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Several important sensory physical quantities exist but are difficult to quantify, including food freshness. With the aid of a hyperspectral imaging system (HIS) and machine learning (ML), meat freshness is converted into a measurable physical quantity, i.e., freshness index (F. I.), in this study. F. I. is defined from meat fluorescence, which has a strong correlation with bacterial density, using a line-scan-type HIS stimulated at 365 nm. Combined with ML techniques, hyperspectral images are processed more efficiently. By employing linear discriminant and quadratic component analyses for hyperspectral images, F. I. can be estimated from its decision boundary after hyperspectral images are taken at an unknown freshness state. Advanced sensing versatility utilized by computational sensing systems allows hyper-personalization and hyper-customization of human life with the aid of home appliances and smartphones.

Measuring, recoding and analyzing of spectral information of materials as its unique finger print using a ubiquitous smart phone has been craved for by scientists and consumers. We demonstrated the concept of a spectral barcode in drug classification with a smartphone Raman spectrometer. The spectral barcode is a 2D Raman spectral intensity map captured with a CMOS-image sensor integrated with a periodic array of band-pass filters. We classified the type of each drug by capturing its spectrum and using a convolutional neural network (CNN) that we trained to identify 11 major spectral components. This yielded a prediction accuracy of 99%, including drugs in the same category but from different brands. The accuracy of identifying drugs by individual brand was 79.5%, which improved to 83.2% simultaneously using the spectral barcode and RGB image in the CNN. This inherent property-based labeling system will facilitate fundamental research and business opportunities.

Stimuli-responsive nanoparticles are favorable for improving the selective delivery and rational vocation that easily avoids the undesirable barriers or side effects, leading to a further improved therapeutic efficiency. Furthermore, multifunctional nanomaterials have been extensively developed as attractive candidates for theranostic reagents for cancer treatment. In this article, we developed reversibly pH-responsive gold nanoparticles (AuNPs) with an enhanced Raman scattering signal as well as an efficient photothermal effect and demonstrated their applications as a theranostic reagent for cancer treatment. Surfaces of these AuNPs were modified with mixed layers of Cy3-modified single-stranded DNA (ssDNA-Cy3) for Raman probing and a negative charge supply and cytochrome C (Cyt C) for pH-responsive charge inversion. This combination of pH-responsive ligands and Raman probes played an important role in inducing the assembly or disassembly of AuNPs corresponding to the neighboring pH, accompanied by an additional highly distinguished Raman signal intensity. An operative reversible response of the AuNPs to pH is endowed with the characteristic behavior of AuNPs with the cancerous cell's acidic microenvironment of low pH. The responsive aggregation of AuNPs in a lower pH medium provides highly amplified signals attributed to well-formed hot spots between the particle surfaces that deliver better Raman scattering signals. The acidic pH-responsive aggregation of the particles also provided efficient photothermal treatments using a long-wavelength laser light with the benefit of deeper penetration for cancer cells.

Artificial synaptic platforms are promising for next-generation semiconductor computing devices; however, state-of-the-art optoelectronic approaches remain challenging, owing to their unstable charge trap states and limited integration. We demonstrate wide-band-gap (WBG) III-V materials for photoelectronic neural networks. Our experimental analysis shows that the enhanced crystallinity of WBG synapses promotes better synaptic characteristics, such as effective multilevel states, a wider dynamic range, and linearity, allowing the better power consumption, training, and recognition accuracy of artificial neural networks. Furthermore, light-frequency-dependent memory characteristics suggest that artificial optoelectronic synapses with improved crystallinity support the transition from short-term potentiation to long-term potentiation, implying a clear emulation of the psychological multistorage model. This is attributed to the charge trapping in deep-level states and suppresses fast decay and nonradiative recombination in shallow traps. We believe that the fingerprints of these WBG synaptic characteristics provide an effective strategy for establishing an artificial optoelectronic synaptic architecture for innovative neuromorphic computing.

