Nanoscale Horizons最新文献

Single-atom catalysis is a subcategory of heterogeneous catalysis with well-defined active sites. Numerous endeavors have been devoted to developing single-atom catalysts for industrially applicable catalysis, including the hydrogen evolution reaction (HER). High-current-density electrolyzers have been pursued for single-atom catalysts to increase active-site density and enhance mass transfer. Here, we reasoned that a single-atom metal embedded in nitrogen assembly carbon (NAC) catalysts with high single-atom density, large surface area, and ordered mesoporosity, could fulfil an industrially applicable HER. Among several different single-atom catalysts, the HER overpotential with the best performing Co-NAC reached a current density of 200 mA cm⁻² at 310 mV, which is relevant to industrially applicable current density. Density functional theory (DFT) calculations suggested feasible hydrogen binding on single-atom Co resulted in the promising HER activity over Co-NAC. The best-performing Co-NAC showed robust performance under alkaline conditions at a current density of 50 mA cm⁻² for 20 h in an H-cell and at a current density of 150 mA cm⁻² for 100 h in a flow cell.

In the electrochemical CO₂ reduction reaction (CO₂RR), Cu alloy electrocatalysts can control the CO₂RR selectivity by modulating the intermediate binding energy. Here, we report the thermodynamic-based Cu–Sn bimetallic phase control in heterogeneous catalysts for selective CO₂ conversion. Starting from the thermodynamic understanding about Cu–Sn bimetallic compounds, we established the specific processing window for Cu–Sn bimetallic phase control. To modulate the Cu–Sn bimetallic phases, we controlled the oxygen partial pressure (pO₂) during the calcination of electrospun Cu and Sn ions-incorporated nanofibers (NFs). This resulted in the formation of CuO–SnO₂ NFs (full oxidation), Cu–SnO₂ NFs (selective reduction), Cu₃Sn/CNFs, Cu₄₁Sn₁₁/CNFs, and Cu₆Sn₅/CNFs (full reduction). In the CO₂RR, CuO–SnO₂ NFs exhibited formate (HCOO⁻) production and Cu–SnO₂ NFs showed carbon monoxide (CO) production with the faradaic efficiency (FE) of 65.3% at −0.99 V (vs. RHE) and 59.1% at −0.89 V (vs. RHE) respectively. Cu-rich Cu₄₁Sn₁₁/CNFs and Cu₃Sn/CNFs enhanced the methane (CH₄) production with the FE of 39.1% at −1.36 V (vs. RHE) and 34.7% at −1.50 V (vs. RHE). However, Sn-rich Cu₆Sn₅/CNFs produced HCOO⁻ with the FE of 58.6% at −2.31 V (vs. RHE). This study suggests the methodology for bimetallic catalyst design and steering the CO₂RR pathway by controlling the active sites of Cu–Sn alloys.

Influenza viral infection poses a severe risk to global public health. Considering the suboptimal protection provided by current influenza vaccines against circulating influenza A viruses, it is imperative to develop novel vaccine formulations to combat respiratory infections. Here, we report the development of an intranasally-administered, self-adjuvanted double-layered protein nanoparticle consisting of influenza nucleoprotein (NP) cores coated with hemagglutinin (HA) and a truncated form of bacterial flagellin (tFliC). Intranasal vaccination of these nanoparticles notably amplified both antigen-specific humoral and cellular immune responses in the systematic compartments. Elevated antigen-specific IgA and IgG levels in mucosal washes, along with increased lung-resident memory B cell populations, were observed in the respiratory system of the immunized mice. Furthermore, intranasal vaccination of tFliC-adjuvanted nanoparticles enhanced survival rates against homologous and heterologous H3N2 viral challenges. Intriguingly, mucosal slow delivery of the prime dose (by splitting the dose into 5 applications over 8 days) significantly enhanced germinal center reactions and effector T-cell populations in lung draining lymph nodes, therefore promoting the protective efficacy against heterologous influenza viral challenges compared to single-prime immunization. These findings highlight the potential of intranasal immunization with tFliC-adjuvanted protein nanoparticles to bolster mucosal and systemic immune responses, with a slow-delivery strategy offering a promising approach for combating influenza epidemics.

