Universal Substrate Research Articles

Ti3C2T x MXene as surface-enhanced Raman scattering substrate

The electromagnetic field enhancement mechanisms leading to surface-enhanced Raman scattering (SERS) of R6G molecules near Ti3C2T x MXene flakes of different shapes and sizes are analyzed theoretically in this paper. In COMSOL simulations for the enhancement factor (EF) of SERS, the dye molecule is modeled as a small sphere with polarizability spectrum based on experimental data. It is demonstrated, for the first time, that in the wavelength range of 500 nm – 1000 nm , the enhancement of Raman signals is largely conditioned by quadrupole surface plasmon (QSP) oscillations that induce a strong polarization of the MXene substrate. We show that the vis-NIR spectral range quadrupole SP resonances are strengthened due to interband transitions (IBTs), which provide EF values of the order of 105–107 in agreement with experimental data. The weak sensitivity of the EF to the shape and size of MXene nanoparticles (NPs) is interpreted as a consequence of the low dependence of the absorption cross-section of QSP oscillations and IBT on the geometry of the flakes. This reveals a new feature: the independence of EF on the geometry of MXene substrates, which allows to avoid the monitoring of the shape and size of flakes during their synthesis. Thus, MXene flakes can be advantageous for the easy manufacturing of universal substrates for SERS applications. The electromagnetic SERS enhancement is determined by the ‘lightning rod’ and ‘hot-spot’ effects due to the partial overlapping of the absorption spectrum of the R6G molecule with these MXene resonances.

Synthesis of multilayered h-BN film on the molten Ni–B and the influence of underneath W substrate

High-quality two-dimensional hexagonal boron nitride (h-BN) film with tens of layers has been used as a universal substrate and capping layer for the van der Waals devices. Various approaches have been carried out for the synthesis of multilayered h-BN. Among them, the metal flux method is reliable in yielding h-BN crystals with high crystalline quality. However, this time- and energy-demanding method hinders its scale application. Herein, inspired by the metal flux method, we reported the time-effective growth of high-quality multilayered h-BN film (ca. 20 nm) on a molten Ni–B layer wetting on W substrate with chemical vapor deposition method. The film exhibits an excellent stacking sequence and a full-width at half maximum of the Raman E2g peak narrow to 9.5 cm−1. Cross-sectional high-resolution transmission electron microscopy and in-situ x-ray diffraction spectroscopy were carried out to investigate the crystal structure evolution of Ni–B layer wetting on W substrate. It is found that the low surface tension caused by the spreading of Ni–B alloy on the W substrate and the presence of the Ni subsurface may be responsible for the formation of multilayered h-BN with excellent crystalline quality. Meanwhile, the W diffusion in Ni–B-based melt can hinder the formation of h-BN under certain growth conditions. The approach demonstrates the feasibility of large-scale growth of multilayered h-BN, paving the way to future applications in van der Waals electronic and optoelectronic devices.

Synthesis of N-Phenylcarbamate by C–N Coupling Reaction without Metal Participation

AbstractWe have developed a new method for the synthesis of carbamates from amine and hydrazine formate. The reaction occurs in the presence of iodine and tert-butyl hydroperoxide, in which carbazates are produced via alkoxycarbonyl radical formation for cross-coupling reaction. The method exhibits broad functional group tolerance and affords a series of N-phenylcarbamates in moderate to good yields. Remarkably, our approach is metal free and utilizes cheap, readily available raw materials and relatively universal substrates.

Molecular Thin Films Enable the Synthesis and Screening of Nanoparticle Megalibraries Containing Millions of Catalysts.

