基于能量色散X射线散射方法的液体物质探测与识别研究

固定散射角θ,采用连续波长的X射线对3类纯液体物质（伯醇、苯同系物与氯代甲烷）进行了能量色散X射线散射实验,得到了上述纯液体物质的能量色散X射线散射图谱。结果表明,每种液体物质的能量色散X射线散射图谱的峰形与峰位置彼此不同。伯醇随着碳链长度的增加,散射峰宽变窄,主峰位置向小的散射参数动量转移（q）值方向移动。苯同系物的...     

Core-shell nanostructured molecular imprinting fluorescent chemosensor for selective detection of atrazine herbicide

To convert the binding events on molecularly imprinted polymers (MIPs) into physically detectable signals and to extract the templates completely are the great challenges in developing MIP-based sensors. In this paper, a core-shell nanostructure was employed in constructing the MIP chemosensor for the improvements of template extraction efficiency and imprinted sites accessibility. Vinyl-substituted zinc(II) protoporphyrin (ZnPP) was used as both fluorescent reporter and functional monomer to synthesize atrazine-imprinted polymer shell at silica nanoparticle cores. The template atrazine coordinates with the Lewis acid binding site Zn of ZnPP to form a complex for the molecular imprinting polymerization. These imprinted sites are located in polymer matrix of the thin shells (~8 nm), possessing better accessibility and lower mass-transfer resistance for the target molecules. The fluorescence properties of ZnPP around the imprinted sites will vary upon rebinding of atrazine to these imprinted sites, realizing the conversion of rebinding events into detectable signals by monitoring fluorescence spectra. This MIP probe showed a limit of detection (LOD) of about 1.8 μM for atrazine detection. The core-shell nanostructured MIP method not only improves the sensitivity, but also shows high selectivity for atrazine detection when compared with the non-molecular imprinted counterparts.     

Surface-enhanced Raman scattering sensor for theophylline determination by molecular imprinting on silver nanoparticles

A surface-enhanced Raman scattering (SERS)-based sensor for the determination of theophylline (THO) has been developed by imprinting the target molecules on the surface of silver nanoparticles. The desired recognition sites are generated after template removal and homogeneous distribution on the silver nanoparticles that have been incorporated within polymer matrix by the in situ reduction of theophylline-silver complexes, providing molecular recognition ability and SERS active surfaces. The theophylline molecules, complementary to the shape, size, and functionality of the recognition cavities, can selectively bind to the recognition sites at the surface of silver nanoparticles driven by the formation of hydrogen bonding and surface coordination. It has been demonstrated that the SERS signals of the theophylline molecules captured on the surface of the silver nanoparticles have a good reproducibility and a dose-response relationship to the target analytes, showing the potential for reliable identification and quantification of the bioactive compound. The molecular imprinting-based SERS sensor, like antibodies or enzymes, also possesses the ability to distinguish theophylline from the closely related structure caffeine due to the variations of molecular size and shape as well as the different affinity to silver ions.     

基于虫型碳纳米纤维的气敏薄膜传感器对工作场所氨气的高灵敏性检测

本文使用铝支持的铁催化剂,通过化学气相淀积方法合成了虫型碳纳米纤维;并把它以3：2的质量比与玻璃粉混合,借助松油醇的粘结,制备了薄膜传感器。使用扫描电镜和透射电镜对虫型碳纳米纤维,铁催化剂和传感器薄膜进行了形貌分析。最后在室温和常压下,采用新的检测方法在低电压（0-1伏）条件下进行了传感器的气敏测试,分析了它对氨气的灵敏性等特性。实验结果证实：在低浓度氨气条件下(0.175 mg/m³-0.35 mg/m³),基于虫型碳纳米纤维的薄膜传感器具有极高的灵敏性;经过反复的实验,证实薄膜传感器具有很高的稳定性,极快的反应时间(0.05 s)和恢复时间(1 min)。实验结果说明虫型碳纳米纤维是极好的气敏材料。     

Full-field and point strain measurement via the inner surface of a rolling large lug tyre

Vehicle safety and performance can be dramatically improved if force or friction measurement of the tyre-terrain interface is known. Since the tyre-terrain interface is responsible for the majority of forces acting on the vehicle, this region has received a lot of attention in vehicle dynamics. Direct measurement of the tyre-terrain interface is difficult since it is hidden by the tyre and terrain. A lot of research has been conducted on the inside of tyre using accelerometers or strain gauges with research more focussed on passenger car tyres and very little work performed on agricultural tyres with larger lugs. This study performs strain measurements using point measurement, from strain gauges, and full field measurement, using a stereo camera measurement system, of the inside of an agricultural tyre on a drum test rig during vertical and lateral loading. Results show similar trends when compared to results on passenger car tyres, however the mounting of the strain gauge relative to the lug is shown to play a large role in the developed strain. Linear relationships between the applied tyre force and strain were obtained in different direction with R² values above 0.97.     

