Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 22
Filtrar
Más filtros










Base de datos
Intervalo de año de publicación
1.
Int J Biol Macromol ; 273(Pt 1): 132803, 2024 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-38848836

RESUMEN

Bionanocomposites offer a promising solution to the plastic waste crisis. Although tapioca starch shows potential as a bioplastic material, it is characterized by low mechanical properties, poor thermal stability, and high water absorption owing to its hydrophilic nature. To increase the flexibility of the material and reduce the transmission rate of oxygen and water vapor, additives such as fructose and titanium dioxide (TiO2) can be incorporated into the material. TiO2 nanoparticles are commonly utilized in agriculture to enhance nutrient release and promote plant growth. In this study, X-ray diffraction analysis revealed that TiO2 reduced crystal size while increasing the crystallinity of bionanocomposites. Fourier-transform infrared spectroscopy analysis revealed an absorption peak at 3397 cm-1, indicating hydrogen bonding between TiO2 and starch-OH groups, and a peak at 773 cm-1, indicating an increase in the intensity of Ti-O-Ti stretching vibrations with the incorporation of TiO2. Water absorption rate results confirmed that TiO2 addition enhanced bionanocomposite resistance to water vapor and moisture, evidenced by increased tensile strength from 0.11 to 0.49 MPa and Young's modulus from 2.48 to 5.26 MPa, as well as decreased elongation at break from 21.46 % to 2.36 % in bionanocomposites with TiO2. Furthermore, with TiO2 addition, the biodegradation rate of the bionanocomposites decreased, which is beneficial for enhancing plant nutrient content.


Asunto(s)
Embalaje de Alimentos , Fructosa , Manihot , Nanocompuestos , Almidón , Titanio , Nanocompuestos/química , Titanio/química , Almidón/química , Embalaje de Alimentos/métodos , Fructosa/química , Manihot/química , Fertilizantes , Resistencia a la Tracción , Agua/química , Difracción de Rayos X , Espectroscopía Infrarroja por Transformada de Fourier
2.
Int J Biol Macromol ; 265(Pt 1): 130722, 2024 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-38462103

RESUMEN

Keratin was synthesized by alkaline hydrolysis from chicken feathers and then continue by casting method for producing bioplastics with additional various amounts of chitosan as a filler, polyvinyl alcohol (PVA) and glycerol as a plasticizer. The main purpose is analysis the effect of chitosan on the structural properties using quantitative analysis of X-ray diffraction (XRD) spectra, chemical bonding by Fourier transforms infrared (FTIR) spectra, and mechanical properties by texture analyser to the keratin-based bioplastics. Biodegradation of bioplastics was analysed from the loss of weight by burying in the soil. It's found that, the additional of chitosan (0 %, 2 %, 5 %, and 8 %) increased the crystallinity of bioplastics by 11.83 %, 11.12 %, 18.99 %, and 17.03 %, respectively, but decreasing tensile strength and elasticity of bioplastics. Degradation of bioplastic keratin-based shows that the addition of chitosan can reduce the degradation time which is directly proportional to the loss of CO bonds. The highest degradation rate is 89.29 % in 49 days for keratin-based bioplastics with 8 % chitosan, indicated that high potential for future production.


Asunto(s)
Quitosano , Animales , Quitosano/química , Plumas/química , Queratinas/química , Pollos , Citoesqueleto
3.
Bone ; 183: 117075, 2024 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-38508371

