Carboxyl-functionalized Graphene Oxide Research Articles

Development Of Non-Enzymatic Electrochemical P-Nitrophenol Sensor Based On Carboxylated Graphene Oxide Modified Glassy Carbon Electrode

The current work reports a new electrochemical p-nitrophenol (p-NP) sensor which depends upon the carboxyl functionalized graphene oxide (GO-COOH) modified of glassy carbon electrode (GCE). Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were performed to examine the morphology of GO-COOH. The GO-COOH/GCE sensor was electrochemically characterized by means of chronoamperometry, electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and linear sweep voltammetry (LSV). A distinct cathodic peak of p-NP was seen on the GO-COOH/GCE in 0.1 M phosphate buffer solution (pH 6.5). The sensor displayed three dynamic linear ranges for p-NP under optimum conductions. The linear detection ranges were 2.0×10-7 - 2.95×10-6 M, 2.95×10-6 – 2.74×10-4 M, and 2.74×10-4 – 7.25×10-4 M with the sensitivities of 39622.1 A/Mm2, 9959.3 A/Mm2, and 6395 A/Mm2, respectively. It was found that detection limit (LOD) was 5.3×10-8 M at a signal to noise ratio of 3. The GO-COOH/GCE demonstrated satisfactory performance factors such as selectivity and repeatability. Additionally, the GO-COOH/GCE sensor was demonstrated to be utilized to electrochemically determine p-NP in a variety of water samples.

Dynamics of h-shape narrow bandwidth dissipative soliton in Yb-doped fiber laser

We demonstrate a narrow bandwidth mode-locked ytterbium-doped fiber laser based on the carboxyl-functionalized graphene oxide (GO-COOH). In the combination of GO-COOH and intracavity filtering effects, the narrow bandwidth spectrum exhibits an h-shape at 1060.76 nm central wavelength with a 3-dB bandwidth of 0.47 nm. Furthermore, the 3-dB bandwidth can be compressed to 0.049 nm by adjusting the polarization controller. The formation of h-shape dissipative soliton has been investigated by applying the dispersive Fourier transformation and numerical simulation. The h-shape narrow bandwidth dissipative soliton we demonstrated provides a new insight for investigating the evolution dynamics of solitons with special shapes.

The layer-by-layer assembled ERGO+/ERGO− multilayer modified electrode for sensitive detection of dopamine

Graphene materials represented by graphene oxide (GO) have been widely regarded as functional coatings or films to modify surface of the electrode for detecting dopamine molecules. However, interfacial material properties for detection sensitivity, film stability, and applicability to electrodes are still highly desired. Herein, we first present a screen-printing carbon electrode (SPCE) coated with an electrochemically reduced layer-by-layer (LbL) assembled multilayer driven by an electrostatic interaction between positively charged polyethyleneimine-modified GO with amine groups (ERGO+) and negatively charged carboxyl-functionalized GO (ERGO−), which is briefly described as (ERGO+/ERGO−)n/SPCE. Firstly, without using conventional glassy carbon and gold electrodes, SPCE was tried to make coatings adapt to more flexible and unstable electrodes, simultaneously guaranteeing higher detection performance. Secondly, although a variety of electrochemical sensors such as GO−/SPCE and ERGO−/SPCE were obtained through the drop-casting technique, as-prepared (ERGO+/ERGO−)n/SPCE showed much higher electrocatalytic activities with enhanced peak current signals and reduced charge transfer resistance. Finally, excellent electrochemical properties and sensing performances of the (ERGO+/ERGO−)n/SPCE sensor for detection of dopamine were demonstrated, especially having a linear range of 1 μM to 1000 μM. Meanwhile, the detection limit is as low as 0.39 μM and S/N is equal to 3. The present work offers a potential direction to develop GO modified electrodes for sensitive biomolecular detection.

