Convolutional Neural Network-Driven Impedance Flow Cytometry for Accurate Bacterial Differentiation.

Impedance flow cytometry (IFC) has been demonstrated to be an efficient tool for label-free bacterial investigation to obtain the electrical properties in real time. However, the accurate differentiation of different species of bacteria by IFC technology remains a challenge owing to the insignificant differences in data. Here, we developed a convolutional neural networks (ConvNet) deep learning approach to enhance the accuracy and efficiency of the IFC toward distinguishing various species of bacteria. First, more than 1 million sets of impedance data (comprising 42 characteristic features for each set) of various groups of bacteria were trained by the ConvNet model. To improve the efficiency for data analysis, the Spearman correlation coefficient and the mean decrease accuracy of the random forest algorithm were introduced to eliminate feature interaction and extract the opacity of impedance related to the bacterial wall and membrane structure as the predominant features in bacterial differentiation. Moreover, the 25 optimized features were selected with differentiation accuracies of >96% for three groups of bacteria (bacilli, cocci, and vibrio) and >95% for two species of bacilli (Escherichia coli and Salmonella enteritidis), compared to machine learning algorithms (complex tree, linear discriminant, and K-nearest neighbor algorithms) with a maximum accuracy of 76.4%. Furthermore, bacterial differentiation was achieved on spiked samples of different species with different mixing ratios. The proposed ConvNet deep learning-assisted data analysis method of IFC exhibits advantages in analyzing a huge number of data sets with capacity for extracting predominant features within multicomponent information and will bring about progress and advances in the fields of both biosensing and data analysis.

Inorganic-Organic Nanoarchitectonics: MXene/Covalent Organic Framework Heterostructure for Superior Microextraction.

One of the difficulties limiting covalent organic frameworks (COFs) from becoming excellent adsorbents is their stacking/aggregation architectures owing to poor morphology/structure control during the synthesis process. Herein, an inorganic-organic nanoarchitectonics strategy to synthesize the MXene/COF heterostructure (Ti3 C2 Tx /TAPT-TFP) is developed by the assembly of ß-ketoenamine-linked COF on the Ti3 C2 Tx MXene nanosheets. The as-prepared Ti3 C2 Tx /TAPT-TFP retains the 2D architecture and high adsorption capacity of MXenes as well as large specific surface area and hierarchical porous structure of COFs. As a proof of concept, the potential of Ti3 C2 Tx /TAPT-TFP for solid-phase microextraction (SPME) of trace organochlorine pesticides (OCPs) is investigated. The Ti3 C2 Tx /TAPT-TFP based SPME method achieves low limits of detection (0.036-0.126 ng g-1 ), wide linearity ranges (0.12-20.0 ng g-1 ), and acceptable repeatabilities for preconcentrating trace OCPs from fruit and vegetable samples. This study offers insights into the potential of constructing COF or MXene-based heterostructures for the microextraction of environmental pollutants.

Phenotyping of single plant cells on a microfluidic cytometry platform with fluorescent, mechanical, and electrical modules.

Compared to animal cells, phenotypic characterization of single plant cells on microfluidic platforms is still rare. In this work, we collated population statistics on the morphological, biochemical, physical and electrical properties of Arabidopsis protoplasts under different external and internal conditions, using progressively improved microfluidic platforms. First, we analyzed the different effects of three phytohormones (auxin, cytokinin and gibberellin) on the primary cell wall (PCW) regeneration process using a microfluidic flow cytometry platform equipped with a single-channel fluorescence sensor. Second, we correlated the intracellular reactive oxygen species (ROS) level induced by heavy metal stress with the concurrent PCW regeneration process by using a dual-channel fluorescence sensor. Third, by integrating contraction channels, we were able to effectively discriminate variations in cell size while monitoring the intensity of intracellular ROS signaling. Fourth, by combining an electrical impedance electrode with the contraction channel, we analyzed the differences in electrical and mechanical properties of wild-type and mutant plant cells before and after primary cell wall regeneration. Overall, our work demonstrates the feasibility and sensitivity of microfluidic flow cytometry in high-throughput phenotyping of plant cells and provides a reference for assessing metabolic and physiological indicators of individual plant cells in multiple dimensions.

MoS2 Hollow Multishelled Nanospheres Doped Fe Single Atoms Capable of Fast Phase Transformation for Fast-charging Na-ion Batteries.