Megalibraries are centimeter-scale chips containing millions of materials synthesized in parallel using scanning probe lithography. As such, they stand to accelerate how materials are discovered for applications spanning catalysis, optics, and more. However, a long-standing challenge is the availability of substrates compatible with megalibrary synthesis, which limits the structural and functional design space that can be explored. To address this challenge, thermally removable polystyrene films were developed as universal substrate coatings that decouple lithography-enabled nanoparticle synthesis from the underlying substrate chemistry, thus providing consistent lithography parameters on diverse substrates. Multi-spray inking of the scanning probe arrays with polymer solutions containing metal salts allows patterning of >56 million nanoreactors designed to vary in composition and size. These are subsequently converted to inorganic nanoparticles via reductive thermal annealing, which also removes the polystyrene to deposit the megalibrary. Megalibraries with mono-, bi-, and trimetallic materials were synthesized, and nanoparticle size was controlled between 5 and 35 nm by modulating the lithography speed. Importantly, the polystyrene coating can be used on conventional substrates like Si/SiOx, as well as substrates typically more difficult to pattern on, such as glassy carbon, diamond, TiO2, BN, W, or SiC. Finally, high-throughput materials discovery is performed in the context of photocatalytic degradation of organic pollutants using Au-Pd-Cu nanoparticle megalibraries on TiO2 substrates with 2,250,000 unique composition/size combinations. The megalibrary was screened within 1 h by developing fluorescent thin-film coatings on top of the megalibrary as proxies for catalytic turnover, revealing Au0.53Pd0.38Cu0.09-TiO2 as the most active photocatalyst composition.

Investigating the role of Candida albicans as a universal substrate for oral bacteria using a transcriptomic approach: implications for interkingdom biofilm control?

Candida albicans is frequently identified as a colonizer of the oral cavity in health and has recently been termed a "keystone" commensal due to its role on the bacterial communities. However, the role that C. albicans plays in such interactions is not fully understood. Therefore, this study aimed to identify the relationship between C. albicans and bacteria associated with oral symbiosis and dysbiosis. To do this, we evaluated the ability of C. albicans to support the growth of the aerobic commensal Streptococcus gordonii and the anaerobic pathogens Fusobacterium nucleatum and Porphyromonas gingivalis in the biofilm environment. RNA-Sequencing with the Illumina platform was then utilized to identify C. albicans gene expression and functional pathways involved during such interactions in dual-species and a 4-species biofilm model. Results indicated that C. albicans was capable of supporting growth of all three bacteria, with a significant increase in colony counts of each bacteria in the dual-species biofilm (p < 0.05). We identified specific functional enrichment of pathways in our 4-species community as well as transcriptional profiles unique to the F. nucleatum and S. gordonii dual-species biofilms, indicating a species-specific effect on C. albicans. Candida-related hemin acquisition and heat shock protein mediated processes were unique to the organism following co-culture with anaerobic and aerobic bacteria, respectively, suggestive that such pathways may be feasible options for therapeutic targeting to interfere with these fungal-bacterial interactions. Targeted antifungal therapy may be considered as an option for biofilm destabilization and treatment of complex communities. Moving forward, we propose that further studies must continue to investigate the role of this fungal organism in the context of the interkingdom nature of oral diseases.

Cation Vacancy Clusters in Ti3C2Tx MXene Induce Ultra‐Strong Interaction with Noble Metal Clusters for Efficient Electrocatalytic Hydrogen Evolution

AbstractMXenes are promising substrates for supported noble metal electrocatalysts. Yet, it is a significant challenge to modulate the metal–support interaction (MSI) for enhancing catalytic performance. Herein, employing a facile HF etching method, the cation vacancy structures in Ti3C2Tx MXenes are controllably tuned, producing nearly vacancy‐free (Ti3C2Tx‐V0), single Ti atom vacancy (Ti3C2Tx‐VS), or Ti vacancy cluster (Ti3C2Tx‐VC) engineered MXenes. Ruthenium atomic clusters, as a model catalyst, successfully anchor on all MXene substrates. Different from the terminal O/F coordination groups on routine Ti3C2Tx MXene surfaces, the Ti vacancy clusters in Ti3C2Tx‐VC create unique lattice carbon ligand environment toward Ru species, which induces ultra‐strong MSI. As a result, compared to Ti3C2Tx‐V0 and Ti3C2Tx‐VS, the Ti3C2Tx‐VC modulated Ru clusters (Ru@Ti3C2Tx‐VC) exhibit the optimized balance of H2O adsorption/dissociation and OH/H desorption, thereby delivering superior electrocatalytic performance in the alkaline hydrogen evolution reaction (HER). Within the wide range from laboratory‐level (90 mA cm−2) to industrial‐level (1.5 A cm−2) current density, Ru@Ti3C2Tx‐VC outperforms commercial Pt/C in terms of overpotential and mass activity. Moreover, as a universal substrate for noble metal catalysts, Ti3C2Tx‐VC can also anchor Ir/Pt/Rh atomic clusters and enable excellent HER catalytic activity. This work expands the scope of the MSI between MXene and noble metal catalysts.

