How Hot Electron Generation at the Solid-Liquid Interface Is Different from the Solid-Gas Interface.

Excitation of hot electrons by energy dissipation under exothermic chemical reactions on metal catalyst surfaces occurs at both solid-gas and solid-liquid interfaces. Despite extensive studies, a comparative operando study directly comparing electronic excitation by electronically nonadiabatic interactions at solid-gas and solid-liquid interfaces has not been reported. Herein, on the basis of our in situ techniques for monitoring energy dissipation as a chemicurrent using a Pt/n-Si nanodiode sensor, we observed the generation of hot electrons in both gas and liquid phases during H2O2 decomposition. As a result of comparing the current signal and oxygen evolution rate in the two phases, surprisingly, the efficiency of reaction-induced excitation of hot electrons increased by ∼100 times at the solid-liquid interface compared to the solid-gas interface. The boost of hot electron excitation in the liquid phase is due to the presence of an ionic layer lowering the potential barrier at the junction for transferring hot electrons.

Systematic review and meta-analysis of the prevalence of chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME).

BACKGROUND: Chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) has been emerging as a significant health issue worldwide. This study aimed to systemically assess the prevalence of CFS/ME in various aspects of analyses for precise assessment. METHODS: We systematically searched prevalence of CFS/ME from public databases from 1980 to December 2018. Data were extracted according to 7 categories for analysis: study participants, gender and age of the participants, case definition, diagnostic method, publication year, and country of the study conducted. Prevalence data were collected and counted individually for studies adopted various case definitions. We analyzed and estimated prevalence rates in various angles: average prevalence, pooled prevalence and meta-analysis of all studies. RESULTS: A total of 1291 articles were initially identified, and 45 articles (46 studies, 56 prevalence data) were selected for this study. Total 1085,976 participants were enrolled from community-based survey (540,901) and primary care sites (545,075). The total average prevalence was 1.40 ± 1.57%, pooled prevalence 0.39%, and meta-analysis 0.68% [95% CI 0.48-0.97]. The prevalence rates were varied by enrolled participants (gender, study participants, and population group), case definitions and diagnostic methods. For example, in the meta-analysis; women (1.36% [95% CI 0.48-0.97]) vs. men (0.86% [95% CI 0.48-0.97]), community-based samples (0.76% [95% CI 0.53-1.10]) vs. primary care sites (0.63% [95% CI 0.37-1.10]), adults ≥ 18 years (0.65% [95% CI 0.43-0.99]) vs. children and adolescents < 18 years (0.55% [95% CI 0.22-1.35]), CDC-1994 (0.89% [95% CI 0.60-1.33]) vs. Holmes (0.17% [95% CI 0.06-0.49]), and interviews (1.14% [95% CI 0.76-1.72]) vs. physician diagnosis (0.09% [95% CI 0.05-0.13]), respectively. CONCLUSIONS: This study comprehensively estimated the prevalence of CFS/ME; 0.89% according to the most commonly used case definition CDC-1994, with women approximately 1.5 to 2 folds higher than men in all categories. However, we observed the prevalence rates are widely varied particularly by case definitions and diagnostic methods. An objective diagnostic tool is urgently required for rigorous assessment of the prevalence of CFS/ME.

Relationship of sociodemographic and anthropometric characteristics, and nutrient and food intakes with osteoarthritis prevalence in elderly subjects with controlled dyslipidaemia: a cross-sectional study.

