16 research outputs found
Ag–ZnO Nanocomposites as a 3D Metal-Enhanced Fluorescence Substrate for the Fluorescence Detection of DNA
Fluorescence enhancement, including metal-enhanced fluorescence
(MEF), has been widely explored in the field of biosensor technology.
Two- and three-dimensional (2D and 3D) MEF substrate approaches have
been developed for biosensors to detect target biomarkers such as
genes and proteins. However, several issues remain, not least poor
reproducibility caused by limited recognition and diffusion of biomolecules
among target molecules, biological probes, and MEF substrates in aqueous
environments. Here, an Ag–ZnO nanocomplex as a 3D MEF substrate
was developed in two steps: hydrothermal synthesis of ZnO nanowire
(NW) as a building block of Ag nanoparticles (NPs), and photochemical
deposition of AgNPs on the ZnO NW. Fluorescence enhancement on Ag–ZnO
nanocomposites (NCs) compared with the glass substrate was 14.8-,
16.9-, 11.4-, and 14.2-fold in the presence of 10, 20, 40, and 60
base pair (bp) double-stranded (ds) DNA, respectively. The MEF effects
on glass, ZnO NW, and Ag–ZnO NCs were analyzed by measuring
the fluorescence lifetime of fluorescein (FAM)-labeled dsDNA, and
the average lifetimes were 9.76, 9.34, and 7.86 ns, respectively.
Ag–ZnO NCs showed a 50-fold higher sensitivity for the detection
of dsDNA than Ag nanoisland film (AgNIF) as a 2D MEF substrate. Therefore,
Ag–ZnO NCs may have potential as a 3D MEF substrate. The MEF
phenomenon might involve broad-range interactions between the surface
of the metal nanostructure on Ag–ZnO NCs and fluorophores in
various scenarios. Our Ag–ZnO NCs could facilitate the development
of sensitive MEF-based biosensors for DNA detection
Enhanced Electrochemical and Photocatalytic Performance of Core–Shell CuS@Carbon Quantum Dots@Carbon Hollow Nanospheres
A controlled
structural morphology, high specific surface area, large void space,
and excellent biocompatibility are typical favorable properties in
electrochemical energy storage and photocatalytic studies; however,
a complete understanding about this essential topic still remains
a great challenge. Herein, we have developed a new type of functionalized
carbon hollow-structured nanospheres based on core–shell copper
sulfide@carbon quantum dots (CQDs)@carbon hollow nanosphere (CHNS)
architecture. This CuS@CQDs@C HNS is accomplished by a simple, scalable, <i>in situ</i> single-step hydrothermal method to produce the material
that can be employed as an electrode for electrochemical energy storage
and photocatalytic applications. Impressively, the CuS@CQDs@C HNS
nanostructure delivers exceptional electrochemical energy storage
characteristics with high specific capacitance (618 F g<sup>–1</sup> at a current density of 1 A g<sup>–1</sup>) and an excellent
rate capability with an extraordinary capacitance (462 F g<sup>–1</sup> at current density of 20 A g<sup>–1</sup>) and long cycle
life (95% capacitance retention after 4000 cycles). Further, the proposed
photocatalyst exhibited superior photocatalytic activity under solar
light due to the efficient electron transfer, which was revealed by
photoluminescence studies. Such superior electrochemical and photocatalytic
performance can be ascribed to the mutual contribution of CuS, CQDs,
and CHNS and unique core–shell architecture. These results
exhibit that the core–shell CuS@CQDs@C HNS nanostructure is
one of the potential candidates for supercapacitors and photocatalytic
applications
Hierarchical Heterostructures of Ultrasmall Fe<sub>2</sub>O<sub>3</sub>‑Encapsulated MoS<sub>2</sub>/N-Graphene as an Effective Catalyst for Oxygen Reduction Reaction
In
this study, a facile approach has been successfully applied to synthesize
a hierarchical three-dimensional architecture of ultrasmall hematite
nanoparticles homogeneously encapsulated in MoS<sub>2</sub>/nitrogen-doped
graphene nanosheets, as a novel non-Pt cathodic catalyst for oxygen
reduction reaction in fuel cell applications. The intrinsic topological
characteristics along with unique physicochemical properties allowed
this catalyst to facilitate oxygen adsorption and sped up the reduction
kinetics through fast heterogeneous decomposition of oxygen to final
products. As a result, the catalyst exhibited outstanding catalytic
performance with a high electron-transfer number of 3.91–3.96,
which was comparable to that of the Pt/C product. Furthermore, its
working stability with a retention of 96.1% after 30 000 s
and excellent alcohol tolerance were found to be significantly better
than those for the Pt/C product. This hybrid can be considered as
a highly potential non-Pt catalyst for practical oxygen reduction
reaction application in requirement of low cost, facile production,
high catalytic behavior, and excellent stability
Highly Active and Durable Core–Shell fct-PdFe@Pd Nanoparticles Encapsulated NG as an Efficient Catalyst for Oxygen Reduction Reaction
Development of highly
active and durable catalysts for oxygen reduction
reaction (ORR) alternative to Pt-based catalyst is an essential topic
of interest in the research community but a challenging task. Here,
we have developed a new type of face-centered tetragonal (fct) PdFe-alloy
nanoparticle-encapsulated Pd (fct-PdFe@Pd) anchored onto nitrogen-doped
graphene (NG). This core–shell fct-PdFe@Pd@NG hybrid is fabricated
by a facile and cost-effective technique. The effect of temperature
on the transformation of face-centered cubic (fcc) to fct structure
and their effect on ORR activity are systematically investigated.
