Black Titanium Oxide/Activated TaS2 Flakes Photoelectrode for Plasmon Assisted Hydrogen Evolution at Neutral pH at High Current Density.

A heterojunction photo-electrode(s) consisting of porous black titanium oxide (bTiO2) and electrochemically self-activated TaS2 flakes is proposed and utilized for hydrogen evolution reaction (HER). The self-activated TaS2 flakes provide abundant catalytic sites for HER and the porous bTiO2, prepared by electrochemical anodization and subsequent reduction serves as an efficient light absorber, providing electrons for HER. Additionally, Au nanostructures are introduced between bTiO2 and TaS2 to facilitate the charge transfer and plasmon-triggering ability of the structure created. After structure optimization, high HER catalytic activity at acidic pH and excellent HER activity at neutral pH are achieved at high current densities. In particular, with the utilization of bTiO2@TaS2 photoelectrode (neutral electrolyte, sunlight illumination) current densities of 250 and 500 mA cm-2 are achieved at overpotentials of 433, and 689 mV, respectively, both exceeding the "benchmark" Pt. The addition of gold nanostructures further reduces the overpotential to 360 and 543 mV at 250 and 500 mA cm-2, respectively. The stability of the prepared electrodes is investigated and found to be satisfying within 24 h of performance at high current densities. The proposed system offers an excellent potential alternative to Pt for the development of green hydrogen production on an industrial scale.

Rapid and Universal Synthesis of 2D Transition Metal (Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W) Sulfides through Oxide Sulfurization in CS2 Vapor.

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 CS2 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 (CS2 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.

Plasma-Activated Polydimethylsiloxane Microstructured Pattern with Collagen for Improved Myoblast Cell Guidance.

We focused on polydimethylsiloxane (PDMS) as a substrate for replication, micropatterning, and construction of biologically active surfaces. The novelty of this study is based on the combination of the argon plasma exposure of a micropatterned PDMS scaffold, where the plasma served as a strong tool for subsequent grafting of collagen coatings and their application as cell growth scaffolds, where the standard was significantly exceeded. As part of the scaffold design, templates with a patterned microstructure of different dimensions (50 × 50, 50 × 20, and 30 × 30 µm2) were created by photolithography followed by pattern replication on a PDMS polymer substrate. Subsequently, the prepared microstructured PDMS replicas were coated with a type I collagen layer. The sample preparation was followed by the characterization of material surface properties using various analytical techniques, including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). To evaluate the biocompatibility of the produced samples, we conducted studies on the interactions between selected polymer replicas and micro- and nanostructures and mammalian cells. Specifically, we utilized mouse myoblasts (C2C12), and our results demonstrate that we achieved excellent cell alignment in conjunction with the development of a cytocompatible surface. Consequently, the outcomes of this research contribute to an enhanced comprehension of surface properties and interactions between structured polymers and mammalian cells. The use of periodic microstructures has the potential to advance the creation of novel materials and scaffolds in tissue engineering. These materials exhibit exceptional biocompatibility and possess the capacity to promote cell adhesion and growth.

Mammalian Cell Interaction with Periodic Surface Nanostructures.

Here, we report on the nanopatterning of different aromatic polymer substrates achieved by KrF excimer laser treatment. The conditions for the construction of the laser-induced periodic surface structures, the so-called LIPSS pattern, were established by optimized laser fluence and a number of pulses. The polymer substrates were polyethylene naphthalate (PEN), polyethersulfone (PES), and polystyrene (PS), which were chosen since they are thermally, chemically, and mechanically resistant polymers with high absorption coefficients at the excimer laser wavelength. The surface morphology of the treated substrates was investigated by atomic force microscopy and scanning electron microscopy, and the roughness and effective surface area on the modified samples were determined. Elemental concentration was characterized by energy-dispersive (EDX) analysis, surface chemistry was determined with X-ray photoelectron spectroscopy (XPS). The samples with the formation of LIPSS induced by 10 mJ·cm-2 with 1000, 3000, and 6000 pulses were used for subsequent in vitro cytocompatibility tests using human cells from osteosarcoma (U-2 OS). The LIPSS pattern and its ability of significant cell guidance were confirmed for some of the studied samples. Cell morphology, adhesion, and proliferation were evaluated. The results strongly contribute to the development of novel applications using nanopatterned polymers, e.g., in tissue engineering, cell analysis or in combination with metallization for sensor construction.