RESUMEN

Hydroxyapatite [HA, Ca10(PO4)6(OH)2], with its robust biocompatibility and bioactivity, has found extensive utility in bone grafting, replacement therapies, and supplemental medical materials. HA is highly regarded for its osteoconductive properties because it boasts hydrophilicity, nontoxicity, non-allergenicity, and non-mutagenicity. Nevertheless, HA's intrinsic mechanical weakness has spurred efforts to enhance its properties. This enhancement is achieved through ion incorporation, with elements such as magnesium, zinc, lithium, strontium, boron, and others being integrated into the HA structure. In the domain of orthopedics, HA-based scaffolds have emerged as a solution for addressing prevalent issues like bone deformities and defects stemming from congenital anomalies, injuries, trauma, infections, or tumors. The fabrication of three-dimensional scaffolds (3D scaffolds) has enabled advancements in bone regeneration and replacement, with a focus on practical applications such as repairing calvarial, skull, and femoral defects. In vitro and in vivo assessments have substantiated the effectiveness of 3D scaffolds for bone defect repair, regeneration, and tissue engineering. Beyond bone-related applications, scaffolds demonstrate versatility in enhancing cartilage healing and serving as bioimplants. The wide array of scaffold applications underscores their ongoing potential for further development in the realm of medical science.


Asunto(s)
Durapatita , Andamios del Tejido , Durapatita/química , Andamios del Tejido/química , Regeneración Ósea , Ingeniería de Tejidos/métodos , Cráneo/patología
4.
Int J Biol Macromol ; 256(Pt 2): 128074, 2024 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-37989433

RESUMEN

Bioplastic that is synthesized from natural materials such as chitosan is a renewable solution to reduce plastic waste in the environment because they are easily decomposed. In this study, chitosan (CS) was extracted from Milkfish scales waste to produce composite bioplastic CS/PVA/PEG to determine the effect of CS on the mechanical properties and degradation time. The average particle size of chitin is 8.5 µm and crystallinity of 57.18 % and for CS, the particle size is 3.5 µm and crystallinity of 64.94 %. The degree of deacetylation of CS is 84.1 % which met the quality standard of Indonesian national standard (SNI) Number: 7949:2013. The tensile strength of bioplastics for 0.5 g CS of 0.21 MPa increases to 0.24 MPa for 2 g CS in composite bioplastics CS/PVA/PEG. The biodegradation performance of bioplastic samples takes 72 h to completely decompose in soil for CS-based and in seawater for chitin-based, means that highly recommended to develop in future.


Asunto(s)
Quitosano , Animales , Quitosano/metabolismo , Peces/metabolismo
5.
ACS Omega ; 8(30): 27663-27673, 2023 Aug 01.
Artículo en Inglés | MEDLINE | ID: mdl-37546675

RESUMEN

Activated carbon/GeO2 composites were synthesized using the sol-gel method and then used as catalysts for the photodegradation of organic pollutants methylene blue (MB) and congo red (CR). The composites were characterized using an X-ray diffractometer and Fourier transform infrared spectroscopy to analyze the structure and chemical bonds of the composite materials, respectively. The ultraviolet-visible (UV-vis) absorption wavelength ranges of the composites toward the pollutants were 550-700 nm for MB and 450-550 for CR. The band gap energies of the composites were calculated, with the values found to be <4.5 eV. It was shown that the adsorption ability of the composites increased with the irradiation time of the pollutants. Furthermore, the adsorption kinetics data were found to be a good fit to a pseudo-first-order kinetics model.

6.
ACS Omega ; 8(21): 18591-18602, 2023 May 30.
Artículo en Inglés | MEDLINE | ID: mdl-37273611

RESUMEN

Efforts to produce microwave absorber materials that are inexpensive and environmentally friendly have become a means of greening the environment. The breakthrough can be focused on industrial waste and natural materials for functional purposes and how to enhance their performance. We successfully synthesized nickel slag/laterite soil (NS/LS) and nickel slag/iron sand (NS/IS) nanocomposites using a simple mechanical alloying technique, and the electromagnetic (EM) wave absorption capacities of the nanocomposites were measured using a vector network analyzer. The structural properties of the nanocomposites were analyzed by X-ray diffraction spectroscopy, where the results of the analysis showed that NS/IS has the largest crystallite size (15.69 nm) and the highest EM wave absorption performance. The optical properties of the nanocomposites were determined from their Fourier transform infrared spectra using the Kramers-Kronig relation. As determined through a quantitative analysis of the optical properties, the distance between the longitudinal and transversal optical phonon wavenumber positions (Δ(LO - TO) = 65 cm-1) is inversely proportional to the reflection loss. The surface morphologies of the nanocomposites were analyzed by scanning electron microscopy, and the particle diameters were observed by binary image and Gaussian distribution analyses. The nanocomposite surface exhibits a graded-like morphology, which indicates multiple reflections of the EM radiation, consequently reducing the EM interference. The best nanocomposite for an attenuated EM wave achieved a reflection loss of -39.14 dB at 5-8 GHz. A low penetration depth has implications for the electrical charge tuning of the storage and composite magnets. Finally, the EM absorption properties of NS/IS and NS/LS indicate a 2-mm-thick environmentally friendly nanocomposite for EM absorption.

