Nano Convergence

Interfacial charge transfer on hierarchical synergistic shell wall of MXene/MoS on CdS nanospheres: heterostructure integrity for visible light responsive photocatalytic H evolution
Ranjith KS, Mohammadi A, Raju GSR, Huh YS and Han YK
Energy scarcity and environmental pollution have prompted research in hydrogen generation from solar to develop clean energy through highly efficient, effective, and long-lasting photocatalytic systems. Designing a catalyst with robust stability and an effective carrier separation rate was achieved through heterostructure assembly, but certain functionalities must be explored. In this paper we designed a ternary heterostructure assembly of CdS nanospheres wrapped with hierarchical shell walls of layered MXene-tagged MoS nanoflakes, forming intimate interfaces through an in-situ growth process. An in-layered shell wall of MXene with surface-wrapped MoS nanoflakes as a core-shell assembly improved the photo-corrosion resistance and accelerated the production of photocatalytic H (38.5 mmol g h), which is 10.7, 3.1, and 1.9 times faster than that of CdS, CdS-MXe, and CdS-MoS nanostructures, respectively. The apparent quantum efficiency of the CdS-MXe/MoS heterostructure was calculated to be 34.6% at λ = 420 nm. X-ray and ultraviolet photoelectron spectroscopies validated the electronic states, energy band alignment, and work function of the heterostructures, whilst time-resolved photoluminescence measured the carrier lifespan to evaluate the effective charge migration in the CdS-MXe/MoS heterostructure. The dual surface wrapping of MXe/MoS over CdS nanospheres confirmed the structural durability that remained intact throughout the photocatalytic reaction, promoting approximately 93.1% of its catalytic property even after five repeatable cycles. This study examined how the MXene heterostructure template improves the catalytic efficiency and opens a new way to design MXene-based durable heterostructure catalysts for solar-energy conversion.
Topological surface states of semimetal TaSb
Lee JE, Liu Y, Hwang J, Hwang C, Petrovic C, Park SY, Ryu H and Mo SK
Topological surface states, protected by the global symmetry of the materials, are the keys to understanding various novel electrical, magnetic, and optical properties. TaSb is a newly discovered topological material with unique transport phenomena, including negative magnetoresistance and resistivity plateau, whose microscopic understanding is yet to be reached. In this study, we investigate the electronic band structure of TaSb using angle-resolved photoemission spectroscopy and density functional theory. Our analyses reveal distinct bulk and surface states in TaSb, providing direct evidence of its topological nature. Notably, surface states predominate the electronic contribution near the Fermi level, while bulk bands are mostly located at higher binding energies. Our study underlines the importance of systematic investigations into the electronic structures of topological materials, offering insights into their fundamental properties and potential applications in future technologies.
Advances in materials and technologies for digital light processing 3D printing
Nam J and Kim M
Digital light processing (DLP) is a projection-based vat photopolymerization 3D printing technique that attracts increasing attention due to its high resolution and accuracy. The projection-based layer-by-layer deposition in DLP uses precise light control to cure photopolymer resin quickly, providing a smooth surface finish due to the uniform layer curing process. Additionally, the extensive material selection in DLP 3D printing, notably including existing photopolymerizable materials, presents a significant advantage compared with other 3D printing techniques with limited material choices. Studies in DLP can be categorized into two main domains: material-level and system-level innovation. Regarding material-level innovations, the development of photocurable resins with tailored rheological, photocuring, mechanical, and functional properties is crucial for expanding the application prospects of DLP technology. In this review, we comprehensively review the state-of-the-art advancements in DLP 3D printing, focusing on material innovations centered on functional materials, particularly various smart materials for 4D printing, in addition to piezoelectric ceramics and their composites with their applications in DLP. Additionally, we discuss the development of recyclable DLP resins to promote sustainable manufacturing practices. The state-of-the-art system-level innovations are also delineated, including recent progress in multi-materials DLP, grayscale DLP, AI-assisted DLP, and other related developments. We also highlight the current challenges and propose potential directions for future development. Exciting areas such as the creation of photocurable materials with stimuli-responsive functionality, ceramic DLP, recyclable DLP, and AI-enhanced DLP are still in their nascent stages. By exploring concepts like AI-assisted DLP recycling technology, the integration of these aspects can unlock significant opportunities for applications driven by DLP technology. Through this review, we aim to stimulate further interest and encourage active collaborations in advancing DLP resin materials and systems, fostering innovations in this dynamic field.
