Choices solid-state system components

Semiconductor photodiodes are the natural choice for building an optofluidic device with integrated on-chip detection. The immediate consequence is that the chip has to either be entirely semiconductor based or be a hybrid system with soft material fluidic components and a solid-state... 

In the sol-gel preparation of such a system a key aspect concerns the control over chemical composition through the choice of proper annealing procedures. Indeed, gel-derived Zn0-Si02 mixtures could lead to the formation of undesired ceramic zinc silicate at temperatures lower than those expected for conventional solid-state reactions [172], Activation energies, and thus the temperatures necessary to get crystalline phases usually are much lower when the ceramic materials are formed from an amorphous gel with a high dispersion of the individual components, rather than if ions have to diffuse through crystal lattices. 

We now have the foundation for applying thermodynamics to chemical processes. We have defined the potential that moves mass in a chemical process and have developed the criteria for spontaneity and for equilibrium in terms of this chemical potential. We have defined fugacity and activity in terms of the chemical potential and have derived the equations for determining the effect of pressure and temperature on the fugacity and activity. Finally, we have introduced the concept of a standard state, have described the usual choices of standard states for pure substances (solids, liquids, or gases) and for components in solution, and have seen how these choices of standard states reduce the activity to pressure in gaseous systems in the limits of low pressure, to concentration (mole fraction or molality) in solutions in the limit of low concentration of solute, and to a value near unity for pure solids or pure liquids at pressures near ambient. 

The effect of pressure on AG° and AH0 depends on the choice of standard states employed. When the standard state of each component of the reaction system is taken at 1 atm pressure, whether the species in question is a gas, liquid, or solid, the values of AG° and AH0 refer to a process that starts and ends at 1 atm. For this choice of standard states, the values of AG° and AH0 are independent of the system pressure at which the reaction is actually carried out. It is important to note in this connection that we are calculating the enthalpy change for a hypothetical process, not for the actual process as it occurs in nature. This choice of standard states at 1 atm pressure is the convention that is customarily adopted in the analysis of chemical reaction equilibria. 

Special consideration must be given to systems involving liquid solutions of at least one solid component, for which the choice of either the pure solid or pure supercooled liquid as the standard state is not convenient. This case is encountered for all solutions in which the pure solute is not chosen as the reference state. As an example, we consider an aqueous solution of a solid B and choose the reference state to be the infinitely dilute solution. Then a general change of state for the formation of the solution from the components is written as... 

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