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1.
Small ; 20(27): e2303421, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-38533978

RESUMO

Materials with tunable negative electromagnetic performance, i.e., where dielectric permittivity becomes negative, have long been pursued in materials research due to their peculiar electromagnetic (EM) characteristics. Here, this promising feature is reported in materials on the case of plasma-synthesized nitrogen-doped graphene sheets with tunable permittivity over a wide (1-40 GHz) frequency range. Selectively incorporated nitrogen atoms in a graphene scaffold tailor the electronic structure in a way that provides an ultra-low energy (0.5-2 eV) 2D surface plasmon excitation, leading to subunitary and negative dielectric constant values in the Ka-band, from 30 up to 40 GHz. By allowing the tailoring of structures at atomic scale, this novel plasma-based approach creates a new paradigm for designing 2D nanomaterials like nanocarbons with controllable and tunable permittivity, opening a path to the next generation of 2D metamaterials.

2.
Naunyn Schmiedebergs Arch Pharmacol ; 396(3): 533-546, 2023 03.
Artigo em Inglês | MEDLINE | ID: mdl-36418466

RESUMO

Oxidative stress, a pathological condition, contributes to the pathophysiology of a number of diseases including carcinogenesis. Numerous studies pointed out the disturbed antioxidants status and accumulation of oxidative stress markers in the carcinogenesis. The present study analyzed the anticancer efficacy of chlorogenic acid-loaded chitosan nanoparticles by utilizing the oxidative stress biomarkers as an endpoint in mice with skin cancer developed by 7,12-dimethylbenz(a)anthracene (DMBA). Oxidative stress markers' (lipid peroxidation by-products and antioxidants) levels or activities were measured using colorimetric assays. While mice exposed with DMBA alone showed a 100% tumor incidence, 0 and 50% tumor formation was seen in mice treated with DMBA + topical application of the nanoparticles and DMBA + orally administered nanoparticles, respectively. Also, the study noticed a 33% and 67% tumor incidence in mice treated with DMBA + topical application of free chlorogenic acid and DMBA + orally administered free chlorogenic acid, respectively. The present study noticed that the topical application of chlorogenic acid-loaded chitosan nanoparticles to DMBA-painted mice completely suppressed the tumor growth and restored the levels or activities of oxidative stress markers as compared to mice that received DMBA + oral administration of chlorogenic acid-loaded chitosan nanoparticles. The study observed that chlorogenic acid-loaded chitosan nanoparticles are more potent than free chlorogenic acid in preventing skin cancer in mice caused by DMBA. Thus, the present investigation explores the tumor-inhibiting efficacy of chlorogenic acid-loaded chitosan nanoparticles in experimental skin cancer, and the tumor preventive efficiency could be attributed to their antilipid peroxidative and antioxidant effects.


Assuntos
Carcinoma de Células Escamosas , Quitosana , Nanopartículas , Neoplasias Cutâneas , Animais , Camundongos , Antioxidantes/farmacologia , 9,10-Dimetil-1,2-benzantraceno/toxicidade , Ácido Clorogênico/farmacologia , Ácido Clorogênico/uso terapêutico , Carcinoma de Células Escamosas/patologia , Carcinogênese/patologia , Neoplasias Cutâneas/induzido quimicamente , Neoplasias Cutâneas/tratamento farmacológico , Neoplasias Cutâneas/prevenção & controle
3.
ACS Appl Mater Interfaces ; 13(17): 20559-20572, 2021 May 05.
Artigo em Inglês | MEDLINE | ID: mdl-33881814

RESUMO

Transition-metal sulfides combined with conductive carbon nanostructures are considered promising electrode materials for redox-based supercapacitors due to their high specific capacity. However, the low rate capability of these electrodes, still considered "battery-type" electrodes, presents an obstacle for general use. In this work, we demonstrate a successful and fast fabrication process of metal sulfide-carbon nanostructures ideal for charge-storage electrodes with ultra-high capacity and outstanding rate capability. The novel hybrid binder-free electrode material consists of a vertically aligned carbon nanotube (VCN), terminated by a nanosized single-crystal metallic Ni grain; Ni is covered by a nickel nitride (Ni3N) interlayer and topped by trinickel disulfide (Ni3S2, heazlewoodite). Thus, the electrode is formed by a Ni3S2/Ni3N/Ni@NVCN architecture with a unique broccoli-like morphology. Electrochemical measurements show that these hybrid binder-free electrodes exhibit one of the best electrochemical performances compared to the other reported Ni3S2-based electrodes, evidencing an ultra-high specific capacity (856.3 C g-1 at 3 A g-1), outstanding rate capability (77.2% retention at 13 A g-1), and excellent cycling stability (83% retention after 4000 cycles at 13 A g-1). The remarkable electrochemical performance of the binder-free Ni3S2/Ni3N/Ni@NVCN electrodes is a significant step forward, improving rate capability and capacity for redox-based supercapacitor applications.