Prediction of soil vertical stress under off-road tire using smoothed-particle hydrodynamics

Evaluation of vertical stress distribution in clay-loam soil using Smoothed-Particle Hydrodynamics-Finite Element Analysis (SPH-FEA) technique is presented in this research. The moist soil is modelled using the hydrodynamic elastic–plastic material and Murnaghan equation of state, while the tire is modelled using FEA in Visual Environment’s Pam-Crash software. Soil-tire interaction is performed using the node symmetric node to segment with edge treatment method. A single-wheel tester in a soil bin environment was utilized to provide experimental data. The objectives of the experimental test were to (1) calculate maximum subsoil stresses in the subsoil at 1 to 15 passes of a wheel with loads of 1, 2, 4, and 5 kN on soil with moisture levels of 0, 10, 17, and 24%.; (2) calibrate soil with different levels of moisture (3) compare predicted soil stresses with experiments. The maximum stress at 20 cm depth increased with increasing soil moisture and also with high levels of tire load. In contrast, successive traffic showed a decreasing effect on soil stress. The coefficient of determination 0.97 shows the predictions agreed very well with experiments. The moist soil-tire interaction model will be further used to analyze the soil stress in different soil depths and different forward velocity.     

Solvent-induced hot spot switch on silver nanorod enhanced Raman spectroscopy

An extremely simple and sensitive approach using solvent-induced hot spot switch on silver nanorod enhanced Raman spectroscopy has been found and experimentally demonstrated, which can be used for detection and identification analyte molecules.     

A displacement principle for mercury detection by optical waveguide and surface enhanced Raman spectroscopy

A novel displacement principle of metal nanoparticles for target analysis, differing from the usual target-induced aggregation principle, was proved feasible by the use of para-aminothiophenol coupled Au nanoparticles (PATP-Au) multilayer as probes to detect Hg(2+). The PATP-Au multilayer was fabricated through layer-by-layer assembly of Au nanoparticles on optical waveguide (OWG) chip surface using para-aminothiophenol (PATP) as coupling molecules. The localized surface plasmon resonance (LSPR) extinction from Au nanoparticles and the PATP as a Raman reporter enable to easily capture changes in PATP-Au multilayer by OWG and of surface enhanced Raman spectroscopy, respectively. The introduction of the Hg(2+), which has a higher binding affinity to the thiol group of PATP, greatly destroyed the multilayer structure, and produced a large change, several folds higher than the noise, in LSPR features and Raman signals of PATP-Au multilayer probes, and resulted in an excellent selectivity for Hg(2+) detection at a low level of 1nM. This investigation provides us more ideas on the future development of surface analysis techniques for the detection of various target analytes.     

In situ photoreduced silver nanoparticles on cysteine: an insight into the origin of chirality

A delicate system, that is, in situ photoreduced silver metal nanoparticles (NPs) formed from a combination of Ag(+) complexes with L- or D-cysteine, enables the introduction of chirality. This chirality is essentially programmed by a synergetic interplay between the CO(2)(-) and NH(3)(+) groups on cysteine, rather than the formation of a chiral metal core (see figure).     

A simplified approach for the coupling of excitation energy transfer

A simplified approach for computing the electronic coupling of nonradiative excitation-energy transfer is proposed by following Scholes et al.’s construction on the initial and final states [G.D. Scholes, R.D. Harcourt, K.P. Ghiggino, J. Chem. Phys. 102 (1995) 9574]. The simplification is realized through defining a set of orthogonalized localized MOs, which include the polarization effect of the charge densities. The method allows calculating the coupling of both the singlet-to-singlet and triplet-to-triplet energy transfer. Numerical tests are performed for a few of dimers with different intermolecular orientations, and the results demonstrate that Coulomb term are the major contribution to the coupling of singlet-to-singlet energy transfer whereas in the case of triplet-to-triplet energy transfer, the dominant effect is arisen from the intermolecular charge-transfer states. The present application is on the Hartree-Fock level. However, the correlated wavefunctions which are normally expanded in terms of the determinant wavefunctions can be employed in the similar way.