Search

Anti-interference characteristics, whereby undesirable signal interference is minimized, are required for multifunctional sensor platforms. In this study, an anti-temperature-interference resistive-type strain sensor, which does not respond to temperature but only to strain, is designed. Anti-interference properties were achieved by modulating the temperature coefficient of resistance (TCR) of metal nanoparticles (NPs) through hybrid chemical treatment with organic and halide ligands that induce negative and positive TCRs, respectively. Consequently, a very low TCR of 1.9 × 10

Next-generation devices and systems require the development and integration of advanced materials, the realization of which inevitably requires two separate processes: property engineering and patterning. Here, we report a one-step, ink-lithography technique to pattern and engineer the properties of thin films of colloidal nanocrystals that exploits their chemically addressable surface. Colloidal nanocrystals are deposited by solution-based methods to form thin films and a local chemical treatment is applied using an ink-printing technique to simultaneously modify (i) the chemical nature of the nanocrystal surface to allow thin-film patterning and (ii) the physical electronic, optical, thermal, and mechanical properties of the nanocrystal thin films. The ink-lithography technique is applied to the library of colloidal nanocrystals to engineer thin films of metals, semiconductors, and insulators on both rigid and flexible substrates and demonstrate their application in high-resolution image replications, anticounterfeit devices, multicolor filters, thin-film transistors and circuits, photoconductors, and wearable multisensors.

In this study, non-temperature interference strain gauge sensors, which are only sensitive to strain but not temperature, are developed by engineering the properties and structure from a material perspective. The environmental interference from temperature fluctuations is successfully eliminated by controlling the charge transport in nanoparticles with thermally expandable polymer substrates. Notably, the negative temperature coefficient of resistance (TCR), which originates from the hopping transport in nanoparticle arrays, is compensated by the positive TCR of the effective surface thermal expansion with anchoring effects. This strategy successfully controls the TCR from negative to positive. A near-zero TCR (NZTCR), less than 1.0 × 10-6 K-1, is achieved through precisely controlled expansion. Various characterization methods and finite element and transport simulations are conducted to investigate the correlated electrical, mechanical, and thermal properties of the materials and elucidate the compensated NZTCR mechanism. With this strategy, an all-solution-processed, transparent, highly sensitive, and noninterference strain sensor is fabricated with a gauge factor higher than 5000 at 1% strain, as demonstrated by pulse and motion sensing, as well as the noninterference property under variable-temperature conditions. It is envisaged that the sensor developed herein is applicable to multifunctional wearable sensors or e-skins for artificial skin or robots.

In this study, a self-sorting sensor was developed with the ability to distinguish between different pressure regimes and translate the pressure to electrical signals. Specifically, the self-sorting sensor can distinguish between soft and hard pressure like the human skin, without any software assistance and complicated circuits. To achieve the self-sorting property, Janus-like jagged structures were prepared via an all-solution process of spontaneous chemical patterning; they comprised electrically semi-insulating vertices and highly conductive valleys. This unique structure facilitates the detection and determination of the intensities and types of pressure by providing a significant gap between the current levels of two types of states, similar to the function of fibers in the human tactile system. The fabricated sensors also exhibit high sensitivity and durability as well as low power consumption, as demonstrated by the electronic skin and ternary Morse signal applications. Compared with conventional wearable pressure sensors, this sensor can detect signals without additional programming; thus, it is highly suitable for delay-sensitive, energy-efficient sensor applications such as driverless vehicles, autonomous artificial intelligence technology, and prosthetic devices.

In this study, multifunctional light-emitting and passive radiative cooling (LEPC) materials and devices are designed by embedding chemically designed perovskite nanocrystals (NCs) into the radiative polymer layer. Lead halide perovskite NCs are chosen as the light-emitting material, owing to their high photon radiation rate and low phonon generation. To integrate the perovskite NCs into the radiative polymer layers, a surface passivation is achieved by coating the NCs with silica. The silica shell synergistically improves the chemical stability and cooling efficiency. Both outdoor experimental and simulation results demonstrate that the fabricated LEPC devices show better cooling performance than conventional cooling devices. The LEPC devices are easily patterned by utilizing pixelating, assembling, and simple cutting or drawing techniques with the LEPC materials. This study also demonstrates the potential applications of these materials as components of smart building systems, in smart window displays, or for anticounterfeiting cooling systems, thus proving the practicality of these multifunctional LEPC devices.

