Flexible transition metal nitrides (TMNs) are considered key candidate materials for constructing next-generation high-performance flexible sensing devices. However, their strong metal-nitrogen bonds require high-temperature synthesis, which tends to cause spontaneous aggregation into three-dimensional bulk materials, making it difficult to obtain ultrathin two-dimensional materials suitable for flexible devices. This study proposes an innovative rapid and nondestructive microwave crystallization method. By ingeniously leveraging the abundant free electrons in quasi-metallic TMN nanostructures, electromagnetic irradiation induces efficient microwave heating, achieving exceptional crystallization within 20 s. This method effectively circumvents the sintering of ultrathin nanostructures inherent to conventional high-temperature annealing and increases the specific surface area of the product by more than 10-fold. Based on this method, dense and robust flexible TMN films with ultrahigh specific surface area and excellent chemical stability have been successfully obtained, enabling highly sensitive surface-enhanced Raman spectroscopy (SERS) detection of polycyclic aromatic hydrocarbons and nanoplastics.

In the realm of surface-enhanced Raman spectroscopy (SERS), the structure of Raman scattering substrate is crucial for determining the detection's sensitivity and stability. In this work, a combined sol-gel, hydrothermal, and freeze-drying strategy is proposed to prepare MoWO aerogel self-assembled from ultrathin nanowires with a diameter of about 2 nm. The MoWO aerogel has high surface area, abundant oxygen vacancies, and a narrow bandgap. Evaluated as an effective substrate for SERS applications, the MoWO aerogel exhibits pronounced localized surface plasmon resonance at 682 nm and possesses a narrowed bandgap of 2.12 eV. The detection limit of MoWO aerogel for the probe molecule Rhodamine 6G (R6G) is as low as 1 & times; 10-10 M, with an enhancement factor (EF) as high as 7.2 & times; 106. Significantly, it still maintains its intact structure and high SERS activity under long-term high-temperature treatment and strong laser irradiation, demonstrating exceptional chemical stability.

Per-and polyfluoroalkyl substances (PFAS) represent a class of emerging contaminants with significant environmental and health risks, yet their rapid and sensitive detection in complex water matrices remains challenging. In this work, we report an innovative approach that integrates surface-enhanced Raman scattering (SERS) with ion-pair extraction strategy for rapid detection of PFAS contaminants in water. Three-dimensional NiFe-layered double hydroxide (NiFe-LDH) nanosheet arrays decorated with plasmonic silver nanoparticles (AgNPs) were fabricated as SERS substrate, exhibiting an ultra-sensitive SERS performance with enhancement factor (EF) of 109. Moreover, a 4-mercaptopyridine (4-MPY)-mediated ion-pair extraction strategy was developed, significantly improving the detection sensitivity for anionic PFAS, such as perfluorooctanoic acid, perfluorohexanoic acid, perfluorobutanoic acid, and potassium perfluorobutanesulfonate at trace concentration of 1 ppb. This method established a quantitative correlation between 4-MPY and total PFAS (& sum;PFAS) via complex formation and phase transfer. The feasibility of semi-quantitative and multicomponent PFAS detection was demonstrated. Finally, the practical applicability of the SERS combined with ion-pair extraction strategy was validated through the detection of PFAS in environmental water samples from River water of the East China, achieving a detection limit as low as 10 ppb, confirming its strong potential for on-site environmental monitoring.

Although surface-enhanced Raman scattering (SERS) technology has been widely applied in fields such as environmental pollutant monitoring and early cancer diagnosis, the design of universal substrates to enable high-sensitivity detection across multiple scenarios remains a pressing problem to be solved. In this study, an innovative defect engineering strategy was employed to successfully develop a SERS substrate based on molybdenum oxide sub-nanowires (MoO3-x Sub-NWs) with a high oxygen vacancy (Vo) concentration. This substrate uniquely combines the gradient defect states induced by Vo and the quantum confinement effect generated by the one-dimensional sub-nanostructure, thereby achieving the synergy of chemical enhancement and electromagnetic enhancement. Experimental results demonstrate that the substrate exhibits an enhancement factor as high as 7.8×107 for rhodamine 6G, achieves a LOD of 10-11 M for dyes such as methyl orange, and enables effective detection of various environmental pollutants including polychlorinated phenols, polycyclic aromatic hydrocarbons, and polystyrene microspheres. In terms of biomedical applications, based on the PCA-LDA model, the method achieves a three-category classification accuracy of 92.22% for hepatocellular carcinoma cells (HepG2), esophageal cancer cells (TE-1), and white blood cells (WBC), a discrimination accuracy of 90% for esophageal cancer subtypes (TE-1 and KYSE), and an ROC curve AUC value of 0.97. This study provides a new paradigm for the development of high-performance universal SERS substrates and possesses significant application value in the fields of environmental monitoring and non-invasive tumor diagnosis.