Low Na+ and electron diffusion kinetics severely restrain the rate capability of MoS2 as anode for sodium-ion batteries (SIBs). Slow phase transitions between 2H and 1T, and from NaxMoS2 to Mo and Na2S as well as the volume change during cycling, induce a poor cycling stability. Herein, an original Fe single atom doped MoS2 hollow multishelled structure (HoMS) is designed for the first time to address the above challenges. The Fe single atom in MoS2 promotes the electron transfer, companying with shortened charge diffusion path from unique HoMS, thereby achieving excellent rate capability. The strong adsorption with Na+ and self-catalysis of Fe single atom facilitates the reversible conversion between 2H and 1T, and from NaxMoS2 to Mo and Na2S. Moreover, the buffering effect of HoMS on volume change during cycling improves the cyclic stability. Consequently, the Fe single atom doped MoS2 quadruple-shelled sphere exhibits a high specific capacity of 213.3 mAh g-1 at an ultrahigh current density of 30 A g-1, which is superior to previously-reported results. Even at 5 A g-1, 259.4 mAh g-1 (83.68 %) was reserved after 500 cycles. Such elaborate catalytic site decorated HoMS is also promising to realize other "fast-charging" high-energy-density rechargeable batteries.

Unlocking Enhanced Capacitive Deionization of NaTi2(PO4)3/Carbon Materials by the Yolk-Shell Design.

The low salt adsorption capacities (SACs) of benchmark carbon materials (usually below 20 mg g-1) are one of the most challenging issues limiting further commercial development of capacitive deionization (CDI), an energetically favorable method for sustainable water desalination. Sodium superionic conductor (NASICON)-structured NaTi2(PO4)3 (NTP) materials, especially used in combination with carbon to prepare NTP/C materials, provide emerging options for higher CDI performance but face the problems of poor cycling stability and dissolution of active materials. In this study, we report the development of the yolk-shell nanoarchitecture of NASICON-structured NTP/C materials (denoted as ys-NTP@C) using a metal-organic framework@covalent organic polymer (MOF@COP) as a sacrificial template and space-confined nanoreactor. As expected, ys-NTP@C exhibits good CDI performance, including exemplary SACs with a maximum SAC of 124.72 mg g-1 at 1.8 V in the constant-voltage mode and 202.76 mg g-1 at 100 mA g-1 in the constant-current mode, and good cycling stability without obvious performance degradation or energy consumption increase over 100 cycles. Furthermore, X-ray diffraction used to study CDI cycling clearly exhibits the good structural stability of ys-NTP@C during repeated ion intercalation/deintercalation processes, and the finite element simulation shows why yolk-shell nanostructures exhibit better performance than other materials. This study provides a new synthetic paradigm for preparing yolk-shell structured materials from MOF@COP and highlights the potential use of yolk-shell nanoarchitectures for electrochemical desalination.

Sustainable synthesis of hydroxyl-functional porous organic framework as novel adsorbent for effective removal of organic micropollutants from water.

Organic micropollutants (OMPs) in water resources are a growing threat to aquatic ecosystems and human health. Efficient removal of polar OMPs is very challenging because of their high hydrophility. Synthesizing novel adsorbent capable of high-efficiently removing hydrophilic and hydrophobic micropollutants is highly desirable for water remediation. Here, using natural proanthocyanidin as building units, a novel hydroxyl-functional porous organic framework (denoted as PC-POF) with amphiphilic feature was synthesized through facile azo coupling reaction. Five sulfonamide antibiotics were selected as model OMPs for adsorption study. Adsorption experiments demonstrated a more rapid and efficient sulfonamides capture ability of the PC-POF than that of the most reported adsorbents due to strong hydrogen bonding, π stacking and electrostatic interactions. The PC-POF can be easily recovered and reused at least 5 times without obvious decline in adsorption performance. Moreover, experiments conducted at environmentally relevant concentrations (µg L-1) further confirmed a notable adsorption performance of the PC-POF even when the sulfonamides solution was rapidly passed through the PC-POF packed column. The PC-POF also showed good adsorption performance for other micropollutants like neonicotinoid insecticides, nitroimidazole antibiotics and triazine herbicides, indicating a promising prospect. This work provides a new strategy to construct amphiphilic adsorbent by using renewable resources for pollutants removal.

Triazine-based covalent organic polymer: A promising coating for solid-phase microextraction.

