Imprinting crystal

Bulk and surface imprinting strategies are straightforward tools to generate artificial antibodies. Combined with transducers such as QCM (quartz crystal microbalance), SAW (surface acoustic wave resonator), IDC (interdigital capacitor) or SPR (surface plasmon resonator) they yield powerful chemical sensors for a very broad range of analytes. 

Figure 19 illustrates key steps of the FI2O2 formation at the nanostructured catalyst surface. An important feature is the imprintment and maintenance of the (11 0) crystal surface through the polymer template because the specific row of metal atoms favours the formation of hydrogen peroxide while minimizing byproducts such as water. 

Quite a number of recent papers have concentrated on techniques which allow the gravimetric detection of only a few femtograms of an analyte [105]. In one of these, PAHs could be measured in concentration of down to a few ng ml-1 in degraded oil when a piezoelectric quartz crystal coated with Mi-polymers imprinted either with a fresh or with a degraded lubricant was immersed into the... 

The improvement of enzyme like MIP is currently another area of intense research. Beside the use of the MIP themselves as catalysts, they may also be applied as enhancer of product yield in bio-transformation processes. In an exemplary condensation of Z-L-aspartic acid with L-phenylalanine methyl ester to Z-aspartame, the enzyme thermolysin was used as catalyst. In order to shift the equilibrium towards product formation, a product imprinted MIP was added. By adsorbing specifically the freshly generated product from the reaction mixture, the MIP helped to increase product formation by 40% [130]. MIP can also be used to support a physical process. Copolymers of 6-methacrylamidohexanoic acid and DVB generated in the presence of calcite were investigated with respect to promotion of the nucleation of calcite. Figure 19 (left) shows the polymer surface with imprints from the calcite crystals. When employing these polymers in an aqueous solution of Ca2+ and CO2 the enhanced formation of rhombohedral calcite crystals was observed see Fig. 19 (right) [131]. 

A profile imprinted on a crystal surface will undergo morphological changes when relaxing towards equilibrium. This morphological evolution has been foiind, in experiments and theoretically, to be significant different above and below the roughening transition of the relevant surface. - ... 

Results of Monte Carlo simulations on the healing of profiles imprinted on a crystal surface have been briefly reviewed, together with experimental findings and predictions of analytic theories. 

Figure 15.7 Response of the molecular imprinted polymer quartz crystal microbalance (MIP-QCM) sensor to monoterpene analogues ( ) L-menthol, (A) D-menthol, ( ) citronel-lol, (A) citronellal, and (O) menthone. Reprinted from Percival et al. (2001). Copyright 2001 American Chemical Society.

Percival CJ, Stanley S, Galle TM, Braithwaite A, Newton MI, McHale G, Hayes W. Molecular-imprinted, polymer-coated quartz crystal microbalances for the detection of terpenes. Anal Chem 2001 73 4225-4228. 

Piacham T, Josell A, Arwin H, Prachayasittikul V, Ye L. Molecularly imprinted polymer thin films on quartz crystal microbalance using a surface bound photo-radical initiator. Anal Chim Acta 2005 536 191-196. 

Figure 3 Fractional surface coverage 0. determined using Eq. (3), as a function of ammonia pressure for (a) an etched w-CdSe crystal and (b) a n-CdSe crystal coated with an ammonia-imprinted PAA film. The insets show the same data as double reciprocal plots, yielding equilibrium constants for (a) and (b) of 750 250 and 1000 500...

S. P. Pogprelova, M. Zayats, T. Bourenko, A. B. Kharitonov, O. Lioubashevski, E. Katz, and L Willner, Analysis of NAD(P) /NAD(P)H Cofactors by Imprinted Polymer Membranes Associated with Ion-Sensitive Field-Effect Transistor Devices and Au-Quartz Crystals, Anal. Chem. 2003, 75, 509. 

Another nice example of nanostructuring an MIP layer is the work published by Wu et al. [138, 139] who developed a label-free optical sensor based on molecularly imprinted photonic polymers. Photonic crystals were prepared by self-assembly of silica nanospheres. The space between the spheres was then filled with MIP precursor solution. After polymerization, the silica was dissolved, leaving an MIP in the form of a 3D-ordered interconnected macroporous inverse polymer opal (Fig. 15). The authors were able to detect traces of the herbicide atrazine at low concentrations in aqueous solution [139]. Analyte adsorption into the binding sites resulted in a change in Bragg diffraction of the polymer characterized by a color modification (Fig. 15). 

An MIP-QCM chemosensor for determination of carbamate pesticides, such as carbaryl, has been devised [130]. The chemosensor featured a thin film of PVC, containing carbaryl-imprinted polymer microspheres, which was deposited on top of the gold-sputtered quartz crystal transducer. The microspheres were prepared by thermo-induced co-polymerization in ACN of MAA and EGDMA, used as the functional monomer and cross-linker, respectively, in the presence of carbaryl and AIBN serving as the template and initiator, respectively. The chemosensor performance was evaluated for determination of carbaryl exhibiting the linear concentration range of 10-1000 ng mL-1 in the Britton-Robinson buffer of pH = 8.0. This chemosensor was highly stable. It selectively discriminated carbaryl from its structural counterparts, such as carbofuran and aldicarb, with LOD of 1.25 ng mL-1 carbaryl. 

Table 5 Comparison of performance of quartz crystal microbalance chemosensors using molecularly imprinted polymer for determination of caffeine... 

Fig. 5 Mass change, under FIA conditions, of the MIP film (imprinted with L-aspartic acid) due to injection of a 10-mM sample of L-aspartic acid or D-aspartic acid into the KC1-HC1 carrier solution (pH = 1.6). The MIP film was deposited on a gold-coated quartz crystal resonator held at a constant potential of —0.4 V (adapted from [148])...

When the indentation hardness is measured, a small sphere or the tip of a pyramid-shaped crystal of a material which is harder than the one to be tested is pressed in the surface. The depth of the imprint is a measure for the hardness. Especially in the case of porous material it is vital that the determination is carried out carefully to avoid that... 

Yeah, he said. A crystal, with a wonky kite design imprinted on its structure at a molecular level. The same one we found on a book. A cross-section, the Doctor had pointed out again, of a diamond. Diamante, Trix had translated pointedly, solely for Fitz s benefit. 

Ersoz A, Denizli A, Ozcan A, Say R. Molecularly imprinted ligand-exchange recognition assay of glucose by quartz crystal microbalance. Biosensors Bioelectronics 2005, 20, 2197-2202. 

Molecularly imprinted polymers (MIPs) oscillating quartz crystals Magnetic Toroids ... 

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