The core–shell fct-PdFe@Pd@NG hybrid exerts high synergistic
interaction between fct-PdFe@Pd NPs and NG shell, beneficial to enhance
the catalytic ORR activity and excellent durability. Impressively,
core–shell fct-PdFe@Pd@NG hybrid exhibits an excellent catalytic
activity for ORR with an onset potential of ∼0.97 V and a half-wave
potential of ∼0.83 V versus relative hydrogen electrode, ultrahigh
current density, and decent durability after 10 000 potential
cycles, which is significantly higher than that of marketable Pt/C
catalyst. Furthermore, the core–shell fct-PdFe@Pd@NG hybrid
also shows excellent tolerance to methanol, unlike the commercial
Pt/C catalyst. Thus, these findings open a new protocol for fabricating
another core–shell hybrid by facile and cost-effective techniques,
emphasizing great prospect in next-generation energy conversion and
storage applications
Facile Method for the Preparation of Water Dispersible Graphene using Sulfonated Poly(ether–ether–ketone) and Its Application as Energy Storage Materials
A simple and effective method for the preparation of
water dispersible
graphene using sulfonated polyÂ(ether–ether–ketone) (SPEEK)
has been described. The SPEEK macromolecules are noncovalently adsorbed
on the surface of graphene through π–π interactions.
The SPEEK-modified graphene (SPG) forms an aqueous dispersion that
is stable for more than six months. An analysis of the ultraviolet–visible
spectra shows that the aqueous dispersion of SPG obeys Beer’s
law and the molar extinction coefficient has been found to be 149.03
mL mg<sup>–1</sup> cm<sup>–1</sup>. Fourier transform
infrared, Raman, and X-ray photoelectron spectroscopy analyses confirm
successful reduction and surface modification of graphene. An atomic
force microscopy (AFM) analysis reveals the formation of a single
layer of functionalized graphene. Transmission electron microscopy
results are also in good agreement with the AFM analysis and support
the formation of single-layer graphene. SPG shows good electrochemical
cyclic stability during cyclic voltammetry and charge/discharge process
when used as a supercapacitor electrode. A specific capacitance of
476 F g<sup>–1</sup> at a current density of 6.6 A g<sup>–1</sup> is observed for SPG materials
Table1_Metformin acts as a dual glucose regulator in mouse brain.DOCX
Aims: Metformin improves glucose regulation through various mechanisms in the periphery. Our previous study revealed that oral intake of metformin activates several brain regions, including the hypothalamus, and directly activates hypothalamic S6 kinase in mice. In this study, we aimed to identify the direct effects of metformin on glucose regulation in the brain.Materials and methods: We investigated the role of metformin in peripheral glucose regulation by directly administering metformin intracerebroventricularly in mice. The effect of centrally administered metformin (central metformin) on peripheral glucose regulation was evaluated by oral or intraperitoneal glucose, insulin, and pyruvate tolerance tests. Hepatic gluconeogenesis and gastric emptying were assessed to elucidate the underlying mechanisms. Liver-specific and systemic sympathetic denervation were performed.Results: Central metformin improved the glycemic response to oral glucose load in mice compared to that in the control group, and worsened the response to intraperitoneal glucose load, indicating its dual role in peripheral glucose regulation. It lowered the ability of insulin to decrease serum glucose levels and worsened the glycemic response to pyruvate load relative to the control group. Furthermore, it increased the expression of hepatic G6pc and decreased the phosphorylation of STAT3, suggesting that central metformin increased hepatic glucose production. The effect was mediated by sympathetic nervous system activation. In contrast, it induced a significant delay in gastric emptying in mice, suggesting its potent role in suppressing intestinal glucose absorption.Conclusion: Central metformin improves glucose tolerance by delaying gastric emptying through the brain-gut axis, but at the same time worsens it by increasing hepatic glucose production via the brain-liver axis. However, with its ordinary intake, central metformin may effectively enhance its glucose-lowering effect through the brain-gut axis, which could surpass its effect on glucose regulation via the brain-liver axis.</p
CdS-CoFe<sub>2</sub>O<sub>4</sub>@Reduced Graphene Oxide Nanohybrid: An Excellent Electrode Material for Supercapacitor Applications
CoFe<sub>2</sub>O<sub>4</sub> nanospheres
ornamented CdS nanorods
were successfully assembled over the reduced graphene oxide nanosheets.
