Yuming Huang

CoFe2O4 magnetic nanoparticles as a peroxidase mimic mediated chemiluminescence for hydrogen peroxide and glucose

This communication presents a new peroxidase mimic of CoFe(2)O(4) nanoparticles evaluated by the luminol-based chemiluminescent (CL) reaction. This offers a new method for evaluation and screening of the nanoparticles-based enzyme mimetics.

Copper nanoclusters as a highly sensitive and selective fluorescence sensor for ferric ions in serum and living cells by imaging

A simple, one-step facile route for preparation of water soluble and fluorescent Cu nanoclusters (NCs) stabilized by tannic acid (TA) is described. The as-prepared TA capped Cu NCs (TA-Cu NCs) are characterized by UV-vis spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, luminescence, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The TA-Cu NCs show luminescence properties having excitation and emission maxima at 360 nm and 430 nm, respectively, with a quantum yield of about 14%. The TA-Cu NCs are very stable even in 0.3 M NaCl, and their luminescent properties show pH independent. The fluorescence (FL) of Cu NCs is strongly quenched by Fe(3+) through an electron transfer mechanism, but not by other metal ions. Furthermore, the FL of the TA-Cu NCs shows no changes with the addition of Fe(2+) or H2O2 individually. On this basis, a facile chemosensor was developed for rapid, reliable, sensitive, and selective sensing of Fe(3+) ions with detection limit as low as 10 nM and a dynamic range from 10 nM to 10 μM. The proposed sensor was successfully used for the determination of iron contents in serum samples. Importantly, the Cu NCs-based FL probe showed long-term stability, good biocompatibility and very low cytotoxicity. It was successfully used for imaging ferric ions in living cells, suggesting the potential application of Cu NCs fluorescent probe in clinical analysis and cell imaging.

Hemimicelle capped functionalized carbon nanotubes-based nanosized solid-phase extraction of arsenic from environmental water samples.

The end functionalization of CNTs can introduce oxygen-containing negatively functional groups such as -COOH, -OH, or -CO on their surface site. If cationic surfactant such as cetyltrimethylammonium chloride (CTAC) was added to the functionalized CNTs, then interactions such as hydrophobic and ionic may lead to formation of hemimicelle/admicelle aggregates on the CNTs, a new kind of adsorbents, namely, the hemimicelle capped CMMWCNTs, is obtained. The application of the hemimicelle capped carbon nanotubes-based nanosized solid-phase extraction (SPE) adsorbents in environmental analysis is reported for the first time using arsenic as model target. The effect of adsorption and desorption conditions for arsenic including the amount of surfactant, initial pH of sample solution, the ultrasonic time of sample solution, the amount of electrolyte, flow rate, eluent and its amount were investigated and optimized prior to its determination by atomic fluorescence spectrophotometry (AFS). Arsenic can be quantitatively retained on the hemimicelle capped CMMWCNTs at pH 5-6 from sample volume up to 500 mL and then eluted completely with 2 molL(-1) HNO(3) in the presence of 10 mgL(-1) CTAC. The method detection limit for arsenic determination with AFS detection was 2ngL(-1), and the relative standard deviation (RSD, n=11) was 5.3% at the 0.5 microgL(-1) level. The recoveries of arsenic in the spiked environmental water samples ranged from 94% to 104.29% with 500 mL of water sample. The proposed method has been applied successfully to the analysis of arsenic in aqueous environmental samples, which demonstrates the hemimicelle capped CMMWCNTs can be an excellent SPE adsorbents for arsenic pretreatment and enrichment from real water samples.

β−cyclodextrins-based inclusion complexes of CoFe2O4 magnetic nanoparticles as catalyst for the luminol chemiluminescence system and their applications in hydrogen peroxide detection

beta-cyclodextrins (beta-CD)-based inclusion complexes of CoFe(2)O(4) magnetic nanoparticles (MNPs) were prepared and used as catalysts for chemiluminescence (CL) system using the luminol-hydrogen peroxide CL reaction as a model. The as-prepared inclusion complexes were characterized by XRD (X-ray diffraction), TGA (thermal gravimetric analysis) and FT-IR. The oxidation reaction between luminol and hydrogen peroxide in basic media initiated CL. The effect of beta-CD-based inclusion complexes of CoFe(2)O(4) magnetic nanoparticles and naked CoFe(2)O(4) magnetic nanoparticles on the luminol-hydrogen peroxide CL system was investigated. It was found that inclusion complexes between beta-CD and CoFe(2)O(4) magnetic nanoparticles could greatly enhance the CL of the luminol-hydrogen peroxide system. Investigation on the kinetic curves and the chemiluminescence spectra of the luminol-hydrogen peroxide system demonstrates that addition of CoFe(2)O(4) MNPs or inclusion complexes between beta-CD and CoFe(2)O(4) MNPs does not produce a new luminophor of the chemiluminescent reaction. The luminophor for the CL system was still the excited-state 3-aminophthalate anions (3-APA*). The enhanced CL signals were thus ascribed to the possible catalysis from CoFe(2)O(4) MNPs or inclusion complexes between beta-CD and CoFe(2)O(4) nanoparticles. The feasibility of employing the proposed system for hydrogen peroxide sensing was also investigated. Experimental results showed that the CL emission intensity was linear with hydrogen peroxide concentration in the range of 1.0 x 10(-7) to 4.0 x 10(-6) mol L(-1) with a detection limit of 2.0 x 10(-8) mol L(-1) under optimized conditions. The proposed method has been used to determine hydrogen peroxide in water samples successfully.

