Refrigerant leakage poses significant safety and environmental challenges in heating, ventilation, air conditioning, and refrigeration (HVAC&R) systems, particularly with the increasing use of highly flammable hydrocarbon (A3) refrigerants such as propane (R-290), ethane (R-170), butane (R-600), and isobutane (R-600a). Existing sensor technologies developed for traditional halogenated refrigerants are often unsuitable for accurately detecting low concentrations of hydrocarbons due to differences in chemical properties and flammability risks. This paper presents a comprehensive review of gas-sensing technologies applicable to A3 refrigerants, emphasizing both established and emerging technologies that could be adapted from other industries for use in HVAC&R applications. The sensor categories evaluated include metal–oxide semiconductor (MOS), catalytic, optical (photoacoustic spectroscopy—PAS, quartz-enhanced PAS, non-dispersive infrared—NDIR, fiber optic), acoustic (surface acoustic wave—SAW, quartz crystal microbalance—QCM), electrochemical, capacitive, and emerging nanomaterial-based sensors (C2N, sulfur-doped silicon carbide nanotube, surface plasmon resonance). Each technology was assessed based on critical parameters such as sensitivity, selectivity, response time, power consumption, and practicality for integration into HVAC&R systems. Although MOS, PAS/quartz-enhanced photoacoustic spectroscopy, and NDIR sensors demonstrate potential, limitations related to elevated operating temperatures, vibration sensitivity, and cross-selectivity remain significant concerns. Emerging technologies, including SAW, QCM, and novel nanostructured materials, exhibit promising performance characteristics such as room temperature operation, rapid response, high sensitivity, and compact size; however, they require further development and validation for reliability, long-term stability, and commercialization. This paper also identifies key gaps, challenges, and research opportunities, emphasizing the importance of developing robust calibration protocols and clearly defining operational conditions within HVAC&R systems to optimize sensor selection, safety, and system efficiency.

Tuning crystal structures of Mn nanomaterials on Enteromorpha prolifera biochar to enhance seawater purification.

Proton-conducting solid oxide fuel cells (PCFCs) represent a promising class of energy conversion technologies operating at intermediate to low temperatures. However, the development of efficient oxygen reduction reaction (ORR) catalysts remains a critical challenge for achieving practical performance in PCFCs. In this study, a series of K-doped Sr2Fe1.5Mo0.5O6-δ (SFM) perovskites with triple-conducting characteristics, synthesized through electrospinning into a nanofiber architecture, are presented as high-performance oxygen electrode materials. The SK30FM electrode demonstrates exceptional electrochemical performance, exhibiting a low polarization resistance of 0.062 Ω cm2 under wet air (3% H2O) at 750 °C, and delivering a peak power density of 645 mW cm-2 with decent short-term stability during fuel cell operation. These results highlight the significant potential of SFM-based perovskites as advanced oxygen electrodes for PCFCs, while also underscoring the advantages of electrospinning in fabricating nanostructured functional materials.

ZnO has been used as template to prepare and regulate the structures of functional nanomaterials. Due to the structural characteristics of Zn, its nanomaterials are generally considered inert. This study presents an innovative ZnO-templated synthesis of hollow N-doped carbon materials with atomically dispersed Zn single atoms (Zn SA/NC), where ZnO uniquely serves dual roles as both structural template and Zn precursor. The synthesized Zn SA/NC exhibits remarkable bifunctionality, demonstrating exceptional electrocatalytic activity for H₂O₂ reduction (detection limit: 3.7 µM, sensitivity: 1285.7 µA·mM⁻¹·cm⁻²) and intrinsic peroxidase-like activity for TMB oxidation. Leveraging these properties, we developed a dual-mode H₂O₂ detection platform integrating electrochemical and colorimetric readouts. The work challenges conventional views on Zn's catalytic inertness by revealing that Zn-Nₓ sites enable efficient charge redistribution, while the hollow architecture enhances mass transport. This strategy bridges the gap between structural control and atomic dispersion in single-atom catalyst design.

We analyze the degradation of the C60 fullerene under the action of hypochlorite (ClO-). The ClO- anion, produced by the human myeloperoxidase (hMPO) enzyme, is highly reactive and known for destroying bacteria and degrading nanostructured materials. In particular, previous studies show that hMPO can biodegrade nC60 nanoparticles in a short time, with hypochlorite playing a key role, though the exact mechanism is still unknown. In this work, we use density functional theory (DFT) calculations to investigate ClO- adsorption on water-covered fullerenes. We find that there is a strong tendency of hypochlorite to dissociate rather than remain molecularly adsorbed near the hydrated C60 surface. As a consequence of this reaction, the fullerene cage can be oxidized through the adsorption of carbonyl, epoxy, molecular O2, and ClO groups preferentially located in close proximity on the carbon network, while individual chloride ions remain hydrated and stabilized in the aqueous environment. The formation of domains of chemisorbed oxygen species, as reported here, reduces the number of C═C double bonds in the cage, thereby decreasing the structural stability of C60. Chlorination of the carbon surface is not energetically favored following ClO- bond cleavage. Most interestingly, our calculations reveal that the oxidation of the fullerene surface is frequently accompanied by the breaking of C-C bonds beneath the oxidized regions, resulting in hole formation in the carbon cage. We performed simulations of NMR, UV-vis, and ECD spectroscopies, which reveal well-defined spectral features that could be very helpful in identifying the structural transformations and chemical composition reported here for these nanosized carbon materials. According to our proposed atomistic mechanism, the dissociative adsorption of hypochlorite at various regions on the carbon network, along with the formation of molecular islands composed of oxidizing species, may lead to a generalized porous morphology of the cage consistent with experimental observations of significant structural transformations in hMPO exposed C60 solutions.