Numerous efforts have been made to establish three-dimensional (3D) cell cultures that mimic the structure, cell composition, and functions of actual tissues and organs in vitro; however, owing to its intrinsic complexity, precise characterization of 3D differentiation remains challenging and often results in high variations in the resulting differentiated spheroids. This study reports a 3D Raman mapping-based analytical method that helps us to identify the crucial factors responsible for inducing variability in differentiated stem cell spheroids. Human dental pulp stem cell spheroids were generated at various cell densities using the hanging drop (HD) and molded parafilm-based (MP) methods and were then further subjected to odontogenic differentiation. Thereafter, the 3D cellular differentiation in these spheroids was analyzed based on three different Raman peaks, namely, 960, 1156/1528, and 2935 cm-1, which correspond to hydroxyapatite (HA, odontogenic differentiation marker), β-carotene (precursor of HA), and proteins/cellular components (cell reference). By correlating such cell differentiation-related peaks and water/medium peaks (3400 cm-1), we discovered that the diffusion of the medium containing various nutrients and differentiation factors was crucial in determining the variations in 3D differentiation of stem cell spheroids. Odontogenic differentiation was majorly induced at the outer shell of HD spheroids (up to ∼20 μm), whereas odontogenic differentiation was markedly induced in MP spheroids (up to 40-50 μm). Considering the challenges associated with high variations in spheroid and organoid differentiation, we conclude that the proposed Raman-based 3D analysis plays a pivotal role in stem cell-based regenerative therapy and drug screening.

The inherent risk of side reactions in lithium ion batteries (LIBs) is a crucial issue for large battery packs. To mitigate this problem, there have been previous studies that have attempted to reveal the possible chemical reactions from decomposition of electrolytes and electrode materials’ reactions during cycling. In particular, the gases expelled during decomposition have garnered research attention as they are explosive, flammable, toxic, and raise the inner pressure of a cell drastically. In addition, it is important to understand thermal effects on gas evolution or degradation of the electrode layer because batteries are normally exposed to a warm operation condition. Herein, the gases expelled within commercial 18650 cylindrical type LIB cells were investigated in moderate thermal conditions in a charged state. The investigation was conducted using a lab-made in situ Raman spectroscopic analysis system and performing comprehensive transient electrochemical analyses. Our Raman spectroscopy system could explore the battery reactions non-disruptively, which is critical for the interior of a cell. Through this in situ technique, the gas expelling trends upon the thermal conditions were elucidated; furthermore, detrimental effects of gas generation reactions to a cell integrity were proposed through comparison with the electrochemical results.

The chemical transformation from zinc oxide (ZnO) to zinc sulphide (ZnS), using di-tert-butyl disulphide (TBDS) as a highly reactive sulphur precursor, is demonstrated herein. Through anion exchange, we investigate the phase and morphological changes associated with the nanoparticle (NP) transformation of ZnO to ZnS using TBDS. The Zn–O–S alloy was not formed through the anion exchange reaction, only the ZnO and ZnS phases were detected. The NPs were transformed from a solid sphere to a hollow structure, induced by the nanoscale Kirkendall effect. Even with the dramatic shape and phase changes occurring in the NPs, the Zn oxidation state remained as 2+ throughout the 2 h anion exchange reaction. In addition, trioctylphosphine (TOP), a soft base ligand, increased the anion exchange reaction rate, facilitating the reaction with TBDS. Furthermore, anion exchange with elemental sulphur required a longer reaction time (3 h) than that with TBDS (2 h). Consequently, this study offers not only insights into phase and morphological transformations by anion exchange, but also the advantages of utilizing TBDS as a sulphur precursor.

