Dr Milan Kumar Sanyal speaks at the meet

It’s like playing billiards with balls that are actually clusters of atoms, far thinner than a human hair. Scientists obsessed with plodding atoms know the tricks of the game. While fiddling with such minute balls, they have stumbled upon tiny structures as small as viruses, and some even smaller than them. Known as nanostructures, they work wonders, from carrying electricity to sensing even a tiny drop in humidity in atmosphere. Such powers of nanostructures were discussed at a one-day seminar at the Saha Institute of Nuclear Physics (SINP) recently. The Materials Research Society of India (MRSI), Kolkata Chapter, and West Bengal Academy of Science and Technology (WAST) jointly organized the seminar to celebrate the World Year of Physics.

“One hundred years ago, Albert Einstein set the stage for studying matter at the microscopic level in his paper on the Brownian motion (zigzag movements of particles suspended in a liquid),” said Dr Bikash Sinha, director, SINP, in his lecture on ‘Albert Einstein, 1905: Contemporary Applications of Special Theory of Relativity and Brownian Motion’. “In that paper, he calculated the average trajectory of a microscopic particle buffeted by random collisions with molecules of the fluid or gas. It’s been observed that quarks, the tiniest component of matter, perform Brownian motion in a soup called quark-gluon plasma.”

“Sophisticated imaging techniques have shown that atoms and molecules coalesce to form clusters of nanoparticles, ultimately giving rise to stable nanomaterials,” said Dr Milan Kumar Sanyal of SINP in his lecture on ‘Growth Mechanism and Electrical Properties of Nanomaterials’. “We have produced nano-sized gold particles, which show magnetic as well as electrical properties,” he added. According to him, nanomaterials will play a vital role in enhancing computer memory.

Dr Dipankar Chakravorty, from the Indian Association for Cultivation of Science (IACS), explained how, resorting to various chemical tricks, experts were making different core-shell structures. Speaking on ‘Nano Core-shell Structures and Their Properties’, he said, “Exploiting the void space within silica-based glass structures, different nanostructures with core-shell have been produced. Changing temperature and using chemical reactions like reduction and oxidation we have carved out nano-sized shells of silver, which behave like semiconductors.” According to him, seen through sophisticated microscopes nano-shells of iron and iron oxides were found to produce wonderful leafy structures.

With changes in size, nanocrystals change their structure. “This gives rise to nanocrystals with novel properties,” said Dr Dipankar Das Sarma of the Indian Institute of Science, Bangalore, in his lecture on ‘Electronic Structure of Nanocrystals: A Story of Tuning Properties By Tailoring Sizes’. Nanocrystals of various shapes have been made from zinc oxides, he added.

Speaking on ‘Playing Billiards at the Nanoscale’, Dr G.U. Kulkarni from the Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore said, “Nanoparticles could be moved around like billiard balls.” According to him, a thin probe of sophisticated atomic force microscopy could give an extremely delicate kick to a cluster of gold nanocrystals, breaking the cluster into two fragments.

Biplab Das