Carboxyl-functionalized graphene oxide/cellulose nanofiber as adsorbents toward methylene blue

An efficient adsorbent for eliminating methylene blue (MB) from water solutions was created by combining carboxyl-functionalized graphene oxide (GO-COOH) with cellulose nanofiber. The GO-COOH was prepared using a malonic acid-choline chloride deep eutectic solvent, resulting in a carboxyl group ratio of 5.3 % and a C/O ratio of 2.15. This novel approach addresses the issue of partial reduction of GO-COOH observed in traditional preparation methods, thereby enhancing the adsorption capacity of the adsorbent for MB (611.44 mg g−1). In general, this method provides the opportunity for producing cellulose-based adsorbents for dye wastewater on a large scale, while being environmentally friendly.

Developing a versatile and resilient PVDF/CeO2@GO-COOH photocatalytic membrane for efficient treatment of antibiotic-contaminated wastewater

This study focuses on enhancing the performance of PVDF membranes by incorporating CeO2 photocatalyst in combination with carboxyl-functionalized graphene oxide (GO-COOH). The carboxyl groups of GO-COOH serve a dual purpose: providing anchoring sites for CeO2 and enhancing the interfacial interaction with the polymer. The PVDF/CeO2@GO-COOH membranes were fabricated using sequence of physical blending and phase inversion processes, resulting in significantly improved internal structure with an average pore size diameter of 1.20–1.35 nm. Moreover, the CeO2@GO-COOH photocatalyst exhibited superior compatibility with PVDF. The as-prepared PVDF/CeO2@GO-COOH photocatalytic membranes (PMs) demonstrated remarkable photocatalytic activity, outperforming PVDF/CeO2, achieving degradation efficiencies of 85.55 % for ciprofloxacin and 84.82 % for sulfanilamide (both at 20 mg/L) under UV irradiation for 150 min. Photo-filtration experiments confirmed the synergistic effect of molecular separation and photodegradation, resulting in the removal of 99.5 % of ciprofloxacin and 79.5 % of sulfanilamide, coupled with a relatively high pure water flux of 115.44 L.m−2.h−1. The PM also exhibited excellent stability, self-cleaning properties, and reusability, with a flux recovery rate (FRR) of 97.5 % after five cycles of use. Finally, the PVDF/CeO2@GO-COOH membrane holds great promise for the treatment of pharmaceutical industry wastewater, offering a comprehensive solution that combines efficient pollutant degradation, high permeate flux, stability, and reusability.

Nonlinear optical properties of carboxyl-functionalized graphene oxide for dissipative soliton resonance pulse generation

Here, we investigated the nonlinear optical (NLO) characteristics of carboxyl-functionalized graphene oxide (GO-COOH) in the near-infrared (NIR) region. The results revealed that GO-COOH samples exhibit strong saturable absorption at low pump levels and a gradual transition to reverse saturable absorption (RSA) with increasing pump power. Then the saturable absorber (SA) by depositing the GO-COOH on the side-polished fiber (SPF) was employed in Yb- and Er-doped fiber lasers. Stable ultrashort pulses operating in the dissipative soliton (DS) and conventional soliton (CS) regimes were obtained with pulse widths of 26.6 ps and 968 fs, respectively. Besides, the dissipative soliton resonance (DSR) phenomenon caused by the RSA of GO-COOH was also observed with increasing pump power. The high-stable DSR mode-locked pulses with the maximum pulse energy of 1.91 nJ and 0.74 nJ were obtained in YDFL and EDFL respectively. These results not only reveal the potentiality of GO-COOH in ultrafast photonics applications but also open a new avenue to explore high-pulse-energy laser sources based on two-dimensional materials.

Self-Assembled Nanofibrous Membranes by Electrospinning as Efficient Dye Photocatalysts for Wastewater Treatment.