BACKGROUND AND OBJECTIVES: Several studies have suggested that abnormal levels of serum cholesterol may be a major risk factor for osteoarthritis. However, no studies have been conducted to prevent osteoarthritis under controlled conditions of serum cholesterol. This study aimed to examine the relationship of sociodemographic and anthropometric characteristics, and nutrient and food intakes with osteoarthritis prevalence in Korean elderly subjects with controlled dyslipidaemia. METHODS AND STUDY DESIGN: This study included 314 subjects aged ≥65 years who were diagnosed and treated for dyslipidaemia (data from the Seventh Korea National Health and Nutrition Examination Survey, 2016). Among them, 108 were also diagnosed with osteoarthritis. Sociodemographic, health, and nutritional data were analysed. RESULTS: Osteoarthritis prevalence was higher in females, highereducated subjects, unmarried subjects, non-smokers, and subjects with high body mass index (p<0.05). After adjusting for the multiple variables, the non-osteoarthritis group had significantly higher vitamin C intake (132±11.0 vs 93.1±11.1 mg/day), fish intake (172±30.0 vs 79.0±12.9 g/day), and seaweed intake (93.7±19.3 vs 38.3±13.4 mg/day) than the osteoarthritis group. Furthermore, the lowest vitamin C, fish, seaweed intake group (quartile 1) each had 3.20, 2.76, 9.93 times higher risk of osteoarthritis than the highest vitamin C, fish, seaweed intake group (quartile 4) (p<0.05). CONCLUSIONS: Among Korean elderly subjects with controlled dyslipidaemia, those with osteoarthritis had lower vitamin C, fish, seaweed intakes than those without osteoarthritis. Although our results do not prove that low vitamin C, fish, seaweed intakes cause osteoarthritis, such relationship is worth exploring for a preventive perspective.

Identification of five novel genetic loci related to facial morphology by genome-wide association studies.

BACKGROUND: Face morphology is strongly determined by genetic factors. However, only a small number of genes related to face morphology have been identified to date. Here, we performed a two-stage genome-wide association study (GWAS) of 85 face morphological traits in 7569 Koreans (5643 in the discovery set and 1926 in the replication set). RESULTS: In this study, we analyzed 85 facial traits, including facial angles. After discovery GWAS, 128 single nucleotide polymorphisms (SNPs) showing an association of P < 5 × 10- 6 were selected to determine the replication of the associations, and meta-analysis of discovery GWAS and the replication analysis resulted in five genome-wide significant loci. The OSR1-WDR35 [rs7567283, G allele, beta (se) = -0.536 (0.096), P = 2.75 × 10- 8] locus was associated with the facial frontal contour; the HOXD1-MTX2 [rs970797, A allele, beta (se) = 0.015 (0.003), P = 3.97 × 10- 9] and WDR27 [rs3736712, C allele, beta (se) = 0.293 (0.048), P = 8.44 × 10- 10] loci were associated with eye shape; and the SOX9 [rs2193054, C allele, beta (se) (ln-transformed) = -0.007 (0.001), P = 6.17 × 10- 17] and DHX35 [rs2206437, A allele, beta (se) = -0.283 (0.047), P = 1.61 × 10- 9] loci were associated with nose shape. WDR35 and SOX9 were related to known craniofacial malformations, i.e., cranioectodermal dysplasia 2 and campomelic dysplasia, respectively. In addition, we found three independent association signals in the SOX9 locus, and six known loci for nose size and shape were replicated in this study population. Interestingly, four SNPs within these five face morphology-related loci showed discrepancies in allele frequencies among ethnic groups. CONCLUSIONS: We identified five novel face morphology loci that were associated with facial frontal contour, nose shape, and eye shape. Our findings provide useful genetic information for the determination of face morphology.

Genomic structure, expression and association study of the porcine FSD2.

The fibronectin type III and SPRY domain containing 2 (FSD2) on porcine chromosome 7 is considered a candidate gene for pork quality, since its two domains, which were present in fibronectin and ryanodine receptor. The fibronectin type III and SPRY domains were first identified in fibronectin and ryanodine receptor, respectively, which are candidate genes for meat quality. The aim of this study was to elucidate the genomic structure of FSD2 and functions of single nucleotide polymorphisms (SNPs) within FSD2 that are related to meat quality in pigs. Using a bacterial artificial chromosome clone sequence, we revealed that porcine FSD2 consisted of 13 exons encoding 750 amino acids. In addition, FSD2 was expressed in heart, longissimus dorsi muscle, psoas muscle, and tendon among 23 kinds of porcine tissues tested. A total of ten SNPs, including four missense mutations, were identified in the exonic region of FSD2, and two major haplotypes were obtained based on the SNP genotypes of 633 Berkshire pigs. Both haplotypes were associated significantly with intramuscular fat content (IMF, P < 0.020) and moisture percentage (MP, P < 0.002). Moreover, haplotype 2 was associated with meat color, affecting yellowness (P = 0.002). These haplotype effects were further supported by the alteration of putative protein structures with amino acid substitutions. Taken together, our results suggest that FSD2 haplotypes are involved in regulating meat quality including IMF, MP, and meat color in pigs, and may be used as meaningful molecular makers to identify pigs with preferable pork quality.

