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The efficiency of green hydrogen production through photo- or electrochemical splitting of water depends strongly on the catalyst used. Several 2D materials have recently been proposed as effective catalysts or co-catalysts, and among them, oxygen-terminated MXenes deserve significant attention for both electro- and photo-induced water splitting. In this work, we described a hybrid photo-electrochemical approach based on the coupling of Ti3C2Tx MXene flakes on a plasmon-supported Au grating and light triggering of the electrocatalytic activity of the generated hybrid structure in a water splitting half reaction, namely, the hydrogen evolution reaction (HER). In particular, MXene flakes with both fluor and oxygen surface terminations were deposited on a periodic patterned gold surface that was capable of supporting surface plasmon-polariton (SPP) excitation under visible and near-infrared (NIR) light illumination. SPP excitation allows sub-diffraction focusing of light energy and effective enhancement of the electrocatalytic performance of Ti3C2Tx flakes. Under illumination, a significant enhancement of the HER kinetics was observed, as well as tuning of the HER rate-determining step from the Volmer step to the Heyrovsky step. In turn, we observed several-fold enhanced hydrogen evolution, which was attributed to plasmon-assisted hot charge carrier injection, with an additional contribution from the plasmon heating effect. The proposed Au grating/Ti3C2Tx hybrid structure allows utilization of the NIR part of the solar spectrum, which is commonly not used in water photolysis but achieves better efficiency in renewable energy-assisted green hydrogen production. [ABSTRACT FROM AUTHOR]

The future development of human society is closely related to the development of new energy approaches which frequently will be based on green hydrogen. In this regard, one of the key research subjects is the elaboration of new materials for safe and effective hydrogen storage and transportation. In this work, we propose a hybrid hydrogen storage material based on boron nanosheets with surface-immobilized IRMOF-20. Surface immobilization was carried out in two-step procedure using covalent modification of the nanosheets surface and subsequent surface-assisted growth of IRMOF-20 from its mother liquor. Both materials (i. e. boron and IRMOF-20) have previously been reported as effective media for the hydrogen chemical sorption. However, along with a number of advantages, they have specific drawback such as low capacity or insufficient stability at higher pressure. Our main idea was to compensate the drawbacks by materials combination and enhance their effectivity in hydrogen storage. Developed materials combination exhibits high hydrogen gravimetric sorption capacity (significantly superior to boron flakes and even surpassed IRMOF-20 powder), high material stability (even at relatively high pressures) and high selectivity to hydrogen, in comparison with others, "parasitic" gases. [Display omitted] • A hybrid hydrogen storage material based on boron nanosheets with surface-immobilized IRMOF-20 was proposed. • B@IRMOF-20 combination exhibits high hydrogen gravimetric sorption capacity. • B@IRMOF-20 demonstrates relatively high stability at higher pressure. [ABSTRACT FROM AUTHOR]

