Influence of urban morphological parameters on the distribution and diffusion of air pollutants: A case study in China.

Air pollution has a serious fallout on human health, and the influences of the different urban morphological characteristics on air pollutants cannot be ignored. In this study, the relationship between urban morphology and air quality (wind speed, CO, and PM2.5) in residential neighborhoods at the meso-microscale was investigated. The changes in the microclimate and pollutant diffusion distribution in the neighborhood under diverse weather conditions were simulated by Computational Fluid Dynamics (CFD). This study identified five key urban morphological parameters (Building Density, Average Building Height, Standard Deviation of Building Height, Mean Building Volume, and Degree of Enclosure) which significantly impacted the diffusion and distribution of pollutants in the neighborhood. The findings of this study suggested that three specific strategies (e.g. volume of a single building should be reduced, DE should be increased) and one comprehensive strategy (the width and height of the single building should be reduced while the number of single buildings should be increased) could be illustrated as an optimized approach of urban planning to relief the air pollution. The result of the combined effects could provide a reference for mitigating air pollution in sustainable urban environments.

Alkali metal-modified C-FDU-15: Highly efficient adsorbents for adsorption of NO and O2 at low temperatures.

The alkali metal (M = Na, K, Rb, and Cs)-modified C-FDU-15 (M-C-FDU-15(x); x was the M/C-FDU-15 M ratio, and equal to 0.01-0.03) samples were prepared through an in situ process, and characterized by means of the TG, XRD, TEM, EDS, N2 adsorption-desorption, O2-TPD, and CO2-TPD techniques. The (NO + O2) adsorption mechanism was investigated using the (NO + O2)-TPD and DRIFTS techniques. The results show that the sequence of (NO + O2) adsorption performance was Na-C-FDU-15(0.01) (104.1 mg/g) > K-C-FDU-15(0.01) (92.4 mg/g) > C-FDU-15 (76.2 mg/g) > Rb-C-FDU-15(0.01) (65.1 mg/g) > Cs-C-FDU-15(0.01) (62.3 mg/g). The alkali metal was uniformly distributed in C-FDU-15 and its doping enhanced the amount of the basic sites in the sample. Moreover, the optimal Na/C-FDU-15 M ratio was 0.02. (NO + O2) were chemically adsorbed mainly in the forms of nitrite (NO2-) and nitrate (NO3-) on M-C-FDU-15(x). A more amount of NO was converted to nitrate than to nitrite. There were three key factors of enhancing the (NO + O2) adsorption capacity of C-FDU-15 due to alkali metal doping: the first factor was the increasing of surface area and pore volume of the sample, the second one was the enhancement in amount of the active sites in the sample, and the third one was the smaller alkali metal ionic radius in the sample.

Sandwich magnetically imprinted immunosensor for electrochemiluminescence ultrasensing diethylstilbestrol based on enhanced luminescence of Ru@SiO2 by CdTe@ZnS quantum dots.

A molecularly imprinted magnetic sensor with electroluminescent tags (MIP-ECL sensor) was developed for ultrasensing diethylstilbestrol (DES). A strategy is exploited to enhance ECL emission of the [Ru(bpy)3]2 +-tripropyl amine (TPrA) system by CdTe@ZnS quantum-dots (QDs) through energy transfer. Magnetically molecularly imprinted nanoparticles (MMIPs NPs) based on Fe3O4@SiO2 carriers are artificial, easily reproducible, and could replace easily inactivated first antibodies for capturing more DES molecules. Functionalized bio-conjugates of single antibody-CdTe@ZnS (Ab-CdTe@ZnS) are for the first time loaded on signal labels of Ru(bpy)32 +-doped silica nanocomposites (Ru@SiO2) for signal amplification. The final bio-conjugated signal probes are denoted as Ab-DES/CdTe@ZnS-Ru@SiO2. MMIPs beads that have captured antigens are bio-conjugated with antibody-labeled luminescent probes by specific immunoreactive reaction, and then the luminescent immunocomplex generates ECL signal on the magnetic electrode. The logarithm of ECL intensities depend linearly on the logarithm of DES concentrations in the range from 4.8 × 10- 4 to 36.0 nM with a detection limit of 0.025 pM. This novel assay is much more sensitive than other MIP sensors, and achieves lower cost and more enhanced stability than other immunosensors. The sensor is significantly potential and has been applied to DES detection in actual environment.

Adsorption performance of CMK-3 and C-FDU-15 in NO removal at low temperature.