We demonstrated a simple and effective processing protocol to improve the electrical conductivity of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films via post-treatment with an alcohol-based solvent, 2-chloroethanol (2-CE), and to enhance their performance as a transparent anode in organic photovoltaic cells (OPVs). Owing to its moderate boiling point, in contrast to previously reported chemicals, 2-CE is advantageous both for handling as a liquid-phase chemical and for drying from the films via evaporation. We compared the optical and electrical properties of the 2-CE-treated PEDOT:PSS with those of standard PEDOT:PSS-based electrodes with the addition of 5 vol% dimethyl sulfoxide (DMSO). With a similar thickness and transmittance in the visible region, the 2-CE-treated polymer electrodes outperformed the DMSO-added films with regard to the electrical conductivity (762 S cm−1 vs. 439 S cm−1). The work functions were almost identical: ∼5 eV. We fabricated and characterized organic photovoltaic devices using the anodes and polymer:fullerene blends and found that the 2-CE treatment resulted in higher device performance. Additionally, the 2-CE treatment was applicable to OPVs on a flexible plastic substrate, indicating the effectiveness of the proposed protocol.

While aluminum nitride (AlN) is at the heart of next-generation optoelectronic applications, the growth of highly crystalline AlN remains a challenge. We investigated the formation of nanovoids (NVs) in AlN crystals and the concomitant effect on the structural and optoelectronic characteristics of AlN crystal layers. Surface treatment with a H3PO4 acid solution etched the initial AlN layer and as-deposited template to introduce NVs between the initial and subsequent AlN layers, and at the interfaces between the epitaxial layers and substrate during AlN regrowth. This approach suppressed the propagation of threading dislocations to the surface, thus promoting the growth of highly crystalline AlN materials. Raman spectroscopy analysis revealed that the residual stresses in AlN films were relaxed by the formation of nanovoids. UV-visible spectrometer analysis confirmed that the regrown AlN had an optical bandgap of 6.08 eV and could be suitable for use in a solar-blind UV photodetector. Furthermore, a metal–semiconductor–metal (MSM) photodetector fabricated on AlN crystals regrown on a template, acid-etched with nanovoids, showed improved photoresponse characteristics and solid solar-blind UV photodetector capability, compared to a MSM fabricated on AlN crystals regrown on an untreated template. We expect that our research will support and promote further development of group-III nitride materials and optoelectronic devices with excellent structural properties.

Direct messenger ribonucleic acid (mRNA) delivery to target cells or tissues has revolutionized the field of biotechnology. However, the applicability of regenerative medicine is limited by the technical difficulties of various mRNA-loaded nanocarriers. Herein, we report a new conductive hybrid film that could guide osteogenic differentiation of human adipose-derived mesenchymal stem cells (hADMSCs) via electrically controlled mRNA delivery. To find optimal electrical conductivity and mRNA-loading capacity, the polypyrrole-graphene oxide (PPy-GO) hybrid film was electropolymerized on indium tin oxide substrates. We found that the fluorescein sodium salt, a molecule partially mimicking the physical and chemical properties of mRNAs, can be effectively absorbed and released by electrical stimulation (ES). The hADMSCs cultivated on the PPy-GO hybrid film loaded with pre-osteogenic mRNAs showed the highest osteogenic differentiation under electrical stimulation. This platform can load various types of RNAs thus highly promising as a new nucleic acid delivery tool for the development of stem cell-based therapeutics.Supplementary material (electrochemical and FT-IR analysis on the film, additional SEM, AFM and C-AFM images of the film, optical and fluorescence images of cells, and the primers used for RT-qPCR analysis) is available in the online version of this article at 10.1007/s12274-022-4613-y.

Atomic-layered materials, such as high-quality bismuth oxychalcogenides, which are composed of oppositely charged alternate layers grown using chemical vapor deposition, have attracted considerable attention. Their physical properties are well-suited for high-speed, low-power-consumption optoelectronic devices, and the rapid determination of their crystallographic characteristics is crucial for scalability and integration. In this study, we introduce how the crystallographic structure and quality of such materials can be projected through Raman spectroscopy analysis. Frequency modes at ∼55, ∼78, ∼360, and ∼434 cm

