A surface functional monomer-directing strategy for highly dense imprinting of TNT at surface of silica nanoparticles

Electropolymerized molecular imprinting on gold nanoparticle-carbon nanotube modified electrode for electrochemical detection of triazophos

An electrochemical sensor for pesticide triazophos (TAP) was prepared by deposition of gold nanoparticles (AuNPs) on carbon nanotubes (CNTs) modified glassy carbon (GC) electrode surface using a potentiostatic method, followed by electropolymerizing of o-hydroxyphenol at the AuNP/CNT/GC electrode surface in the presence of template triazophos via cyclic voltammetry. The electrochemical response of triazophos at the TAP-imprinted polyhydroxyphenol (PHP) modified AuNP/CNT/GC (PHP/AuNP/CNT/GC) electrode was investigated by cyclic voltammetry. The cyclic voltammetric response of triazophos at the TAP-imprinted PHP/AuNP/CNT/GC electrode was significantly higher than that at bare GC, CNT/GC, AuNP/CNT/GC, imprinted PHP/CNT/GC and non-imprinted PHP/AuNP/CNT/GC electrodes. The results indicated that the TAP-imprinted PHP/AuNP/CNT/GC electrode can effectively improve the reductive properties of triazophos and eliminate interferences of other pesticides. In addition, the AuNPs can strikingly amplify the electrochemical response of triazophos and improve the sensitivity to triazophos. Finally, the electrochemical sensor was successfully applied to determination of triazophos in vegetable samples with satisfactory results.

Development of a novel deltamethrin sensor based on molecularly imprinted silica nanospheres embedded CdTe quantum dots

A novel procedure for the determination of deltmethrin (DM) is reported. The water-soluble CdTe quantum dots (QDs) and highly fluorescent silica molecularly imprinted nanospheres embedded CdTe QDs (CdTe-SiO2-MIPs) were prepared and characterized by fluorescence spectroscopy, UV-vis spectroscopy, TEM and IR. The fluorescence nanosensor based CdTe-SiO2-MIPs is developed. The possible quenching mechanism is discussed by DM. Under optimal conditions, the relative fluorescence intensity of CdTe-SiO2-MIPs decreased with increasing DM by a Stern-Volmer type equation in the concentration range of 0.5-35.0 μg mL(-1), the corresponding detection limit is 0.16 μg mL(-1). The developed sensor based on CdTe-SiO2-MIPs was applied to determine DM in fruit and vegetable samples.

Electrochemical sensor for dopamine based on a novel graphene-molecular imprinted polymers composite recognition element

A novel composite of graphene sheets/Congo red-molecular imprinted polymers (GSCR-MIPs) was synthesized through free radical polymerization (FRP) and applied as a molecular recognition element to construct dopamine (DA) electrochemical sensor. The template molecules (DA) were firstly absorbed at the GSCR surface due to their excellent affinity, and subsequently, selective copolymerization of methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) was further achieved at the GSCR surface. Potential scanning was presented to extract DA molecules from the imprinted polymers film, and as a result, DA could be rapidly and completely removed by this way. With regard to the traditional MIPs, the GSCR-MIPs not only possessed a faster desorption and adsorption dynamics, but also exhibited a higher selectivity and binding capacity toward DA molecule. As a consequence, an electrochemical sensor for highly sensitive and selective detection of DA was successfully constructed as demonstration based on the synthesized GSCR-MIPs nanocomposites. Under experimental conditions, selective detection of DA in a linear concentration range of 1.0 × 10(-7)-8.3 × 10(-4)M was obtained, which revealed a lower limit of detection and wider linear response compared to some previously reported DA electrochemical MIPs sensors. The new DA electrochemical sensor based on GSCR-MIPs composites also exhibited excellent repeatability, which expressed as relative standard deviation (RSD) was about 2.50% for 30 repeated analyses of 20 μM DA.

Ultrasensitive determination of 1,4-dihydroxybenzene based on fluorescence resonance energy quenching of luminescent quantum dots modified on surface of silica nanoparticles

An ultrasensitive solid-phase fluorescence resonance energy quenching (FREQ) method for determination of 1,4-dihydroxybenzene (DHB) using mercaptosuccinic acid (MSA)-capped CdTe quantum dots (QDs) immobilized on silica nanoparticles (NPs) as donors was developed. In the method, silica NPs were first modified with 3-aminopropyltriethoxysilane (APTS). Then, MSA-capped CdTe QDs were immobilized on the surface of the APTS-modified silica NPs. Finally, DHB in the solution was attached to the empty sites on the surface of silica NPs with QDs through electrostatic interaction. The fluorescence emission of the QDs was quenched by the proximal DHB molecules on the silica NPs. The quenching efficiency of the solid-phase FREQ method was 200-times higher than that of the solution-phase FREQ method. Using the ultrasensitive solid-phase FREQ method, DHB as low as 2.4×10(-12) mol/L could be detected. The method was applied to quantify trace DHB in water samples.