CMK-3 and C-FDU-15 samples were synthesized using hard-templating and evaporation-induced self-assembly (EISA) methods, respectively. The pore structures of CMK-3 and C-FDU-15 as well as commercial activated carbon were characterized by means of X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and N2 adsorption-desorption. Adsorption of NO was investigated by means of thermogravimetric analysis, temperature-programmed desorption of NO + O2, and in situ diffuse reflectance Fourier transform infrared spectroscopy. The results show that the CMK-3 and C-FDU-15 materials possessed ordered and uniform structures. The co-adsorption capacity of NO and O2 decreased in the sequence CMK-3 (88.6 mg/g) > C-FDU-15 (71.7 mg/g) > AC (25.3 mg/g). There were two main adsorption species on CMK-3 and C-FDU-15: nitrite and nitrate. Nitrite is converted to nitrate easily. However, the adsorption species were more complex on AC, with nitrite being the main species. Moreover, CMK-3 and C-FDU-15 exhibit excellent regeneration efficiency compared with AC. The excellent NO adsorption performance of CMK-3 and C-FDU-15 was associated with their ordered mesoporous structures and high surface areas. The research provides more options for NO adsorption in the future.

Molecular beacon immobilized on graphene oxide for enzyme-free signal amplification in electrochemiluminescent determination of microRNA.

An electrochemiluminescence (ECL) based biosensor is described for determination of microRNAs in the A549 cell line. Firstly, graphene oxide (GO) is dripped onto a glassy carbon electrode surface to form an interface to which one end of the capture probe (with a stem-loop structure) can be anchored through π-interaction via dangling unpaired bases. The other end of the capture probe is directed away from the GO surface to make it stand upright. Target microRNAs can open the hairpin structure to form a double-stranded DNA-RNA structure. Two auxiliary probes, generating a hybridization chain reaction, are used to elongate the DNA duplex. Finally, doxorubicin-modified cadmium telluride quantum dot nanoparticles (Dox-CdTe QD) are intercalated into the base pairs of the hybrid duplexes to act as signalling molecules. The ECL signal of the Dox-CdTe QD increases proportionally with the concentration of microRNAs, specifically for microRNA-21. The assay covers a wide linear range (1 fM to 0.1 nM), has a low detection limit for microRNA-21 (1 fM), and is selective, reproducible, and stable. Graphical abstract An enzyme-free amplification electrochemiluminescent assay is described to quantitative detection of microRNA in the A549 cell line. Graphene oxide was used to immobilize capture probes obviating the special modification. Doxorubicin-modified cadmium telluride quantum dot nanoparticles are intercalated into the base pairs of the hybrid duplexes to act as signalling molecules.

Magnetic surface molecularly imprinted poly(3-aminophenylboronic acid) for selective capture and determination of diethylstilbestrol.

Diethylstilbestrol (DES) is considered a representative example of an exogenous endocrine disrupting compound (EDC). It can retard development in infants, lead to serious metabolic regulation disorders, and even result in distortion and cancer in the reproductive system. Therefore, achieving rapid and accurate analysis of trace amounts of DES in complex environments is of great importance to human health and for environmental protection. Novel magnetic molecularly imprinted polymers (MIPs) with excellent molecular recognition ability and super water-compatibility were developed for the selective capture of DES in water samples. Fe3O4@SiO2 magnetic nanoparticles (NPs) were synthesized and used as support cores. Molecularly imprinted poly(3-aminophenylboronic acid) (poly(APBA)), synthesized on magnetic cores based on a surface-imprinting strategy, can preferentially bind DES molecules in water samples. The magnetic core-shell MIPs (denoted as Fe3O4@SiO2@APBA/MIPs) exhibited high binding capacity and favorable recognition specificity for DES in water. The adsorption kinetics and experimental isotherm data of DES on magnetic MIPs can be well described by the pseudo-second-order kinetic model and the Langmuir isotherm, respectively. The imprinted nanoparticles were subjected to magnetic solid-phase extraction (MSPE) of DES from water samples. The DES content in the samples was determined by high-performance liquid chromatography (HPLC). The peak area increased linearly with increasing DES concentration over the range 0.08-150 µg L-1, with a detection limit of 0.03 µg L-1. The recoveries for spiked lake water samples were in the range 97.1-103.2%, with relative standard deviation (RSD) of 2.8-4.3% (n = 6).

Highly sensitive aptasensor based on synergetic catalysis activity of MoS2-Au-HE composite using cDNA-Au-GOD for signal amplification.