This study proposes a stand-off Raman spectroscopy system using dual-wavelength in the ultraviolet (UV) region to detect hazardous chemicals. The Raman spectrum generated by the UV excitation source avoids solar background noise during daytime for chemical detection as the spectrum is in the solar blind range. Wavelengths of 213 and 266 nm by 5th and 4th harmonics are generated from Nd:YAG laser. However, Raman spectra of chemicals exhibit different signal-to-noise ratios for both the excitation wavelengths; therefore, to detect such chemicals, Raman spectra by two sources are required. Raman spectra were acquired using a dual-wavelength laser and spectrometer with a single grating and detector at the wavelengths of 213 and 266 nm simultaneously. The Raman spectra of sulfuric acid, 2-chloroethyl ethyl sulfide, and dimethyl methylphosphonate were acquired and analyzed, thus highlighting the application of dual-wavelength Raman spectroscopy. For efficient chemical detection in the field, we have ensured that the system developed in this study is robust.

2D heterostructures made of transition metal dichalcogenides (TMD) have emerged as potential building blocks for new-generation 2D electronics due to their interesting physical properties at the interfaces. The bandgap, work function, and optical constants are composition dependent, and the spectrum of applications can be expanded by producing alloy-based heterostructures. Herein, the successful synthesis of monolayer and bilayer lateral heterostructures, based on ternary alloys of MoS

The enhanced growth of Cu oxides underneath graphene grown on a Cu substrate has been of great interest to many groups. In this work, the strain and doping status of graphene, based on the gradual growth of Cu oxides from underneath, were systematically studied using time evolution Raman spectroscopy. The compressive strain to graphene, due to the thermal expansion coefficient difference between graphene and the Cu substrate, was almost released by the nonuniform Cu

Graphene oxide (GO) has proven to be a highly promising material across various biomedical research avenues, including cancer therapy and stem cell-based regenerative medicine. However, creating a uniform GO coating as a thin layer on desired substrates has been considered challenging owing to the intrinsic variability of the size and shape of GO. Herein, a new method is introduced that enables highly uniform GO thin film (UGTF) fabrication on various biocompatible substrates. By optimizing the composition of the GO suspension and preheating process to the substrates, the "coffee-ring effect" is significantly suppressed. After applying a special postsmoothing process referred to as the low-oxygen concentration and low electrical energy plasma (LOLP) treatment, GO is converted to small fragments with a film thickness of up to several nanometers (≈5.1 nm) and a height variation of only 0.6 nm, based on atomic force microscopy images. The uniform GO thin film can also be generated as periodic micropatterns on glass and polymer substrates, which are effective in one-step micropatterning of both antibodies and mouse melanoma cells (B16-F10). Therefore, it can be concluded that the developed UGTF is useful for various graphene-based biological applications.

The chemical transformation from zinc oxide (ZnO) to zinc sulphide (ZnS), using di-tert-butyl disulphide (TBDS) as a highly reactive sulphur precursor, is demonstrated herein. Through anion exchange, we investigate the phase and morphological changes associated with the nanoparticle (NP) transformation of ZnO to ZnS using TBDS. The Zn-O-S alloy was not formed through the anion exchange reaction, only the ZnO and ZnS phases were detected. The NPs were transformed from a solid sphere to a hollow structure, induced by the nanoscale Kirkendall effect. Even with the dramatic shape and phase changes occurring in the NPs, the Zn oxidation state remained as 2+ throughout the 2 h anion exchange reaction. In addition, trioctylphosphine (TOP), a soft base ligand, increased the anion exchange reaction rate, facilitating the reaction with TBDS. Furthermore, anion exchange with elemental sulphur required a longer reaction time (3 h) than that with TBDS (2 h). Consequently, this study offers not only insights into phase and morphological transformations by anion exchange, but also the advantages of utilizing TBDS as a sulphur precursor.

Colloidal nanoparticles (NPs) have been recently spotlighted as building blocks for various nanostructured devices. Their collective properties have been exhibited by arranging them on a substrate to form assembled NPs. In particular, electrophoretic deposition (EPD) is an emerging fabrication method for such nanostructured films. To maximize the benefits of this method, further studies are required to fully elucidate the key parameters that influence the NP deposition. Herein, two key parameters are examined, namely: (i) the aging of colloidal NPs and (ii) the charge formation by surface ligands. The aging of Cu2-xS NPs changes the charge states, thus leading to different NP deposition behaviors. The SEM images of NP films, dynamic light scattering, and zeta potential results demonstrated that the charge control and restoration of interparticle interactions for aged NPs were achieved via simple ligand engineering. The charge control of colloidal NPs was found to be more dominant than the influence of aging, which can alter the surface charges of the NPs. The present results thus reveal that the charge formation on the colloidal NPs, which depends on the surface ligands, is an important controllable parameter in EPD.