Human activity is the cause of the continuous and gradual grooving of environmental contaminants, where some released toxic and dangerous compounds cannot be degraded under natural conditions, resulting in a serious safety issue. Among them are the widely occurring water-soluble perfluoroalkyl and polyfluoroalkyl substances (PFAS), sometimes called "forever chemicals" because of the impossibility of their natural degradation. Hence, a reliable, expressive, and simple method should be developed to monitor and eliminate the risks associated with these compounds. In this study, we propose a simple, express, and portable detection method for water-soluble fluoro-alkyl compounds (PFOA and GenX) using mutually complementary methods: electrochemical impedance spectroscopy (EIS) and surface-enhanced Raman spectroscopy (SERS). To implement our method, we developed special substrates based on porous silicon with a top-deposited plasmon-active Au layer by subsequently grafting -C 6 H 4 -NH 2 chemical moieties to provide surface affinity toward negatively charged water-soluble PFAS. Subsequent EIS utilization allows us to perform semiquantitative detection of PFOA and GenX up to 10 -10  M concentration because surface entrapping of PFAS leads to a significant increase in the electrode-electrolyte charge-transfer resistance. However, distinguishing by EIS whether even PFAS were entrapped was impossible, and thus the substrates were subsequently subjected to SERS measurements (allowed by surface plasmon activity due to the presence of a porous Au layer), clearly indicating the appearance of characteristic C-F vibration bands., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Transition metal (TM) sulfides belong to the class of 2D materials with a wide application range. Various methods, including solvothermal, hydrothermal, chemical vapor deposition, and quartz ampoule-based approaches, have been employed for the synthesis of TM sulfides. Some of them face limitations due to the low stability of TM sulfides and their susceptibility to oxidation, and others require more sophisticated equipment or complex and rare precursors or are not scalable. In this work, we propose an alternative approach for the synthesis of 2D TM sulfides by sulfurization of corresponding metal oxides in the vapor of CS 2 at elevated temperature. Subsequent treatment in liquid nitrogen allows exfoliation of created sulfides to a 2D structure. A proposed approach was successfully applied to nine transition metals: Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W. The resulting materials were extensively characterized using various analytical techniques with a focus on their crystalline structure and 2D nature. Our approach offers several advantages including the use of simple precursors (CS 2 and metal oxides), universality (in all cases, the sulfides were obtained), equipment simplicity (tube furnace and quartz reactor), short preparation time (3 h), and the ability of morphology and phase tuning (in particular cases) of the created materials by adjusting the temperature. In addition, gram-scale bulk materials can be obtained in the entry-level laboratories using the proposed approach.

Humidity sensors play a critical role in monitoring human activities, environmental health, food processing and storage, and many other fields. Recently, some 2D materials, particularly MXenes, have been considered as promising candidates for creating humidity sensors because of their high surface area, surface-to-bulk ratio, and excellent conductivity, arising from the high concentration and mobility of free electrons. In this work, we propose the plasmon-assisted surface modification and termination tuning of common MXene (Ti 3 C 2 T x ) to enhance their response to humidity and increase their stability against oxidation. Hydrophobic (-C 6 H 4 -CF 3 ) and hydrophilic (-C 6 H 4 -COOH) chemical moieties were covalently grafted to the Ti 3 C 2 T x surface using plasmon-mediated diazonium chemistry. In situ Grazing-Incidence Wide-Angle X-ray Scattering (GIWAXS) measurements, performed at different humidity levels indicate that surface modification significantly affects penetration of water molecules in Ti 3 C 2 T x films. As a result, the sensitivity of the flakes to the presence of water molecules was significantly altered. Additionally, proposed surface grafting commonly proceeds on the less stable MXene surface sites, where flake oxidation commonly initiates. As a result of the modification, such "weak" and more chemically active sites were blocked and Ti 3 C 2 T x stability was significantly enhanced., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Ammonia is one of the most widely produced chemicals worldwide, which is consumed in the fertilizer industry and is also considered an interesting alternative in energy storage. However, common ammonia production is energy-demanding and leads to high CO 2 emissions. Thus, the development of alternative ammonia production methods based on available raw materials (air, for example) and renewable energy sources is highly demanding. In this work, we demonstrated the utilization of TiB 2 nanostructures sandwiched between coupled plasmonic nanostructures (gold nanoparticles and gold grating) for photoelectrochemical (PEC) nitrogen reduction and selective ammonia production. The utilization of the coupled plasmon structure allows us to reach efficient sunlight capture with a subdiffraction concentration of light energy in the space, where the catalytically active TiB 2 flakes were placed. As a result, PEC experiments performed at -0.2 V (vs. RHE) and simulated sunlight illumination give the 535.2 and 491.3 μg h -1 mg cat -1 ammonia yields, respectively, with the utilization of pure nitrogen and air as a nitrogen source. In addition, a number of control experiments confirm the key role of plasmon coupling in increasing the ammonia yield, the selectivity of ammonia production, and the durability of the proposed system. Finally, we have performed a series of numerical and quantum mechanical calculations to evaluate the plasmonic contribution to the activation of nitrogen on the TiB 2 surface, indicating an increase in the catalytic activity under the plasmon-generated electric field., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Solely light-induced water splitting represents a promising avenue for a carbon-free energy future, based on reliable energy sources. Such processes can be performed using coupled semiconductor materials (the so-called direct Z-scheme design) that facilitate spatial separation of (photo)excited electrons and holes, prevent their recombination, and allow water-splitting half-reactions proceeding at each corresponding semiconductor side. In this work, we proposed and prepared a specific structure, based on WO 3g- x /CdWO 4 /CdS coupled semiconductors, created by annealing of a common WO 3 /CdS direct Z-scheme. WO 3- x /CdWO 4 /CdS flakes were further combined with a plasmon-active grating for the creation of the so-called artificial leaf design, making possible complete utilization of the sunlight spectrum. The proposed structure enables water splitting with high production of stoichiometric amounts of oxygen and hydrogen without undesirable catalyst photodegradation. Several control experiments confirm the creation of electrons and holes participating in the water splitting half-reaction in a spatially selective manner.