7.
Environ Monit Assess ; 195(4): 474, 2023 Mar 16.
Artículo en Inglés | MEDLINE | ID: mdl-36928989

RESUMEN

Wastewater has negative impacts on the environment, such as destroying aquatic ecosystems and creating a shortage of clean water sources for consumption. In this paper, we provide a comprehensive bibliometric analysis of chitosan to better understand the evolution in degrading various pollutants as a wastewater treatment research limited only by photocatalyst system published in 2001-2021. The number of publications analyzed a total of 456 documents, which was conducted from the Scopus database. All data in this paper was visualized by using open-source software, VOSviewer and Tableau, to perform bibliometric analysis and scientific mapping. The reason for choosing chitosan is its ability to degrade various pollutants with high adsorption performance (from various sources: degradation Congo red 98.4%, methylene blue 99.36%, rhodamine B 95%, and Cd(II) 94%), non-toxicity, biodegradability, and abundantly available sources in nature. The analysis results show that the highest number of publications in 2016 was 66, and the highest number of citations was 2258. The network of keywords and innovations for wastewater treatment is USA and China as the most productive countries with many cooperative relations. This paper helps scholars understand the evolution of composite chitosan-based photocatalyst systems as research on wastewater treatment from a bibliometric point of view and inspires them to develop new efficient methods in synthesizing chitosan from fish by-products (waste) with high adsorption efficiency for various type of waste.


Asunto(s)
Quitosano , Contaminantes Ambientales , Aguas Residuales , Ecosistema , Monitoreo del Ambiente , Bibliometría
8.
Appl Radiat Isot ; 193: 110626, 2023 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-36640699

RESUMEN

Breast cancer is a common malignancy for females (25% of female cancers) and also has low incidence in males. It was estimated that 1% of all breast malignancies occur in males with mortality rate about 20%, with annual increase in incidence. Risk factors include age, family history, exposure to ionizing radiation and high estrogen and low of androgens hormones level. Diagnosis and screening are challenging due to limiting effectiveness of breast cancer screening. Therefore, patients may expose to ionizing radiation that may contribute in breast cancer incidence in males. In literature, limited studies were published regarding radiation exposure for males during mammography. The objective of this research is to quantify patient doses during male mammogram and to estimate the projected radiogenic risk during the procedure. In total, 42 male patients were undergone mammogram for breast cancer diagnosis during two consecutive years. The mean and range of patient age (years) is 45 (23-80). The mean and standard deviation (SD) of the peak tube potential and tube current time product are 28.64 ± 2. and 149 ± 35.1, respectively. The mean, and range of patients' entrance surface air kerma (ESAK, mGy) per single breast procedure was 5.3 (0.47-27.5). Male patient's received comparable radiation dose per mammogram compared to female procedures. With increasing incidence of male breast cancer, proper guidelines are necessary for the mammographic procedure are necessary to reduce unnecessary radiation doses and radiogenic risk.


