Charge-transfer-driven ultrasensitive SERS sensing in a two-dimensional titanium carbonitride MXene.

Two-dimensional (2D) MXenes stand out as promising platforms for surface-enhanced Raman scattering (SERS) sensing owing to their metallic feature, various compositions, high surface area, compatibility with functionalization, and ease of fabrication. In this work, we report a high-performance 2D titanium carbonitride (Ti3CN) MXene SERS substrate. We reveal that the abundant electronic density of states near the Fermi level of Ti3CN MXene boosts the efficiency of photo-induced charge transfer at the interface of Ti3CN/molecule, resulting in significant Raman enhancement. The SERS sensitivity of Ti3CN MXene is further promoted through a 2D morphology regulation and molecular enrichment strategies. Moreover, prohibited drugs are detectable on this substrate, presenting the potential of trace-amount analysis on Ti3CN MXene. This work provides a deep insight of the SERS mechanisms of Ti3CN MXene and broadens the practical application of transition metal carbonitride MXene SERS substrates.

Chicoric acid advanced PAQR3 ubiquitination to ameliorate ferroptosis in diabetes nephropathy through the relieving of the interaction between PAQR3 and P110α pathway.

PURPOSE: This study aimed to examine the impact of CA on DN and elucidate its underlying molecular mechanisms of inflammation. METHODS: We fed C57BL/6 mice injected with streptozotocin to induce diabetes. In addition, we stimulated NRK-52E cells with 20 mmol/L d-glucose to mimic the diabetic condition. RESULTS: Our findings demonstrated that CA effectively reduced blood glucose levels, and improved DN in mice models. Additionally, CA reduced kidney injury and inflammation in both mice models and in vitro models. CA decreased high glucose-induced ferroptosis of NRK-52E cells by inducing GSH/GPX4 axis. Conversely, the ferroptosis activator or the PI3K inhibitor reversed positive effects of CA on DN in both mice and in vitro models. CA suppressed PAQR3 expression in DN models to promote PI3K/AKT activity. The PAQR3 activator reduced the positive effects of CA on DN in vitro models. Moreover, CA directly targeted the PAQR3 protein to enhance the ubiquitination of the PAQR3 protein. CONCLUSION: Overall, our study has uncovered that CA promotes the ubiquitination of PAQR3, leading to the attenuation of ferroptosis in DN. This effect is achieved through the activation of the PI3K/AKT signaling pathways by disrupting the interaction between PAQR3 and the P110α pathway. These findings highlight the potential of CA as a viable therapeutic option for the prevention of DN and other forms of diabetes.

Solution Blow Spinning of the Benzimidazole-Containing Aramid Nanofibers for Separators of Lithium-Ion Batteries.

Nanofibers based on high-performance polymers are much highlighted in recent studies toward advanced lithium-ion batteries. Herein, we demonstrate one scalable poly(ethylene oxide) (PEO)-assisted solution blow spinning strategy for the preparation of heterocyclic aramid (HA) nanofibers of poly(p-phenylene-benzimidazole-terephthalamide). The incorporation of PEO is essential to improve the spinnability of the HA solution achieved directly through the low-temperature-solution copolymerization process. Additionally, the flexible PEO with a strong H-bonding affinity is also utilized as the molecular zipper to adjust the pore size of the nanofiber membrane during the post-treatment process. The obtained membrane combines the good wettability of PEO to the liquid electrolytes, with outstanding mechanical strength, modulus, toughness, and environmental resistance of HA. The nonwoven separator membranes with a porosity of 83.6% exhibited excellent comprehensive performance, which could be seen not only on the high tensile strength (68.2 MPa), modulus (3.0 GPa), and toughness but also on the high thermal stability (Td > 405 °C) and flame retardancy, as well as the high electrolyte uptake (302.4%). The ion conductivity of the porous separators reached 0.83 mS/cm, with the bulk resistance dropping to 1/4 of the reference polypropylene separator. In the assembly of the Li/LiFePO4 half battery, the HA separators displayed improved discharge specific capacity and high retention in both rate capability and cycling tests, providing the potential industrial preparation for advanced lithium-ion batteries.

