Design,synthesis, and fungicidal activity of novel 1,3,4-oxadiazole derivatives

Employing the intermediate derivatization method (IDM), a series of 1,3,4-oxadiazole derivatives containing arylpyrazoloxyl moiety were designed and synthesized. In vitro bioassays showed that these compounds have moderate to significant fungicidal activity against rice sheath blight and sorghum anthracnose. Furthermore, compound 20 is a promising fungicide for further development.     

Sensing of 2,4-dichlorophenoxyacetic acid by surface-enhanced Raman scattering

Surface-enhanced Raman scattering (SERS) spectra of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was obtained by employing a bi-layer gold substrate, assembled by the reduction of Au(III) over gold-seeded nanoparticles immobilized on functionalized glass substrates. The SERS signal was linear with the logarithm of the solution concentrations between 1.0 × 10⁻⁷ mol L⁻¹ and 1.0 × 10⁻³ mol L⁻¹, indicating that the bi-layer gold substrate affords a significant dynamic range for SERS, providing an excellent analytical response within this concentration range, and revealing the high sensitivity of the gold surface towards such analyte. In addition, using the same gold substrate, a similar calibration curve was obtained for crystal-violet (CV), and it was possible to identify the concentration limit corresponding to the transition from the average SERS to the nonlinear SERS response.     

A dual-functional membrane for bisphenol A enrichment and resonance amplification by surface-enhanced Raman scattering

A dual-functional membrane with enrichment and resonance amplification property, combined with an automatic sampler was designed for bisphenol A detection by surface-enhanced Raman scattering.     

Surface-enhanced Raman scattering of 4-aminobenzenethiol on silver nanoparticles substrate

Active surface-enhanced Raman scattering (SERS) silver nanoparticles substrate was prepared by multiple depositions of Ag nanoparticles on glass slides. The substrate is based on five depositions of Ag nanoparticles on 3-aminopropyl-trimetoxisilane (APTMS) modified glass slides, using APTMS sol–gel as linker molecules between silver layers. The SERS performance of the substrate was investigated using 4-aminobenzenethiol (4-ABT) as Raman probe molecule. The spectral analyses reveal a 4-ABT Raman signal enhancement of band intensities, which allow the detection of this compound in different solutions. The average SERS intensity decreases significantly in 4-ABT diluted solutions (from 10⁻⁴ to 10⁻⁶ mol L⁻¹), but the compound may still be detected with high signal/noise ratio. The obtained results demonstrate that the Ag nanoparticles sensor has a great potential as SERS substrate.     

In-line Raman spectroscopy and advanced process control for the extraction of anethole and fenchone from fennel (Foeniculum vulgare L. MILL.)

Plants are a desirable source for molecules of all kinds and for every purpose. Besides traditional techniques for extraction, plants are challenging for modern process engineering due to great variations because of their natural origin. One way to ensure high quality and low costs, as well as highly resource-efficient extraction, is in-line monitoring and process control. This study demonstrates the use of in-line Raman spectroscopy for monitoring the extraction of anethole and fenchone from fennel seed as a typical example. A partial least square calibration model with high accuracy was created. (Anethole: R² = 0.99, root mean square error of calibration (RMSEC) = 0.01256 g/L, root mean square error of validation (RMSEV) = 0.02608 g/L, and calibration range up to 2 g/L. Fenchone: R² = 0.98, RMSEC = 0.01188 g/L, RMSEV = 0.01945 g/L, and calibration up to 0.75 g/L.) These data are directly linked to a physicochemical process model to control the extraction process in real time and to perform predictive simulations while processing. The added value of this approach for modern phytoextraction is highlighted and exemplified as a major step toward sustainable Green Extraction processes.     