Traditional two-dimensional transition-metal nitrides used for surface-enhanced Raman scattering (SERS) suffer from difficulties in tuning their localized surface plasmon resonance (LSPR) effect, which does not match commonly used laser wavelengths, resulting in a low Raman enhancement factor and making trace detection challenging. A solvent-assisted molten salt technique is proposed to fabricate tungsten nitride (WN) microflowers assembled from a highly crystalline nanosheet with a large specific surface area of 82.1 m2/g. Using rhodamine 6G as a probe molecule, the substrate achieves a limit of detection as low as 2 × 10-11 M and an enhancement factor of 5.6 × 107, outperforming most nonprecious semiconductor SERS substrates. The excellent enhancement effect originates from the physical enhancement brought about by its LSPR effect. These WN microflowers exhibit excellent SERS performance and remarkable LSPR characteristics, while showing high sensitivity to typical high-risk environmental pollutants. They also possess excellent signal reproducibility, robust chemical stability, and strong anti-interference capability.

Disposable face masks (DFMs), while essential for public health protection, may introduce chemical exposure risks due to the presence of non-volatile organic chemicals (NVOCs). This study developed a non-target screening methodology based on ultra-high-performance liquid chromatography quadrupole-Orbitrap high-resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS) to comprehensively profile NVOCs in 225 DFMs of five types. A total of 44 NVOCs were tentatively identified, of which 31 exhibited positive toxicological responses in the ToxCast database. A multi-criteria risk prioritization scheme integrating regulatory lists, detected concentrations, and toxicity prediction based on the Cramer rules classified the chemicals into five levels of concern. In-silico genotoxicity assessment indicated low direct mutagenic potential for most compounds, though several exhibited structural alerts associated with indirect genotoxicity or non-genotoxic carcinogenicity. This work provides the first comprehensive screening and risk-based prioritization of NVOCs in DFMs, offering a valuable framework for safety evaluation and regulatory monitoring of chemical exposures from DFMs use.

The formation of transition metal nitrides (TMNs) necessitates overcoming extremely high reaction barriers, which renders the precise synthesis of TMN materials with tailored structures a significant challenge. Herein, we propose a molten-salt/template strategy for the accurate customization of TMNs featuring a rare single-crystal ordered mesoporous (SCOM) structure. By leveraging this strategy, 5 types of SCOM-structured TMNs-including WN, MoN, TiN, VN, and CoN were synthesized. Hydroxylation of templates and the subsequent formation of SCOM-structured metal oxides were identified as the key factors governing the formation of SCOM-TMNs. Interestingly, these SCOM-structured WN lack the intrinsic Raman signals typically possessed by non-metallic materials, effectively resolving the long-standing issue of background interference in non-metallic surface-enhanced Raman scattering (SERS) substrates. The WN substrate achieves an ultrahigh Raman enhancement factor of up to 7.5 × 107 and an ultralow detection limit of 1 × 10-12 M.

This perspective commemorates 50 years of surface-enhanced Raman scattering (SERS) by highlighting the paradigm shift toward rationally designed semiconductor substrates, enabling ultrasensitive and molecule-selective detection. Several enhancement strategies have been developed to effectively modulate the electronic band structure and charge transfer (CT) processes, such as energy level customization, amorphization, quasi-metallization, and morphology control, achieving high enhancement factors with good selectivity and stability. Moreover, semiconductor SERS substrates show broad prospects in the fields of bio-sensing and cancer diagnosis. Nevertheless, standardization gaps in substrate reproducibility and data comparability hinder its widespread adoption. Resolving these challenges through multi-stakeholder collaboration is essential to bridge the technology transfer gap and establish SERS as a core platform for next-generation inspection.

