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1.
Front Neurorobot ; 17: 1203962, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-37304664

RESUMEN

As a type of biometric recognition, palmprint recognition uses unique discriminative features on the palm of a person to identify his/her identity. It has attracted much attention because of its advantages of contactlessness, stability, and security. Recently, many palmprint recognition methods based on convolutional neural networks (CNN) have been proposed in academia. Convolutional neural networks are limited by the size of the convolutional kernel and lack the ability to extract global information of palmprints. This paper proposes a framework based on the integration of CNN and Transformer-GLGAnet for palmprint recognition, which can take advantage of CNN's local information extraction and Transformer's global modeling capabilities. A gating mechanism and an adaptive feature fusion module are also designed for palmprint feature extraction. The gating mechanism filters features by a feature selection algorithm and the adaptive feature fusion module fuses them with the features extracted by the backbone network. Through extensive experiments on two datasets, the experimental results show that the recognition accuracy is 98.5% for 12,000 palmprints in the Tongji University dataset and 99.5% for 600 palmprints in the Hong Kong Polytechnic University dataset. This demonstrates that the proposed method outperforms existing methods in the correctness of both palmprint recognition tasks. The source codes will be available on https://github.com/Ywatery/GLnet.git.

2.
Heliyon ; 8(5): e09482, 2022 May.
Artículo en Inglés | MEDLINE | ID: mdl-35620623

RESUMEN

Reducing the incidence of obesity is the focus of global attention, and traditional Chinese medicine (TCM) may play an important role in achieving this goal. Numerous studies have shown that most individuals with obesity have leptin resistance, exogenous leptin is ineffective in individuals with obesity, and the effect of leptin decreases with increased serum leptin levels in individuals with obesity. At present, there are many hypotheses regarding the mechanism of leptin resistance, but there is no definite conclusion. TCM has a long history of treating obesity, and single and compound TCM is an effective obesity treatment method. However, TCM's mechanism of action is complex and resists further weight loss drug development. In the last decade, network pharmacology has become an important tool for exploring the mechanism of compound TCMs. In this study, we reviewed the interrelation between TCM obesity treatment and leptin resistance, and network pharmacology studies of TCM intervention in simple obesity revealed that their targets overlap with the leptin pathway. We also summarized TCM pairs that effectively interfere with leptin resistance and their related intervention mechanisms, providing targets for anti-obesity drug development.

3.
Trials ; 21(1): 951, 2020 Nov 23.
Artículo en Inglés | MEDLINE | ID: mdl-33228726

RESUMEN

BACKGROUND: Diabetic kidney disease (DKD) is one of the most important microvascular complications of diabetes, and its prevalence has increased dramatically in the past few decades. DKD is responsible for considerable morbidity and mortality of patients with diabetes. Keluoxin capsule (KLX) is a Chinese patent medicine that has been used in the clinic to control DKD for years. Previous studies have shown that KLX appears to reduce proteinuria, but the study protocols as well as the primary outcome need to be improved. Thus, we aim to evaluate whether losartan potassium combined with KLX is more effective than losartan potassium in DKD treatment and to provide validated evidence for the application of KLX in the treatment of DKD. METHODS: We will conduct a randomized double-blind placebo-controlled multicenter clinical trial. A total of 252 participants diagnosed with DKD recruited from 18 institutions will be randomly allocated to either a losartan potassium plus KLX (n = 126) or a losartan potassium plus placebo group (n = 126). The participants will be administered KLX or placebo in addition to losartan potassium for 24 weeks. The primary outcome measure will be the decline in estimated glomerular filtration rate (eGFR) (ml/min/1.73 m2/year) from baseline within 24 weeks, and the secondary outcomes will be the incidence of serum creatinine doubling, the incidence of end-stage renal disease (ESRD), the proportion of subjects with a progressive decline in eGFR > 30%, the percent change in 24 h urinary total protein (UTP), the change in the urinary albumin/creatinine ratio (UACR), and the total effective rate of the traditional Chinese medicine (TCM) syndrome scale scores. Comparison of the differences in the variables between groups will be performed according to the data revealed by independent t tests, chi-squared tests, Fisher's exact tests, or Wilcoxon's tests. All statistical tests will be two-sided, and significance will be considered for p values < 0.05. DISCUSSION: This study will be the first randomized clinical trial to evaluate the efficacy and safety of KLX versus the placebo for the treatment of patients with DKD. The outcome of this trial will provide a basis for prescribing KLX to patients with DKD. TRIAL REGISTRATION: Chinese Clinical Trial Registry ( www.chictr.org.cn ) ChiCTR1900021113. Registered on January 29, 2019.


