Chronic kidney disease in postmenopausal women is associated with tooth loss.

OBJECTIVE: Menopause is characterized by changes in reproductive hormone levels that can negatively affect bone. Chronic kidney disease (CKD) and tooth loss are also important and common health issues after menopause. This study aimed to evaluate the association between CKD and tooth loss in postmenopausal women. METHODS: The study evaluated 64,971 participants who participated in the Korean National Health and Nutrition Examination Survey (KNHANES) from 2010-2018, including postmenopausal women, aged 40 to 79 years. Participants were divided into two groups based on the number of teeth in their dentition (≥20 and <20). MAIN OUTCOME MEASURES: The association between CKD and tooth loss was analyzed using multivariate logistic regression. Age, income, education, smoking, alcohol intake, body mass index, hypertension, diabetes, annual oral examination, toothbrushing, and the use of oral care products were considered. Subgroup analyses were further conducted according to age (40-65 yr and 66-79 yr). RESULTS: After adjusting for covariates, CKD and estimated glomerular filtration rate were significantly associated with having ≥20 teeth (PT20; CKD: odds ratio [OR] 1.41, 95% confidence interval [CI] 1.04-1.90; estimated glomerular filtration rate (10 mL/min/1.73 m2): OR 0.90, 95% CI 0.86-0.94). Importantly, the association between CKD and PT20 was significant in postmenopausal women, aged 66 to 79 years (OR 1.45, 95% CI 1.05-2.01). CONCLUSIONS: In postmenopausal women, CKD and tooth loss may be associated. The association is significant in postmenopausal women, aged 66 to 79 years.

Development and evaluation of a multiplex real-time RT-PCR assay for simultaneous detection of H5, H7, and H9 subtype avian influenza viruses.

H5, H7 and H9 are the major subtypes of avian influenza virus (AIV) that cause economic losses in the poultry industry and sporadic zoonotic infection. Early detection of AIV is essential for preventing disease spread. Therefore, molecular diagnosis and subtyping of AIV via real-time RT-PCR (rRT-PCR) is preferred over other classical diagnostic methods, such as egg inoculation, RT-PCR and HI test, due to its high sensitivity, specificity and convenience. The singleplex rRT-PCRs for the Matrix, H5 and H7 gene used for the national surveillance program in Korea have been developed in 2017; however, these methods were not designed for multiplexing, and does not reflect the sequences of currently circulating strains completely. In this study, the multiplex H5/7/9 rRT-PCR assay was developed with sets of primers and probe updated or newly designed to simultaneously detect the H5, H7 and H9 genes. Multiplex H5/7/9 rRT-PCR showed 100% specificity without cross-reactivity with other subtypes of AIVs and avian disease-causing viruses or bacteria, and the limit of detection was 1-10 EID50/0.1 ml (50% egg infectious dose). Artificial mixed infections with the three different subtypes could be detected accurately with high analytical sensitivity even under highly biased relative molecular ratios by balancing the reactivities of each subtype by modifying the concentration of the primers and probes. The multiplex H5/7/9 rRT-PCR assay developed in this study could be a useful tool for large-scale surveillance programs for viral detection as well as subtyping due to its high specificity, sensitivity and robustness in discriminating viruses in mixed infections, and this approach would greatly decrease the time, cost, effort and chance of cross-contamination compared to the conventional method of testing three subtypes by different singleplex rRT-PCR methods in parallel or in series.

Optically Triggered Emergent Mesostructures in Monolayer WS2.

The ultrahigh surface area of two-dimensional materials can drive multimodal coupling between optical, electrical, and mechanical properties that leads to emergent dynamical responses not possible in three-dimensional systems. We observed that optical excitation of the WS2 monolayer above the exciton energy creates symmetrically patterned mechanical protrusions which can be controlled by laser intensity and wavelength. This observed photostrictive behavior is attributed to lattice expansion due to the formation of polarons, which are charge carriers dressed by lattice vibrations. Scanning Kelvin probe force microscopy measurements and density functional theory calculations reveal unconventional charge transport properties such as the spatially and optical intensity-dependent conversion in the WS2 monolayer from apparent n- to p-type and the subsequent formation of effective p-n junctions at the boundaries between regions with different defect densities. The strong opto-electrical-mechanical coupling in the WS2 monolayer reveals previously unexplored properties, which can lead to new applications in optically driven ultrathin microactuators.

Multichannel Hierarchical Analysis of Time-Resolved Hyperspectral Data for Advanced Colorimetric E-Nose.

