Graphene quantum dots doped poly(vinyl alcohol)hybrid membranes for desalination via pervaporation

Pervaporation desalination by highly hydrophilic materials such as poly(vinyl alcohol)(PVA)based separation membrane is a burgeoning technology of late years.However,the improvement of membrane flux in pervaporation desalination has been a difficult task.Here,a novel hybrid membrane with doped graphene oxide quantum dots(GOQDs)which is rich in hydrophilic groups and small size into the matrix of PVA was prepared to improve the membrane flux.The membranes structures were described by field emission scanning electron microscopy(FESEM),atomic force microscopy(AFM),Fourier transform infrared(FT-IR),differential scanning calorimetry(DSC),thermogravimetric analysis(TGA)and X-ray diffraction(XRD).And more,Water contact angle,swelling degree,and pervaporation properties were carried out to explore the effect of GOQDs in PVA matrix.In addition,GOQDs content in the hybrid membrane,NaCl concentration,and feed temperature were investigated accordingly.Moreover,the hydrogen bonds between PVA chains were weakened by the interaction between GOQDs and PVA chains.Significantly,the hybrid membrane with optimized doped GOQDs content,200 mg·L^(-1),displays a high membrane flux of 17.09 kg·m^(-2)·h^(-1)and the salt rejection is consistently greater than 99.6%.

Enhanced visible-light photocatalytic degradation and disinfection performance of oxidized nanoporous g-C3N4 via decoration with graphene oxide quantum dots

Oxidized nanoporous g-C3N4(PCNO)decorated with graphene oxide quantum dots(ox-GQDs)was successfully prepared by a facile self-assembly method.As co-catalysts,the ultrasmall zero-dimensional(0 D)ox-GQDs can achieve uniform dispersion on the surface/inner channels of PCNO,as well as intimate contact with PCNO through hydrogen bonding,π-π,and chemical bonding interactions.In contrast with PCNO,the ox-GQDs/PCNO composite photocatalysts possessed improved light-harvesting ability,higher charge-transfer efficiency,enhanced photooxidation capacity,and increased amounts of reactive species due to the upconversion properties,strong electron capturing ability,and peroxidase-like activity of the ox-GQDs.Therefore,the visible-light photocatalytic degradation and disinfection performances of the ox-GQDs/PCNO composite were significantly enhanced.Remarkably,the composite with a 0.2 wt.% deposited amount of ox-GQDs(ox-GQDs-0.2%/PCNO)exhibited optimum amaranth photodegradation activity,with a corresponding rate about 3.1 times as high as that of PCNO.In addition,ox-GQDs-0.2%/PCNO could inactivate about 99.6%of Escherichia coli(E.coli)cells after 4 h of visible light irradiation,whereas only^31.9% of E.coli cells were killed by PCNO.Furthermore,h+,·O2-,and·OH were determined to be the reactive species generated in the photocatalytic process of the ox-GQDs/PCNO system;these species can thoroughly mineralize azo dyes and effectively inactivate pathogenic bacteria.

Enhanced permeability and biofouling mitigation of forward osmosis membranes via grafting graphene quantum dots

In this paper,graphene oxide quantum dots with amino groups(NH_(2)-GOQDs)were tailored to the surface of a thin-film composite(TFC)membrane surface for optimizing forward osmosis(FO)membrane performance using the amide coupling reaction.The results jointly demonstrated hydrophilicity and surface roughness of the membrane enhanced after grafting NH_(2)-GOQDs,leading to the optimized affinity and the contact area between the membrane and water molecules.Therefore,grafting of the membrane with a concentration of 100 ppm(TFC-100)exhibited excellent permeability performance(58.32 L·m^(–2)·h^(–1))compared with TFC membrane(16.94 L·m^(–2)·h^(–1)).In the evaluation of static antibacterial properties of membranes,TFC-100 membrane destroyed the cell morphology of Escherichia coli(E.coli)and reduced the degree of bacterial adsorption.In the dynamic biofouling experiment,TFC-100 membrane showed a lower flux decline than TFC membrane.After the physical cleaning,the flux of TFC-100 membrane could recover to 96%of the initial flux,which was notably better than that of TFC membrane(63%).Additionally,the extended Derjaguin–Landau–Verwey–Overbeek analysis of the affinity between pollutants and membrane surface verified that NH_(2)-GOQDs alleviates E.coli contamination of membrane.This work highlights the potential applications of NH_(2)-GOQDs for optimizing permeability and biofouling mitigation of FO membranes.