Exploring and Engineering 2D Transition Metal Dichalcogenides toward Ultimate SERS Performance.

Surface-enhanced Raman spectroscopy (SERS) is an ultrasensitive surface analysis technique that is widely used in chemical sensing, bioanalysis, and environmental monitoring. The design of the SERS substrates is crucial for obtaining high-quality SERS signals. Recently, 2D transition metal dichalcogenides (2D TMDs) have emerged as high-performance SERS substrates due to their superior stability, ease of fabrication, biocompatibility, controllable doping, and tunable bandgaps and excitons. In this review, a systematic overview of the latest advancements in 2D TMDs SERS substrates is provided. This review comprehensively summarizes the candidate 2D TMDs SERS materials, elucidates their working principles for SERS, explores the strategies to optimize their SERS performance, and highlights their practical applications. Particularly delved into are the material engineering strategies, including defect engineering, alloy engineering, thickness engineering, and heterojunction engineering. Additionally, the challenges and future prospects associated with the development of 2D TMDs SERS substrates are discussed, outlining potential directions that may lead to significant breakthroughs in practical applications.

Probing Oxidation Mechanisms in Plasmonic Catalysis: Unraveling the Role of Reactive Oxygen Species.

Plasmon-induced oxidation has conventionally been attributed to the transfer of plasmonic hot holes. However, this theoretical framework encounters challenges in elucidating the latest experimental findings, such as enhanced catalytic efficiency under uncoupled irradiation conditions and superior oxidizability of silver nanoparticles. Herein, we employ liquid surface-enhanced Raman spectroscopy (SERS) as a real-time and in situ tool to explore the oxidation mechanisms in plasmonic catalysis, taking the decarboxylation of p-mercaptobenzoic acid (PMBA) as a case study. Our findings suggest that the plasmon-induced oxidation is driven by reactive oxygen species (ROS) rather than hot holes, holding true for both the Au and Ag nanoparticles. Subsequent investigations suggest that plasmon-induced ROS may arise from hot carriers or energy transfer mechanisms, exhibiting selectivity under different experimental conditions. The observations were substantiated by investigating the cleavage of the carbon-boron bonds. Furthermore, the underlying mechanisms were clarified by energy level theories, advancing our understanding of plasmonic catalysis.

The Post-Curing of Waterborne Polyurethane-Acrylate Composite Latex with the Dynamic Disulfide-Bearing Crosslinking Agent.

The development of a dynamic network for commodity polymer systems via feasible methods has been explored in the context of a society-wide focus on the environment and sustainability. Herein, we demonstrate an adaptive post-curing method used to build a self-healable network of waterborne polyurethane-acrylate (WPUA) composite latex. The composite latex was synthesized via the miniemulsion polymerization of acrylates in the dispersion of waterborne polyurethane (PU), with commercial acetoacetoxyethyl methacrylate (AAEM) serving as the functional monomer. Then, a dynamic disulfide (S-S)-bearing diamine was applied as the crosslinking agent for the post-curing of the hybrid latex via keto-amine condensation, which occurred during the evaporation of water for film formation. It was revealed that the microphase separation in the hybrid films was suppressed by the post-curing network. The mechanical performance exhibited a high reliability as regards the contents of the crosslinking agents. The reversible exchange of S-S bonds meant that the film displayed associative covalent-adaptive networks in the range of medium temperature in stress relaxation tests, and ≥95% recovery in both the stress and the strain was achieved after the cut-off films were self-healed at 70 °C for 2 h. The rebuilding of the network was also illustrated by the >80% recovery in the elongation at break of the films after three crushing-hot pressing cycles. These findings offer valuable insights, not only endowing the traditional WPUA with self-healing and reprocessing properties, but broadening the field of study of dynamic networks to polymer hybrid latex.

Alloy Engineering Allows On-Demand Design of Ultrasensitive Monolayer Semiconductor SERS Substrates.

