Small-sized Nanoparticles Research Articles

Hydrophilic Metal-Organic Frameworks Regulated by Biomineralized Protein for Enhanced Stability and Drug Delivery.

For bridging the gap between biological and synthetic materials, the fusion of Metal-Organic Frameworks (MOFs) with biological entities has emerged as a revolutionary strategy in functional materials. In this context, our study introduces a novel structure wherein Bovine Serum Albumin (BSA), a robust and versatile protein, encapsulates zeolitic imidazolate framework-8 (ZIF-8), forming a protein-caged MOF. Highlighting the advantages of this innovative design, the protein-encapsulation enhances the stability and dispersity of ZIF-8, and aids in the synthesis of smaller-sized nanoparticles, crucial for size-impact performance applications. Additionally, the BSA-caged ZIF-8 structure showcases potential in drug delivery applications, especially in the controlled delivery of chemotherapeutic drugs. The study thus elucidates the multifaceted applicability of this novel structure, marking a significant stride in the convergence of biological and synthetic materials.

Ru-M (Fe, Co, Ni) onto Nitrogen-doped Two-dimensional Carbon Nanosheets through Microwave Approach with Strong Metal-support Interactions for overall Water-splitting

Developing Ru-based catalysts with strong metal-support interactions (SMSI) is a significant approach to achieve highly-efficient catalytic activity and satisfactory stability. Nevertheless, the current strategies to construct SMSI are generally time-consuming and tedious, and then leading to aggregation. In this research, ultrafast microwave (45 s) is employed to affix small Ru-M (Fe, Co, Ni) nanoparticles onto nitrogen-doped two-dimensional (2D) carbon nanosheets (NCN, Ru-M/NCN), leading to robust metal-support interactions that enhance reaction kinetics and boost stability. Furthermore, the electronic interplay between Ru and M is pivotal in augmenting catalytic efficacy. The small size of the Ru-M nanoparticles and high specific surface area also favor exposing active sites and abundant interconnected channels to accelerate mass transport. Subsequent low-temperature oxidation process, to prepare RuM@RuOx/NCN, which is conducted to achieve oxygen evolution reaction (OER) performance. Thus, the as-synthesized RuCo/NCN only requires 65 mV, 58 mV, and 98 mV to achieve 10 mA cm-2 for hydrogen evolution reaction (HER) in 0.5 M H2SO4, 1 M KOH and alkaline seawater. RuM@RuOx/NCN is obtained by low-temperature oxidation to achieve excellent oxygen reduction reaction performance in 1 M KOH, the low overpotential of only 273 mV, 256 mV and 284 mV can reach 10 mA cm-2 and satisfactory stability. Moreover, the prepared electrocatalysts also achieve satisfactory electrocatalytic activity for overall water-splitting in alkaline freshwater/seawater electrolytes. This work provides a superior pathway for multifunctional nanomaterials for sustainable energy storage and conversion.

Manganese Oxide-Incorporated Hybrid Lipid Nanoparticles Amplify the Potency of mRNA Vaccine via Oxygen Generation and STING Activation.

Messenger RNA (mRNA) vaccines have exhibited enormous potential in the treatment of human diseases; however, their widespread applications are curtailed by the induction of reactive oxygen species during mRNA translation, which greatly compromises the translation efficiency. Herein, we present a robust strategy with the capability to substantially enhance the efficacy of the mRNA vaccine through promoting mRNA translation and stimulator of interferon genes (STING) activation. The strategy entails the coassembly of small-sized manganese oxide nanoparticles (Mn3O4 NPs) with lipid nanoparticles (LNPs) as the hybrid delivery vehicle (MnLNPs) for the fabrication of mRNA vaccine. The acquired MnLNPs proficiently scavenge reactive oxygen species (ROS) produced during mRNA translation and facilitate oxygen production, thereby boosting adenosine triphosphate (ATP) synthesis and augmenting mRNA translation. Furthermore, MnLNPs effectively bolster the antigen presentation and maturation of dendritic cells by activating the cGAS-STING pathway. In vivo studies demonstrate that mRNA vaccine prepared from MnLNPs markedly enhances the translation of antigen-encoding mRNA compared to LNPs, leading to superior antitumor efficacy. The tumor-suppressive capabilities of MnLNPs@mRNA are further promoted by synergizing with immune checkpoint blockade, underscoring MnLNPs-based mRNA vaccine as an exceptionally promising avenue in cancer immunotherapy.

