Real-time reaction monitoring using ion mobility-mass spectrometry

The potential of ion mobility (IM) spectrometry in combination with mass spectrometry (MS) for real-time reaction monitoring is reported. The combined IM-MS approach using electrospray ionization affords gas-phase analyte characterization based on both mass-to-charge (m/z) ratio and gas-phase ion mobility (drift time). The use of IM-MS analysis is demonstrated for the monitoring of the reaction products formed when 7-fluoro-6-hydroxy-2-methylindole is deprotonated by aqueous sodium hydroxide. Real-time reaction monitoring was carried out over a period of several hours, with the reaction mixture sampled and analysed at intervals of several minutes. Product ion relative intensity is enhanced selectively in the ion mobility-selected mass spectrum, compared to mass spectrometry alone. The combined IM-MS approach has potential as a rapid and selective technique to aid pharmaceutical process control and for the elucidation of reaction mechanism.     

Selective Detection of Hydrazine in the Presence of Excess Electrochemically Active Pharmaceutical Ingredients Using Boron Doped Diamond Metal Nanoparticle Functionalised Electrodes

Detection of the genotoxic impurity hydrazine (HZ) in the presence of active pharmaceutical ingredients (APIs) represents a significant challenge to the pharmaceutical industry. Here we show how the use of electrochemical strategies in conjunction with metal nanoparticle (NP) functionalised polycrystalline boron‐doped diamond (BDD) electrodes enables detection of HZ in the presence of two different electrochemically active APIs. By simply changing the chemical identity of the metal NP, which shifts the detection potential for HZ, it is possible to selectively screen out the API signature from the HZ current – voltage response. HZ detection limits of 11.1 µM (Au NP BDD) and 3.3 µM (Pt NP BDD) in the presence of excess acetaminophen and promazine respectively, were determined using differential pulse voltammetry in quiescent solution.     

Photocatalytic activity enhanced by plasmonic resonant energy transfer from metal to semiconductor

Plasmonic metal nanostructures have been incorporated into semiconductors to enhance the solar-light harvesting and the energy-conversion efficiency. So far the mechanism of energy transfer from the plasmonic metal to semiconductors remains unclear. Herein the underlying plasmonic energy-transfer mechanism is unambiguously determined in Au@SiO(2)@Cu(2)O sandwich nanostructures by transient-absorption and photocatalysis action spectrum measurement. The gold core converts the energy of incident photons into localized surface plasmon resonance oscillations and transfers the plasmonic energy to the Cu(2)O semiconductor shell via resonant energy transfer (RET). RET generates electron-hole pairs in the semiconductor by the dipole-dipole interaction between the plasmonic metal (donor) and semiconductor (acceptor), which greatly enhances the visible-light photocatalytic activity as compared to the semiconductor alone. RET from a plasmonic metal to a semiconductor is a viable and efficient mechanism that can be used to guide the design of photocatalysts, photovoltaics, and other optoelectronic devices.     

Broadband terahertz pulse emission from ZnGeP2

Optical rectification is demonstrated in (110)-cut ZnGeP(2) (ZGP) providing broadband terahertz (THz) generation. The source is compared to both GaP and GaAs over a wavelength range of 1150 nm to 1600 nm and peak-intensity range of 0.5 GW/cm(2) to 40 GW/cm(2). ZGP peak-to-peak field amplitude is larger than in the other materials due to either lower nonlinear absorption or larger second-order nonlinearity. This material is well suited for broadband THz generation across a wide range of infrared excitation wavelengths.