In this study, we developed a effective processing protocol to modify the electrical conductivity of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films via post-treatment with an alcohol-based solvent, 2-chloroethanol (2-CE), and to improve their performance as a transparent anode in organic photovoltaics (OPVs). Due to its appropriate boiling point, 2-CE is advantageous both for treating as a liquid phase chemical and for drying from the films via evaporation. We compared the optical and electrical properties of the 2-CE-treated PEDOT:PSS with those of standard 5 vol% dimethyl sulfoxide (DMSO) added PEDOT:PSS. With a similar thickness and transmittance in the visible region, the 2-CE-treated polymer electrodes surpassed the DMSO-added films with regard to the electrical conductivity. Additionally, we conducted X-ray Photoelectron Spectrometer (XPS), Ultraviolet Photoelectron Spectroscopy (UPS), J-V characteristic, Photoluminescence (PL), Impedance spectroscopy.

Post-growth graphene transfer to a variety of host substrates for circuitry fabrication has been among the most popular subjects since its successful development via chemical vapor deposition in the past decade. Fast and reliable evaluation tools for its morphological characteristics are essential for the development of defect-free transfer protocols. The implementation of conventional techniques, such as Raman spectroscopy, atomic force microscopy (AFM), and transmission electron microscopy in production quality control at an industrial scale is difficult because they are limited to local areas, are time consuming, and their operation is complex. However, through a one-shot measurement within a few seconds, phase-shifting interferometry (PSI) successfully scans ≈1 mm2 of transferred graphene with a vertical resolution of ≈0.1 nm. This provides crucial morphological information, such as the surface roughness derived from polymer residues, the thickness of the graphene, and its adhesive strength with respect to the target substrates. Graphene samples transferred via four different methods are evaluated using PSI, Raman spectroscopy, and AFM. Although the thickness of the nanomaterials measured by PSI can be highly sensitive to their refractive indices, PSI is successfully demonstrated to be a powerful tool for investigating the morphological characteristics of the transferred graphene for industrial and research purposes.

Because large-scale lithium-ion battery (LIB) packs are compactly constructed using many LIB cells, one battery can cause fire of the other LIB cells when a few cells of them are damaged by accident owing to the latent risk of thermal decomposition reactions. To alleviate this problem, research seeks to provide an understanding of the gas generating mechanisms during cycling, electrolyte decomposition, and electrode material reactions. Understanding gas behaviors can prevent propagation of a battery fire and other hazardous situations. Therefore, in this study, we investigate commercial 18650 cylindrical cells with long-term cycling. A lab-made in-situ Raman spectroscopic system and comprehensive transient electrochemical analyses are utilized to explore four gas expulsion phases. In addition, gas generation data are assessed for various overcharging voltage cutoffs (4.2–4.6 V). For the first time, furthermore, a simple empircal mathematical model is proposed, based on the distinct gas evolution phases, that can provide the insight into the state of health (SOH) of commercial 18650 cells.

Graphene derivatives are known to be suitable for biomedical applications, especially for stem cell-based therapies. Herein, we report the size effects of graphene oxide (GO) on differentiation of human adipose-derived mesenchymal stem cells (hADMSCs), using micro-sized (MGO) and nano-sized graphene oxide (NGO) sheets. The MGO and NGO sheets having lateral sizes of 1–10 μm and 100–300 nm, respectively, are coated on glass substrates by drop casting. The hADMSCs grown on the MGO-coated substrates show enhanced cell spreading and proliferation rate when compared with those of NGO counterpart, regardless of their densities. The GO size-dependency of hADMSCs becomes more prominent when it comes to their differentiation capabilities. After 4 weeks of differentiation under the same culture conditions, the osteogenesis of hADMSCs grown on the MGO-coated substrate is particularly higher than that on the NGO-coated substrate. The difference in osteogenic differentiation of hADMSCs is found to be most dominant after 21–28 days of differentiation according to the calcification level of osteoblasts. These finding signify the importance of graphene size in controlling the osteogenesis of hADMSCs, which may shed new insight into the use of graphene-based materials for stem cell research and therapy.