Greatly boosted H2O2 activity in two-electron water oxidation reaction on Zn-based catalysts by doping engineering

Electrocatalytic production of hydrogen peroxide (H2O2) by two electron water oxidation reaction (2e-WOR) is an environmental process with low cost and devoid of H2O2 storage and transportation. ZnO is one of the important promising 2e-WOR catalysts with relatively high activity and selectivity of H2O2. However, the active sites and the effects of oxygen defects of ZnO remain unknown, which hampers the further improvement in H2O2 formation. To explore the active sites and develop Zn-based catalysts with high performance, Ni, Cu and Co ions are chosen to form M0.1Zn0.9O (M = Ni, Cu and Co) catalysts. Combining the experimental results with density functional theory (DFT) calculations, the active site of 2e-WOR on Zn-based catalysts is first discovered to be the 3-coordinated surface Zn without surface oxygen defects since oxygen defects result in a strong interaction of ·OH with catalyst and then impede the 2e-WOR process. Catalysts with high activity and selectivity for 2e-WOR should have small nano-particle sizes without oxygen defects. Co0.1Zn0.9O is obtained with high activity (35.3 mmol min−1·gcat−1) and selectivity (82%) of H2O2 at 3.2 V vs RHE. This work provides valuable perspectives for designing and developing high-performing catalysts in 2e-WOR reaction.

Highly stable platinum catalyst encapsulated with mesoporous silica for preferential oxidation of CO in H2-rich stream

Preferential oxidation of CO in H₂-rich streams (PROX) is an effective method to reduce trace amounts of CO for proton exchange membrane fuel cells. However, developing highly stable catalysts for practical reaction conditions achieving the 50:50 goal—below 50 ppm CO concentration with 50% O₂ selectivity—remains challenging. Here, we report a highly stable Pt nanoparticle catalyst encapsulated in mesoporous silica (Pt@mSiO2) loaded on a monolith, which achieves the 50:50 goal. Over 1000 h of continuous PROX reactions in the presence of H2O and CO2, the catalyst maintained an average CO concentration of ca. 33 ppm and O2 selectivity of ca. 50%. The excellent activity, selectivity, and long-term stability of Pt@mSiO₂, which can be attributed to the small size (ca. 2.7 nm) of Pt nanoparticles stably encapsulated in interconnected micro- and meso-porous silica without agglomeration, offer great potential for practical PROX applications.

An Efficient Analytical Method for Determining Transition Temperatures in Core‐Shell Spin Crossover Nanoparticles Described by an Extended Ising‐Like Model

AbstractThis contribution is dedicated to the analysis of the size and interaction parameters effects on the thermal properties of square‐shaped cross‐spin transition core‐shell nanoparticles. The present study is carried out by varying the shell size at fixed core size and vice versa. In this problem, the core and shell are active from the spin transition point of view, while having different properties in terms of ligand field (transition temperatures) and interactions. The resulting nanoparticle is described by an Ising‐type model including the three interaction parameters JCC, JSS and JCS coupling core‐core, shell‐shell and core‐shell sites, respectively. The thermodynamic investigations have been carried out in 3 different ways: (i) by Monte Carlo Entropic Sampling (MCES) for small size nanoparticles ( ) (ii) by usual Monte Carlo Metropolis for higher dimensions (iii) by an analytical method deducing the equilibrium temperature of the system from the various local environments. We demonstrate that, as long as a clear plateau region occurs in the thermal‐dependence of the high‐spin fraction, an excellent agreement is obtained, allowing to predict analytically the evolution of the transition temperatures. The limitations of the method are discussed in the case of strong interference between the thermal dependences of the core and shell.

Fabrication of apigenin and adenosine-loaded nanoparticles against doxorubicin-induced myocardial infarction by reducing inflammation and oxidative stress.