The chemical mechanism (CM) of surface-enhanced Raman scattering (SERS) has been recognized as a decent approach to mildly amplify Raman scattering. However, the insufficient charge transfer (CT) between the SERS substrate and molecules always results in unsatisfying Raman enhancement, exerting a substantial restriction for CM-based SERS. In principle, CT is dominated by the coupling between the energy levels of a semiconductor-molecule system and the laser wavelength, whereas precise tuning of the energy levels is intrinsically difficult. Herein, two-dimensional transition-metal dichalcogenide alloys, whose energy levels can be precisely and continuously tuned over a wide range by simply adjusting their compositions, are investigated. The alloys enable on-demand construction of the CT resonance channels to cater to the requirements of a specific target molecule in SERS. The SERS signals are highly reproducible, and a clear view of the SERS dependences on the energy levels is revealed for different CT resonance terms.

VSe2-x O x @Pd Sensor for Operando Self-Monitoring of Palladium-Catalyzed Reactions.

Operando monitoring of catalytic reaction kinetics plays a key role in investigating the reaction pathways and revealing the reaction mechanisms. Surface-enhanced Raman scattering (SERS) has been demonstrated as an innovative tool in tracking molecular dynamics in heterogeneous reactions. However, the SERS performance of most catalytic metals is inadequate. In this work, we propose hybridized VSe2-x O x @Pd sensors to track the molecular dynamics in Pd-catalyzed reactions. Benefiting from metal-support interactions (MSI), the VSe2-x O x @Pd realizes strong charge transfer and enriched density of states near the Fermi level, thereby strongly intensifying the photoinduced charge transfer (PICT) to the adsorbed molecules and consequently enhancing the SERS signals. The excellent SERS performance of the VSe2-x O x @Pd offers the possibility for self-monitoring the Pd-catalyzed reaction. Taking the Suzuki-Miyaura coupling reaction as an example, operando investigations of Pd-catalyzed reactions were demonstrated on the VSe2-x O x @Pd, and the contributions from PICT resonance were illustrated by wavelength-dependent studies. Our work demonstrates the feasibility of improved SERS performance of catalytic metals by modulating the MSI and offers a valid means to investigate the mechanisms of Pd-catalyzed reactions based on VSe2-x O x @Pd sensors.

Epigenetic reactivation of PEG3 by EZH2 inhibitors suppresses renal clear cell carcinoma progress.

PEG3 is a paternally imprinted gene located on chromosome 19q13.4 and one of the most common low-expression genes in human ovarian cancer. PEG3 plays an important role in p53-related cell death. However, whether PEG3 plays a role in renal clear cell carcinoma (ccRCC) remains unclear. Here, we found that PEG3 was epigenetic inactivated and played a tumor suppressor role in ccRCC. Overexpression of PEG3 inhibited ccRCC cell proliferation and colony formation, while removal of PEG3 significantly promoted cell proliferation in vitro and tumor formation in nude mice in vivo. EZH2-mediated H3K27me3 at the PEG3 promoter suppressed PEG3 expression. EZH2 specific inhibitors promote PEG3 transcriptional expression through the transition from H3K27me3 to H3K27ac at the PEG3 promoter region. Depletion of PEG3 inhibited the activation of the p53 signaling pathway, resulting in the resistance of ccRCC to EZH2 inhibitors treatment. Thus, our data show that EZH2-mediated epigenetic inactivation of PEG3 promotes the progress of ccRCC, and reactivation of PEG3 may be a promising strategy for ccRCC.

Flexible plasmonic nanocavities: a universal platform for the identification of molecular orientations.

The molecular orientation provides fundamental images to understand molecular behaviors in chemistry. Herein, we propose and demonstrate sandwich plasmonic nanocavities as a surface-selection ruler to illustrate the molecular orientations by surface-enhanced Raman spectroscopy (SERS). The field vector in the plasmonic nanocavity presents a transverse spinning feature under specific excitations, allowing the facile modulation of the field polarizations to selectively amplify the Raman modes of the target molecules. It does not require the knowledge of the Raman spectrum of a bare molecule as a standard and thus can be extended as a universal ruler for the identification of molecular orientations. We investigated the most widely used Raman probe, Rhodamine 6G (R6G) on the Au surface and tried to clarify the arguments about its orientations from our perspectives. The experimental results suggest concentration-dependent adsorption configurations of R6G: it adsorbs on Au primarily via an ethylamine group with the xanthene ring lying flatly on the metal surface at low concentrations, and the molecular orientation gradually changes from "flat" to "upright" with the increase of molecular concentrations.