Asunto(s)
Diabetes Mellitus , Nefropatías Diabéticas , Medicamentos Herbarios Chinos , Nefropatías Diabéticas/diagnóstico , Nefropatías Diabéticas/tratamiento farmacológico , Método Doble Ciego , Medicamentos Herbarios Chinos/efectos adversos , Tasa de Filtración Glomerular , Humanos , Losartán/efectos adversos , Estudios Multicéntricos como Asunto , Ensayos Clínicos Controlados Aleatorios como Asunto , Resultado del Tratamiento
4.
Front Endocrinol (Lausanne) ; 11: 560157, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-33569041

RESUMEN

Graves' disease is the most common cause of hyperthyroidism. Antithyroid drugs, radioiodine ablation, and surgery are the main treatments. Research has demonstrated that adding thyroxine to antithyroid therapy can improve the remission rate, and many similar studies have been conducted subsequently. The purpose of this systematic review was to investigate whether adding thyroxine to various treatments for Graves' disease has a clinical benefit in remission/relapse rate, stable thyroid function, occurrence of Graves' ophthalmopathy, etc. A total of 27 studies were included, and the risk of research bias was moderate to high. We discuss the role of thyroxine both in pharmacological and non-pharmacological therapeutic regimens. Overall, the available evidence does not support the indiscriminate addition of thyroxine to various treatments for Graves' disease, especially in combination with oral antithyroid drugs. Further clinical studies are required to explore the indications of thyroxine addition in the treatment of Graves' disease.


Asunto(s)
Antitiroideos/administración & dosificación , Enfermedad de Graves/tratamiento farmacológico , Tiroxina/administración & dosificación , Animales , Quimioterapia Combinada , Enfermedad de Graves/diagnóstico , Enfermedad de Graves/metabolismo , Oftalmopatía de Graves/diagnóstico , Oftalmopatía de Graves/tratamiento farmacológico , Oftalmopatía de Graves/metabolismo , Humanos , Resultado del Tratamiento
5.
Front Pharmacol ; 10: 661, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-31258478

RESUMEN

Insulin resistance is a condition in which insulin sensitivity is reduced and the insulin signaling pathway is impaired. Although often expressed as an increase in insulin concentration, the disease is characterized by a decrease in insulin action. This increased workload of the pancreas and the consequent decompensation are not only the main mechanisms for the development of type 2 diabetes (T2D), but also exacerbate the damage of metabolic diseases, including obesity, nonalcoholic fatty liver disease, polycystic ovary syndrome, metabolic syndrome, and others. Many clinical trials have suggested the potential role of herbs in the treatment of insulin resistance, although most of the clinical trials included in this review have certain flaws and bias risks in their methodological design, including the generation of randomization, the concealment of allocation, blinding, and inadequate reporting of sample size estimates. These studies involve not only the single-flavored herbs, but also herbal formulas, extracts, and active ingredients. Numerous of in vitro and in vivo studies have pointed out that the role of herbal medicine in improving insulin resistance is related to interventions in various aspects of the insulin signaling pathway. The targets involved in these studies include insulin receptor substrate, phosphatidylinositol 3-kinase, glucose transporter, AMP-activated protein kinase, glycogen synthase kinase 3, mitogen-activated protein kinases, c-Jun-N-terminal kinase, nuclear factor-kappaB, protein tyrosine phosphatase 1B, nuclear factor-E2-related factor 2, and peroxisome proliferator-activated receptors. Improved insulin sensitivity upon treatment with herbal medicine provides considerable prospects for treating insulin resistance. This article reviews studies of the target mechanisms of herbal treatments for insulin resistance.