2D amorphous solids for sub-nanometer scale devices
Jang H, Kim H, Kim G, Cho S and Yang H
Amorphous solids are a type of condensed matter characterized by the absence of long-range order in their lattice structure. However, they still exhibit short- or medium-range order, which contributes to their versatile local and global electronic and chemical properties. Recently, 2D amorphous solids have gained attention for their exceptional mechanical and electronic features, which are unattainable in conventional crystalline materials. This review highlights the physical properties of ultrathin 2D amorphous solids, which are formed through covalent bonding and feature polyhedron structures with shared edges and corners. Two notable examples of 2D amorphous solids include honeycomb-structured nanosheets with mixed hybrid orbitals and layered materials with reduced coordination numbers of the elements. We provide an in-depth discussion of (1) the phase transition between crystalline and amorphous phases in 2D solids, (2) advanced synthetic methods for producing high-quality amorphous films with precise thickness control, and (3) the potential applications of sub-nanometer scale 2D amorphous solids. Lastly, we explore their potential to revolutionize the design of highly versatile electronic devices at sub-nanometer scales.
Integration of nanobiosensors into organ-on-chip systems for monitoring viral infections
Zhang J, Kim MH, Lee S and Park S
The integration of nanobiosensors into organ-on-chip (OoC) models offers a promising advancement in the study of viral infections and therapeutic development. Conventional research methods for studying viral infection, such as two-dimensional cell cultures and animal models, face challenges in replicating the complex and dynamic nature of human tissues. In contrast, OoC systems provide more accurate, physiologically relevant models for investigating viral infections, disease mechanisms, and host responses. Nanobiosensors, with their miniaturized designs and enhanced sensitivity, enable real-time, continuous, in situ monitoring of key biomarkers, such as cytokines and proteins within these systems. This review highlights the need for integrating nanobiosensors into OoC systems to advance virological research and improve therapeutic outcomes. Although there is extensive literature on biosensors for viral infection detection and OoC models for replicating infections, real integration of biosensors into OoCs for continuous monitoring remains unachieved. We discuss the advantages of nanobiosensor integration for real-time tracking of critical biomarkers within OoC models, key biosensor technologies, and current OoC systems relevant to viral infection studies. Additionally, we address the main technical challenges and propose solutions for successful integration. This review aims to guide the development of biosensor-integrated OoCs, paving the way for precise diagnostics and personalized treatments in virological research.
Manganese oxide nanomaterials: bridging synthesis and therapeutic innovations for cancer treatment
Balwe SG, Moon D, Hong M and Song JM
The advent of precision medicine in oncology emphasizes the urgent need for innovative therapeutic strategies that effectively integrate diagnosis and treatment while minimizing invasiveness. Manganese oxide nanomaterials (MONs) have emerged as a promising class of nanocarriers in biomedicine, particularly for targeted drug delivery and the therapeutic management of tumors. These nanomaterials are characterized by exceptional responsiveness to the tumor microenvironment (TME), high catalytic efficiency, favorable biodegradability, and advanced capabilities in magnetic resonance imaging. These attributes significantly enhance drug delivery, facilitate real-time bioimaging, and enable early tumor detection, thereby improving the precision and effectiveness of cancer therapies. This review highlights the significant advancements in the synthesis and therapeutic applications of MONs, beginning with a comprehensive overview of key synthetic methods, including thermal decomposition, potassium permanganate reduction, exfoliation, adsorption-oxidation, and hydro/solvothermal techniques. We delve into the preparation of MONs and H-MnO₂-based nanomaterials, emphasizing their chemical properties, surface modifications, and toxicity profiles, which are critical for their clinical application. Moreover, we discuss the notable applications of H-MnO₂-based nanomaterials in pH-responsive drug release, overcoming multidrug resistance (MDR), immunotherapy, and the development of nanovaccines for synergistic cancer treatments. By addressing the current challenges in the clinical translation of MONs, we propose future research directions for overcoming these obstacles. By underscoring the potential of MONs to transform cancer treatment paradigms, this review aims to inspire further investigations into their multifunctional applications in oncology, thus ultimately contributing to more effective and personalized therapeutic strategies.
