Colorimetric Method for Sensitive Detection of Microcystin-LR Using Surface Copper Nanoparticles of Polydopamine Nanosphere as Turn-On Probe

A novel, facile sensor was further developed for microcystin-LR (MC-LR) determination by visible spectroscopy. Antibody-functionalized SiO2-coated magnetic nanoparticles (Fe3O4@SiO2) and aptamer-functionalized polydopamine nanospheres decorated with Cu nanoparticles (PDA/CuNPs) recognized specific sites in MC-LR and then the sandwich-type composites were separated magnetically. The Cu in the separated composites was converted to Cu2+ ions in solution and turn-on visible absorption was achieved after reaction with bis(cyclohexanone)oxaldihydrazone (BCO) (λmax = 600 nm). There was a quantitative relationship between the spectral intensity and MC-LR concentration. In addition, under the optimum conditions, the sensor turns out to be a linear relationship from 0.05 to 25 nM, with a limit of detection of 0.05 nM (0.05 μg/L) (S/N = 3) for MC-LR. The sensitivity was dependent on the low background absorption from the off-to-on spectrum and label amplification by the polydopamine (PDA) surface. The sensor had high selectivity, which shows the importance of dual-site recognition by the aptamer and antibody and the highly specific color formed by BCO with Cu2+. The bioassay was complete within 150 min, which enabled quick determination. The sensor was successfully used with real spiked samples. These results suggest it has potential applications in visible detection and could be used to detect other microcystin analogs.

3D-printed jars for ball-milling experiments monitoredin situby X-ray powder diffraction

Mechanochemistry is flourishing in materials science, but a characterization of the related processes is difficult to achieve. Recently, the use of plastic jars in shaker mills has enabledin situX-ray powder diffraction studies at high-energy beamlines. This paper describes an easy way to design and manufacture these jars by three-dimensional (3D) printing. A modified wall thickness and the use of a thin-walled sampling groove and a two-chamber design, where the milling and diffraction take place in two communicating volumes, allow for a reduced background/absorption and higher angular resolution, with the prospect for use at lower-energy beamlines. 3D-printed polylactic acid jars show good mechanical strength and they are also more resistant to solvents than jars made of polymethyl methacrylate. The source files for printing the jars are available as supporting information.

Hidden role of intermolecular proton transfer in the anomalously diffuse vibrational spectrum of a trapped hydronium ion

We report the vibrational spectra of the hydronium and methyl-ammonium ions captured in the C3v binding pocket of the 18-crown-6 ether ionophore. Although the NH stretching bands of the CH3NH3+ ion are consistent with harmonic expectations, the OH stretching bands of H3O+ are surprisingly broad, appearing as a diffuse background absorption with little intensity modulation over 800 cm−1 with an onset ∼400 cm−1 below the harmonic prediction. This structure persists even when only a single OH group is present in the HD2O+ isotopologue, while the OD stretching region displays a regular progression involving a soft mode at about 85 cm−1. These results are rationalized in a vibrationally adiabatic (VA) model in which the motion of the H3O+ ion in the crown pocket is strongly coupled with its OH stretches. In this picture, H3O+ resides in the center of the crown in the vibrational zero-point level, while the minima in the VA potentials associated with the excited OH vibrational states are shifted away from the symmetrical configuration displayed by the ground state. Infrared excitation between these strongly H/D isotope-dependent VA potentials then accounts for most of the broadening in the OH stretching manifold. Specifically, low-frequency motions involving concerted motions of the crown scaffold and the H3O+ ion are driven by a Franck–Condon-like mechanism. In essence, vibrational spectroscopy of these systems can be viewed from the perspective of photochemical interconversion between transient, isomeric forms of the complexes corresponding to the initial stage of intermolecular proton transfer.

Investigation of Micro-Raman Spectroscopy to Determine the Degree of Cure for Tiny Dot Epoxy Adhesive

Epoxy adhesive has been widely used in microelectronic production process and the technique to determine the degree of tiny dot adhesive cure is essential to evaluate the products. In this work, micro Raman spectra were demonstrated to examine the adhesive curing at small diameter of about hundred micrometers. There are two Raman peaks that can be observed then modification during the curing process while it is bond to observe the change in the infrared absorption due to the background absorption. These two Raman peaks located at 1260 and 790 cm-1 due to C-C breathing and C-O-C epoxide ring vibrating, respectively. It is found that the relative peak heights decrease as a function of UV exposure time. The vibration of Raman peak for heat cure were investigated for comparison the bond vibration of epoxy was also study by DFT in term of vibration rotation analysis for both close and open epoxy ring models which used to describe the vibration before and after curing processes. The open epoxide ring model shows the reducing of epoxide peak. Relative Raman peak heights are proposed to be used for determining the degree of adhesive cure. With imaging ability of micro Raman system, the mapping of curing sample can be illustrated by setting the color map with the proposed relative Raman peak height.

A robust method for removal of glint effects from satellite ocean colour imagery

Removal of the glint effects from satellite imagery for accurate retrieval of water-leaving radiances is a complicated problem since its contribution in the measured signal is dependent on many factors such as viewing geometry, sun elevation and azimuth, illumination conditions, wind speed and direction, and the water refractive index. To simplify the situation, existing glint correction models describe the extent of the glint-contaminated region and its contribution to the radiance essentially as a function of the wind speed and sea surface slope that often lead to a tremendous loss of information with a considerable scientific and financial impact. Even with the glint-tilting capability of modern sensors, glint contamination is severe on the satellite-derived ocean colour products in the equatorial and sub-tropical regions. To rescue a significant portion of data presently discarded as "glint contaminated" and improving the accuracy of water-leaving radiances in the glint contaminated regions, we developed a glint correction algorithm which is dependent only on the satellite derived Rayleigh Corrected Radiance and absorption by clear waters. The new algorithm is capable of achieving meaningful retrievals of ocean radiances from the glint-contaminated pixels unless saturated by strong glint in any of the wavebands. It takes into consideration the combination of the background absorption of radiance by water and the spectral glint function, to accurately minimize the glint contamination effects and produce robust ocean colour products. The new algorithm is implemented along with an aerosol correction method and its performance is demonstrated for many MODIS-Aqua images over the Arabian Sea, one of the regions that are heavily affected by sunglint due to their geographical location. The results with and without sunglint correction are compared indicating major improvements in the derived products with sunglint correction. When compared to the results of an existing model in the SeaDAS processing system, the new algorithm has the best performance in terms of yielding physically realistic water-leaving radiance spectra and improving the accuracy of the ocean colour products. Validation of MODIS-Aqua derived water-leaving radiances with in-situ data also corroborates the above results. Unlike the standard models, the new algorithm performs well in variable illumination and wind conditions and does not require any auxiliary data besides the Rayleigh-corrected radiance itself. Exploitation of signals observed by sensors looking within regions affected by bright white sunglint is possible with the present algorithm when the requirement of a stable response over a wide dynamical range for these sensors is fulfilled.