PH and non-enzymatic glucose response at ultra-low concentration using submicrochannel heterogeneous membrane

The construction of solid nanochannel-based biosensor with submicron pore size has great significance to the analysis of biomolecule with high sensitivity and low detection limit. In this paper, a submicrochannel heterogeneous membrane with asymmetric geometry is prepared as the base by combining thermo-crosslinked hydrophobic conducting polymer and porous anodic aluminium oxide channel (AAO) with submicron pore size (269 nm). After the polydopamine-Au multilayer assembly, a large number of Au nanoparticles with adjustable size (∼10 and 89 nm) and density are in situ generated and fixed on the inner wall of AAO. Then 4-mercapto phenylboric acid with high density is grafted through Au-S bond to construct the submicrochannel heterogeneous membrane with the characteristic of ion current rectification in response to pH and saccharide. Benefit from the blocking effect of hydrophobic conducting polymer and the multilayer assembly of polydopamine-Au, the current of background response by the membrane device is effectively reduced, the ion current rectification strength can be effectively regulated in the range of pH 3–9, and the response to ultra-low glucose concentration without enzyme is achieved in the linear range of 1 pM-0.1 μM. A universal substrate platform is provided for the construction of solid nanochannel-based biosensor with submicron pore size.

Schiff-Base Chemistry-Coupled Catechol Oxidase-Like Nanozyme Reaction as a Universal Sensing Mode for Ultrasensitive Biosensing.

Expanding sensing modes and improving catalytic performance of nanozyme-based analytical chemistry are beneficial to realizing the desired biosensing of analytes. Herein, Schiff-base chemistry coupled with a novel catechol oxidase-like nanozyme (CHzyme) is designed and constructed, exhibiting two main advantages, including (1) improving catalytic performance by nearly 2-fold compared with only the oxidase-like role of CHzyme; (2) increasing the designability of the output signal by signal transduction of cascade reaction. Thereafter, the substrate sensing modes based on a cascade reaction between the CHzyme-catalyzed reaction and Schiff-base chemistry are proposed and comprehensively studied, containing catalytic substrate sensing mode, competitive substrate sensing mode, and generated substrate sensing mode, expecting to be employed in environmental monitoring, food analyses, and clinical diagnoses, respectively. More meaningfully, the generated substrate sensing mode is successfully applied to construct a cascade reaction coupling ratiometric fluorescent immunoassay for the detection of clenbuterol, increasing 15-fold in detection sensitivity compared with the traditional enzyme-linked immunosorbent assay. It is expected that the expanded universal substrate sensing modes and the Schiff-base chemistry-enhanced nanozyme can enlighten the exploration of innovative biosensors.

Thiolate DNAzymes on Gold Nanoparticles for Isothermal Amplification and Detection of Mesothelioma-derived Exosomal PD-L1 mRNA.

Catalytic DNAzymes have been used for isothermal amplification and rapid detection of nucleic acids, holding the potential for point-of-care testing applications. However, when Subzymes (universal substrate and DNAzyme) are tethered to the polystyrene magnetic microparticles via biotin-streptavidin bonds, the residual free Subzymes are often detached from the microparticle surface, which causes a significant degree of false positives. Here, we attached dithiol-modified Subzyme to gold nanoparticle and improved the limit of detection (LoD) by 200 times compared to that using magnetic microparticles. As a proof of concept, we applied our new method for the detection of exosomal programed cell-death ligand 1 (PD-L1) RNA. As the classical immune checkpoint, molecule PD-L1, found in small extracellular vesicles (sEVs, traditionally called exosomes), can reflect the antitumor immune response for predicting immunotherapy response. We achieved the LoD as low as 50 fM in detecting both the RNA homologous to the PD-L1 gene and exosomal PD-L1 RNAs extracted from epithelioid and nonepithelioid subtypes of mesothelioma cell lines, which only takes 8 min of reaction time. As the first application of isothermal DNAzymes for detecting exosomal PD-L1 RNA, this work suggests new point-of-care testing potentials toward clinical translations.