VHL-HIF-2α axis-induced SEMA6A upregulation stabilized ß-catenin to drive clear cell renal cell carcinoma progression.

SEMA6A is a multifunctional transmembrane semaphorin protein that participates in various cellular processes, including axon guidance, cell migration, and cancer progression. However, the role of SEMA6A in clear cell renal cell carcinoma (ccRCC) is unclear. Based on high-throughput sequencing data, here we report that SEMA6A is a novel target gene of the VHL-HIF-2α axis and overexpressed in ccRCC. Chromatin immunoprecipitation and reporter assays revealed that HIF-2α directly activated SEMA6A transcription in hypoxic ccRCC cells. Wnt/ß-catenin pathway activation is correlated with the expression of SEMA6A in ccRCC; the latter physically interacted with SEC62 and promoted ccRCC progression through SEC62-dependent ß-catenin stabilization and activation. Depletion of SEMA6A impaired HIF-2α-induced Wnt/ß-catenin pathway activation and led to defective ccRCC cell proliferation both in vitro and in vivo. SEMA6A overexpression promoted the malignant phenotypes of ccRCC, which was reversed by SEC62 depletion. Collectively, this study revealed a potential role for VHL-HIF-2α-SEMA6A-SEC62 axis in the activation of Wnt/ß-catenin pathway. Thus, SEMA6A may act as a potential therapeutic target, especially in VHL-deficient ccRCC.

Flexible two-dimensional MXene-based antennas.

With the growing development of the Internet of things, wearable electronic devices have been extensively applied in civilian and military fields. As an essential component of data transmission in wearable electronics, a flexible antenna is one of the key aspects of research. Conventional metal antennas suffer from a large skin depth, and cannot satisfy the requirements of wearable electronics such as light weight, flexibility, and thinness. Recently, a group of two-dimensional metallic metal carbides (named MXenes) have been explored as building blocks for high-performance flexible antennas with excellent flexibility and superior mechanical strength. The appearance of hydrophilic functional groups at the surface of a MXene allows simple, scalable, and environmentally friendly manufacturing of MXene-based antennas. In this minireview, some pioneering works of MXene-based flexible radio frequency components are summarized, and the existing bottlenecks and the future trends of this promising field are discussed.

Monolayer Iron Oxychloride with a Resonant Band Structure for Ultrasensitive Molecular Sensing.

Two-dimensional layered materials (2DLMs) are expected to be next-generation commercial sensors for surface-enhanced Raman scattering (SERS) sensing owing to their unique structural features and physicochemical properties. The low sensitivity and poor universality of 2DLMs are the dominant barriers toward their practical applications. Herein, we report that monolayer iron oxychloride (FeOCl) with a naturally suitable band structure is a promising candidate for ultrasensitive SERS sensing. The generally boosted Raman scattering cross section of different analyte-FeOCl systems benefits from the resonant photoinduced charge transfer processes and strong ground-state interactions. In addition, the strong adsorption ability of monolayer FeOCl is crucial for rapid detection in practical applications, which is proven to be much better than those of conventional SERS sensors. Consequently, monolayer FeOCl enables diverse SERS applications, including multicomponent analysis, chemical reaction monitoring, and indirect ion sensing.

Two-dimensional MBenes with ordered metal vacancies for surface-enhanced Raman scattering.