Enhanced charge extraction for all-inorganic perovskite solar cells by graphene oxide quantum dots modified TiO_(2)layer

All-inorganic cesium lead bromide(CsPbBr_(3))perovskite solar cells have been attracting growing interest due to superior performance stability and low cost.However,low light absorbance and large charge recombination at TiO_(2)/CsPbBr_(3)interface or within CsPbBr_(3)film still prevent further performance improvement.Herein,we report devices with high power conversion efficiency(9.16%)by introducing graphene oxide quantum dots(GOQDs)between TiO_(2)and perovskite layers.The recombination of interfacial radiation can be effectively restrained due to enhanced charge transfer capability.GOQDs with C-rich active sites can involve in crystallization and fill within the CsPbBr_(3)perovskite film as functional semiconductor additives.This work provides a promising strategy to optimize the crystallization process and boost charge extraction at the surface/interface optoelectronic properties of perovskites for high efficient and low-cost solar cells.

A novel phosphorus oxide quantum dots as an emissive nanomaterial for inorganic ions screening and bioimaging

In this work,a novel blue-green fluorescence phosphorous oxide quantum dots(PO QDs)was synthesized by solvothermal method in N-methyl-2-pyrrolidone(NMP)solution without any protection treatment during synthesis.Upon excitation at 400 nm,PO QDs emitted blue-green fluorescence with quantum yield of 0.28.PO QDs exhibited the high inertness to air or moisture,the excellent water solubility,and stable emission intensity in a wide pH range and in high ionic strength solution.Interestingly,PO QDs could give the positive optical response to iron ions(Fe^(3+))and iodine ion(I^(-)).The photoluminescence(PL)of PO QDs could be directly quenched by Fe^(3+).While I^(-)quenched the PO QDs PL by means of Ag^(+)-mediated PO QDs system via the internal filtration effects(IFE)induced by the formation of AgI.Moreover,the biocompatibility and low toxicity of PO QDs verified in bean sprout and Hela cells indicated the promising application of PO QDs in medicine related fields.Furthermore,PO QDs could also be utilized in luminescent composite film for various application scenarios.

Near infrared molybdenum oxide quantum dots with high photoluminescence and photothermal performance

The synthesized near infrared molybdenum oxide quantum dots perform excellent red fluorescence imaging performance and photothermal performance,which have 600,650 and 700 nm three unique peaks excited at 540 nm,with a high quantum yield around 20%.Meanwhile,with 808 nm NIR laser excitation,10 mg/mL modified Molybdenum oxide quantum dots can increase temperature up to 72.2℃within 150 s and 77.7℃within 270 s,respectively.

Properties of fluorescence based on the immobilization of graphene oxide quantum dots in nanostructured porous silicon films

The fluorescence of graphene oxide quantum dots （GOQDs） that are infiltrated into porous silicon （PSi） is investigated. By dropping activated GOQDs solution onto silanized PSi samples, GOQDs are successfully in- filtrated into a PSi device. The results indicate that the intensity of the fluorescence of the GOQD-inflltrated multilayer with a high reflection band located at its fluorescence spectra scope is approximately double that of the single layer sample. This indicates that the multilayer GOQD-infiltrated PSi substrate is a suitable material for the preparation of sensitive photoluminescence biosensors.