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Carbon dots (CDs), as a new zero-dimensional carbon-based nanomaterial with desirable optical properties, exhibit great potential for many application fields. However, the preparation technique of multiple emission CDs with high yield is difficult and complex. Therefore, exploring the large-scale and straightforward synthesis of multicolor CDs from a simple carbon source is necessary. In this work, the solvent-free method prepares a series of multicolor emission CDs from dihydroxybenzoic acid (DHBA). The maximum emission wavelengths are 408, 445, 553, 580, and 610 nm, respectively, covering the visible light region. The 2,4- and 2,6-CDs possess the longer emission wavelength caused by the 2,4-, and 2,6-DHBA easily undergo decarboxylation to form the larger sp2 domain graphitized structure. These CDs incorporated with g-C3N4 can significantly improve the photocatalytic water-splitting hydrogen production rate by extending the visible light absorption and enhancing the charge separation efficiency. The long-wavelength emission CDs can further enhance photocatalytic activity primarily by improving visible light absorption efficiency. [ABSTRACT FROM AUTHOR]

Noble metal nanoporous materials hold great potential in the field of catalysis, owing to their high open structures and numerous low coordination surface sites. However, the formation of porous nanoparticles is restricted by particle size. Herein, we utilized a Pt1Bi2 intermetallic nanocatalyst to develop a dealloying approach for preparing nanoparticles with a bi-continuous porous and core–shell structure and proposed a mechanism for the formation of pores. The particle size used to form the porous structure can be <10 nm, which enhances the nanocatalyst's performance for the oxygen reduction reaction (ORR). This study provides a new understanding of the formation of porous materials via a dealloying approach. [ABSTRACT FROM AUTHOR]

The solar H2 generation directly from natural seawater is a sustainable way of green energy. However, it is limited by a low H2 generation rate even compared to fresh water. In this report, TiO2 is chosen as a model photocatalyst to disclose the critical factor to deteriorate the H2 generation rate from seawater. The simulated seawater (SSW), which is composed of eight ions (Na+, K+, Ca2+, Mg2+, Cl−, Br−, SO42−, and CO32−), is investigated the effect of each ion on the H2 production. The results indicate that all ions have a negative effect at the same concentration as in the seawater except Br−. The CO32− has the most serious deterioration, and the H2 production rate lowers near 40% even at [CO32−] of 1.5 mmol·L−1. The H2 production rate can be recovered to 85% if the CO32− is excluded from the SSW. To understand the reason, the zeta potential of the TiO2 treated with different ions aqueous solution reveals that the zeta potential decreases when it is treated with CO32− and SO42− due to they can adsorb on the surface of TiO2 nanoparticles. Fourier transform infrared (FTIR) and thermogravimetric analysis-mass spectroscopy (TGA-MS) further confirm that the adsorbed ion is mainly from CO32−. Since the pH of seawater is about 8.9 between pKa1 (6.37) and pKa2 (10.3) of H2CO3, the CO32− should exist in the form of HCO3− in the seawater. We proposed a simple method to remove the adsorbed HCO3− from the TiO2 surface by adjusting the pH below the pKa1. The results indicate that if a trace amount of HCl (adjusting pH ∣ 6.0) is added to the SSW, the H2 production rate can be recovered to 85% of that in pure water. [ABSTRACT FROM AUTHOR]

We have recently examined the potential of bare nanocapillaries for free solution DNA separations and demonstrated efficiencies exceeding [10.sup.6] theoretical plates/ m. In the present work, we demonstrate the use of bare and hydroxypropylcellulose (HPC) coated open tubular nanocapillaries for protein separations. Using 1.5 [micro]m inner diameter (i.d.) capillary columns, hydrodynamically injecting femto- to picoliter volumes of fluorescent or fluorescent dye labeled protein samples, utilizing a pneumatically pressurized chamber containing 1.0 mM sodium tetraborate solution eluent (typically 200 psi) as the pump, and performing on-column detection using a simple laser-induced fluorescence detector, we demonstrate efficiencies of close to a million theoretical plates/m while generating single digit microliter volumes of waste for a complete chromatographic run. We achieve baseline resolution for a protein mixture consisting of transferrin, [alpha]-lactalbumin, insulin, and [alpha]-2-macroglobulin.