Water pollution has become a leading problem due to industrial development and the resulting waste, which causes water contamination. Different materials and techniques have been developed to treat wastewater. Due to their self-assembly and photocatalytic behavior, membranes based on graphene oxide (GO) are ideal composite materials for wastewater treatment. We fabricated composite membranes from polylactic acid (PLA) and carboxylic methyl cellulose (CMC)/carboxyl-functionalized graphene oxide (GO-f-COOH) using the electrospinning technique and the thermal method. Then, a nanofibrous membrane (PLA/CMC/GO-f-COOH@Ag) was produced by loading with silver nanoparticles (Ag-NPs) to study its photocatalytic behavior. These membranes were characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) in order to investigate the behavior of the fabricated membranes. The degradation kinetics studies were conducted using mathematical models, such as the pseudo first- and second-order models, by calculating their regression coefficients (R2). These membranes exhibited exceptional dye degradation kinetics. The R2 values for pseudo first order were PCGC = 0.983581, PCGC@Ag = 0.992917, and the R2 values for pseudo second order were PCGC = 0.978329, PCGC@Ag = 0.989839 for methylene blue. The degradation kinetics of Rh-B showed R2 values of PCGC = 0.973594, PCGC@Ag = 0.989832 for pseudo first order and R2 values of PCGC = 0.994392, PCGC@Ag = 0.998738 for pseudo second order. The fabricated nanofibrous membranes exhibited a strong π-π electrostatic interaction, thus providing a large surface area, and demonstrated efficient photocatalytic behavior for treating organic dyes present in wastewater. The fabricated PLA/CMC/GO-f-COOH@Ag membrane presents exceptional photocatalytic properties for the catalytic degradation of methylene blue (MB) dye. Hence, the fabricated nanofibrous membrane would be an eco-friendly system for wastewater treatment under catalytic reaction.

Removal Efficiency of Sulfapyridine from Contaminated Surface Water by Carboxylated Graphene Oxide Blended PVDF Composite Ultrafiltration Membrane with Activated Carbon.

In this study, sulfapyridine (SPY), an antibiotic that is less commonly treated by membrane filtration techniques but is frequently detected in the aqueous environment and at higher concentrations than other detected antibiotics, was selected for investigation. A composite ultrafiltration membrane for the removal of sulfapyridine (SPY) antibiotics from water was fabricated using polyvinylidene fluoride (PVDF), polyvinylpyrrolidone (PVP), and carboxyl-functionalized graphene oxide (CFGO) as additives. The changes in retention rate and pure water flux of sulfapyridine by the composite ultrafiltration membrane were investigated by changing the ratios of the prepared ultrafiltration membrane materials under the conditions of low-pressure operation to explore the optimal experimental conditions. The results showed that the addition of PVP and CFGO significantly increased the number of membrane pores and their pore size. The addition of CFGO in the membrane significantly improved the hydrophilicity of the membrane. The contact angle decreased from 83.7 to 31.6°. Compared to ordinary PVDF ultrafiltration membranes, the membrane's pure water flux increased nearly three times to 2612.95 L/(m2·h). The removal rate of SPY was 56.26% under the optimal conditions. When the composite ultrafiltration membrane was combined with activated carbon, the removal rate of SPY was 92.67%, which was nine times higher than that of activated carbon alone. At this time, the flux of the composite membrane was 2610.23 L/(m2·h). This study proposes a simple, efficient, and low production cost solution for the removal of sulfapyridine from water.

Carboxyl functionalized graphene oxide based electrochemical sensor for detection of dopamine in presence of ascorbic acid, uric acid and synthetic cerebrospinal fluid

Dopamine is an important neurotransmitter and plays a vital role in the proper functioning of human metabolism. Therefore, fabrication of a sensitive sensor for the detection of dopamine is crucial. The work reports detection of dopamine in presence of interfering ascorbic acid, uric acid, Na + , K + , Ca 2+ , urea and glucose. The linear range for the detection of dopamine is observed from 1.07×10 -4 M to 2.19×10 -4 M in presence of 1.00×10 -3 M ascorbic acid and 1.00×10 -3 M uric acid. The detection limit is estimated to be 1.46×10 -8 M.

