Jinsuo Gao

Preparation of molecularly imprinted polymer nanoparticles for selective removal of fluoroquinolone antibiotics in aqueous solution

In this study, novel molecularly imprinted polymer nanoparticles (nanoMCN@MIPs) were prepared by covalent grafting of ofloxacin-imprinted polymer onto the surface of mesoporous carbon nanoparticles (MCNs). SEM analyses indicated that the prepared nanoMCN@MIPs were almost uniform, and their geometrical mean diameter was about 230 nm. The sorption behaviors of the nanoMCN@MIPs including sorption kinetics and isotherms, effect of pH, ionic strength, and cross-reactivity were investigated in detail. The adsorption capacity of the nanoparticles for ofloxacin was 40.98 mg/g, with a selectivity factor of 2.6 compared to the nonimprinted polymer nanoparticles (nanoMCN@NIPs). The feasibility of removing fluoroquinolone antibiotics (FQs) from environmental waters with the nanoMCN@MIPs was demonstrated using sea water spiked with six typical FQs (ofloxacin, gatifloxacin, balofloxcacin, enrofloxacin, norfloxacin and sarafloxacin). The nanoMCN@MIPs could be reused at least five times with removal efficiency more than 90% except for norfloxacin.

Adsorption of ciprofloxacin, bisphenol and 2-chlorophenol on electrospun carbon nanofibers: in comparison with powder activated carbon.

Carbon nanofibers (CNFs) were prepared by electrospun polyacrylonitrile (PAN) polymer solutions followed by thermal treatment. For the first time, the influence of stabilization procedure on the structure properties of CNFs was explored to improve the adsorption capacity of CNFs towards the environmental pollutants from aqueous solution. The adsorption of three organic chemicals including ciprofloxacin (CIP), bisphenol (BPA) and 2-chlorophenol (2-CP) on electrospun CNFs with high surface area of 2326m(2)/g and micro/mesoporous structure characteristics were investigated. The adsorption affinities were compared with that of the commercial powder activated carbon (PAC). The adsorption kinetics and isotherms showed that the maximum adsorption capacities (qm) of CNFs towards the three pollutants are sequenced in the order of CIP>BPA>2-CP, which are 2.6-fold (CIP), 1.6-fold (BPA) and 1.1-fold (2-CP) increase respectively in comparison with that of PAC adsorption. It was assumed that the micro/mesoporous structure of CNFs, molecular size of the pollutants and the π electron interaction play important roles on the high adsorption capacity exhibited by CNFs. In addition, electrostatic interaction and hydrophobic interaction also contribute to the adsorption of CNFs. This study demonstrates that the electrospun CNFs are promising adsorbents for the removal of pollutants from aqueous solutions.

The nanocomposites of SO3H-hollow-nanosphere and chiral amine for asymmetric aldol reaction

The nanocomposites formed by SO3H-hollow-nanospheres and chiral amines are highly efficient catalysts for the direct asymmetric aldol reaction of cyclohexanone and 4-nitrobenzaldehyde. The catalyst showed 91% yield with 96% ee under optimized reaction conditions. SO3H-hollow-nanospheres were synthesized by oxidation of thiol-hollow-nanospheres, which were fabricated through a one-pot co-condensation of 1,2-bis(trimethoxysilyl)ethane and 3-mercaptopropyltrimethoxysilane around F127 micelles in the presence of NaOAc. Chiral amines could be combined with SO3H-hollow-nanospheres through facile electrostatic interactions. The obtained nanocomposites showed a much higher reaction rate than the catalyst formed from the combination of chiral amine and SO3H-mesoporous-organosilica (ribbon shaped particles with particle size of tens of micrometres) in the direct asymmetric aldol reaction. This is mainly attributed to the hollow spherical morphology and nano-scale particle size (16–20 nm) of the SO3H-hollow-nanospheres.

Clickable Periodic Mesoporous Organosilicas: Synthesis, Click Reactions, and Adsorption of Antibiotics

Pharmaceutical antibiotics are not easily removed from water by conventional water-treatment technologies and have been recognized as new emerging pollutants. Herein, we report the synthesis of clickable azido periodic mesoporous organosilicas (PMOs) and their use as adsorbents for the adsorption of antibiotics. Ethane-bridged PMOs, functionalized with azido groups at different densities, were synthesized by the co-condensation of 1,2-bis(trimethoxysilyl)ethane (BTME) and 3-azidopropyltrimethoxysilane (AzPTMS), in the presence of nonionic-surfactant triblock-copolymer P123, in an acidic medium. Four different alkynes were conjugated to azide-terminated PMOs by means of an efficient click reaction. The clicked PMOs showed improved adsorption capacity (241 μg g(-1)) for antibiotics (ciprofloxacin hydrochloride) compared with azido-functionalized PMOs because of the enhanced π-π stacking interactions. These results indicate that click reactions can introduce multifunctional groups onto PMOs, thus demonstrating the great potential of PMOs for environmental applications.

Simultaneous detection of dopamine, uric acid, and ascorbic acid using SnO2 nanoparticles/multi-walled carbon nanotubes/carbon paste electrode

A novel SnO2 nanoparticles/multi-walled carbon nanotubes/carbon paste electrode (nanoSnO2/MWCNTs/CPE) was prepared for simultaneous detection of dopamine (DA), uric acid (UA), and ascorbic acid (AA) via cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The novel nanoSnO2/MWCNTs/CPE electrode showed high electrochemical catalytic behavior for DA, UA, and AA. The three compounds could be completely separated on the electrode in CV and DPV at optimal conditions. DPV provided larger peak potential separations and higher response sensitivities of DA, UA, and AA compared to CV. In DPV, there are linear relationships between the peak currents and the concentrations in the ranges of 0.3–50 μM for DA, 3–200 μM for UA, and 0.1–5 mM for AA, with the detection limits (S/N = 3) of 0.03, 1, and 50 μM for DA, UA, and AA, respectively. The proposed method was applied for the simultaneous detection of DA, UA, and AA in human urine samples, with recoveries of 91.0%, 97.4%, and 103.0% for DA, UA, and AA, respectively. The relative standard derivations (RSDs, n = 5) were 2.8–4.4%.

