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Mode-locking in Er-doped fiber laser with reduced graphene oxide on a side-polished fiber as saturable absorber
摘要： In this work, the generation of highly stable mode-locked pulses from a side-polished fiber (SPF) embedded with graphene oxide (rGO) nanoparticles (NPs) is proposed and demonstrated. The rGO NPs are obtained from a graphene oxide solution prepared using Hummer’s technique, before being reduced by a hydrothermal route. The rGO NPs, suspended in the form of a solution, are then drop-casted onto the SPF. The SPF is fabricated by polishing away the cladding layer of a single-mode fiber section, leaving the core exposed and allowing the evanescent field of the signal propagating through the fiber to interact directly with the NPs. The SPF is integrated into an erbium doped fiber laser (EDFL) cavity, and the strong nonlinear optical response and spectral filtering by the rGO NPs as well as total anomalous dispersion of the laser cavity generates highly stable soliton mode-locked pulses with visible Kelly’s sidebands at 1544.02 nm. The output pulses have a pulse repetition rate of 16.79 MHz and pulse duration of 1.17 ps throughout the mode-locking operation range of 64.44–280.5 mW. The rGO NP coated SPF in this work demonstrates the viability and performance of the SPF for mode-locked pulse generation via evanescent field interactions.
关键词： Side polished fiber,Reduced graphene oxide,Mode-locked fiber laser,Saturable absorber
更新于2025-11-28 14:23:57
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Investigation of temperature and frequency dependence of electrical conductivity and dielectric behavior in CuS and rGO capped CuS nanocomposites
摘要： In this work, we develop a simple and low-cost strategy toward the one-pot synthesis of reduced graphene oxide (rGO) capped copper sulfide (CuS) nanocomposite through an obvious redox transformation reaction between Cu and graphene oxide (GO) without any additive. The prepared CuS and rGO capped CuS nanocomposite have been characterized by various physicochemical techniques for the observation of shape, morphology, and structure. It reveals the average size of the synthesized samples in the range of 10–30 nm with the hexagonal structure. The UV–vis absorption spectra exposed the strong absorption peak of CuS and rGO capped CuS composites in the range of NIR region was observed. The synthesized samples displayed high dielectric constant and electrical conductivity in a wide range of frequency (102–106 Hz). The effect of temperature on the electrical conductivity of the synthesized rGO capped CuS nanocomposite was also investigated. The excellent electrical conductivity performance is ascribed to the synergistic effect between CuS and rGO. As the temperature increases, the maximum electrical conductivity of rGO capped CuS composite was exponentially increased at high temperature. The synthesized composite with a high dielectric constant and electrical conductivity is a promising material in high capacitance, and further, it is used as electrode materials for supercapacitors and energy storage applications.
关键词： electrical conductivity,temperature effect,CuS nanocomposites,reduced graphene oxide,dielectric constant
更新于2025-11-21 11:18:25
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One-step growth of reduced graphene oxide on arbitrary substrates
摘要： Reduced graphene oxide (rGO) has inherited the outstanding electronic, optical, thermal and mechanical properties of graphene to a large extent, while maintaining sufficient chemically active sites. Therefore, it has attracted a great deal of research attention in the fields of energy storage, electronics, photonics, catalysis, environmental engineering, etc. Currently, the most popular way to prepare rGO is to reduce graphene oxide, which is obtained by modified Hummer methods using tedious treatments in a harsh environment, to rGO flakes. Industrial applications demand advanced preparation methods that can mass produce highly uniform rGO sheets on arbitrary substrates. In this work, a one-step growth process is introduced that utilizes cellulose acetate as a precursor, without any catalysts, to produce uniform ultrathin rGO films on various substrates and free-standing rGO powders. Systematic spectroscopic and microscopic studies on the resulting rGO are performed. Prototypes of electronic and optoelectronic devices, such as field effect transistors (FETs), photodetectors, and humidity sensors, are fabricated and tested, demonstrating the intriguing applications of our rGO materials across a wide range of fields.
