(II) and the thymines to form T-Hg(II)-T structures, thereby causing the release of trigger. The liberated trigger unfolds the hairpin structure of H1, and unfolded H1 further unfolds with H2. As a result, the H2 hairpin displaces trigger, and the released trigger unfolds another H1. This results in strong and enzyme-free strand displacement recycling amplification. The aggregation of DNA-AuNPs occurs in the presence of the duplex formed by hairpins H2 and H1. This results in a color change from red to colorless that can be visually observed. Under optimal conditions, the assay has a detection range over 4 orders of magnitude and a 3.4 nM detection limit. The assay is selective, sensitive, rapid and cost-effective. In our perception, it represents a useful platform for determination of Hg(II).

Open image in new window

Graphical abstract Schematic presentation of the  simple, rapid, low cost colorimetric detection of mercury(II) based on enzyme-free strand displacement amplification along with DNA-labeled AuNP.