The project proposal is based on our prior research activities where we learned how to prepare high quality nanostructured silicon. We have also developed ideas and gained knowledge and experience for further experimental treatments of our samples aimed on development of new properties competitive for specific applications. The project addresses fundamental physics and chemistry, properties and application of hybrid silicon nanostructures prepared by electrochemical anodisation and low pressure chemical vapour deposition (LPCVD). The project proposal consists of four interrelated research tasks: silicon/hybrid nanostructures for gas sensing; low light infrared detection; surface enhanced Raman spectroscopy (SERS) in food technology and spherical optical microresonators in low concentration molecular detection. The proposed tasks are mutually interconnected by the CMOS technology compatible materials production based on inexpensive silicon, and by the search for their specific advanced applications. For the achievement of the proposed research tasks we have organized a team of 14 researchers (9 scientists and 5 PhD students) from 2 scientific institutions, 2 faculties and 1 institution in the private sector and 2 renowned institutions from abroad. Electrochemical processes will be used for construction of tailored pore sizes and volumes in silicon that are controllable on the scale from nano- to micrometers. A number of suitable chemistries will be applied for the functionalization of porous Si surfaces for gas sensing, IR sensors and SERS spectroscopy. The novel silicon heterostructures deposited by the LPCVD method on silica spherical optical microresonators will be investigated for possible applications in molecular sensing. The structural, optical and electrical properties of such functional silicon nanostructures will be examined from the fundamental science point of view as well as for development of specific high-tech products needed by the Croatian industry.