(Leader: L. F. Fonseca; Collaborators: R. Diaz, P. Feng, W. Otaño, and D. Piñero)
This IRG will develop nanomaterials that enable new, robust and stable devices that remain operational under environmental conditions with minimal power consumption for physical and chemical sensing of contaminants of environmental concern.
The primary goal is to develop sensitive, autonomous, and efficient gas sensor devices that can be used in El Yaguazo zone for the continuous monitoring of emissions from the targeted pollutant gases.
The second goal is to advance research on highly sensitive and selective multifunctional sensor devices. IRG2 proposes to focus on three different materials to achieve the main goal: metal oxides semiconductors (MOS), metal phthalocyanines (MPc), and two-dimensional (2-D) ones.
One IRG2 goal is to synthesize SnTe, Sb2Te3 and Bi2Te3 nanowires and nanoribbons with diameters (thickness) that let the surface states to play a significant role on the electrical transport in the nanowires for their potential use in chemiresistive sensors devices. To achieve that it is necessary to reduce the contribution of the bulk states.
- This requires to reduce the relative number of bulk states and/or keep the Fermi level as near as possible to the center of the bulk energy gap.
- In requirement (a) it is necessary to increase the surface to volume ratio of the material and in (b) to reduce doping during synthesis as much as possible.
Subproject 1: Novel Metal Oxide Semiconductor (MOS) Heterostructures for highly sensitive gas sensors.
MOS are widely used gas sensing materials due to their low cost, wide range of detectable gases and chemical stability at the operation conditions.
IRG2 will tailor the synthesis of new nano-composite MOS materials including (but not limited to): SnO2, ZnO, TiO2, WO3, and CuO. These materials will be prepared as nanowires, nanoshells, and nanoparticles using a combination of CVD, PVD, electrospinning and electrochemical deposition.
The proposed approaches for the formation of the composites are:
- Novel morphologies with mixed composites
- Highly porous nanowires will be prepared by co-electrodeposition in porous alumina templates of intermediaries and main materials.
- Synthesis of zinc oxide and tin dioxide nanoshells as active elements for CO and NOx detection. Zinc and Tin oxide nanoshells will be fabricated in nano and mesoscales.
For operation in high humidity conditions, promising metal oxide heterostructures will be first tested in the laboratory under gas mixtures flow with different RH percentages and the ones less affected by high RH values will be selected.
Subproject 2: Metal phthalocyanines (MPc).
The aim in this sub-project is to test MPc with different substitutions and metal centers for sensing a variety of gases.
Four different types of sensors are proposed to be tested at the Yaguazo march:
- Systems from unsubstituted MPc
- Platforms from substituted MPc with three different types of substitutions: fluorinated groups, aromatic groups and carboxylated groups
- Use of polymers to anchor the MPc on the electrodes surface
- The synthesis of MPc-MOFs using an innovative approach that incorporates as linker a metal complex in lieu of an organic bridging molecule.
We expect to yield novel 3- D units with better sensing capabilities than the mono-dimensional nanomaterials.
Subproject 3: 2D materials.
The objective is the design and fabrication of multifunctional hybrid 2D materials with enhanced selectivity and sensitivity as well as high humidity resistance for the detection of the target pollutant gases (including but not limited to) NH3, NO2, NO, and CO.
The team will conduct several tasks
- (a) Synthesis. The initial focus will be on BN. Later, the investigation will extend to MoO3 and MoS2. The goal is to control thickness, surface orientation and structure, where sensitivity highly relies on 2D material thickness whereas humidity resistance is determined by surface orientation and structure.
- (b) Surface treatment to create composite structures including catalytic nanoparticles and p-n junctions.
IRG2 Integration: Testing, Device Prototype Design, and Fabrication.
IRG2 will combine their expertise on synthesis and device fabrication techniques to develop an advanced autonomous and low power consumption device.
The prototype will be then operated in the zone of El Yaguazo marsh for field performance evaluation, feedback, and final tuning.