The colorimetric sensor-based electronic nose has been demonstrated to discriminate specific gaseous molecules for various applications, including health or environmental monitoring. However, conventional colorimetric sensor systems rely on RGB sensors, which cannot capture the complete spectral response of the system. This limitation can degrade the performance of machine learning analysis, leading to inaccurate identification of chemicals with similar functional groups. Here, we propose a novel time-resolved hyperspectral (TRH) data set from colorimetric array sensors consisting of 1D spatial, 1D spectral, and 1D temporal axes, which enables hierarchical analysis of multichannel 2D spectrograms via a convolution neural network (CNN). We assessed the outstanding classification performance of the TRH data set compared to an RGB data set by conducting a relative humidity (RH) concentration classification. The time-dependent spectral response of the colorimetric sensor was measured and trained as a CNN model using TRH and RGB sensor systems at different RH levels. While the TRH model shows a high classification accuracy of 97.5% for the RH concentration, the RGB model yields 72.5% under identical conditions. Furthermore, we demonstrated the detection of various functional volatile gases with the TRH system by using experimental and simulation approaches. The results reveal distinct spectral features from the TRH system, corresponding to changes in the concentration of each substance.

The first record of leucism in the Rhabdophis tigrinus (Boie, 1826) (Squamata, Colubridae) in South Korea.

Leucism, in which pigmentation is lost over part or the entire body of an animal, has a range of possible genetic causes. Here, we report leucism in an individual tiger keelback (Rhabdophis tigrinus) found on Jeung Island, Shinan-gun, Jeollanam-do, South Korea, during a survey of the distribution of reptiles in the area. The individual was observed sunbathing in the bushes next to a pond. This individual exhibited ecdysis, thus it considered that have normal feeding activity. Our report represents the first observation of leucism in R. tigrinus, and thus, further analysis is needed of this phenotype to more clearly understand its impact on the species and its natural history.

Analogous Design of a Microlayered Silicon Oxide-Based Electrode to the General Electrode Structure for Thin-Film Lithium-Ion Batteries.

Development of miniaturized thin-film lithium-ion batteries (TF-LIBs) using vacuum deposition techniques is crucial for low-scale applications, but addressing low energy density remains a challenge. In this work, structures analogous to SiOx-based thin-film electrodes are designed with close resemblance to traditional LIB slurry formulations including active material, conductive agent, and binder. The thin-film is produced using mid-frequency sputtering with a single hybrid target consisting of SiOx nanoparticles, carbon nanotubes, and polytetrafluoroethylene. The thin-film SiOx/PPFC (plasma-polymerized fluorocarbon) involves a combination of SiOx and conductive carbon within the PPFC matrix. This results in enhanced electronic conductivity and superior elasticity and hardness in comparison to a conventional pure SiOx-based thin-film. The electrochemical performance of the half-cell consisting of thin-film SiOx/PPFC demonstrates remarkable cycling stability, with a capacity retention of 74.8% up to the 1000th cycle at 0.5 C. In addition, a full cell using the LiNi0.6Co0.2Mn0.2O2 thin-film as the cathode material exhibits an exceptional initial capacity of ≈120 mAh g-1 at 0.1 C and cycle performance, marked by a capacity retention of 90.8% from the first cycle to the 500th cycle at a 1 C rate. This work will be a stepping stone for the AM/CB/B composite electrodes in TF-LIBs.

Development of a Novel Korean H9-Specific rRT-PCR Assay and Its Application for Avian Influenza Virus Surveillance in Korea.

Since the 2000s, the Y439 lineage of H9N2 avian influenza virus (AIV) has been the predominant strain circulating in poultry in Korea; however, in 2020, the Y280 lineage emerged and spread rapidly nationwide, causing large economic losses. To prevent further spread and circulation of such viruses, rapid detection and diagnosis through active surveillance programs are crucial. Here, we developed a novel H9 rRT-PCR assay that can detect a broad range of H9Nx viruses in situations in which multiple lineages of H9 AIVs are co-circulating. We then evaluated its efficacy using a large number of clinical samples. The assay, named the Uni Kor-H9 assay, showed high sensitivity for Y280 lineage viruses, as well as for the Y439 lineage originating in Korean poultry and wild birds. In addition, the assay showed no cross-reactivity with other subtypes of AIV or other avian pathogens. Furthermore, the Uni Kor-H9 assay was more sensitive, and had higher detection rates, than reference H9 rRT-PCR methods when tested against a panel of domestically isolated H9 AIVs. In conclusion, the novel Uni Kor-H9 assay enables more rapid and efficient diagnosis than the "traditional" method of virus isolation followed by subtyping RT-PCR. Application of the new H9 rRT-PCR assay to AI active surveillance programs will help to control and manage Korean H9 AIVs more efficiently.