Among 2D materials, transition-metal dichalcogenides (TMDCs) of group 5 metals recently have attracted substantial interest due to their superior electrocatalytic activity toward hydrogen evolution reaction (HER). However, a straightforward and efficient synthesis of the TMDCs which can be easily scaled up is missing. Herein, we report an innovative, simple, and scalable method for tantalum disulfide (TaS 2 ) synthesis, involving CS 2 as a sulfurizing agent and Ta 2 O 5 as a metal precursor. The structure of the created TaS 2 flakes was analyzed by Raman, XRD, XPS, SEM, and HRTEM techniques. It was demonstrated that a tuning between 1T (metallic) and 3R (semiconductor) TaS 2 phases can be accomplished by varying the reaction conditions. The created materials were tested for HER, and the electrocatalytic activity of both phases was significantly enhanced by electrochemical self-activation, up to that comparable with the Pt one. The final values of the Tafel slopes of activated TaS 2 were found to be 35 and 43 mV/dec for 3R-TaS 2 and 1T-TaS 2 , respectively, with the corresponding overpotentials of 63 and 109 mV required to reach a current density of 10 mA/cm 2 . We also investigated the mechanism of flake activation, which can be attributed to the changes in the flake morphology and surface chemistry. Our work provides a scalable and simple synthesis method to produce transition-metal sulfides which could replace the platinum catalyst in water splitting technology.

Supercapacitors based on nonresponsive polymer hydrogels are gaining significant attention due to their fabrication simplicity and high potential for wearable electronics. However, the use of smart hydrogels in supercapacitor design remains unexplored. In this work, a smart externally controlled supercapacitor based on a temperature-responsive hydrogel doped with polypyrrole nanotubes (PPyNTs) is proposed. The redistribution of PPyNTs in the poly( N -isopropylacrylamide) (PNIPAm) hydrogel can be reversibly controlled by light illumination or temperature increase, leading to on-demand formation/disruption of the nanotube conductive network, due to release/entrapping of the nanotubes from PNIPAm globule volume on surface. The switchable material was introduced in a supercapacitor design as an active and smart electrode, responsible for external control of charge transport and storage. The created device showed a switchable supercapacitor performance with an ability to significantly and rapidly change capacity under heating/cooling or light illumination. The external trigger was applied for static or dynamic control of supercapacitor behavior: prolongation of discharge time (with constant electric loading) or vice-versa pronounced acceleration of supercapacitor discharge. The proposed smart material-based supercapacitor can find a range of attractive applications in backup energy storage or high power pulse generation.

