Hello there! I got some question regarding nanoparticles. 1) It is well known fact that peak broadening occurs when the particle size falls in nano range, but does anybody know what's the reason of peak broadening compared to the bulk material? 2) What is the color of metal nanoparticles dependent on? 3) Why do we obserwe a non exponential decay of emission for rare earth ions? 4) What is an optimal ligand for application in biology and photovoltaic? Thank you for your response.