Mechanism of Gold-Silver Alloy Nanoparticle Formation by Laser Coreduction of Gold and Silver Ions in Solution.

Photochemical reduction of aqueous Ag and [AuCl] into alloy Au-Ag nanoparticles (Au-Ag NPs) with intense laser pulses is a green synthesis approach that requires no toxic chemical reducing agents or stabilizers; however size control without capping agents still remains a challenge. Hydrated electrons produced in the laser plasma can reduce both [AuCl] and Ag to form NPs, but hydroxyl radicals (OH·) in the plasma inhibit Ag NP formation by promoting the back-oxidation of Ag into Ag. In this work, femtosecond laser reduction is used to synthesize Au-Ag NPs with controlled compositions by adding the OH· scavenger isopropyl alcohol (IPA) to precursor solutions containing KAuCl and AgClO.

Nucleation and growth of gold nanoparticles initiated by nanosecond and femtosecond laser irradiation of aqueous [AuCl].

Irradiation of aqueous [AuCl4]- with 532 nm nanosecond (ns) laser pulses produces monodisperse (PDI = 0.04) 5 nm Au nanoparticles (AuNPs) without any additives or capping agents via a plasmon-enhanced photothermal autocatalytic mechanism. Compared with 800 nm femtosecond (fs) laser pulses, the AuNP growth kinetics under ns laser irradiation follow the same autocatalytic rate law, but with a significantly lower sensitivity to laser pulse energy.

Radical Chemistry in a Femtosecond Laser Plasma: Photochemical Reduction of Ag⁺ in Liquid Ammonia Solution.

Plasmas with dense concentrations of reactive species such as hydrated electrons and hydroxyl radicals are generated from focusing intense femtosecond laser pulses into aqueous media. These radical species can reduce metal ions such as Au to form metal nanoparticles (NPs). However, the formation of H₂O₂ by the recombination of hydroxyl radicals inhibits the reduction of Ag⁺ through back-oxidation.

Roles of Free Electrons and HO in the Optical Breakdown-Induced Photochemical Reduction of Aqueous [AuCl].

Free electrons and HO formed in an optical breakdown plasma are found to directly control the kinetics of [AuCl] reduction to form Au nanoparticles (AuNPs) during femtosecond laser-assisted synthesis of AuNPs. The formation rates of both free electrons and HO strongly depend on the energy and duration of the 800 nm laser pulses over the ranges of 10-2400 μJ and 30-1500 fs. By monitoring the conversion of [AuCl] to AuNPs using in situ UV-vis spectroscopy during laser irradiation, the first- and second-order rate constants in the autocatalytic rate law, k and k, were extracted and compared to the computed free electron densities and experimentally measured HO formation rates.

Effect of background correction on peak detection and quantification in online comprehensive two-dimensional liquid chromatography using diode array detection.

A singular value decomposition-based background correction (SVD-BC) technique is proposed for the reduction of background contributions in online comprehensive two-dimensional liquid chromatography (LC×LC) data. The SVD-BC technique was compared to simply subtracting a blank chromatogram from a sample chromatogram and to a previously reported background correction technique for one dimensional chromatography, which uses an asymmetric weighted least squares (AWLS) approach. AWLS was the only background correction technique to completely remove the background artifacts from the samples as evaluated by visual inspection.

Lewis pair polymerization by classical and frustrated Lewis pairs: acid, base and monomer scope and polymerization mechanism.

Classical and frustrated Lewis pairs (LPs) of the strong Lewis acid (LA) Al(C(6)F(5))(3) with several Lewis base (LB) classes have been found to exhibit exceptional activity in the Lewis pair polymerization (LPP) of conjugated polar alkenes such as methyl methacrylate (MMA) as well as renewable α-methylene-γ-butyrolactone (MBL) and γ-methyl-α-methylene-γ-butyrolactone (γ-MMBL), leading to high molecular weight polymers, often with narrow molecular weight distributions. This study has investigated a large number of LPs, consisting of 11 LAs as well as 10 achiral and 4 chiral LBs, for LPP of 12 monomers of several different types. Although some more common LAs can also be utilized for LPP, Al(C(6)F(5))(3)-based LPs are far more active and effective than other LA-based LPs.