Platinum diselenide (PtSe2) has emerged as a promising material for gas sensing applications, particularly for detecting hazardous vapors such as acetone and ethanol. Its unique electronic properties, scalable synthesis methods, and layer-dependent behavior distinguish it from conventional metal-oxide sensors. This article examines the mechanisms behind PtSe2 gas sensing, its advantages over metal-oxide counterparts, and the practical implications of its semimetal-to-semiconductor transition.

PtSe2 belongs to the family of transition metal dichalcogenides (TMDCs), which exhibit tunable electronic properties based on their thickness. Bulk PtSe2 behaves as a semimetal with negligible bandgap, while thinning it to a few layers induces a transition to a semiconductor with a measurable bandgap. This layer-dependent electronic structure is critical for gas sensing, as the semiconducting phase offers higher sensitivity due to its surface-dominated charge transport. For instance, monolayer PtSe2 exhibits a bandgap of approximately 1.2 eV, enabling efficient adsorption and desorption of gas molecules on its surface.

The sensing mechanism of PtSe2 relies on charge transfer between the material and adsorbed gas molecules. When exposed to acetone or ethanol vapors, the molecules interact with the PtSe2 surface, altering its electrical conductivity. Acetone, an electron-withdrawing molecule, donates electrons to PtSe2, increasing its conductivity in n-type samples. Conversely, ethanol, which can act as either an electron donor or acceptor depending on the environment, induces measurable changes in resistance. Experiments have demonstrated that PtSe2 sensors exhibit response times as fast as 10 seconds for acetone detection at concentrations as low as 1 ppm, with recovery times under 30 seconds.

Scalable synthesis methods further enhance the practicality of PtSe2 gas sensors. Chemical vapor deposition (CVD) is the most widely used technique, enabling large-area growth of uniform PtSe2 films. The process typically involves selenization of pre-deposited platinum layers at temperatures between 400°C and 500°C, producing high-quality crystalline films. Alternatively, low-temperature processes below 300°C have been developed for compatibility with flexible substrates, expanding potential applications in wearable sensors. The ability to synthesize PtSe2 at wafer-scale with controlled thickness makes it suitable for industrial adoption.

In contrast to metal-oxide sensors, PtSe2 offers several advantages. Metal-oxide sensors, such as those based on tin oxide (SnO2) or tungsten oxide (WO3), require high operating temperatures (often above 200°C) to achieve sufficient sensitivity, leading to elevated power consumption and long-term stability issues. PtSe2 sensors operate effectively at room temperature, reducing energy demands and simplifying device integration. Additionally, metal-oxide sensors often suffer from poor selectivity due to broad reactivity with multiple gases, whereas PtSe2 demonstrates higher specificity toward particular volatile organic compounds (VOCs) like acetone.

The stability of PtSe2 under ambient conditions further differentiates it from other TMDCs. Unlike materials such as black phosphorus, which degrade rapidly in air, PtSe2 exhibits robust environmental stability, maintaining its performance over extended periods. This durability is attributed to its inert basal plane and resistance to oxidation, ensuring reliable operation in practical settings. Long-term testing has shown minimal degradation in sensor response after weeks of exposure to humid air.

Sensitivity and selectivity can be further optimized through defect engineering and heterostructure formation. Intentional introduction of selenium vacancies increases the density of active sites for gas adsorption, enhancing sensitivity. Hybrid structures combining PtSe2 with other 2D materials, such as graphene or hexagonal boron nitride, have also been explored to improve selectivity by tailoring interfacial charge transfer. For example, a PtSe2-graphene hybrid sensor has demonstrated a 3-fold increase in response to ethanol compared to pure PtSe2.

The following table summarizes key performance metrics of PtSe2 sensors compared to metal-oxide counterparts:

| Parameter | PtSe2 Sensor | Metal-Oxide Sensor |
|-------------------------|--------------------|--------------------|
| Operating Temperature | Room Temperature | 200-400°C |
| Response Time (Acetone) | 10-30 seconds | 30-60 seconds |
| Detection Limit | <1 ppm | 5-10 ppm |
| Power Consumption | Low | High |
| Stability | Excellent | Moderate |

Despite these advantages, challenges remain in commercializing PtSe2 gas sensors. Reproducibility of large-scale synthesis needs further refinement to ensure uniform film quality across substrates. Integration with readout electronics and wireless communication modules is another area requiring development for IoT-enabled sensor networks. Nevertheless, the progress in material synthesis and device engineering suggests a viable path toward practical deployment.

Future research directions include exploring alloying strategies to fine-tune electronic properties and investigating the role of edge sites in gas adsorption. Alloys such as PtSe2(1-x)S2x could offer additional control over bandgap and reactivity, while edge-functionalized PtSe2 may provide enhanced selectivity for specific analytes. Advances in machine learning-assisted sensor data analysis could also improve discrimination between multiple gases in complex mixtures.

In summary, PtSe2 represents a significant advancement in gas sensing technology, combining room-temperature operation, high sensitivity, and robust stability. Its layer-dependent properties and scalable synthesis position it as a strong candidate for next-generation environmental and industrial safety monitors. While metal-oxide sensors continue to dominate the market, the unique benefits of PtSe2 are likely to drive increased adoption as manufacturing techniques mature. The ongoing development of this material underscores its potential to address critical challenges in hazardous vapor detection.