The study's goals are to fabricate PLGA nanoparticles (PNPs) loaded with apigenin (AP) and adenosine (AD) using a microfluidic preparation method to a standard emulsification method and investigate the possible heart-protective effects of AP-AD PNPs made using the emulsification method. Compared to microfluidics, the emulsification method fabricated small-size nanoparticles, which are better at encapsulating drugs, retaining more drugs, and having a low viscosity for the myocardial infarction (MI) injection. TheMI model was developed using SD rats injected under the skin with 85mg/kg doxorubicin (DOX) for 2 days. The metabolic results showed that our AP-AD PNPs accelerated the blood flow in rats with MI, which increased the amounts of AP and AD in the circulatory system. This led to significant improvements in the cardiac index and lower amounts of AST, LDH, and CK in the blood. A histopathological study using Hematoxylin&eosin, and TUNEL staining showed that cardiac function had improved and apoptosis had decreased. Moreover, tests that checked the amounts of IL-6, TNF-α, NO, GSH, MDA, and SOD showed that AP-AD PNPs may help treat MI by reducing oxidative stress and inflammation, making it a potentially useful therapeutic approach.

Synthesis and Characterization of Zirconium Dioxide Nanoparticles in Various Liquid Media by Nd:YAG Pulse Laser Ablation and Its Antibacterial Application

The issue of antibiotic resistance by bacteria has been studied to develop a new agent to inhibit bacterial activity. Recent studies have reported on nanoparticles promising antibacterial properties. Zirconium dioxide nanoparticles (ZrO2 NPs) have emerged as potential antibacterial agents for gram-negative bacteria. Nevertheless, there remains a gap in research done on producing stable nanoparticles. Additionally, it studies the impact of the liquid environment in the synthesis to keep a small size. In this present work, ZrO2 NPs have been successfully synthesized in various liquids by pulse laser ablation using the Nd:YAG laser. The laser was ablated on the surface of a zirconium metal plate in different liquid media, such as deionized water, ethylene diamine, and chitosan solution. Furthermore, the liquid media used has an effect on the characteristics of ZrO2 NPs and their antibacterial properties. An investigation of scanning electron microscope images reveals that ZrO2 NPs in deionized water, ethylene diamine, and chitosan solutions have a spherical morphology with diameters measuring around 24.33 nm, 19.76 nm, and 15.05 nm, respectively. The antibacterial effect of ZrO2 NPs in chitosan solution against E. coli bacteria is assessed by measuring the diameter of the inhibition zone (DIZ), which has greater colloidal stability than the other liquid media. The findings indicate that the stability and small size of nanoparticles enhance the ability to inhibit the growth of bacteria.

Enzymatic synthesis of long-branched or short-branched starches with uniform molecular size

Branched starches are gaining increasing attention due to their applications in food nutrition, drug delivery systems, and material science. In this study, two types of highly branched starches with uniform molecular size (hydrodynamic radius (Rh) = 10–20 nm), characterized by long and short branches, respectively, were successfully prepared using branching enzyme (BE) and 4-α-glucanotransferase (4αGT). The findings indicate that BE preferred longer chains as substrate by showing higher activity on amylose-containing native starches and modified starches with longer chains generated by 4αGT since the longer linear chains offer more potential sites for the catalysis of α-1,6-linkage transfer by BE from Rhodothermus obamensis (RoBE). These two highly branched starches show potential as materials for developing novel small-sized starch nanoparticles for encapsulation of functional bioactive compounds and ingredients.

Expanding the Toolbox of Oxidants: Controllable Etching of Ultrasmall Au Nanoparticles toward Tailorable NIR-II Luminescence and Ligand-Mediated Biodistribution and Clearance.

