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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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Targeted delivery of reduced graphene oxide nanosheets using multifunctional ultrasound nanobubbles for visualization and enhanced photothermal therapy
摘要： Ultrasound molecular imaging as a promising strategy, which involved the use of molecularly targeted contrast agents, combined the advantages of contrast-enhanced ultrasound with the photothermal effect of reduced graphene oxide (rGO). Methods and results: The heparin sulfate proteoglycan glypican-3 (GPC3) is a potential molecular target for hepatocellular carcinoma (HCC). In this study, we covalently linked biotinylated GPC3 antibody to PEGylated nano-rGO to obtain GPC3-modified rGO-PEG (rGO-GPC3), and then combined rGO-GPC3 with avidinylated nanobubbles (NBs) using biotin-avidin system to prepare NBs-GPC3-rGO with photothermal effect and dispersibility, solubility in physiological environment. The average size of NBs-GPC3-rGO complex was 700.4±52.9 nm due to the polymerization of biotin-avidin system. Scanning electron microscope (SEM) showed NBs-GPC3-rGO attached to human hepatocellular carcinoma HepG2 cell. The ultrasound-targeted nanobubble destruction (UTND) technology make use of the physical energy of ultrasound exposure for the improvement of rGO delivery. Compared with other control groups, the highest nanobubble destruction efficiency of NBs-GPC3-rGO was attributed to the dissection effect of rGO on UTND. This is a positive feedback effect that leads to an increase in the concentration of rGO around the HepG2 cell. So NBs-GPC3-rGO using UTND and near-infrared (NIR) irradiation resulted in cell viability within 24 h, 48 h, 72 h lower than other treatment groups. Conclusion: This work established NBs-GPC3-rGO as an ultrasonic photothermal agent due to its suitable size, imaging capability, photothermal efficiency for visual photothermal therapy in vitro.
关键词： ultrasound-targeted nanobubble destruction,photothermal therapy,glypican-3,reduced graphene oxide,HepG2 cell
更新于2025-09-23 15:23:52
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Wafer-scale Fabrication of Nitrogen-doped Reduced Graphene Oxide with Enhanced Quaternary-N for High-Performance Photodetection
摘要： We demonstrated a simple and scalable fabrication route of nitrogen-doped reduced graphene oxide (N-rGO) photodetector on 8-inch wafer-scale. The N-rGO was prepared through in-situ plasma-treatment in an acetylene-ammonia atmosphere to achieve n-type semiconductor with substantial formation of quaternary-N substituted into the graphene lattice. The morphology, structural, chemical composition and electrical properties of the N-rGO was carefully characterized and being used for the device fabrication. The N-rGO devices were fabricated in a simple metal-semiconductor-metal (MSM) structure with unconventional metal-on-bottom configuration to promote high-performance photodetection. The N-rGO devices exhibited enhanced photoresponsivity as high as 0.68 A W?1 at 1.0 V, which is about two orders of magnitude higher compared to a pristine graphene and wide-band photo-induced response from visible to near-infrared (NIR) region with increasing sensitivity in the order of 785 nm, 632.8 nm and 473 nm excitation wavelengths. We also further demonstrated a symmetric characteristic of photo-induced response to any position of local laser excitation with respect to the electrodes. The excellent features of wafer-scale N-rGO devices suggest a promising route to merge the current silicon technology and two-dimensional materials for future optoelectronic devices.
关键词： photodetector,plasma treatment,quaternary-N,wafer-scale fabrication,Nitrogen-doped reduced graphene oxide
更新于2025-09-23 15:23:52
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Enhanced photocatalytic activity of TiO2/graphene by tailoring oxidation degrees of graphene oxide for gaseous mercury removal
摘要： We used a simple method of graphene oxide (GO) preparation with different oxidation levels, and control the properties of the TiO2 nanocrystals by tuning the content and oxidation degree of GO to enhance the photocatalytic performance. During the hydrothermal reaction, reduction of GO, formation of TiO2 and chemical bonds between TiO2 and reduced graphene oxide (RGO) was achieved simultaneously. Characterization results showed that TiO2 properties such as crystalline grain and particle size could be tailored by the amount of functional groups, and that crystallinity was also controlled by GO degrees of oxidation. TiO2/RGO photocatalysts showed great efficiency of mercury oxidation, which reached 83.7% and 43.6% under UV and LED light irradiation, respectively. The effects of crystalline grain size and surface chemical properties on Hg0 removal under LED and UV light irradiation were analyzed. In addition, the properties of the photocatalysts before and after UV illumination were investigated, finding that part of Ti-OH on TiO2 surface transformed to Ti-O-Ti. In a nutshell, this work could provide a new insight into enhancing activity of photocatalysts and understanding the photocatalytic mechanism.
关键词： TiO2,Photocatalysis,Chemical Bonds,Elemental Mercury,Reduced Graphene Oxide
更新于2025-09-23 15:23:52