Spectroelectrochemical insights into the intrinsic nature of lead halide perovskites
Min S, Jeon M, Cho J, Bang JH and Kamat PV
Lead halide perovskites have emerged as a new class of semiconductor materials with exceptional optoelectronic properties, sparking significant research interest in photovoltaics and light-emitting diodes. However, achieving long-term operational stability remains a critical hurdle. The soft, ionic nature of the halide perovskite lattice renders them vulnerable to various instabilities. These instabilities can be triggered by factors such as photoexcitation, electrical bias, and the surrounding electrolyte/solvent or atmosphere under operating conditions. Spectroelectrochemistry offers a powerful approach to bridge the gap between electrochemistry and photochemistry (or spectroscopy), by providing a comprehensive understanding of the band structure and excited-state dynamics of halide perovskites. This review summarizes recent advances that highlight the fundamental principles, the electronic band structure of halide perovskite materials, and the photoelectrochemical phenomena observed upon photo- and electro-chemical charge injections. Further, we discuss halide instability, encompassing halide oxidation, vacancy formation, ion migration, degradation, and sequential expulsion under electrical bias. Spectroelectrochemical studies that provide a deeper understanding of interfacial processes and halide mobility can pave the way for the design of more robust perovskites, accelerating future research and development efforts.
Highly sensitive multiplexed colorimetric lateral flow immunoassay by plasmon-controlled metal-silica isoform nanocomposites: PINs
Shin M, Kim W, Yoo K, Cho HS, Jang S, Bae HJ, An J, Lee JC, Chang H, Kim DE, Kim J, Lee LP and Jun BH
Lateral flow assay (LFA) systems use metal nanoparticles for rapid and convenient target detection and are extensively studied for the diagnostics of various diseases. Gold nanoparticles (AuNPs) are often used as probes in LFAs, displaying a single red color. However, there is a high demand for colorimetric LFAs to detect multiple biomarkers, requiring the use of multicolored NPs. Here, we present a highly sensitive multiplexed colorimetric lateral flow immunoassay by multicolored Plasmon-controlled metal-silica Isoform Nanocomposites (PINs). We utilized the localized surface plasmon resonance effect to create multi-colored PINs by precisely adjusting the distance between the NPs on the surface of PINs through the controlled addition of reduced gold and silver precursors. Through simulations, we also confirmed that the distance between nanoparticles on the surface of PINs significantly affects the color and colorimetric signal intensity of the PINs. We achieved multicolored PINs that exhibit stronger colorimetric signals, offering a new solution for LFA detection with high sensitivity and a 33 times reduced limit of detection (LOD) while maintaining consistent size deviations within 5%. We expect that our PINs-based colorimetric LFA will facilitate the sensitive and simultaneous detection of multiple biomarkers in point-of-care testing.
Multifunctional extracellular vesicles and edaravone-loaded scaffolds for kidney tissue regeneration by activating GDNF/RET pathway
Lee SY, Park JM, Rhim WK, Lee EH, Lee SH, Kim JY, Cha SG, Lee SH, Kim B, Hwang DY, Rho S, Ahn TK, Kim BS and Han DK
With the severity of chronic kidney disease worldwide, strategies to recover renal function via tissue regeneration provide alternatives to kidney replacement therapy. To exclude side effects from direct cell transplantation, extracellular vesicles (EVs) are great substitutes representing paracrine cell signaling. To build three-dimensional structures for implantation into the 5/6 nephrectomy model by incorporating bioactive materials, including multifunctional EVs (mEVs), porous PMEZE/mEV scaffolds were developed in combination with edaravone (EDV; E) and mEV based on PMEZ scaffolds with PLGA (P), MH-RA (M), ECM (E), ZnO-ALA (Z). The oxygen free radical scavenger EDV was incorporated to induce tubular regeneration. mEVs were engineered to serve regenerative activities with a combination of two EVs from SDF-1α overexpressed tonsil-derived mesenchymal stem cells (sEVs) and intermediate mesoderm (IM) cells during differentiation into kidney progenitor cells (dEVs). mEVs displayed beneficial effects on regeneration by facilitating migration and inducing differentiation of surrounding stem cells, and EDV improved kidney function by regulating the GDNF/RET pathway and their downstream genes. The promotion of MSC recruitment was confirmed with sEV particles number dependently, and the regulation of the GDNF/RET pathway by the effect of EDV and its enhanced effect by mEVs were elucidated using in vitro analysis. The regeneration of tubules was additionally demonstrated through the increased expression of aquaporin-1 (AQP-1) and cadherin-16 (CDH16) for proximal tubules, and calbindin and PAX2 for distal tubules in the renal defect model. With these, structural regeneration and functional recovery were achieved with kidney regeneration in the 5/6 nephrectomy mice model.