Synthesis of surface imprinted nanospheres for selective removal of uranium from simulants of Sambhar salt lake and ground water

Imprinted polymer nanospheres for uranium were prepared by complexing uranyl ion on to quinoline-8-ol functionalized 3-aminopropyltrimethoxysilane modified silica nanoparticles followed by surface imprinting with 4-VP (4-vinyl pyridine), HEMA (2-hydroxy ethyl methacrylate) and EGDMA (ethylene glycol dimethacrylate) as the functional monomers and cross linking agent respectively with AIBN (2,2'-azo-bis-isobutyronitrile) as initiator and 2-methoxyethanol as the porogen. Non-imprinted polymer material was also prepared under similar conditions omitting uranyl ion. The above materials were used for solid phase extraction of uranium. Recent realization that its chemical toxicity is dominant than radiation hazards makes decontamination a relevant topic for environmental point of view, particularly in the light of projected global thrust for uranium fuel based atomic power plants. The material offers high retention capacity of 97.1 μmol g(-1) for 10 mg L(-1) of uranium that does not require tedious grinding and sieving steps, is water compatible and works in the pH range of 5-7, making it ideal for possible use in decontamination of polluted natural water samples or front end effluents of nuclear power reactors.

3-Aminopropyltriethoxysilane-functionalized manganese doped ZnS quantum dots for room-temperature phosphorescence sensing ultratrace 2,4,6-trinitrotoluene in aqueous solution

New strategies for silica coating of inorganic nanoparticles became a research hotspot for enhancing the mechanical stability of colloidal particles and protecting colloidal particles against oxidation and agglomeration, and so on. In this paper, 3-aminopropyltriethoxysilane (APTES)-functionalized Mn doped (AF MnD) ZnS QDs was prepared to be firsyly through the use of silane coupling agents to form an active layer of silica, then sol-gel reaction of TEOS co-deposited with APTES on the surface of resultant active layer of silica. The emitted long lifetime room-temperature phosphorescence (RTP) of the resultant nanomaterials allows an appropriate delay time so that any fluorescent emission and scattering light can be easily avoided. The APTES anchored on the layer of silica can bind 2,4,6-trinitrotoluene (TNT) species to form TNT anion through acid-base pairing interaction, the TNT anion species may increase the charge-transfer pathways from the nanocrystals to nitroaromatic analytes, therefore further enhance the quenching efficiency of RTP. Moreover, APTES as capped reagents can enlarge the spectral sensitivity and enhance RTP response of nanocrystals to the electron-deficient nitroaromatic and nitrophenol species. Meanwhile, AF MnD ZnS QDs also exhibited a highly selective response toward TNT analyte through significant color change and quenching of (4)T(1) to (6)A(1) transition emission. This AF MnD ZnS QDs based sensor showed a very good linearity in the range of 0.05-1.8μM with detection limit down to 50 nM (quenching percentage of phosphorescence intensity of 8%) and RSD of 3.5% (n=5). The reported QDs-based chemosensors here open up a promising prospect for the sensitive and convenient sensing of TNT explosive.

Recent advances in molecular imprinting technology: current status, challenges and highlighted applications

Molecular imprinting technology (MIT) concerns formation of selective sites in a polymer matrix with the memory of a template. Recently, molecularly imprinted polymers (MIPs) have aroused extensive attention and been widely applied in many fields, such as solid-phase extraction, chemical sensors and artificial antibodies owing to their desired selectivity, physical robustness, thermal stability, as well as low cost and easy preparation. With the rapid development of MIT as a research hotspot, it faces a number of challenges, involving biological macromolecule imprinting, heterogeneous binding sites, template leakage, incompatibility with aqueous media, low binding capacity and slow mass transfer, which restricts its applications in various aspects. This critical review briefly reviews the current status of MIT, particular emphasis on significant progresses of novel imprinting methods, some challenges and effective strategies for MIT, and highlighted applications of MIPs. Finally, some significant attempts in further developing MIT are also proposed (236 references).

Voltammetric detection of nitroaromatic compounds using carbon-nanomaterials-based electrodes

The morphology of glassy carbon surfaces was investigated by the atomic force microscope (AFM) method. Multi-wall carbon nanotubes (MWCNTs) were purified and investigated with a scanning electron microscope (SEM) and a transmission electron microscope (TEM). An electrochemical technique based on the glassy carbon electrode (GCE) or MWCNT-modified GCEs was used for the detection of nitroaromatic compounds (NACs), namely 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitrobenzene (TNB), 2,4-dinitrotoluene (2,4-DNT), and 1,3-dinitrobenzene (1,3-DNB). MWCNT-modified GCEs were more sensitive than GCEs to TNB, 2,4-DNT, and 1,3-DNB, with the detection limit down to ppb level, whereas the modified GCEs showed lower sensitivity to TNT. In varying degrees, the accumulation of nitro compounds can be promoted by MWCNT-modified GCEs in the detection process, a property which can be attributed to the large surface area and graphene-sheet structure of MWCNTs.