Projects / Programmes
Characterization of semiconductor nanomaterials by determining their optical and thermal parameters using the photothermal effect
| Code |
Science |
Field |
Subfield |
| 7.00.00 |
Interdisciplinary research |
|
|
| Code |
Science |
Field |
| T000 |
Technological sciences |
|
| Code |
Science |
Field |
| 2.05 |
Engineering and Technology |
Materials engineering |
photothermal measurements (photothermal methods), semiconductor nanofilms, nanomaterials, optothermal and transport properties, thermal lens spectroscopy, photothermal spectrometry, photothermal beam deflection, photoacoustic measurements
Researchers (1)
| no. |
Code |
Name and surname |
Research area |
Role |
Period |
No. of publicationsNo. of publications |
| 1. |
31463 |
PhD Dorota Agnieszka Korte |
Control and care of the environment |
Head |
2011 - 2013 |
156 |
Organisations (1)
| no. |
Code |
Research organisation |
City |
Registration number |
No. of publicationsNo. of publications |
| 1. |
1540 |
University of Nova Gorica |
Nova Gorica |
5920884000 |
14,072 |
Abstract
Nanomaterials (NMs) due to their unique properties became attractive materials for many purposes ranging from the applications in medicine to various industrial products. Among all the parameters of NMs, their thermal properties are the least extensively investigated, even though they are very important for understanding and improving materials properties and applicability. NMs properties depend on the structure of NMs but their variations are very subtle, therefore, highly sensitive and precise detection methods are required for their determination. These requirements are satisfied by the methods based on photothermal effects. Among them are: the photothermal deflection (PD), photoacoustic (PA) and thermal lens spectrometric (TL) techniques. The general principle of all of photothermal techniques relies on the generation of heat by periodical excitation of the sample. As a result of the nonradiative relaxation of the energy absorbed by the sample, a temperature gradient is generated, which changes the physical parameters (eg. density, refractive index) of the sample and its surroundings. These changes can be probed in different ways depending on the chosen measurement technique. The PD technique is usually based on probing the periodic temperature disturbance in the medium surrounding the illuminated sample close to its surface by a laser beam, which is deflected by the periodic gradient of the refraction index resulting from these temperature disturbances. In the PA technique the changes in gas pressure resulting from photothermal effect in the sample or it’s surroundings are measured by the use of a sensitive microphone. In case of TL spectrometry the thermal lens arising from a refractive index gradient due to changes in temperature causes the defocusing of the laser beam passing through a transparent sample. In all three cases the detected signal depends on the thermooptical as well as transport parameters of the sample.
Among the NMs of high interest are those with photocatalytic properties, where TiO2 is one of the most widely investigated. The disadvantage of TiO2 is high band gap energy (~3.2 eV), which limits its application in the visible light range. Another disadvantages is the charge carrier recombination (e-/h+) which occurs within nanoseconds. As a consequence, the photocatalytic activity of TiO2 is limited. Therefore, it is necessary to modify the structure of TiO2 materials, by doping or changing the conditions of deposition process. This will change its thermal and optical parameters, that can be related to improved photocatalytic activity.
Another group of materials which will be examined as part of this research are the organic and small molecule semiconductor materials as well as semimetal thin films used in optoelectronic applications. Similarly to the case of TiO2, modification of their structure leads to increase of charge transport efficiency, and consequently increased response time and reduced power loss in materials for devices such as solar cells. The charge transport efficiency is determined by eg. charge density, their recombination speed or mobility, which are also related to thermal diffusivity of the semiconductor NMs.
The objectives of the proposed research are therefore focused on the development and application of novel, highly sensitive PT methods for determination of thermal and optical parameters of some selected NMs, which will include thin TiO2 films for photocatalysis, small molecule and organic semiconductors for solar cells, as well as semimetals as grapheme for electronic applications. Their optothermal parameters, chemical composition and structural characteristics will be determined and optimatization of parameters for synthesis of NMs based on TiO2 with better photocatalytic efficiency and organic nanostructured semiconductor films providing higher conversion efficiency of solar cells will be performed.
Significance for science
Relevance to the science: Most important contributions of the proposed project to development of science are : 1) validation of existing theory of photothermal effects and development of novel theoretical models which describe photothermal effects in thin film semiconductor materials. 2) Optimization and selection of the best suited optothermal technique for determination of optical an thermal properties of nanolayered semiconductor materials applied in photocatalysis and photovoltaics 3) Measurements of optical (absorbance spectra, band gap energies) and thermal properties (thermal diffusivity, efusivity, thermal conductivity) of thin film semiconductors, which can not be performed by other techniques. 4) Development of novel approaches to determination of structural properties of thin films (porosity, surface roughness) and charge carrier densities, based on measured thermal parameters All mentioned outcomes of this project represent novel contributions to science, which stimulate further progress in the field of photothermal phenomena and techniques, as well in the field of nanostructured semiconductors for photocatalysis and photovoltaics. Relevance to the industry: New knowledge and applications of techniques and materials within this project are important for development of nanomaterials with improved properties and performance, i.e. higher photocatalytic activity and higher conversion efficiency of photovoltaic materials. In fact, important optical, thermal and structural characteristics were determined and described, which should lead to production of semiconductor nanomaterials with improved properties and to optimization and modifications of existing production technologies, which are all of great interest to manufacturers of such materials.
Significance for the country
The results of the project are expected to impact the practice of syntesis and analysis of new materials in Slovenia at international level. Apart from the cooperation with IENI-CNR and INSTM, Chemistry Depertmant, University of Padovi, Italy, that is already developed and going to be continued in the future by the way of preparation of projects application together, the cooperation with another insitutions as Institute of Physics, Technical Univeristy of Silezia, Poland is also under development. Another focus of possible applications is water purification quality and safety, as well as the usage of renewable sources of energy. Because of that, the developed method for different thin films analysis for photocatalyical applications and different polimer thin fims materials for solar cells, has an impact to the development of solar technology and technology of making new materials for the need of water purification. This is a primary priority area in EU, and is one of the more important fields in Slovenia as well. The results of the project provide very high sensitivity compared to other technques and a will expand the circle of analytical detection techniques as well as the spectrum of determining parameters and examined materials, which parameters we want to determine.
Most important scientific results
Annual report
2011,
2012,
final report,
complete report on dLib.si
Most important socioeconomically and culturally relevant results
complete report on dLib.si