Synthesis of size tunable monodispersed silver nanoparticles and the effect of size on SERS enhancement

Spherical and monodispersed silver nanoparticles (AgNPs) are ideal for fundamental research as the contribution from size and shape can be accounted for in the experimental design. In this paper a seeded growth method is presented, whereby varying the concentration of sodium borohydride-reduced silver nanoparticle seeds, different sizes of stable spherical nanoparticles with a low polydispersity nanoparticles are produced using hydroquinone as a selective reducing agent. The surface-enhanced Raman scattering (SERS) enhancement factor for each nanoparticle size produced (17, 26, 50, and 65 nm) was then assessed using three different analytes, rhodamine 6G (R6G), malachite green oxalate (MGO) and thiophenol (TP). The enhancement factor gives an indication of the Raman enhancement effect by the nanoparticle. Using non-aggregated conditions and two different laser excitation wavelength (633 nm and 785 nm) it is shown that an increase in particle size results in an increased enhancement for each analyte used.     

银/金纳米线阵列表面增强拉曼基底的制备及对孔雀石绿的高灵敏度检测

利用种子介导的软模板生长方法制备了金纳米线(Au NWs)阵列, 通过调节生长温度控制Au NWs阵列的形貌, 最后在经硼氢化钠(NaBH₄)清洗过的Au NWs阵列上化学沉积银纳米颗粒(Ag NPs), 制得银/金纳米线(Ag/Au NWs)阵列作为表面增强拉曼散射(SERS)基底. 选用罗丹明6G(R6G)作为拉曼探针分子测定了Ag/Au NWs阵列的SERS性能. 结果表明, Ag/Au NWs阵列作为SERS基底具有高灵敏度、 优异的信号均匀性和良好的稳定性. 使用Ag/Au NWs阵列对孔雀石绿(MG)检测的检出限可低至1×10^-8 mol/L, 线性范围为 1×10^-8~1×10^-4 mol/L. NaBH₄可以在不影响SERS性能的情况下去除Ag/Au NWs阵列上吸附的分子, 使得 SERS基底可以重复使用. 使用Ag/Au NWs阵列对湖水中的MG进行检测, 得到了可靠的回收率, 证明Ag/Au NWs 阵列在检测环境水体中的孔雀石绿上具有应用潜力.     

Enhanced Raman spectroscopy coupled to chemometrics for identification and quantification of acetylcholinesterase inhibitors

In this work, we present a new complete method using Surface Enhanced Raman Spectroscopy (SERS) and chemometrics for the qualitative and quantitative detection of pesticides by measuring the acetylcholinesterase (ACHE) activity. The Raman SERS is not only used for measuring the ACHE activity, but also for the direct detection of pesticides individually and for their identification. Gold nanoparticles (AuNPs) were used as dynamic SERS substrates for sensitive monitoring of ACHE activity in the presence of very low levels of organophosphate and carbamate pesticides, chemical warfare agents that are known to be ACHE inhibitors. The lowest detectable level for paraoxon was determined at 4.0 × 10⁻¹⁴ M and 1.9 × 10⁻⁹ M for carbaryl. The use of the enzyme allowed limits of detection for both pesticides that were much lower than the limits obtained by direct SERS analysis of the pesticides. The system shows a linear relationship between the intensity band at 639 cm⁻¹ and pesticide concentration. These results suggest that this biosensor could be used in the future for the non-selective detection of all ACHE inhibitors at very low concentrations with possible identification of the inhibitor.     

Density functional theory and surface-enhanced Raman spectroscopy studies on endocrine-disrupting chemical,dimethyl phthalate

A method to monitor endocrine-disrupting chemical contamination phthalate esters (PAEs) by surface-enhanced Raman scattering (SERS) spectroscopy has been investigated. The molecular structure and assignment of the vibrations of dimethyl phthalate (DMP), forming short chains in PAEs, has been studied by density functional theory (DFT) calculations. The structure of DMP with the dihedral angles of 1C-6C-11C-13O and 4C-5C-18C-20O being 133.78° and −24.00°, respectively, has the lowest energy. Theoretical vibrational frequencies using B3LYP/6-31 + G(d) (after scaling) show excellent agreement with the experimental normal Raman spectrum. In the region 200–1800 cm⁻¹, SERS spectra of DMP were measured using ordered gold nanosubstrates. All except the weak signals in the normal Raman spectrum of DMP were successfully enhanced. These results demonstrate that SERS technology could be developed as a rapid method for screening of DMP.     

