The development of efficient electrocatalysts for alkaline hydrogen oxidation reaction (HOR) is crucial to realize the commercialized application of alkaline exchange membrane fuel cells. Platinum group metals (PGMs) have been extensively used as alkaline HOR catalysts because they exhibit high activity and stability. Currently, searching for methods to improve the catalytic activity and reduce the loading of PGMs is the main research interest of PGM-based electrocatalysts. The alloying method has been regarded as an effective strategy. In this review, we summarized various kinds of PGM-based alloys, including traditional random alloys, single-atom alloys, high-entropy alloys and intermetallic compounds, and highlighted the challenges and future directions regarding the development of advanced PGM-based alloys.

Low antibiotic utilization and inability to achieve real-time monitoring of pathological status and treatment processes often result in unsatisfactory performance against bacterial infection. Developing a targeting antibacterial nanoprobe combining imaging with stimulus-response antibiotic release is a promising strategy to precisely recognize lesions and enhance therapeutic efficacy for bacterial infection. In this work, we report a pH-responsive theragnostic nanoplatform for targeted imaging and local drug release at the bacterial infection site. The nanoplatform consists of the core-shell structure with persistent luminescence nanoparticles (PLNPs) as the core for autofluorescence-free luminescence imaging and zeolitic imidazolate framework-8 as the shell (ZIF-8) to act as a carrier for antibiotics cefazolin. The core-shell nanostructure is further conjugated with folic acid to facilitate the uptake and accumulation of the nanoparticles, and realize the autofluorescence-free targeted imaging of the infection site. The acidic microenvironment at the bacterial infection site enables ZIF-8 to decompose for specific drug release improve the performance in bacterial infection treatment. The developed pH-responsive nanotheranostic probe is promising for autofluorescence-free targeted imaging and therapy of bacterial infection.

In order to explore the M−N−C catalysts to replace noble-metal catalysts, Cu-based catalysts with different structures were obtained by pyrolysis of ZIFs with different structures precursors. Their structure-activity relationship was investigated. The results show that the Cu−NC-8 catalyst has abundant Cu−N active sites and N-doped carbon. The N atoms doped with the carbon backbone can adjust the electron density of adjacent C atoms, which is more conducive to the adsorption of O₂ on the electrocatalyst and improves the reaction rate.

Abstract

Cu−N−C catalysts with nitrogen-coordinated copper supported on carbon exhibits good catalytic performance in oxygen reduction reaction (ORR) and is considered as an excellent substitute for Pt catalyst. Achieving high electrocatalytic activity with low amount of copper is critical for improving the performance and reducing the cost of fuel cells. Here, we propose a Cu−NC-8 catalyst, using zeolitic-imidazolate-framework (ZIF), which is rich in N-coordination, as the precursor. High -emperature pyrolysis of the ZIF-8 provides metal anchored sites in the carbon skeleton, which promotes the construction of Cu−N active centers by the introduced Cu. The N-coordination also adjust the electron density of the C atoms to promote the adsorption of O₂ on the catalyst, which is beneficial to the ORR activity of 4e⁻ pathway. The 2.5 % Cu−NC-8 electrocatalyst shows high efficiency ORR activity (E _onset=1.0 V and E _1/2=0.82 V) and good stability.

Graphene attracted great interest in the electrochemical applications due to its stability and extremely high surface-area-to-mass ratio. Wet chemical and electrochemical synthesis allows affordable and single to multilayer graphenes with functional groups that contribute to surface accessibility, and electrolyte diffusion. These materials also have faradaic and pseudocapacitive reaction sites which enhance the electrochemical performance while altering their capacitive nature based on reaction type and density of these sites. Therefore heteroatom doping of graphene has been studied widely, and various outcomes, some of which have been controversial, were reported. In this study, we investigated the doping modification with multiple samples and also conduct a detailed physicochemical characterization. Oxidation-reduction and electrochemical exfoliation methods utilized to synthesize; pristine, nitrogen-doped, and phosphorus-doped reduced graphene oxide as well as the phosphorus-doped and pristine electrochemically exfoliated graphene materials. Samples have been characterized in terms of doping level, particle size, number of layers, defect density, and exfoliation homogeneity. Electrochemical measurements showed that surface wrinkling property among similarly large rGO particles (~9x) and small particle size (~2x) of graphenes are effective in determination of specific capacitance (Cspecific) and capacitive characteristic of samples while heteroatom doping doesn’t produce any significant change on these properties.

