Projects / Programmes
Colorimetric humidity sensing material based on SiO2 mesoporous particles
| Code |
Science |
Field |
Subfield |
| 1.04.00 |
Natural sciences and mathematics |
Chemistry |
|
| Code |
Science |
Field |
| P003 |
Natural sciences and mathematics |
Chemistry |
| Code |
Science |
Field |
| 1.04 |
Natural Sciences |
Chemical sciences |
relative humidity indicator, mesoporus SiO2 nanoparticles, dye, core@shell, core-shell
Researchers (1)
| no. |
Code |
Name and surname |
Research area |
Role |
Period |
No. of publicationsNo. of publications |
| 1. |
32022 |
PhD Erika Švara Fabjan |
Chemistry |
Head |
2017 - 2019 |
0 |
Organisations (1)
Abstract
Relative humidity (RH) is one of the main factors with an important influence on thermal comfort of occupants. In order to avoid health problems it is suggested that people should adjust the RH in their indoor environments to between 40 and 60 % RH. Additionally, a high RH can accelerate the surface condensation and consequently the mould and corrosion, while a too low RH can cause the cracking and shrinking of wood and the deterioration of some other materials. For this reason continuous control and maintenance of appropriate RH in an indoor environment is desirable. RH can be monitored by an electronic device, but such a device usually only gains information about the RH in one part of room and cannot cover the distribution of RH in the specific areas, such as the corners of the rooms. An alternative option for detecting the rise of local RH on the surfaces is the colorimetric determination of humidity. But available colorimetric indicators, despite their low price and simplicity, have major problems with toxicity (e.g. CoCl2).
The main objective of the project is to develop a non-toxic colorimetric RH indicator dye@mSiO2, which will be based on a core-dye encapsulated within a mesoporous silica shell. The mesoporous silica (mSiO2) shell will be synthesised using a sol-gel reaction with the addition of the surfactants or the co-polymers, as the structure-directing agents, to obtain the desired shape and diameter of the pores. The proposed mechanism of action is based on the capillary condensation of water from humid air in the mesopores and flow into the core incorporated with the dye, which changes colour in the presence of water. The proposed mechanism is a completely new approach to the colorimetric determination of RH.
The prepared mSiO2 shell will possess cylindrical pores with a diameter between 2 and 10 nm, which correspond to condensation in the pores between 60 and 90 % RH. The new RH indicator dye@mSiO2 will be synthesized using two pathways: (1) by pre-synthesis of the mSiO2 shell (which means a mesoporous hollow nanostructure) followed by the incorporation of the dye into the hollow core and (2) by in-situ synthesis. The pre-synthesized mSiO2 (hollow structure) will be prepared using a template, which is removed at the end.
The shape, diameter distribution and orientation of the pores as well as the particle size distribution and general morphological properties of the new RH indicator dye@mSiO2will be characterized using a N2 sorption analyser, FE-SEM, TEM and DLS. The amount of bonded dye and the proposed interactions between the shell and the dye will be studied using TG/DTA, contact-angle measurements, XRD, solid-state NMR and FT-IR spectroscopy. Within the project the method will also be developed to characterize the responsiveness of the synthesized indicator to RH. The method will be based on exposure of the samples to defined stable RHs, which will be established using saturated salt solutions. The colour change will be measured by UV-Vis spectroscopy before and after exposure to define the RH, while cromometer will be used for continuously monitoring the colour change during the entire exposure.
Significance for science
We will develop new indicators to detect the relative humidity (RH) in the air. These indicators will change their colour if the RH goes above a certain threshold, thereby providing an early-warning signal. The use of dye cores coated with the mesoporous silica (dye@mSiO2) for the detection of RH represents a completely new approach to the colourimetric detection of humidity, and we anticipate that it will have a major impact on scientific research. The proposed mechanism is based on the condensation of water vapour in the mesopores and the filling of these pores with liquid water, which in turn enables a colourimetric reaction in the core. The colourimetric response of the dye@mSiO2 indicator to the specific values of the RH will be possible by tuning the pore diameter during the synthesis. The relation of the RH and the critical pore diameter, at which the condensation occurs, is described using the Kelvin equation. To the best of our knowledge, the proposed mechanism of colourimetric detection is not described in the scientific nor in the technical literature. Furthermore, facile colourimetric reporting of high RH values by the application of the proposed indicator systems on interior walls or objects has not been described in the literature. This strengthens the importance and the novelty of the results of the project, making them patentable and an interesting material for a high-impact journal. The proposed activities will also create new knowledge in the fields of chemistry, surface science, spectroscopy and optics.
Significance for the country
The main goal of the project is to develop new colourimetric indicators for relative humidity (RH). The use of new active materials in the coating, paper and building industries means new high-added-value products at a reasonable price. The integration of the proposed novel materials into products, such as coatings and impregnations, will give these products new functionalities and increase their usability. We anticipate an increase in the demand for these products among consumers. Although the proposed indicator exhibits a reversible change of colour, it is expected that with a certain modification it would also be possible to prepare indicators with an ireversible function, i.e., the change in the colour at high RH would be permanent. Such ireversible RH indicators can be redesigned and printed in the form of smart tags, which can be placed on packaging and give information about any exposure to humid conditions. This is particularly attractive for goods that are negatively affect by humid conditions.
The coating industry (specifically, the company JUB) has already expressed an interest and we have already discussed the subject of incorporating colourimetric RH indicators into their products in the future.
Most important scientific results
Interim report,
final report
Most important socioeconomically and culturally relevant results
Interim report,
final report
