Desorption electrospray ionization (DESI) mass spectrometry (MS) was used to differentiate seven bacteria species on the basis of their measured DESI-mass spectral profile. Both gram-positive and gram-negative bacteria were tested and included Escherichia coli, Staphyloccocus aureus, Enterococcus sp., Bordetella bronchiseptica, Bacillus thuringiensis, Bacillus subtilis and Salmonella typhimurium. Distinct DESI-mass spectra, in the mass range of 50-500 u, were obtained from whole bacteria in either positive or negative ion modes in less than 2 mins analysis time. Positive ion DESI-mass spectral fingerprints were compared using principal components analysis (PCA) to investigate reproducibility for the intraday and the day-to-day measurements and the method selectivity to differentiate the bacteria studied. Detailed study of variances in the assay revealed that a large contribution to the DESI-mass spectral fingerprint variation was the growth media preparation procedure. Specifically, experiments conducted with the growth media prepared using the same batch yielded highly reproducible DESI-mass spectra, both in intraday and in day-to-day analyses (i.e. one batch of growth media used over a 3-day period versus a new batch every day over the same 3-day period). Conclusions are drawn from our findings in terms of strategies for rapid biodetection with DESI-MS.

Controlled synthesis of low-dimensional materials, such as nanoparticles, nanorods, and hollow nanospheres, is vitally important for achieving desired properties and fabricating functional devices. We report a systematic investigation of the growth of low-dimensional sub-100 nm SnO(2) hollow nanostructures by a mild template- and surfactant-free hydrothermal route, aiming to achieve precise control of morphology and size. The starting materials are potassium stannate and urea in an ethylene glycol (EG)/H(2)O system. We found the size of the SnO(2) hollow nanospheres can be controlled by simply adjusting the urea concentration. Investigation of the mechanism of formation of the SnO(2) hollow nanospheres revealed that reaction time, urea concentration, and reaction temperature make significant contributions to the growth of hollow nanospheres. On switching the solvent from EG/H(2)O to H(2)O or ethanol, the SnO(2) nanostructures changed from nanospheres to ultrafine nanorods and nanoparticles. On the basis of reaction parameter dependent experiments, oriented self-assembly and subsequent evacuation through Ostwald ripening are proposed to explain the formation of hollow nanostructures. Their size-dependent optical properties, including UV/Vis absorption spectra and room-temperature fluorescence spectra, were also studied. Moreover, the studies on the photocatalytic property demonstrate that the fabricated hollow structures have slightly enhanced photocatalytic degradation activity for rhodamine B when exposed to mercury light irradiation compared to solid SnO(2) nanospheres under the same conditions. The synthesized tin oxide nanoparticles display high photocatalytic efficiency and have potential applications for cleaning polluted water in the textile industry.

a b s t r a c tPoly (m-phenylene isophthalamide)/graphene oxide (PMIA/GO) composite nanofiltartion (NF) membranes were prepared via a facile phase inversion method. Structures, surface properties and hydrophilicities of the membrane were analyzed using FT-IR, XPS, AFM, SEM, water contact angle and Zeta-potential measurements. FTIR spectra indicated the existence of hydrophilic carboxylic acid and hydroxyl groups in the GO molecules. SEM pictures revealed the large and finger-like micro-voids formed in the sublayer of the NF membranes after adding GO. The zeta-potential and water contact angle results proved that PMIA/GO composite membranes had more negatively charged and greater hydrophilic surfaces. The pure water flux of the PMIA/GO (0.3 wt% GO) composite membrane (125.2 (L/m 2 /h)) was 2.6 times as high as that of the pristine PMIA NF membrane (48.3 (L/m 2 /h)) at 0.8 MPa with slightly higher rejections to all tested dyes and better fouling resistance to bovine serum albumin (BSA). This study gave an effective method for preparing composite PMIA NF membranes with high water flux and excellent antifouling property, which showed potential application in water treatment.

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A simple and site-specific non-enzymatic method based on pyrolysis has been developed to cleave peptides and proteins. Pyrolytic cleavage was found to be specific and rapid as it induced a cleavage at the C-terminal side of aspartic acid in the temperature range of 220-250 °C in 10 seconds. Electrospray Ionization (ESI) mass spectrometry (MS) and tandem-MS (MS/MS) were used to characterize and identify pyrolysis cleavage products, confirming that sequence information is conserved after the pyrolysis process in both peptides and protein tested. This suggests that pyrolysis-induced cleavage at aspartyl residues can be used as a rapid protein digestion procedure for the generation of sequence specific protein biomarkers.