This study represents the heating-up synthesis of lead-free cesium bismuth bromide perovskite nanocrystals (NCs). CsBr and BiBr3 precursors are used to synthesize uniform and phase-pure cesium bismuth bromide NCs, and the reaction is performed via an injection-free, heating-up method in the presence of a solvent mixture with a high boiling point. The size and composition of cesium bismuth bromide NCs are readily controlled by changing the reaction time, temperature, and amount of surfactant added to the reaction mixture. Upon heating, sequential phase evolution occurs, resulting in the formation of kinetically stable BiOBr in the early reaction stages, which transformed into the thermodynamically stable Cs3BiBr6 and Cs3Bi2Br9 with an increase in either the reaction time or the reaction temperature. Furthermore, the absorption and photoluminescence properties of Cs3BiBr6 and Cs3Bi2Br9 NCs are characterized to investigate their composition-dependent optical properties. This work provides the potential to synthesize various types of lead-free perovskite NCs by tailoring the size and compositions.

Post-synthesis engineering methods that employ oriented attachment to precisely control the size and dimensionality (0D/1D/2D) of as-synthesized CsPbBr3 nanocrystals (NCs) are demonstrated. We investigated the chemical effects of the properties of polar solvents, including their immiscibility, polarity, and boiling point, on the surfaces of NCs, as well as their effect on the structural and optical properties of NCs. Appropriate exploitation of the solvent properties made it possible to use a polar solvent to mildly affect the NCs indirectly such that they discarded their ligands and became attached to proximal NCs without being destroyed. Based on our observations, we developed a method whereby a solution of the NCs in a non-polar solvent is mixed with a polar solvent to form an immiscible phase to induce epitaxial growth of CsPbBr3 NCs. The method enables the size of NCs to be easily regulated from 5 to 50 nm by controlling the engineering time. Taking advantage of the minimal effect of a mild solvent, we also developed a self-assembly method that operates at the liquid–air interface to systematically control the dimensionality. At this interface, the NCs self-assemble in the horizontal direction and grow into micron-sized, single-crystalline, defect-free nanowires (1D) and nanoplates (2D) via oriented attachment. Finally, we discuss the origin of the non-destructive oriented attachment phenomenon and the surface chemistry of a perovskite NC using density functional theory (DFT) simulations and a proposed model system.

We report a simple, solution-based, and postsynthetic process for simultaneous ligand exchange, surface passivation, and doping of CdSe nanocrystals (NCs) for the design of high-performance field-e...

The structure of global wine consumption is changing from traditional concerns with color, taste, alcohol contents, brand, etc. to low alcohol, well-being, convenience, price, and others caused by social activities of woman and increase in one-person households, etc. We focus the wine market of the Republic of Korea because wine consumption trend in Korea is changing toward multiple directions. The purpose of this study is to segment wine market considering new consumption trend and find out the characteristics of target market(s). Three hundred thirty-eight Korean wine consumers were surveyed using questionnaire survey method. The research identifies five clusters of wine consumers: low-involvement type, epicure type, cost-effectiveness type, outside perspective type, and health-based type. Among them, cost-effectiveness type and health-based type accorded with new consumption trend are selected as target markets. The two target markets show different characteristics. It is expected that wineries or wine marketers could consider the profile of target markets when they produce or promote wine products related with cost-effectiveness and health benefits.

We investigated the chemical effects of halide ligands on the electromechanical properties of Ag nanocrystal (NC) thin films for potential uses in wearable devices and sensors. The halide treatment...

In this study, we introduce a strategy to introduce solution-processed interfacial layers in nanocrystal (NC) thin films to fabricate high-performance strain sensors. SiO2 interfacial layers are chemically introduced in ligand-exchanged Ag NC thin films to increase the tunneling gap or inter-particle distance between each Ag NC. In this way, the charge-transport mechanism is manipulated, leading to unique electromechanical properties with a high gauge factor. All solution-processed strain gauge sensors with high stability, durability, and sensitivity are fabricated. The sensor successfully measured delicate movements such as finger motions, demonstrating its possible application in electronic skin.