A comprehensive study on the molecular structure of TiO2 nanomaterials for efficient green hydrogen production

Facile fabrication of bulk nanostructured thermoelectric materials via ligand exchange-enabled integration of colloidal nanoparticles

Electrospun nanofibers for the adsorption and separation of pollutants from wastewater: New opportunities and recent advances.

The precise control of active site spatial structure is a central challenge in high-performance catalyst development and is particularly formidable in long-range disordered amorphous materials where inherent disorder prevents any deliberate engineering. Herein, we develop a DNA framework templated approach to program the fine structure of amorphous Cu nanomaterials, enabling tailorable electrocatalytic performance. Various Cu nanosheets were fabricated with effective modulation of electrocatalytic activity through control of the spatial arrangement of metal-binding sequences. We observed that Cu nanomaterials synthesized with different dimensionalities through the modulation of DNA nanostructures exhibit distinct electrocatalytic performance. Using the single-atom structural characteristics of Cu nanosheets, we performed density functional theory calculations to reveal that two-dimensional Cu nanomaterials possess the smallest energy gap and optimal glucose adsorption characteristics, which exhibit superior catalytic activity (3.65-fold and 2.70-fold) to other lower-dimensional counterparts. This work establishes a general methodology that uses prescriptive DNA blueprints to achieve programmable control over material structure and functionality, thereby providing a novel paradigm for crafting amorphous electrocatalysts and informing precision design in fields ranging from energy to biosensing.

While state-of-the-art alloy catalysts for the oxygen reduction reaction (ORR), a key process for future sustainable energy provision, rely on platinum-rich materials, alloys containing less noble metals may play an increasingly important role. In particular, Cu-Pt systems are among state-of-the-art electrocatalysts for O2 electro-reduction, demonstrating high activity and selectivity for the four-electron pathway. This study explores the behavior of Cu-Pt model thin film alloy catalysts using electrochemical scanning tunneling microscopy (EC-STM), a technique capable of detecting active sites and areas for surface catalytic processes under reaction conditions. Our findings indicate that the nature of active centers changes depending on whether the final product is H2O or H2O2, which can also be generated in parallel. Active centers are located on the (111) terraces for the four-electron ORR and shift to step defects if the hydrogen peroxide generation starts. On the other hand, the grain boundaries do not seem to contribute to the sample activity. These findings can be used in designing the shape of nanoparticles for improved nanostructured materials for energy applications.

In many nanostructured materials, such as those for implantation, it would be useful to control surface chemistry (e.g., ligand display) independent of mechanical properties. However, mesoscale heterogeneities native to soft elastomers limit spatial resolution. Here, we design interlayers composed of highly cross-linked 10-200 nm thin-film polydimethylsiloxane (TF-PDMS) for controlled ligand presentation on a range of hard and soft material interfaces. Nanometer-resolution chemical patterns (1 nm wide with a sub-10 nm pitch) assembled on highly oriented pyrolytic graphite (HOPG) are cross-linked to TF-PDMS and transferred to target materials (e.g., glass and soft PDMS) through plasma bonding. In this way, similar ligand densities are presented independently of the native material structure and modulus. We demonstrate that it is possible to leverage the difference in elastic modulus between the TF-PDMS interlayer and a soft PDMS substrate to generate mechanically induced microscale topographical control. Hierarchical nanoscale control over the interface architecture is also used to control the assembly of inorganic nanostructures (high-aspect-ratio gold nanowires) at the interface.

Alloy nanocrystals (NCs) have attracted considerable attention due to their broad applications. Herein, we present examples of ultrasmall (<5 nm) noble metal alloy NCs, i.e., AuPd and PdPt NCs, synthesized by sprayed water microdroplets. Electrons generated at the air-water interface of microdroplets serve as the primary reducing species, enabling metal ion reduction in the absence of added reductants. Through physical characterizations and mass spectrometry analysis, we elucidate the unique formation mechanism of NCs: the air-water interface of microdroplets simultaneously promotes the reduction and polymerization of precursor ions, followed by efficient surface reduction of the polymerized metal clusters, forming nuclei that undergo subsequent coalescence. The submillisecond reaction time prevents excessive crystal growth, yielding ultrasmall NCs featuring high-energy facets. This work provides insights into nonclassical nucleation and reduction of metal ions, and demonstrates the unique capabilities of microdroplet chemistry in the manipulation of nanomaterial growth dynamics and structures.