6.
J Telemed Telecare ; 25(2): 93-105, 2019 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-29228855

RESUMEN

BACKGROUND: Mobile health interventions utilising telephone calls are promising tools for diabetes management. However, there is still a lack of convincing evidence demonstrating their beneficial effects on cardiovascular risk factors. The aim of this meta-analysis of randomised controlled trials was to assess the effect of telephone calls on glycaemic control and other cardiovascular risk factors in type 2 diabetes mellitus patients. METHODS: Two independent reviewers searched three online databases (PubMed, the Cochrane Library and EMBASE) to identify relevant English-language randomised controlled trials up to September 2017. Randomised controlled trials that assessed the effects of telephone calls on glycaemic control and other cardiovascular risk factors in type 2 diabetes mellitus patients were included. Effect size was calculated for changes in glycosylated haemoglobin A1c, weight, blood pressure and lipid levels using fixed- or random-effects models. RESULTS: Eighteen studies involving 3954 patients were included in the meta-analysis. Compared with usual care, telephone calls significantly decreased glycosylated haemoglobin A1c, by 0.12% (95% confidence interval: -0.22% to -0.02%). Univariate regression analysis showed that none of the covariates (number of participants, baseline age, baseline glycosylated haemoglobin A1c, duration of diabetes, call maker, number of calls and duration of study) had an impact on glycosylated haemoglobin A1c. For other cardiovascular risk factors, telephone calls significantly reduced systolic blood pressure by 0.19 mm Hg (95% confidence interval: -0.34% to -0.03%) but non-significantly changed diastolic blood pressure, body mass index, low-density lipoprotein cholesterol, total cholesterol, triglyceride or high-density cholesterol levels. CONCLUSIONS: This meta-analysis supports the hypothesis that telephone calls offer moderate benefits for glycosylated haemoglobin A1c and systolic blood pressure reduction among type 2 diabetes mellitus patients. However, the data remain insufficient regarding the association of telephone calls with lowered diastolic blood pressure, body mass index or improved lipoprotein profiles.


Asunto(s)
Enfermedades Cardiovasculares/epidemiología , Enfermedades Cardiovasculares/prevención & control , Diabetes Mellitus Tipo 2/epidemiología , Autocuidado/métodos , Teléfono , Factores de Edad , Glucemia , Presión Sanguínea , Peso Corporal , Hemoglobina Glucada , Humanos , Ensayos Clínicos Controlados Aleatorios como Asunto , Factores de Riesgo , Factores Sexuales
7.
Medicine (Baltimore) ; 97(45): e13183, 2018 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-30407354

RESUMEN

INTRODUCTION: Mild subclinical hypothyroidism (SCH) can cause depression, fatigue, cognitive dysfunction, or other hypothyroid symptoms, and even progress to hypothyroidism. The treatment of mild SCH is controversial. Shuganjianpihuatanxingqi decoction (SD) is a frequently prescribed Chinese herbal medicine in patients with mild SCH. However, scientific evidence is needed to confirm the therapeutic effect of SD. METHODS AND ANALYSIS: This study is a randomized, double-blind, and controlled clinical trial. A total of 228 participants with the diagnosis of mild SCH will be randomly assigned to the SD or placebo group in a ratio of 1:1. Participants will receive treatment for 12 weeks and undergo 12-month follow-up. The primary outcome measure is the thyroid-stimulating hormone level, and secondary outcomes will be the differences in the results of Thyroid-related Quality of Life Questionnaire, blood lipids, and Traditional Chinese Medicine Symptom Score Scale between baseline and at 12 weeks after intervention. ETHICS AND DISSEMINATION: The study has been approved by Guang'anmen Hospital of China Academy of Chinese Medical Sciences (no.2018-005-ky-01). The trial results will be published via peer-reviewed journals and the Clinical Research Information Service. TRIAL REGISTRATION NUMBER: ChiCTR1800015781 (approval date: 20 April 2018).