Temperature-Dependent Evolution of Poly(3-Hexylthiophene) Type-II Phase in a Blended Thin Film.

The structure of P3HT in P3HT:PCBM films is examined on a poly(3,4-ethylenedioxythiophene) polystyrene sulfonate ( PEDOT: PSS) substrate subjected to cryo-cooling to low temperature (-143 °C) followed by gradual heating to 50 °C. The behavior of these systems is examined in the absence and presence of an Al electrode on top of the P3HT:PCBM film. At temperatures below -10 °C, only the type-I phase of P3HT is observed. However, the type-II phase of P3HT starts to form near -10 °C, in both the presence and absence of the Al layer. In the system without an Al layer, the type-II phase disappears at 30 °C, but this phase persists to 50 °C in the presence of the Al layer. Concomitant with the formation of the type-II phase, a 1:3 ordered P3HT type-II (1/3,0,0) superlattice peak emerged. The type-II domains tend to form near the Al electrode layer and show a higher degree of alignment than the type-I crystals.

A genome-wide scan for signatures of directional selection in domesticated pigs.

BACKGROUND: Animal domestication involved drastic phenotypic changes driven by strong artificial selection and also resulted in new populations of breeds, established by humans. This study aims to identify genes that show evidence of recent artificial selection during pig domestication. RESULTS: Whole-genome resequencing of 30 individual pigs from domesticated breeds, Landrace and Yorkshire, and 10 Asian wild boars at ~16-fold coverage was performed resulting in over 4.3 million SNPs for 19,990 genes. We constructed a comprehensive genome map of directional selection by detecting selective sweeps using an F ST-based approach that detects directional selection in lineages leading to the domesticated breeds and using a haplotype-based test that detects ongoing selective sweeps within the breeds. We show that candidate genes under selection are significantly enriched for loci implicated in quantitative traits important to pig reproduction and production. The candidate gene with the strongest signals of directional selection belongs to group III of the metabolomics glutamate receptors, known to affect brain functions associated with eating behavior, suggesting that loci under strong selection include loci involved in behaviorial traits in domesticated pigs including tameness. CONCLUSIONS: We show that a significant proportion of selection signatures coincide with loci that were previously inferred to affect phenotypic variation in pigs. We further identify functional enrichment related to behavior, such as signal transduction and neuronal activities, for those targets of selection during domestication in pigs.

Non-alcoholic fatty liver disease among sasang constitutional types: a population-based study in Korea.

BACKGROUND: Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease and is highly prevalent in populations with metabolic conditions such as obesity and type II diabetes. Specific types of Sasang constitution can act as a risk factor for metabolic diseases, but there are no studies addressing the association between the Sasang constitutional types (SCTs) and NAFLD. METHODS: A total of 1184 individuals (508 males, 676 females) that enrolled in the Korean Genome and Epidemiology Study were included in the present study. Classification of SCTs was done with an integrated diagnostic model. NAFLD was diagnosed when the liver attenuation index (LAI) value was <5 Hounsfield units using computed tomography. Relationships between the SCTs and NAFLD were analyzed using multiple logistic regressions. RESULTS: The average LAI was 13.3±6.0 in the So-eum (SE) type, 12.3±7.0 in the So-yang (SY) type, and 6.5±9.9 in the Tae-eum (TE) type. Prevalence of NAFLD was 4.7% in the SE type, 14.0% in the SY type, and 34% in the TE type. Even after adjusting for possible confounders, the SY and TE types continued to show a 3.90-fold (95% CI, 1.60-9.51; P=0.0028) and 3.36-fold (95% CI, 1.42-7.92; P=0.0057) increase in chance of having NAFLD, respectively, compared with the SE type. In the additional analysis including only non-obese subjects, the odds ratio of NAFLD was 3.27 (95% CI, 1.29-8.29; P=0.0126) in the SY type and 3.53 (95% CI, 1.30-9.58; P=0.0134) in the TE type compared with SE type. In the multivariate analysis to determine which parameter had an independent association with NAFLD, higher body mass index, alanine aminotransferase (ALT), triglyceride (TG), and low high-density lipoprotein cholesterol were independently associated with developing NAFLD in the SY type. In contrast, male sex, alcohol consumption, higher ALT, TG, and fasting glucose were risk factors for NAFLD in the TE type. CONCLUSIONS: These results indicated that the SY and TE types are independent risk factors for NAFLD.

