No abstract

Magnetic isolation using magnetic nanoparticles (MNPs) as trapping probes have been widely used in sample pretreatment to shorten analysis time. Nevertheless, to generate MNPs is time-consuming. Furthermore, the generated MNPs have to be further functionalized to gain the capability of recognizing their target species. Thus, an alternative approach that can impose magnetism to nonmagnetic species by simply using magnetic ions as the probes is developed in this study. That is, we employ magnetic ions (Fe, Co, and Ni) that can interact with nonmagnetic species containing oxygen-containing functional groups as the probes. Pyrophosphate (PPi), bacteria, and mammalian cells were selected as the model samples. Our results show that the as-prepared magnetic ion-PPi conjugates gain sufficient magnetism and can be readily aggregated by applying an external magnetic field. Moreover, the magnetic trapping is reversible. The PPi-containing conjugates can lose their magnetic property simply using ethylenediaminetetraacetic acid or aluminum ions as competing agents to remove or to replace, respectively, the conjugated magnetic ions. In addition, bacteria and mammalian cells that possess abundant oxygen-containing functional groups on their cell surfaces can be selectively probed by magnetic ions and gain sufficient magnetism for magnetic isolation from complex serum samples.

Due to the fast diffusion, small molecules such as hydronium ions (HO) are expected to be homogeneously distributed, even close to the site-of-origin. Given the importance of HO in numerous processes, it is surprising that HO concentration ([HO]) has yet to be profiled near its generation site with nanometer resolution. Here, we innovated a single-molecule method to probe [HO] in nanometer proximity of individual alkaline phosphatases. We designed a mechanophore with cytosine (C)-C mismatch pairs in a DNA hairpin. Binding of HO to these C-C pairs changes mechanical properties, such as stability and transition distance, of the mechanophore. These changes are recorded in optical tweezers and analyzed in a multivariate fashion to reduce the stochastic noise of individual mechanophores. With this method, we found [HO] increases in the nanometer vicinity of an active alkaline phosphatase, which supports that the proximity effect is the cause for increased rates in cascade enzymatic reactions.

We demonstrate p‐i‐n organic light‐emitting diodes (OLEDs) incorporating a p‐doped transport layer which comprises tungsten oxide (WO3) and 4,4′,4″‐tris(N‐(2‐naphthyl)‐N‐phenylamino) triphenylamine (2‐TNATA) to replace the volatile and low Tg F4‐TCNQ. We propose the 2‐TNATA:WO3 composition functions as a p‐doping layer which significantly improves hole‐injection and conductivity of the Alq3 based p‐i‐n OLEDs with long lifetime, low driving voltage (3.1 V), and high power efficiency (3.5 lm/W) at 100 cd/m2