The comparison of interface properties on crude oil-water and rheological behavior of four polymeric nanofluids (nano-SiO2, nano-CaO, GO and CNT) in carbonates for enhanced oil recovery

Nanoparticles (NPs) are currently being used in different areas of petroleum exploration and production, such as drilling, well logging, reservoir management, and enhanced oil recovery (EOR). Nanofluids, prepared from NPs, have been used as a novel flooding for EOR due to the excellent performance in altering interfacial properties and improving rheological behaviors. The properties of nanofluids vary with the structure of nanofluids. Nonetheless, most of the previous studies have focused on a particular type of nanofluid, the interfacial properties of various polymeric nanofluids and their flow behaviors under harsh and challenging reservoir conditions have been rarely reported or compared in literature. In this study, four polymeric nanofluids, prepared by mixing nano-silica (nano-SiO2), nano-CaO, carboxyl functionalized graphene oxide (GO) and amino modified carbon nanotube (CNT) with partially hydrolyzed polyacrylamide (HPAM), were characterized through XRD, FT-IR, UV–Vis and SEM to confirm that the materials were successfully prepared. Then, the colloidal stability, interfacial tension (IFT) reduction, rheological behavior, and wettability on calcite surface of these polymeric nanofluids were also studied in comparison. The experimental results of CNT-NH2/HPAM nanofluid showed that the overlap degree of BS and ΔBS curves was high, oil/brine IFT reduced from 35.84 mN/m to 18.11 mN/m and the contact angle on calcite surface reduced from 139.69° to 47.985°, indicating that the nanofluids were colloidally stability, and both reduce the IFT and alter wettability effectively. Furthermore, the addition of SiO2 and CNT NPs enhanced the network structure significantly, and showed excellent rheological behavior of polymer solution with improved viscoelasticity. Finally, the CNT-NH2/HPAM nanofluid increased the additional oil recovery from 13.8% to 21.6% in core flooding experiments, with the oil displacement mechanism explained in detail. Therefore, the findings of this study can help for better understanding of the effect of NPs on polymeric nanofluids, and set the stage for future investigation into EOR application in carbonate reservoirs.

Efficient Eradication of Bacterial Biofilms with Highly Specific Graphene-Based Nanocomposite Sheets.

Bacterial biofilms are usually resistant to antibiotics, thus powerful methods are required for removal. Nanomaterial involving a combination of treatment modalities recently has been recognized as an effective alternative to combat biofilm. However, its targeted and controlled release in bacterial infection is still a major challenge. Here, we present an intelligent phototherapeutic nanoplatform consisting of an aptamer (Apt), indocyanine green (ICG), and carboxyl-functionalized graphene oxide (GO-COOH), namely, ICG@GO-Apt, for targeted treatment of the biofilm formed by Salmonella Typhimurium. Since Apt-conjugated nanosheets (NSs) can specifically accumulate near abscess caused by the pathogens, they enhance greatly the local drug molecule concentration and promote their precise delivery. They can simultaneously generate heat and reactive oxygen species under near-infrared irradiation for photothermal/photodynamic therapy, thereby significantly enhancing biofilm elimination. The phototherapeutic ICG@GO-Apt also displays a good biocompatibility. More importantly, the multifunction phototherapeutic platform shows an efficient biofilm elimination with an efficiency of greater than 99.99% in an abscess formation model. Therefore, ICG@GO-Apt NSs with bacteria-targeting capability provide a reliable tool for clinical bacterial infection that circumvents antibiotic resistance.