Glutathione serves as a common biomarkers in tumor diagnosis and treatment. The levels of its intracellular concentration permit detailed investigation of the tumor microenvironment. However, low polarization and weak Raman scattering cross-section make direct and indirect Raman detection challenging. This study designs an amorphous-crystalline urchin-like TiO2 (AC-UL-TiO2) for the accurate identification of GSH and GSSG. By synergistically regulating the crystalline core and amorphous shell, the bandgap structure is optimized, thereby enhancing charge transfer efficiency. AC-UL-TiO2 demonstrates excellent SERS performance in detecting dye molecules with good selectivity for mixed analytes. The enhancement factor (EF) for R6G is 6.89 × 106, and the limit of detection (LOD) is 10-10 M. A SERS-colorimetric dual-modality platform is developed based on the AC-UL-TiO2@DTNB system to accurately monitor GSH concentrations from 0 to 1000 µM, providing a robust dual-confirmation result. Importantly, combined with the principal component analysis method, the AC-UL-TiO2 SERS platform can directly distinguish GSH and GSSG molecules. Besides, direct SERS detection LOD for GSH and GSSG are 10-8 M, which is 100 times higher than that of indirect detection. These findings indicate that AC-UL-TiO2 holds potential for biomarkers trace detection in tumor microenvironments.

Compared with metal surface-enhanced Raman spectroscopy (SERS) substrates that exhibit no intrinsic Raman signals, nonmetallic SERS substrates often introduce bothersome background interference due to their strong inherent Raman scattering. Herein, we report the synthesis of single-crystalline mesoporous (SCM) TiN nanosheets─with a thickness of merely 2 nm─as a nonmetallic SERS substrate that is free of intrinsic Raman signals. To fabricate these unique SCM nanosheets, we developed a mixed-molten-salt nitridation strategy that incorporates both inert (KCl) and reactive (ZnCl2) molten salts. The Zn3N2 thin layer formed in situ via the nitridation of the reactive molten salt not only facilitates the formation of SCM-TiN nanosheets but also effectively suppresses the high-temperature sintering of the TiN nanosheets. As a nonmetallic SERS substrate, the SCM-TiN nanosheets exhibit an ultrahigh Raman enhancement factor of 2.71 × 108, an ultralow detection limit of 2.0 × 10-13 M, excellent signal reproducibility, and remarkable durability in corrosive environments. A particularly valuable finding is that the SCM-TiN nanosheets themselves have no intrinsic Raman signals, which eliminates the background interference commonly associated with traditional nonmetallic substrates and thus provides a strategy for the design of high-performance SERS substrates.

Surface-enhanced Raman scattering (SERS) is extensively employed for detecting organics, where its sensitivity and selectivity are strongly influenced by the properties of the SERS substrates. In this work, a simple hydrothermal synthesis followed by a subsequent reduction was used to prepare Au-CeO2 composite nanocubes as a new SERS substrate, in which the side length of the CeO2 cubes was 20~30 nm and the diameter of the Au nanoparticles was 5~25 nm. Using methylene blue (MB) and crystal violet (CV) as probe molecules, the lowest detection limit (LDL) of methylene blue (MB) on the Au-CeO2 composite nanocubes substrate was 10−7 M, and the maximum SERS enhancement factor (EF) was 2.6 × 105. As a result, the lowest detection limit (LDL) of crystal violet (CV) was 10−7 M, and the maximum enhancement factor (EF) was 3.7 × 104. The above results proved that the Au-CeO2 composite nanocubes had a quite good Raman enhancement effect, which could be used as a SERS substrate. Finally, a Raman enhancement mechanism is proposed for the Au-CeO2 nanucubes.