Oxidant-driven and controllable etching of small-sized nanoparticles (NPs, d < 3 nm) and tailorable modulation of their optical properties are challenging due to the high reactivity and complicated surface chemistry. Herein, we present a facile strategy for highly controllable oxidative etching of ultrasmall AuNPs and tailorable modulation of luminescence. The proper choice of a moderate oxidant, ClO-, could not only selectively etch the Au(I)-thiolate motifs from the nanoparticle surface at the subnanometer scale but also retained a stable metallic core structure without aggregation, which impressively prompted the wide-range luminescent switching from the visible to second near-infrared (NIR-II) region. The resultant oxidized AuNPs displayed highly luminescent NIR-II emission with a quantum yield of 3.0%, excellent monodispersed stability, ideal biocompatibility, and tunable shielding effects against protein adsorption. With those outstanding features, oxidized AuNPs could be utilized as nanoprobes for long-lasting and in vivo bioimaging of associated metabolic behaviors with distinguishable organ-specific targeting capabilities and ligand-mediated kinetics in nanoparticle clearance. These findings expand the toolbox of oxidants for the controllable synthesis of NIR-II nanoprobes and open up a path for exploring diverse ligand interactions on ultrasmall AuNPs with organs or tissues that might advance their monitoring applications for a wide range of clinically important diseases.

Cauliflower-like Pd/MoC||Mo2C/C heterostructure as an efficient trifunctional catalyst for formic acid oxidation, hydrogen evolution, and oxygen reduction reactions

The use of Pd-based catalytic materials as electrocatalysts for formic acid oxidation reaction (FAO), hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) has been well-established for some time. The incorporation of a second phase can markedly enhance the electronic properties of the composites. The combination of different compounds with superior electronic properties is crucial for the design and preparation of catalysts with optimal catalytic activity and stability. In this study, a novel cauliflower-like Pd/MoC||Mo2C/C composite with heterostructure is synthesised, which exhibits excellent catalytic activity and long-term stability against FAO, HER, and ORR. The high-temperature treatment results in the formation of small-sized Mo₂C and MoC nanoparticles on the carbonaceous substrate, thereby exposing a greater number of Mo and Mo-C active sites. The formation of heterostructures between Mo₂C and MoC optimises the electronic structure of the composite, thereby facilitating enhanced reaction processes. In terms of FAO, the mass activity of Pd/MoC||Mo2C/C is 1.87 A mgPd−1, which is 2.75 times higher than that of Pd/C (0.68 A mgPd−1). As for the HER, a much lower overpotential of 28 mV is required to achieve a current density of 10 mA cm−2 compared to Pd/C (40 mV). Fortunately, Pd/MoC||Mo2C/C also shows excellent ORR activity with a half-wave potential of 0.798 V and the maximum current density of approximately 5.73 mA cm−2 in alkaline electrolyte. These findings may contribute to the development of other noble metal-based materials loaded on intermetallic compounds with stable and effective electrocatalytic performance.

Polyvinyl alcohol assisted citrate based reduction of gold(III) ions: Theoretical design and experimental study on green synthesis of spherical and biocompatible gold nanoparticles

In this study, we demonstrate the synthesis of small gold nanoparticles (typically 8–10 nm) through a green synthesis approach. This method involves utilizing chloroauric acid as the gold precursor, trisodium citrate as a mild reducing and co-capping agent, and polyvinyl alcohol (PVA), as a co-capping and shape-directing agent. This novel synthesis method stands alone as a protocol that involves just mixing the reagents at room temperature and allowing the reaction to proceed at ambient temperature without any disturbance. In the absence of PVA, spherical particles are not formed and the reaction mixture slowly turns black followed by precipitation.The synthesis process was meticulously tracked using time-resolved monitoring of the growth of the localized surface plasmon resonance (LSPR) by UV-vis spectroscopy and transmission electron microscopy. The as-prepared colloidal gold solution was bright red, attributed to the small size (≤10 nm) and spherical geometry of nanoparticles. This colloidal solution could be stored indefinitely at room temperature without precipitation or a change in its absorption profile. The nanoparticles remained stable in adverse conditions such as 100 mM NaCl solution, 1 × PBS and cell culture medium. Additionally, they could be easily loaded with drugs like doxorubicin by adsorption. The particles were thoroughly characterized using a range of techniques, including UV-vis spectroscopy, attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), high-resolution transmission electron microscopy (HRTEM), hyperspectral-enhanced dark field microscopy (HEDFM), dynamic light scattering (DLS), and X-ray photoelectron spectroscopy (XPS). Cell viability tests conducted on 2D cell lines and 3D spheroids revealed negligible toxicity even at high concentrations. Furthermore, we demonstrated that an advanced version of conventional diffusion-limited aggregation (DLA) schemes, which allows individual clusters to move freely within a domain to form larger aggregates, can effectively replicate the intricate interactions between chloroauric acid, trisodium citrate, and PVA, the agents involved in the synthesis of gold nanoparticles.