New Aspects of the Reaction of Thioacetamide and N-Substituted Maleimides.

N-Arylmaleimides are universal substrates for the synthesis of various heterocyclic compounds with a wide spectrum of biological activity. However, their reactions with thioacetamides have not been comprehensively studied. We studied the reactions of thioacetamide with N-arylmaleimides under various conditions. We established for the first time that three types of products: epithiopyrrolo[3,4-c]pyridines, pyrrolo[3,4-c]pyridines and 3,3'-thiobis(1-arylpyrrolidine-2,5-diones) can be obtained in different conditions. In all cases, two maleimide molecules are involved in the reaction. 3,3'-Thiobis(1-arylpyrrolidine-2,5-diones) are the major products when the reaction is conducted at boiling in acetic acid. When thioacetamide and N-arylmaleimide are kept in dioxane at 50 °C, epithiopyrrolo[3,4-c]pyridines can be isolated, which, when heated in dioxane, in acetic acid or in methanol in the presence of catalytic amounts of sodium methoxide, are converted into pyrrolo[3,4-c]pyridines by eliminating hydrogen sulfide. The reaction of thioacetamide and N-arylmaleimide in dioxane at boiling temperature with the portioned addition of N-arylmaleimide leads predominantly to the formation of pyrrolo[3,4-c]pyridines. The reaction of thioacetamide with N-alkylmaleimides under all the above conditions leads predominantly to the formation of the corresponding sulfides. The structure of the compounds obtained was characterized by a set of spectral analysis methods and X-ray diffraction (XRD) data.

SERS-CNN approach for non-invasive and non-destructive monitoring of stem cell growth on a universal substrate through an analysis of the cultivation medium

The development of advanced methods of SERS-CNN data analysis seems to provide a perfect analytical system that is capable of solving the sophisticated task of determining the species and the behavior of microorganisms. Unlike the widely-used analytical approach, machine learning allows precise analysis even of very complex spectra of biological samples, and can provide precise decisions for a specific biochemical or microbiological task. In this article, we show for the first time the utilization of the SERS–CNN approach for remote observation of mesenchymal stem cell behavior. Our approach is based on SERS measurements of the biochemical changes taking place in the surrounding culture media due to stem cell proliferation and their biochemical activity. The cells were cultivated on various substrates supporting random or oriented cell growth, and also on “surface-toxic” substrates. SERS-CNN analysis reveals the ability to perform “remote” non-invasive estimation (i.e. using the surrounding medium analysis) of the degree of cell survival and the proliferation rate, using Raman measurements and advanced spectra data processing. It should be noted that the proposed approach makes it possible to analyze cell behavior without disrupting cell growth, and it can also be performed by untrained staff with the use of widely-available equipment.

A universal substrate for the nanoscale investigation of two-dimensional materials

Since discovering two-dimensional materials, there has been a great interest in exploring, understanding, and taking advantage of their unique properties. Si/SiO2 is one of the most used substrates for the deposition and characterization of 2D materials due to its availability and optical contrast. This work goes beyond the conventional substrate and introduces highly-ordered pyrolytic graphite (HOPG) as universal support for investigating two-dimensional materials due to several unique properties such as chemical and temperature stability, intrinsic high flatness, reusability, electrical conductivity, ease of use, availability, and enhanced adhesion of two-dimensional materials. We demonstrate this by analyzing several 2D materials with advanced atomic force microscopy methods, Raman and photoluminescence spectroscopy with hyperspectral imaging, and scanning electron microscopy with elementary analysis imaging. The strong adhesion to HOPG allowed the instant deposition of different two-dimensional materials GaSe, MoS2, Zn2In2S5, talc, and h-BN. This feat is hard to accomplish on the conventional SiO2 substrate without polymer-assisted transfer. Moreover, this strong interaction can strain 2D materials deposited on HOPG, giving localized changes in reactivity, optical, and electronic properties. This effect is explored for selective Ag deposition on strained regions of 2D materials to activate photocatalytic reactions.