Detection of trace amounts of insoluble pharmaceuticals in water by extraction and SERS measurements in a microfluidic flow regime.

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.

Nanostructured Materials for Artificial Tissue Replacements.

This paper review current trends in applications of nanomaterials in tissue engineering. Nanomaterials applicable in this area can be divided into two groups: organic and inorganic. Organic nanomaterials are especially used for the preparation of highly porous scaffolds for cell cultivation and are represented by polymeric nanofibers. Inorganic nanomaterials are implemented as they stand or dispersed in matrices promoting their functional properties while preserving high level of biocompatibility. They are used in various forms (e.g., nano- particles, -tubes and -fibers)-and when forming the composites with organic matrices-are able to enhance many resulting properties (biologic, mechanical, electrical and/or antibacterial). For this reason, this contribution points especially to such type of composite nanomaterials. Basic information on classification, properties and application potential of single nanostructures, as well as complex scaffolds suitable for 3D tissues reconstruction is provided. Examples of practical usage of these structures are demonstrated on cartilage, bone, neural, cardiac and skin tissue regeneration and replacements. Nanomaterials open up new ways of treatments in almost all areas of current tissue regeneration, especially in tissue support or cell proliferation and growth. They significantly promote tissue rebuilding by direct replacement of damaged tissues.

Optomechanical Processing of Silver Colloids: New Generation of Nanoparticle-Polymer Composites with Bactericidal Effect.

The properties of materials at the nanoscale open up new methodologies for engineering prospective materials usable in high-end applications. The preparation of composite materials with a high content of an active component on their surface is one of the current challenges of materials engineering. This concept significantly increases the efficiency of heterogeneous processes moderated by the active component, typically in biological applications, catalysis, or drug delivery. Here we introduce a general approach, based on laser-induced optomechanical processing of silver colloids, for the preparation of polymer surfaces highly enriched with silver nanoparticles (AgNPs). As a result, the AgNPs are firmly immobilized in a thin surface layer without the use of any other chemical mediators. We have shown that our approach is applicable to a broad spectrum of polymer foils, regardless of whether they absorb laser light or not. However, if the laser radiation is absorbed, it is possible to transform smooth surface morphology of the polymer into a roughened one with a higher specific surface area. Analyses of the release of silver from the polymer surface together with antibacterial tests suggested that these materials could be suitable candidates in the fight against nosocomial infections and could inhibit the formation of biofilms with a long-term effect.

Surface Plasmon-Polariton: A Novel Way To Initiate Azide-Alkyne Cycloaddition.

Plasmon catalysis has recently generated tremendous interest in the field of modern chemistry. Application of plasmon introduces the principally new stimulus for the activation of organic reactions, keeping the optical energy concentrated in the vicinity of plasmonic structure, creating an optical near-field enhancement as well as hot electron injection. In this work, for the first time, we presented a new way for the initiation of the azide-alkyne cycloaddition (AAC) using the surface plasmon-polariton wave, supported by the gold grating. With this concept in hand, the plasmon-active gold grating was functionalized with 4-ethynylbenzenediazonium compound. Then, surface-grafted 4-ethynylphenyl groups were plasmon activated and clicked with 4-azidobenzoic acid. Additional experiments allowed to exclude the potential effect of photon, heating, and metal impurities confirmed the key role of surface plasmon-polariton AAC activation. For the investigation of plasmon-induced AAC mechanism, 4-azidophenyl groups (instead of 4-ethynylphenyl groups) were also grafted to the grating surface. Further careful evaluation of reaction kinetics demonstrates that the AAC reaction rate is significantly higher in the case of acetylene activation than in the case of azide activation.

Rapid SERS-based recognition of cell secretome on the folic acid-functionalized gold gratings.