Effects of a 2-Week Kinect-Based Mixed-Reality Exercise Program on Prediabetes: A Pilot Trial during COVID-19.

Background: Pre-diabetes can develop into type 2 diabetes mellitus, but can prevented by regular exercise. However, the outcomes when combining unsupervised Kinect-based mixed-reality (KMR) exercise with continuous glucose monitoring (CGM) remain unclear. Therefore, this single-arm pilot trial examined changes in blood glucose (BG) concentrations over 672 hours (4 weeks), including a 2-week period of KMR exercise and CGM in individuals with pre-diabetes. Methods: This was a pre-and post-treatment case-control study with nine participants. General questionnaires were administered and body composition, fasting BG concentrations, and 2-hour oral glucose tolerance test (2-OGTT) results were measured pre-and post-treatment. Weekly average glucose concentrations, hyperglycemia rate, hypoglycemia rate, average glucose concentration over time, amount of physical activity, amount of food intake, and pre- and postprandial BG (immediately and 30, 60, 90, and 120 minutes after lunch) were measured over 4 weeks (pre-test, exercise, and post -test weeks). Glucose concentrations were measured before exercising, between sets, and 30 and 60 minutes after exercise during the 2 weeks of unsupervised exercise (3 days/week). Results: In all participants, body mass index (27.16±2.92 kg/m2), fasting BG (108.00±7.19 mg/dL), 2-OGTT (162.56±18.12 mg/dL), hyperglycemia rate (P=0.040), and 90-minute postprandial BG (P=0.035) were significantly reduced during the 2 exercise weeks, and the 2-OGTT result (P=0.044) and diastolic blood pressure (DBP) (P=0.046) were significantly reduced at the post -test as compared with the pre-test. Conclusion: This study found that 2 weeks of unsupervised KMR exercise reduced 2-OGTT, DBP, hyperglycemia rate, and 90-minute postprandial BG concentration. We believed this effect could be identified more clearly in studies involving a larger number of participants and longer durations of exercise.

Total nasal resistance among Sasang constitutional types: a population-based study in Korea.

BACKGROUND: There have been many attempts to find an objective phenotype by Sasang constitutional types (SCTs) on an anatomical, physiological, and psychological basis, but there has been no research on total nasal resistance (TNR) among SCTs. METHODS: We assessed the value of the TNR in the SCTs classified by an integrated diagnostic model. Included in the study were 1,346 individuals (701 males, 645 females) who participated in the Korean Genome and Epidemiology Study (KoGES). The TNR was measured by active anterior rhinomanometry (AAR) at transnasal pressures of 100 and 150 Pascal (Pa). RESULTS: The average TNR was 0.186 ± 0.004 Pa/cm3/second at 100 Pa in the Tae-eum (TE), 0.193 ± 0.007 in the So-eum (SE), and 0.208 ± 0.005 in the So-yang (SY) types. Under condition of 150 Pa the TE type had a TNR value of 0.217 ± 0.004, the SE type was 0.230 ± 0.008, and the SY type was 0.243 ± 0.005. Higher values of TNR were more likely to be reported in the SY type at 100 Pa and 150 Pa. In the stratified analysis by sex, the SY type in males and females tended to have higher TNR value than the TE and SE types at transnasal pressure of both 100 Pa and 150 Pa. CONCLUSIONS: These results provide new approaches to understand the functional characteristics among the SCTs in terms of nasal physiology. Further studies are required to clarify contributing factors for such a difference.

Validation of Fitbit Inspire 2TM Against Polysomnography in Adults Considering Adaptation for Use.