关键词： electronic devices,reduced graphene oxide,one-step growth,cellulose acetate,optoelectronic devices
更新于2025-11-21 11:03:25
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AIP Conference Proceedings [Author(s) CURRENT TRENDS IN RENEWABLE AND ALTERNATE ENERGY - Guwahati, India (4–6 December 2018)] - Study of laser induced micro-structural changes in reduced graphene oxide
摘要： Graphene is a promising 2D material for solar cell and energy storage applications. Graphene based materials such as Graphene oxide (GO) are proposed as anode materials for Lithium ion batteries, transparent conducting films, electrodes in polymer based solar cells and many other applications. The present paper discusses laser induced micro structural changes in reduced GO (r-GO) thin films. GO was prepared by Modified Hummers Method, which is easy and low cost method for its large-scale production. The samples were thermally annealed at 400°C to obtain r-GO. To study the influence of laser exposure on micro structure of r-GO, the Raman spectra was recorded after exposure to different time 2, 4, 6 and 8 minutes. Two different laser intensities (95 and 159 KW/cm2) were used to do the same. A blue shift in peak positions and change in ratio of intensity were observed in D and G peaks of Raman spectra after exposure. A total Raman blue shift of about 5 cm-1 is noted in each case, which is due to increased compressive stress between the carbon-carbon bonds. The Raman data was used for calculations of residual stress, grain size and defect density, which changes in gradual pattern with increase in power density and time of exposure. From these observations, it can be concluded that r-GO thin film undergoes micro-structural changes at exposed portion, without affecting rest of the film.
关键词： Graphene,Raman Spectroscopy,Reduced Graphene Oxide,Laser Induced Changes,Graphene Oxide
更新于2025-11-21 11:01:37
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Superior light harnessing and charge injection kinetics utilizing mirror-like nano cuboidal ceria coupled with reduced graphene oxide in zinc oxide nanoparticle based photovoltaics
摘要： Efficiency in nanoparticle based photovoltaics is limited by optical transparency, light absorption as well as detrimental back transfer of electron at the hetero-interfaces. Three dimensional (3D) micro/nanostructures with excellent light scattering properties play pivotal role in light harvesting efficiency in DSSCs. Present study deals with the design and development of ternary hybrid photoanode utilizing high quality mirror like nano-cuboidal ceria (CeO2 NC) and 2D- reduced graphene oxide (RGO) sheets in conjunction with ZnO nanoparticle. A ～6% power conversion efficiency has been achieved for photoanode with optimized CeO2 NC loaded with 1 wt% RGO into ZnO NP. CeO2 NC owing to its size and high quality mirror like facets provides a better light harvesting by multiple interactions of incident photon with the absorber as revealed by UV–Vis diffused reflectance and IPCE analysis. 2D- RGO is proposed to act as an electron sink and provides faster electron transport pathway. Inclusion of 2D- RGO sheets yields a better charge injection kinetics (keinj ～ 2.3 × 108 s?1 for ternary, 1.1 × 108 s?1 for reference device) and collection at FTO as well as elevated recombination resistance (Rrec) and photo-induced electron life time (τe), unveiled by Electrochemical Impedance Spectroscopic (EIS) analysis corroborates a reduced reverse tunneling of photo-injected electron at ZnO/sensitizer/redox couple interface.
关键词： Diffusion,Mirror-like,Light scattering material,Reduced graphene oxide,Electrochemical impedance spectroscopy,Nano cuboidal
更新于2025-11-21 11:01:37
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One-Step Photochemical Synthesis of Transition Metal - Graphene Hybrid for Electrocatalysis
摘要： For widespread use of renewable energy such as water splitting, the development of electrocatalysts on a large-scale at a low-cost that remains safe and environmentally friendly is still a great challenge. Here, we report the use of α-aminoalkyl radicals in a one-step procedure that synthesizes transition metal nanoparticle - graphene composites via photoreduction. The organic photocatalyst 2-Methyl-1-[4-(methylthio)phenyl]-2-(morpholinyl) phenyl]-1-butanone (I-907) undergoes Norrish Type I photocleavage to generate strongly reducing α-aminoalkyl radicals, when exposed to UVA. For the first time we demonstrate its ability to reduce graphene oxide (GO) and successfully synthesize Co3O4 nanoparticles decorated on graphene (Co3O4NP-rGO). The α-aminoalkyl radicals simultaneously reduce GO and Co2+ salts which nucleates on the negatively charged GO sheets and grows to form nanoparticles. The resulting Co3O4NP-rGO showed decent catalytic activity and stability for the Oxygen Evolution Reaction (OER). Our work introduces a new and environmentally friendly synthesis procedure that can be used to produce earth abundant transition metal electrocatalysts.
关键词： photochemical synthesis,reduced graphene oxide,Graphene oxide,α-aminoalkyl radicals,water oxidation,metal nanoparticles
更新于2025-11-19 16:56:35
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Tuning the electrical properties of graphene oxide by nitrogen ion implantation: Implication for gas sensing
摘要： Tailoring the electrical properties of graphene oxide (GO) is one of the important requirements for its application in future electronic devices. A modified Hummer’s method was employed in the preparation of GO and spray coated on glass substrates, subsequently drying at 60 °C for 6 h. The as prepared samples were implanted with 100 keV nitrogen ions at the fluences of 1E15, 5E15 and 1E16 ions/cm2. A peak shift to higher 2θ in XRD pattern indicates the reduction of GO to rGO after N ion implantation. The intensity ratio of G and D bands (IG/ID) for GO derived from the Raman analysis increased from 0.97 to 1.02 after implantation (1E16 ions/cm2). The EDS analysis confirms the implantation of N ions in GO. The electrical conductivity improved as a function of fluence, and observed to be high for the sample of 1E16 ions/cm2, and is tested for methanol sensing. Concentration dependent methanol sensing shows 5.9% response for 300 ppm. Above results show that ion implantation is a promising method for controlled reduction of GO for tuning the electrical properties.