Nowadays, functionalization of the plasmon-supported nanostructured surface is considered as a powerful tool for tumour cell recognition. In this study, the SERS on a surface plasmon polariton-supported gold grating functionalized with folic acid was used to demonstrate an unpretentious recognition of melanoma-associated fibroblasts. Using cultivation media conditioned by different cells, we were able to detect reproducible differences in the secretome of melanoma-associated and normal control fibroblasts. The homogeneous distribution of plasmon energy along the grating surface was proved to provide excellent SERS signal reproducibility, while, to increase the affinity of (bio)molecules to SERS substrate, folic acid molecules were covalently grafted to the gold gratings. As proof of concept, fibroblasts were cultured in vitro, and culture media from the normal and tumour-associated lines were collected and analysed with our proposed SERS substrates. Identifying individual peaks of the Raman spectra as well as comparing their relative intensities, we showed that the proposed functional SERS platform can recognise the melanoma-associated cells without the need for further statistical spectral evaluation directly. We also demonstrated that the SERS chip created provided a stable SERS signal over a period of 90 days without loss of sensitivity. Graphical abstract.

Preparation of Selective and Reproducible SERS Sensors of Hg2+ Ions via a Sunlight-Induced Thiol⁻Yne Reaction on Gold Gratings.

In this contribution, we propose a novel functional surface-enhanced Raman spectroscopy (SERS) platform for the detection of one of the most hazardous heavy metal ions, Hg2+. The design of the proposed sensor is based on the combination of surface plasmon-polariton (SPP) supporting gold grating with the high homogeneity of the response and enhancement and mercaptosuccinic acid (MSA) based specific recognition layer. For the first time, diazonium grafted 4-ethynylphenyl groups have undergone the sunlight-induced thiol-yne reaction with MSA in the presence of Eosine Y. The developed SERS platform provides an extremely sensitive, selective, and convenient analytical procedure to detect mercury ions with limit of detection (LOD) as low as 10-10 M (0.027 µg/L) with excellent selectivity over other metals. The developed SERS sensor is compatible with a portable SERS spectrophotometer and does not require the expensive equipment for statistical methods of analysis.

Ultrasensitive and reproducible SERS platform of coupled Ag grating with multibranched Au nanoparticles.

Surface-enhanced Raman scattering (SERS) spectroscopy is an extremely sensitive analytical technique that is capable of identifying the vibration signatures of target molecules up to single-molecule sensitivity. In this work, the ultrahigh sensitivity of SERS has been achieved through the immobilization of sharp-edges specific nanoparticles - so-called gold multibranched NPs (AuMs) on the silver grating surface through the biphenyl dithiol. This approach allows combining the extremely high SERS enhancement factor (better than that in the case of AuMs immobilized on the flat Ag film) with perfect reproducibility of Raman signals. The grating was created on the polymer substrate using the excimer laser modification and further metal deposition and has an "active" area 5 × 10 mm2, enabling the macroscale SERS substrate preparation. The wet-chemistry synthesized AuMs were then immobilized on the grating surface and the produced structure allows SERS measurements with a portable Raman spectrophotometer. The prepared structures were checked using the AFM, UV-Vis, and Raman spectroscopy techniques.

Antimicrobial Treatment of Polymeric Medical Devices by Silver Nanomaterials and Related Technology.

Antimicrobial biocompatible polymers form a group of highly desirable materials in medicinal technology that exhibit interesting thermal and mechanical properties, and high chemical resistance. There are numerous types of polymers with antimicrobial activity or antimicrobial properties conferred through their proper modification. In this review, we focus on the second type of polymers, especially those whose antimicrobial activity is conferred by nanotechnology. Nanotechnology processing is a developing area that exploits the antibacterial effects of broad-scale compounds, both organic and inorganic, to form value-added medical devices. This work gives an overview of nanostructured antimicrobial agents, especially silver ones, used together with biocompatible polymers as effective antimicrobial composites in healthcare. The bactericidal properties of non-conventional antimicrobial agents are compared with those of conventional ones and the advantages and disadvantages are discussed.

Label-free SERS-ML detection of cocaine trace in human blood plasma.

