Surface tuneable

Hyperthermal surface ionisation (HSI) is an ultrasensitive tuneable selective ion source [222,223] which is based on the very effective ionisation of various hyperthermal molecules upon their scattering from a surface with a high work function, such as rhenium oxide. Molecule-surface electron transfer constitutes the major and most important HSI mechanism for GC-MS. 

The tuneable nature of the evanescent field penetration depth is critical to the effective operation of this sensor as it facilitates surface-specific excitation of fluorescence. This means that only those fluorophores attached to the surface via the antibody-antigen-labelled antibody recognition event... 

While planar optical sensors exist in various forms, the focus of this chapter has been on planar waveguide-based platforms that employ evanescent wave effects as the basis for sensing. The advantages of evanescent wave interrogation of thin film optical sensors have been discussed for both optical absorption and fluorescence-based sensors. These include the ability to increase device sensitivity without adversely affecting response time in the case of absorption-based platforms and the surface-specific excitation of fluorescence for optical biosensors, the latter being made possible by the tuneable nature of the evanescent field penetration depth. 

ATRP is a powerful synthetic tool for the synthesis of low molecular weight (Dp < 100-200), controlled-structure hydrophilic block copolymers. Compared to other living radical polymerisation chemistries such as RAFT, ATRP offers two advantages (1) facile synthesis of a range of well-defined macro-initiators for the preparation of novel diblock copolymers (2) much more rapid polymerisations under mild conditions in the presence of water. In many cases these new copolymers have tuneable surface activity (i.e. they are stimuli-responsive) and exhibit reversible micellisation behaviour. Unique materials such as new schizo-... 

Amongst other systems reported for the Knoevenagel condensation reaction have been, nitrogen incorporated ZSM-5 and high surface area silicon oxynitride." The ZSM-5 based -system potentially combines tuneable acid/ base properties with shape selectivity leading to the potential of selective conversion and/or unusual reaction pathways. 

The resolution of the problems outlined above will obviously require much more theoretical and experimental work before the Raman technique will become universally applicable to the study of adsorption at metal surfaces. It will be interesting to see if tuneable lasers capable of operating in the near infrared will be... 

Because of their biocompatibility, chemical stability, high thermal and electrical conductivity, sorption ability, tuneable surfaces area, pore-size distribution and straightforward functionalization chemistry, porous carbons have found application in diverse topical areas such as sensors, fuel cells, hydrogen storage, and sorption.39 11 One particular property that distinguishes porous carbon from porous silica materials is the electrical conductivity of the former that has no counterpart in siliceous-based scaffoldings. This feature opens the route for certain applications... 

For EXAFS and particularly for XANES, data analysis is complex. The oscillation frequency/bond distance dependence means that extensive use is made of Fourier transform analysis. Most applications to date have been in the EXAFS region. In order to acquire sufficiently strong signals in a reasonable time, use has to be made of high-intensity photon fluxes, which are available at synchrotron facilities. These provide a broad-band tuneable source of high-intensity radiation, but the reduced number of facilities limits widespread dissemination of the technique. Reflection (fluorescent detection) mode is usually preferred to transmission. Experiments can be conducted in any phase, and the probing of electrode surfaces in situ is an important application. 

A relatively new method for studying chemisorbed species is sum-frequency generation (SFG) (see Table 4.1 for references). This is a second-order non-linear process, requiring both a fixed visible and a tuneable laser the selection rules determine that a vibrational mode must result in changes both to dipole moment and to polarisability for the effect to occur, and this limits it to a medium which lacks inversion symmetry, i.e. to the surface and not the gas phase. This, coupled with the fact that excitation is by photons, not electrons, leads to the inestimable benefit of being usable in the presence of a high gas pressure, and therefore enables in situ examination of the surface under reaction conditions. 

Mansky P, Russell TP, Hawker CJ, Mays J, Cook DC, Satija SK (1997) Interfacial segregation in disordered block copolymers Effect of tuneable surface potential. Phys Rev Lett 79(2) 237-240... 

Gold nanoparticles have been perhaps the most widely used nanoscale material to date. Their combination of facile synthesis, inert core, well-defined surface chemistry (often analogous to gold surfaces) and size-tuneable properties make them attractive for a number of biological applications. Silver and platinum nanoparticles have also attracted attention for similar reasons. The anti-microbial abilities of silver nanoparticles are well-known. ... 

The electrochemical transduction is dynamic in that the electrode is itself a tuneable charged reagent as well as a detector of all surface phenomena, which greatly enlarges the electrochemical biosensing capabilities. 

Laser radiation is monochromatic and in many cases it also is tuneable these two characteristics together provide the basis for high-resolution laser spectroscopy. The interaction between laser radiation and molecules can be very selective (individual quantum states can be selected), permitting chemists to investigate whether energy in a particular type of molecular motion or excitation can influence its reactivity. Photochemical processes can be carried out with sufficient control that one can separate isotopes, or even write fine fines (of molecular dimensions) on surfaces. 

Typically, the UV light sources used for this type of experiment are continuous (CW) arc lamps and pulsed lasers. Arc lamps are low cost, easy to operate and provide, with band-pass filters or monochromators, tuneable radiation from the IR to the UV. It should be noted that the incident power provided by them is relatively low, and thus thermal reactions are minimized, as surface heating is negligible. 

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