Ultrasensitive photoelectrochemical microcystin-LR immunosensor using carboxyl-functionalized graphene oxide enhanced gold nanoclusters for signal amplification

An ultrasensitive photoelectrochemical (PEC) immunosensor based on gold nanoclusters (AuNCs) with 11-mercaptoundecanoic acid (MUA) ligands was fabricated for determination of microcystin-LR (MC-LR). The PEC immunosensor was developed by loading the monoclonal MC-LR antibody (Ab) to the MUA-AuNCs modified gold electrodes. After different measurement conditions being optimized, silver nanoparticles (AgNPs), gold nanorods (AuNRs), graphene oxide (GO) and carboxyl-functionalized graphene oxide (cGO) were introduced into MUA-AuNCs to enhance the sensing properties. The experimental result revealed that the sensitivity of PEC immunosensors was enhanced by both their photoelectrochemical properties and antibody loading properties with dependent relationship, which was different from the enhancement strategy of PEC sensors based on redox reactions. Among different hybrid nanocomposites, MUA-AuNCs/cGO not only improved the photoelectrochemical properties, but also loaded more antibodies for sensing, which resulted in best sensing performance. Thus, a universal method was proposed to enhance the sensing performance of PEC immunosensors based on impedance changes. Finally, MUA-AuNCs/cGO based PEC immunosensors exhibited a wide linear range of 0.001 nM–1000 nM with low detection limit of 0.011 pM (S/N = 3) for MC-LR determination. Meanwhile, the designed PEC immunosensors showed high selectivity, reproducibility and specificity, which provided the promising applications in aquatic environment.

Ultraflat Langmuir–Blodgett assembled graphene oxide saturable-absorber films for pulsed near-infrared laser generation

Large-scale production of ultraflat broadband saturable-absorber films is highly desired for passive mode-locked solid-state lasers. However, the current vapour deposition and spin coating routes for fabricating saturable absorbers (SAs) are suffering from the limited flexibility in substrate choice and complexity of mass production processes. Here, we demonstrate an ultraflat carboxyl-functionalized graphene oxide (GO-COOH) SA film via Langmuir–Blodgett (LB) assembly for solid state laser mode-locking. Hydrophilic carboxyl groups from GO sheets weaken the aggregation effect thus contribute to the uniform and stable dispersion of GO sheets in water. Such GO suspensions are made into an ultrathin large-area graphene-based SA film by a LB assembly process ensuring high surface uniformity. The room-temperature and highly repeated operation for GO LB films avoids the thermal damage of GO sheets and improves the membrane repeatability. Consequently, the ultrathin GO-COOH SA shows the modulation depth (2.3%) and low saturation intensity (24.7 KW cm−2) under 1064 nm laser irradiation. By inserting the GO SA into a Nd:GdVO4 laser, both passive Q-switched (QS) and passive Q-switched mode-locked (QML) operations are also attained. The slope efficiency of QS laser is up to 35.6% and the maximum single pulse energy is 1.48 μJ. In particular, the QML pulses can be achieved stably and repeatedly with an average output power of 1.33 W and a pulse energy of 13.2 nJ. Our strategy provides a new concept for improving the modulation stability of graphene-based SAs and promoting their industrial application in pulsed solid-state lasers.

Switchable single- and dual-wavelength femtosecond mode-locked Er-doped fiber laser based on carboxyl-functionalized graphene oxide saturable absorber

In this Letter, we demonstrated the switchable single- and dual-wavelength femtosecond soliton generation in single-mode Er-doped fiber lasers with the usage of carboxyl-functionalized graphene oxide (GO-COOH) saturable absorbers (SAs) for the first time, to the best of our knowledge. The fiber laser generated a stable single-wavelength conventional soliton at 1560.1 nm with a pulse duration of 548.1 fs. The dual-wavelength solitons centered at 1531.9 nm and 1555.2 nm with a spacing of approximately 23 nm can be obtained by adjusting the pump power of the cavity. Our experimental results indicated the GO-COOH has great potential to be used in ultrafast fiber lasers as broadband SAs.

Clinical Application for Screening Down's Syndrome by Using Carboxylated Graphene Oxide-Based Surface Plasmon Resonance Aptasensors.