Ligand exchange processes have been attracting tremendous interest and are necessary when fabricating nanocrystal (NC) thin films for various applications. As ligand exchange processes are based on...

Highly transparent and sensitive pressure sensors with a wide detection range were developed by a simple process using silver nanowires and ZnO nanocrystals (NCs) without lithography. The open mesh structured spacers were sucessfully designed by one-step chemical treatment involving a ligand exchange process on the ZnO NC thin films, leading to improved sensitivity, responsivity and transparency. The device performance analyses along with chemical, structural, and electronic characterization studies reveal that the chemically designed pressure sensor has a record-breaking sensitivity of 3.23 × 103 kPa−1, a large detection range of up to 75 kPa, excellent reliability, and high transparency of 85% in the visible-light region. The origin of improved sensitivity was explained with the contact area variation theory. We also demonstrate that the pressure sensor fabricated by the all-solution-based facile process can be employed in various applications such as wearable sensors for measurement of the human pulse and attachable electronics for an electronic skin with a wide sensing range of pressures.

Post-synthesis engineering methods that employ oriented attachment to precisely control the size and dimensionality (0D/1D/2D) of as-synthesized CsPbBr

Daytime radiative cooling is an eco-friendly, temperature-cooling mechanism that uses the inherent properties of a material without energy consumption. To realize a high daytime radiative cooling ability, it is necessary to minimize light absorption in the solar spectrum (0.3–2.5 μm) and maximize the emissivity in the atmospheric transmittance window (8–13 μm). Currently, the solar reflective layer of a radiative cooling material has the limitation of absorbing UV light, which can reduce the cooling performance. We attempted to solve this problem via UV-to-visible wavelength conversion using CdSe/ZnS giant core-shell structures. By applying this strategy, a wavelength conversion-type radiative cooling emitter (WC-RCE) was fabricated using “giant” CdSe/ZnS core-shell nanocrystals embedded into a polymeric membrane to establish minimized absorption within the UV and short-visible regions, which constitute up to 17.28% of the total solar spectrum. The applied g-NCs have a high photoluminescence quantum yield and a large Stokes shift, and can resolve the absorption in reflective layers, such as silver, by re-emitting the wavelength of the absorbed UV rays into the visible region. Compared with a conventional RCE, the WC-RCE achieves further cooling by 0.38 °C on average from outdoor measurements. Thus, a wavelength conversion strategy was confirmed for efficient daytime radiative cooling.

In this study, a highly stretchable white-light electroluminescent device is fabricated using chemically designed perovskite nanocrystals (NCs). To incorporate perovskite into a stretchable polymer matrix without any degradation, gel-type silica-coated CsPbBr3 and CsPbBrxI3-x NC inks are prepared using (3-aminopropyl) triethoxysilane (APTES) with a sacrificial solvent of hexane. The chemical, optical, and structural properties of powdered and gel-type perovskite NCs with and without APTES are investigated. Silica shell with APTES treatment improves the stability of perovskite NCs, and gel-type inks improve the dispersivity in the polymer matrix. These enable the fabrication of stretchable and luminescent NC/polymer matrices with enhanced and uniform luminescence properties. By utilizing these materials, we propose a stretchable electroluminescent device emitting strong white light that is close to the ideal white position in Commission Internationale de l'eclairage (CIE) with optical simulation. Herein, we fabricate a multi-color filter with high color reproducibility on stretchable blue electroluminescent devices for white-light generation. Furthermore, all-solution-processed, color-filterless, stretchable, white-light electroluminescence devices with excellent optical and mechanical properties are fabricated.

