a) Processing of new composites using MAPLE and PLD techniques

The results of this project have led to the development of procedures that have been verified through repeatability and validated in the laboratory to obtain composite materials in the form of thin layers, used in various applications (sensing, biology, etc.). The techniques offered as services for the processing of these composites are: pulsed laser deposition (PLD) and pulsed laser evaporation assisted by a matrix (MAPLE). A process for obtaining mesoporous crystalline layers of WO3 with a high specific surface area/volume ratio has been developed and patented (under evaluation at OSIM - A/00462/18.08.2023), which can be integrated as sensitive layers in resistive sensors for ammonia detection. The process is carried out in a single step, based on the deposition of the sensitive layer by laser ablation technique (PLD) at atmospheric pressure, concurrently with thermal treatment. Using this process, resistive sensors with improved sensitivity to ammonia are obtained. Also, a method for obtaining inorganic-organic composite layers (tungsten oxide and polypyrrole – PPy/WO3), with a porous morphology and a large specific surface area, has been developed and patented (under evaluation at OSIM - A/00510/19.09.2023), which can be used in sensing, particularly as sensitive layers in resistive sensors. The method uses a pulsed laser, with a pulse duration in the order of nanoseconds (5 - 7 ns), implementing the laser ablation technique, adapted both to the specific requirements for the deposition of ceramic materials on the one hand, and to the specific requirements for the deposition of organic materials, on the other hand. Thus, the method combines two laser ablation-based techniques, namely matrix-assisted pulsed laser evaporation (MAPLE) and pulsed laser deposition (PLD), with the aim of obtaining composite materials with a large specific surface area. The third patent application developed within this project was the creation of polymeric membranes (particularly, polypyrrole) on an ice substrate with the aim to produce "free-standing" layers. Using the patented process based on the MAPLE technique, we can obtain both simple polymeric membranes and composite membranes, with a "free-standing" character.

b) "Manufacturing" of Resistive and Electrochemical Sensors

Having experience in processing both simple and complex materials, we can also offer services related to the "manufacturing" of sensors that can detect both air contaminants (ammonia, nitrogen oxides, methane) and water contaminants (nitrites, heavy metals). Thus, we can develop both resistive sensors and electrochemical sensors. Project team members have extensive expertise in processing and characterizing such materials in the form of sensitive membranes. Consequently, some team members (Filipescu Mihaela, Dumitru Marius, Brajnicov Simona, Bercea Adrian, Palla Papavlu Alexandra) have developed a functional demonstrator not only within the laboratory but also outside it, specifically an electrochemical sensor for detecting nitrites in liquid environments (COD 23 DEM 20002, No. 8205/03.11.2023).

c) Testing Sensors for Various Contaminants

Within the group that includes our team members (http://ppam.inflpr.ro/index.html), a system for testing sensors "in house" has been developed, with which we can detect various air contaminants such as ammonia, nitrogen oxide, methane, etc. The experimental sensor testing system is mounted on a mobile stand and includes the following subsystems: i) a sensor testing chamber that includes a module for making electrical contact with the sensors; the chamber is made of stainless steel (vacuum-resistant) and is equipped with electrical pass-throughs that allow for multiple electrical connections; ii) a gas admission and control unit that contains: certified gas cylinders, a gas mixer, and flowmeters (Bronkhorst 50, 100, and 500 sccm and Alicat); iii) an SMU current/voltage source, Keithley 2612, connected to a computer via RS-232 port; iv) a computer for controlling gas flows, operating the Keithley source, and data acquisition. Electrochemical sensors can be tested using an AutoLab PGSTAT302N system controlled by NOVA 1.11 software. Nitrite detection is performed using voltammetry and amperometric techniques.