Precise characterizations of stem cell differentiation into specific lineages, especially in non-destructive and non-invasive manner, are extremely important for generating patient-specific cells without mass loss of differentiated cells. Here, we report a new method capable of in situ label-free quantification of stem cell differentiation into multiple lineages, even at a single cell level. The human adipose-derived mesenchymal stem cells (hADMSCs) were first differentiated into two different types of cells (osteoblasts and adipocytes) and these differentiated cells were then intensively analyzed by micro-Raman spectroscopy. Interestingly, the Raman peaks assigned to lipid droplets and hydroxyapatite were found to be highly specific to the adipocyte (fat cell) and osteoblast (bone cell) and were thus found to be useful for generating label-free single cell Raman images in combination with CH3 (2935 cm-1) peaks for visualizing cell shape. Remarkably, based on these Raman images, we found that the osteogenesis of hADMSCs could be determined and quantified after 9 days of differentiation, which is a week earlier than with the typical alizarin red staining method. In the case of adipogenesis, the increase of lipid droplets in the cytoplasm at the single cell level could be clearly visualized and detected during the entire period of adipogenesis, which is impossible using any other currently available methods such as Oil Red O and immunostaining. Hence, the new method reported in this study is highly promising as an analytical tool for precise in-situ monitoring of stem cell differentiation, and could facilitate the use of stem cell-based materials for the regenerative therapies.

Graphene derivatives are highly promising materials for use in stem-cell-based regenerative therapies, particularly for bone regeneration. Herein, we report a graphene oxide (GO)-based hybrid platform (GOHP) that is highly effective for guiding the osteogenesis of human adipose-derived mesenchymal stem cells (hAMSCs). A GO-coated indium tin oxide (ITO) substrate was electrochemically modified with Au nanostructures (GNSs), following which a cysteine-modified quadruple-branched arginine-glycine-aspartic acid was self-assembled on the ITO-GO-GNS hybrid via Au-S bonds. The synthesized GOHP, with the highest density of GNSs (deposition time of 120 s), exhibited the highest osteogenic differentiation efficiency based on the osteogenic marker expression level, osteocalcin expression, and osteoblastic mineralisation. Remarkably, although GO is known to be less efficient than the high-quality pure graphene synthesised via chemical vapour deposition (CVD), the fabricated GOHP exhibited an efficiency similar to that of CVD-grown graphene in guiding the osteogenesis of hAMSCs. The total RNA sequencing results revealed that CVD graphene and GOHP induced the osteogenesis of hAMSCs by upregulating the transcription factors related to direct osteogenesis, Wnt activation, and extracellular matrix deposition. Considering that GO is easy to produce, cost-effective, and biocompatible, the developed GOHP is highly promising for treating various diseases/disorders, including osteoporosis, rickets, and osteogenesis imperfecta.

Graphene, a typical two-dimensional (2D) material, is known to affect a variety of stem cell behaviors including adhesion, spreading, growth, and differentiation. Here, we report for the first time the effects of four different emerging 2D materials on human adipose-derived mesenchymal stem cells (hADMSCs). Graphene oxide (GO), molybdenum sulfide (MoS2), tungsten sulfide (WS2), and boron nitride (BN) were selected as model two-dimensional materials and were coated on cell-culture substrates by a drop-casting method. Acute toxicity was not observed with any of the four different 2D materials at a low concentration range (