Herein, a self-supported carbon network is designed through the sole pyrolysis of Carica papaya seeds (biomass) without any activation agent, demonstrating their field emission and supercapacitor applications. The pyrolysis of seeds in an argon atmosphere leads to the formation of interconnected, rod-like structures. Furthermore, the hydrofluoric acid treatment not only removed impurities, but also resulted in the formation of CaF₂ nanocrystals with the addition of F-doping. From the field emission studies, the turn-on field values defined at an emission current density of ∼10 μA cm⁻² were found to be ∼2.16 and 1.21 V μm⁻¹ for the as-prepared carbon and F-doped carbon, respectively. Notably, F-doped carbon exhibits a high emission current density of ∼9.49 mA cm⁻² and has been drawn at an applied electric field of ∼2.29 V μm⁻¹. Supercapacitor studies were carried out to demonstrate the multi-functionality of the prepared materials. The F-doped carbon electrode material exhibits the highest specific capacitance of 234 F g⁻¹ at 0.5 A g⁻¹. To demonstrate the actual supercapacitor application, the HFC//HFC symmetric coin cell supercapacitor device was assembled. The overall multifunctional applicability of the fabricated hybrid structures provides a futuristic approach to field emission and energy storage applications.

Neuroelectronic prostheses are being developed for restoring vision at the retinal level in patients who have lost their sight due to photoreceptor loss. The core component of these devices is the electrode array, which enables interfacing with retinal neurons. Generating the perception of meaningful images requires high-density microelectrode arrays (MEAs) capable of precisely activating targeted retinal neurons. Achieving this precision necessitates the downscaling of electrodes to micrometer dimensions. However, miniaturization increases electrode impedance, which poses challenges by limiting the amount of current that can be delivered, thereby impairing the electrode's capability for effective neural modulation. Additionally, it elevates noise levels, reducing the signal quality of the recorded neural activity. This report focuses on evaluating reduced graphene oxide (rGO) based devices for interfacing with the retina, showcasing their potential in vision restoration. Our findings reveal low impedance and high charge injection limit for microscale rGO electrodes, confirming their suitability for developing next-generation high-density retinal devices. We successfully demonstrated bidirectional interfacing with cell cultures and explanted retinal tissue, enabling the identification and modulation of multiple cells' activity. Additionally, calcium imaging allowed real-time monitoring of retinal cell dynamics, demonstrating a significant reduction in activated areas with small-sized electrodes. Overall, this study lays the groundwork for developing advanced rGO-based MEAs for high-acuity visual prostheses.

Recently, tellurium (Te) has been proposed as a promising p-type material; however, even the state-of-the-art results couldn’t overcome the critical roadblocks for its practical applications, such as large I–V hysteresis and high off-state leakage current. We developed a novel Te atomic layer deposition (ALD) process combined with a TeO_x seed layer and Al₂O₃ passivation to detour the limitations of p-type Te semiconducting materials. Also, we have identified the origins of high hysteresis and off current using the 77 K operation study and passivation process optimization. As a result, a p-type Te field-effect transistor exhibits less than 23 mV hysteresis and a high field-effect mobility of 33 cm² V⁻¹ s⁻¹ after proper channel thickness modulation and passivation. Also, an ultralow off-current of approximately 1 × 10⁻¹⁴ A, high on/off ratios in the order of 10⁸, and a steep slope subthreshold swing of 79 mV dec⁻¹ could be achieved at 77 K. These enhancements strongly indicate that the previously reported high off-state current was originated from interfacial defects formed at the metal–Te contact interface. Although further studies concerning this interface are still necessary, the findings herein demonstrate that the major obstacles hindering the use of Te for ultrathin p-channel device applications can be eliminated by proper process optimization.

