Mass spectrometric monitoring of ligand-bridged hot electron transfer and anaerobic oxidization on auto renewable droplet-based plasmonic nanoreactors under visible light illumination.

The light induced hot-electron on plasmonic nanostructures has been recognized as a breakthrough discovery for photovoltaic and photocatalytic applications. With mass spectrometry, we demonstrate the dynamics of hot electron transfers of anaerobic oxidization reactions on Au decorated TiO2 plasmonic nanoparticles, which were coated on the inner surface of a flask. Those nanoparticles were covered by continuously renewed liquid droplets of solvent and reactants that were transported through a Venturi jet mixer with auto-spray. In addition to intensive mass transfer in such droplet-based nanoreactors, as well as strong adsorption of reactants and rapid desorption of products on materials surfaces, the localized surface plasmon resonance (LSPR) excitation upon visible light illumination, by which accumulated energies of plasmons are transferred to electrons in the conduction band of the material, attributes to the efficient photocatalytic transformation. Mass spectrometric detection of intermediate radical anions and negative ions with stable isotope labeling unambiguously identifies that highly energetic hot electrons can escape from the plasmonic nanostructures, be collected by adsorbed molecules, and initiate bond cleavages. It was demonstrated that losses of two H atoms result in the anaerobic oxidization of each benzyl alcohol molecule to a benzyl aldehyde molecule in the absence of molecular oxygen with more than 90 % yields. The well recyclable plasmonic nanoreactors implicate the injection of transferred electrons eventually back to electronically depleted Au+ positive ions. Bridged by adsorbed molecules, electrons were repeatedly circulated back and forth in plasmonic nanoreactors, where the collected light was eventually converted into chemical energy.

Imaging the Dynamics of Metal Ion-Coupled Electron Transfer on Material Surfaces with Redox/Photo Active Chelators.

Metal ions on surfaces of various materials as bulk matrices, doped structural units, or functionalized active sites play critical roles in the establishment of physical and chemical properties. Characterization of surface-bound metal ions and metal ion-coupled electron transfer are urgently needed for the determination of material structures as well as for understanding the relationship to macroscopic properties and technological applications. We present here a mass spectrometric (MS) technique that allows the monitoring of metal ion-coupled electron transfer along with spatial distributions, identities, quantities, valences, redox activities, and associated anions. It is based on the coordination of metal ions with chelators that are redox/photo active. Upon the irradiation of a focused laser beam, metal ions on material surfaces that are covered with chelators are evaporated, ionized, and detected with MS. This technique clearly reveals ligand-metal/metal-ligand and ligand-bridged electron transfers through MS or tandem MS/MS experiments. MS images of metal ions on material surfaces with the spatial resolution down to the sub-micrometer level have been obtained. It has been applied to the monitoring of hot electron transfer, leftover positive metal ions in localized surface plasmon resonance, and photocatalytic activities of crystalline facets of TiO2.

Metal-organic framework on porous TiO2 thin film-coated alumina beads for fractional distillation of plant essential oils.

Fractionation of essential oils is technically challenging due to enormous scaffold diversities and structural complexities as well as difficulties in the implementation of the fractionation in the gas phase. Packing beads with multi-dimensional hierarchical nanostructures have been developed herein to pack fractional columns for atmospheric distillations. Activated alumina beads were coated with a porous TiO2 thin film. Growth of Cu-BTC (benzene-1,3,5-tricarboxylate) crystals in resultant porous surfaces leads to the generation of new nanopores and increased metal centers for differential coordination with diverse components of essential oils. The TiO2 thin film is not only an integral part of the composites but also induces the oriented growth of Cu-BTC metal organic framework (MOF) crystals through coordinative interactions. These Al2O3@TiO2@Cu-BTC MOF beads show very strong absorptive capability for major components of essential oils, except for a single cyclic ether eucalyptol with steric hindrances. The eucalyptol was fractionated by using the column packed with those modified alumina beads from raw materials of Artemisia argyi, and Rosmarinus officinalis with high purities up to 96% and 93%, respectively.

Cell-Based Ambient Venturi Autosampling and Matrix-Assisted Laser Desorption Ionization Mass Spectrometric Imaging of Secretory Products.