Purpose: The commercialization of sleep activity tracking devices has made it possible to manage sleep quality at home. However, it is necessary to verify the reliability and accuracy of wearable devices through comparison with polysomnography (PSG), which is the standard for tracking sleep activity. This study aimed to monitor overall sleep activity using Fitbit Inspire 2™ (FBI2) and to evaluate its performance and effectiveness through PSG under the same conditions. Patients and Methods: We compared the FBI2 and PSG data of nine participants (four male and five female participants; average age, 39 years) without severe sleeping problems. The participants wore FBI2 continuously for 14 days, considering the period of adaptation to the device. FBI2 and PSG sleep data were compared using paired t-tests, Bland-Altman plots, and epoch-by-epoch analysis for 18 samples by pooling data from two replicates. Results: The average values for each sleep stage obtained from FBI2 and PSG showed significant differences in the total sleep time (TST), deep sleep, and rapid eye motion (REM). In the Bland-Altman analysis, TST (P = 0.02), deep sleep (P = 0.05), and REM (P = 0.03) were significantly overstated in FBI2 compared to PSG. In addition, time in bed, sleep efficiency, and wake after sleep onset were overestimated, while light sleep was underestimated. However, these differences were not statistically significant. FBI2 showed a high sensitivity (93.9%) and low specificity (13.1%), with an accuracy of 76%. The sensitivity and specificity of each sleep stage was 54.3% and 62.3%, respectively, for light sleep, 84.8% and 50.1%, respectively, for deep sleep, and 86.4% and 59.1%, respectively for REM sleep. Conclusion: The use of FBI2 as an objective tool for measuring sleep in daily life can be considered appropriate. However, further research is warranted on its application in participants with sleep-wake problems.

Unraveling surface structures of gallium promoted transition metal catalysts in CO2 hydrogenation.

Gallium-containing alloys have recently been reported to hydrogenate CO2 to methanol at ambient pressures. However, a full understanding of the Ga-promoted catalysts is still missing due to the lack of information about the surface structures formed under reaction conditions. Here, we employed near ambient pressure scanning tunneling microscopy and x-ray photoelectron spectroscopy to monitor the evolution of well-defined Cu-Ga surfaces during CO2 hydrogenation. We show the formation of two-dimensional Ga(III) oxide islands embedded into the Cu surface in the reaction atmosphere. The islands are a few atomic layers in thickness and considerably differ from bulk Ga2O3 polymorphs. Such a complex structure, which could not be determined with conventional characterization methods on powder catalysts, should be used for elucidating the reaction mechanism on the Ga-promoted metal catalysts.

Interaction of Gallium with a Copper Surface: Surface Alloying and Formation of Ordered Structures.

Alloys of gallium with transition metals have recently received considerable attention for their applications in microelectronics and catalysis. Here, we investigated the initial stages of the Ga-Cu alloy formation on Cu(111) and Cu(001) surfaces using scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and low energy electron diffraction (LEED). The results show that Ga atoms deposited using physical vapor deposition readily intermix with the Cu surface, leading to a random distribution of the Ga and Cu atoms within the surface layer, on both terraces and monolayer-thick islands formed thereon. However, as the Ga coverage increases, several ordered structures are formed. The (√3×√3)R30° structure is found to be thermodynamically most stable on Cu(111). This structure remains after vacuum annealing at 600 K, independent of the initial Ga coverage (varied between 0.5 and 3 monolayers), indicating a self-limited growth of the Ga-Cu alloy layer, with the rest of the Ga atoms migrating into the Cu crystal. For Ga deposited on Cu(001), we observed a (1 × 5)-reconstructed surface, which has never been observed for surface alloys on Cu(001). The experimental findings were rationalized on the basis of density functional theory (DFT) calculations, which provided structural models for the most stable surface Ga-Cu alloys on Cu(111) and Cu(001). The study sheds light on the complex interaction of Ga with transition metal surfaces and the interfaces formed thereon that will aid in a better understanding of surface alloying and chemical reactions on the Ga-based alloys.

Hot Electron Phenomena at Solid-Liquid Interfaces.