Aging astrocytes metabolically support aging axon function by proficiently regulating astrocyte-neuron lactate shuttle

The astrocyte-neuron lactate shuttle (ANLS) is an essential metabolic support system that uptakes glucose, stores it as glycogen in astrocytes, and provides glycogen-derived lactate for axonal function. Aging intrinsically increases the vulnerability of white matter (WM) to injury. Therefore, we investigated the regulation of this shuttle to understand vascular-glial metabolic coupling to support axonal function during aging in two different WM tracts. Aging astrocytes displayed larger cell bodies and thicker horizontal processes in contrast to thinner vertically oriented processes of young astrocytes. Aging axons recovered less following aglycemia in mouse optic nerves (MONs) compared to young axons, although providing lactate during aglycemia equally supported young and aging axonal function. Incubating MONs in high glucose to upregulate glycogen stores in astrocytes delayed loss of function during aglycemia and improved recovery in both young and aging axons. Providing lactate during recovery from aglycemia unmasked a metabolic switch from glucose to lactate in aging axons. Young and aging corpus callosum consisting of a mixture of myelinated and unmyelinated axons sustained their function fully when lactate was available during aglycemia and surprisingly showed a greater resilience to aglycemia compared to fully myelinated axons of optic nerve. We conclude that lactate is a universal substrate for axons independent of their myelination content and age.

Virus‐Like Iron Oxide Minerals Inspired by Magnetotactic Bacteria: Towards an Outstanding Photothermal Superhydrophobic Platform on Universal Substrates

AbstractMagnetic iron oxides, as the typical photothermal materials, possess the advantages of low cost, easy preparation, and biocompatibility, which impart great expectations in broad application prospects. However, the limited photothermal efficiency of iron oxides restricts their further use. Inspired by magnetotactic bacteria, a liquid film‐confined strategy has been developed assisted by a magnetic field for mineralization and assembly of iron oxides on the surface at room temperature. Virus‐like hierarchically micro/nanostructured iron oxides can be obtained on universal substrates which exhibit excellent photothermal performance, the highest among all iron oxide coatings and even comparable with carbon‐based materials. Theoretical simulation demonstrates the promotion of light capture by these particular structures. Moreover, by virtue of this, the surface is endowed with superhydrophobicity by a simple modification to construct a photothermal superhydrophobic platform, which is demonstrated by two challenging scenarios: high‐efficient antibacterial activity and defrosting/deicing ability controlled remotely. There is no need for harsh experimental conditions and templates, the strategy reported here is mild, environmental‐friendly and adopts trace amount of liquid (55 µL cm−2), which can provide a reference for the fabrication and application of other photothermal materials.

Left and Right Arcuate Fasciculi Are Uniquely Related to Word Reading Skills in Chinese-English Bilingual Children.

Whether reading in different writing systems recruits language-unique or language-universal neural processes is a long-standing debate. Many studies have shown the left arcuate fasciculus (AF) to be involved in phonological and reading processes. In contrast, little is known about the role of the right AF in reading, but some have suggested that it may play a role in visual spatial aspects of reading or the prosodic components of language. The right AF may be more important for reading in Chinese due to its logographic and tonal properties, but this hypothesis has yet to be tested. We recruited a group of Chinese-English bilingual children (8.2 to 12.0 years old) to explore the common and unique relation of reading skill in English and Chinese to fractional anisotropy (FA) in the bilateral AF. We found that both English and Chinese reading skills were positively correlated with FA in the rostral part of the left AF-direct segment. Additionally, English reading skill was positively correlated with FA in the caudal part of the left AF-direct segment, which was also positively correlated with phonological awareness. In contrast, Chinese reading skill was positively correlated with FA in certain segments of the right AF, which was positively correlated with visual spatial ability, but not tone discrimination ability. Our results suggest that there are language universal substrates of reading across languages, but that certain left AF nodes support phonological mechanisms important for reading in English, whereas certain right AF nodes support visual spatial mechanisms important for reading in Chinese.