In surface-enhanced Raman spectroscopy detection, the structure of the Raman scattering substrate is critical to the sensitivity and stability of the detector. In this study, W18O49 ultrafine nanowire bundles are used as precursors to synthesize porous tungsten nitride (WN) through a nitriding treatment. As a typical transition metal nitride (TMN), these porous WN exhibit a strong localized surface plasmon resonance effect in the visible region, with a resonance peak centered at 672 nm. Significantly, WN as a substrate for detection of typical dyes exhibit strong Raman enhancement signals. In particular, the detection sensitivity for R6G has been significantly improved, with the lowest detectable concentration reaching an impressive 1 × 10-10 M, and the maximum enhancement factor is up to 1.62 × 107. Moreover, they even can maintain the detection performance in a variety of harsh environments, showing outstanding corrosion resistance, and oxidation resistance, which is not available on traditional noble metal and semiconductor Raman substrates.

Traditional high-temperature and high-pressure synthesis routes make transition metal nitride (TMN) grains prone to sintering and agglomeration, thus synthesis of architectures with high specific surface area and pore volume is an urgent problem to be solved for the applications of TMNs. Here, a general single-source precursor route is designed to synthesize cubic-phase γ-Mo2N multilayered hollow spheres with high specific surface area (191.3 m2 g–1) and pore volume (0.69 cm3 g–1) under relatively mild conditions. Furthermore, by changing the metal composition of the precursor through ion exchange, a series of TMN (WN, TiN, VN, NbN, MoN/WN, MoN/WN/TiN) multilayer hollow spheres with high specific surface area (178.6–193.7 m2 g–1) and pore volume (0.57–0.72 cm3 g–1) are prepared. Particle size of precursor is found to be a key factor affecting the crystal phase and composition of molybdenum nitride nanostructures, and hexagonal-phase δ-MoN hierarchical hollow spheres composed of nanosheets are synthesized by adjusting the precursor particle size. The γ-Mo2N multilayered hollow spheres exhibit enhanced Raman activity for applications in trace detection of polychlorophenol and microplastics. Harsh reaction pathways make transition metal nitride (TMN) grains susceptible to sintering. Here, the authors report a general route to synthesize multilayered TMN hollow spheres with high specific surface area from a single-source precursor.

Since the first synthesis of graphdiyne (GDY), it has been widely receiving a lot of attention and has great application prospects in many fields, such as energy storage, catalysis, and sensing. However, the complex deprotection treatment and long reaction time limit its mass production and applications. Here, we present a strategy for the silver-catalyzed deprotection-free rapid synthesis of GDY. Crystalline GDY was synthesized in 8 h at room temperature and atmospheric pressure, and after the reaction, Ag nanoparticles with an ultrathin diameter of 2-3 nm were formed in situ inside and on the surface of GDY. This Ag/GDY composite exhibits a high specific surface area of 672.3 m2 g-1 and strong surface plasmon resonance behavior, showing a strong surface-enhanced Raman scattering effect. The enhancement factor and the lowest detection limit for rhodamine 6G are 3.54 x 108 and 1 x 10-14 M, respectively. The Ag/GDY achieves the simultaneous enrichment and detection of polychlorophenols and ultrafine nanoplastics.

Preparation of crystalline fullerene (C-60) nanoarchitectonics with ultrahigh specific surface area is crucial for their practical applications. Here, solvated C-60 microtubes were prepared by an improved liquid-liquid interfacial precipitation method, and a seed-induced growth mechanism was proposed. These solvated C-60 microtubes were found to be converted into highly crystalline C-60 mesoporous microtubes by rapid microwave heating without any graphitization. The C-60 mesoporous microtubes show an ultrahigh surface area of 785.3 m(2) g(-1) and a pore volume of 0.86 cm(3) g(-1). Highly crystalline C-60 mesoporous nanobelts and nanowires with an ultrahigh specific surface area are also obtained by this method. As a new type of semiconductor substrate, the C-60 mesoporous microtubes exhibit exceptional Raman sensing performances, and the Raman enhancement factor is as high as 6.57 x 10(7). Experimental tests and density functional theory calculations demonstrate that the enhanced Raman activity can be attributed to an effective interfacial charge transfer within the C-60/molecule system.