Asunto(s)
Neoplasias de la Mama , Exposición a la Radiación , Humanos , Femenino , Masculino , Dosis de Radiación , Mamografía/métodos , Mama/diagnóstico por imagen , Neoplasias de la Mama/patología , Exposición a la Radiación/análisis
9.
Appl Radiat Isot ; 193: 110648, 2023 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-36669265

RESUMEN

Occupational radiation exposure can occur due to various human activities, including the use of radiation in medicine. Occupationally exposed personnel surpassing 7.4 millions, and respresent the biggest single group of employees who are exposed to artificial radiation sources at work. This study compares the occupational radiation dose levels for 145 workers in four different hospitals located in the Aseer region in Saudi Arabia. The occupational exposure was quantified using thermoluminescence dosimeters (TLD-100). The levels of annual occupational exposures in targeted hospitals were calculated and compared with the levels of the international atomic energy agency (IAEA) Safety Standards. An average yearly cumulative dose for the two consecutive years. The average, highest and lowest resulted occupational doses under examination in this work is 1.42, 3.9 mSv and 0.72 for workers in various diagnostic radiology procedures. The resulted annual effective dose were within the IAEA approved yearly dose limit for occupational exposure of workers over 18, which is 20 mSv. Staff should be monitored on a regular basis, according to current practice, because their annual exposure may surpass 15% of the annual effective doses.


Asunto(s)
Exposición Profesional , Exposición a la Radiación , Traumatismos por Radiación , Monitoreo de Radiación , Humanos , Monitoreo de Radiación/métodos , Dosis de Radiación , Radiografía , Exposición Profesional/análisis
10.
Int J Biol Macromol ; 228: 138-152, 2023 Feb 15.
Artículo en Inglés | MEDLINE | ID: mdl-36543298

RESUMEN

Wounds can cause many disorders and affect the quality of health, so it is necessary to develop wound dressings that have a role in accelerating the healing process. Wound dressings have evolved over time, and today there are many types of wound dressings that can suit the type of wound the patient has. This review discusses the development, types, and research directions of wound dressings from calcium alginate (CaAlg), using bibliometric analysis with time intervals from 1982 to 2021. It was found that, in the late 1990s, research related to this matter began to increase. United Kingdom, United States, China, Japan, and Italy are the five most influential countries. And from the results of the keyword analysis, it was found that, in addition to studying the general properties of wound dressings, currently there are many developments related to the structure of the material as well as the effect of adding drugs to wound dressings, so that the current study also displays various characterizations.


Asunto(s)
Alginatos , Vendas Hidrocoloidales , Humanos , Alginatos/uso terapéutico , Cicatrización de Heridas , Bibliometría , China
11.
Appl Radiat Isot ; 192: 110610, 2023 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-36525913

RESUMEN

In comparison to adults and paediatric are more sensitive to ionizing radiation exposure. Computed tomography (CT) is now the dominant source of medical radiologic tests for patients, accounting for more than 70% of total doses to the general public. Paediatric CT brain scans (with and without contrast) are routinely performed for a variety of clinical reasons. As a result, this parameter must be calculated in order to determine relative radiation risk. The goal of this study is to assess the radiation risk to children during CT brain diagnostic procedures. Three hundred fifty three child patients' radiation risk doses were assessed over the course of a year. The mean and ranged of the children's radiation doses were 40.6 ± 8.8 (27.8-45.8) CTDIvol (mGy) and 850 ± 230 (568.1-1126.4) DLP (mGy.cm) for the brain with contrast medium. For CT brain without contrast, the patients' doses were 40.9 ± 9.4 (14.27-64.07) CTDIvol (mGy), and 866.1 ± 289.3 (203.6-2484.9) DLP (mGy.cm). The characteristics related to the radiation dose were retrieved from the scan protocol generated by the CT system by the participating physicians after each procedure. Furthermore, optimizing the CT acquisition parameter is critical for increasing the benefit while lowering the procedure's radiogenic risk. The patients' radiation dose is comparable with the most previously published studies and international diagnostic reference levels (DRLs). Radiation dose optimization is recommended due to high sensitivity of the paediatric patients to ionizing radiation.