关键词： Ion implantation,Gas sensing,Graphene oxide,Reduced graphene oxide
更新于2025-09-23 15:23:52
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Two-step synthesis of reduced graphene oxide with columnar-shaped ZnO composites and their photocatalytic performance with natural dye
摘要： Composites of ZnO with reduced graphene oxide were prepared in two-step synthesis process with constant temperature in variation with pH values. The synthesized composites were characterized and the results suggest that ZnO structure in the composites has a columnar morphology with an average diameter ranging 0.8–1.57 μm. The obtained properties of the composites with the present method confirmed that the material morphology influences the absorption and photocatalytic activity of natural dye under sunlight irradiation. The result shows that the maximum degradation efficiency is 64.40% achieved in 120 min.
关键词： Zinc oxide,Columnar morphology,Photocatalytic activity,Reduced graphene oxide,Natural dye
更新于2025-09-23 15:23:52
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Cuprous oxide nanocubes decorated reduced graphene oxide nanosheets embedded in chitosan matrix: A versatile electrode material for stable supercapacitor and sensing applications
摘要： Herein, we report cuprous oxide nanocubes decorated reduced graphene oxide (CNC-rGO) immersed in chitosan matrix as a versatile and enhanced electrochemically active electrode material for both supercapacitor and hydrogen peroxide (H2O2) sensor applications. The CNC-rGO was synthesized by one-pot scalable chemical precipitation method. The morphology and crystal structure of as-synthesized hybrid material was characterized by field emission scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The CNC-rGO hybrid material immersed in the chitosan matrix was used as an enhanced electrochemically active electrode material for supercapacitor and hydrogen peroxide (H2O2) sensor. The fabricated CNC-rGO hybrid in chitosan matrix as an electrode showed remarkable charge storage capacity of 772.3 F g-1 (12.87 mA h g-1) at a current density of 0.2 A g-1 with high cyclic stability over 2000 charge-discharge cycles. Similarly, H2O2 sensing performance of the same electrode exhibits very high sensitivity of 0.33 A M-1 cm-2 within a linear range of detection of 20-160 μM. Thus, the synthesized CNC-rGO hybrid material composed of numerous cuprous nanocubes on rGO nanosheets with large active sites showed enhanced electrochemical activity beneficial towards the supercapacitor and H2O2 sensor applications.
关键词： copper oxide nanocubes,chitosan,supercapacitor,H2O2 sensor,reduced graphene oxide
更新于2025-09-23 15:23:52
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Label-free immunosensors based on a novel multi-amplification signal strategy of TiO2-NGO/Au@Pd hetero-nanostructures
摘要： A label-free electrochemical immunosensor for quantitative detection of human epididymis specific protein 4 antigen (HE4 Ag) was developed by a novel multi-amplification signal system. The multi-amplification signal system was formed by loading bimetallic Au@Pd holothurian-shaped nanoparticles (Au@Pd HSs) on titanium oxide nanoclusters functionalized nitrogen-doped reduced graphene oxide (TiO2-NGO). The Au@Pd HSs were obtained via seed-mediated approach with in-situ grown palladium nanoarms on gold nanorods (Au NRs) surfaces, which possessed good electrocatalysis for hydrogen peroxide (H2O2) reduction and excellent biocompatibility. The TiO2-NGO with the high catalytic activity and large specific surface area was synthesized by hydrothermal method. Using H2O2 as an electrochemically active substrate, the prepared label-free electrochemical immunosensor based on the TiO2-NGO/Au@Pd HSs hetero-nanostructures as the signal amplification platform exhibited excellent selectivity, reproducibility and stability for the detection of HE4 Ag. Meanwhile, the linear range from 40 fM to 60 nM with the detection limit of 13.33 fM (S/N = 3) was obtained, indicating the immunosensor offers a promising method for clinical detection of HE4 Ag.
关键词： Au@Pd nanoparticles,Titanium oxide,Label-free electrochemical immunosensor,Nitrogen-doped reduced graphene oxide,Human epididymis specific protein 4
更新于2025-09-23 15:23:52