A rapid method for the detection of humic acid based on the poly(thymine)-templated copper nanoparticles

A label-free fluorescent method for sensitive detection of humic acid based on poly(thymine)-templated copper nanoparticles is reported.     

Synthesis of MXene-supported layered MoS2 with enhanced electrochemical performance for Mg batteries

In this paper, the petal-like MoS₂/MXene composite has been successfully synthesized by one-step hydrothermal method. With the combination of few-layer MoS₂ nanosheets and the high conductive MXene substrate, the composite exhibits enhanced capacities and rate performance as cathode material of Mg batteries.     

Synthesis,bioactivity, action mode and 3D-QSAR of novel anthranilic diamide derivatives

Several newly synthesized anthranilic diamide derivatives were found to exhibit excellent bioactivity. The action mode test and 3D-QSAR analysis provided valuable information for evaluation and future design of anthranilic diamide insecticides.     

Synthesis,insecticidal activities and SAR studies of novel anthranilic diamides containing trifluoroethoxyl substituent and chiral amino acid moieties

Based on the structures of ryanodine receptors (RyRs) activators anthranilic diamide insecticidal agents and FKI- 1033, a series of 18 novel trifluoroethoxyl-containing chiral anthranilic diamides Ia–i and IIa–i were synthesized. Their insecticidal activities were evaluated systematically and the SAR was discussed.     

Novel dual inhibitors against FP-2 and PfDHFR as potential antimalarial agents: Design,synthesis and biological evaluation

A series of novel 2,4-diaminopyrimidine-modified compounds was designed and synthesized. Compound 14 showed micromolar dual inhibitory effect on both FP-2 and PfDHFR, and potential inhibition to the proliferation of P. falciparum 3D7 strain and chloroquine-resistant P. falciparum Dd2 strain.     

Surface-enhanced Raman scattering of 4,4′-bipyridine on silver by density functional theory calculations

Surface-enhanced Raman scattering (SERS) of 4,4′-bipyridine (BPy) on silver foil substrate was measured using the 488, 514.5, and 1064 nm excitation lines. Density functional theory (DFT) methods were used to calculate the structure and vibrational spectra of Ag–BPy, Ag₃–BPy and Ag₄–BPy complexes with B3LYP/6-31++G(d,p)(C,H,N)/Lanl2dz(Ag) basis set. The Raman bands of BPy were assigned on the basis of the calculation of potential energy distribution. The calculated spectra of Ag–BPy and Ag₄–BPy complexes were much closer to the experimental results of BPy adsorbed on silver surface than that of Ag₃–BPy complexes. The vibrational frequencies that are sensitive to the planar or non-planar structure of BPy and to the dihedral angle of two pyridyl rings were discussed. The DFT results showed that the angles between two pyridyl rings for Ag–BPy and Ag₄–BPy were skewed by about 38.44° and 37.1°, respectively. The energy gaps of the HOMO and LUMO from DFT were 415–912 nm for BPy–Ag complexes. The relative intensities of SERS bands changed with different excitation laser lines. Thus, a chemical enhancement mechanism should play an important role in the SERS of BPy on silver substrate.     

Synthesis of a reduction-sensitive Bletilla striata polysaccharide amphiphilic copolymer

A reduction-sensitive stearic acid modified-Bletilla striata polysaccharide amphiphilic copolymer is synthesized. The copolymer enabled to spontaneously form micelles which display faster docetaxel release rates under reduction condition and enhanced anticancer activity in vitro after incorporating docetaxel into micelles.     

