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Surface enhanced Raman spectroscopy (SERS) has been intensively investigated during the past decades for its enormous electromagnetic field enhancement near the nanoscale metallic surfaces. Chemical enhancement of SERS, however, remains rather elusive despite intensive research efforts, mainly due to the relatively complex enhancing factors and inconsistent experimental results. To study details of chemical enhancement mechanism, we prepared various low dimensional semiconductor substrates such as ZnO and GaN that were fabricated via metal organic chemical vapor deposition process. We used three kinds of molecules (4-MPY, 4-MBA, 4-ATP) as analytes to measure SERS spectra under non-plasmonic conditions to understand charge transfer mechanisms between a substrate and analyte molecules leading to chemical enhancement. We observed that there is a preferential route for charge transfer responsible for chemical enhancement, that is, there exists a dominant enhancement process in non-plasmonic SERS. To further confirm our idea of charge transfer mechanism, we used a combination of 2-dimensional transition metal dichalcogenide substrates and analyte molecules. We also observed significant enhancement of Raman signal from molecules adsorbed on 2-dimensional transition metal dichalcogenide surface that is completely consistent with our previous results. We also discuss crucial factors for increasing enhancement factors for chemical enhancement without involving plasmonic resonance.

Bicyclic polystyrene was prepared by combining atom transfer radical polymerization and click chemistry. The bicyclic polymer was separated from concurrently produced acyclic (branched) polymers through fractional precipitation, and its purity was quantified by two-dimensional liquid chromatography analysis. The structure of bicyclic polymer was characterized by SEC, MALDI–TOF MS, 1H NMR, and FT-IR.

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Although a number of methods have been developed to reduce sulfoxides to sulfides, many of these processes are limited by side reactions, low yields, poorly available reagents, or harsh reaction conditions. We recently studied the reaction of various sulfoxides with SOCl2 and Ph3P. We were able to obtain the corresponding sulfides in excellent yields (>90%) when aliphatic and aromatic sulfoxides were treated with SOCl2 as a catalyst and Ph3P in THF at room temperature.

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Cyclopropanone derivatives have long been considered unsustainable synthetic intermediates because of their extreme strain and kinetic instability.R eported here is the enantioselective synthesis of 1-sulfonylcyclopropanols,a ss table yet powerful equivalents of the corresponding cyclopropanone derivatives,bya-hydroxylation of sulfonylcyclopropanes using ab is(silyl) peroxide as the electrophilic oxygen source. This work constitutes the first general approach to enantioenriched cyclopropanone derivatives.B oth the electronic and steric nature of the sulfonyl moiety,w hich serves as ab aselabile protecting group and confers crystallinity to these cyclopropanone precursors,w ere found to have ac rucial impact on the rate of equilibration to the corresponding cyclopropanone.T he utility of these cyclopropanone surrogates is demonstrated in amild and stereospecific formal [3+ +1] cycloaddition with simple hydroxylamines,l eading to the efficient formation of chiral b-lactam derivatives.