BackgroundAdvanced medical detection technology requires high sensitivity and accuracy to increase the disease detection rate. We showed that carboxyl-functionalized graphene oxide (carboxyl-GO) biosensing materials are capable of accurate detection.MethodsWe developed a carboxylated GO-based surface plasmon resonance (SPR) aptasensor suitable for screening Down’s syndrome in clinical serum. This biosensing material could rapidly and accurately detect hCG protein with a low concentration to identify fetal Down’s syndrome. The developed carboxyl-GO-based SPR aptasensor showed excellent sensitivity and limit of detection without the use of antibodies and without any specific preference.ResultshCG protein detection limits of 1 pM in buffer samples and 1.9 pM in clinical serum samples were achieved. The results showed that the carboxyl-GO-based chip could detect hCG well below the normal physiological level of serum protein (5.0 mIU/mL). High affinity, sensitivity, and better detection limit were obtained in the range of 1.9 pM to 135 pM. The results showed a 5k-fold dilution factor, and that an SPR angle shift of more than 20 millidegrees (mo) was associated with a significant risk of fetal Down’s syndrome compared to normal pregnant women. The results clearly showed that the detection of hCG protein in serum samples from pregnant women at 12–19 weeks could be used to screen Down’s syndrome with high selectivity and sensitivity.ConclusionOur findings suggest the potential application of carboxyl-GO film in proof-of-concept studies for serum assays as a new type of SPR material. In addition, peptide and carboxyl-GO films may be conducive to the development of future point of care testing and rapid diagnostic devices for other diseases such as cancer.

A sensitive immunoassay based on fluorescence resonance energy transfer from up-converting nanoparticles and graphene oxide for one-step detection of imidacloprid

In this study, a fluorescence resonance energy transfer (FRET) immunoassay based on graphene oxide (GO) and up-converting nanoparticles (UCNPs) was established for rapid detection of imidacloprid, a commonly-used insecticide. Under 980 nm near-infrared light excitation, emission of UCNPs at 542 nm can be absorbed by the energy acceptor GO. The carboxyl-functionalized GO and UCNPs were coupled with competitive antigen and antibody against imidacloprid. After optimization, the FRET immunoassay showed a wide detection range of 0.08–50 ng/mL to imidacloprid, with cross-reaction toward other three neonicotinoids including imidaclothiz (74.4%), thiacloprid (36.9%) and clothianidin (31.9%). The average recoveries of spiked water, Chinese cabbage, cucumber, honey and tea samples were 76.8%-101.8%. The accuracy and reliability of the FRET immunoassay were verified by UPLC-MS/MS with a good correlation (R2 = 0.9816). In a summary, this study provides a sensitive and one-step method for monitoring imidacloprid residue in food and environmental samples within 1 h.

A Novel Method for the Removal of Uranium by Using Carboxyl Functionalized Graphene Oxide

Graphene oxide (GO) and functionalized carboxylic graphene oxide (COOH-GO) were successfully synthesized by modified Hummer’s technique. The prepared GO and COOH-GO was characterized successfully by UV-Visible Spectroscopy, Fourier transforms infrared spectroscopy (FTIR), X-ray diffraction, Raman spectroscopy, Scanning electron microscopy (SEM)& Zeta potential. The removal of U(VI) heavy metal comparative study was done by using Graphite, GO & COOH-GO and the removal were confirmed by using LED fluorimeter. The effect of pH of medium, contact time, adsorbent dose, initial concentration of U(VI) were examined for the removal of U(VI). The extent of U(VI) removal has been found to be in the order of COOH-GO >GO> graphite. The U(VI) removal maximum efficiency was observed ~96% observed at pH 4.5. The higher removal efficiency is attributed to the higher negative surface charge of COOH-GO (zeta potential:-39.9 mV) in comparison to zeta potential of GO (-28.9 mV) &graphite (-21.6 mV).

