A new method using MCE with LIF detection was developed for the determination of hydrogen peroxide (H2O2). Bis(p‐methylbenzenesulfonyl)dichlorofluorescein, a new fluorogenic reagent synthesized by our laboratory was employed as a labeling reagent, the derivatization reaction was performed in 0.10 M HEPES buffer (pH 7.4) for 30 min at 37°C. The detection of H2O2 was accomplished in 55 s, using a 40 mM HEPES buffer, 20% mannitol, pH 7.4, on a glass microchip. The RSDs of migration time and peak area were 1.8 and 3.7%, respectively. Method validation showed the linear response ranging from 0.50 to 50 μM with an LOD (S/N=3) of 0.20 μM (19.1 amol). The proposed method was applied to determine H2O2 in phorbol myristate acetate‐stimulated RAW264.7 macrophages, the concentration of H2O2 was found to be 1.86±0.05 μM; recoveries for macrophage samples were from 96.7 to 97.8%, within‐days and between‐days accuracies were 4.5% (n=5) and 6.8% (n=5), respectively. 相似文献
The photophysical processes for three nanosized photocatalytic oxides, titanium dioxide (TiO2) thin film, tin dioxide (SnO2) thin film, and layered TiO2/SnO2 thin film, have been examined in planar solid-state devices. It is found that, for SnO2 thin film, the dissociation of the photogenerated excitons can take place both on the film surface and inside the film, while for TiO2 thin film, almost all excitons dissociate on the film surface. Such a difference is proposed to account for the higher photocatalytic activity of TiO2 over SnO2, since it is experimentally shown that the excitons dissociate in SnO2 thin film as efficiently as they do in TiO2 thin film. For layered TiO2/SnO2 thin film, when it is illuminated by a beam of UV light, it is suggested that there exists a local electrostatic field at the SnO2 side of the interface, mainly formed by those holes efficiently photogenerated and then localized in SnO2 thin film. The photo-induced local electrostatic field is believed to facilitate hole–electron separation on TiO2 thin film and therefore increase the photocatalytic activity of the layered thin film over single TiO2 thin film. 相似文献
Functional spheres : Monodisperse gold‐doped titania spheres with tunable sizes under high concentration of titanium precursor have been synthesized by introducing trace amounts of chloroauric acid into the reaction system. Surface photovoltage, surface photocurrent, and transient photovoltage measurements (see figure) of annealed samples reveal that gold nanodots can act as both electron acceptors and donors under the illumination of different wavelengths of light.
We herein report a theoretical analysis based on a density functional theory/time‐dependent density functional theory (DFT/TDDFT) approach to understand the different phosphorescence efficiencies of a family of cyclometalated platinum(II) complexes: [Pt(NCN)Cl] ( 1 ; NCN=1,3‐bis(2‐pyridyl)phenyl?), [Pt(CNN)Cl] ( 2 ; CNN=6‐phenyl‐2,2′‐bipyridyl?), [Pt(CNC)(CNPh)] ( 3 ; CNC=2,6‐diphenylpyridyl2?), [Pt(R‐CNN)Cl] ( 4 ; R‐CNN=3‐(6′‐(2′′‐naphthyl)‐2′‐pyridyl)isoquinolinyl?), and [Pt(R‐CNC)(CNPh)] ( 5 ; R‐CNC=2,6‐bis(2′‐naphthyl)pyridyl2?). By considering both the spin–orbit coupling (SOC) and the electronic structures of these complexes at their respective optimized singlet ground (S0) and first triplet ( ) excited states, we were able to rationalize the experimental findings that 1) 1 is a strong emitter while its isomer 2 is only weakly emissive in CH2Cl2 solution at room temperature; 2) although the cyclometalated ligand of 3 has a higher ligand‐field strength than that of 1 , 3 is nonemissive in CH2Cl2 solution at 298 K; and 3) extension of π conjugation at the lateral aryl rings of the cyclometalated ligands of 2 and 3 to give 4 and 5 , respectively, leads to increased emission quantum yields under the same conditions. We found that Jahn–Teller and pseudo‐Jahn–Teller effects are operative in complexes 2 and 3 , respectively, on going from the optimized S0 ground state to the optimized excited state, and thus lead to large excited‐state structural distortions and hence fast nonradiative decay. Furthermore, a strong‐field ligand may push the two different occupied d orbitals so far apart that the SOC effect is small and the radiative decay rate is slow. This work is an example of electronic‐structure‐driven tuning of the phosphorescence efficiency, and the DFT/TDDFT approach is demonstrated to be a versatile tool for the design of phosphorescent materials with target characteristics. 相似文献
Gold nanorods (NRs) have plasmon‐resonant absorption and scattering in the near‐infrared (NIR) region, making them attractive probes for in vitro and in vivo imaging. In the cellular environment, NRs can provide scattering contrast for darkfield microscopy, or emit a strong two‐photon luminescence due to plasmon‐enhanced two‐photon absorption. NRs have also been employed in biomedical imaging modalities such as optical coherence tomography or photoacoustic tomography. Careful control over surface chemistry enhances the capacity of NRs as biological imaging agents by enabling cell‐specific targeting, and by increasing their dispersion stability and circulation lifetimes. NRs can also efficiently convert optical energy into heat, and inflict localized damage to tumor cells. Laser‐induced heating of NRs can disrupt cell membrane integrity and homeostasis, resulting in Ca2+ influx and the depolymerization of the intracellular actin network. The combination of plasmon‐resonant optical properties, intense local photothermal effects and robust surface chemistry render gold NRs as promising theragnostic agents. 相似文献
A novel approach for differentiation and dating of red ink entries of seals on documents was developed based on ion‐pairing HPLC (IP‐HPLC) and GC/MS. Sixty‐nine red ink pastes of seals were collected and the chromatographic conditions for separation of the dye components by IP‐HPLC and the volatile additives by GC/MS in the ink entries were optimized. According to the dye components and additives, the ink entries were classified by HPLC with a multi‐wavelength UV detector. The volatile components of the inks were identified by GC/MS and the classification of the ink entries was also investigated based on these volatile additives. The results showed that most of the ink entries of the seals can be differentiated by combining HPLC with a multi‐wavelength detector and GC/MS methods. The degradation of the standard dye mixtures and the compositional changes of the ink entries of seals were investigated in light or natural aging conditions. The results indicated that the dye components decomposed in light or natural storage conditions, while the rates of the degradation depended on the structures of the dye components, the aging conditions, even the additives of the ink pastes. The results also showed that there existed good relationships between the compositional changes of the ink entries and the aging time, which can provide scientific evidences and valuable clues for dating of the ink entries. 相似文献
Porous methylsilicone monoliths doped with SiO2 powder were prepared by dispersion of SiO2 nanoparticles in methylsilicone oligomer solution followed by ammonia-catalyzed gelation and ambient drying. The microstructure of the porous composite monoliths was investigated by FTIR, SEM, and N2 adsorption. The results indicated that SiO2 evenly dispersed in methylsilicone matrix. The thermal stability of SiO2-doped methylsilicone monoliths had been enhanced. The structure stability and hydrophobic property of the composite monoliths were maintained until 400 °C. 相似文献