Colloids

Solutions vs Colloids

Colloidal MixtureColloidal MixtureTrue SolutionTrue Solution

The Tyndall EffectThe Tyndall Effect

Solutions vs Colloids

Colloidal MixtureColloidal MixtureTrue SolutionTrue Solution

The Tyndall EffectThe Tyndall Effect

Semipermeable membraneSemipermeable membrane

PurePureHH22OO

SolutionSolution(H(H22O +O +

Solutes)Solutes)

Only water passes through Only water passes through osmotic osmotic membranes and faster membranes and faster fromfrom the side on which water is more concentrated. the side on which water is more concentrated.

Semipermeable membraneSemipermeable membrane

PurePureHH22OO

SolutionSolution(H(H22O +O +

Solutes)Solutes)

Diffusion rates tend to equalize as flow continues.Diffusion rates tend to equalize as flow continues.

Dialytic membraneDialytic membrane

PurePureHH22OO

MixtureMixture(H(H22O,O,

NaNa++ClCl--,,protein)protein)

DialysisDialysis

Water and solutes pass down concentration gradient through Water and solutes pass down concentration gradient through dialytic dialytic membrane. Colloids do not cross membrane.membrane. Colloids do not cross membrane.

HH22OO

NaClNaCl

HH22O O more more

concentrated concentrated herehere

NaCl NaCl more more concen-concen-trated trated herehere

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, For certain solutes, osMosM will equal will equal MM..

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 H2O flow

across membranes.

An emulsion consists of two immiscible liquids (usually oil and water), with one liquid being dispersed as small (d = 0.1 - 100 mm) spherical droplets in the other liquid.

Emulsions are thermodynamically unstable systems.

EMULSION

InterfacialInterfacialMembraneMembrane

OilOilDropletsDroplets

AqueousAqueousPhasePhase

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 2 Product + …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