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

Inkjet-printed silver nanoparticle paper detects airborne species from crystalline explosives and their ultratrace residues in open environment

An electronic nose can detect highly volatile chemicals in foods, drugs, and environments, but it is still very much a challenge to detect the odors from crystalline compounds (e.g., solid explosives) with a low vapor pressure using the present chemosensing techniques in such way as a dog's olfactory system can do. Here, we inkjet printed silver nanoparticles (AgNPs) on cellulose paper and established a Raman spectroscopic approach to detect the odors of explosive trinitrotoluene (TNT) crystals and residues in the open environment. The layer-by-layer printed AgNP paper was modified with p-aminobenzenethiol (PABT) for efficiently collecting airborne TNT via a charge-transfer reaction and for greatly enhancing the Raman scattering of PABT by multiple spectral resonances. Thus, a Raman switch concept by the Raman readout of PABT for the detection of TNT was proposed. The AgNPs paper at different sites exhibited a highly uniform sensitivity to TNT due to the layer-by-layer printing, and the sensitive limit could reach 1.6 × 10(-17) g/cm(2) TNT. Experimentally, upon applying a beam of near-infrared low-energy laser to slightly heat (but not destruct) TNT crystals, the resulting airborne TNT in the open environment was probed at the height of 5 cm, in which the concentration of airborne species was lower than 10 ppt by a theoretical analysis. Similarly, the odors from 1.4 ppm TNT in soil and 7.2, 2.9, and 5.7 ng/cm(2) TNT on clothing, leather, and envelope, respectively, were also quickly sensed for 2 s without destoying these inspected objects.

ZnO–Ag hybrids for ultrasensitive detection of trinitrotoluene by surface-enhanced Raman spectroscopy

Low-cost SERS sensors were fabricated by 4-ATP-functionalized ZnO–Ag hybrid substrates for TNT detection with high sensitivity, selectivity and reproducibility.

Uniform core–shell molecularly imprinted polymers: a correlation study between shell thickness and binding capacity

A model of core–shell MIPs was constructed to evaluate the correlation between shell thickness and binding capacity.

Selective visual detection of trace trinitrotoluene residues based on dual-color fluorescence of graphene oxide–nanocrystals hybrid probe

The dual-color fluorescence nanohybrid probe comprising blue emissive fluorescent graphene oxide and red emissive nanocrystals has been developed for the visual detection of TNT residues in solution and on various surfaces.

APTS and rGO co-functionalized pyrenated fluorescent nanonets for representative vapor phase nitroaromatic explosive detection

For the first time, flexible PVP/pyrene/APTS/rGO fluorescent nanonets were designed and synthesized via a one-step electrospinning method to detect representative subsaturated nitroaromatic explosive vapor. The functional fluorescent nanonets, which were highly stable in air, showed an 81% quenching efficiency towards TNT vapor (∼10 ppb) with an exposure time of 540 s at room temperature. The nice performance of the nanonets was ascribed to the synergistic effects induced by the specific adsorption properties of APTS, the fast charge transfer properties and the effective π-π interaction with pyrene and TNT of rGO. Compared to the analogues of TNT, the PVP/pyrene/APTS/rGO nanonets showed notable selectivity towards TNT and DNT vapors. The explored functionalization method opens up brand new insight into sensitive and selective detection of vapor phase nitroaromatic explosives.

Automatic reactor for solid-phase synthesis of molecularly imprinted polymeric nanoparticles (MIP NPs) in water

We report the development of an automated chemical reactor for solid-phase synthesis of MIP NPs in water. Operational parameters are under computer control, requiring minimal operator intervention. In this study, "ready for use" MIP NPs with sub-nanomolar affinity are prepared against pepsin A, trypsin and α-amylase in only 4 hours.

Novel hybrid structure silica/CdTe/molecularly imprinted polymer: synthesis, specific recognition, and quantitative fluorescence detection of bovine hemoglobin

This work presented a novel strategy for the synthesis of the hybrid structure silica/CdTe/molecularly imprinted polymer (Si-NP/CdTe/MIP) to recognize and detect the template bovine hemoglobin (BHb). First, amino-functionalized silica nanoparticles (Si-NP) and carboxyl-terminated CdTe quantum dots (QDs) were assembled into composite nanoparticles (Si-NP/CdTe) using the EDC (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride) chemistry. Next, Si-NP/CdTe/MIP was synthesized by anchoring molecularly imprinted polymer (MIP) layer on the surface of Si-NP/CdTe through the sol-gel technique and surface imprinting technique. The hybrid structure possessed the selectivity of molecular imprinting technique and the sensitivity of CdTe QDs as well as well-defined morphology. The binding experiment and fluorescence method demonstrated its special recognition performance toward the template BHb. Under the optimized conditions, the fluorescence intensity of the Si-NP/CdTe/MIP decreased linearly with the increase of BHb in the concentration range 0.02-2.1 μM, and the detection limit was 9.4 nM. Moreover, the reusability and reproducibility and the successful applications in practical samples indicated the synthesis of Si-NP/CdTe/MIP provided an alternative solution for special recognition and determination of protein from real samples.