Detection of trace amounts of poorly water-soluble pharmaceuticals or related (bio)solutions represents a key challenge in environment protection and clinical diagnostics. However, this task is complicated by low concentrations of pharmaceuticals, complex sample matrices, and sophisticated sample preparative routes. In this work, we present an alternative approach on the basis of an on-line flow extraction procedure and SERS measurements performed in a microfluidic regime. The advantages of our approach were demonstrated using ibuprofen (Ibu), which is considered as a common pharmaceutical contaminant in wastewater and should be monitored in various bioliquids. The extraction of Ibu from water to the dichloromethane phase was performed with an optimized microfluidic mixer architecture. As SERS tags, lipophilic functionalized gold multibranched nanoparticles (AuMs) were added to the organic phase. After microfluidic extraction, Ibu was captured by the functionalized AuM surface and recognized by on-line SERS measurements with up to 10-8 M detection limit. The main advantages of the proposed approach can be regarded as its simplicity, lack of need for preliminary sample preparation, high reliability, the absence of sample pretreatment, and low detection limits.

Here, we present a new family of hierarchical porous hybrid materials as an innovative tool for ultrasensitive and selective sensing of enantiomeric drugs in complex biosamples via chiral surface-enhanced Raman spectroscopy (SERS). Hierarchical porous hybrid films were prepared by the combination of mesoporous plasmonic Au films and microporous homochiral metal-organic frameworks (HMOFs). The proposed hierarchical porous substrates enable extremely low limit of detection values (10 -12  M) for pseudoephedrine in undiluted blood plasma due to dual enhancement mechanisms (physical enhancement by the mesoporous Au nanostructures and chemical enhancement by HMOF), chemical recognition by HMOF, and a discriminant function for bio-samples containing large biomolecules, such as blood components. We demonstrate the effect of each component (mesoporous Au and microporous AlaZnCl (HMOF)) on the analytical performance for sensing. The growth of AlaZnCl leads to an increase in the SERS signal (by around 17 times), while the use of mesoporous Au leads to an increase in the signal (by up to 40%). In the presence of a complex biomatrix (blood serum or plasma), the hybrid hierarchical porous substrate provides control over the transport of the molecules inside the pores and prevents blood protein infiltration, provoking competition with existing plasmonic materials at the limit of detection and enantioselectivity in the presence of a multicomponent biomatrix., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Two-dimensional (2D) transition-metal dichalcogenides have become promising candidates for surface-enhanced Raman spectroscopy (SERS), but currently very few examples of detection of relevant molecules are available. Herein, we show the detection of the lipophilic disease marker β-sitosterol on few-layered MoTe 2 films. The chemical vapor deposition (CVD)-grown films are capable of nanomolar detection, exceeding the performance of alternative noble-metal surfaces. We confirm that the enhancement occurs through the chemical enhancement (CE) mechanism via formation of a surface-analyte complex, which leads to an enhancement factor of ≈10 4 , as confirmed by Fourier transform infrared (FTIR), UV-vis, and cyclic voltammetry (CV) analyses and density functional theory (DFT) calculations. Low values of signal deviation over a seven-layered MoTe 2 film confirms the homogeneity and reproducibility of the results in comparison to noble-metal substrate analogues. Furthermore, β-sitosterol detection within cell culture media, a minimal loss of signal over 50 days, and the opportunity for sensor regeneration suggest that MoTe 2 can become a promising new SERS platform for biosensing.

Plasmon-assisted transformations of organic compounds represent a novel opportunity for conversion of light to chemical energy at room temperature. However, the mechanistic insights of interaction between plasmon energy and organic molecules is still under debate. Herein, we proposed a comprehensive study of the plasmon-assisted reaction mechanism using unsymmetric iodonium salts (ISs) as an organic probe. The experimental and theoretical analysis allow us to exclude the possible thermal effect or hot electron transfer. We found that plasmon interaction with unsymmetrical ISs led to the intramolecular excitation of electron followed by the regioselective cleavage of C-I bond with the formation of electron-rich radical species, which cannot be explained by the hot electron excitation or thermal effects. The high regioselectivity is explained by the direct excitation of electron to LUMO with the formation of a dissociative excited state according to quantum-chemical modeling, which provides novel opportunities for the fine control of reactivity using plasmon energy.