Beyond noble metals and semiconductors, quasi-metals have recently been shown to be noteworthy substrates for surface enhanced Raman spectroscopy, and their excellent quasi-metal surface-enhanced Raman spectroscopy (SERS) sensing has demonstrated a wider range of application scenarios. However, the underlying mechanism behind the enhanced Raman activity is still unclear. Here, we demonstrate that surface hydroxyls play a crucial role in the enhancement of the SERS activity of quasi-metal nanostructures. As a demonstration material, quasi-metallic MoO2 single-crystal frameworks rich in surface hydroxyls have been shown to have 100 times higher SERS activity than MoO2 single-crystal frameworks without hydroxyl functionalization, with a Raman enhancement factor of up to 7.6 × 107. Experimental and first-principles density-functional theory calculation results show that the enhanced Raman activity can be attributed to an effective interfacial charge transfer within the MoO2/OH/molecule system.

Copper is a crucial catalyst in the synthesis of graphdiyne (GDY). However, as catalysts, the final fate of the copper ions has hardly been concerned, which are usually treated as impurities. Here, it is observed that after simple washing with water and ethanol, GDY still contains a certain amount of copper ions, and demonstrated that the copper ions are adsorbed at the atomic layers of GDY. Furthermore, we transformed in situ the copper ions into ultrathin Cu nanocrystals, and the obtained Cu/GDY hybrids can be generally converted into a series of metal/GDY hybrid materials, such as Ag/GDY, Au/GDY, Pt/GDY, Pd/GDY, and Rh/GDY. The Cu/GDY hybrids exhibit extraordinary surface enhanced Raman scattering effect and can be applied in pollutant efficient enrichment and detection.

Bismuthene, an emerging two-dimensional monoelemental material as a good candidate of the room-temperature topological insulator, has attracted considerable attention due to its layer-dependent narrow band gap, high carrier mobility, high stability, tunable electronic and optical properties, and easy transferability. Here, we give a comprehensive overview of bismuthene from synthesis to applications. First, the structures and properties of bismuthene are summarized based on the theoretical simulation and experimental results. Then, the synthesis methods of bismuthene, mainly including liquid phase exfoliation, wet-chemical method and epitaxial growth are shown along with the pros and cons of each. The wide applications of bismuthene in electro/photo-catalysis, sensors, biomedicine, batteries, supercapacitors, optoelectronics, and nonlinear optical devices are further discussed. Finally, we conclude the current status, remaining challenges, and possible research directions to advance this exciting field.

Due to the intrinsic layered structure, graphdiyne (GDY) strongly tends to form 2D materials, therefore, most of the current research are based on GDY 2D structures. Up to now, the synthesis of its ultrathin nanowires with a high aspect ratio has not been reported. Here, the ultrathin GDY nanowires with diameters below 3 nm are reported for the first time by a two-phase interface synthesis method, which has excellent crystallinity and an aspect ratio of more than 2500. Evidence shows that the GDY ultrathin nanowires are formed by the oriented-attachment mechanism of nanoparticles. The GDY ultrathin nanowires exhibit a significant quantum confinement effect, enhanced photoelectric effect, and promising applications in surface-enhanced Raman sensing.

A general polymerization‐induced strategy is developed to synthesize large‐area (100 cm2) transition metal nitride (TMN: TiN, MoN, WN, VN) porous arrays with high specific surface area (187.5–215.5 m2 g−1) for the first time, which also can be used to prepare TMN porous arrays uniformly doped with multiple elements. The formation of homogeneous organic/inorganic hybrid polymer precursors is a key factor in forming such TMN porous arrays. The TiN porous arrays exhibit an intense blue‐light localized surface plasmon resonance effect centered at 508 nm. The TiN porous arrays also show a remarkable surface‐enhanced Raman scattering (SERS) effect with a Raman enhanced factor of 5.7 × 107 and the lowest detection limit of 1.0 × 10−12 m. They show ultrahigh corrosion resistance and oxidation resistance, which are not available on traditional noble metal and semiconductor SERS substrates. These results suggest the possibility of the development of effective SERS substrates by using cheap TiN to replace the expensive commercial Au substrates.