Single or few-layer nanosheets of MoS2 (MoS2 nanosheets) and a composite composed of MoS2 nanosheets, Au nanoparticles (AuNPs) and hemin (HE) (denoted as MoS2-Au-HE) were prepared. The composites possessed high synergetic catalysis activity towards the electroreduction of hydrogen peroxide. Furthermore, glucose oxidase (GOD) and AuNPs were used as marker of the complementary DNA (cDNA) strand of kanamycin aptamer to prepare a conjugate (reffered as cDNA-Au-GOD) that was designed as the signal probe. Both cDNA-Au-GOD and MoS2-Au-HE were applied to fabricate aptasensor for kanamycin. MoS2-Au-HE acted as solid platform for kanamycin aptamer and signal transmitters. AuNPs were employed as the supporter of cDNA and GOD which catalyze dissolved oxygen to produce hydrogen peroxide in the presence of glucose. Then cathodic peak current of H2O2 was recorded by differential pulse voltammetry (DPV). The electrochemical reduction of H2O2 was catalyzed by MoS2-Au-HE that was modified onto the surface of a glassy carbon electrode (GCE). The cathodic peak current of H2O2 was highly linearly decreased with an increase of kanamycin concentrations from 1.0ng/L to 1.0×105ng/L, with a detection limit of 0.8ng/L. This aptasensor can be used to detect kanamycin in milk with high specificity, sensitivity and selectivity.

Investigation of perfluorooctanoic acid induced DNA damage using electrogenerated chemiluminescence associated with charge transfer in DNA.

An electrogenerated chemiluminescence (ECL)-DNA sensor was designed and fabricated for the investigation of DNA damage by a potential environmental pollutant, perfluorooctanoic acid (PFOA). The ECL-DNA sensor consisted of a Au electrode that had a self-assembled monolayer of 15 base-pair double-stranded (ds) DNA oligonucleotides with covalently attached semiconductor CdSe quantum dots (QDs) at the distal end of the DNA. Characterization of the ECL-DNA sensor was conducted with X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), ECL, and cyclic voltammetry before and after the exposure of the sensor to PFOA. Consistent data revealed that the dsDNA on Au was severely damaged upon the incubation of the electrode in PFOA, causing significant increase in charge (or electron) transfer (CT) resistance within DNA strands. Consequently, the cathodic coreactant ECL responses of the Au/dsDNA-QDs electrode in the presence of K2S2O8 were markedly decreased. The strong interaction between DNA and PFOA via the hydrophobic interaction, especially the formation of F···H hydrogen bonds by insertion of the difluoro-methylene group of PFOA into the DNA base pairs, was believed to be responsible for the dissociation or loosening of dsDNA structure, which inhibited the CT through DNA. A linear relationship between the ECL signal of the sensor and the logarithmical concentration of PFOA displayed a dynamic range of 1.00 × 10(-14)-1.00 × 10(-4) M, with a limit of detection of 1.00 × 10(-15) M at a signal-to-noise ratio of 3. Graphical Abstract Illustration of ECL detection of PFOA on a Au/dsDNA-QDs ECL-DNA sensor.

Intense charge transfer surface based on graphene and thymine-Hg(II)-thymine base pairs for detection of Hg(2.).

In this article, we developed an electrochemiluminescence (ECL) sensor with a high-intensity charge transfer interface for Hg(2+) detection based on Hg(II)-induced DNA hybridization. The sensor was fabricated by the following simple method. First, graphene oxide (GO) was electrochemically reduced onto a glassy carbon electrode through cyclic voltammetry. Then, amino-labeled double-stranded (ds)DNA was assembled on the electrode surface using 1-pyrenebutyric acid N-hydroxysuccinimide as a linker between GO and DNA. The other terminal of dsDNA, which was labeled with biotin, was linked to CdSe quantum dots via biotin-avidin interactions. Reduced graphene oxide has excellent electrical conductivity. dsDNA with T-Hg(II)-T base pairs exhibited more facile charge transfer. They both accelerate the electron transfer performance and sensitivity of the sensor. The increased ECL signals were logarithmically linear with the concentration of Hg(II) when Hg(2+) was present in the detection solution. The linear range of the sensor was 10(-11) to 10(-8)mol/L (R=0.9819) with a detection limit of 10(-11)mol/L. This biosensor exhibited satisfactory results when it was used to detect Hg(II) in real water samples. The biosensor with high-intense charge transfer performance is a prospect avenue to pursue more and more sensitive detection method.

Bi-functionalized aptasensor for ultrasensitive detection of thrombin.

A novel bi-functionalized aptasensor for thrombin detection was fabricated by using electrochemiluminescence (ECL) and electrochemical impedance spectroscopy (EIS) techniques. A thiol-terminated aptamer with 15 oligonucleotides was hybridized with its complementary oligonucleotides to form a double-stranded DNA (dsDNA). Then, the thiol-labeled dsDNA was assembled on a Au electrode via Au-S bond; the other distal of the dsDNA labeled with biotin was bound to QDs through a biotin-avidin conjugation. When thrombin is present in the detection solution, the aptamer can combine with thrombin, resulting in loss of CdSe QDs from the electrode surface and thereby decreasing the ECL intensity and increasing the impedance. The decreased ECL and increased EIS signals are logarithmically linear with respect to the concentration of thrombin. The linear range was 10(-10)-10(-3) µg mL(-1) (R=0.9924) for the ECL signal and 10(-10)-10(-1) µg mL(-1) (R=0.9875) for the EIS method with a common detection limit of 10(-10) µg mL(-1) (2.7 aM). In addition, the bi-functionalized aptasensor exhibited excellent selectivity, super sensitivity, a low detection limit and a wide linear range.