As an emerging class of two-dimensional (2D) materials, MBenes show enormous potential for optoelectronic applications. However, their use in molecular sensing as surface-enhanced Raman scattering (SERS)-active material is unknown. Herein, for the first time, we develop a brand-new high-performance MBene SERS platform. Ordered vacancy-triggered highly sensitive SERS platform with outstanding signal uniformity based on a 2D Mo4/3B2 MBene material was designed. The 2D Mo4/3B2 MBene presented superior SERS activity to most of the semiconductor SERS substrates, showing a remarkable Raman enhancement factor of 3.88 × 106 and an ultralow detection limit of 1 × 10-9 M. The underlying SERS mechanism is revealed from systematic experiments and density functional theory calculations that the ultrahigh SERS sensitivity of 2D Mo4/3B2 MBene is derived from the efficient photoinduced charge transfer process between MBene substrates and adsorbed molecules. The abundant electronic density of states near the Fermi level of 2D Mo4/3B2 MBene enables its Raman enhancement by a factor of 100 000 times higher than that of the bulk MoB. Consequently, the 2D Mo4/3B2 MBene could accurately detect various trace chemical analytes. Moreover, with ordered metal vacancies in the 2D Mo4/3B2 MBene, uniform charge transfer sites are formed, resulting in an outstanding signal uniformity with a relative standard deviation down to 6.0%. This work opens up a new horizon for the high-performance SERS platform based on MBene materials, which holds great promise in the field of chemical sensing.

High-specificity molecular sensing on an individual whispering-gallery-mode cavity: coupling-enhanced Raman scattering by photoinduced charge transfer and cavity effects.

Optical whispering-gallery-mode (WGM) cavities have gained considerable interest because of their unique properties of enhanced light-matter interactions. Conventional WGM sensing is based on the mechanisms of mode shift, mode broadening, or mode splitting, which requires a small mode volume and an ultrahigh Q-factor. Besides, WGM sensing suffers from a lack of specificity in identifying substances, and additional chemical functionalization or incorporation of plasmonic materials is required for achieving good specificity. Herein, we propose a new sensing method based on an individual WGM cavity to achieve ultrasensitive and high-specificity molecular sensing, which combines the features of enhanced light-matter interactions on the WGM cavity and the "fingerprint spectrum" of surface-enhanced Raman scattering (SERS). This method identifies the substance by monitoring the Raman signal enhanced by the WGM cavity rather than monitoring the variation of the WGM itself. Therefore, ultrasensitive and high-specificity molecular sensing can be accomplished even on a low-Q cavity. The working principles of the proposed sensing method were also systematically investigated in terms of photoinduced charge transfer, Purcell effect, and optical resonance coupling. This work provides a new WGM sensing approach as well as a strategy for the design of a high-performance SERS substrate by creating an optical resonance mode.

Identification of the deubiquitinase USP28 as a novel molecular therapeutic target of ovarian cancer.

Ubiquitin specific proteinase 28 (USP28) is a member of the deubiquitylating enzymes, which are mainly involved in cell cycle, apoptosis and DNA damage repair. Although USP28 has been found to be upregulated in some tumors, its role in ovarian cancer (OV) remains unclear. Here we show that USP28 was highly expressed in OV samples compared with normal ovarian tissue, and OV patients with higher USP28 levels had a worse prognosis. We found that the abnormal expression of USP28 mRNA in OV was related to the activation of ß-catenin signaling pathway, and USP28 was a transcriptional target gene of the ß-catenin/YAP1/TBX5 complex. In addition, genetic ablation or pharmacological inhibition of USP28 impaired the proliferation ability of OV cells in vitro and in vivo. In conclusion, our findings show that ß-catenin/YAP1/TBX5-mediated aberrant expression of USP28 promotes the malignant phenotype of OV, suggesting that USP28 may be a therapeutic target for OV.

Investigation of the Plasmon-Activated C-C Coupling Reactions by Liquid-State SERS Measurement.

The implementation of plasmonic materials in heterogeneous catalysis was limited due to the lack of experimental access in managing the plasmonic hot carriers. Herein, we propose a liquid-state surface-enhanced Raman scattering (SERS) technique to manipulate and visualize heterogeneous photocatalysis with transparent plasmonic chips. The liquid-state measurement conquers the difficulties that arise from the plasmon-induced thermal effects, and thus the plasmon based strategies can be extended to investigate a wider range of catalytic reactions. We demonstrated the selection of reaction products by modulating the plasmonic hot carriers and explored the mechanisms in several typical C-C coupling reactions with 4-bromothiophenol (4-BTP) as reactants. The real-time experimental results suggest brand new mechanisms of the formation of C-C bonds on plasmonic metal nanoparticles (NPs): the residue of 4-BTP, but not thiophenol (TP), is responsible for the C-C coupling. Furthermore, this technique was extended to study the evolution of the Suzuki-Miyaura reaction on nonplasmonic palladium metals by establishing the charge transfer channels between palladium and Au NPs. The cleavage and formation of chemical bonds in each individual reaction step were discerned, and the corresponding working mechanisms were clarified.