Flexible asymmetric supercapacitor based on MnO2 honeycomb structure

By controlling the electroplating time of solution containing Mn(Ac)₂, the MnO₂ nanosheets were self-assembled to the honeycomb structure and showed an excellent electrochemical performance in 1 mol/L Na₂SO₄ electrolyte. Via pairing with activated carbon as negative electrode, the capacitor could deliver a maximum energy density of 43.84 Wh/kg and a maximum power density of 6.62 kW/kg.     

Raman spectroscopy of gold nanoparticle conjugates of cosmetic ingredient kinetin

We performed a feasibility test of the cosmetic ingredient kinetin (KT)-gold nanoparticle (AuNP) conjugates by means of vibrational Raman spectroscopy and quantum mechanical calculations. The adsorptions of KT on AuNP surfaces were examined by absorption spectra and surface-enhanced Raman scattering (SERS). The size of KT at the initial concentrations of 10⁻⁵ M with the AuNP composites was measured to be 22 nm. Density functional theory (DFT) calculations were performed to estimate the energetic stabilities of KT on an Au cluster atom. The two tautomeric forms of 9H-amino and 7H-amino in KT are predicted to have similar energies on Au. The N3-coordinating geometries in both 9H-amino and 7H-amino forms of KT are predicted to be most stable on an Au cluster. Vibrational analysis also suggested that the two tautomers of KT should coexist in the adsorbed state on Au. The concentration-dependent SERS spectra of KT indicated that 5 × 10⁻⁵ M exhibited the highest SERS signals.     

Trace molecules detectable by surface-enhanced Raman scattering based on newly developed Ag and Au nanoparticles-containing substrates

In this work, Ag and Au nanoparticles-containing substrates were first developed for obtaining a stronger surface-enhanced Raman scattering (SERS) intensity of Rhodamine 6G (R6G) and reducing the limit of detection (LOD) of trace molecules. First, the optimum electrochemically roughening conditions employed on Ag substrates for obtaining strongest SERS of R6G were investigated. Then the optimally roughened Ag substrates were incubated in the prepared Cl- and Au-containing solutions for different couples of minutes to undergo the galvanic replacement reactions. Encouragingly, the SERS of R6G adsorbed on this roughened Ag substrate modified by the replacement of Ag with Au for 5 min exhibits a higher intensity by 8-fold of magnitude, as compared with the SERS of R6G adsorbed on an unmodified roughened Ag substrate. Moreover, the practical LOD of R6G can be reduced by one order of magnitude from 1 ppq to 0.1 ppq. Further investigations indicate that the compositions of complexes formed on the substrates demonstrate decided effects on the improved SERS.     

Analysis of artist’s palette on a 16th century wood panel painting by portable and laboratory Raman instruments

Non-destructive analysis of the artist’s palette of ancient wooden panel paintings is a difficult task and studies are rare. Here we compare different methods of analysis of a wooden panel painting, dated to the early sixteenth century, mainly by Raman and infrared spectroscopies. Raman spectra were recorded on collected/sampled micrometric fragments using portable Raman instruments with laser excitation lines at 532 and 785 nm and transportable Raman instruments at 532, 633 and 785 nm; a fixed 1064 nm Raman spectrometer was also used. Infrared analyses were performed in Attenuated Total Reflection (ATR-FTIR) mode. Using the portable instrument, the Raman spectra evidenced white lead, calcite and vermilion only. Raman spectra recorded by transportable and fixed instruments enabled the identification of most of the artist’s palette: (i) white lead, calcite, gypsum and cerussite for white colour; (ii) vermilion, red lead, litharge, haematite for red; (iii) azurite, indigo and lapis lazuli for blue. IR spectra gave information on the organic binding media. XRF analysis on a brown pigment suggested an heterogeneous mixture of a red pigment (such as haematite and/or minium) and a green one as malachite. GC-MS analysis allowed identifying terpenic resin in the composition of the outer protective layer.