Asunto(s)
Angiografía por Tomografía Computarizada , Tomografía Computarizada por Rayos X , Adulto , Humanos , Niño , Dosis de Radiación , Tomografía Computarizada por Rayos X/métodos , Cabeza , Encéfalo/diagnóstico por imagen , Valores de Referencia
12.
Int J Biol Macromol ; 224: 125-132, 2023 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-36257365

RESUMEN

ZnO/chitosan coated wool fabric has been applied as a self-cleaning which obtained through sol-gel method for various pH: 5, 7, and 9. The self-cleaning test was carried out by irradiating the cloth samples using UVA-UVB lamps up to 15 h with dye for the clothing stain. ZnO/chitosan composites were characterized using X-Ray Diffraction (XRD), Fourier Transform Infra-Red (FTIR), and UV-Visible spectroscopy. The diffraction spectra from chitosan for pH 9 is 19.56°. The vibration bond at the wavenumbers 422 cm-1- 621 cm-1 identified as ZnO bond and at the wavenumber 3495 cm-1 identified for stretching -OH and -NH2 from chitosan. Optical properties were analysed using the Kamers Kronig (KK) relation which was applied to the FTIR spectra and shows the highest distance between two optical photon vibration modes (∆ (LO-TO)) is 199 cm-1 was obtained when the pH 9. The pH 9 is the best self-cleaning performance for dye stain which completely lost after being exposed for 15 h irradiation. Samples pH 9 shows the best self-cleaning due to the smallest crystallite size and highest bandgap and (∆ (LO-TO)) indicated high potential for new self-cleaning material in future.


Asunto(s)
Quitosano , Nanocompuestos , Óxido de Zinc , Óxido de Zinc/química , Quitosano/química , Electrones , Luz , Colorantes/química , Nanocompuestos/química , Espectroscopía Infrarroja por Transformada de Fourier , Difracción de Rayos X
13.
Sci Rep ; 12(1): 19169, 2022 Nov 10.
Artículo en Inglés | MEDLINE | ID: mdl-36357772

RESUMEN

Composite cement/BaSO4/Fe3O4/CuO with a thickness of 0.6 cm for various amounts of CuO: 2 wt%, 4 wt%, 6 wt%, and 8 wt% were successfully synthesized for the X-ray radiation shield. The bonding characteristics of composite and structural properties were determined using Fourier transform infrared spectra for the wavelength range of 4000-400 cm-1 and X-ray diffraction with the range of 2θ from 25° to 50°, respectively. The shielding ability was measured using a mobile X-ray with an energy of 55, 66, and 77 keV for determining the mass and linear attenuation coefficient, electronic and atomic cross-section. These shield characteristics best agreement with theoretical calculation from the XCOM database for energy < 77 keV with half value layer (HVL) < 0.3 cm. The best shielding in this study indicated by the lowest HVL and MFP is composite for CuO 8 wt%. The HVL and MFP shows better values compared to the previous reported using composite rubber-based, indicated high potentials composite in this study for design new and efficient radiology rooms as an alternative concrete, especially for X-ray radiation, in the future.

14.
Luminescence ; 37(12): 2006-2017, 2022 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-36136299

RESUMEN

High-photoluminescence carbon dots (CDs) were synthesized from various sources and various methods using two approaches, namely bottom up and top down, with emission-dependent excitation wavelength. Electronic transition from the higher-occupied molecular orbital (HOMO) state to the lowest-unoccupied molecular orbital(LUMO) state, surface defect states, wider excitation spectrum, higher quantum yield, efficient energy transfer, and element doping affected the fluorescence properties of CDs. Using 102 references listed in this review, the authors studied the relationship between fluorescence mechanism and reactive oxygen species (ROS) produced for photodynamic therapy (PDT) and materials anticancer applications. We described how the radical atom or ROS work as anticancer therapy and PDT and described the chemical reaction of high-resolution fluorescence CDs. We summarized experimental techniques that are used for producing CDs and discussed their characteristics. Finally, conclusions and future prospects in this field are also discussed. The important characteristics of CD-based design for high ROS may usher in new prospects and challenges for high efficiency and stability of PDT and anticancer therapy. In conclusion, we have provided perspectives and challenges of the future development of CD s.