Advancement of novel coating materials for solid-phase microextraction is highly needed for sample pretreatment. Herein, a triazine-based covalent organic polymer was constructed from the monomers of cyanuric chloride and trans-stilbene via the Friedel-Crafts reaction and thereafter used as a solid-phase microextraction fiber coating for the extraction of polycyclic aromatic hydrocarbons and their nitrated and oxygenated derivatives. The newly-developed solid-phase microextraction method coupled with gas chromatography/flame ionization detection gives enhancement factors of 548-1236 and limits of detection of 0.40-2.81 ng/L for the determination of polycyclic aromatic hydrocarbons and their derivatives. The one fiber precision for five replicate determinations of the analytes and the fiber-to-fiber precision with three parallel prepared fibers, expressed as relative standard deviations, was in the range of 4.6-9.4% and 6.2-10.9%, respectively. The relative recoveries of the analytes for environmental water samples were in the range of 88.6-106.4% with the relative standard deviations ranging from 4.0 to 11.7% (n = 5).

Label-Free and Simultaneous Mechanical and Electrical Characterization of Single Plant Cells Using Microfluidic Impedance Flow Cytometry.

Despite that single-cell-type-level analyses have been extensively conducted on animal models to gain new insights into complex biological processes; the unique biological and physiological properties of plant cells have not been widely studied at single-cell resolution. In this work, an electrical impedance flow cytometry was fabricated based on microfluidics with constriction microchannel to simultaneously characterize the mechanical and electrical properties of single plant cells. Protoplasts from two model plant species, the herbaceous Arabidopsis thaliana and the woody Populus trichocarpa, could be readily discriminated by their respective mechanical traits, but not by electrical impedance. On the contrary, overexpression of a red fluorescent protein on plasma membrane resulted in changes in cell electrical impedance instead of cell deformability. During primary cell wall (PCW) regeneration, this extracellular layer outside of protoplasts introduced dramatic variations in both mechanical and electrical properties of single plant cells. Furthermore, the effects of auxin, an essential phytohormone regulating PCW reformation, were validated on this platform. Taken together, our results revealed a novel application of microfluidic impedance flow cytometry in the field of plant science to simultaneously characterize dual biophysical properties at single-cell resolution, which could be further developed as a powerful and reliable tool for plant cell phenotyping and cell fate specification.

Rational Design of Nanoporous MoS2 /VS2 Heteroarchitecture for Ultrahigh Performance Ammonia Sensors.

2D transition metal dichalcogenides (TMDs) have received widespread interest by virtue of their excellent electrical, optical, and electrochemical characteristics. Recent studies on TMDs have revealed their versatile utilization as electrocatalysts, supercapacitors, battery materials, and sensors, etc. In this study, MoS2 nanosheets are successfully assembled on the porous VS2 (P-VS2 ) scaffold to form a MoS2 /VS2 heterostructure. Their gas-sensing features, such as sensitivity and selectivity, are investigated by using a quartz crystal microbalance (QCM) technique. The QCM results and density functional theory (DFT) calculations reveal the impressive affinity of the MoS2 /VS2 heterostructure sensor toward ammonia with a higher adsorption uptake than the pristine MoS2 or P-VS2 sensor. Furthermore, the adsorption kinetics of the MoS2 /VS2 heterostructure sensor toward ammonia follow the pseudo-first-order kinetics model. The excellent sensing features of the MoS2 /VS2 heterostructure render it attractive for high-performance ammonia sensors in diverse applications.

Carbon nanospheres as solid-phase microextraction coating for the extraction of polycyclic aromatic hydrocarbons from water and soil samples.

A solid-phase microextraction with carbon nanospheres coated fiber coupled with gas chromatographic detection was established for the determination of eight polycyclic aromatic hydrocarbons (naphthalene, biphenyl, acenaphthene, fluorine, phenanthrene, anthracene, fluoranthene, and pyrene) in water and soil samples. The experimental parameters (extraction temperature, extraction time, stirring rate, headspace volume, salt content, and desorption temperature) which affect the extraction efficiency were studied. Under the optimized conditions, good linearity between the peak areas and the concentrations of the analytes was achieved in the concentration range of 0.5-300 ng/mL for water samples, and in the concentration range of 6.0-2700 ng/g for soil samples. The detection limits for the analytes were in the range of 0.12-0.45 ng/mL for water samples, and in the range of 1.53-2.70 ng/g for soil samples. The method recoveries of the polycyclic aromatic hydrocarbons for spiked water samples were 80.10-120.1% with relative standard deviations less than 13.9%. The method recoveries of the analytes for spiked soil samples were 80.40-119.6% with relative standard deviations less than 14.4%. The fiber was reused over 100 times without a significant loss of extraction efficiency.

Rational integration of porous organic polymer and multiwall carbon nanotube for the microextraction of polycyclic aromatic hydrocarbons.