Understanding the role of energy dissipation and charge transfer under exothermic chemical reactions on metal catalyst surfaces is important for elucidating the fundamental phenomena at solid-gas and solid-liquid interfaces. Recently, many surface chemistry studies have been conducted on the solid-liquid interface, so correlating electronic excitation in the liquid-phase with the reaction mechanism plays a crucial role in heterogeneous catalysis. In this review, we introduce the detection principle of electron transfer at the solid-liquid interface by developing cutting-edge technologies with metal-semiconductor Schottky nanodiodes. The kinetics of hot electron excitation are well correlated with the reaction rates, demonstrating that the operando method for understanding nonadiabatic interactions is helpful in studying the reaction mechanism of surface molecular processes. In addition to the detection of hot electrons excited by a catalytic reaction, we highlight recent results on how the transfer of the hot electrons influences surface chemical and photoelectrochemical reactions.

DA-1241, a Novel GPR119 Agonist, Improves Hyperglycaemia by Inhibiting Hepatic Gluconeogenesis and Enhancing Insulin Secretion in Diabetic Mice.

BACKGROUND: We investigated the antidiabetic effects of DA-1241, a novel G protein-coupled receptor (GPR) 119 agonist, in vitro and in vivo. METHODS: DA-1241 was administrated to high-fat diet (HFD)-fed C57BL/6J mice for 12 weeks after hyperglycaemia developed. Oral/intraperitoneal glucose tolerance test and insulin tolerance test were performed. Serum insulin and glucagon-like peptide-1 (GLP-1) levels were measured during oral glucose tolerance test. Insulinoma cell line (INS-1E) cells and mouse islets were used to find whether DA-1241 directly stimulate insulin secretion in beta cell. HepG2 cells were used to evaluate the gluconeogenesis and autophagic process. Autophagic flux was evaluated by transfecting microtubule-associated protein 1 light chain 3-fused to green fluorescent protein and monomeric red fluorescent (mRFP-GFP-LC3) expression vector to HepG2 cells. RESULTS: Although DA-1241 treatment did not affect body weight gain and amount of food intake, fasting blood glucose level decreased along with increase in GLP-1 level. DA-1241 improved only oral glucose tolerance test and showed no effect in intraperitoneal glucose tolerance test. No significant effect was observed in insulin tolerance test. DA-1241 did not increase insulin secretion in INS-1E cell and mouse islets. DA-1241 reduced triglyceride content in the liver thereby improved fatty liver. Additionally, DA-1241 reduced gluconeogenic enzyme expression in HepG2 cells and mouse liver. DA-1241 reduced autophagic flow in HepG2 cells. CONCLUSION: These findings suggested that DA-1241 augmented glucose-dependent insulin release via stimulation of GLP-1 secretion, and reduced hepatic gluconeogenesis, which might be associated with autophagic blockage, leading to improved glycaemic control.

The effect of biphasic calcium phosphate and demineralized bone matrix on tooth eruption in mongrel dogs.

BACKGROUND: Bone grafts can provide an optimal environment for permanent tooth to erupt and enhance the stability of the alveolar maxilla. Although autologous bone is an optimal source for osteogenesis, its inevitable donor site morbidity has led to active research on bone substitutes. This study was designed to evaluate the safety and feasibility of using biphasic calcium phosphate (BCP; Osteon) as a bone substitute in dogs. METHODS: Bilateral third and fourth premolars of four 15-week-old mongrel dogs were used. All teeth were extracted except the third premolar of the right mandible, which was used as a control. After extraction of the premolars, each dog was administered BCP (Osteon), demineralized bone matrix (DBM; DBX), and no graft in the hollow sockets of the right fourth premolar, left fourth premolar, and left third premolar, respectively. Radiographs were taken at 2-week intervals to check for tooth eruption. After 8 weeks, each dog was sacrificed, and tooth and bone biopsies were performed to check for the presence of tooth and bone substitute particle remnants. RESULTS: Four weeks after the operation, permanent tooth eruptions had started at all the extraction sites in each dog. Eight weeks after the operation, all teeth had normally erupted, and histological examination revealed BCP particles at the right fourth premolar. CONCLUSION: In all four dogs, no delay in the eruption of the teeth or shape disfigurement of permanent teeth was observed on gross inspection and radiologic evaluation. On histological examination, most of the BCP and DBM were replaced by new bone. Bone substitutes can be used as graft materials in patients with alveolar clefts.