Simple and Cost-Effective Generation of 3D Cell Sheets and Spheroids Using Curvature-Controlled Paraffin Wax Substrates
Kim H, Koo KM, Kim CD, Byun MJ, Park CG, Son H, Kim HR and Kim TH
The challenges associated with animal testing in pharmaceutical development have driven the search for alternative in vitro models that mimic human tissues more accurately. In this study, we present a simple and cost-effective method for generating 3D cell sheets and spheroids using curvature-controlled paraffin wax films, which are easily accessible laboratory materials that eliminate the need for extracellular matrix (ECM) components or thermo-responsive polymers. By adjusting the curvature of the paraffin wax film, we successfully generated human periodontal ligament fibroblast (HPdLF) cell sheets and bone marrow-derived mesenchymal stem cell (hBMSC) spheroids. Key parameters, such as cell density, substrate curvature, and incubation time, were identified as critical factors for optimizing the formation of these 3D structures. In addition, the use of quantum dots (QDs) for cell tracking enabled long-term visualization and distinction between different cell types within complex tissue-like structures. We further demonstrated that wrapping the hBMSC spheroids with HPdLF cell sheets partially replicated the connective tissue structure of the periodontal ligament surrounding the tooth root. This highlights the potential of this platform for the construction of more sophisticated tissue-mimicking assemblies. In conclusion, curvature-controlled paraffin wax films provide a versatile and practical approach for 3D cell cultures. This simplifies the generation of both cell sheets and spheroids, offering a promising tool for tissue engineering and regenerative medicine applications, where precise cell-to-cell interactions are essential.
Evaluation of size-dependent uptake, transport and cytotoxicity of polystyrene microplastic in a blood-brain barrier (BBB) model
Cho Y, Seo EU, Hwang KS, Kim H, Choi J and Kim HN
Microplastics, particularly those in the micrometer scale, have been shown to enter the human body through ingestion, inhalation, and dermal contact. Recent research indicates that microplastics can potentially impact the central nervous system (CNS) by crossing the blood-brain barrier (BBB). However, the exact mechanisms of their transport, uptake, and subsequent toxicity at BBB remain unclear. In this study, we evaluated the size-dependent uptake and cytotoxicity of polystyrene microparticles using an engineered BBB model. Our findings demonstrate that 0.2 μm polystyrene microparticles exhibit significantly higher uptake and transendothelial transport compared to 1.0 μm polystyrene microparticles, leading to increased permeability and cellular damage. After 24 h of exposure, permeability increased by 15.6-fold for the 0.2 μm particles and 2-fold for the 1.0 μm particles compared to the control. After 72 h of exposure, permeability further increased by 27.3-fold for the 0.2 μm particles and a 4.5-fold for the 1.0 μm particles compared to the control. Notably, microplastics administration following TNF-α treatment resulted in enhanced absorption and greater BBB damage compared to non-stimulated conditions. Additionally, the size-dependent toxicity observed differently between 2D cultured cells and 3D BBB models, highlighting the importance of testing models in evaluating environmental toxicity.