Asunto(s)
Medicamentos Herbarios Chinos/uso terapéutico , Hipotiroidismo/tratamiento farmacológico , Adolescente , Adulto , Anciano , China , Método Doble Ciego , Medicamentos Herbarios Chinos/efectos adversos , Estudios de Seguimiento , Humanos , Lípidos/sangre , Persona de Mediana Edad , Calidad de Vida , Índice de Severidad de la Enfermedad , Tirotropina/sangre , Resultado del Tratamiento , Adulto Joven
8.
Front Pharmacol ; 9: 423, 2018.
Artículo en Inglés | MEDLINE | ID: mdl-29765322

RESUMEN

Ginseng, one of the oldest traditional Chinese medicinal herbs, has been used widely in China and Asia for thousands of years. Ginsenosides extracted from ginseng, which is derived from the roots and rhizomes of Panax ginseng C. A. Meyer, have been used in China as an adjuvant in the treatment of diabetes mellitus. Owing to the technical complexity of ginsenoside production, the total ginsenosides are generally extracted. Accumulating evidence has shown that ginsenosides exert antidiabetic effects. In vivo and in vitro tests revealed the potential of ginsenoside Rg1, Rg3, Rg5, Rb1, Rb2, Rb3, compound K, Rk1, Re, ginseng total saponins, malonyl ginsenosides, Rd, Rh2, F2, protopanaxadiol (PPD) and protopanaxatriol (PPT)-type saponins to treat diabetes and its complications, including type 1 diabetes mellitus, type 2 diabetes mellitus, diabetic nephropathy, diabetic cognitive dysfunction, type 2 diabetes mellitus with fatty liver disease, diabetic cerebral infarction, diabetic cardiomyopathy, and diabetic erectile dysfunction. Many effects are attributed to ginsenosides, including gluconeogenesis reduction, improvement of insulin resistance, glucose transport, insulinotropic action, islet cell protection, hepatoprotective activity, anti-inflammatory effect, myocardial protection, lipid regulation, improvement of glucose tolerance, antioxidation, improvement of erectile dysfunction, regulation of gut flora metabolism, neuroprotection, anti-angiopathy, anti-neurotoxic effects, immunosuppression, and renoprotection effect. The molecular targets of these effects mainly contains GLUTs, SGLT1, GLP-1, FoxO1, TNF-α, IL-6, caspase-3, bcl-2, MDA, SOD, STAT5-PPAR gamma pathway, PI3K/Akt pathway, AMPK-JNK pathway, NF-κB pathway, and endoplasmic reticulum stress. Rg1, Rg3, Rb1, and compound K demonstrated the most promising therapeutic prospects as potential adjuvant medicines for the treatment of diabetes. This paper highlights the underlying pharmacological mechanisms of the anti-diabetic effects of ginsenosides.