By integration of benzene-constructed porous organic polymer (KBF) and multiwalled carbon nanotube (MWCNT), a MWCNT-KBF hybrid material was constructed through in situ knitting benzene with formaldehyde dimethyl acetal in the presence of MWCNTs to form a network. MWCNT-KBF was then adopted as a novel solid-phase microextraction (SPME) fiber coating. Coupled to gas chromatography-flame ionization detection, the MWCNT-KBF-assisted SPME method showed large enhancement factors (483-2066), low limits of detection (0.04-0.12 µg L-1), good linearity (0.13-50 µg L-1), and acceptable reproducibility (4.2-10.2%) for the determination of polycyclic aromatic hydrocarbons (PAHs). The method recoveries of seven PAHs were in the range 80.1-116.3%, with relative standard deviations (RSDs) ranging from 3.5 to 11.9%. The SPME method was successfully applied to the determination of PAHs in river, pond, rain, and waste water, providing a good alternative for monitoring trace level of PAHs in environmental water. Graphical abstract Schematic representation of the rational integration of porous organic polymer (KBF) and multiwalled carbon nanotube (MWCNT) to form a MWCNT-KBF hybrid material through in situ knitting benzene with formaldehyde dimethyl acetal at the presence of MWCNT.

Solid phase microextraction of polycyclic aromatic hydrocarbons by using an etched stainless-steel fiber coated with a covalent organic framework.

A new covalent organic framework (COF) was synthesized by the amide coupling between 1,3,5-tris(4-aminophenyl)benzene and trimesoyl chloride at room temperature. The COF was applied as a steel fiber coating for the solid phase microextraction of polycyclic aromatic hydrocarbons (PAHs) from water samples. The effect of extraction time, salt concentration, and extraction temperature on the efficiency of SPME was optimized by a Box-Behnken design. The PAHs were quantified by gas chromatography with mass spectrometric detection. Figures of merit include (a) a wide linear range (typically from 0.2 ng L-1 to 2 µg L-1), (b) low limits of detection (0.29 to 0.94 ng L-1 at S/N = 3), and (c) high enrichment factors (EFs; 819-2420). Density functional theory was employed to study the interaction between the COF cluster and the PAHs. The results demonstrated that the EFs increase with the enhancement of π stacking interaction. The repeatability (one fiber; n = 5) and reproducibility (fiber to fiber; n = 5), expressed as the relative standard deviations were in the range of 4.3%-8.4% and 8.5-11.0%, respectively. The recoveries of the PAHs from water samples spiked at levels of 20.0 and 100 ng L-1 ranged from 79.0% to 105.0%. Graphical abstract A covalent organic framework prepared from 1,3,5-tris(4-aminophenyl)benzene and trimesoyl chloride (TAPB-TMC-COF) was synthesized and employed as solid phase microextraction (SPME) fiber coating for the extraction of polycyclic aromatic hydrocarbons from water samples prior to gas chromatography (GC) - mass spectrometric (MS) detection.

Defect-Rich Graphene Nanomesh Produced by Thermal Exfoliation of Metal-Organic Frameworks for the Oxygen Reduction Reaction.

Although graphene nanomesh is an attractive 2D carbon material, general synthetic routes to produce functional graphene nanomesh in large-scale are complex and tedious. Herein, we elaborately design a simple two-step dimensional reduction strategy for exploring nitrogen-doped graphene nanomesh by thermal exfoliation of crystal- and shape-modified metal-organic frameworks (MOFs). MOF nanoleaves with 2D rather than 3D crystal structure are used as the precursor, which are further thermally unraveled into nitrogen-doped graphene nanomesh by using metal chlorides as the exfoliators and etching agent. The nitrogen-doped graphene nanomesh has a unique ultrathin two-dimensional morphology, high porosity, rich and accessible nitrogen-doped active sites, and defective graphene edges, contributing to an unprecedented catalytic activity for the oxygen reduction reaction (ORR) in acid electrolytes. This approach is suitable for scalable production.

Synthesis of nanoporous poly-melamine-formaldehyde (PMF) based on Schiff base chemistry as a highly efficient adsorbent.