Designing injectable dermal matrix hydrogel combined with silver nanoparticles for methicillin-resistant Staphylococcus aureus infected wounds healing
Chen S, Yao J, Huo S, Xu C, Yang R, Tao D, Fang B, Ma G, Zhu Z, Zhang Y and Guo J
Hydrogel-based delivery systems have now emerged as a pivotal platform for addressing chronic tissue defects, leveraging their innate capacity to suppress pathogenic infections and facilitate expedited tissue regeneration. In this work, an injectable hydrogel dressing, termed AgNPs-dermal matrix hydrogel (Ag@ADMH), has been designed to expedite the healing process of wounds afflicted with methicillin-resistant Staphylococcus aureus (MRSA), featuring sustained antibacterial efficacy. The synthesis of the hydrogel dressing entailed a self-assembly process of collagen fibers within an acellular dermal matrix to construct a three-dimensional scaffold, encapsulated with plant polyphenol-functionalized silver nanoparticles (AgNPs). The Ag@ADMH demonstrated exceptional biocompatibility, and enables a sustained release of AgNPs, ensuring prolonged antimicrobial activity. Moreover, the in vitro RT-qPCR analysis revealed that compared with ADMH, Ag@ADMH diminish the expression of iNOS while augmenting CD206 expression, thereby mitigating the inflammatory response and fostering wound healing. Especially, the Ag@ADMH facilitated a reduction in M1 macrophage polarization, as evidenced by a significant decrement in the M1 polarization trend and an enhanced M2/M1 ratio in dermal matrix hydrogels laden with AgNPs, corroborated by confocal microscopy and flow cytometry analyses of macrophage phenotypes. The in vivo assessments indicated that Ag@ADMH minimized fibrous capsule formation. In a full-thickness skin defect model of MRSA infection, the formulation significantly attenuated the inflammatory response by reducing MPO and CD68 expression levels, concurrently promoting collagen synthesis and CD34 expression, pivotal for vasculogenesis, thereby accelerating the resolution of MRSA-infected wounds. These attributes underscore the injectable extracellular matrix hydrogel as a formidable strategy for the remediation and regeneration of infected wounds.
Perovskite nanocomposites: synthesis, properties, and applications from renewable energy to optoelectronics
Choi Y, Han S, Park BI, Xu Z, Huang Q, Bae S, Kim JS, Kim SO, Meng Y, Kim SI, Moon JY, Roh I, Park JW and Bae SH
The oxide and halide perovskite materials with a ABX structure exhibit a number of excellent properties, including a high dielectric constant, electrochemical properties, a wide band gap, and a large absorption coefficient. These properties have led to a range of applications, including renewable energy and optoelectronics, where high-performance catalysts are needed. However, it is difficult for a single structure of perovskite alone to simultaneously fulfill the diverse needs of multiple applications, such as high performance and good stability at the same time. Consequently, perovskite nanocomposites have been developed to address the current limitations and enhance their functionality by combining perovskite with two or more materials to create complementary materials. This review paper categorizes perovskite nanocomposites according to their structural composition and outlines their synthesis methodologies, as well as their applications in various fields. These include fuel cells, electrochemical water splitting, CO mitigation, supercapacitors, and optoelectronic devices. Additionally, the review presents a summary of their research status, practical challenges, and future prospects in the fields of renewable energy and electronics.
Correction to: PFP@PLGA/CuSbS‑mediated PTT ablates hepatocellular carcinoma by inhibiting the RAS/MAPK/MT‑CO1 signaling pathway
Dong T, Jiang J, Zhang H, Liu H, Zou X, Niu J, Mao Y, Zhu M, Chen X, Li Z, Chen Y, Shi C and Yang X
Simultaneous low-frequency vibration isolation and energy harvesting via attachable metamaterials
Hyun J, Jung J, Park J, Choi W and Kim M
In this study, we achieved energy localization and amplification of flexural vibrations by utilizing the defect mode of plate-attachable locally resonant metamaterials, thereby realizing compact and low-frequency vibration energy suppression and energy harvesting with enhanced output performance. We designed a cantilever-based metamaterial unit cell to induce local resonance inside a periodic supercell structure and form a bandgap within the targeted low-frequency range of 300-450 Hz. Subsequently, a defect area was created by removing some unit cells to break the periodicity inside the metamaterial, which led to the isolation and localization of the vibration energy. This localized vibration energy was simultaneously converted into electrical energy by a piezoelectric energy harvester coupled with a metamaterial inside the defect area. Consequently, a substantially enhanced energy harvesting output power was achieved at 360 Hz, which was 43-times higher than that of a bare plate without metamaterials. The proposed local resonant metamaterial offers a useful and multifunctional platform with the capability of vibration energy isolation and harvesting, while exhibiting easy handling via attachable designs that can be tailored in the low-frequency regime.