Controlling hot electron flux and catalytic selectivity with nanoscale metal-oxide interfaces.

Interaction between metal and oxides is an important molecular-level factor that influences the selectivity of a desirable reaction. Therefore, designing a heterogeneous catalyst where metal-oxide interfaces are well-formed is important for understanding selectivity and surface electronic excitation at the interface. Here, we utilized a nanoscale catalytic Schottky diode from Pt nanowire arrays on TiO2 that forms a nanoscale Pt-TiO2 interface to determine the influence of the metal-oxide interface on catalytic selectivity, thereby affecting hot electron excitation; this demonstrated the real-time detection of hot electron flow generated under an exothermic methanol oxidation reaction. The selectivity to methyl formate and hot electron generation was obtained on nanoscale Pt nanowires/TiO2, which exhibited ~2 times higher partial oxidation selectivity and ~3 times higher chemicurrent yield compared to a diode based on Pt film. By utilizing various Pt/TiO2 nanostructures, we found that the ratio of interface to metal sites significantly affects the selectivity, thereby enhancing chemicurrent yield in methanol oxidation. Density function theory (DFT) calculations show that formation of the Pt-TiO2 interface showed that selectivity to methyl formate formation was much larger in Pt nanowire arrays than in Pt films because of the different reaction mechanism.

Operando Surface Characterization on Catalytic and Energy Materials from Single Crystals to Nanoparticles.

Modern surface science faces two major challenges, a materials gap and a pressure gap. While studies on single crystal surface in ultrahigh vacuum have uncovered the atomic and electronic structures of the surface, the materials and environmental conditions of commercial catalysis are much more complicated, both in the structure of the materials and in the accessible pressure range of analysis instruments. Model systems and operando surface techniques have been developed to bridge these gaps. In this Review, we highlight the current trends in the development of the surface characterization techniques and methodologies in more realistic environments, with emphasis on recent research efforts at the Korea Advanced Institute of Science and Technology. We show principles and applications of the microscopic and spectroscopic surface techniques at ambient pressure that were used for the characterization of atomic structure, electronic structure, charge transport, and the mechanical properties of catalytic and energy materials. Ambient pressure scanning tunneling microscopy and X-ray photoelectron spectroscopy allow us to observe the surface restructuring that occurs during oxidation, reduction, and catalytic processes. In addition, we introduce the ambient pressure atomic force microscopy that revealed the morphological, mechanical, and charge transport properties that occur during the catalytic and energy conversion processes. Hot electron detection enables the monitoring of catalytic reactions and electronic excitations on the surface. Overall, the information on the nature of catalytic reactions obtained with operando spectroscopic and microscopic techniques may bring breakthroughs in some of the global energy and environmental problems the world is facing.

Engineering Nanoscale Interfaces of Metal/Oxide Nanowires to Control Catalytic Activity.

The interfacial effect between a metal catalyst and its various supporting transition metal oxides on the catalytic activity of heterogeneous catalysis has been extensively explored; engineering interfacial sites of metal supported on metal oxide has been found to influence catalytic performance. Here, we investigate the interfacial effect of Pt nanowires (NWs) vertically and alternatingly stacked with titanium dioxide (TiO2) or cobalt monoxide (CoO) NWs, which exhibit a strong metal-support interaction under carbon monoxide (CO) oxidation. High-resolution nanotransfer printing based on nanoscale pattern replication and e-beam evaporation were utilized to obtain the Pt NWs cross-stacked on the CoO or TiO2 NW on the silicon dioxide (SiO2) substrate with varying numbers of nanowires. The morphology and interfacial area were precisely determined by means of atomic force microscopy and scanning electron microscopy. The cross-stacked Pt/TiO2 NW and Pt/CoO NW catalysts were estimated with CO oxidation under 40 Torr CO and 100 Torr O2 from 200 to 240 °C. Higher catalytic activity was found on the Pt/CoO NW catalyst than on Pt/TiO2 NWs and Pt NWs, which indicates the significance of nanoscale metal-oxide interfaces. As the number of nanowire layers increased, the catalytic activity became saturated. Our study demonstrates the interfacial role of nanoscale metal-oxide interfaces under CO oxidation, which has intriguing applications in the smart design of catalytic materials.