Association between birth-related factors and periodontitis in women: Korea National Health and Nutrition Examination Survey 2013-2018.

AIM: Adult women experience several changes in physiological status, such as pregnancy and childbirth, during their life cycle. This study analyses the association between birth-related factors (the number of childbirths, abortions and miscarriages) and periodontitis using data from the Korea National Health and Nutrition Examination Survey, which represents Korean adults. MATERIALS AND METHODS: The study used data from Korea National Health and Nutrition Examination Survey VI and VII (2013-2018) and included 10,072 women 19 years or older, with no missing data on the variables assessed. Periodontitis was defined according to the Community Periodontal Index (CPI) criteria. Multiple logistic regression analysis, adjusting for age, household income, education, alcohol consumption, smoking, stress, body mass index, waist circumference, hypertension, diabetes mellitus, an oral examination within 1 year, daily tooth brushing frequency, hygiene products and self-perceived oral health as identified via logistic regression analyses, was performed to determine the association between birth-related variables and periodontitis. RESULTS: In the crude model, the odds ratio (OR) showed a significantly increased risk of periodontitis (CPI ≥ 3) and severe periodontitis (CPI = 4) based on the number of childbirths, abortions and miscarriages (p < .05). After covariate adjustment, periodontitis (CPI ≥ 3) was associated with the number of childbirths (1: OR = 1.92; 95% confidence interval [CI]: 1.47-2.50; 2: OR = 2.03; 95% CI: 1.57-2.61; ≥3: OR = 2.11; 95% CI: 1.60-2.78). Furthermore, severe periodontitis (CPI = 4) was also associated with the number of childbirths (1: OR = 2.33; 95% CI: 1.24-4.38; 2: OR = 2.99; 95% CI: 1.62-5.52; ≥3: OR = 3.34; 95% CI: 1.79-6.21). CONCLUSIONS: The findings of this large-scale, nationally representative study suggest that the number of childbirths is associated with the severity of periodontitis. However, the relationship between the number of abortions and miscarriages and periodontitis (CPI ≥ 3) or severe periodontitis (CPI = 4) is not significant.

Determination and comparison of freely dissolved PAHs using different types of passive samplers in freshwater.

Polycyclic aromatic hydrocarbons (PAHs) are well-known for their recalcitrant properties and biotoxicity in organisms, leading to serious environmental and health problems. Despite various analytical methods available, accurate determination of the bioavailable fraction is warranted in order to evaluate the precise toxic potentials of these compounds. Currently, the passive sampler is used worldwide to measure the bioavailable PAHs in the environment using the equilibrium partitioning principle. In this study, we co-deployed different types of passive samplers, which are linear low-density polyethylene (LLDPE) and low-density polyethylene (LDPE), to determine freely dissolved concentrations (Cfree) of PAHs using the performance reference compounds (PRCs) in Kentucky Lake (KL), Ohio River (OH), and Mississippi River (MS). The fractional equilibrium (feq) of BeP-d12 was observed to be high in LLDPE compared with LDPE in OH and MS. In contrast, the feq of all PRCs was similar in both passive samplers in KL due to slow flow velocity. The sum of average freely dissolved PAH concentrations in LLDPE and LDPE during the exposure period were 2.89 and 1.27 ng/L in KL, 8.13 and 3.31 ng/L in OH, and 5.19 and 3.82 ng/L in MS, respectively. The results revealed that LLDPE is a suitable alternative tool to LDPE for both short-term and long-term monitoring of PAHs.

Statistical Analysis of the Performance of Local Veterinary Laboratories in Molecular Detection (rRT-PCR) of Avian Influenza Virus via National Proficiency Testing Performed during 2020-2022.