The Multi-Step Chain Extension for Waterborne Polyurethane Binder of Para-Aramid Fabrics.

The comprehensive balance of the mechanical, interfacial, and environmental requirements of waterborne polyurethane (WPU) has proved challenging, but crucial in the specific application as the binder for high-performance polymer fiber composites. In this work, a multi-step chain extension (MCE) method was demonstrated using three kinds of small extenders and one kind of macro-chain extender (CE) for different chain extension steps. One dihydroxyl blocked small molecular urea (1,3-dimethylolurea, DMU) was applied as one of the CEs and, through the hybrid macrodiol/diamine systems of polyether, polyester, and polysiloxane, the WPU was developed by the step-by-step optimization on each chain extending reaction via the characterization on the H-bonding association, microphase separation, and mechanical properties. The best performance was achieved when the ratio of polyether/polyester was controlled at 6:4, while 2% of DMU and 1% of polysiloxane diamine was incorporated in the third and fourth chain extension steps, respectively. Under the condition, the WPU exhibited not only excellent tensile strength of 30 MPa, elongation of break of about 1300%, and hydrophobicity indicated by the water contact angle of 98°, but also effective interfacial adhesion to para-aramid fabrics. The peeling strength of the joint based on the polysiloxane incorporated WPU after four steps of chain extension was 430% higher than that prepared through only two steps of chain extension. Moreover, about 44% of the peeling strength was sustained after the joint had been boiling for 40 min in water, suggesting the potential application for high-performance fabric composites.

Electromagnetic Mechanisms or Chemical Mechanisms? Role of Interfacial Charge Transfer in the Plasmonic Metal/Semiconductor Heterojunction.

The plasmonic metal/semiconductor heterojunction provides a unique paradigm for manipulating light to improve the efficiency of plasmonic materials. Previous studies suggest that the improvement originates from the enhanced carrier exchanges between the plasmonic component of the heterojunction and molecules. This viewpoint, known as the chemical mechanism, is reasonable but insufficient, because the construction of the heterojunction will lead to a charge redistribution in the plasmonic component and cause changes in its physical characteristics. Herein, we will try to clarify that these changes are decisive factors in specific applications by investigating the surface-enhanced Raman scattering (SERS) behavior of a typical Ag/TiO2 heterojunction. We observed significant changes in SERS spectra by modulating the band alignment of the heterojunction in a loop. Identical trends in SERS spectra were observed despite the fact that the charge transfer from the heterojunction to molecules was blocked, suggesting that the major SERS enhancement originates from electromagnetic mechanisms rather than chemical ones.

Flexible Two-Dimensional Vanadium Carbide MXene-Based Membranes with Ultra-Rapid Molecular Enrichment for Surface-Enhanced Raman Scattering.

Two-dimensional (2D) MXene materials have attracted broad interest in surface-enhanced Raman scattering (SERS) applications by virtue of their abundant surface terminations and excellent photoelectric properties. Herein, we propose to design highly sensitive MXene-based SERS membranes by integrating a 2D downsizing strategy with molecular enrichment approaches. Two types of 2D vanadium carbide (V4C3 and V2C) MXenes are demonstrated for ultrasensitive SERS sensing, and corresponding SERS mechanisms including the effect of 2D vanadium carbide thickness on their electron density states and interfacial photoinduced charge transfer resonance were discussed. A 2D downsizing strategy authorizes nonplasmonic SERS detection with a sensitivity of 1 × 10-7 M. Moreover, the performance can be further upgraded by vacuum-assisted filtration, which enables an ultrarapid molecular enrichment (within 2 min), ultrahigh molecular removal rate (over 95%), and improved sensitivity (5 × 10-9 M). This work may shed light on the MXene-based materials as an innovative platform for nonplasmonic SERS detection.