| 1. |
- Chen, Y. C., et al.
(författare)
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Evaluation of molecularly imprinted polyurethane as an optical waveguide for PAH sensing
- 2004
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Ingår i: NANOSENSING. - : SPIE. ; , s. 513-520
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Konferensbidrag (refereegranskat)abstract
- We developed a numerical model for the fluorescence output efficiency of a molecularly imprinted polymer (MIP) waveguide sensing system. A polyurethane waveguide imprinted with a polycyclic aromatic hydrocarbon (PAH) molecule was fabricated using micromolding in capillaries. The coupling of light into a 5 mm long MIP segment was verified by comparing the output transmission signals of a deuterium lamp from the MIP waveguide collected by, an optical fiber with the background lamp signals collected by the same optical fiber. It was found that polyurethane MIP was an effective waveguide but absorbed much shorter wavelengths, especially ill the UV region. thereby the transmission of light appeared orange/red in color. The high background absorption of polyurethane in the spectrometric regions of interest was found to be a critical problem for sensor sensitivity. Our numerical model shows that the fluorescence output is only 2 X 10(-6) of the input excitation for 25 mM anthracene for a 5mm polyurethane waveguide. A 10 fold decrease of background absorption will increase the fluorescence output 250 times.
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| 2. |
- Chen, Y. C., et al.
(författare)
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Fluorescence-based optical sensor design for molecularly imprinted polymers
- 2004
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 102:1, s. 107-116
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Tidskriftsartikel (refereegranskat)abstract
- A Monte Carlo model was developed to analyze the sensitivity and the performance of a fluorescence-based molecularly imprinted polymer (MIP) sensor. The MIP sensor consisted of highly cross-linked polyurethane containing anthracene binding sites coated on a transparent substrate. The optical properties of MlPs, the quantum yields of anthracene within MIPs, and the fluorescence of MlPs were measured. The rebinding capacity of the MIPs was about 1 mumol/g or roughly seven times binding rate of non-imprinted polymers. The MIP fluorescence emission at 404 nm was measured for thicknesses ranging from 100 to 2000 mum containing templated anthracene concentrations ranging from 60 to 600 ppm for excitation at 358 nm. The emission agreed with model predictions within 15%. This sensing system could only distinguish anthracene down to 15 ppm due to fluorescence from the polymer matrix. To make a fluorescence-based MIP sensor that is capable of detecting one part per billion analyte concentration with a 200 mum thick MIP film, our model suggests that imprinted polymers would need to have an absorption coefficient less than 0.001 cm(-1), or have a quantum yield 10(5) times lower than that of the analyte at the detection wavelength.
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| 3. |
- Chen, Y. C., et al.
(författare)
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Steady-state fluorescence anisotropy studies of molecularly imprinted polymer sensors
- 2004
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Ingår i: MOLECULARLY IMPRINTED MATERIALS-2003. - : Materials Research Society. - 1558997253 ; , s. 35-39
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Konferensbidrag (refereegranskat)abstract
- Molecularly imprinted polymers (MIPs) are used as recognition elements in biochemical sensors. In a fluorescence-based MIP sensor system, it can be difficult to distinguish the analyte fluorescence from the fluorescence of the polymer itself. We studied steady-state fluorescence anisotropy of anthracene imprinted in a polymer (polyurethane) matrix. Vertically polarized excitation light was incident on MIP films coated on silicon wafers; vertically and horizontally polarized emission was measured. We compared the fluorescence anisotropy of MIPs with imprinted molecules, MIPs with the imprinted molecules extracted, MIPs with rebound molecules, and nonimprinted control polymers. It is shown that differences in fluorescence anisotropy between the polymers and imprinted fluorescent molecules may provide a means to discriminate the fluorescence of analyte from that of the background polymer.
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| 4. |
- Graupner, R K, et al.
(författare)
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Theoretical model for photochemical or thermally activated immobilization of macromolecules
- 2004
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 20:20, s. 8675-8680
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Tidskriftsartikel (refereegranskat)abstract
- The covalent immobilization of macromolecules on surfaces and within 3-dimensional networks is quantitatively described using a model based on Poisson statistics. This model determines the immobilized density or layer thickness as a function of molecular weight of the macromolecule or radiant exposure prior to and following the surface deposition of the macromolecule. Measurements of immobilized layer thickness provide first-order rate constants for decomposition of the surface-bound linker molecules and an estimate of the surface-bound linker density. The model predicts the relative density of immunocomplexed antibodies as a function of the irradiation time used to immobilize antigens. By providing the average number of bonds to the immobilized molecule, the model enables studies of the effect of multiple bonds on the activity of biomolecules. Experimental data by the authors and from the literature validate the model.
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| 5. |
- Yan, Mingdi, et al.
(författare)
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Covalent immobilization of ultrathin polymer films by thermal activation of perfluorophenyl azide
- 2004
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 16:9, s. 1627-1632
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Tidskriftsartikel (refereegranskat)abstract
- The attachment of thin films on solid materials is an effective way to tailor the chemical and physical properties of the surface layer. In this article, we report an alternative approach to the covalent immobilization of ultrathin polymer films. The immobilization chemistry is based on the C-H/N-H insertion reaction of perfluorophenyl nitrenes that were generated by the thermal activation of perfluorophenyl azides (PFPAs). In the process, a silicon wafer was treated with PFPA-silane 1 to give a monolayer of azido groups on the surface. A polymer was then spin coated on the functionalized wafer and the sample was heated. Thermolysis produced perfluorophenyl nitrenes which underwent insertion reactions with the neighboring polymer chains. Removal of the excess polymer by solvent extraction resulted in nanometer-thick polymer thin films covalently attached to the wafer surface. Using polystyrene and poly(2-ethyl-2-oxazoline) as examples, covalently immobilized thin films with thicknesses ranging from a few to over a hundred A were obtained. The thickness of the film could be controlled by the type and the molecular weight of the polymer. Patterned polymer films were also fabricated using this method.
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| 6. |
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| 7. |
- Yan, Mingdi, et al.
(författare)
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Polymeric structures, particularly microstructures, and methods for making same
- 2001
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Patent (populärvet., debatt m.m.)abstract
- Methods of adhering polymeric materials to a substrate, either directly or through linker molecules, are disclosed. Structures, for example, microstructures, including microwells and arrays of microwells, may be readily formed using the methods. In some embodiments, microstructures formed completely from polymeric materials are provided, making it possible to tailor the chemical and physical properties of the microstructures. For example, microwells having a bottom comprising a polar polymeric material and well sides/top comprising a non-polar polymeric material are provided. Biochemical reagents may be easily delivered to such "smart wells" because the intrinsic attraction of the well bottom for the reagents and the intrinsic repulsion between the well sides/top combine to direct the reagents to the wells.
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