In situ generation of cuprous oxide in metal-organic framework for significantly enhanced room-temperature ammonia sensing: Synergy enabling excellent sensitivity and selectivity

Development of effective strategies to improve the response sensitivity of metal-organic frameworks (MOFs) to target gases is imperative to further enhancing their application potential in gas sensing. In this work, series of CuHHTP/Cu2O (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) composites are successfully constructed by in-situ electrochemical reduction treatment of CuHHTP, and the changing trend of first increasing and then decreasing with increase of CuHHTP electrochemical reduction degree for their sensitivity to NH3 detection is revealed. When the average size of Cu2O nanoparticles generated in CuHHTP is 3.6 nm, the corresponding CuHHTP/Cu2O-A composite exhibits the best NH3 sensing performance compared to pristine CuHHTP, including significantly enhanced response sensitivity, ultralow experimental detection limit of 10 ppb, superior selectivity, good reproducibility, and excellent response stability even after placed for 90 days. More impressively, thanks to integration and synergy of the uniformly-dispersed small-sized Cu2O nanoparticles with significantly enhanced adsorption activity and capacity for NH3, the released large amount of uncoordinated hydroxyl groups that can interact with NH3, as well as the active sites of the CuHHTP substrate itself, the 10 ppb experimental detection limit for the CuHHTP/Cu2O-A-based sensors is not only the lowest one reported in the past 10 years for NH3 sensors based on copper-containing MOF and oxide materials, but also superior to that of 0.1–1 ppm for the existing commercial NH3 sensors. This work opens the avenue for design and development of novel MOF-based sensing materials.

Effects of SiO2 Particle Size in Soggy‐Sand Electrolyte on Electrochemical Performance of Zinc‐Ion Batteries

AbstractThe presence of free water molecules in the aqueous electrolyte leads to serious side reactions at the interface, easy dissolution of the cathode material, and uncontrolled growth of zinc dendrites in Zn‐ion batteries, which hinders their practical applications. Here, we propose a type of SiO2‐based soggy‐sand electrolyte (ZnSO4+MnSO4 electrolyte with SiO2, SiO2‐ZMSO4) and focus on the effect of the SiO2 nanoparticle size on the performance of soggy‐sand electrolyte. It is found that SiO2 with smaller nanoparticle size provides higher porosity, and the SiO2 network‐formed can effectively trap the free water in the electrolyte, which increases the ionic conductivity of electrolyte, widens working voltage window, and decreases the internal resistance of batteries. As a result, the Zn//MnO2 batteries with 20 nm SiO2‐based soggy‐sand electrolyte show stable cycling performance and rate capacities. The specific capacity of the battery can be maintained at 198.5 mAh g−1 after 1200 cycles at 1 A g−1 without capacity degradation. The specific capacity can be increased by 100 mAh g−1 even at a high rate of 5 A g−1. This study provides the rule of particle selection for the development of aqueous soggy‐sand electrolytes used in aqueous rechargeable batteries.

A Comprehensive study on the reduction of 4-NP using Au/Polydopamine catalysts

Here, Au/polydopamine (Au/PDA) catalysts were prepared by gold sol adsorption (Au/PDA(Sol)), PDA in situ reduction (Au/PDA(PDA reduction)) and DA in situ reduction (Au/PDA(DA reduction)). The factors that influence the performance of Au-PDA on the reduction of 4-nitrophenol (4-NP), were systematically studied for the first time. The catalytic performance of Au/PDA(Sol) is the best because of the uniform and small size of Au nanoparticles (NPs) (3.2 ± 0.7 nm), with a turn over frequency (TOF) of 10125 h−1, a mass-normalized rate constant (k’) of 33360 min-1gAu-1 and an apparent activation energy (Ea) of 11.39 KJ/mol. It is confirmed that there are electronic interactions between Au and the catechol hydroxyl groups and imino groups of PDA. Some unreduced Au3+ ions can be reduced in situ by NaBH4 during the catalytic reaction, forming ultra small Au NPs and leading to a good initial catalytic activity, especially for Au/PDA(DA reduction). This work systematically studied the influencing factors in catalysis for Au/PDA, providing guidance for the preparation and industrial application of PDA supported noble metal catalysts.