This study proposes the construction of nanoporous poly-melamine-formaldehyde (PMF) through the Schiff base condensation reaction of paraformaldehyde and melamine. The PMF nanoparticles showed a good adsorption capability to some benzene-ring-containing dyes including acid fuchsine, nigrosine, and methyl orange. Moreover, the as-prepared PMF nanoparticles were employed as the coating adsorbent for the solid-phase microextraction (SPME) of seven volatile fatty acids (VFAs) with high enrichment factors. A PMF-assisted SPME method was established for the enrichment of VFAs from environmental water samples with satisfactory recoveries (88.5%-102.0%) and acceptable precisions (relative standard deviations <10.9%). This contribution might furnish an advanced benchmark for the exploitation of new porous organic polymers as the effective adsorbents for SPME or other fields of utilization.

Fibrous boron nitride nanocomposite for magnetic solid phase extraction of ten pesticides prior to the quantitation by gas chromatography.

A fibrous magnetic boron nitride nanocomposite was synthesized and is shown to be a viable adsorbent for the magnetic solid phase extraction of pesticides prior to their quantitation by gas chromatography with electron capture detection. The optimum conditions were obtained by both single factor optimization and response surface analysis (Box-Behnken design). Under the optimized conditions, the response to the ten pesticides (dicofol, α-endosulfan, p,p'-DDE, nitrofen, ß-endosulfan, p,p'-DDD, p,p'-DDT, bifenthrin, permethrin and fenvalerate) is linear in the 0.03-40 ng·mL-1 concentration range with the coefficients of determination ranging from 0.9970 to 0.9992. The relative standard deviations at concentration levels of 0.5 ng·mL-1, 20 ng·mL-1 and 40 ng·mL-1 were below 8.7%. The recoveries of the analytes from spiked tea water and tea beverage samples varied between 84.5% and 122%, with relative standard deviations ranging from 4.8 to 12%. The limits of detection are between 0.01 and 0.05 ng·mL-1. The adsorbent can be reused over 50 times without significant loss of extraction efficiency. Graphical abstract A novel fibrous-shape magnetic boron nitride nanocomposite (Fe3O4@f-BN) was used as the adsorbent for the magnetic solid phase extraction (MSPE) of ten pesticides from tea water and tea beverage samples prior to their determination by gas chromatography (GC).

Covalent organic frameworks as a novel fiber coating for solid-phase microextraction of volatile benzene homologues.

Covalent organic frameworks (COFs) have attracted great research interest due to their fascinating structures and potential applications in various fields. Here, the COF-SCU1 (SCU for Sichuan University) coated solid-phase microextraction (SPME) fibers were fabricated by coating it on prior functionalized stainless steel wires via a simple physical coating method, and applied to extract some volatile benzene homologues from indoor air samples. The main experimental parameters affecting the extraction efficiency were optimized, including extraction temperature, extraction time, and desorption time. The developed method, which combined the COF-SCU1 coated fiber-based SPME with gas chromatography-mass spectrometric detection, gave large enrichment factors (276-887), low limits of detection (0.03-0.15 ng L-1), and good linearity (0.10-20 ng L-1) for the determination of gaseous benzene homologues from three different indoor air samples. The precision (expressed as the relative standard deviations, RSDs) for six replicate determinations of the analytes at 10 ng L-1 each of the analytes using the same COF-SCU1 coated fiber ranged from 5.8 to 8.9%. The fiber-to-fiber reproducibility for three parallel COF-SCU1 coated fibers varied from 6.9 to 10.7%. The recoveries of the analytes for the method for the spiked indoor air samples with the benzene homologues at the two concentrations of 1 and 10 ng L-1 were in the range of 88.6-101.5% and 87.9-103.4% with the RSDs ranging from 3.9 to 10.3% and 3.4 to 8.5%, respectively. Graphical Abstract The covalent organic frameworks were applied as a novel fiber coating material for the solid-phase microextraction of volatile benzene homologues.

Microextraction of polycyclic aromatic hydrocarbons by using a stainless steel fiber coated with nanoparticles made from a porous aromatic framework.

