"High sensitive thermal imaging for biomedical and microelectronic application"

The great interest of using nanoparticles (NPs) for bioapplications is associated, except of their small size, with the possibility to create multifunctional NPs that enable multifuntionality within single particle. Thanks to this it is possible i.e. to determine exact position of the NPs into biological systems by analyzing their luminescence (luminescent bioimaging). It is especially important if the specific type of functional group will be attached onto NP’s surface making them e.g. specific cancer cells labels. Moreover, this kind of particles can be used as local, selective heaters via light-into-heat conversion of photoexcitation light. The great importance of such possibility is associated with using so called ‘nanoheaters’ for local hyperthermia generation of cancer cells in in vivo experiments. Since thermal resistivity of cancer cells is lower than thermal resistivity of healthy cells it is possible to create local overheating of cancer cells with reduction of the damages occurring to healthy cells. However in order to further reduce damages caused by overheating, it is of crucial importance to monitor the NP’s temperature in real time. Infrared camera allows only for determination of temperature of the surface/skin of the biological system/organism, which can significantly differ from temperature of the NPs localized even few mm below the surface/skin. Direct temperature determination of the NP is possible based on the so called ‘luminescent thermometry’. This technique allows for non-contact temperature determination of the luminescent NPs basing on their luminescent features like emission spectra or luminescence decay profiles. One of the most accurate type of luminescent thermometers is called ‘ratiometric’ - technique that is based on the thermal induced changes of the relative emission bands intensities. Thanks to this, the influence of the tissue scattering, amount of the phosphor and the intensity of exciting light on temperature determination is minimized.

Among many different materials used for non-contact temperature determination the rare-earth doped nanocrystals seems to the especially attractive due to their good photo-chemical stability, low cytotoxicity, high thermal stability and high emission intensity. Despite the fact that luminescent thermometry is well known technique of temperature determination, no wide field temperature mapping have been presented up to now. Therefore the main aim of this project is to develop technique that allows for thermal mapping of biological and microelectronic objects with fast response-time, high temperature sensitivity and high spatial resolution based on a new type of highly sensitive luminescent thermometers. In this project we propose a new type of luminescent thermometers for which combination of d-d transition of transition metal ions with f-f transition of lanthanide ions will be used for temperature determination and applying them for creation of thermal maps of different objects. These maps allow for thermal characterization on living cells and electronic elements. Such thermal visualization of objects is of fundamental meaning for bioapplication since great number of physiological processes involve change of temperature. Therefore, the capability to map temperature with high spatial and thermal resolution will give inside into in-real time analysis of processes taking place at cellular level. In case of electronics, the possibility of thermal mapping will allow for fast and easy detection of overheating spots or edges of electronic systems and microprocessors preventing their destruction and allowing for reasonable designing of new generation of integrated circuits. Preparation of such thermal map is nowadays strongly limited due to their low sensitivity.