Transition-metal nitride thin-film electrodes are potential electrode materials for all-solid-state thin-film lithium-ion batteries. In this study, orthorhombic Hf₃N₄ thin-film electrodes applied in lithium-ion batteries were fabricated by the magnetron sputtering deposition of Hf followed by N₂ plasma immersion and post-annealing for the first time. This electrode material without additives such as binders and conductive agents exhibited a high specific capacity, high cycling stability, and excellent rate performance. At a current density of 0.1 A g⁻¹, the initial discharge capacity was 583.2 mA h g⁻¹ and the stable Coulombic efficiency was 96.6%. At a high current density of 2 A g⁻¹, the Hf₃N₄ thin-film electrodes could still provide a stable discharge capacity of about 260 mA h g⁻¹ and Coulombic efficiency close to 100%. By analyzing the cyclic voltammetry curves at different scan rates, it was found that the Li⁺ storage in Hf₃N₄ thin-film electrodes was mainly contributed by a pseudo-capacitance mechanism.

Creating tin-alloyed silicon nanocrystals with tailored bandgap values is a significant challenge, primarily because a substantial concentration of tin is essential to observe useful changes in the electronic structure. However, high concentration of Sn leads to instability of the silicon–tin nanocrystals. This work introduces a completely new approach to doping and the modification of the electronic structure of nanoparticles by incorporating few-atom clusters in nanocrystals, deviating from isolated atom doping or attempting alloying. This approach is exemplified via a combined theoretical and experimental study on tin (Sn) ‘cluster-doping’ of silicon (Si) nanocrystals, motivated by the opportunities offered by the Si–Sn system with tailored band energy. First-principles modelling predicts two noteworthy outcomes: a considerably smaller bandgap of these nanocrystals even with a modest concentration of tin compared to an equivalent-sized pure silicon nanocrystal and an unexpected decrease in the bandgap of nanocrystals as the diameter of nanocrystals increases, contrary to the typical quantum confined behaviour. Experimental verification using atmospheric pressure microplasma synthesis confirms the stability of these nanocrystals under ambient conditions. The plasma-synthesised nanocrystals exhibited the predicted atypical size-dependent behaviour of the bandgap, which ranged from 1.6 eV for 1.4 nm mean diameter particles to 2.4 eV for 2.2 nm mean diameter particles.

In order to achieve a therapeutic effect, many drugs have to reach specific cellular compartments. Nanoscale drug delivery systems extend the circulation time, reduce adverse effects and thus improve tolerability compared to systemic administration. We have developed two types of albumin-coated nanocarriers equipped with built-in dyes to track their cellular uptake and intracellular enzymatic opening. Using the approved antiprotozoal drug and STAT3 inhibitor Atovaquone (Ato) as prototype for a hydrophobic small molecule, we show that Ato-loaded ovalbumin-coated nanocapsules (Ato-nCap) preferentially enter human myeloid cells. In contrast, Ato nanocrystals coated with human serum albumin (Ato-nCry) distribute their cargo in all different immune cell types, including T and B cells. By measuring the effect of Ato nanocarriers on induced STAT3 phosphorylation in IL-10-primed human dendritic cells and constitutive STAT3 phosphorylation in human melanoma cells, we demonstrate that the intracellular Ato release is particularly effective from Ato nanocrystals and less toxic than equal doses of free drug. These new nanocarriers thus represent effective systems for intracellular drug delivery.

Marine biofouling severely limits the development of the marine economy, and reactive oxygen species (ROS) produced by electrocatalytic antifouling techniques could inactivate marine microorganisms and inhibit the formation of marine biofouling. Compared with an electro-Fenton reaction, a three-electron oxygen reduction reaction (3e⁻ ORR) could generate a hydroxyl radical (˙OH) in situ without the limitation of pH and iron mud pollutants. Herein, O_v-rich γ-MnO₂ is designed to enhance the 3e⁻ ORR performance in neutral media and exhibits excellent sterilization performance for typical marine bacteria. DFT calculation reveals that O_v is beneficial to the “end-on” adsorption and activation of O₂, and the Mn site could accept the electrons from *OOH and promote its further reduction to form ˙OH; O_v and Mn sites together guarantee the high 3e⁻ ORR efficiency. In addition, liquid chromatography–tandem mass spectrometry (LC–MS/MS) proves the vast formation of ˙OH in the primary reaction stage, which is the key to sterilization. This work explores the reaction mechanism of the 3e⁻ ORR in neutral media and provides the possibility for the application of electrocatalysis technology in the treatment of marine biofouling pollution.