The widespread consumption of cocaine poses a significant threat to modern society. The most effective way to combat this problem is to control the distribution of cocaine, based on its accurate and sensitive detection. Here, we proposed the detection of cocaine in human blood plasma using a combination of surface enhanced Raman spectroscopy and machine learning (SERS-ML). To demonstrate the efficacy of our proposed approach, cocaine was added into blood plasma at various concentrations and drop-deposited onto a specially prepared disposable SERS substrate. SERS substrates were created by deposition of metal nanoclusters on electrospun polymer nanofibers. Subsequently, SERS spectra were measured and as could be expected, the manual distinguishing of cocaine from the spectra proved unfeasible, as its signal was masked by the background signal from blood plasma molecules. To overcome this issue, a database of SERS spectra of cocaine in blood plasma was collected and used for ML training and validation. After training, the reliability of proposed approach was tested on independently prepared samples, with unknown for SERS-ML cocaine presence or absence. As a result, the possibility of rapid determination of cocaine in blood plasma with a probability above 99.5% for cocaine concentrations up to 10-14 M was confirmed. Therefore, it is evident that the proposed approach has the ability to detect trace amounts of cocaine in bioliquids in an express and simple manner.

Dual-mode electrochemical and SERS detection of PFAS using functional porous substrate.

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 -C6H4-NH2 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.

Surface activation of Hastalex by vacuum argon plasma for cytocompatibility enhancement.

Here, we present surface analysis and biocompatibility evaluation of novel composite material based on graphene oxide traded as Hastalex. First, the surface morphology and elemental analysis of the pristine material were examined by atomic force and scanning electron microscopies, and by energy-dispersive and X-ray photoelectron spectroscopies, respectively. The Hastalex surface was then modified by plasma (3 and 8 W with exposure times up to 240 s), the impact of which on the material surface wettability and morphology was further evaluated. In addition, the material aging was studied at room and elevated temperatures. Significant changes in surface roughness, morphology, and area were detected at the nanometer scale after plasma exposure. An increase in oxygen content due to the plasma exposure was observed both for 3 and 8 W. The plasma treatment had an outstanding effect on the cytocompatibility of Hastalex foil treated at both input powers of 3 and 8 W. The cell number of human MRC-5 fibroblasts on Hastalex foils exposed to plasma increased significantly compared to pristine Hastalex and even to tissue culture polystyrene. The plasma exposure also affected the fibroblasts' cell growth and shape.

Plasmon-Mediated Organic Photoelectrochemistry Applied to Amination Reactions.

Organic electrochemistry is currently experiencing an era of renaissance, which is closely related to the possibility of carrying out organic transformations under mild conditions, with high selectivity, high yields, and without the use of toxic solvents. Combination of organic electrochemistry with alternative approaches, such as photo-chemistry was found to have great potential due to induced synergy effects. In this work, we propose for the first time utilization of plasmon triggering of enhanced and regio-controlled organic chemical transformation performed in photoelectrochemical regime. The advantages of the proposed route is demonstrated in the model amination reaction with formation of C-N bond between pyrazole and substituted benzene derivatives. Amination was performed in photo-electrochemical mode on the surface of plasmon active Au@Pt electrode with attention focused on the impact of plasmon triggering on the reaction efficiency and regio-selectivity. The ability to enhance the reaction rate significantly and to tune products regio-selectivity is demonstrated. We also performed density functional theory calculations to inquire about the reaction mechanism and potentially explain the plasmon contribution to electrochemical reaction rate and regioselectivity.

Polymer-Metal Bilayer with Alkoxy Groups for Antibacterial Improvement.

Many bio-applicable materials, medical devices, and prosthetics combine both polymer and metal components to benefit from their complementary properties. This goal is normally achieved by their mechanical bonding or casting only. Here, we report an alternative easy method for the chemical grafting of a polymer on the surfaces of a metal or metal alloys using alkoxy amine salt as a coupling agent. The surface morphology of the created composites was studied by various microscopy methods, and their surface area and porosity were determined by adsorption/desorption nitrogen isotherms. The surface chemical composition was also examined by various spectroscopy techniques and electrokinetic analysis. The distribution of elements on the surface was determined, and the successful bonding of the metal/alloys on one side with the polymer on the other by alkoxy amine was confirmed. The composites show significantly increased hydrophilicity, reliable chemical stability of the bonding, even interaction with solvent for thirty cycles, and up to 95% less bacterial adhesion for the modified samples in comparison with pristine samples, i.e., characteristics that are promising for their application in the biomedical field, such as for implants, prosthetics, etc. All this uses universal, two-step procedures with minimal use of energy and the possibility of production on a mass scale.