Interface engineering of AgI/(P, K)-g-C3N4 novel S-scheme heterostructures as a highly efficient photocatalyst for RhB degradation

In this study, we developed an in-situ deposition method to load small-sized AgI nanoparticles as an oxidative photocatalyst (OP) onto phosphorus (P) and potassium (K) co-doped two-dimensional porous g-C3N4 (PK-CN-N) as a reductive photocatalyst (RP), forming an S-scheme heterojunction photocatalyst AgI/PK-CN-N. PK-CN-N achieved morphology control and element doping, leading to surface functionalization and heterostructure formation for the AgI/PK-CN-N photocatalyst. Notably, the 50AgI/PK-CN-N composite demonstrated an approximately 95 % removal efficiency for RhB within 30 minutes, 17.6 times higher than pure g-C3N4, surpassing most reported g-C3N4-based photocatalysts. The enhanced photocatalytic efficiency is attributed to the surface modification strategy and heterostructure formation of g-C3N4, which broadens the visible light response range, increases the number of active sites, improves the separation of photogenerated electron-hole pairs, and enhances REDOX capabilities. The band structure of the composite was elucidated through Mott-Schottky analysis and UV–vis DRS. The formation of the AgI/PK-CN-N S-scheme heterojunction and its charge transfer mechanism was confirmed through XPS, band structure analysis, KPFM, and EPR spectroscopy. Experimental data confirmed the presence of a strong and effective interface electric field between the two semiconductors, leading to band bending and accelerated charge separation. Additionally, the introduction of small-sized AgI semiconductors enhanced the exposure of the coupling interface, further improving catalytic performance. The reusability and lifespan of the catalyst were also analyzed, showing that after four cycles, the photocatalytic activity remained above 92 %.

Uniformly dispersed FeOOH nanoparticles supported on alumina-carbon nanosheets for Cr(VI) removal

The mesoporous alumina-carbon nanosheets supported FeOOH nanoparticles were prepared by a facile and cost-effective hydrothermal synthesis for Cr(VI) removal in the wastewater, based on the affinity and selectivity of FeOOH and the accelerated mass transfer of nanosheet structure. The prepared nanoparticles with a small size of 2–5 nm were uniformly dispersed over the alumina-carbon nanosheets, attributed to the metal interaction and mesoporous confinement. The acid property after the introduction of alumina induced a positive charge on the surface of the adsorbent, which could enhance the adsorption of negatively charged metal ions. The Cr(VI) removal efficiency with the Al/Fe ratios showed a similar volcano curve. When Al/Fe ratio was around 3.3 and pHpzc was about 7.1, the adsorbent exhibited the best Cr(VI) removal efficiency of 99.4 %, owing to a large specific surface area, and small nanoparticle size, combined with abundant moderate-strong acid content of 294.5 μmol NH3 g−1.The Langmuir model could describe the adsorption process well, and the kinetic data was consistent with Pseudo-second-order. The thermodynamics revealed that the reaction process was spontaneous and endothermic. The adsorbent maintained a high removal efficiency of more than 80 % after running for five cycles and kept over 95 % under ionic co-existence and natural water conditions. Therefore, this study provides a new insight into the rational construction of efficient adsorbents with low-cost Cr(VI) removal.

Influence of Pd, Pt and Au nanoparticles in the photocatalytic performance of N-TiO2 support under visible light.