Zero-crosstalk silicon photonic refractive index sensor with subwavelength gratings
Ahmed SZ, Hasan M, Kim K and Kim S
Silicon photonic index sensors have received significant attention for label-free bio and gas-sensing applications, offering cost-effective and scalable solutions. Here, we introduce an ultra-compact silicon photonic refractive index sensor that leverages zero-crosstalk singularity responses enabled by subwavelength gratings. The subwavelength gratings are precisely engineered to achieve an anisotropic perturbation-led zero-crosstalk, resulting in a single transmission dip singularity in the spectrum that is independent of device length. The sensor is optimized for the transverse magnetic mode operation, where the subwavelength gratings are arranged perpendicular to the propagation direction to support a leaky-like mode and maximize the evanescent field interaction with the analyte space. Experimental results demonstrate a high wavelength sensitivity of - 410 nm/RIU and an intensity sensitivity of 395 dB/RIU, with a compact device footprint of approximately 82.8 μm. Distinct from other resonant and interferometric sensors, our approach provides an FSR-free single-dip spectral response on a small device footprint, overcoming common challenges faced by traditional sensors, such as signal/phase ambiguity, sensitivity fading, limited detection range, and the necessity for large device footprints. This makes our sensor ideal for simplified intensity interrogation. The proposed sensor holds promise for a range of on-chip refractive index sensing applications, from gas to biochemical detection, representing a significant step towards efficient and miniaturized photonic sensing solutions.
Mechanism exploration of synergistic photo-immunotherapy strategy based on a novel exosome-like nanosystem for remodeling the immune microenvironment of HCC
Chen Y, Li X, Shang H, Sun Y, Wang C, Wang X, Tian H, Yang H, Zhang L, Deng L, Yang K, Wu B and Cheng W
The immunosuppressive tumor microenvironment (TME) has become a major challenge in cancer immunotherapy, with abundant tumor-associated macrophages (TAMs) playing a key role in promoting tumor immune escape by displaying an immunosuppressive (M2) phenotype. Recently, it was reported that M1 macrophage-derived nanovesicles (M1NVs) can reprogram TAMs to an anti-tumor M1 phenotype, thereby significantly alleviating the immunosuppressive TME and enhancing the anti-tumor efficacy of immunotherapy. Herein, we developed M1NVs loaded with mesoporous dopamine (MPDA) and indocyanine green (ICG), which facilitated the recruitment of M2 TAMs through synergistic photothermal and photodynamic therapy. Thereafter, M1NVs can induce M1 repolarization of TAMs, resulting in increased infiltration of cytotoxic T lymphocytes within the tumor to promote tumor regression. This study investigated the effect of phototherapy on the immune environment of liver cancer using single-cell RNA sequencing (scRNA-seq) by comparing HCC tissues before and after MPDA/ICG@M1NVs + NIR treatment. The results showed significant shifts in cell composition and gene expression, with decreases in epithelial cells, B cells, and macrophages and increases in neutrophils and myeloid cells. Additionally, gene analysis indicated a reduction in pro-inflammatory signals and immunosuppressive functions, along with enhanced B-cell function and anti-tumor immunity, downregulation of the Gtsf1 gene in the epithelial cells of the MPDA/ICG @M1NVs + NIR group, and decreased expression of the lars2 gene in immune subpopulations. Eno3 expression is reduced in M1 macrophages, whereas Clec4a3 expression is downregulated in M2 macrophages. Notably, the B cell population decreased, whereas Pou2f2 expression increased. These genes regulate cell growth, death, metabolism, and tumor environment, indicating their key role in HCC progression. This study highlights the potential for understanding cellular and molecular dynamics to improve immunotherapy.
