Solution-casting-evaporation

Several experiments were performed on a DNA biosensor based on CHT film doped with CNT. The observation made was that a CNT/CHT film can be used as a stable and sensitive platform for DNA detection. The results demonstrated improved sensor performance as a result of adding CNT to a CHT film. Moreover, the analytical performance of glassy carbon electrodes modified with a dispersion of MWNT/CHT for DNA quantification was reported. This new platform immobilised the DNA and opened the doors to new strategies for the development of biosensors. 

Other experiments have reported the high sensitivity of glassy carbon electrodes modified by MWNT-CHT for cathodic stripping voltammetric measurements of bromide. 

Researchers prepared an amperometric hydrogen peroxide biosensor based on composite films of MWNT/CS. The results showed the excellent electrocatalytic activity of the biosensor for hydrogen peroxide with good repeatability and stability. 

Some researchers reported the effect of the CNT/CHT matrix on an amperometric laccase biosensor, evidencing some of its major advantages, including detection of different substrates, high affinity and sensitivity, durable long-term stability, and facile preparation procedures. 

Others have paid particular attention to the preparation of a SWNT/CHT film by the solution-cast method, then characterised its drug delivery properties. They found out that the the release of dexamethasone from the film was slowed down in the presence of SWNT compared with the release rate from pure CHT films. 

---

Most solution-cast composite membranes are prepared by a technique pioneered at UOP (35). In this technique, a polymer solution is cast directly onto the microporous support film. The support film must be clean, defect-free, and very finely microporous, to prevent penetration of the coating solution into the pores. If these conditions are met, the support can be coated with a Hquid layer 50—100 p.m thick, which after evaporation leaves a thin permselective film, 0.5—2 pm thick. This technique was used to form the Monsanto Prism gas separation membranes (6) and at Membrane Technology and Research to form pervaporation and organic vapor—air separation membranes (36,37) (Fig. 16). 

The first five of these techniques involve deformation and this has to be followed by some setting operation which stabilises the new shape. In the case of polymer melt deformation this can be affected by cooling of thermoplastics and cross-linking of thermosetting plastics and similtir comments can apply to deformation in the rubbery state. Solution-cast film and fibre requires solvent evaporation (with also perhaps some chemical coagulation process). Latex suspensions can simply be dried as with emulsion paints or subjected to some... 

Chitin films can be manufactured from DMAc solutions or by other approaches, for example, blend films of beta-chitin (derived from squid pens) and poly(vinyl alcohol) (PVA) were prepared by a solution casting technique from corresponding solutions of beta-chitin and PVA in concentrated formic acid. Upon evaporation of the solvent, the film having 50/50 composition was found to be cloudy [224]. 

A membrane prepared by PVA blending with PAcr.Ac. in aqueous solution, casting, solvent evaporation and then crosslinking by heat treatment (at 150 °C), has been used. 

A solution of 2 g (2 wt%) of polyisoprene (see Example 3-12) in 100 ml of dry toluene is prepared.To 50 ml of this solution 1 mg of IRGANOX 565 2,6-di(ferf-butyl)-4-[4,6-bis(octylthio)-1,3,5-triazin-2-ylamino]phenol, Ciba Specialty Chemicals is added. From either solution a film is cast.To do this, 5 ml of the solution are evaporated in a... 

In the preparation of the cellulose blends listed above, two methods were mainly adopted casting from solutions by evaporation of solvent, and coagulation of solutions in a non-solvent followed by drying. Both processes involve dissolution and mixing of two polymer components in a common sol-... 

Perhaps the most common method for preparing polymer-nanotube composites has been to mix the nanotubes and polymer in a suitable solvent before evaporating the solvent to form a composite film. One of the benefits of the solution casting method is that agitation of the nanotube powder in a solvent facilitates nanotube de-aggregation and dispersion. Almost all solution processing methods are variations on a general theme which can be summarized in three major steps ... 