Enantioselective Molecular Detection by Surface Enhanced Raman Scattering at Chiral Gold Helicoids on Grating Surfaces.

Distinct advantages of surface enhanced Raman scattering (SERS) in molecular detection can benefit the enantioselective discrimination of specific molecular configurations. However, many of the recent methods still lack versatility and require customized anchors to chemically interact with the studied analyte. In this work, we propose the utilization of helicoid-shaped chiral gold nanoparticles arranged in an ordered array on a gold grating surface for enantioselective SERS recognition. This arrangement ensured a homogeneous distribution of chiral plasmonic hot spots and facilitated the enhancement of the SERS response of targeted analytes through plasmon coupling between gold helicoid multimers (formed in the grating valleys) and adjacent regions of the gold grating. Naproxen enantiomers (R(+) and S(-)) were employed as model compounds, revealing a clear dependence of their SERS response on the chirality of the gold helicoids. Additionally, propranolol and penicillamine enantiomers were used to validate the universality of the proposed approach. Finally, numerical simulations were conducted to elucidate the roles of intensified local electric field and optical helicity density on the SERS signal intensity and on the chirality of the nanoparticles and enantiomers. Unlike previously reported methods, our approach relies on the excitation of a chiral plasmonic near-field and its interaction with the chiral environment of analyte molecules, obviating the need for the enantioselective entrapment of targeted molecules. Moreover, our method is not limited to specific analyte classes and can be applied to a broad range of chiral molecules.

Surface-Enhanced Raman Spectroscopy and Artificial Neural Networks for Detection of MXene Flakes' Surface Terminations.

The properties of MXene flakes, a new class of two-dimensional materials, are strictly determined by their surface termination. The most common termination groups are oxygen-containing (=O or -OH) and fluorine (-F), and their relative ratio is closely related to flake stability and catalytic activity. The surface termination can vary significantly among MXene flakes depending on the preparation route and is commonly determined after flake preparation by using X-ray photoelectron spectroscopy (XPS). In this paper, as an alternative approach, we propose the combination of surface-enhanced Raman spectroscopy (SERS) and artificial neural networks (ANN) for the precise and reliable determination of MXene flakes' (Ti3C2Tx) surface chemistry. Ti3C2Tx flakes were independently prepared by three scientific groups and subsequently measured using three different Raman spectrometers, employing resonant excitation wavelengths. Manual analysis of the SERS spectra did not enable accurate determination of the flake surface termination. However, the combined SERS-ANN approach allowed us to determine the surface termination with a high accuracy. The reliability of the method was verified by using a series of independently prepared samples. We also paid special attention to how the results of the SERS-ANN method are affected by the flake stability and differences in the conditions of flake preparation and Raman measurements. This way, we have developed a universal technique that is independent of the above-mentioned parameters, providing the results with accuracy similar to XPS, but enhanced in terms of analysis time and simplicity.

Smart multi stimuli-responsive electrospun nanofibers for on-demand drug release.

Here, we report poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAm-co-AAc) microgel-loaded polycaprolactone (PCL) nanofibers as temperature-, pH- and electro-responsive materials. First, the PNIPAm-co-AAc microgels were prepared by precipitation polymerization and then electrospun with PCL. The morphology of the prepared materials, analysed by scanning electron microscopy, showed a narrow nanofiber distribution in the range of 500-800 nm, depending on microgel content. Refractometry measurements, performed at pH4 and 6.5, as well as in distilled water, indicated the thermo- and pH-responsive behaviour of the nanofibers between 31 and 34 °C. After being thoroughly characterized, the prepared nanofibers were loaded with crystal violet (CV) or gentamicin as model drugs. The application of a pulsed voltage led to a pronounced increase in drug release kinetics, which was also dependent on microgel content. In addition, long-term temperature- and pH-responsive release was demonstrated. Next, the prepared materials displayed switchable antibacterial activity against S. aureus and E. coli. Finally, cell compatibility tests showed that NIH 3T3 fibroblasts spread evenly over the nanofiber surface, confirming that the nanofibers serve as a favourable support for cell growth. Overall, the prepared nanofibers offer switchable drug release and appear to have considerable biomedical potential, particularly in wound healing.