For the early detection of avian influenza virus (AIV), molecular diagnostic methods such as real-time RT-PCR (rRT-PCR) are the first choice in terms of accuracy and speed in many countries. A laboratory's capability to perform this diagnostic method needs to be measured through external and independent assessment to ensure that the method is validated within the laboratory and in interlaboratory comparison. The Animal and Plant Quarantine Agency of Korea has implemented five rounds of proficiency testing (PT) for rRT-PCR targeting local veterinary service laboratories involved in the AIV national surveillance program from 2020 to 2022. In each round, a portion composed of six or more samples was selected from the entire PT panel consisting of H5, H7, and H9 viruses isolated in Korea and distributed to each participant, and at least one pair of samples was commonly included in each panel for interlaboratory comparison. During the five rounds of PT, a few incorrect and outlying results were detected that required immediate inspection or corrective actions. However, in the quantitative measurement of Ct values, the average standard deviation or coefficient of variation decreased as multiple PT rounds progressed, and a positive correlation between consecutive rounds of PT was observed since 2021. The better consistency or stability in the experimental performance appeared to contribute to the more harmonized results in the latest PTs, and it is assumed that the positive reaction of participants to the challenges of quantitative assessment reports showing their status intuitively might work. We need to continue operating the PT program for local laboratories because they play crucial roles at the front line of the national avian influenza surveillance program, and frequent changes in the human resources or environment for diagnosis in those laboratories are inevitable.

Complementary Regulation of BfmRS Two-Component and AbaIR Quorum Sensing Systems to Express Virulence-Associated Genes in Acinetobacter baumannii.

Acinetobacter baumannii expresses various virulence factors to adapt to hostile environments and infect susceptible hosts. This study investigated the regulatory network of the BfmRS two-component and AbaIR quorum sensing (QS) systems in the expression of virulence-associated genes in A. baumannii ATCC 17978. The ΔbfmS mutant exhibited a significant decrease in surface motility, which presumably resulted from the low expression of pilT and A1S_0112-A1S_0119 gene cluster. The ΔbfmR mutant displayed a significant reduction in biofilm and pellicle formation due to the low expression of csu operon. The deletion of abaR did not affect the expression of bfmR or bfmS. However, the expression of abaR and abaI was upregulated in the ΔbfmR mutant. The ΔbfmR mutant also produced more autoinducers than did the wild-type strain, suggesting that BfmR negatively regulates the AbaIR QS system. The ΔbfmS mutant exhibited no autoinducer production in the bioassay system. The expression of the A1S_0112-A1S_0119 gene cluster was downregulated in the ΔabaR mutant, whereas the expression of csu operon was upregulated in this mutant with a high cell density. In conclusion, for the first time, we demonstrated that the BfmRS-AbaIR QS system axis regulated the expression of virulence-associated genes in A. baumannii. This study provides new insights into the complex network system involved in the regulation of virulence-associated genes underlying the pathogenicity of A. baumannii.

Association between Present Teeth and Muscle Strength in Older People in Korea.

BACKGROUND: As the world population continues to age, interest in muscle strength loss in older people is increasing. This study aimed to confirm the association between present teeth and muscle strength in older people in Korea. METHODS: Using data extracted from the 2014-2019 Korea National Health and Nutrition Examination Survey, we analyzed 5136 older people aged 65-79 years. The present teeth were based on 20 teeth, which is the criteria for comfortable mastication. The association of the risk of low muscle strength according to the present teeth was assessed using multiple logistic regression analysis, and the association was confirmed by dividing into subgroups according to sex. RESULTS: The prevalence of low muscle strength was 17.87% among all participants. Multiple logistic regression analysis confirmed the association between low muscle strength and present teeth; a significant association was found even in the model in which all covariates were adjusted (odds ratios (OR) = 1.35; 95% confidence interval (CI): 1.13-1.61). Subgroup analysis revealed a significant association between present teeth and low muscle strength even in the model in which both covariates were adjusted for sex (Men, OR = 1.41; 95% CI: 1.02-1.95; Women, OR = 1.31; 95% CI: 1.06-1.6). CONCLUSION: An association between present teeth and low muscle strength was confirmed in older people in Korea. These results indicate that the importance of oral hygiene management should be emphasized to prevent muscle strength loss in older people.

Association between Oral Health Status and Relative Handgrip Strength in 11,337 Korean.

Grip strength is a simple indicator of physical strength and is closely associated with systemic health. Conversely, oral health has also been reported to have an important association with systemic health. The present study aimed to assess the effect of oral health status on relative handgrip strength. The data pertaining to 11,337 participants were obtained by means of the seventh Korea National Health and Nutrition Survey (2016 to 2018). Oral health status was evaluated on the basis of the presence of periodontitis and number of remaining teeth (PT, present teeth). Relative handgrip strength was evaluated by means of a digital dynamometer and the value pertaining to the lower 25% of measurements was used as the quartile by gender. The association between oral health status and relative handgrip strength was evaluated by means of multiple regression analysis and multiple logistic regression analysis with covariate correction. Analysis of the crude model revealed a significant association in the group of patients with periodontal disease (odds ratio = 1.69, 95% confidence interval: 1.51-1.89). However, analysis with adjusted covariates revealed that the association was not statistically significant. Moreover, statistical analysis after adjustment for covariates revealed a consistent correlation between PT and relative handgrip strength as categorical and continuous variables. Hence, the present study observed a significant association between oral health status and relative handgrip strength among the Korean adult population.