Asunto(s)
Fotoquimioterapia , Puntos Cuánticos , Carbono/química , Especies Reactivas de Oxígeno , Puntos Cuánticos/química , Fluorescencia
15.
Int J Biol Macromol ; 213: 814-823, 2022 Jul 31.
Artículo en Inglés | MEDLINE | ID: mdl-35697163

RESUMEN

Biopolymers based on starch, cellulose and proteins extracted directly from biomass with or without modification have been widely used as the natural resources to produce biodegradable plastic. Starch has several disadvantages: strong hydrophilic behavior and inferior mechanical properties when compared with synthetic polymers. Starch is also mostly soluble in water and will be decomposed before undergoing the gelatinization process. To provide resistance and mechanical strength of starch, several fillers (reinforcement) in the form of metal and natural materials are usually added to the polymer matrix. Zinc oxide (ZnO) nanoparticle and natural fiber as a lightweight material that is biocompatible, nontoxic, cost-effective and exhibit strong antibacterial activity can be considered as a reinforcement of starch-based bioplastic. The present study, the reinforcing effect of ZnO on the mechanical, antibacterial, and physical properties of bioplastic films in the form of cassava starch/chitosan/pineapple leaf fiber (PALF)/ZnO. The highest value of elongation at break is for 16 % ZnO-bioplastics which could be completely decomposed only 21 days in ordinary soil and only 18 days in seawater. The packaging tests using slice bread showed antimicrobial properties with no fungal growth for 30 days of bioplastic coatings with 10, 13, and 16 % ZnO NPs. The results in this study indicated that, the ZnO and PALF plays an important role in reinforcing the physical, mechanical, and antibacterial properties of starch/chitosan/PALF-based bioplastic.


Asunto(s)
Ananas , Quitosano , Manihot , Nanocompuestos , Óxido de Zinc , Antibacterianos , Hojas de la Planta , Polímeros , Agua de Mar , Suelo , Almidón
16.
Luminescence ; 37(8): 1246-1258, 2022 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-35671060

RESUMEN

Carbon dots (CDs) are 10-nm nanomaterial classes as excellent candidates in various applications: physics, biology, chemistry, and food science due to high stable biocompatibility and high surface expansive. CDs produced from natural materials have received wide attention due to their unique benefits, easy availabilities, sufficient costs, and harmless to the ecosystem. The various properties of CDs can be obtained from various synthesis methods: hydrothermal, microwave-assisted, and pyrolysis. The CDs have shown enormous potential in metal particle detection, colorimetric sensors, electrochemical sensors, and pesticide sensors. This review provides systematic information on a synthesis method based on natural resources and the application to the environmental sensors for supporting the clean environment. We hope this review will be useful as a reference source in providing the guidance or roadmap for new researchers to develop new strategies in increasing luminescence properties CDs for multi detection of heavy metals in the environment.


Asunto(s)
Metales Pesados , Puntos Cuánticos , Carbono/química , Ecosistema , Luminiscencia , Recursos Naturales , Puntos Cuánticos/química
17.
ACS Omega ; 6(42): 28334-28346, 2021 Oct 26.
Artículo en Inglés | MEDLINE | ID: mdl-34723030

RESUMEN

Visible-light absorption is a critical factor for photocatalyst activity and absorption of electromagnetic (EM) interference application. The band gap of Fe2O3 is 2 eV, which can be increased by doping with a high-band-gap material such as carbon from activated carbon (AC) with a band gap of 4.5 eV for increased visible-light absorption. The porosity decreases from 88 to 81.6%, and the band gap increases from 2.14 to 2.64 eV by increasing the AC from 10 to 25%, respectively. The photocatalytic activity takes 120 min to produce a harmless product for 10-20% AC, but 25% AC shows 89.5% degradation in only 90 min and the potential to attenuate the EM wave up to 99% due to the RL being below -20 dB. The second- and third-cycle degradation achieved by the composite Fe2O3-AC having 25% AC is 88.2 and 86.5% in 90 min, respectively. The pore of the surface state of AC contains a trapped charge, and interaction occurs between the charge (electron/hole) and O2 or H2O to produce OH and superoxide (O2 -) radicals. These radicals move inside the molecule of the pollutant (methylene blue (MB)) to break up the bond, with the final products being H2O and CO2. The X-ray photoelectron (XPS) spectra show that oxygen plays a key role in the interatomic bonding with Fe, C, and MB atoms. The best absorption of EM interference is -21.43 dB, with degradation reaching 89.51% in only 90 min for 25% AC due to its higher band gap and anisotropy constant. Fe2O3-carbon is a multifunctional material for the green environment because of its electromagnetic interference absorption and photodegradation of wastewater.

