Junqing Fu

Sol–gel synthesis and photoluminescent properties of LaPO4:A (A = Eu3+, Ce3+, Tb3+) nanocrystalline thin films

Rare-earth ion (Eu3+, Tb3+, Ce3+)-doped LaPO4 nanocrystalline thin films and their patterning were fabricated by a Pechini sol–gel process combined with soft lithography on silicon and silica glass substrates. X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), atomic force microscopy (AFM), scanning electron microcopy (SEM), optical microscopy, absorption and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting films. The results of XRD indicate that the films begin to crystallize at 700 °C and the crystallinity increases with increasing annealing temperature. The morphology of the thin film depends on the annealing temperature and the number of coating layers. The 1000 °C annealed single layer film is transparent to the naked eye, uniform and crack-free with a thickness of about 200 nm and an average grain size of 100 nm. Patterned thin films with different strip widths (5–50 µm) were obtained by micromolding in capillaries (soft lithography). The doped rare earth ions show their characteristic emission in the nanocrystalline LaPO4 films, i.e., Eu3+5D0–7FJ (J = 1, 2, 3, 4), Tb3+5D3,4–7FJ (J = 6, 5, 4, 3, 2) and Ce3+ 5d–4f transition emissions, respectively. Both the lifetimes and the PL intensities of Eu3+ and Tb3+ increase with increasing annealing temperature, and the optimum concentrations for them were determined to be 5 mol% and 16 mol% of La3+ in LaPO4 thin films, respectively. An energy transfer phenomenon from Ce3+ to Tb3+ has been observed in LaPO4 nanocrystalline thin films, and the energy transfer efficiency depends on the doping concentration of Tb3+ if the concentration of Ce3+ is fixed.

Preparation, patterning and luminescent properties of nanocrystalline Gd2O3 : A (A = Eu3+, Dy3+, Sm3+, Er3+) phosphor films via Pechini sol-gel soft lithography

Nanocrystalline Gd2O3:A (A = Eu3+, Dy3+, Sm3+, Er3+) phosphor films and their patterning were fabricated by a Pechini sol-gel process combined with a soft lithography. X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and optical microscopy, UV/vis transmission and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 500 degreesC and that the crystallinity increased with the elevation of annealing temperatures. Uniform and crack free non-patterned phosphor films were obtained by optimizing the composition of the coating sol, which mainly consisted of grains with an average size of 70 nm and a thickness of 550 nm. Using micro-molding in capillaries technique, we obtained homogeneous and defects-free patterned gel and crystalline phosphor films with different stripe widths (5, 10, 20 and 50 mum). Significant shrinkage (50%) was observed in the patterned films during the heat treatment process. The doped rare earth ions (A) showed their characteristic emission in crystalline Gd2O3 phosphor films due to an efficient energy transfer from Gd2O3 host to them. Both the lifetimes and PL intensity of the rare earth ions increased with increasing the annealing temperature from 500 to 900 degreesC, and the optimum concentrations for Eu3+, Dy3+, sm(3+), Er3+ were determined to be 5, 0.25, 1 and 1.5 mol% of Gd3+ in Gd2O3 films, respectively.

Current status and challenges of ion imprinting

Ion imprinting technology (IIT) aims to recognize ions while retaining the unique virtues of molecular imprinting technology (MIT), namely structure predictability, recognition specificity and application universality. Owing to special coordination or electrostatic interactions, ion imprinted polymers (IIPs) are generally compatible with aqueous media and have advantages over most molecularly imprinted polymers (MIPs). IIPs can achieve effective identification of water-soluble ions, especially heavy metals and radioactive elements that cause increasing concerns. The purpose of this review is to summarize recent advances of ion imprinting, focusing on the current status and challenges in fundamentals and applications that involve almost all types of ions and ion-related molecular imprinting. In addition, various smart strategies are highlighted, such as surface imprinting, stimuli-responsive imprinting, dual/multiple components imprinting, click chemistry, and microwave-assisted heating. In this review, the elemental periodic table is first utilized as a template to introduce ion classification standards for various IIPs, including main groups, transition elements, actinides, rare earths, metalloids, anion imprinting and secondary imprinting. Finally, the challenges and possible solution strategies plus future trends are also proposed (302 references).