Upconversion luminescence nanosensor for TNT selective and label-free quantification in the mixture of nitroaromatic explosives

This paper reports a rapid, sensitive, and selective nanosensor for the detection of 2,4,6-trinitrotoluene (TNT) in the mixture aqueous solution of nitroaromatics independent of immunoassay or molecularly imprinted technology and complicated instruments. Despite many strategies including immunoassay and molecularly imprinted technologies been successfully developed for the detection of TNT, it is not easy to differentiate TNT from 2,4,6-trinitrophenol (TNP) due to their very similar chemical structures and properties. In this work, the amine functionalized NaYF4:Yb(3+)/Er(3+) upconversion luminescence nanoparticles (UCNPs) whose excitation (980 nm) and emission (543 nm) wavelength were far from the absorbance bands of other usual interference nitroaromatics including 2,4-dinitrotoluene (DNT), nitrobenzene (NB), and especially TNP, were utilized as the luminescent nanosensors for TNT luminescence detection. To make these UCNPs highly water stable and render the charge transfer from UCNPs to TNT easier, amino groups were introduced onto the surface of the UCNPs by coating a polymer layer of ethylene glycol dimethacrylate (EGDMA) hybridized with 3-aminopropyltriethoxysilane (APTS). After binding with TNT through amino groups on the UCNPs, the naked eye visible green upconversion luminescence of the UCNPs was dramatically quenched and thus a sensitive UC luminescence nanosensor was developed for TNT detection. However, other nitroaromatics including TNP, DNT, and NB have no influence on the green UC luminescence and thus no influence on the TNT detection. The luminescence intensity is negatively proportional to the concentration of TNT in the range of 0.01-9.0 µg/mL with the 3σ limit of detection (LOD) of 9.7 ng/mL. The present studies provide a novel and facile strategy to fabricate the upconversion luminescence sensors with highly selective recognition ability in aqueous media and are desirable for label free analysis of TNT in mixed solution independent of immunoassay and molecularly imprinted technology and complicated instruments.

Surface plasmon resonance sensor based on magnetic molecularly imprinted polymers amplification for pesticide recognition

We reported here a method to enhance detection sensitivity in surface plasmon resonance (SPR) spectroscopy integrated with a surface molecular imprinting recognition system and employing magnetic molecular imprinting polymer nanoparticles for amplifying SPR response. The proposed magnetic molecular imprinting polymer was designed by self-polymerization of dopamine on the Fe3O4 NPs surface in weak base aqueous solution in the presence of template chlorpyrifos (CPF). The imprinted Fe3O4@polydopamine nanoparticles (Fe3O4@PDA NPs) were characterized by Fourier transform infrared spectroscopy, UV-vis absorption spectroscopy, and transmission electron microscopy. The biosensor showed a good linear relationship between the SPR angle shift and the chlorpyrifos concentration over a range from 0.001 to 10 μM with a detection limit of 0.76 nM. A significant increase in sensitivity was therefore afforded through the use of imprinted Fe3O4@PDA NPs as an amplifier, and meanwhile, the imprinted Fe3O4@PDA NPs had an excellent recognition capacity to chlorpyrifos over other pesticides. The excellent sensitivity and selectivity and high stability of the designed biosensor make this magnetic imprinted Fe3O4@PDA NP an attractive recognition element for various SPR sensors for detecting pesticide residuals and other environmentally deleterious chemicals.

Nanostructure-based optoelectronic sensing of vapor phase explosives--a promising but challenging method

Optoelectronic sensing of gas phase hazardous chemicals is a newly explored field, which shows great advantages towards low concentration sensing when compared to normal gas sensing in the dark. Here, based on the recent progress on nanostructured vapor phase explosive gas sensors operated in dark conditions, the attractiveness of developing optoelectronic sensors for vapor phase explosive detection was highlighted. Furthermore, we try to propose some new insights to enhance optoelectronic sensing of vapor phase explosives. We suggest employing photocatalysis principles to enhance the sensitivity and employing a molecular imprinting technique (MIT) to enhance the selectivity.

Fe3O4/Au nanoparticles/lignin modified microspheres as effectual surface enhanced Raman scattering (SERS) substrates for highly selective and sensitive detection of 2,4,6-trinitrotoluene (TNT)

A new lignin modified hybrid microsphere, comprising poly(styrene-co-acrylic acid) core and magnetite (Fe3O4)/Au nanoparticle (NP) shell, was proposed here for the selective and highly sensitive detection and removal of 2,4,6-trinitrotoluene (TNT) explosives based on surface enhanced Raman scattering (SERS) and electrochemical detection methods. The presence of lignin and the highly packed layer of Fe3O4/AuNPs as a magnetic collector and metal enhancer for SERS signals allowed for the detection of TNT below 1 pM.