The self-assembly of anisotropic nanocrystals (stabilized by organic capping molecules) with pre-selected composition, size, and shape allows for the creation of nanostructured materials with unique structures and features. For such a material, the shape and packing of the individual nanoparticles play an important role. This work presents a synthesis procedure for ω-thiol-terminated polystyrene (PS-SH) functionalized gold nanooctahedra of variable size (edge length 37, 46, 58, and 72 nm). The impact of polymer chain length (Mw: 11k, 22k, 43k, and 66k g∙mol-1) on the growth of colloidal crystals (e.g. mesocrystals) and their resulting crystal structure is investigated. Small-angle X-ray scattering (SAXS) and scanning transmission electron microscopy (STEM) methods provide a detailed structural examination of the self-assembled faceted mesocrystals based on octahedral gold nanoparticles of different size and surface functionalization. Three-dimensional angular X-ray cross-correlation analysis (AXCCA) enables high-precision determination of the superlattice structure and relative orientation of nanoparticles in mesocrystals. This approach allows us to perform non-destructive characterization of mesocrystalline materials and reveals their structure with resolution down to the nanometer scale.

Two-in-one: This review discusses recent developments in the area of functional nanomaterials that are capable of detecting and removing fluoride through the use of agglomeration, electrostatic, H-bonding, ion exchange, coordination and π-π stacking interactions. This unique approach provides an effective way to detect and remove fluoride from water in the environment.

Abstract

Fluoride (F⁻) is a unique analyte because when in small quantities, it is beneficial and harmful when in larger or negligible quantities, leaving it essential for dual-purpose detection and removal from a water sample to prevent fluoride-caused health risks. F⁻ detection and removal using organic molecules and hybrid materials are extensively reported in the literature, but very few reports discuss dual-purpose detection and removal. Functional nanomaterials (FNM) based on nanoparticles, metal-organic frameworks, and carbon dots conjugated with fluorophore moiety are largely used for these purposes. Functional groups on nanomaterial surfaces exhibited various interactions such as agglomeration, electrostatic, hydrogen bonding, ion exchange, coordination and π-π stacking interactions, enabling dual-purpose detection and removal of F⁻. These materials offer unique properties such as tunable pore structure, size, and morphology coupled with large surface area and high thermal/chemical stability. Further, this perspective review discusses prospects for sustainable technologies and describes the advantages and disadvantages of using FNM based on its optical properties for detection and removal efficiency. We believe this is the first account that summarizes the single FNM that can be used for simultaneously the selective detection of F⁻ in aqueous media and its efficient removal.

The present study illustrates the advantages of the synergistically upgraded, sustainable, metal-free h-BN/PCN electrocatalyst for sulfamethazine sensor towards real-world samples using highly sensitive electrochemical techniques with good recovery percentages. Thus, the best performance for the electrochemical sensing of SMZ was exhibited by the h-BN/PCN nanocomposite.

Abstract

In the scientific community, developing a non-enzymatic detection tool for highly reliable and sensitive identification of the targeted biomolecules is challenging. Sulfamethazine (SMZ), a bacterial inhibitor frequently used as an antibacterial medicine, can cause antimicrobial resistance (AMR) in humans if taken in excess. Hence, there is a need for a reliable and rapid sensor that can detect SMZ in food and aquatic environments. The goal of this study aims to develop a novel, inexpensive 2D/2D hexagonal boron nitride/protonated carbon nitride (h-BN/PCN) nanohybrid that can function as an electrocatalyst for SMZ sensing. The as-synthesized material‘s crystalline, structural, chemical, and self-assembly properties were thoroughly characterized by XRD, HR-TEM, XPS, HR-SEM, FT-IR, and ZETA potential and electrochemical sensing capacity of the suggested electrodes was optimized using CV, EIS, DPV, and i-t curve techniques. The above nanohybrid of h-BN/PCN-modified GCE exhibits improved non-enzymatic sulfamethazine sensing behaviour, with a response time of less than 1.83 s, a sensitivity of 1.80 μA μM⁻¹ cm⁻², a detection limit of 0.00298 μM, and a range of 10 nM to 200 μM. The electrochemical analysis proves that the conductivity of h-BN has significantly improved after assembling PCN due to the large surface area with active surface sites and the synergistic effect. Notably, our constructed sensor demonstrated outstanding selectivity over a range of probable interferents, and electrochemical studies indicate that the suggested sensor has improved functional durability, rapid response, impartial repeatability, and reproducibility. Furthermore, the feasibility of an h-BN/PCN-modified sensor to detect the presence of SMZ in food samples consumed by humans has been successfully tested with high recovery percentages.