In this article, we report the modification and photocatalytic evaluation of commercial TiO2-P25 under visible light for methyl orange (MO) dye degradation under visible light. The activity of materials doped with N, Pd, Pt and Au on to the TiO2-P25 was evaluated, with optimal photocatalytic performance achieved using Au nanoparticles doped on an N-functionalized titania surface. X-ray diffraction (XRD), physical nitrogen adsorption/desorption isotherm curves, transmission electron microscopy (TEM), diffuse reflectance spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to study the structural and textural properties of the samples. The chemical species present in the bulk and surface of the catalysts were identified using X-ray photoelectron spectroscopy (XPS) and microwave plasma-atomic emission spectroscopy. The results show that Au/N-TiO2 photocatalyst presents a remarkable enhanced activity for MO dye degradation, under visible light illumination, reaching 100% after 4 h. The enhanced photocatalytic activity using this composite is attributable to the well-dispersed and small size of Au nanoparticles, large surface area, reduction of band-gap energy and the interaction between nitrogen and Au which promoted a synergistic effect. This article is part of the discussion meeting issue 'Green carbon for the chemical industry of the future'.

Non-platinum-based electrocatalysts for high performance acidic hydrogen evolution reactions in proton exchange membrane water electrolysis

To replace Pt for economical and scalable H2O to H2 conversion in proton exchange membranes (PEM) water electrolysis, efforts are being made to find cost-effective catalysts that delicately co-ordinate key parameters such as high mass activity and long durability. We found that by engineering the small size (<5 nm) of RuMo bimetallic nanoparticles (NPs) on carbon nanotube (CNT) with a strong metal-support interaction (SMSI) effect, we could obtain Mo2.8-Ru@CNT-2.8 catalysts with optimal activity and stability in acidic HER (Mo amount is 2.8 wt% and NPs size is about 2.8 nm). Experimental and theoretical studies reveal that reducing the size to about 2.8 nm can simultaneously obtain the optimal Gibbs free energy of H intermediate adsorption and the bonding energy between Ru-Ru/Ru-Mo, which contribute to the improvement of the catalytic activity and stability of Mo2.8-Ru@CNT-2.8. In addition, Mo doping can greatly increase the formation energy of Ru vacancies, which contribute to the improvement of the catalytic stability of Mo2.8-Ru@CNT-2.8. Specially, the optimized Mo2.8-Ru@CNT-2.8 catalyst represent an advance in mass activity (4.4 A mg−1Ru) compared to commercial Pt/C catalysts (3.1 A mg−1Ru) and high per-site activity (32.7 s−1) under acidic conditions while remaining the excellent stability. At the same time, Mo2.8-Ru@CNT-2.8 as a cathode in the proton exchange membrane (PEM) water electrolyser exhibits excellent cell voltages with a Ru loading of 0.06 mgRu cm−2 (1.7 V to 1 A cm−2), 0.12 times that of commercial Pt/C with a Pt loading of 0.5 mgPt cm−2 (1.74 V up to 1 A cm−2), and maintains long-term stability for 700 h at 1 A cm−2.

Oxygen vacancy-enriched WO3 hierarchical tubes inherited from pine needle for the enhanced detection to ppb-level hydrazine at near room temperature

It is of great importance to develop low-temperature gas sensors for monitoring hydrazine (N2H4) with high toxicity and easy explosion. However, how to highly sense its ppb-level concentration remains challenging. For this purpose, biomorphic WO3 structure replicated by small-size nanoparticles was simply prepared though air calcinations of tungsten salt-immersed pine needle (PN) template. The mesoporous WO3-PN tubes with pore volume of 0.096 cc·g−1 had relatively large specific surface area (38 m2·g−1) for exposing more active sites, as well as rich oxygen vacancies (g = 2.005) and small band gap for promoting electron migration. With the assistance of W6+ Lewis acid catalytic sites, such unique multilevel structure facilitated the rapid transport and adsorption of basic N2H4 molecules, as well as their chemical reactions with high content of oxygen species (37.4 %) in sensing layer, thus first achieving the highly sensitive detection of ppb-level N2H4 gas at near room temperature. At 50 °C, WO3-PN sensor exhibited ultra-high response (S = 307), fast response time (Tres = 16 s) for 1 ppm N2H4, and low actual detection concentration (5 ppb). These key indicators were remarkably superior to reported semiconductor gas sensors. In addition, the enhanced low-temperature sensing mechanism of WO3-PN sensor was explored by means of analytical tests and DFT calculations.