Highly selective detection of polycyclic aromatic hydrocarbons using multifunctional magnetic-luminescent molecularly imprinted polymers

A facile method is presented for the selective luminescence detection of trace polycyclic aromatic hydrocarbons (PAHs) based on a combination of the specific recognition of molecularly imprinted polymers (MIPs) and magnetic separation (MS). Multifunctional magnetic-luminescent MIP nanocomposites were fabricated via a one-pot emulsion strategy using polystyrene-co-methacrylic acid copolymer, hydrophobic Fe3O4 nanoparticles and luminescent LaVO4:Eu(3+) nanoparticles as building blocks with a phenanthrene template. The resulting nanocomposites can be employed in a simple method for the luminescence detection of phenanthrene. Furthermore, magnetic separation of the nanocomposites from the target mixture prior to luminescence detection of phenanthrene affords significantly enhanced selectivity and sensitivity, with a 3σ limit of detection (LOD) as low as 3.64 ng/mL. Milk samples spiked with phenanthrene (5.0 μg/mL) were assayed via this method and recoveries ranging from 97.11 to 101.9% were obtained, showing that our strategy is potentially applicable for the preconcentration, recovering, and monitoring of trace PAHs in complex mixtures.

Surface molecular-imprinting engineering of novel cellulose nanofibril/conjugated polymer film sensors towards highly selective recognition and responsiveness of nitroaromatic vapors

We designed and synthesized two conjugated polymer-grafted cellulose nanofibril film sensors via surface molecular-imprinting. These two surface TNT- or DNT-imprinted film sensors exhibit highly selective recognition and fast response towards target explosive vapor.

Molecularly imprinted SPE coupled with HPLC for the selective separation and enrichment of alkyl imidazolium ionic liquids in environmental water samples

A novel 1-butyl-3-methylimidazolium chloride ionic liquid surface imprinted solid-phase sorbent was synthesized. The as-prepared material was characterized by SEM, Brunauer-Emmett-Teller surface area analysis and Fourier Transform IR measurements. Then its adsorption properties for alkyl imidazolium ionic liquids, including adsorption capacities, adsorption kinetics, and properties of selective separation and enrichment were studied in detail. It was shown that the ionic liquid surface imprinted polymer exhibited high selective recognition characteristics for the imidazolium chloride ionic liquids with short alkyl chains (C(n)mimCl, n = 2, 4, 6, 8) and the adsorption equilibrium was achieved within 25 min. Various parameters were optimized for the 1-butyl-3-methylimidazolium chloride ionic liquid surface imprinted polymer SPE column, such as flow rate, eluent solvent, selectivity, and reusability of the column. Then, the SPE column coupled with HPLC was used for the determination of alkyl imidazolium ionic liquids. Experimental results showed that the existence of their structural analogs and common concomitants in environmental matrices did not affect the enrichment of 1-butyl-3-methyl imidazolium chloride ionic liquid. The average recoveries of 1-butyl-3-methylimidazolium chloride ionic liquid in spiked water samples were in the range of 92.0-102.0% with the RSD lower than 5.8%.

Bovine serum albumin coated CuInS2 quantum dots as a near-infrared fluorescence probe for 2,4,6-trinitrophenol detection

In this paper, a novel near-infrared fluorescence probe for the determination of 2,4,6-trinitrophenol (TNP) was developed based on bovine serum albumin (BSA) coated CuInS2 quantum dot (QD). Water-soluble CuInS2 QDs were directly synthesized in aqueous solution with mercaptopropionic acid (MPA) as stablizers, and it was coated by BSA via an amide link interacting with carboxyl of the MPA-capped CuInS2 QDs. The obtained BSA coated CuInS2 QDs (BSA-CuInS2 QDs) can bind TNP in water via the acid-base pairing interaction between electron-rich amino groups of BSA and electron-deficient nitroaromatic rings, and leading the fluorescence quenching of BSA-CuInS2 QDs. The quenched fluorescence intensity of BSA-CuInS2 QDs was proportional to the concentration of TNP in the concentration ranges from 50 nmol/L to 3.0 μmol/L. The detection limit (LOD) for TNP was 28 nmol/L. The developed fluorescence probe showed a excellent resistant to interference of metal ions such as K(+), Na(+), Zn(2+), Cu(2+), Hg(2+), and Pb(2+). The developed biosensor was applied to the determination of TNP in spiked water samples with satisfactory results.

Luminescent core-shell imprinted nanoparticles engineered for targeted Förster resonance energy transfer-based sensing

Red-luminescent 200 nm silica nanoparticles have been designed and prepared as a versatile platform for developing FRET (Förster resonance energy transfer) biomimetic assays. Ru(phen)₃²⁺ dye molecules embedded off-center in the silica core provide the long-lived donor emission, and a near-infrared labeled analyte serves as fluorescent acceptor (the measured R₀ of this D-A pair is 4.3 nm). A thin surface-grafted molecularly imprinted polymer (MIP) shell intervenes as selective enrofloxacin-binding element. These nanoparticles have been tested for photochemical detection of enrofloxacin by using a competitive scheme that can be readily performed in MeCN-HEPES (pH 7.5) 7:3 (v/v) mixtures and allows for the antibiotic detection in the μM range (LOD = 2 μM) without optimization of the assay. Given the well-known difficulties of coupling the target-binding-to-MIP and the transducing events, the novel photochemical approach tuned up here will be valuable in future developments of MIP-based assays and optosensors that capitalize also on the advantages of nanomaterials for (bio)analysis.