Bone regeneration is generally not effective in cases of extensive defects or inflammatory conditions such as osteoporosis and periodontitis. The traditional approach, such as bone grafting, comes with limitations, thereby making tissue engineering strategies a potential alternative. However, successful regeneration needs both osteogenesis and proper immunomodulation. Among all the immune cells, macrophages play a pivotal role in osteoimmunomodulation because of their plasticity in switching between pro-inflammatory (M1) and anti-inflammatory (M2) states. Nanostructured biomaterials can change the polarization of macrophages by altering important immune pathways such as NF-κB, MAPK, PI3K-Akt, JAK-STAT, NLRP3, Notch, and HIF-1 due to their large surface area and adjustable surface chemistry. These nanomaterials have also demonstrated excellent efficacy as carriers for targeted delivery of osteoimmunomodulatory bioactive agents, such as growth factors, cytokines, metal ions, and phytochemicals. In this review, we have discussed the crosstalk between the skeletal system, nanomaterials, and the immune system. We have also discussed the various types of nanomaterials and the design strategy of nanomaterials to modulate immune responses for enhanced bone regeneration. A brief discussion about the molecular pathways involved in osteoimmunomodulation and the modulation of these pathways by nanostructured materials for bone repair is also provided. Finally, we examined how nanomaterials can be engineered as delivery platforms for the controlled release of bioactive molecules involved in immune modulation and bone regeneration.

Electronic structure and property modulation of h-ScN nanomaterials

Organic ferroelectrics are of great interest in sustainable energy conversion, information storage, flexible electronics, and potential biomedical applications as soft implants, among many other applications. Despite their broad potential, the development of organic ferroelectrics has remained limited, with only a few known examples in solid-state systems, primarily due to the lack of well-established design strategies compared to inorganic systems. Bio-inspired supramolecular chemistry offers a path to create functional nanostructures that are water-processable and biocompatible. We report here on supramolecular charge transfer (CT) systems in which peptides are covalently linked to dyads of electron-donating and electron-accepting moieties, creating amphiphiles that self-assemble into nanoscale ribbons in water. The peptide chirality-induced symmetry breaking in these crystalline nanostructures not only results in second harmonic activity but also generates ferroelectric behavior across multiple CT systems, demonstrating a versatile supramolecular approach to the design of new organic ferroelectrics. Furthermore, culturing primary neuron cells on coatings of the ferroelectric materials promoted axonal growth and enhanced action potentials, indicating improved neuronal maturity facilitated by the polar structure of the ferroelectric nanomaterials. The supramolecular strategy used here holds promise to create new water-processable ferroelectric biomaterials, opening avenues for innovative applications in cell charge transfer, neuronal axon growth, peptide symmetry breaking, self-assembling peptides, supramolecular ferroelectrics proliferation, and bioelectronics.

High-Strength Nanostructured Glass-Ceramic Materials for Special-Purpose Equipment and Devices

Structural colors (SC), generated by light interacting with nano-structured materials, are responsible for the brightest and most vivid coloration in nature. Despite being widespread within the tree of life, there is little knowledge of the genes involved. Partial exceptions are some Flavobacteriia in which genes involved in a number of pathways, including gliding motility and polysaccharide metabolism, have been linked to SC. A previous genomic analysis of SC and non-SC bacteria suggested that the pterin pathway is involved in the organization of bacteria to form SC. Here, we focus on moeA, a molybdopterin molybdenum transferase. When this gene was deleted from Flavobacterium IR1, the knock-out mutant showed a strong blue shift in SC of the colony compared to the wild-type. The moeA mutant showed a particularly strong blue shift when grown on kappa-carrageenan and was upregulated for starch degradation. To further analyze the molecular changes, proteomic analysis was performed, showing the upregulation of various polysaccharide utilization loci, which supported the link between moeA and polysaccharide metabolism in SC. Overall, we demonstrated that a targeted approach, modifying a single gene identified by genomics, could change the optical properties of bacteria.

We report here how the polymerization-induced self-assembly approach can be implemented in orthogonally reactive dispersants to afford the preparation of nanostructured polymer networks. Precisely-defined PMMA-b-PLMA block copolymers self-assembling into different morphologies are first obtained in epoxy monomers through RAFT dispersion polymerization. The subsequent polymerization of the epoxide (through step growth or chain growth polymerization) affords the straightforward preparation of epoxy networks that integrate diverse BCP structures and exhibit significantly enhanced fracture toughness at extremely low block copolymer content (1%w/w).

Moving forward into a second golden age: Innovative and sustainable production of reprocessed starch aerogels.

The latest progress of nanostructured barium titanate crystal materials: Industrial synthesis, modification and application