4.
Nanomaterials (Basel) ; 10(9)2020 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-32872479

RESUMO

Oriented carbon nanostructures (OCNs) with dominant graphitic characteristics have attracted research interest for various applications due to the excellent electrical and optical properties owing to their vertical orientation, interconnected structures, electronic properties, and large surface area. Plasma enhanced chemical vapor deposition (PECVD) is considered as a promising method for the large-scale synthesis of OCNs. Alternatively, structural reformation of natural carbon precursor or phenol-based polymers using plasma-assisted surface treatment is also considered for the fabrication of OCNs. In this work, we have demonstrated a fast technique for the synthesis of OCNs by plasma-assisted structure reformation of resorcinol-formaldehyde (RF) polymer gels using radio-frequency inductively coupled plasma (rf-ICP). A thin layer of RF polymer gel cast on a glass substrate was used as the carbon source and treated with rf plasma under different plasma discharge conditions. Argon and hydrogen gases were used in surface treatment, and the growth of carbon nanostructures at different discharge parameters was systematically examined. This study explored the influence of the gas flow rate, the plasma power, and the treatment time on the structural reformation of polymer gel to produce OCNs. Moreover, the gas-sensing properties of as-prepared OCNs towards ethanol at atmospheric conditions were also investigated.

5.
Nanotechnology ; 31(39): 395604, 2020 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-32521529

RESUMO

The need for 2D vertical graphene nanosheets (VGNs) is driven by its great potential in diverse energy, electronics, and sensor applications, wherein many cases a low-temperature synthesis is preferred due to requirements of the manufacturing process. Unfortunately, most of today's known methods, including plasma, require either relatively high temperatures or high plasma powers. Herein, we report on a controllable synthesis of VGNs at a pushed down low-temperature boundary for synthesis, the low temperatures (450 °C) and low plasma powers (30 W) using capacitively coupled plasma (CCP) driven by radio-frequency power at 13.56 MHz. The strategies implemented also include unrevealing the role of Nickel (Ni) catalyst thin film on the substrates (Si/Al). It was found that the Ni catalyst on Si/Al initiates the nucleation/growth of VGNs at 450 °C in comparison to the substrates without Ni catalyst. With increasing temperature, the graphene nanosheets become bigger in size, well-structured and well separated. The role of Ni catalysts is hence to boost the growth rate, density, and quality of the growing VGNs. Furthermore, this CCP method can be used to synthesize VGNs at the lowest temperatures possible so far on a variety of substrates and provide new opportunities in the practical application of VGNs.

6.
Micromachines (Basel) ; 9(11)2018 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-30715064

RESUMO

Carbon, one of the most abundant materials, is very attractive for many applications because it exists in a variety of forms based on dimensions, such as zero-dimensional (0D), one-dimensional (1D), two-dimensional (2D), and-three dimensional (3D). Carbon nanowall (CNW) is a vertically-oriented 2D form of a graphene-like structure with open boundaries, sharp edges, nonstacking morphology, large interlayer spacing, and a huge surface area. Plasma-enhanced chemical vapor deposition (PECVD) is widely used for the large-scale synthesis and functionalization of carbon nanowalls (CNWs) with different types of plasma activation. Plasma-enhanced techniques open up possibilities to improve the structure and morphology of CNWs by controlling the plasma discharge parameters. Plasma-assisted surface treatment on CNWs improves their stability against structural degradation and surface chemistry with enhanced electrical and chemical properties. These advantages broaden the applications of CNWs in electrochemical energy storage devices, catalysis, and electronic devices and sensing devices to extremely thin black body coatings. However, the controlled growth of CNWs for specific applications remains a challenge. In these aspects, this review discusses the growth of CNWs using different plasma activation, the influence of various plasma-discharge parameters, and plasma-assisted surface treatment techniques for tailoring the properties of CNWs. The challenges and possibilities of CNW-related research are also discussed.

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