Publications by authors named "Minjae Choi"

In this study, nonvolatile bipolar resistive switching and synaptic emulation behaviors are performed in an InGaP quantum dots (QDs)/HfO-based memristor device. First, the physical and chemical properties of InGaP QDs are investigated by high-resolution transmission electron microscopy and spectrophotometric analysis. Through comparative experiments, it is proven that the HfO layer improves the variations in resistive switching characteristics.

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Article Synopsis
  • GaP, a semiconductor commonly used in optoelectronics, is limited by its indirect bandgap which affects efficiency.
  • Researchers demonstrated that creating quantum shells on ZnS nanocrystals can transition GaP from an indirect to a direct bandgap, resulting in a high photoluminescence quantum yield of 45.4% at 409 nm.
  • This work suggests that using ZnS as a growth platform for GaP can enable the formation of direct bandgaps in other materials, potentially enhancing the efficiency of optoelectronic devices and solar cells.
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Hydrogen peroxide (HO) is a high-demand chemical, valued as a powerful and eco-friendly oxidant for various industrial applications. The traditional industrial method for producing HO, known as the anthraquinone process, is both costly and environmentally problematic. Electrochemical synthesis, which produces HO using electricity, offers a sustainable alternative, particularly suited for small-scale, continuous on-site HO generation due to the portability of electrocatalytic devices.

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Three-dimensional optical nanostructures have garnered significant interest in photonics due to their extraordinary capabilities to manipulate the amplitude, phase, and polarization states of light. However, achieving complex three-dimensional optical nanostructures with bottom-up fabrication has remained challenging, despite its nanoscale precision and cost-effectiveness, mainly due to inherent limitations in structural controllability. Here, we report the optical characteristics of intricate two- and three-dimensional nanoarchitectures made of colloidal quantum dots fabricated with multi-dimensional transfer printing.

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Quantum dots (QDs), a novel category of semiconductor materials, exhibit extraordinary capabilities in tuning optical characteristics. Their emergence in biophotonics has been noteworthy, particularly in bio-imaging, biosensing, and theranostics applications. Although conventional QDs such as PbS, CdSe, CdS, and HgTe have garnered attention for their promising features, the presence of heavy metals in these QDs poses significant challenges for biological use.

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Indium phosphide (InP) quantum dots (QDs) have attracted significant interest as next-generation light-emitting materials. However, the synthesis of blue-emitting InP-based QDs has lagged behind that of established green- and red-emitting InP QDs. Herein, we present a strategy to synthesize blue-emitting QDs by forming an InGaP alloy composition.

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Background: It is well-known that socioeconomic status is associated with mental illness at both the individual and population levels, but there is a less clear understanding of whether socioeconomic development is related to poor mental health at the country level.

Aims: We aimed to investigate sociodemographic disparities in burden of mental disorders, substance use disorders and self-harm by age group.

Method: Estimates of age-specific disability-adjusted life years (DALY) rates for mental disorders, substance use disorders and self-harm from 1990 to 2019 for 204 countries were obtained.

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Photothermal therapy (PTT) holds great promise as a cancer treatment modality by generating localized heat at the tumor site. Among various photothermal agents, gallium-based liquid metal (LM) has been widely used as a new photothermal-inducible metallic compound due to its structural transformability. To overcome limitations of random aggregation and dissipation of administrated LM particles into a human body, we developed LM-containing injectable composite hydrogel platforms capable of achieving spatiotemporal PTT and chemotherapy.

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Objectives: This study aimed to examine changes in life expectancy (LE), health-adjusted life expectancy (HALE), unhealthy years of life, and disease burden of older people in industrialised countries and associations with health systems.

Methods: We used estimates of LE and HALE, unhealthy years of life, years of life loss (YLL), years lived with disability (YLD) for individuals aged 70 years and over in 33 industrialised countries from 1990 to 2019 from the Global Burden of Disease Study 2019. A linear regression analysis was conducted to examine the association of health outcomes with the Healthcare Access and Quality (HAQ) index.

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This study presents the development of a β-hairpin (tryptophan zipper, Trpzip)-based molecular tweezer (MT) that can control the folding and binding of α-helical peptides. When an α-helix isolated from the p53 protein was conjugated with Trpzip in an optimized macrocyclic structure, the folded β-hairpin stabilized the helix conformation through the side chain-to-side chain stapling strategy, which notably enhanced target (hDM2) affinity of the peptide. On the other hand, the helicity and binding affinity were significantly reduced when the hairpin was unfolded by a redox stimulus.