A porous aromatic framework of type PAF-6 was synthesized and explored as a coating onto a steel wire for using in solid-phase microextraction of polycyclic aromatic hydrocarbons (PAHs), phthalate plasticizers, and n-alkanes. The extraction temperature, extraction time, salt concentration, agitation speed, desorption temperature, and desorption time were optimized. This method for SPME resulted in the enrichment factors ranging from 122 to 1090 for PAHs (naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene), from 122 to 271 for plasticizers (diisobutyl phthalate, dibutyl phthalate, benzyl butyl phthalate, dicyclohexyl phthalate), and from 9 to 113 for n-alkanes (n-undecane, n-dodecane, n-tridecane, n-tetradecane, n-pentadecane, n-hexadecane, n-octadecane and n-eicosane). The good extraction of the PAHs is assumed to be due to their π-stacking interaction and hydrophobic effect. The PAF-6 coated fibers are durable and can be reused more than 100 times without significant loss of extraction performance. In combination with GC-MS detection, the method has limits of detection in the range from 0.8 to 4.2 ng L-1 in case of PAHs. The relative standard deviations for five replicate determinations of the PAHs by using one fiber are in the range from 5.2 to 8.5%. When using different fibers, they range from 7.1 to 9.6%. The recoveries of PAHs from water samples at a spiking level of 20 ng L-1 are in the range from 89.5 to 103.1%, with relative standard deviations ranging from 4.0 to 9.3%. Graphical abstract A porous aromatic framework of type PAF-6 was synthesized and used as a novel coating for the solid-phase microextraction of polycyclic aromatic hydrocarbons prior to their determination by gas chromatography with mass spectrometric detection.

Zeolitic imidazole framework templated synthesis of nanoporous carbon as a novel fiber coating for solid-phase microextraction.

A new solid-phase microextraction (SPME) fiber coating material, a zeolitic imidazole framework-67 (ZIF-67) templated nanoporous carbon, Co-NPC, was fabricated by one-step direct carbonization of ZIF-67 without using any other carbon precursors. The prepared Co-NPC was then coated onto a functionalized stainless steel wire by a simple physical coating method to prepare SPME fibers. By coupling the Co-NPC coated fiber based SPME with gas chromatography/micro-electron capture detection (GC/µECD), the developed method exhibited low limits of detection (0.07-0.45 ng g(-1)) and a wide linearity (0.30-50 ng g(-1)) for the determination of five organochlorine pesticides (OCPs) in vegetable samples. The method was applied to the analysis of cabbage, cucumber and celery cabbage samples, and the recoveries of the analytes were in the range of 87.9-103.9% with the relative standard deviations (RSDs) ranging from 5.1% to 10.4% (n = 5). Single fiber repeatability and fiber-to-fiber reproducibility values expressed as RSDs were in the range of 4.9-9.6% and 5.8-11.0%, respectively. The method was simple, convenient and feasible for the determination of OCPs in real samples.

Application of a solid-phase microextraction fiber coated with a graphene oxide-poly(dimethylsiloxane) composite for the extraction of triazoles from water.

A solid-phase microextraction fiber was prepared by mixing graphene oxide and hydroxyl-terminated polydimethylsiloxane together and then coating the mixture on the surface of etched stainless-steel wire by sol-gel technology. After aging by heating, the graphene oxide-polydimethylsiloxane composite coated fiber was used for the direct solid phase microextraction of triazole fungicides from water samples. The properties of the graphene oxide-polydimethylsiloxane coating were characterized by transmission electron microscopy and thermogravimetric analysis. And the chemical stability of the coating was tested as well. Several important experimental parameters that could influence the extraction efficiency such as desorption temperature and time, extraction temperature and time, sample pH and stirring rate, were investigated and optimized. Under the optimized conditions, the limits of detection were in the range from 0.01 to 0.03 µg/L. The results indicated that the homemade fiber had the advantages of good thermal and chemical stability and high extraction efficiency, which was successfully applied to the analysis of triazoles in water samples.

Cyclodextrin-functionalized reduced graphene oxide as a fiber coating material for the solid-phase microextraction of some volatile aromatic compounds.

A novel solid phase microextraction fiber was prepared for the first time by using a sol-gel technique with hydroxypropyl-ß-cyclodextrin-functionalized reduced graphene oxide as the fiber coating material. The results verified that the ß-cyclodextrin was successfully grafted onto the surface of reduced graphene oxide and the coating possessed a uniform folded and wrinkled structure. The performance of the solid phase microextraction fiber was evaluated by using it to extract nine volatile aromatic compounds from water samples before determination with gas chromatography and flame ionization detection. Some important experimental parameters that could affect the extraction efficiency such as the extraction time, extraction temperature, desorption temperature, desorption time, the volume of water sample solution, stirring rate, as well as ionic strength were optimized. The new method was validated to be effective for the trace analysis of some volatile aromatic compounds, with the limits of detection ranging from 2.0 to 8.0 ng/L. Single fiber repeatability and fiber-to-fiber reproducibility were in the range of 2.5-9.4 and 5.4-12.9%, respectively. The developed method was successfully applied to the analysis of three different water samples, and the recoveries of the method were in the range from 77.9 to 113.6% at spiking levels of 10, 100, and 1000 ng/L, respectively.