Facile Preparation of Organic Nanoparticles by Interfacial Cross-Linking of Reverse Micelles and Template Synthesis of Subnanometer Au−Pt Nanoparticles

A single- and a double-tailed cationic surfactant with the triallylammonium headgroup formed reverse micelles (RMs) in heptane/chloroform containing a small amount of water. The reverse micelles were cross-linked at the interface upon UV irradiation in the presence of a water-soluble dithiol cross-linker and a photoinitiator. The resulting interfacially cross-linked reverse micelles (ICRMs) of the single-tailed surfactant aggregated in a solvent-dependent fashion, whereas those of the double-tailed were identical in size as the corresponding RMs. The ICRMs could extract anionic metal salts, such as AuCl4− and PtCl62−, from water into the organic phase. Au and Pt metal nanoparticles were produced upon reduction of metal salts. The covalent nature of the ICRMs made the template synthesis highly predictable, with the size of the metal particles controlled by the amount of the metal salt and the method of reduction. Nanoalloys were obtained by combining two metal precursors in the same reaction. Reduction of the ICRM-entrapped aurate also occurred without any external reducing agents, and the gold nanoparticles differed dramatically from those obtained through sodium borohydride reduction. The same template allowed the preparation of luminescent Au4, Au8, and Au13−Au23 clusters, as well as gold nanoparticles several nanometers in size, simply by using different amounts of gold precursor and reducing conditions

Lewis acid catalysis for (2+2)-cycloadditions and alternating copolymerizations.

(2+2) -Cycloaddition reactions between alkenes take place spontaneously when one alkene contains strong donors and the other strong acceptors. However, when the difference of electron-density between these nucleophilic and electrophilic partners is small, the (2+2) -cycloaddition does not take place. Lewis acids are known as catalysts for many purposes due to their capability to increase the accepting ability of an electrophile, and can be utilized as catalysts for these (2+2) -cycloadditions. In this study, it is shown that ethereal lithium perchlorate, which has recently been recognized as an astounding medium for many reactions, and zinc chloride can promote (2+2) -cycloadditions. This systematic study of the (2+2) -cycloadditions between various nucleophiles and electrophiles leads to an expansion of "The Organic Chemist's Periodic Table". When the electrophilic partner contains at least one ester at the olefinic end, the (2+2) -cycloaddition can occur in the presence of Lewis acid, instead of the reported inverse electron demand Diels-Alder reaction. The efficiency of Lewis acid catalysis to promote (2+2) -cycloadditions for olefin pairs where they normally do not occur is investigated. Weak Lewis acids are suitable for the (2+2) -cycloaddition in contrast to strong Lewis acids, which cause decomposition of the cyclobutanes. In addition, many cyclobutane derivatives containing an acidic proton at C₃ and a leaving group derived from sulfide at C₁ are synthesized. However, the aim of obtaining bicyclobutane by 1,3-elimination of these cyclobutane derivatives was not achieved. An exploratory study using zinc chloride as Lewis acid to promote the spontaneous alternating copolymerization between the weak acceptor olefin acrylonitrile and the donor olefins, p-methylstyrene, p-methoxystyrene and isobutyl vinyl ether was also performed

Prevalence of OXA-Type β-Lactamase Genes among Carbapenem-Resistant Acinetobacter baumannii Clinical Isolates in Thailand

Carbapenem-resistant Acinetobacter baumannii (CRAB) is a critical health concern for the treatment of infectious diseases. The aim of this study was to investigate the molecular epidemiology of CRAB emphasizing the presence of oxacillinase (OXA)-type β-lactamase-encoding genes, one of the most important carbapenem resistance mechanisms. In this study, a total of 183 non-repetitive CRAB isolates collected from 11 tertiary care hospitals across Thailand were investigated. As a result, the blaoxa-51-like gene, an intrinsic enzyme marker, was detected in all clinical isolates. The blaoxa-23-like gene was presented in the majority of isolates (68.31%). In contrast, the prevalence rates of blaoxa-40/24-like and blaoxa-58-like gene occurrences in CRAB isolates were only 4.92% and 1.09%, respectively. All isolates were resistant to carbapenems, with 100% resistance to imipenem, followed by meropenem (98.91%) and doripenem (94.54%). Most isolates showed high resistance rates to ciprofloxacin (97.81%), ceftazidime (96.72%), gentamicin (91.26%), and amikacin (80.87%). Interestingly, colistin was found to be a potential drug of choice due to the high susceptibility of the tested isolates to this antimicrobial (87.98%). Most CRAB isolates in Thailand were of ST2 lineage, but some belonged to ST25, ST98, ST129, ST164, ST215, ST338, and ST745. Further studies to monitor the spread of carbapenem-resistant OXA-type β-lactamase genes from A. baumannii in hospital settings are warranted