Pathogenicity of H5N8 High Pathogenicity Avian Influenza Virus in Chickens and Ducks from South Korea in 2020-2021.

During the 2020-2021 winter season, an outbreak of clade 2.3.4.4b H5N8 high pathogenicity avian influenza (HPAI) virus occurred in South Korea. Here, we evaluated the pathogenicity and transmissibility of A/mandarin duck/Korea/H242/2020 (H5N8) (H242/20(H5N8)) first isolated from this outbreak in specific pathogen-free (SPF) chickens and commercial ducks in comparison with those of A/duck/Korea/HD1/2017(H5N6) (HD1/17(H5N6)) from a previous HPAI outbreak in 2017-2018. In chickens, the 50% chicken lethal dose and mean death time of H242/20(H5N8) group were 104.5 EID50 and 4.3 days, respectively, which indicate less virulent than those of HD1/17(H5N6) (103.6 EID50 and 2.2 days). Whereas, chickens inoculated with H242/20(H5N8) survived longer and had a higher titer of viral shedding than those inoculated with HD1/17(H5N6), which may increase the risk of viral contamination on farms. All ducks infected with either HPAI virus survived without clinical symptoms. In addition, they exhibited a longer virus shedding period and a higher transmission rate, indicating that ducks may play an important role as a silent carrier of both HPAI viruses. These results suggest that the pathogenic characteristics of HPAI viruses in chickens and ducks need to be considered to effectively control HPAI outbreaks in the field.

Selective Soxhlets extraction to enhance solubility of newly-synthesized poly(indoloindole-selenophene vinylene selenophene) donor for photovoltaic applications.

An electron-rich fused indoloindole-based poly(indoloindole-selenophene vinylene selenophene) was synthesized and characterized. Soxhlet can be obtained by continuously purifying the product with a specific solvent and obtaining a pure polymer with a high concentration. Molecular weight is affected by the vapor pressure of marginal solvent, and the polymer was fractionated using tetrahydrofuran, chloroform, and chlorobenzene. Solubility is closely related to the morphology of bulk heterojunction and device parameters. In the solution process of fabricating the organic solar cell, securement of solubility has a great effect on the performance of the device, because morphology and orientation of a photo-active layer which significantly affect charge transport in the device. Since tetrahydrofuran (THF) Soxhlet solvents have high vapor pressure and appropriate solubility parameters, THF induced the best solubility of P-IDI-SVS materials for organic solvents. And through additive optimization, the performance of the device based on P-IDI-SVS from THF-Soxhlet extraction was enhanced. This is expected to be a meaningful study because the effect on solubility of Soxhlet solvent suggests factors to be considered in the solution process in organic solar cell research. In addition, surface modified bulk heterojunction was observed using atomic force microscopy, photoluminescence, time-correlated single photon counting and Raman spectroscopy analysis.

Magnetically enhanced luminescence of CdSe/ZnS quantum dot light-emitting diodes using circular ferromagnetic Co/Pt multilayer disks.

We investigate the effect of a magnetic field on red, green, and blue CdSe/ZnS quantum dot light-emitting diodes (QDLEDs). Circular multilayer ferromagnetic cobalt/platinum (Co/Pt) disks are deposited on a MgF2 layer covering an Al electrode, and a perpendicular magnetic field is applied to the QDs in the active layer. Carriers injected into the active layer are then trapped and efficiently recombined inside the QDs because of strong carrier localization caused by the perpendicular magnetic field. The luminescence of the QDLEDs in the multilayer increases by 33.31% at 7.5 V, 22.34% at 7.5 V, and 16.73% at 7.0 V compared with that of QDLEDs without the multilayer. The time-resolved photoluminescence of all the QDLEDs also indicates that their increased luminescence results from improved radiative recombination through the stronger carrier localization in the QDs.

Hollow Porous Gold Nanoshells with Controlled Nanojunctions for Highly Tunable Plasmon Resonances and Intense Field Enhancements for Surface-Enhanced Raman Scattering.