A molecular imprinting-based turn-on Ratiometric fluorescence sensor for highly selective and sensitive detection of 2,4-dichlorophenoxyacetic acid (2,4-D)

A novel molecular imprinting-based turn-on ratiometric fluorescence sensor was constructed via a facile sol-gel polymerization for detection of 2,4-dichlorophenoxyacetic acid (2,4-D) on the basis of photoinduced electron transfer (PET) by using nitrobenzoxadiazole (NBD) as detection signal source and quantum dots (QDs) as reference signal source. With the presence and increase of 2,4-D, the amine groups on the surface of QDs@SiO2 could bind with 2,4-D and thereby the NBD fluorescence intensities could be significantly enhanced since the PET process was inhibited, while the QDs maintained constant intensities. Accordingly, the ratio of the dual-emission intensities of green NBD and red QDs could be utilized for turn-on fluorescent detection of 2,4-D, along with continuous color changes from orange-red to green readily observed by the naked eye. The as-prepared fluorescence sensor obtained high sensitivity with a low detection limit of 0.14μM within 5min, and distinguished recognition selectivity for 2,4-D over its analogs. Moreover, the sensor was successfully applied to determine 2,4-D in real water samples, and high recoveries at three spiking levels of 2,4-D ranged from 95.0% to 110.1% with precisions below 4.5%. The simple, rapid and reliable visual sensing strategy would not only provide potential applications for high selective ultratrace analysis of complicated matrices, but also greatly enrich the research connotations of molecularly imprinted sensors.

Patterning and optical properties rhodamine B-doped organic-inorganic silica films fabricated by sol-gel soft lithography

Abstract Rhodamine B (RB)-doped organic–inorganic silica films and their patterning were fabricated by a sol–gel process combined with a soft lithography. The resulted film samples were characterized by atomic force microscope (AFM), optical microscope and UV/Vis absorption and photoluminescence excitation and emission spectra. The effects of the concentration of the RB dye and heat treatment temperature on the optical properties of the hybrid silica films have been studied. Four kinds of patterning structures with film line widths of 5, 10, 20 and 50 μm have been obtained by micromolding in capillaries by a soft lithography technique. The RB-doped hybrid silica films present a red color, with an excitation and emission bands around 564 and 585 nm, respectively. With increasing the RB concentration, the emission intensity of the RB-doped hybrid silica films increases and the emission maximum presents a red shift. The emission intensity of the films decreases with increasing the heat treatment temperatures.

Fluorescent and magnetic dual-responsive coreshell imprinting microspheres strategy for recognition and detection of phycocyanin

Molecular imprinting as a versatile technology is emerging for diverse species in various fields; however protein imprinting faces several problems related to the size, structural complexity, conformational flexibility, and compatibility with solvents. Herein, by using phycocyanin as a model, with physiological significance and fluorescence characteristics, we developed a facile and highly efficient approach to obtain fluorescent and magnetic dual-responsive coreshell imprinting microspheres. Twostage miniemulsion polymerization was employed, based on surface immobilization of phycocyanin with aminolysis and aldehyde modification on superparamagnetic support particles. The dual-responsive imprinting microspheres exhibited high adsorption capacity of 10.53 mg g−1, excellent binding selectivity toward phycocyanin with a high imprinting factor of 2.41, and good reproducibility with standard error within 10%. Furthermore, fast simple magnetic separation and sensitive fluorescent detection in a wide pH range was offered for phycocyanin, showing a good linearity within 0.01–1.0 mg L−1 (R2 = 0.9970) and a favorable detectability up to 1.5 ng mL−1. Consequently, the imprinting microspheres were successfully applied as sorbents for selective isolation of phycocyanin from protein mixtures and special imaging recognition. Taking advantages of dual-responsive polymers and surface imprinting, the developed strategy provides great application potentials for convenient, rapid targeting identification/enrichment and separation of proteins and thereby contributing to targeting drug delivery and protein research.

Preparation, patterning and luminescent properties of oxyapatite La9.33(SiO6)4O2:A(A = Eu3+, Tb3+, Ce3+) phosphor films by sol–gel soft lithography