CoFe2O4 Nanoparticles as Oxidase Mimic-Mediated Chemiluminescence of Aqueous Luminol for Sulfite in White Wines

Recently, the intrinsic enzyme-like activity of nanoparticles (NPs) has become a growing area of interest. However, the analytical applications of the NP-based enzyme mimetic are mainly concentrated on their peroxidase-like activity; no attempts have been made to investigate the analytical applications based on the oxidase mimic activities of NPs. For the first time, we report that CoFe(2)O(4) NPs were found to possess intrinsic oxidase-like activity and could catalyze luminol oxidation by dissolved oxygen to produce intensified chemiluminescence (CL). The effect of sulfite on CoFe(2)O(4) NP oxidase mimic-mediated CL of aqueous luminol was investigated. It is very interesting that when adding sulfite to the luminol-CoFe(2)O(4) system, the role of sulfite in the luminol-CoFe(2)O(4) NP-sulfite system depends on its concentration. At a relatively low concentration level, sulfite presents an inhibition effect on the luminol-CoFe(2)O(4) NP system. However, it does have an enhancement effect at a higher concentration level. Investigations on the effect of the solution pH and luminol and CoFe(2)O(4) NP concentrations on the kinetic characteristics of the studied CL system in the presence of trace sulfite suggested that the enhancement and inhibition of the luminol-CoFe(2)O(4) NP-sulfite CL system also depended on the solution pH. It seems that the concentrations of luminol and CoFe(2)O(4) NPs did not influence the CL pathway. The possible mechanism of the luminol-CoFe(2)O(4) NP-sulfite CL system was also discussed. On this basis, a flow injection chemiluminescence method was established for the determination of trace sulfite in this study. Under the optimal conditions, the proposed system could respond down to 2.0 × 10(-8) M sulfite. The method has been applied to the determination of trace sulfite in white wine samples with satisfactory results. The results given by the proposed method are in good agreement with those given by the standard titration method.

Eggshell membrane-based solid-phase extraction combined with hydride generation atomic fluorescence spectrometry for trace arsenic(V) in environmental water samples.

The eggshell membrane (ESM) contains several surface functional groups such as amines, amides and carboxylic groups with potential as SPE adsorbent for the retention of target species of interest. In this paper, the potential use of ESM, a typical biomaterial, as solid-phase extraction (SPE) adsorbent is evaluated for analysis of trace arsenic(V) in environmental water samples in combination with hydride generation atomic fluorescence spectrometry (HG-AFS). In order to obtain the satisfactory recovery of arsenic(V), various parameters including the desorption and enrichment conditions such as pH, the flow rate and the volume of sample solution, the amount of ESM and the content of sodium chloride were systematically optimized and the effects of co-existed ions were also investigated in detail. Under the optimal conditions, arsenic(V) could be easily extracted by the ESM packed cartridge and the breakthrough adsorption capacity was found to be 3.9 microg g(-1). The favorable limit of detection (LOD) for arsenic(V) was found to be 0.001 microg L(-1) with an enrichment factor of 33.3, and the relative standard deviations (R.S.Ds) was 2.1% for 0.6 microg L(-1) arsenic (n=11). The reproducibility among columns was satisfactory (R.S.D. among columns is less than 5%). The proposed method has been successfully applied to analysis of arsenic(V) in aqueous environmental samples, which suggests the ESM can be an excellent SPE adsorbent for arsenic(V) pretreatment and enrichment from real water samples.

Fe3O4-MWCNT magnetic nanocomposites as efficient peroxidase mimic catalysts in a Fenton-like reaction for water purification without pH limitation

