Colloids

Solutions vs Colloids Colloidal Mixture True Solution The Tyndall Effect

Solutions vs Colloids Colloidal Mixture True Solution The Tyndall Effect

Semipermeable membrane Pure H 2 O Solution (H 2 O + Solutes) Only water passes through osmotic membranes and faster from the side on which water is more concentrated.

Semipermeable membrane Pure H 2 O Solution (H 2 O + Solutes) Diffusion rates tend to equalize as flow continues.

Dialytic membrane Pure H 2 O Mixture (H 2 O, Na + Cl -, protein) Dialysis Water and solutes pass down concentration gradient through dialytic membrane. Colloids do not cross membrane. H2OH2OH2OH2O NaCl H 2 O more concentrated here NaCl more concen- trated here

Solution Concentrations Expressed as a ratio of the amount of solute to the total amount of solution: Concentration = Amount of solute Total amount of solution Osmoles (total moles) Liters ( Osmolarity, osM) For certain solutes, osM will equal M.

Osmolarity Calculating –Total of molarities of all types of solute particles in the solution. –For ionic solutes, the ions are separated; and each ion has a separate molarity to be totaled. –Molecular solutes have same molarity and osmolarity, but each different solute needs to be included. Impact –Osmolarity determines osmotic pressure –Useful in determining net direction of H 2 O flow across membranes.

 An emulsion consists of two immiscible liquids (usually oil and water), with one liquid being dispersed as small (d = mm) spherical droplets in the other liquid.  Emulsions are thermodynamically unstable systems. EMULSION InterfacialMembrane OilDroplets AqueousPhase

Particle Size dictates Surface Area Traditional method for emulsion formation

GELS Gel: A solid network filled with a second phase of colloidal dimension, either liquid or gas that also forms a three dimensional inter-connected network. Colloidal sol-gel:  Production of Inorganic oxides either from colloidal dispersion or from the metal oxides.  Used in the synthesis (i.e) colloidal route with sol or gel intermediates.  Chemical processing to synthesis ceramics glasses, hybrids from wet chemicals.

Schematic presentation of gel formation by both colloidal and polymeric way:-

Applications of Colloids Used in  Food technology, Pharmaceutical & cosmetics.  Agricultural and horticultural chemicals paints  Dyestuffs  Paper  The processes involved in mineral extraction  Oil recovery  Water treatment  Photography  Biotechnology  Lubricants

Nano-materials Introduction Length Scale

Flowchart for Nano material synthesis

1) Physical methods: Carbon arc, Laser ablation, Vapour trapping…. 2) Chemical methods Reactant 1 + Reactant 2Product + … T, p, t Sonochemistry Microwave synthesis Hydrothermal methods Microencapsulation Sol-gel methods Wet chemical co- precipitation Methods for Nanosynthesis

Top-down versus Bottom-up

Bottom-up Process - What to control Colloidally stable nanoparticles Reproducible Adaptable surface properties Easy + cheap (Biocompatible or biodegradable systems) +

Sol-gel process

Chemical Vapor Deposition (CVD) CVD process are controlled by one of the three steps: -- Mass Transportation of Reactant -- Chemical Reaction Rate -- Desorption of Reaction Products Plasma and some other means aided CVD is to break down the precursor. Somewhat surface area limited and thus better comformality than PVD process => better for ever shrinking technology

Atomic Layer Deposition (ALD) Benefits of ALD, a Sequential, self- limiting surface reactions making alternating layers : Atomic level of control over film composition => nanolaminates and multi-component materials Uniform thickness over large areas and inside narrow holes Very smooth surfaces (for amorphous films) High density and few defects or pinholes Low deposition temperatures and pure films (for very reactive precursors) Good gap fill capability

Application

“Drug”- A substance introduced into the body to alter functionality This includes Proteins, plasmid DNA, and so fort Nano-materials in Drug Delivery systems

Application as Catalyst  Used as dye for solar cells.  Used as catalyst in bio-sensors.  Used as electrolytes.  Used in surface coating for solar cells for better efficiency (Larger surface area).  Used as a Pre-curser for material synthesis.

Advantages in Targeted Drug Delivery methods: Prevention of drug from biological degradation Effective Targeting Patient Compliance Cost effectiveness Product life extension