On‐Demand, Direct Printing of Nanodiamonds at the Quantum Level (Adv. Sci. 5/2022)

Nanodiamonds Diamond nanocrystals, namely nanodiamonds, hosting point defects such as nitrogen-vacancy (NV) centers have been emerging as one of the most promising quantum materials. In article number 2103598, Ji Tae Kim, Zhiqin Chu, and co-workers develop a direct printing method for nanodiamonds containing NV centers at the quantum level. The method developed here provides a high-precision, lithography-free route to place diamond defects directly on the universal substrate towards their further developments in many exciting quantum research areas and beyond.

A Universal Substrate for the Nanoscale Investigation of Two-Dimensional Materials

A Universal Substrate for the Nanoscale Investigation of Two-Dimensional Materials

On-Demand, Direct Printing of Nanodiamonds at the Quantum Level.

The quantum defects in nanodiamonds, such as nitrogen‐vacancy (NV) centers, are emerging as a promising candidate for nanoscale sensing and imaging, and the controlled placement with respect to target locations is vital to their practical applications. Unfortunately, this prerequisite continues to suffer from coarse positioning accuracy, low throughput, and process complexity. Here, it is reported on direct, on‐demand electrohydrodynamic printing of nanodiamonds containing NV centers with high precision control over quantity and position. After thorough characterizations of the printing conditions, it is shown that the number of printed nanodiamonds can be controlled at will, attaining the single‐particle level precision. This printing approach, therefore, enables positioning NV center arrays with a controlled number directly on the universal substrate without any lithographic process. The approach is expected to pave the way toward new horizons not only for experimental quantum physics but also for the practical implementation of such quantum systems.

Bioinspired Integration of Naturally Occurring Molecules towards Universal and Smart Antibacterial Coatings

AbstractSurface‐independent smart antibacterial coatings with on‐demand antibiotics release profiles have attracted increasing attention in medical instruments, antibiotics delivery platforms, and implanted devices. Although several approaches have been well documented, the facile preparation of antibacterial coatings onto universal substrates with high antibiotics loading efficiencies, tunable drug release profiles, and excellent antibacterial performances is still met with many challenges, especially related to the redundant coating material synthesis and selective substrate fabrication process. To resolve this issue, the authors report a facile and robust fabrication method towards smart antibacterial coating surfaces on various substrates via a one‐pot integration of two types of naturally occurring building blocks, aminoglycosides and protocatechualdehyde in the presence of plant enzyme horseradish peroxidase. The simultaneous dynamic imine bonds formation and enzymatic polymerization within the system during the one‐pot reaction enable the facile fabrication of diverse surface‐independent smart antibacterial coatings, which can demonstrate several promising features including high drug loading and dynamic (i.e., pH‐responsive) properties, tunable and on‐demand antibiotics release behaviors, and efficient antibacterial activities both in vitro and in vivo. This work may offer new opportunities towards the robust and universal antibacterial coating materials by the bioinspired integration of all natural building blocks.

Polymer thin films as universal substrates for extreme ultraviolet absorption spectroscopy of molecular transition metal complexes.

Polystyrene and polyvinyl chloride thin films are explored as sample supports for extreme ultraviolet (XUV) spectroscopy of molecular transition metal complexes. Thin polymer films prepared by slip-coating are flat and smooth, and transmit much more XUV light than silicon nitride windows. Analytes can be directly cast onto the polymer surface or co-deposited within it. The M-edge XANES spectra (40-90 eV) of eight archetypal transition metal complexes (M = Mn, Fe, Co, Ni) are presented to demonstrate the versatility of this method. The films are suitable for pump/probe transient absorption spectroscopy, as shown by the excited-state spectra of Fe(bpy)32+ in two different polymer supports.