The Fenton-based reaction is powerful enough to decompose refractory organic pollutants, but it is limited by having a low pH range and it is necessary to have a secondary disposal of the iron sludge. This study demonstrates that Fe3O4–multi-walled carbon nanotube (Fe3O4–MWCNT) magnetic hybrids can be used as an efficient peroxidase mimic catalyst that could overcome such pH limitations in a Fenton-like reaction and could be reused after a simple magnetic separation. The Fe3O4–MWCNT hybrid was prepared using a simple one-pot strategy via in situ growth of Fe3O4 magnetic nanoparticles onto the surface of the MWCNTs. In this process, MWCNTs act as an excellent dispersant, which ensures that the Fe3O4 is well dispersed. The Fe3O4–MWCNT hybrid was characterized by X-ray diffractometry, Fourier transform infrared spectrometer, thermogravimetric analysis and vibrating sample magnetometry, which indicated that the Fe3O4 nanoparticles were successfully deposited on to the surface of MWCNTs. Furthermore, it was revealed that the Fe3O4–MWCNTs could catalyze H2O2 decomposition by acting as a peroxidase mimic catalyst. Then heterogenous Fenton-like reactions were performed using the Fe3O4–MWCNT nanocomposites as a catalyst to degrade methylene blue (10.0 mg L−1; MB) in aqueous solution. The results showed that MB could be efficiently removed in a broad pH range of 1.0–10.0, with a degradation efficiency of 88.13% to 98.68% in two hours, and a highest total organic carbon removal efficiency of 35.6% in 12 hours. Furthermore, the magnetic nanocomposites exhibited an enhanced removal efficiency for MB compared with the Fe3O4 magnetic nanocomparticles and MWCNTs used individually. In addition, Fe3O4–MWCNT nanocomposites exhibited strong magnetism, and thereby could be easily separated from aqueous solution using an external magnetic field. Therefore, the as-prepared Fe3O4–MWCNT nanocomposites could be used as a promising and effective catalyst in Fenton-like reactions for the purification of MB polluted water in a wide pH range.

Mesoporous material-based manipulation of the enzyme-like activity of CoFe2O4 nanoparticles

Mesoporous material supported CoFe2O4 magnetic nanoparticles possess unique peroxidase/oxidase-like activity, and react with luminol to yield a novel chemiluminescence without the need of H2O2. Their oxidase-like activity shows pH and support dependence, and could be reversibly controlled by their pH. This offers a new method for manipulating the enzyme-like activity of nanoparticles.

Metal–organic framework MIL-53(Fe): facile microwave-assisted synthesis and use as a highly active peroxidase mimetic for glucose biosensing

The octahedral structure of MIL-53(Fe) was facilely prepared by a microwave (MW)-assisted approach, and confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The MIL-53(Fe) MOFs were further characterized by thermo gravimetric (TG) analysis and fourier transform infrared (FTIR) spectroscopy. It is found that the as-prepared MIL-53(Fe) exhibits intrinsic peroxidase-like activity, and could catalytically oxidize 3,3′,5,5′-tetramethylbenzidine (TMB), ABTS and OPD by H2O2 to produce a typical coloured reaction. The Michaelis–Menten behavior of the as-prepared MIL-53(Fe) was studied. The Km value of the as-prepared MIL-53(Fe) with H2O2 as the substrate was 0.03 mM, which was at least seven times lower than that of Fe-MIL–88NH2 and hemin@MIL-53(Al)–NH2. Interesting, the Km values of the as-prepared MIL-53(Fe) with H2O2 and TMB as the substrates were both lower than those of the MIL-53(Fe) obtained by conventional electric (CE) heating-based solvothermal method. This is probably attributed to the purely octahedral structure and small sized crystals of the MIL-53(Fe) obtained by MW-based synthesis method, confirming that the MW-based synthesis method promised advantages of simplicity, fast crystallization and good phase selectivity. Results of electron spin resonance (ESR) experiments indicated that the as-prepared MIL-53(Fe) exhibited catalytic ability to decompose H2O2 into ˙OH radicals. On this basis, a simple, sensitive and selective method for glucose detection was developed by coupling the oxidation of glucose catalyzed by glucose oxidase (GOx). As low as 0.25 μM glucose could be detected with a linear range from 0.25–20 μM. The proposed method was successfully used to determine glucose in real human serum samples.

Cigarette filters as adsorbents of solid-phase extraction for determination of fluoroquinolone antibiotics in environmental water samples coupled with high-performance liquid chromatography.

The potential use of cigarette filters (CFs) as solid-phase extraction (SPE) adsorbents for the preconcentration of six fluoroquinolones (FQs) antibacterial agents prior to liquid chromatography was examined in this paper. In order to find a suitable procedure for extraction of the target FQs in one single step, various parameters probably affecting the extraction efficiency including the eluent kind and volume, sample flow rate, pH, ion strength and sample volume were systematically optimized. Under the optimized conditions, the target FQs could be easily extracted by the proposed SPE cartridge. Combination of SPE with HPLC/UV provided detection limits for different FQs of 2-5 ng L(-1) when 500 mL of water sample was processed. The precision of the method, expressed as relative standard deviation, ranged from 4.1 to 6.3% for 2.5 μg L(-1) FQs. The recoveries of FQs spiked in environmental water samples ranged from 76 to 112%. The results obtained from the proposed method demonstrated that CFs-based solid-phase extraction combined with HPLC/UV was suitable for analyzing fluoroquinolones in water samples at ng L(-1) concentration level.