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Even with a reduced burden of malaria in sub-Saharan Africa (SSA), differences remain in the rate of change among countries and sub-regions. We used data from the Global Burden of Disease Study 2019 to establish the relationship between Development Assistance for Health (DAH) and governance and trends in malaria burden in SSA. The trend was estimated using the Joinpoint regression program and the Institute of Health Metrics and Evaluation's DAH database, and World Bank Governance Indicators to analyze the DAH and governance respectively from 2000 to 2017 and used two-way fixed effects to establish their association with the trend in the period.

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Background: Life expectancy gaps between North and South Korea have increased but contributions to these gaps remain poorly understood. Using data from the Global Burden of Disease Study (GBD) 2019, we examined how much death from specific diseases contributed to these gaps in different age groups over three decades.

Methods: Data for death numbers and population by sex and 5-year age groups in both North and South Korea from 1990 to 2019 were extracted from the GBD 2019 to calculate life expectancy.

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To investigate the trend of healthcare needs among elders in low-income countries (LICs) and how changes in healthcare access and quality (HAQ) have correlated with these changes from 1990 to 2019, this study used estimates from the global burden of disease (GBD) 2019 study, including prevalence, years of life lost (YLLs), years lived with disability (YLDs), life expectancy (LE), health-adjusted life expectancy (HALE) and the HAQ index for years 1990 and 2019. We found increases in numbers of YLLs, YLDs, and prevalent cases due to NCDs, and the rate of increase was higher for all indicators of non-communicable diseases (NCDs) when compared with communicable, maternal, neonatal and nutritional diseases among elders. We also observed increases in LE and HALE among all countries.

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III-V colloidal quantum dots (CQDs) are promising materials for optoelectronic applications, for they avoid heavy metals while achieving absorption spanning the visible to the infrared (IR). However, the covalent nature of III-V CQDs requires the development of new passivation strategies to fabricate conductive CQD solids for optoelectronics: this work shows herein that ligand exchanges, previously developed in II-VI and IV-VI quantum dots and employing a single ligand, do not fully passivate CQDs, and that this curtails device efficiency. Guided by density functional theory (DFT) simulations, this work develops a co-passivation strategy to fabricate indium arsenide CQD photodetectors, an approach that employs the combination of X-type methyl ammonium acetate (MaAc) and Z-type ligands InBr .

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Quantum dots have attracted significant scientific interest owing to their optoelectronic properties, which are distinct from their bulk counterparts. In order to fully utilize quantum dots for next generation devices with advanced functionalities, it is important to fabricate quantum dot colloids into dry patterns with desired feature sizes and shapes with respect to target applications. In this review, recent progress in ultrahigh-resolution quantum dot patterning technologies will be discussed, with emphasis on the characteristic advantages as well as the limitations of diverse technologies.

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Objective: Financial hardship influences depression risk, however, the pathway of the effect of financial hardship on depression and the role of self-esteem remain unclear. This study examined whether changes in financial hardship affected depression, and whether self-esteem mediated by this relationship.

Methods: Data from 99,588 observations of 15,331 individuals were extracted from 10 waves of the Korean Welfare Panel Study.

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Background: Evidence for the trends and patterns of disease burden in North Korea is limited, and in-depth analysis based on several health outcomes for a better understanding remains challenging. Therefore, we aimed to investigate the trends and patterns of disease burden in North Korea between 1990 and 2019.

Methods: We used data from the Global Burden of Diseases (GBD) 2019 study to analyze the North Korean disease burden in comparison with four groups: global, South Korea, low-sociodemographic index (SDI) countries, Central and Eastern Europe, and Central Asia (former socialist countries).

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Indium phosphide (InP) colloidal quantum dots (CQDs) have generated great interest as next-generation light-emitting materials owing to their narrow emission spectra and environment-friendly components. The minimized surface defects is essential to achieve narrow full-width at half-maximum (FWHM) and high photoluminescence quantum yield (PLQY). However, InP CQDs are readily oxidized in ambient condition, which results in formation of oxidation defect states on the surface of InP CQDs.

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