To perform the electrochemical nitrogen reduction reaction (NRR) under milder conditions for sustainable ammonia production, electrocatalysts should exhibit high selectivity, activity, and durability. However, the key restrictions are the highly stable N≡N triple bond and the competitive hydrogen evolution reaction (HER), which make it difficult to adsorb and activate N2 on the surface of electrocatalysts, leading to a low ammonia yield and Faraday efficiency. Inspired by the enzymatic nitrogenase process and using the Fe-Mo as the active center, here we report supported Fe2Mo3O8/XC-72 as an effective and durable electrocatalyst for the NRR. Fe2Mo3O8/XC-72 exhibited NRR activity with an NH3 yield of 30.4 µg·h−1·mg−1 (−0.3 V) and a Faraday efficiency of 8.2% (−0.3 V). Theoretical calculations demonstrated that the electrocatalytic nitrogen fixation mechanism involved the Fe atom in the Fe2Mo3O8/XC-72 electrocatalyst acting as the main active site in the enzymatic pathway (*NH2 → *NH3), which activated nitrogen molecules and promoted the NRR performance. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate DNA separation and genotyping analysis in gel-free solutions using a nanocapillary under pressure-driven conditions without application of an external electric field. The nanocapillary is a ~50-cm-long and 500-nm-radius bare fused-silica capillary. After a DNA sample is injected, the analytes are eluted out in a chromatographic separation format. The elution order of DNA molecules follows strictly with their sizes, with the longer DNA being eluted out faster than the shorter ones. High resolutions are obtained for both short (a few bases) and long (tens of thousands of base pairs) DNA fragments. Effects of key experimental parameters, such as eluent composition and elution pressure, on separation efficiency and resolution are investigated. We also apply this technique for DNA separations of real-world genotyping samples to demonstrate its feasibility in biological applications. PCR products (without any purification) amplified from Arabidopsis plant genomic DNA crude preparations are directly injected into the nanocapillary, and PCR-amplified DNA fragments are well resolved, allowing for unambiguous identification of samples from heterozygous and homozygous individuals. Since the capillaries used to conduct the separations are uncoated, column lifetime is virtually unlimited. The only material that is consumed in these assays is the eluent, and hence, the operation cost is low.

Decreasing the volume of reagent solutions consumed in each assay is an effective means to reduce the overall cost in high-throughput analysis laboratories. Recently, increasing attention has been paid to investigate the behavior of individual cells. If one wishes to transfer solution to or from a single cell, a picoliter pipettor is needed since the entire cell volume is commonly less than 1 nL. While pressure ejection and iontophoresis have been used to deliver picoliter volumes of solutions, these techniques cannot yield routine pipettors which perform both solution 'picking up' and 'dispensing' functions. The state-of-the-art pipettors can handle liquids down to ~100 nL, although the pipetting accuracy and precision deteriorate considerably from microliters to nanoliters. If one wishes to pipet reagents of less than 100 nL, new pipettors need to be developed. Electroosmosis has been utilized to pump solutions at flow rates of nanoliters to approximately picoliters per second, which is ideal for nanopipettors. The issue is how to arrange fluidic/electrical connections so that pipetting functions can be performed conveniently. In this paper, we present the results of our initial attempt to develop an electroosmosis-based nanopipettor. The first version of this pipettor consists of a microfabricated electroosmotic (EO) flow pump, a polyacrylamide grounding interface, and a nanoliter-to-picoliter pipet tip. The detailed configuration and fabrication process of the pipettor are discussed. An excellent feature of an EO-driven pipettor is that it has no moving parts. Good reproducibilities (RSD = 6% at 140 pL, 2% at 950 pL, and 2% at 13 nL) and accuracies (9% at 0.13 nL, 4% at 1.0 nL, and 3% at 10 nL) of this pipettor have been demonstrated to aliquot/transport nanoliter-to-picoliter solutions.