Under certain conditions, rather well-defined ring and honeycomb patterns can be formed by solution casting of thin films. Recently Nolte described the formation of isolated rings with diameters of several micrometers formed by stacked porphyrin molecules [287], Phase segregation or eruption of gas bubbles was assumed to be responsible for the peculiar assembly of the porphyrin wheels . However, the regular shape of the solute molecules was also considered to be of crucial importance, Another example is the honeycomb pattern of star shaped poly(styrene)-block-poly(-p-phenylene) films described by Francois [288], In this case, the peculiar molecular shape was emphasized to be of crucial importance besides the proper choice of solvent and evaporation conditions [289],... 

Fig. 6. Elimination coefficient versus temperature of casting solution at 0.06 MPa (1) 0.12 MPa (2) and 0.18 MPa (3) for membranes cast from 15 wt. % PS solution. Solvent evaporation time Os (A) 15s(B)...

Thin films with a thickness of 50 pm of a commercially available PS-PB-PS triblock copolymer (e.g. from BASF, 74% PS, 26% PB) are prepared by solution casting from a 3% solution in toluene onto TEFLON -foil, which is placed in a precleaned petri-dish. The solvent is slowly evaporated over a period of 2 weeks. Residual solvent is then removed and films are annealed under reduced pressure in a vacuum oven at 120°C (48 h). Finally, the films are removed from the support and are uniaxially stretched at a constant strain rate of 0.1 s 1 beyond the yield point at room temperature. ARM investigations are carried out on prestretched samples that are mechanically clamped or fixated by double-sided sticky tape onto the AFM sample holder. 

Fig, 10.24. Simplified schematics illustrating some deposition techniques (a) thermal evaporation (b) stamping (c) liquid-solid interface (d) electro-chemistry set-up (e) Langmuir-Blodgett technique (f) electro-spray deposition (g) pulse injection method (h) solution casting (i) spin-coating. 

Via solution casting (Fig. 10.24h) a droplet of solvent containing the molecules is deposited onto the substrate and the solvent evaporates. Typically, millimolar solutions are used for this method, which therefore only need small quantities of substance. The solvent has to be chosen not to adsorb on the substrate and leave enough time (prior to evaporation) to allow molecular organization. This method leads to reproducible results, also for supermolecules. Solution casting on a heated substrate is often referred to as sizzling [137]. 

Optical Spectroscopy. Figure 7 shows the optical spectra of solution cast (from slowly evaporated methylene chloride solution) poly(, 8-nonadlyne) films which have been exposed to UV light (1600 uW/cm at 254 nm, under UHP argon purge) for various times. The macromonomer has no absorbance maxima In the region shown, whereas, samples with less than about 5 minutes exposure have two dlscernable maxima- at 575 nm and 630 nm. At low conversions (about 2 to 11... 

The high value of the water flux parameter DiCi, along with adequately low NaCl transport, motivated the fabrication of p-2221 into asymmetric membranes. The preparation of asymmetric membranes is a multistep process involving solution casting, partial solvent evaporation, and gelation as the most critical operations. The resulting asymmetric structure (a thin dense "skin" supported by a porous substructure 50-100 urn in thickness) combines the high flux of a thin membrane with the mechanical properties of a much thicker film. 

Depositing polymer membranes from solution is probably the oldest and simplest method for polymer deposition. Typically a solution of the polymer is deposited onto the transducer surface and allowed to dry. Although this technique is simple to practice, it is a fine art to perfect. Polymer concentration, solvent composition, amount of solution deposited, and solvent evaporation rate are all crucial parameters to control in order to obtain films that adhere well to the substrate, are uniform in thickness, and are free from defects. Gregg and Heller have solution cast redox-functional hydrogels containing glucose oxidase on an electrode to fabricate a glucose sensor [19]. 

Figure 8.19. Phase diagram of PVC/NBR/THF and optical micrograph of the solution cast fdm. Spinodal and binodal curves are shown by the broken and solid lines, respectively. The arrow indicates the casting (evaporation) process [Inoue et al., 1985],...

---