Such hierarchical morphology established by field emission scanning
electron microscopy and transmission electron microscopy studies,
with high surface area offered a high specific capacitance of 1487
F g<sup>–1</sup> at a current density of 5 A g<sup>–1</sup> owing to fast diffusion of ions, facile transportation of electrons,
and great synergism between the components, which led to reversible
redox reactions. Furthermore, the electrode material has specific
capacitance retention of 78% up to 5000 cycles, thus demonstrating
its good reversibility and cyclic stability. The resulting CdS-CoFe<sub>2</sub>O<sub>4</sub>@reduced graphene oxide nanohybrid can deliver
excellent electrochemical performance and can be a potential candidate
for supercapacitor application
Body Mass Index and Mortality in the General Population and in Subjects with Chronic Disease in Korea: A Nationwide Cohort Study (2002-2010)
<div><p>Background</p><p>The association between body mass index (BMI) and mortality is not conclusive, especially in East Asian populations. Furthermore, the association has been neither supported by recent data, nor assessed after controlling for weight changes.</p><p>Methods</p><p>We evaluated the relationship between BMI and all-cause or cause-specific mortality, using prospective cohort data by the National Health Insurance Service in Korea, which consisted of more than one million subjects. A total of 153,484 Korean adults over 30 years of age without pre-existing cardiovascular disease or cancer at baseline were followed-up until 2010 (mean follow-up period = 7.91 ± 0.59 years). Study subjects repeatedly measured body weight 3.99 times, on average.</p><p>Results</p><p>During follow-up, 3,937 total deaths occurred; 557 deaths from cardiovascular disease, and 1,224 from cancer. In multiple-adjusted analyses, U-shaped associations were found between BMI and mortality from any cause, cardiovascular disease, and cancer after adjustment for age, sex, smoking status, alcohol consumption, physical activity, socioeconomic status, and weight change. Subjects with a BMI < 23 kg/m<sup>2</sup> and ≥ 30 kg/m<sup>2</sup> had higher risks of all-cause and cause-specific mortality compared with the reference group (BMI 23–24.9 kg/m<sup>2</sup>). The lowest risk of all-cause mortality was observed in subjects with a BMI of 25–26.4 kg/m<sup>2</sup> (adjusted hazard ratio [HR] 0.86; 95% CI 0.77 to 0.97). In subgroup analyses, including the elderly and those with chronic diseases (diabetes mellitus, hypertension, and chronic kidney disease), subjects with a BMI of 25–29.9 kg/m<sup>2</sup> (moderate obesity) had a lower risk of mortality compared with the reference. However, this association has been attenuated in younger individuals, in those with higher socioeconomic status, and those without chronic diseases.</p><p>Conclusion</p><p>Moderate obesity was associated more strongly with a lower risk of mortality than with normal, underweight, and overweight groups in the general population of South Korea. This obesity paradox was prominent in not only the elderly but also individuals with chronic disease.</p></div
U-shaped association between sleep duration and urinary albumin excretion in Korean adults: 2011-2014 Korea National Health and Nutrition Examination Survey
<div><p>Although sleep duration has been extensively studied in metabolic diseases, few studies have investigated the impact of sleep duration on chronic kidney disease. The aim of this study was to examine the relationship between sleep duration and albuminuria in the general population. Among 24,948 adults who participated in the 2011–2014 KNHANES, a total of 19,994 subjects were included in this analysis. Subjects were categorized into the following five groups according to self-reported sleep duration: less than 5 h, 6 h, 7 h, 8 h, and more than 9 h. The association between sleep duration and urinary albumin-creatinine ratio (UACR) was examined cross-sectionally. Subjects with both short and long sleep durations were significantly associated with higher UACR levels and higher proportions of patients with microalbuminuria (30–299 mg/g) and macroalbuminuria (≥300 mg/g) compared to those with a sleep duration of 7 hours. The U-shaped association between sleep duration and UACR remained significant even after adjustment for potential confounders, including age, sex, body mass index, smoking, alcohol, education, income, exercise, estimated glomerular filtration rate, diabetes mellitus, hypertension and hypercholesterolemia. The U-shaped association is more evident in the subgroup aged 65 or older, or in female subjects. Our findings suggest that both short and long sleep durations have a U-shaped association with UACR levels in the general population, independent of potential confounders.</p></div
Clinical characteristics of study subjects according to sleep duration.
<p>Clinical characteristics of study subjects according to sleep duration.</p