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Surface-enhanced Raman spectroscopy (SERS) is a potent technique for analyzing and detecting various targets, including toxic ions, pesticides, and biomarkers, at the single-molecule level. The efficiency of SERS techniques relies heavily on the underlying SERS substrate, which is primarily responsible for the strong induction of localized plasmon resonance on nanostructures. Noble metals such as gold and silver were commonly used to fabricate SERS substrates, leveraging the electromagnetic mechanism (EM) to enhance the Raman signal. However, chemically synthesized nanoparticle-based SERS substrates suffer from low uniformity and reproducibility. Furthermore, the high cost associated with noble metals makes most SERS substrates expensive to produce. In this study, we present a straightforward method for fabricating a highly uniform and reproducible SERS substrate using a femtosecond laser-based 3D printer. Notably, our method offers good cost competitiveness since it requires only a minimal amount of gold coating for the SERS signal. Moreover, the proposed method exhibits exceptional versatility in SERS analysis and detection, catering to numerous targets in the field.

Spiders synthesize their web using a liquid bridge-to-solidification mechanism at the end of their glands. Inspired by this process, in this work, we fabricated micro-glue threads (μGTs, polymer microwires) by a simple "pinch and spread" process using just two fingertips. The μGTs exhibited excellent tensile strength (∼50 GPa), comparable to those of spider silk and biological fibers. The chemical, physical, and mechanical properties of the μGTs were investigated, and it was confirmed that the thickness of the μGTs could be controlled by ethanol treatment in varying concentrations. Moreover, electrically conductive μGTs were easily fabricated by simply mixing them with various nanomaterials such as gold nanoparticles, zinc oxide nanowires, and reduced graphene oxide (rGO). Interestingly, the conductive μGTs, fabricated using rGO, exhibited remarkable electrical conductivity (0.45 μS) compared to those fabricated using other materials. The conductive μGTs are applicable not only to NO2 gas sensing but also as electrical fuselike materials that melt when the humidity increases. Collectively, the results present μGTs as cost-effective, simple, and versatile materials, which enables their application in a variety of sensors.

Heavy metal ions are toxic to humans and can further interact with amyloid in the human body to produce amyloid plaques, which disrupt neurotransmitter function and are linked to Alzheimer's and Parkinson's diseases. In this study, we developed an amyloid oligomer-reduced graphene oxide composite (AOrGOC) electrochemical sensor for effective heavy metal ion detection based on square-wave anodic stripping voltammetry. The reactivity between amyloids and heavy metal ions was studied by analyzing the stripping current for different amyloids (lysozyme, bovine serum albumin, and β-lactoglobulin) and amyloid growth types (monomers, oligomers, and fibrils). Reduced graphene oxide was used to improve the sensitivity of the sensor. The AOrGOC sensor exhibited the detection limits of 86.0 and 9.5 nM for Cd

We propose a method of improving the thermoelectric properties of graphene using defect engineering through plasma irradiation and atomic layer deposition (ALD). We intentionally created atomic blemishes in graphene by oxygen plasma treatment and subsequently healed the atomistically defective places using Pt-ALD. After healing, the thermal conductivity of the initially defective graphene increased slightly, while the electrical conductivity and the square of the Seebeck coefficient increased pronouncedly. The thermoelectric figure of merit of the Pt-ALD treated graphene was measured to be over 4.8 times higher than the values reported in the literature. We expect that our study could provide a useful guideline for the development of graphene-based thermoelectric devices.

Vitamin D has been identified as an essential biomarker for various diseases such as rheumatoid arthritis, cancer, and cardiovascular diseases. Recently, many reports have demonstrated a potential link between vitamin D and systemic infections, including coronavirus disease 2019. The villi of the small intestine increase the surface area of the intestinal walls, demonstrating exceptionally efficient absorption of nutrients in the lumen and adding digestive secretions. In this study, based on the villi structure, we developed a bio-inspired silver nanovilli-based sandwich-type surface enhanced Raman scattering aptasensor for the ultrasensitive and selective detection of 25-hydroxy vitamin D

Vitamin D is associated with various diseases such as obesity, digestive problems, osteoporosis, depression, and infections, which has emerged as an interest in public healthcare. Recently, vitamin D has received more attention because of the potential implication with coronavirus disease 2019. In this study, we developed a localized surface plasmon resonance (LSPR) aptasensor based on polyethylene-glycol(PEG)-free gold nanorods (AuNRs) for the wide-range and direct detection of 25-hydroxyvitamin D

Thermal interface materials (TIMs), typically composed of a polymer matrix with good wetting properties and thermally conductive fillers, are applied to the interfaces of mating components to reduce the interfacial thermal resistance. As a filler material, silver has been extensively studied because of its high intrinsic thermal conductivity. However, the high cost of silver and its toxicity has hindered the wide application of silver-based TIMs. Copper is an earth-abundant element and essential micronutrient for humans. In this paper, we present a copper-based multi-dimensional filler composed of three-dimensional microscale copper flakes, one-dimensional multi-walled carbon nanotubes (MWCNTs), and zero-dimensional copper nanoparticles (Cu NPs) to create a safe and low-cost TIM with a high thermal conductivity. Cu NPs synthesized by microwave irradiation of a precursor solution were bound to MWCNTs and mixed with copper flakes and polyimide matrix to obtain a TIM paste, which was stable even in a high-temperature environment. The cross-plane thermal conductivity of the copper-based TIM was 36 W/m/K. Owing to its high thermal conductivity and low cost, the copper-based TIM could be an industrially useful heat-dissipating material in the future.