Silicate oxyapatite La-9.33 (SiO6)(4)O-2:A (A = Eu3+, Tb3+ and/or Ce3+) phosphor films and their patterning were fabricated by a sol-gel process combined with soft lithography. X-ray diffraction (XRD), Fourier transform infrared spectroscopy, atomic force microscopy, optical microscopy and photoluminescence spectra, as well as lifetimes, were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 800degreesC and the crystallinity increased with the increase in annealing temperatures. Transparent nonpatterned phosphor films were uniform and crack-free, which mainly consisted of rodlike grains with a size between 150 and 210 nm. Patterned thin films with different bandwidths (20, 50 mum) were obtained by the micromoulding in capillaries technique. The doped rare earth ions (Eu3+, Tb3+ and Ce3+) showed their characteristic emission in crystalline La-9.33(SiO6)(4)O-2 phosphor films, i.e. Eu3+ D-5(0)-F-7(J) (J = 0, 1, 2, 3, 4), Tb3+ D-5(3,4)-F-7(J) (J = 3, 4, 5, 6) and Ce3+ 5d (D-2)-4f (F-2(2/5), F-2(2/7)) emissions, respectively. Both the lifetimes and PL intensity of the Eu3+, Tb3+ ions increased with increasing annealing temperature from 800 to 1100 degreesC, and the optimum concentrations for Eu3+, Tb3+ were determined to be 9 and 7 mol% of La3+ in La-9.33(SiO6)(4)O-2 films, respectively. An energy transfer from Ce3+ to Tb3+ was observed in the La-9.33(SiO6)(4)O-2:Ce, Tb phosphor films, and the energy transfer efficiency was estimated as a function of Tb3+ concentration.

Synthesis of multi-ion imprinted polymers based on dithizone chelation for simultaneous removal of Hg2+, Cd2+, Ni2+ and Cu2+ from aqueous solutions

Simultaneous analysis and removal of various heavy metal ions has received increasing concerns because they are usually co-existent with different toxicological effects. Ion imprinted polymers (IIPs) can effectively identify water-soluble ions especially heavy metal ions, however, multi-ion imprinting is rarely performed owing to possible cross-reactivity and matrix interferences. In this work, a novel and generally applicable IIPs strategy was proposed for simultaneous preconcentration and removal of four heavy metal ions based on dithizone chelation. Multi-ion imprinted polymers (MIIPs) embedded in a sol–gel matrix were prepared by using Hg2+, Cd2+, Ni2+ and Cu2+ as templates and 3-aminopropyltriethoxysilane as a functional monomer, and the possible synergy mechanism was explored between dithizone coordination chemistry and multi-ion imprinting. The structures, morphologies and thermostability of MIIPs were well characterized by Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) and thermogravimetry analysis (TGA). The resultant MIIPs showed high binding capacity and fast dynamics, and the adsorption processes obeyed Langmuir isotherm and pseudo-second-order dynamic models. The MIIPs displayed excellent selectivity toward the four target ions particularly over Pb2+, Zn2+ and Co2+ with selective coefficients of 6.8–16.9, as well as high anti-interference ability when confronted with common co-present various ions. Moreover, a high preparation yield of 41% and good reusability over 90% desorption efficiency were obtained. Consequently, the MIIPs were used as solid-phase extraction sorbents for preconcentration of trace Hg2+, Cd2+, Ni2+ and Cu2+, presenting high detectability up to 6.0–22.5 ng L−1 and satisfactory recoveries ranging from 94.7–110.2% in seawater samples. The developed MIIPs-based method proved to be a practically feasible method in heavy metal removal and water pretreatment.

Switchable zipper-like thermoresponsive molecularly imprinted polymers for selective recognition and extraction of estradiol

Zipper-like thermoresponsive molecularly imprinted polymers (MIPs) were prepared based on interpolymer complexation via the synergy of dual functional monomers of acrylamide (AAm) and 2-acrylamide-2-methyl propanesulfonic acid (AMPS) for selective recognition and extraction of estradiol (E2) by temperature regulation. The resulting E2-MIPs attained controlled adsorption and release of E2 in response to temperature change, with higher adsorption capacity (8.78mg/g) and stronger selectivity (imprinting factor was 3.18) at 30°C compared with that at 20 and 40°C; the zipper-like interpolymer interaction between poly(AAm) and poly(AMPS) enabled switchable molecular recognition. The adsorption processes obeyed Langmuir isotherm and pseudo-second-order kinetic models. High recognition selectivity of the MIPs toward E2 was achieved over its structural analogues, and good reusability was displayed over 86% recovery after six adsorption-desorption cycles. Accordingly, the E2-MIPs were empolyed as new adsorbents for selective dispersive solid-phase extraction of E2, and offered low limits of detection and quantification of 4.81 and 16.03μg/L, respectively. Recoveries from goat milk samples ranged from 76.2% to 89.7% with the precisions (relative standard deviations, n = 3, %) of 2.8-3.7% at 30°C. The intelligent E2-MIPs combining good adsorption, special recognition and temperature sensitivity proved to be a promising alternative to the selective identification and controlled extraction/removal of E2 in complicated samples by simple temperature-responsive regulation.