Surface-enhanced Raman spectroscopy (SERS) is a surface-sensitive technique that can enhance the intensity of Raman signal by several orders of magnitude, enabling even the detection of single molecule. This work presents the experimental and theoretical studies of an optical fiber probe with nano-structured end-facet for bio-sensing applications via SERS. The factors affecting the intensity of Raman signal passing through the fiber probe are investigated. These factors include the numerical aperture of the objective lens, the slit width of the spectrometer, the fiber length, and the size of SERS nano-array. The Raman signal loss through fiber compared with optical microscope-based free-space Raman detection is estimated. To further enhance the SERS enhancement factor, a hybrid graphene/Au nano-triangle structure is transferred on the end-facet of the fiber probe to enable SERS. Superimposing graphene layer on Au nano-structure is found to be superior over bare Au nano-structure in terms of the detection sensitivity.

A novel amphiphilic homopolymer (PAGC8), containing two hydrophilic head groups and double hydrophobic tails in each repeat unit, has been prepared by solution polymerization and named as "a geminized amphiphilic homopolymer" in this paper, which is capable of self-assembling into various nanoobjects depending on the solution concentration and solvent properties. Characterization of the self-assembly behaviors was carried out by steady-state fluorescence, transmission electron microscopy and nuclear magnetic resonance techniques. Particular emphasis was dedicated to the environmental responsiveness of the assemblies. The morphologies were observed to transform from micelle-type to vesicles on adding a certain amount of ethanol. It is noteworthy that the assemblies were able to trap hydrophilic (rhodamine B) and hydrophobic (Sudan Red) molecules. Subsequently different nanoobjects were found after the encapsulation. To probe the effect of the topological structure on the self-assembly behaviors, the properties of an additional homopolymer with single charge pendant architecture on the backbone were investigated for comparison. Significant differences in structure between the two architectures brought out remarkable variations in aggregates, which were non-responsive to the solvent environment, or encapsulation of molecules. Based on the experimental results, we proposed a possible mechanism of the morphological transitions of the assemblies.

Cu-based complex formed from Cu­(OAc)2 and [2,2′]-bipyridinyl-5,5′-dicarboxylic acid diethyl ester (BPYDCDE) ligand was synthesized for the first time. It was found that the complex could catalyze aerobic oxidation of alcohols to aldehydes or ketones very efficiently without any external base at ambient temperature and pressure, and the yield of the desired product reached >99% in 2–5 h. Combination of experimental and theoretical studies showed that the ligand enhanced the electron population on the Cu center by a ligand-to-metal charge transfer (LMCT) effect, which made OAc– in the complex have the appropriate alkalinity and be a good leaving group, and the Cu center and the OAc– catalyze the reaction cooperatively. Moreover, the amount of OAc– in the complex was much less than that of the external base added in the catalytic systems reported, suggesting that the basic anion in the complex is more efficient for promoting the reaction than the external base added.

Effective and selective transformation of diaryl ethers to value-added ketones.

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The self-aggregation of amphiphilic dendrimers G1QPAMCm based on poly(amidoamine) PAMAM possessing the same hydrophilic group but differing in alkyl chain length in aqueous solution was investigated. Differences in the chemical structures lead to significant specificities in the aggregate building process. A variety of physicochemical parameters presented monotonous regularity with the increase in alkyl chain length in multibranched structure, as traditional amphiphilic molecules. A significant difference, however, existed in the morphology and the microenvironment of the microdomain of the aggregates, with G1QPAMCm with an alkyl chain length of 16 intending to form vesicles. To obtain supporting information about the aggregation mechanism, the thermodynamic parameters of micellization, the free Gibbs energy ΔGmic, and the entropy ΔSmic were derived subsequently, of which the relationship between the hydrophobic chain length and the thermodynamic properties indicated that the self-assembly process was jointly driven by enthalpy and entropy. Other than traditional surfactants, the contribution of enthalpy has not increased identically to the increase in hydrophobic interactions, which depends on the ratio of the alkyl chain length to the radius in the headgroup. Continuous increases in the hydrophobic chain length from 12 to 16 lead to the intracohesion of the alkyl chain involved in the process of self-assembly, weakening the hydrophobic interactions, and the increase in -ΔHmic, which offers an explanation of the formation of vesicular structures.

PbS-based materials via partial oxidation showed excellent performance for electroreduction of biomass-derived levulinic acid with a high GVL faradaic efficiency of 78.6% at a current density of 13.5 mA cm−2.

We investigate the feasibility of beam position diagnostics using Higher Order Mode (HOM) signals excited by an electron beam in the third harmonic 3.9 GHz superconducting accelerating cavities at FLASH. After careful theoretical and experimental assessment of the HOM spectrum, three modal choices have been narrowed down to fulfill different diagnostics requirements. These are localized dipole beam-pipe modes, trapped cavity modes from the fifth dipole band and propagating modes from the first two dipole bands. These modes are treated with various data analysis techniques: modal identification, direct linear regression (DLR) and singular value decomposition (SVD). Promising options for beam diagnostics are found from all three modal choices. This constitutes the first prediction, subsequently confirmed by experiments, of trapped HOMs in third harmonic cavities, and also the first direct comparison of DLR and SVD in the analysis of HOM-based beam diagnostics.