The effects of halide-ligand exchange and Cu and Ag doping are studied on structural, optical, and electrical properties of four monolayer CdSe nanoplatelet (NPL) and NPL thin films. Combinational study shows that NH4Cl-treatment on CdSe NPL and NPL thin films show tetragonal lattice distortion of NPL, side-to-side attachment between NPLs, bathochromic shift in absorption spectra, and complete quenching of band-edge and dopant-induced emissions. First-principle calculations reveal that Cl creates states below valence band maximum while Ag and Cu dopants create acceptor-like states, explaining the change of their optical property. Field-effect transistors are fabricated to investigate the effect of doping and reduced interplatelet distance on electrical properties of CdSe NPL thin films, demonstrating Cu and Ag dopants mitigate n-type character of CdSe NPL thin films. Temperature-dependent electrical characterization is conducted to further understand charge transport behavior depending on the existence of dopants. This work provides scientific information on the influence of surface chemistry and impurity doping on quantum confined semiconductors and new directions for the design of high-performance nanomaterial-based electronic and optoelectronic devices. Ministry of Education (MOE) National Research Foundation (NRF) Accepted version The authors would like to acknowledge the financial support from Singapore National Research Foundation under the Program of NRF-NRFI2016-08, the Competitive Research Program NRF-CRP14-2014-03, and Singapore Ministry of Education Tier 1 grant (MOE-RG62/20). The authors acknowledge the financial support from National Science Foundation the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (2019R1C1C1003319), Creative Materials Discovery Program through the National Research Foundation of Korea (NRF) funded by Ministry of Science, ICT and Future Planning (NRF-2018M3D1A1059001), and Korea University Future Research Grant. H.V.D. also acknowledges support from TUBA. Y.G.K. and M.J.H. were supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (2021R1A2C1009303).

The popularity of colloidal quantum dot (CQD) solar cells has increased owing to their tunable bandgap, multiple exciton generation, and low-cost solution processes. ZnO nanoparticle (NP) layers are generally employed as electron transport layers in CQD solar cells to efficiently extract the electrons. However, trap sites and the unfavorable band structure of the as-synthesized ZnO NPs have hindered their potential performance. Herein, we introduce a facile method of ZnO NP annealing in the colloidal state. Electrical, structural, and optical analyses demonstrated that the colloidal-annealing of ZnO NPs effectively passivated the defects and simultaneously shifted their band diagram; therefore, colloidal-annealing is a more favorable method as compared to conventional film-annealing. These CQD solar cells based on colloidal-annealed ZnO NPs exhibited efficient charge extraction, reduced recombination and achieved an enhanced power conversion efficiency (PCE) of 9.29%, whereas the CQD solar cells based on ZnO NPs without annealing had a PCE of 8.05%. Moreover, the CQD solar cells using colloidal-annealed ZnO NPs exhibited an improved air stability with 98% retention after 120 days, as compared to that of CQD solar cells using non-annealed ZnO NPs with 84% retention.

Herein, we introduce a unique nanomaterial chemical transformation (NCT) process whereby selenium (Se) anion is introduced to colloidal silver (Ag) nanocrystals (NCs) to create nanostructured silver selenide (Ag2Se). We present a complete suite of material characterizations, including chemical, structural, optical, and electrical characterizations to understand the details of the transformation process. The Ag2Se thin-films obtained through the NCT process exhibit degenerately-doped n-type semiconductor characteristics with high carrier mobility. We discuss the chemical mechanism that drives the material transformation and elucidates the origin of doping in these semiconducting thin-films. We also demonstrate the robustness of Ag2Se thin-films toward mechanical strain and temperature cycling stress for flexible device applications. We believed that the NCT process demonstrated here is of wide applicability to other material systems which can open up new avenues for solid-state chemistry and device engineering research.

Lhx8 (LIM homeobox 8) gene encodes a LIM homeodomain transcriptional regulator that is preferentially expressed in germ cells and critical for mammalian folliculogenesis. However, Lhx8 DNA binding sequences are not characterized yet. We aimed to identify and characterize a cis-acting sequence of germ-cell specific transcriptional factor, Lhx8. To identify Lhx8 DNA binding element, Cyclic Amplification of Sequence Target (CAST) Analysis was performed. Electrophoretic Mobility Shift Assay (EMSA) was processed for the binding specificity of Lhx8. Luciferase assay was for the transcriptional activity of Lhx8 through identified DNA binding site. We identified a putative cis-acting sequence, TGATTG as Lhx8 DNA binding element (LBE). In addition, Lhx8 binds to the LBE with high affinity and augments transcriptional activity of luciferase reporter driven by artificial promoter containing the Lhx8 binding element. These findings indicate that Lhx8 directly regulates the transcription of genes containing Lhx8 binding element in oocytes during early folliculogenesis.