DNA-modified graphene quantum dots as a sensing platform for detection of Hg2+ in living cells

Detection of metal ions in living cells is significant in environmental monitoring and health risk assessment. This paper reports a simple and facile method for the detection of Hg2+ ions in Hela cells through fluorescence imaging, which was based on the fluorescence quenching in thymine-rich DNA modified graphene quantum dots (DNA-GQDs) in the presence of Hg2+. The decrease in the fluorescence intensity was attributed to the electron transfer of DNA-GQDs due to Hg2+ bound to the thymine bases of the DNA, resulting in a T–T mismatch hairpin structure. The method shows high selectivity and sensitivity. This present sensing platform will have broad applications in biological imaging and environmental monitoring.

An electrochemically reduced graphene oxide chemiresistive sensor for sensitive detection of Hg 2+ ion in water samples

Divalent mercuric (Hg2+) ion is one of the most prevalent forms of mercury species in waters with high toxicity and bioaccumulation in the human body, for which sensitive and selective detection methods are highly necessary to carry out its recognition and quantification. Here an electrochemically reduced graphene oxide (RGO) based chemiresistive sensor was constructed and used for the detection of Hg2+ ion in various water samples. Monolayer GO sheets were assembled onto interdigitated electrodes, followed by reduction through linear sweep voltammetry and then modification with a single-stranded DNA aptamer. The electrochemically derived RGO based sensor showed selective response to as low as 0.5nMHg2+ ion in presence of other metal ions and matrices. A comparison between chemiresistive sensors prepared with electrochemically and chemically derived RGO showed that the former had better response performance for sensing Hg2+ ion. The proposed method provides a simple tool for rapid, selective and sensitive monitoring of Hg2+ ion in environmental samples.

Graphene oxide based in‐tube solid‐phase microextraction combined with liquid chromatography tandem mass spectrometry for the determination of triazine herbicides in water

A novel in-tube solid-phase microextraction method based on a graphene oxide coated column was developed for the determination of triazines in waters. This column was prepared by the covalent modification of monolayer graphene oxide sheets onto the inner wall of a fused-silica capillary. Scanning electron microscopy showed that the thickness of the graphene oxide coating was ∼30 nm, with a porous, wrinkled membrane-like structure. Its performance was evaluated through the extraction of triazines in water. Results showed that the coating was stable for at least 100 replicate extractions, and variety of multi-columns was less than 10%. Flow rate, loading volume, pH, and ionic strength of samples played an important effect on the extraction. The high extraction efficiency was mainly attributed to π-π stacking and hydrogen bonding interactions. The in-tube solid-phase microextraction was used in the determination of triazines with liquid chromatography and tandem mass spectrometry, and the detection limits were 0.0005-0.005 μg/L for five triazine compounds. Further, the method was applied to the analysis of triazine herbicides in real samples including tap water, sea water, and river water, and the recoveries were 82.8-112.0, 85.4-110.5, and 81.6-105.9%, respectively, with RSDs of 2.7-7.1%.

Azide-functionalized hollow silica nanospheres for removal of antibiotics.

Antibiotics, which are hardly removed from polluted water by conventional water-treatment technologies, adsorption has been deemed as one of the efficient and promising method to resolve the problems of antibiotics pollution. Herein, we reported a synthesis of filtration separable hollow nanostructured silicas (HNSs) with efficient click functionalization property for antibiotics adsorption. The clickable HNSs were synthesized by the co-condensation and assembling of tetramethoxysilane (TMOS) and 3-azidopropyltrimethoxysilane (AzPTMS) around F127 single micelle template. Alkynyl compounds such as phenylacetylene (Ph), propargyl alcohol (PA), 1-heptyne (Hep), and 2-butyne-1,4-diol (BD) have been linked to the materials through click reaction with high efficiency. Antibiotic adsorption results reveal that functional groups play an important role in adsorption properties of adsorbents and phenyl was found to be the optimal functional group due to the π-π stacking effect. Excellent adsorption capacity and recyclability indicate that the clickable hollow nanostructured silicas exhibit potential application for antibiotics removal.

Surface-passivated SBA-15-supported gold nanoparticles: Highly improved catalytic activity and selectivity toward hydrophobic substrates

Silanol groups on a silica surface affect the activity of immobilized catalysts because they can influence the hydrophilicity/hydrophobicity, matter transfer, or even transition state in a catalytic reaction. Previously, these silanol groups have usually been passivated by using surface-passivation reagents, such as alkoxysilanes, bis-silylamine reagents, chlorosilanes, etc., and surface passivation has typically been found in mesoporous-silicas-supported molecular catalysts and heteroatomic catalysts. However, this property has rarely been reported in mesoporous-silicas-supported metal-nanoparticle catalysts. Herein, we prepared an almost-superhydrophobic SBA-15-supported gold-nanoparticle catalyst by using surface passivation, in which the catalytic activity increased more than 14 times for the reduction of nitrobenzene compared with non-passivated SBA-15. In addition, this catalyst can selectively catalyze hydrophobic molecules under our experimental conditions, owing to its high (almost superhydrophobic) hydrophobic properties.