The efficient utilization of solar energy is the actual task of the present and near future. Thus, the preparation of appropriate materials that are able to harvest and utilize the broad wavelength range of solar light (especially commonly ignored near-infrared light region-NIR) is the high-priority challenging mission. Our study provides a rationally designed two-dimensional (2D) flexible heterostructures with photocatalytic activity for the production of "clean" hydrogen under NIR illumination, with the hydrogen production rate exceeding most 2D materials and the ability to use the seawater as a starting material. The proposed design utilizes the hybrid bimetallic (Au/Pt) periodic structure, which is further covalently grafted with a metal-organic framework MIL-101(Cr). The periodic gold structure is able to efficiently support the plasmon-polariton wave and to excite the hot electrons, which is further injected in the Pt and MIL-101(Cr) layers. The Pt and MIL-101(Cr) structures provide catalytic sites, which are saturated with hot electrons and efficiently initiate water splitting and hydrogen production. The MIL-101(Cr) layer also serves for repelling generated hydrogen bubbles. The mechanistic studies reveal the catalytic role of every element of the 2D flexible heterostructures. The maximum hydrogen output was achieved under plasmon resonance excitation in the NIR range, and it could be actively controlled by the applied LED wavelength.

The chiral recognition of organic compounds is of vital importance in the field of pharmacology and medicine. Unfortunately, the common analytical routes used in this field are significantly restricted by time spent and equipment demands. In this work, we propose an unprecedented alternative, aimed at enantiomer discrimination and estimation of their concentrations in an uncomplicated and instantaneous manner. The proposed approach is based on the creation of an optical fiber probe with two pronounced plasmonic bands attributed to gold and silver. The gold or silver surfaces were grafted with moieties, able to enunciating entrap chiral amines from solution, resulting in a wavelength shift corresponding to each plasmonic metal. As a model compound of chiral amine, we chose the DOPA, also taking in mind its high medical relevancy. For chiral detection, the optical fiber probe was simply immersed in an analytical solution of DOPA, and the selective shift of gold or silver plasmon bands was observed in the reflected light depending on DOPA chirality. The observed shifts depend on the concentration of DOPA enantiomers. In the case of a racemic mixture, the shifts of both plasmonic bands emerge, making possible the simultaneous determination of enantiomer concentrations and their ratio. The analytical cycle takes several minutes and requires very simple laboratory equipment.

Remote detection of hydrogen, without the utilization of electronic component or elevated temperature, is one of the hot topics in the hydrogen technology and safety. In this work, the design and realization of the optical fiber-based hydrogen sensor with unique characteristics are proposed. The proposed sensor is based on the gold-coated multimode fiber, providing the plasmon properties, decorated by the IRMOF-20 layer with high selectivity and affinity toward hydrogen. The IRMOF-20 layer was grown by a surface-assisted technique, and its formation and properties were studied using X-ray photoelectron spectroscopy, Raman, X-ray diffraction, and Brunauer-Emmett-Teller techniques. Simultaneous ellipsometry results indicate the apparent changes of the refractive index of the IRMOF-20 layer due to hydrogen sorption. As results, the presence of hydrogen led to the pronounced changes of plasmon band wavelength position as well as its intensity increase. The proposed hydrogen sensors were favorably distinguished by a high response/recovery rate, excellent selectivity toward the hydrogen, very low temperature dependency, functionality at room or lower temperature, insensitivity toward the humidity, and the presence of CO 2 , CO, or NO 2 . Additionally, the proposed hydrogen sensor showed good reversibility, reproducibility, and long-term stability.