LHX8 (LIM homeobox 8) is a germ cell-specific transcription factor that is crucial for folliculogenesis in the ovary and represents a candidate gene for premature ovarian insufficiency. We analyzed whether mutations in the LHX8 gene in 96 Korean women with premature ovarian insufficiency. The sequence analysis identified four known SNPs included one synonymous and three intronic variants and discovered three novel single-nucleotide polymorphisms in intron 4 (c.114+99C>A), intron 4 (c.114+100C>A) and intron 6 (c.390+77C>G) of the LHX8 gene. These polymorphisms were also found in controls at frequencies that were not statistically significant. Functional mutations in LHX8 gene are rare in Korean women with premature ovarian insufficiency.

Nobox is an oocyte-specific transcriptional regulator. Nobox deficiency disrupts early folliculogenesis and the expression of oocyte-specific genes in mice. In the present study, we found that peptidylarginine deiminase 6 (Pad6) was downregulated in Nobox-null ovaries. Pad6 is preferentially expressed in oocytes and its transcript is detectable at embryonic day 16.5. In addition, we identified one Nobox DNA-binding element (NBE) within the mouse Pad6 promoter. The NBE includes a core sequence TAATTA. Sequence-specific binding of Nobox to the TAATTA motif was confirmed. Nobox overexpression augmented transcriptional activity of a luciferase reporter driven by mouse Pad6. Our findings indicate that Nobox is a critical regulator that orchestrates oocyte-specific genes such as Pad6 during folliculogenesis.

In a previous study, we found SOHLH1 (spermatogenesis and oogenesis-specific basic helix-loop-helix 1) as the first testis-specific basic helix-loop-helix transcription factor essential for spermatogonial differentiation. SOHLH1 therefore represents an excellent candidate gene for testicular failure such as nonobstructive azoospermia (NOA). We analyzed whether there were mutations in the SOHLH1 gene in 96 Korean patients with NOA. The sequence analysis discovered three novel variations: one intronic variant (c.346-1GA), and two nonsynonymous exonic variants (c.91TC and c.529CA) with known single nucleotide polymorphisms (SNPs), which included six intronic variants, two synonymous, and two nonsynonymous variants. We examined the consequences of mutations in SOHLH1 using in vivo and in vitro assays. Analysis of transcripts from minigenes carrying the c.346-1GA revealed that splicing site variation leads to the partial deletion at a cryptic splicing site within exon 4. This deletion results in SOHLH1 with a truncated bHLH domain. Transient transfection assay showed that the SOHLH1 mutant with the truncated domain disrupted the transcriptional activity of KIT promoter, whereas two missense mutations harboring either p.Arg37Gln or p.Pro269Ser did not have a significant effect on its transactivation. Our findings indicate that a splice-acceptor site mutation that probably causes a nonfunctional SOHLH1 protein results in nonobstructive azoospermia by the lack of normal spermatogenesis.

CONceptual-BAsed image retrieval system (CONBA) supports the object recognition and retrieval based on object modeling and machine learning. The system, being independent of a domain, has an advantage in that the probability of the image recognition and the retrieval would be improved on the basis of a continuous learning theory of the image object. This system also includes a design for supporting a conceptual object on the basis of the set-based theory to extract the conceptual object and support it in user's enquires.

Department of Biomedical Science, CHA University, Seoul 135-081, Republic of Korea b Fertility Center of Gangnam Medical Center, Department of Obstetrics and Gynecology, CHA University, Seoul 135-081, Republic of Korea c Severance Hospital Integrative Research Institute for Cerebral & Cardiovascular Disease, Yonsei University Health System, Seoul 120-752, Republic of Korea Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, Pittsburgh, PA 15213, USA