Amino acid transporters with different categories are highly expressed in intestinal epithelial cells for maintaining the essential metabolism of body. The zwitterioninc property of amino acid with α-amino and α-carboxyl also has tremendous potential to conquer the mucus barrier. Therefore, two glutamic acid (Glu)-derived amphiphilic block polymers [poly(lactic acid)-b-poly(glutamine)25 (PPQ) and poly(lactic acid)-b-poly(glutamate)25 (PPD)] were rational designed and further prepared Glu-derived zwitterionic micelles (PPQ-M and PPD-M) toward oral delivery. In comparison with PEG-M (PEG micelles), two Glu-derived zwitterionic micelles revealed superior mucus permeability. In addition, enhanced cellular internalization was also confirmed in both zwitterionic micelles, which were mainly mediated by multiple amino acid transporters. It was speculated that the uptake efficiency of PPQ-M was obviously higher than that of PPD-M due to PPQ-M with higher affinity of glutamine structural unit. Furthermore, the retrograde pathway played an important role in the intracellular transport of both zwitterionic micelles as well as transcytosis transport. Excellent villi absorption in situ of Glu-derived zwitterionic micelles were observed, which gave a convincing evidence for oral delivery potential. The results of this research demonstrated that Glu-derived zwitterionic micelles with unquestionable capacity of conquering intestinal mucosal barrier, have promising application toward oral delivery.

Replacing sluggish oxygen evolution reaction (OER) with electrocatalytic oxidation (ECO) of alcohols was a promising hotspot due to its advantages of requiring low potential, inhibiting mixing of gases, and forming value-added products. In the ECO of alcohols process, Fe electron centers of Fe-based layered double hydroxides (LDHs) can regulate the d band of LDHs overlap, optimize the active local structure of LDHs, and then enhance the electrocatalytic oxidation performance. In this work, CoxFey-LDHs nanosheets with different ratios of Co/Fe were prepared for selective ECO of benzyl alcohol (BA) to benzoic acid (BAC). Comprehensive characterizations revealed that the adjustment of bandgap and OH species adsorption of CoxFey-LDHs resulted in the appropriate thermodynamic driving force, which improved the electrical conductivity of CoxFey-LDHs and enhanced their ECO of BA. Especially, the as-prepared Co3Fe1-LDH showed intriguing electrocatalytic activity and only required a potential of 1.51 V (vs. RHE) to achieve a total current density of 50 mA cm−2 in alkaline solution containing 10 mM BA with a conversion (96.79%) of BA and selectivity (94.93%) of BAC, which was 60 mV lower than that of OER. After six cycles, Co3Fe1-LDH still achieved 94.74% conversion of BA and 92.10% selectivity of BAC without significant degradation.

Heterogenous BPDC-RuO2-CeO2 catalyst derived from Ce-BPDC MOFs can successfully enable the oxidation of amines to nitriles under mild conditions (1 atm O2, H2O as a solvent, room temperature). The catalytic system has the good compatibility with benzylic and aliphatic amines. Lewis acid-base pair [Ru–O–Ce-Vö] formed by the combination of acidic oxygen vacancy and basic oxygen pair Ru–O–Ce on the surface of the catalyst is the key factor for the catalytic activity. The mechanical experiments indicate that amines adopt the step-by-step dehydrogenation process to nitriles in this transformation. Moreover, the catalyst could be recycled up to six times without the evident loss of catalytic activity and the change of morphology.