9.
J Food Drug Anal ; 24(4): 839-847, 2016 10.
Artículo en Inglés | MEDLINE | ID: mdl-28911623

RESUMEN

Plant tissue culture technique is widely used in the conservation and utilization of rare and endangered medicinal plants and it is crucial for tissue culture stocks to obtain the ability to produce similar bioactive components as their wild correspondences. In this paper, a headspace gas chromatography-mass spectrometry method combined with chemometric methods was applied to analyze and evaluate the volatile compounds in tissue-cultured and wild Dendrobium huoshanense Cheng and Tang, Dendrobium officinale Kimura et Migo and Dendrobium moniliforme (Linn.) Sw. In total, 63 volatile compounds were separated, with 53 being identified from the three Dendrobium spp. SAMPLES: Different provenances of Dendrobiums had characteristic chemicals and showed remarkable quantity discrepancy of common compositions. The similarity evaluation disclosed that the accumulation of volatile compounds in Dendrobium samples might be affected by their provenance. Principal component analysis showed that the first three components explained 85.9% of data variance, demonstrating a good discrimination between samples. Gas chromatography-mass spectrometry techniques, combined with chemometrics, might be an effective strategy for identifying the species and their provenance, especially in the assessment of tissue-cultured Dendrobium quality for use in raw herbal medicines.


Asunto(s)
Dendrobium , Técnicas de Cultivo , Medicamentos Herbarios Chinos , Cromatografía de Gases y Espectrometría de Masas , Plantas Medicinales , Polisacáridos , Análisis de Componente Principal , Técnicas de Cultivo de Tejidos , Compuestos Orgánicos Volátiles
10.
Curr Drug Targets ; 16(13): 1531-9, 2015.
Artículo en Inglés | MEDLINE | ID: mdl-26201489

RESUMEN

Acute lung injury (ALI) and its most severe manifestation, acute respiratory distress syndrome (ARDS), is a clinical syndrome defined by acute hypoxemic respiratory failure and bilateral pulmonary infiltrates consistent with edema. In-hospital mortality is 38.5% for AL, and 41.1% for ARDS. Activation of alveolar macrophages in the donor lung causes the release of pro-inflammatory chemokines and cytokines, such as TNF-α. To determine the relevance of TNF-α in disrupting bronchial endothelial cell function, we stimulated human THP-1 macrophages with lipopolysaccharide (LPS) and used the resulting cytokine-supplemented media to disrupt normal endothelial cell functions. Endothelial tube formation was disrupted in the presence of LPS-activated THP- 1 conditioned media, with reversal of the effect occurring in the presence of 0.1µg/ml Enbrel, indicating that TNF-α was the major serum component inhibiting endothelial tube formation. To facilitate lung conditioning, we tested liposomal and porous silicon (pSi) delivery systems for their ability to selectively silence TNFR1 using siRNA technology. Of the three types of liposomes tested, only cationic liposomes had substantial endothelial uptake, with human cells taking up 10-fold more liposomes than their pig counterparts; however, non-specific cellular activation prohibited their use as immunosuppressive agents. On the other hand, pSi microparticles enabled the accumulation of large amounts of siRNA in endothelial cells compared to standard transfection with Lipofectamine(®) LTX, in the absence of non-specific activation of endothelia. Silencing of TNFR1 decreased TNF-α mediated inhibition of endothelial tube formation, as well as TNF-α-induced upregulation of ICAM-1, VCAM, and E-selection in human lung microvascular endothelial cells.


Asunto(s)
Lesión Pulmonar Aguda/fisiopatología , ARN Interferente Pequeño/administración & dosificación , Receptores Tipo I de Factores de Necrosis Tumoral/genética , Síndrome de Dificultad Respiratoria/fisiopatología , Animales , Cationes/metabolismo , Citocinas/metabolismo , Selectina E/genética , Células Endoteliales/metabolismo , Silenciador del Gen , Humanos , Molécula 1 de Adhesión Intercelular/genética , Lipopolisacáridos/farmacología , Liposomas , Macrófagos/metabolismo , Microvasos/citología , Microvasos/metabolismo , Especificidad de la Especie , Porcinos , Factor de Necrosis Tumoral alfa/metabolismo , Regulación hacia Arriba/genética , Molécula 1 de Adhesión Celular Vascular/genética
11.
Clin Cancer Res ; 19(7): 1806-15, 2013 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-23386691