Conveyor CVD to high-quality and productivity of large-area graphene and its potentiality
Lee DY, Nam J, Lee GY, Lee I, Jang AR and Kim KS
The mass production of high-quality graphene is required for industrial application as a future electronic material. However, the chemical vapor deposition (CVD) systems previously studied for graphene production face bottlenecks in terms of quality, speed, and reproducibility. Herein, we report a novel conveyor CVD system that enables rapid graphene synthesis using liquid precursors. Pristine and nitrogen-doped graphene samples of a size comparable to a smartphone (15 cm × 5 cm) are successfully synthesized at temperatures of 900, 950, and 1000 °C using butane and pyridine, respectively. Raman spectroscopy allows optimization of the rapid-synthesis conditions to achieve uniformity and high quality. By conducting compositional analysis via X-ray photoelectron spectroscopy as well as electrical characterization, it is confirmed that graphene synthesis and nitrogen doping degree can be adjusted by varying the synthesis conditions. Testing the corresponding graphene samples as gas-sensor channels for NH and NO and evaluating their response characteristics show that the gas sensors exhibit polar characteristics in terms of gas adsorption and desorption depending on the type of gas, with contrasting characteristics depending on the presence or absence of nitrogen doping; nitrogen-doped graphene exhibits superior gas-sensing sensitivity and response speed compared with pristine graphene.
Advancing SERS as a quantitative technique: challenges, considerations, and correlative approaches to aid validation
Sloan-Dennison S, Wallace GQ, Hassanain WA, Laing S, Faulds K and Graham D
Surface-enhanced Raman scattering (SERS) remains a significant area of research since it's discovery 50 years ago. The surface-based technique has been used in a wide variety of fields, most prominently in chemical detection, cellular imaging and medical diagnostics, offering high sensitivity and specificity when probing and quantifying a chosen analyte or monitoring nanoparticle uptake and accumulation. However, despite its promise, SERS is mostly confined to academic laboratories and is not recognised as a gold standard analytical technique. This is due to the variations that are observed in SERS measurements, mainly caused by poorly characterised SERS substrates, lack of universal calibration methods and uncorrelated results. To convince the wider scientific community that SERS should be a routinely used analytical technique, the field is now focusing on methods that will increase the reproducibility of the SERS signals and how to validate the results with more well-established techniques. This review explores the difficulties experienced by SERS users, the methods adopted to reduce variation and suggestions of best practices and strategies that should be adopted if one is to achieve absolute quantification.
Excimer-ultraviolet-lamp-assisted selective etching of single-layer graphene and its application in edge-contact devices
Shin M, Kim JH, Ko JY, Haidari MM, Jang DJ, Lee K, Kim K, Kim H, Park BH and Choi JS
Since the discovery of graphene and its remarkable properties, researchers have actively explored advanced graphene-patterning technologies. While the etching process is pivotal in shaping graphene channels, existing etching techniques have limitations such as low speed, high cost, residue contamination, and rough edges. Therefore, the development of facile and efficient etching methods is necessary. This study entailed the development of a novel technique for patterning graphene through dry etching, utilizing selective photochemical reactions precisely targeted at single-layer graphene (SLG) surfaces. This process is facilitated by an excimer ultraviolet lamp emitting light at a wavelength of 172 nm. The effectiveness of this technique in selectively removing SLG over large areas, leaving the few-layer graphene intact and clean, was confirmed by various spectroscopic analyses. Furthermore, we explored the application of this technique to device fabrication, revealing its potential to enhance the electrical properties of SLG-based devices. One-dimensional (1D) edge contacts fabricated using this method not only exhibited enhanced electrical transport characteristics compared to two-dimensional contact devices but also demonstrated enhanced efficiency in fabricating conventional 1D-contacted devices. This study addresses the demand for advanced technologies suitable for next-generation graphene devices, providing a promising and versatile graphene-patterning approach with broad applicability and high efficiency.
Correction: Emergence of two distinct phase transitions in monolayer CoSe on graphene
Rhee TG, Lam NH, Kim YG, Gu M, Hwang J, Bostwick A, Mo SK, Chun SH, Kim J, Chang YJ and Choi BK