Characterization of immobilized α-amylase on functionalized graphene oxide surface

Carboxyl-functionalized graphene oxide (GO-COOH) and amino-functionalized graphene oxide (GO-NH2) were prepared for use as carriers for α-amylase immobilization with 2-3% glutaraldehyde as a coupling agent. The α-amylase immobilized onto modified GO exhibited shifts in both working optimum pH and temperature with an increase from pH 6.0 to pH 7.0, and increased optimum temperature by 5-10℃ compared with the free enzyme. The loading capacity of the carriers is 786.8 mg/g (GO-COOH) and 437 mg/g (GO-NH2), respectively. The immobilized α-amylase exhibited a comparable stability activity in comparison with the free enzyme. The FT-IR spectra, UV-visible spectra as well as SEM analysis proved the presence of amine groups and carboxyl groups in the GO, and also covalent immobilization of α-amylase on the modified carrier. The constant values, the Km was 3.541 mg•mL1, 4.072 mg•mL1 and 8.004 mg•mL1 for free enzymes, GO-COOH-E, and GO-NH2-E, respectively, and their Vmax were 7.341 mg•mL1•min1, 4.968 mg•mL1•min1 and 6.655 mg•mL1•min1, respectively. Furthermore, above 54% of the original activity of the immobilized enzyme was retained after 7 reaction cycles, indicating excellent reusability.

Carboxyl graphene oxide solution saturable absorber for femtosecond mode-locked erbium-doped fiber laser**Project supported by the Central University Special Fund Basic Research and Operating Expenses, China (Grant No. GK201702005), the Natural Science Foundation of Shaanxi Province, China (Grant No. 2017JM6091), the National Natural Science Foundation of China (Grant No. 61705183), and the Fundamental Research Funds for the Central Universities, China (Grant

The carboxyl-functionalized graphene oxide (GO-COOH) is a kind of unique two-dimensional (2D) material and possesses excellent nonlinear saturable absorption property and high water-solubility. In this paper, we prepare saturable absorber (SA) device by depositing GO-COOH nanosheets aqueous solution on a D-shaped fiber. The modulation depth (MD) and saturable intensity of the SA are measured to be 9.6% and 19 MW/cm2, respectively. By inserting the SA into the erbium-doped fiber (EDF) laser, a passively mode-locked EDF laser has been achieved with the spectrum center wavelength of 1562.76 nm. The pulse duration, repetition rate, and the signal-to-noise ratio (SNR) are 500 fs, 14.79 MHz, and 80 dB, respectively. The maximum average output power is measured to be 3.85 mW. These results indicate that the GO-COOH nanosheets SA can be used as a promising mode locker for the generation of ultrashort pulses.

Antimicrobial and antifouling properties of versatile PPSU/carboxylated GO nanocomposite membrane against Gram-positive and Gram-negative bacteria and protein.

Biofouling is a serious issue in membrane-based water and wastewater treatment as it critically compromises the efficacy of the water treatment processes. This investigation demonstrates the antimicrobial and antifouling properties of a nanocomposite membrane system composed of carboxyl-functionalized graphene oxide (COOH-GO) and polyphenylsulfone (PPSU). The PPSU/COOH-GO nanocomposite membrane exhibited excellent antimicrobial properties, achieving maximum bacteriostasis rates of 74.2% and 81.1% against the representative Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa, respectively) and 41.9% against the representative Gram-positive bacterium (Staphylococcus aureus). The PPSU/COOH-GO nanocomposite membrane inhibited the attachment, colonization, and the biofilm formation of three species. Antifouling was assessed through filtration experiments using a model foulant bovine serum albumin (BSA). The fouling mechanisms were investigated by Hermia's models (complete blocking, intermediate blocking, standard blocking, and cake formation), and the analysis involved fitting the volumetric flux decline experimental data to models. The fouling study revealed a less irreversible fouling and increased flux recovery ratio for the PPSU/COOH-GO nanocomposite membrane. Complete blocking of pores and cake formation were the major fouling mechanisms for the membrane.