RESUMEN

PURPOSE: RNA interference has the potential to specifically knockdown the expression of target genes and thereby transform cancer therapy. However, lack of effective delivery of siRNA has dramatically limited its in vivo applications. We have developed a multistage vector (MSV) system, composed of discoidal porous silicon particles loaded with nanotherapeutics, that directs effective delivery and sustained release of siRNA in tumor tissues. In this study, we evaluated therapeutic efficacy of MSV-loaded EphA2 siRNA (MSV/EphA2) with murine orthotopic models of metastatic ovarian cancers as a first step toward development of a new class of nanotherapeutics for the treatment of ovarian cancer. EXPERIMENTAL DESIGN: Tumor accumulation of MSV/EphA2 and sustained release of siRNA from MSV were analyzed after intravenous administration of MSV/siRNA. Nude mice with metastatic SKOV3ip2 tumors were treated with MSV/EphA2 and paclitaxel, and therapeutic efficacy was assessed. Mice with chemotherapy-resistant HeyA8 ovarian tumors were treated with a combination of MSV/EphA2 and docetaxel, and enhanced therapeutic efficacy was evaluated. RESULTS: Treatment of SKOV3ip2 tumor mice with MSV/EphA2 biweekly for 6 weeks resulted in dose-dependent (5, 10, and 15 µg/mice) reduction of tumor weight (36%, 64%, and 83%) and number of tumor nodules compared with the control groups. In addition, tumor growth was completely inhibited when mice were treated with MSV/EphA2 in combination with paclitaxel. Furthermore, combination treatment with MSV/EphA2 and docetaxel inhibited growth of HeyA8-MDR tumors, which were otherwise resistant to docetaxel treatment. CONCLUSION: These findings indicate that MSV/EphA2 merits further development as a novel therapeutic agent for ovarian cancer.


Asunto(s)
Silenciador del Gen , Vectores Genéticos/genética , Receptor EphA2/genética , Animales , Antineoplásicos/administración & dosificación , Antineoplásicos/farmacología , Carcinoma Epitelial de Ovario , Línea Celular Tumoral , Relación Dosis-Respuesta a Droga , Resistencia a Antineoplásicos/genética , Femenino , Vectores Genéticos/administración & dosificación , Vectores Genéticos/química , Humanos , Liposomas , Ratones , Nanopartículas/química , Nanopartículas/ultraestructura , Neoplasias Glandulares y Epiteliales/genética , Neoplasias Glandulares y Epiteliales/patología , Neoplasias Glandulares y Epiteliales/terapia , Neoplasias Ováricas/genética , Neoplasias Ováricas/patología , Neoplasias Ováricas/terapia , Interferencia de ARN , ARN Interferente Pequeño/administración & dosificación , Silicio/química , Carga Tumoral/efectos de los fármacos , Carga Tumoral/genética , Ensayos Antitumor por Modelo de Xenoinjerto
12.
Cancer Lett ; 334(2): 245-52, 2013 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-22858582

RESUMEN

Adequate drug delivery to tumors is hindered by barriers such as degradation and non-specific distribution. Nested incorporation of drug-containing nanoparticles within mesoporous silicon particles (MSVs), carriers rationally designed to enhance tumor transport, was hypothesized to result in pronounced and sustained antitumor efficacy. Paclitaxel (PTX)-containing poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-PCL) polymer micelles were favorably loaded within MSVs, after which drug release was significantly delayed. Antitumor efficacy analyses in mice bearing MDA-MB-468 breast tumors demonstrated significant tumor growth suppression following a single administration. Results highlight effective chemotherapeutic shuttling and site-specific controlled release afforded by MSVs, potentially translating towards improvements in patient outcomes and morbidity.