Plasmonic metal nanostructures with nanogaps have attracted great interest owing to their controllable optical properties and intense electromagnetic fields that can be useful for a variety of applications, but precise and reliable control of nanogaps in three-dimensional nanostructures remains a great challenge. Here, we report the control of nanojunctions of hollow porous gold nanoshell (HPAuNS) structures by a facile oxygen plasma-etching process and the influence of changes in nanocrevices of the interparticle junction on the optical and sensing characteristics of HPAuNSs. We demonstrate a high tunability of the localized surface plasmon resonance (LSPR) peaks and surface-enhanced Raman scattering (SERS) detection of rhodamine 6G (R6G) using HPAuNS structures with different nanojunctions by varying the degree of gold sintering. As the neck region of the nanojunction is further sintered, the main LSPR peak shifts from 785 to 1350 nm with broadening because the charge transfer plasmon mode becomes more dominant than the dipolar plasmon mode, resulting from the increase of conductance at the interparticle junctions. In addition, it is demonstrated that an increase in the sharpness of the nanojunction neck can enhance the SERS enhancement factor of the HPAuNS by up to 4.8-fold. This enhancement can be ascribed to the more intense local electromagnetic fields at the sharper nanocrevices of interparticle junctions. The delicate change of nanojunction structures in HPAuNSs can significantly affect their optical spectrum and electromagnetic field intensity, which are critical for their practical use in a SERS-based analytical sensor as well as multiple-wavelength compatible applications.

The first hydride-Meisenheimer adduct of electron-deficient 3-nitronaphthalimide: application to colorimetric borohydride determination.

The first hydride-Meisenheimer adduct of 3-nitronaphthalimide was used for the colorimetric borohydride assay. To explain the regioselectivity of the adduct, the reaction enthalpies of the two most plausible Meisenheimer adducts were obtained via computational calculation. Using the adduct formation, the assay of borohydride reagents was successfully conducted.

Ultrasensitive and Stable Plasmonic Surface-Enhanced Raman Scattering Substrates Covered with Atomically Thin Monolayers: Effect of the Insulating Property.

We demonstrated the effects of monolayer graphene and hexagonal boron nitride (h-BN) on the stability and detection performance of two types of substrates in surface-enhanced Raman scattering (SERS): a two-dimensional (2D) monolayer/Ag nanoparticle (NP) substrate and a Au NP/2D monolayer/Ag NP substrate. Graphene and h-BN, which have different electrical and chemical properties, were introduced in close contact with the metal NPs and had distinctly different effects on the plasmonic near-field interactions between metal NPs in the subnanometer-scale gap and on the electron transport behavior. A quantitative comparison was possible due to reproducible SERS signals across the entire substrates prepared by simple and inexpensive fabrication methods. The hybrid platform, an insulating h-BN monolayer covering the Ag NP substrate, ensured the long-term oxidative stability for over 80 days, which was superior to the stability achieved using conducting graphene. Additionally, a sandwich structure using an h-BN monolayer exhibited excellent SERS sensitivity with a detection limit for rhodamine 6G as low as 10-12 M; to the best of our knowledge, this is the best SERS detection limit achieved using monolayer h-BN as a gap-control material. In this study, we suggest an efficient strategy for hybridizing the desired 2D layers with metal nanostructures for SERS applications, where the substrate stability and electromagnetic field enhancement are particularly crucial for the various applications that utilize metal/2D hybrid structures.

Enhanced optical output power of InGaN/GaN vertical light-emitting diodes by ZnO nanorods on plasma-treated N-face GaN.

Light-emitting diodes (LEDs) play an important role as a formidable contender for next-generation lighting sources and rapidly replace conventional lighting sources. In this report, the growth of high density inclined ZnO nanorods (NRs) on the N-face n-GaN surface for high efficiency vertical light-emitting diodes (VLEDs) is demonstrated based on oxygen plasma pretreatment and hydrothermal growth. Surface modification by oxygen plasma pretreatment efficiently produces GaOx nanoparticles on the N-face n-GaN surface and they play an important role in the hydrothermal growth of dense and inclined ZnO NRs. The optical output power of ZnO NR VLEDs following oxygen plasma pretreatment is strongly enhanced by a factor of 3.25 at an injection current of 350 mA, compared to that of planar VLEDs. The large enhancement of optical power is attributed to the dense ZnO NR layer which efficiently reduces the total internal reflection and enhances the waveguide effect in ZnO NRs.