Investigation of DNA damage treated with perfluorooctane sulfonate (PFOS) on ZrO2/DDAB active nano-order film.

The interactions between DNA and small molecules with planar heterocyclic structure were indicated in previous researches. This study investigated the interactions between PFOS with linear chain structure and DNA. A new phenomenon of DNA damage due to PFOS using electrochemistry technique was proved. The data was obtained on a modified glassy carbon electrode, on which didodecyldimethylammonium bromide (DDAB), ZrO(2) and calf thymus DNA were immobilized layer-by-layer. Electrochemical response of DNA damage caused by PFOS was detected by differential pulse voltammetry (DPV) using methylene blue (MB) as electro-active indicator. The current of MB attenuated obviously after DNA/ZrO(2)/DDAB/GCE were incubated in PFOS. The shift of MB reduction peak potential indicates that PFOS is bound with DNA in groove probably by the first step of hydrophobic interaction and then the second step of intercalation into the base of DNA. X-ray photoelectron spectroscopic (XPS) was used to elucidate in detail the intercalation of PFOS into DNA and the formation of hydrogen bond between PFOS and DNA base. Electrochemical quartz crystal microbalance (EQCM) proved the formation of adducts of DNA and PFOS. Moreover, electrochemical impedance spectroscopy (EIS) indicates that the PFOS influence DNA structure and attenuate DNA charge transport. These results demonstrate that PFOS intercalated into DNA do induce DNA base damage.

[Self-assembled gold nanoparticles modified electrode for electrochemical detection nitrite].

A modified sensor was fabricated by N-[3-(trimethoxysilyl) propyl]-ethylene diamine (TSPED) and colloidal gold particles (AuNPs) on glass carbon electrode (GCE). Atomic force microscopy (AFM) demonstrated that the colloidal gold particles were self-assembled onto the amine groups of the sol-gel. Due to the excellent electrocatalytic activity of gold nanoparticles toward the oxidation of nitrite and the interaction between the protonated TSPED film and the negatively-charged nitrite, the operating potential for nitrite oxidation was shifted about 140 mV to negative side, compared to bare GCE. The differential pulse voltammetry and the differential pulse amperometry were employed in the process of electrochemical measurements. Under the optimal conditions, a highly linear response to nitrite in the concentration range of 5.0 x 10(-7)-1.0 x 10(-3) mol x L- was observed, with a detection limit of 2.0 x 10(-7) mol x L(-1) (S/N = 3). The real water samples were investigated and the results were in good agreement with those obtained by standard spectrophotometric method. This method proposed by this paper possesses high sensitivity and good reproducibility.

[Preparation and characterization of parathion sensor based on molecularly imprinted polymer].

A novel electrochemical sensor for the detection of parathion based on molecularly imprinted polymer of self-assembled o-aminothiophenol onto gold electrode was constructed. The polymerization solution was prepared from a 10 mmol/L parathion, 5 mmol/L tetra-n-butylammonium perchlorate, 30 mmol/L o-aminothiophenol solution of dichloromethane. Electropolymerization was carried out over 30 cycles between -0.3 V and 1.4 V. The template molecules were removed from the modified electrode surface by washing with 0.5 mol/L hydrochloric acid. Cyclic voltammetry was employed in the process of electrochemical measurements. The experimental results show that the optimum acidity of background solution is pH 6.8 and the optimum incubation time is 10 min. A highly linear response to parathion in the concentration range of 1.0 x 10(-4)--5.0 x 10(-7) mol/L is observed, with a detection limit of 2.0 x 10(-7) mol/L estimated at a signal-to-noise ratio of 3. The sensor has been applied to the analysis of parathion in real sample with recovery rates ranging from 98.0% to 104%. Parathion imprinted and nonimprinted polymer films were exposed to a series of closely related compounds, e.g. methyl-parathion, paraoxon, phoxim, omethoate, nitrobenzene and o-, m-, p- nitrophenol, and the sensor exhibited good selectivity and sensitivity to parathion.

Determination of nitrite using sensors based on nickel phthalocyanine polymer modified electrodes.

An amperometric nitrite sensor based on a polymeric nikel tetraaminothphalocyanine (p-NiTAPc) film coated glassy carbon (GC) electrode was developed. The mechanism of catalysis on the surface of the electrode was discussed. The sensor exhibited fast respond towards nitrite with a detection limit of 1x10(-7)M and a linear concentration range of 5x10(-7) to 8x10(-3)M. The possible interference from several common ions was tested. The proposed method was successfully applied in the detection of nitrite in real samples.