McGill University researchers have made a cheap, portable, paper-based filter coated with silver nanoparticles to be used in emergency situations which needs clean drinking water.
Silver

Silver has is a precious metal used to make ornaments, jewelry, high-value tableware, utensils and currency coins, nowadays in electrical contacts and conductors, in mirrors and in catalysis of chemical reactions. Its compounds are used in photographic film and dilute silver nitrate solutions and other silver compounds are used as disinfectants and micro biocides.

Silver has been used to clean water for a very long time by keeping water in silver jugs in ancient days. According to Jeffrey Ellis, Adjunct Professor of Chemistry at Florida International University in Miami, the use of silver as a water treatment by business and industry is on the rise. The global community is now rapidly moving toward using silver as a safe and effective treatment for drinking water worldwide.

Nanosilver

Nanosilver is silver (Ag) in suspension with pure de-ionized water. Approximately 80% of the silver is in the form of metallic silver nano-particles. The remaining silver is in ionic form. Though similar to colloidal silver, generally, a colloid is a suspension of particles of from 10 nm to 1 micron in diameter and the silver particles in Nano-Silver are less than 2 nm in diameter and therefore too small to be considered in "colloidal" suspension. They are rather, in a "nano-suspension," a much more stable state.

Nano Silver Antibacterial Powder is used in ceramic (enamel) products, fabric, plastic products, pigment, coin, check, wallpaper glue, architectural structure glue, and wallpaper, etc.

Nanosilver cleans water
Eventhough silver is used to get rid of bacteria in a variety of settings, from bandages to antibacterial socks, no one has used it systematically to clean water before.
McGill's Department of Chemistry researchers have coated thick (0.5mm) hand-sized sheets of an absorbent porous paper with silver nanoparticles to get rid of bacteria. The researchers poured live bacteria through the treated paper and when viewed through an electron microscope, the paper had only silver dots all over even when the contaminated water goes through. The results indicated that even when the paper contained a small quantity of silver (5.9 mg of silver per dry gram of paper), the filter was able to kill nearly all the bacteria and produce water that meets the International water quality standards.
The researchers claim that the filter is not a routine water purification system, but is a way of providing rapid small scale purification system under emergency situations. According to the researchers it works well in the lab but needs to improved and developed for the practical use.