Asunto(s)
Antineoplásicos/administración & dosificación , Neoplasias de la Mama/tratamiento farmacológico , Sistemas de Liberación de Medicamentos/métodos , Nanopartículas/administración & dosificación , Animales , Antineoplásicos/farmacocinética , Neoplasias de la Mama/metabolismo , Portadores de Fármacos/administración & dosificación , Femenino , Humanos , Células MCF-7 , Ratones , Ratones Desnudos , Micelas , Nanopartículas/metabolismo , Distribución Aleatoria , Ensayos Antitumor por Modelo de Xenoinjerto
13.
Adv Healthc Mater ; 1(1): 84-9, 2012 Jan 11.
Artículo en Inglés | MEDLINE | ID: mdl-23184690

RESUMEN

Hollow gold nanoshells are more efficient in heat generation triggered by near infrared laser when they are loaded into porous silicon particles, which results in effective cancer-cell killing in vitro and in vivo. Collective electromagnetic coupling of nanoconfined hollow gold nanoshells leads to dramatic enhancement of thermal ablation.


Asunto(s)
Hipertermia Inducida/métodos , Nanopartículas/química , Nanopartículas/uso terapéutico , Neoplasias Experimentales/patología , Neoplasias Experimentales/terapia , Animales , Línea Celular Tumoral , Ratones , Nanopartículas/ultraestructura , Tamaño de la Partícula , Resultado del Tratamiento
14.
J Nanosci Nanotechnol ; 12(3): 2634-9, 2012 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-22755101

RESUMEN

As one of the most heavily used starting materials in metallic nanostructure syntheses, PVP has made a series of revolutionary successes. However, the true role of PVP still has not been fully understood. Herein, designed reactions and NMR analyses have been done to prove the redox reaction in PVP-mediated synthesis of metallic nanomaterials. As metal ions are reduced, alpha-pyrrolidone rings of PVP are partially oxidized and form poly(vinyl(pyrrolidone)x-(succinimide)y), which has a crucial surface modification capability for nanocrystals. This new finding provides insight into how PVP manipulates the structures and morphologies by modifying the reaction rate and stabilizing the nanocrystals.


Asunto(s)
Metales/química , Nanoestructuras , Povidona/química , Espectroscopía de Resonancia Magnética , Microscopía Electrónica de Transmisión , Modelos Moleculares
15.
J Nanosci Nanotechnol ; 10(8): 5089-92, 2010 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-21125854

RESUMEN

We describe an approach to synthesize monodisperse CoPt nanoparticles with dendrimer as template by a simple chemical reduction method in aqueous solution using NaBH4 as reducing agent at room temperature. The as-made CoPt nanoparticles buried in the dendrimer matrix have the chemically disordered fcc structure and can be transformed to the fct phase after annealing at 700 degrees C. This is the first report of dendrimer-mediated room temperature synthesis of monodisperse magnetic nanoparticles in aqueous solution.

16.
ACS Appl Mater Interfaces ; 1(10): 2304-11, 2009 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-20355866

RESUMEN

Monodisperse polymer-mediated platinum (Pt) nanoparticles (NPs) have been synthesized by photoreduction in the presence of poly(ethylenimine) (PEI), a hyperbranched polymer. The formation process of the Pt NPs is pursued by UV-vis spectroscopy, and the formation mechanism is discussed. The morphology and size of the Pt NPs were characterized by transmission electron microscopy (TEM). TEM imaging shows that the Pt NPs' average diameter is 2.88 +/- 0.53 nm. The PEI/Pt NPs were immobilized on glassy carbon electrodes, and the electrocatalytic activity of the catalysts was investigated by cyclic voltammetry. PEI/Pt NPs exhibit very high catalytic activity for a methanol oxidation reaction. PEI/Pt NPs on glassy carbon electrodes are robust, showing good tolerance to poisoning even after many cycles. The electrocatalytic activity of PEI/Pt NPs compares favorably with other polymer-mediated Pt NPs. The results indicate that PEI is an appropriate complexing reducing agent for the photochemical production of Pt NPs and a good capping agent, allowing immobilization of the NPs on the working electrode.

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