Search

Conventional metal oxide semiconductor (MOS) gas sensors have been investigated for decades to protect our life and property. However, the traditional devices can hardly fulfill the requirements of our fast developing mobile society, because the high operating temperatures greatly limit their applications in battery-loaded portable systems that can only drive devices with low power consumption. As ammonia is gaining importance in the production and storage of hydrogen, there is an increasing demand for energy-efficient ammonia detectors. Hence, in this work, a Schottky diode resulting from the contact between zinc oxide nanorods and gold is designed to detect gaseous ammonia at room temperature with a power consumption of 625 μW. The Schottky diode gas sensors benefit from the change of barrier height in different gases as well as the catalytic effect of gold nanoparticles. This diode structure, fabricated without expensive interdigitated electrodes and displaying excellent performance at room temperature, provides a novel method to equip mobile devices with MOS gas sensors.

Integrin-transmitted cellular forces have rich spatial dynamics and are vital to many cellular functions. To advance the sensitivity and spatial resolution of cellular force imaging, we developed a force-activatable emitter reporting single-molecular tension events and the associated cellular force nanoscopy (CFN). Immobilized on a surface, the emitters are initially dark (>99.8% quenched), providing a low fluorescence background despite the high coating density (>2000/μm 2 ) required for sampling cellular force properly. The emitters fluoresce brightly once switched on by integrin tensions and can be switched off by photobleaching, enabling continuous real-time imaging of integrin molecular tensions in live cells. With multiple cycles of molecular tension imaging and localization, CFN reproduces cellular force images with 50 nm resolution. Applied to both migratory cells and stationary cells, CFN revealed ultranarrow distribution of integrin tensions at the cell leading edge, and showed that force distribution in focal adhesions (FAs) is off-centered and FA size-dependent.

Curcumin, a molecule of labile natural product, has multiplex pharmacological effects, including antioxidant, antimicrobial, and anticancer effects as well as anti-Alzheimer's disease (AD) properties. However, the drawbacks of curcumin such as poor stability and bioavailability seriously limited its application in drug development. Numerous literature studies suggested the conversion of curcumin to metal complexes and explored the clearance of β-amyloid fibrils by curcumin conjugates. However, the research about the inhibition effect of curcumin complex on τ protein aggregation is progressing slowly, and its interactive orientation with the related proteins from the steric effect has been ignored. Inspired by the perspective on interactive orientation, we conjugated curcumin molecule on the positive-charged scaffold of Ru(II) complexes (bipyridine for Ru1, phenanthroline for Ru2) to construct an octahedral structure. After being conjugated with a ruthenium octahedral framework, curcumin exhibited a stronger ability to not only inhibit aggregation of R3, the τ peptide corresponding to the third repeat unit of the microtubule binding domain (residues 306-336 in full τ) (Ru1 with an IC 50 of 0.5 μM and Ru2 with an IC 50 of less than 3 μM) but also disaggregate R3 fibers with dose-dependence through an exothermic and dynamic process. Autodock simulation was applied to get a hairpin-docking mode in the inhibition of R3 aggregation. Herein, our results provide a rational strategy emphasizing the interactive orientation from an octahedral steric structure to design the anti-AD drugs with natural compound.

Light-addressable potentiometric sensors (LAPS) are of great interest in bioimaging applications such as the monitoring of concentrations in microfluidic channels or the investigation of metabolic and signaling events in living cells. By measuring the photocurrents at electrolyte-insulator-semiconductor (EIS) and electrolyte-semiconductor structures, LAPS can produce spatiotemporal images of chemical or biological analytes, electrical potentials and impedance. However, its commercial applications are often restricted by their limited AC photocurrents and resolution of LAPS images. Herein, for the first time, the use of 1D semiconducting oxides in the form of ZnO nanorods for LAPS imaging is explored to solve this issue. A significantly increased AC photocurrent with enhanced image resolution has been achieved based on ZnO nanorods, with a photocurrent of 45.7 ± 0.1 nA at a light intensity of 0.05 mW, a lateral resolution as low as 3.0 μm as demonstrated by images of a PMMA dot on ZnO nanorods and a pH sensitivity of 53 mV/pH. The suitability of the device for bioanalysis and bioimaging was demonstrated by monitoring the degradation of a thin poly(ester amide) film with the enzyme α-chymotrypsin using LAPS. This simple and robust route to fabricate LAPS substrates with excellent performance would provide tremendous opportunities for bioimaging.

Temperature-sensitive organic nanoparticles with AIE effect were assembled in water from tetraphenylethene-based poly(N-isopropylacrylamide) (TPE-PNIPAM), which was synthesized by ATRP using TPE derivative as initiator. The size and fluorescence of TPE-PNIPAM nanoparticles can be tuned by varying the temperature. These nanoparticles can be internalized readily by HeLa cells and can be used as long-term tracer in live cells to be retained for as long as seven passages.

We report a new chemical method to determine the (15)N natural abundance (δ(15)N) for ammonium (NH4(+)) in freshwater (e.g., precipitation) and soil KCl extract. This method is based on the isotopic analysis of nitrous oxide (N2O). Ammonium is initially oxidized to nitrite (NO2(-)) by hypobromite (BrO(-)) using previously established procedures. NO2(-) is then quantitatively converted into N2O by hydroxylamine (NH2OH) under strongly acid conditions. The produced N2O is analyzed by a commercially available purge and cryogenic trap system coupled to an isotope ratio mass spectrometer (PT-IRMS). On the basis of a typical analysis size of 4 mL, the standard deviation of δ(15)N measurements is less than 0.3‰ and often better than 0.1‰ (3 to 5 replicates). Compared to previous methods, the technique here has several advantages and the potential to be used as a routine method for (15)N/(14)N analysis of NH4(+): (1) substantially simplified preparation procedures and reduced preparation time particularly compared to the methods in which diffusion or distillation is involved since all reactions occur in the same vial and separation of NH4(+) from solution is not required; (2) more suitability for low volume samples including those with low N concentration, having a blank size of 0.6 to 2 nmol; (3) elimination of the use of extremely toxic reagents (e.g., HN3) and/or the use of specialized denitrifying bacterial cultures which may be impractical for many laboratories.

Changing polystyrene nanoparticles from three-dimensional spherical shape to two-dimensional disk shape promotes their cell surface binding with significant reduction of cell uptake. As a result of lower cell uptake, nanodisks show very little perturbations on cell functions such as cellular ROS generation, apoptosis and cell cycle progression compared to nanospheres. Therefore, disk-shaped nanoparticles may be a promising template for developing cell membrane-specific and safer imaging agents for a range of biomedical applications such as molecular imaging, tissue engineering, cell tracking, and stem cell separation.

Using poly(5-{[(4'-heptoxy-4-biphenylyl)carbonyl]oxy}-1-pentyne) as an example, we demonstrate the incorporative accommodation of the rigid polyacetylene backbones and the mesogenic pendants, which leads to a highly ordered smectic (Sm) phase with a frustrated structure. The polymer exhibits a recognizable sheetlike molecular shape due to its rigid backbone and relatively short spacer (three methylene units), and the building block of the liquid crystalline (LC) phase is the whole molecule. In the LC phase, five layers of the molecules stack as a smectic A (SmA) block, and adjacent SmA blocks glide halfway of the molecular width from one to another. In scanning tunneling microscopy (STM) experiments, the STM tip scrape is found to generate a regular nanopattern with periodic electron conductivity, of which the spacing is determined by the side-chain length.