Various atomistic defects ever-present in graphene have triggered unwanted phonon scattering, thereby significantly deteriorating the heat transport property of the graphene. Consequently, continuous endeavors have been made to minimize these atomistic defects. Here, we first experimentally show that defect healing based on atomic layer deposition (ALD) can significantly mitigate the degradation in the thermal conductivity of the graphene. After defect healing with Pt and Al2O3 ALD, the thermal conductivities of graphene synthesized by conventional chemical vapor deposition were improved by ∼83% and ∼64%, respectively. It is speculated that the healing atoms facilitate heat transfer across the defects, by eliminating the influence of vacancy in the graphene layer, which likely increases the phonon lifetime (leading to a noticeable improvement in thermal conductivity). This study provides an understanding of how defect engineering could affect phonon transport in 2D materials and sheds light on affordable graphene with excellent thermal conductivity.

Vitamin D has been identified as an essential biomarker for various diseases such as rheumatoid arthritis, cancer, and cardiovascular diseases. Recently, many reports have demonstrated a potential link between vitamin D and systemic infections, including coronavirus disease 2019. The villi of the small intestine increase the surface area of the intestinal walls, demonstrating exceptionally efficient absorption of nutrients in the lumen and adding digestive secretions. In this study, based on the villi structure, we developed a bio-inspired silver nanovilli-based sandwich-type surface enhanced Raman scattering aptasensor for the ultrasensitive and selective detection of 25-hydroxy vitamin D3. The densely packed nanovilli structure enhanced the Raman signal, forming hotspots owing to its large surface area. Using experiments and electromagnetic simulations, we optimized the nanovilli structure as a SERS sensor. The sandwich-type aptasensor was designed using an aptamer and 4-Phenyl-1,2,4-triazoline-3,5-dione-methylene blue complex. The nanovilli-based aptasensor could sensitively detect various concentrations of 25-hydroxy vitamin D3, ranging from those found in deficient to excess conditions. The detection limit of the nanovilli-based sandwich-type aptasensor for 25-hydroxy vitamin D3 was 0.001 ng/mL, which is much lower than the deficiency concentration, and was detectable even in the human serum. In addition, our proposed sensor exhibited good repeatability (17.76%) and reproducibility (7.47%). Moreover, the nanovilli-based sandwich-type SERS aptasensor could selectively distinguish 25-hydroxy vitamin D3 from other vitamins. The silver nanovilli-based sandwich-type surface enhanced Raman scattering aptasensor opens a new avenue for the development of a bio-inspired vitamin-sensing platform.

To achieve an effective surface-enhanced Raman scattering (SERS) sensor with periodically distributed &ldquo, hot spots&rdquo, on wafer-scale substrates, we propose a hybrid approach combining physical nano-imprint lithography and a chemical deposition method to form a silver microbead array. Nano-imprint lithography (NIL) can lead to mass-production and high throughput, but is not appropriate for generating strong &ldquo, hot-spots.&rdquo, However, when we apply electrochemical deposition to an NIL substrate and the reaction time was increased to 45 s, periodical &ldquo, hot-spots&rdquo, between the microbeads were generated on the substrates. It contributed to increasing the enhancement factor (EF) and lowering the detection limit of the substrates to 4.40 &times, 106 and 1.0 &times, 10&minus, 11 M, respectively. In addition, this synthetic method exhibited good substrate-to-substrate reproducibility (RSD &lt, 9.4%). Our research suggests a new opportunity for expanding the SERS application.

Cortisol, which is a stress biomarker that causes various mental disorders, is found in sweat, saliva, blood, and urine. Because mental disorders resulting from stress are a silent contributor to various diseases, the detection of cortisol level is an important step in their prevention. Here, we developed a highly sensitive, localized surface plasmon resonance (LSPR) aptasensor for the direct detection of cortisol in saliva. The LSPR aptasensor was constructed using gold nanoparticles of different sizes. Subsequently, the surface of the LSPR substrate was immobilized using an aptamer for capturing cortisol. The detection capability of the LSPR aptasensor was compared with that of the antibody- immobilized sensor. The LSPR aptasensor displayed excellent detection capability for a wide range of cortisol concentrations extending from 0.1–1000 nM with a detection limit of 0.1 nM. In addition, the LSPR aptasensor was able to selectively detect cortisol among other substances with similar chemical structures (e.g., cortisone, corticosterone, progesterone, and triamcinolone). These results indicate that the LSPR aptasensor may be used for the highly sensitive and selective detection of cortisol in salivary samples.