18.
Luminescence ; 36(6): 1354-1364, 2021 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-33982393

RESUMEN

Carbon dots (CDs) are carbon nanoparticles with a size of less than 10 nm, and are synthesized from various sources; they have been of great interest to scientists worldwide due to their unique optical, electrical, and chemical properties. Sources of carbon are inexpensive and can be classified as a renewable natural resources. Many researchers use CDs because of their low toxicity, better water solubility, high biocompatibility, and stable photoluminescence. The simple methods for producing CDs are hydrothermal and use inexpensive equipment, have low energy consumption, simple manipulation, and one-step preparation. Since the discovery of CDs, researchers have used them in various applications such as sensing, bioimaging, drug delivery, and catalysis. In this review, CDs synthesized from natural resources such as samples from herbs, roots, leaves, flowers, and fruit and some applications are described. This review provides a summary of carbon dots that is expected to provide further information for development of new CDs.


Asunto(s)
Carbono , Puntos Cuánticos , Catálisis , Solubilidad
19.
J Appl Biomater Funct Mater ; 17(1): 2280800018820185, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-30819030

RESUMEN

Structural properties and chemical bonding of new composites (ZnMnO2 and activated carbon) with honeycomb structure have been studied by using X-ray diffraction and Fourier transform infrared. The composition of the powder of ZnMnO2 has been studied by X-ray fluorescence in waste derived from a conventional battery. X-ray diffraction data show that the average crystallite size and the dislocation density for the composite are 90.17 nm and 12.30 × 1013 m-2, respectively. The C-O and C=O bonding for composites seen shifted to the lower wave number of pure ZnMnO2 and activated carbon indicated size reduction as an effect of Zn or Mn in the site of activated carbon. In addition, the reflection loss was analyzed by vector network analyzer and shows reflection loss of about -21.72 dB, the frequency range being 4.40-4.59 GHz for a thickness of 6 nm. The honeycomb structure of composite ZnMnO2-AC in this study promises new types of composite materials for various applications.


Asunto(s)
Carbón Orgánico/química , Compuestos de Manganeso/química , Óxidos/química , Zinc/química , Cristalización , Espectroscopía Infrarroja por Transformada de Fourier , Difracción de Rayos X
20.
Int J Biomater ; 2019: 3526145, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-31915437

RESUMEN

Biochars from bamboo leaves as a potential energy resource were synthesized by annealing in the oxygen-free environment. Samples were characterized using proximate analysis, Fourier-transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). Heating temperatures are 250°C, 300°C, and 350°C and for each temperature, the time was varied between 30, 60, and 90 minutes. The heating time for 30 minutes results in FC 30.777% and calorific value 15 MJ/Kg at temperature 250°C and decreased to 4.004% and 6 MJ/Kg at temperature 350°C, respectively. EDS shows the time of heating is an important parameter which shows the carbon and nitrogen contents were decreasing with the increase in the heating time, and silicon and oxygen contents were increasing with increase in the heating time. XRD shows broad (002) reflections between 20° and 30°, which indicated disordered carbon with small domains of coherent and parallel stacking of the graphene sheets, which is consistent with surface morphology of the SEM image. The experimental results indicated that heating at 300°C for 30 minutes is an effective and efficient parameter for fabrication of low-cost carbon from bamboo leaves which is a source of useful energy.

SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA
...