Multishell hollow structures have attracted tremendous attention due to their outstanding properties for application on photocatalysis. In this work, we demonstrated a straightforward and general method to construct BiOI-based coredouble shell hollow spheres for the first time. The core-double shell hollow spheres consist of Pd particles and MnO x loaded onto the inner and outer surfaces of BiOI hollow spheres, respectively (Pd/BiOI/MnO x ), and utilized them as an advanced photocatalyst for photocatalytic oxidation of formaldehyde gases and methyl blue. The hollow spheres structure could provide a large specific surface area, exposing a large number of catalytic active sites. Additionally, the Pd particles and MnOx serve the function of separating the reduction and oxidation reactive sites. The unique morphology combined with enhanced light-absorption provided the Pd/BiOI/MnO x core-double shell hollow spheres with high efficiency for the photocatalytic oxidation of formaldehyde gases and methyl blue. In situ diffuse reflectance infrared Fourier transform and electron spin resonance measurement were performed to study the mechanism of photocatalytic degradation, which revealed the important role of h + and •O 2 − during the photocatalytic reaction. These findings shed some light on the design of highly efficient photocatalysts for environmental protection.

Surface charges inside a nanopore determine the zeta potential and ion distributions and play a significant role in affecting ion transport and the sensitivity of detecting biomolecules. It is of great importance to study the fluctuation of surface charges with the salt concentration and pH in various applications of nanopores. Herein, we proposed a theoretical model to predict the surface charge density of a Si3N4 nanopore, in which both silanol and amine groups were taken into account. It was demonstrated that the surface charge density in the Si3N4 nanopore changes not only with pH but also with the salt concentration. The theoretical model could well predict the experimental results with different salt concentrations, pH values, and pore sizes. The effect of surface functional groups on the isopotential point (pHiep) of the Si3N4 nanopore was also systematically studied. The results indicated that the silanol groups are major determinants of the surface charge, but the influences of the amine groups should not be ignored because the small number of amine groups can change pHiep dramatically. The pHiep value of the Si3N4 nanopore was measured as 4.1, and the ratio of amine over silanol was ascertained as 0.013.

Discrimination of single nucleotides by a nanopore remains a challenge because of the minor difference among the four types of single nucleotides. Here, the blockade currents induced by the translocation of single nucleotides through a 1.8 nm diameter silicon nitride nanopore have been measured. It is found that the single nucleotides are driven through the nanopore by an electroosmotic flow instead of electrophoretic force when a bias voltage is applied. The blockade currents for the four types of single nucleotides are unique and differentiable, following the order of the nucleotide volume. Also, the dwell time for each single nucleotide can last for several hundred microseconds with the advantage of the electroosmotic flow, which is helpful for single nucleotide identification. The dwell-time distributions are found to obey the first-passage time distribution from the 1D Fokker-Planck equation, from which the velocity and diffusion constant of each nucleotide can be deduced. Interestingly, the larger nucleotide is found to translocate faster than the smaller one inside the nanopore because the larger nucleotide has a larger surface area, which may produce larger drag force induced by the electroosmotic flow, which is validated by molecular dynamics simulations.

Protein sequencing is essential in unveiling the mechanism of cellular processes that govern the function of living organisms, which plays a crucial role in the field of drug design and...

We report on the detection of inactivation of virus particles using femtosecond laser radiation by measuring the conductance of a solid state nanopore designed for detecting single virus particles. Conventional methods of assaying for viral inactivation based on plaque forming assays require 24-48 hours for bacterial growth. Nanopore conductance measurements provide information on morphological changes at a single virion level. We show that analysis of a time series of nanopore conductance can quantify the detection of inactivation, requiring only a few minutes from collection to analysis. Morphological changes were verified by Dynamic Light Scattering (DLS). Statistical analysis maximizing the information entropy provides a measure of the Log-reduction value. Taken together, our work provides a rapid method for assaying viral inactivation with femtosecond lasers using solid-state nanopores. I.