The concentration of sulfate ions was continuously monitored by Raman spectroscopy during the preparation of cathode material precursors. The obtained spectra were used for the quantitative analysis of sulfate ions by comparison with a reference solution, and a gradual increase of sulfate ion concentration was detected. Using a mathematical approach, a time-dependent equation describing sulfate ion concentration was theoretically derived, and the calculated concentrations were compared with the measured ones, showing good agreement between these values. Due to the increased sulfate ion concentration, the metal hydroxide cathode precursor became more contaminated with elemental sulfur. Two as-obtained hydroxide powders with different sulfur impurity contents were calcined with a lithium source, producing cathode materials. Electrochemical analysis of the prepared cathode materials showed that morphological aspects (such as particle size) more highly affected the cathode performance more than the sulfur impurity content.

Stem cell-based therapies have recently emerged to treat various incurable diseases and disorders. Types of stem cell-derived cells and their functions should be intensively analyzed before therapy. However, current pre-treatment steps for biological analysis are mostly destructive. Here, we report a novel optical method that enables ultra-fast and label-free characterization of cells, eliminating invasive, destructive steps. The technique, referred to as “autofluorescence-Raman mapping integration (ARMI)” analysis uses cell autofluorescence (AF) to reveal cellular morphology and cytosolic microstructures, while Raman mapping allows site-specific intensive analysis of target molecules, which enables ultra-fast identification of cell types. We used human mesenchymal stem cells (MSCs) as a model and induced adipogenesis. Lipid droplets in cells appeared as “blanks” in three-dimensional AF images and site-specific Raman mapping guided by AF identified the structure and components of the CH2 stretch. Adipogenesis could be rapidly and precisely analyzed, not only for the same batch but also for different batches. Therefore, the developed tool is highly useful for the accurate screening of stem cell differentiation and implementation in biomedical and clinical applications.

While Ga2O3 crystals are considered as the next generation optoelectronic materials, the exploration of HVPE α-Ga2O3 crystals and their use as solar-blind UV photodetector are still insufficient. In this paper, we investigated the structural characterization of HVPE α-Ga2O3 materials and their properties as solar-blind photodetector. HVPE α-Ga2O3 exhibited excellent structural properties with relatively good crystallinity, and smooth surface morphology, without any complicated process. Raman investigations confirmed the existence of slight compressive strain in the as-grown HVPE α-Ga2O3. UV–visible spectrophotometry proved that HVPE α-Ga2O3 had an optical bandgap of 5.15 eV, evidencing the suitability of this material for application as solar-blind photodetector. Furthermore, the photodetector synthesized using HVPE α-Ga2O3 showed excellent photo-response characteristics. We believe that this study will support further development of functional oxide semiconductor materials and opto-electronic devices.

This paper proposes novel nondisruptive in situ Raman spectroscopy analysis for gas evolution in commercial supercapacitor cells. To accelerate gas evolution, abusive aging tests were conducted during 21 days using commercial supercapacitor cells with a Raman setup. Changes in partial pressure were recorded using the Raman setup after the aging tests under various electrochemical analysis, such as cyclic voltammetry (CV), galvanostatic charge/discharge analysis, and impedance spectroscopy. The performance of the bare supercapacitor cell was evaluated and compared with that of the Raman cell. Difference of capacitance derived from CV was less than 1% until end of life of the cells. Moreover, resistance results obtained from galvanostatic charge/discharge differed below 8%. This analysis confirmed that the Raman cell was nondisruptive with a minute effect on the supercapacitor cell itself, indicating high reliability of in situ gas analysis of practical cells.

Bulk heterojunction (BHJ) films with nanopattern structure have been fabricated using a stamping transfer process with polyurethane acrylate (PUA) replica film based on 3-dimensional colloidal crystals. The uniformly arrayed nanostructure of the PUA film was investigated by SEM analysis. Compared to the organic photovoltaic cells wtih plain BHJ of poly(3-hexylthiophene-2,5-diyl) (P3HT) and indene-C60 bisadduct (ICBA), the device from the nanopatterned BHJ exhibit improved E-field distribution intensity, as assessed using a finite-difference time-domain (FDTD) method. The current density (J SC ) and power conversion efficiency (PCE) of the device were respectively increased by up to 27% and 20% due to the enhanced interfacial contact area and plasmonic effect, which can brought about effective light harvesting between the BHJ active layer and cathode. Through a simple low-temperature transfer process using a PUA mold, we can fabricate reproducible nanopatterned BHJ devices that have improved light absorption within the active layer of the devices.