A cell-based ambient Venturi autosampling device was established for the monitoring of dynamic cell secretions in response to chemical stimulations in real time with temporal resolution on the order of a second. Detection of secretory products of cells and screening of bioactive compounds are primarily performed on an ambient autosampling probe and matrix-assisted laser desorption ionization (MALDI) mass spectrometry. It takes advantage of the Venturi effect in which the fluid flowing through an inlet capillary tube is automatically fed into a parallel array of multiple outlet capillaries. Cells are incubated inside the inlet capillary tube that is connected with either a syringe pump or liquid chromatography (LC) for the transfer of single compounds or mixtures, respectively. Secretory products were continuously pushed into the outlet capillaries and then spotted into a compressed thin film of the matrix material 9-aminoacridine for MALDI mass spectrometric imaging. In physiological pH, without the use of high voltages and without the use of chemical derivatizations, this platform can be applied to the direct assay of neurotransmitters or other secretory products released from cells in response to the stimulation of individual compounds or LC-separated eluates of natural mixtures. It provides a new way to identify bioactive compounds with a detection limit down to 0.04 fmol/pixel.

A Soft Evaporation and Ionization Technique for Mass Spectrometric Analysis and Bio-Imaging of Metal Ions in Plants Based on Metal-Iodide Cluster Ionization.

Protonation/deprotonation is the well-recognized mass spectrometric mechanism in matrix-assisted laser desorption ionization of organic molecules but not for metal ions with different oxidation states. We describe herein a soft evaporation and ionization technique for metal ions based on iodination/de-iodination in metal-iodide cluster ionization (MICI). It is not only able to determine identities and oxidation states of metal ions but also reveal spatial distributions and isotope ratios in response to physiological or environmental changes. A long chain alcohol 1-tetradecanol with no functional groups that can absorb laser irradiation was used to cover and prevent samples from direct laser ablation. Upon the irradiation of the third harmonic Nd3+:YAG (355 nm, 3 ns), iohexol containing three covalently bonded iodine atoms instantly generates negative iodide ions that can quantitatively form clusters with at least 14 essential metal ions present in plants. The detection limits vary with different metal ions down to low fmol. MICI eliminates the atomization process that obscures metal charges in inductively coupled plasma mass spectrometry. Because only metal ions can be iodinated with iohexol, interferences from the abundant organic molecules of plants that are confronted by secondary ion mass spectrometry (SIMS) are also greatly decreased.

Treatment of Pauwels type III femoral neck fracture with medial femoral neck support screw: a biomechanical and clinical study.

A femoral neck fracture is currently one of the most common types of fracture in clinical practice. The incidence continues to increase due to traffic accidents, trauma, and osteoporosis. This research includes a biomechanical study and a clinical retrospective study. In the biomechanical studies, three groups' effects (Control Group: 3CCS, DHS group, and study Group: 3CCS + mFNSS group) were compared by vertical compression tests, torsion tests, and fatigue tests. All the data were collected and analyzed. We subsequently performed a retrospective analysis of 131 patients with femoral neck fractures. The operative time, intraoperative blood loss, quality of postoperative fracture reduction, and follow-up observation of fracture healing, screw retreatment rates and fixation failure rates, as well as femoral head necrosis rates and hip function in two groups with 3CCS and 3CCS + mFNSS were compared. By the biomechanical study, we found that 3CCS + Mfnss group were biomechanically superior to 3CCS group and superior to the DHS group in terms of resistance to torsion. However, it was less effective than the DHS group in compressive strength and fatigue resistance. In terms of clinical application, 3CCS + mFNSS group was found to have lower screw retreatment rates and femoral head necrosis rates, and to have better fracture healing rates than group with 3CCS, indicating that medial support screws can effectively resist the vertical shear forces of fracture ends and promote the stability and healing of fracture ends, as well as to reduce the incidence of postoperative complications.

Electron Acceptive Mass Tag for Mass Spectrometric Imaging-Guided Synergistic Targeting to Mice Brain Glutamate Receptors.

Dysfunctional glutamate receptors (GluRs) have been implicated in neurological disorders and injuries. Hetero-tetrameric assemblies of different GluR subunits or splicing variants have distinct spatiotemporal expression patterns and pharmacological properties. Mass spectrometric imaging of GluRs-targeted small molecules is important for determining the regional preferences of these compounds. We report herein the development of a mass tag covalently bonded with glutamate or N-methyl-d-aspartate that functions as both an electron acceptor to generate mass spectrometric signals on irradiated (Bi2O3)0.07(CoO)0.03(ZnO)0.9 nanoparticles with the third harmonic (355 nm) of Nd3+:YAG laser and as the core component to target bilobed clamshell-like structures of GluRs. In this approach, different molecules produce the same tag ion. It provides a new avenue for quantitative assessment of spatial densities of different compounds, which cannot be achieved with well-established stable isotope labeling technique due to different ionization efficiency of different compounds. Various coexisting endogenous molecules are also simultaneously detected for investigation of overall physiological changes induced by these compounds. Because semiconductors do not generate background peaks, this method eliminates interferences from organic matrix materials that are used in regular MALDI (matrix assisted laser desorption ionization). The localized ionization provides high spatial resolution that can be down to sub-micrometers.