Hexagonally ordered mesoporous carbon materials were prepared and used as electrode materials in an electric double-layer capacitor. Using this electrode, the change of electrolyte resistance within the mesopores was investigated according to the bulk electrolyte concentration. Using three different electrochemical transient experiments—imaginary capacitance analysis, chronoamperometry, and chronopotentiometry—the time constant associated with electrolyte transport was determined, which was then used to obtain the electrolyte resistance within the mesopores. With decreasing electrolyte concentration, the increase in electrolyte resistance was smaller than the increase in the resistivity of the bulk electrolyte, which is indicative of a different environment for ionic transport within the mesopores. On using the confinement effect within the mesopores, the predicted higher concentration within mesopore probably results in lower electrolyte resistance, especially under low bulk concentrations.

In the present study, a tungsten oxide–carbon nanocomposite (WOx–C) is synthesized and employed as the negative electrode in lithium-ion batteries. The prepared material exhibited an ordered mesoporous carbon structure uniformly embedded by tungsten oxide nanoparticles. Also, it is composed of about 90% highly reduced tungsten W5+ fraction. The conversion of WOx to W0 and Li2O is proven to be the major lithiation mechanism of WOx–C negative electrode. From electrochemical analysis, a distinct improvement in the delithiation resistance of tungsten oxide within the composite electrode is observed. This improvement in polarization is a result of the high electrical conductivity of the mesoporous carbon matrix and the uniform distribution of tungsten species. The lower delithiation polarization leads to a WOx-C electrode with very stable cycleability, which has been rarely observed in typical conversion-type negative electrodes.

Research on the 3D culturing of cancer cells that better mimic in vivo solid tumors is important for efficient drug screening. Herein, a new platform that effectively facilitates the formation of cancer spheroids for anticancer drug screening is reported. Cytophilic graphene oxide (GO), when selectively coated on the sidewalls of micro-wells fabricated from a cell-adhesion-resistive polymer, is found to efficiently initiates distinct donut-like formation of cancer cell spheroids. Scanning electron microscopy and Raman mapping are used to analyze vertically coated GO micropatterns (vGO-MPs) of different sizes (100-250 µm) on polymer platforms, and human liver cancer cells (HepG2), as a model cancer, are seeded on these platforms. Remarkably, the 150 µm-sized platform is found to easily and rapidly generate 3D spheroids in the absence of cell-adhesion proteins. In addition, owing to the unique characteristics of GO, vGO-MPs are highly stable for long periods of time (≈1 month), even under harsh conditions (>70 °C). Moreover, the anticancer effects of two drugs (hydroxyurea and cisplatin) and the potential anticancer compound (curcumin) on HepG2 cells are demonstrated by simply measuring decreases in spheroid sizes. Hence, this new platform is highly promising as a cancer spheroid-forming material for rapid drug screening.

This study focuses on a novel approach for the structural design of LiNi0.86Co0.12Al0.02O2 cathodes by tailoring the distribution of Al elements using milled-Al(OH)3. The distribution of Al in the cathode material is investigated using an electron probe micro analyzer. By controlling milled-Al(OH)3 addition time at 3 and 6 h, thickness of Al-rich layer is varied during co-precipitation process and following calcination with LiOH produces cathode materials with the variant Al distribution. Initial discharge capacities of the cathodes with the Al addition at 3 and 6 h are 202 and 195 mA h g−1 and the IE (initial efficiency) is 92.5 and 86.6%, respectively. The capacity retentions from the cycling test of the individual cathodes are as high as 96.7 and 92.6% at 50 cycles under 1 C rate, respectively. This advanced electrochemical performance is attributed to gradual increase of Al element from inner to outer in active material.