Opportunity
Transition metal dichalcogenides (TMDs) like MoS₂, WS₂, MoSe₂, and WSe₂ are widely studied for their unique properties in catalysis, electronics, and biomedicine. However, conventional TMDs predominantly exist in the thermodynamically stable 2H phase, which is semiconducting. The metastable 1T’ phase, with metallic/semi-metallic properties, offers superior performance in applications such as electrocatalysis and surface-enhanced Raman scattering (SERS). Despite its potential, synthesizing high-purity, single-layer 1T’-TMDs remains challenging due to their high formation energy and van der Waals forces between layers. Existing methods, such as chemical vapor deposition (CVD) or alkali metal intercalation, often yield impure products or unstable phases that revert to the 2H structure under ambient conditions. This patent addresses the need for a scalable, low-temperature wet-chemical method to produce phase-pure 1T’-TMD monolayers with enhanced stability and performance.
Technology
The invention introduces a rapid, low-temperature (250–350°C) wet-chemical synthesis method to grow 1T’-TMD monolayers (e.g., WS₂, WSe₂, MoS₂, MoSe₂) with high phase purity. Key innovations include:
1. Precursor Mixing: A transition metal precursor (e.g., ammonium tungstate or molybdate) is dissolved in oleylamine (first solvent), while a chalcogen (e.g., sulfur or selenium) is mixed with octadecylamine/octadecene (second solvent). The rapid injection of the first mixture into the second at high temperature ensures controlled nucleation.
2. Substrate Engineering: Metallic substrates like 4H-phase gold nanowires (4H-Au NWs) are used to stabilize the 1T’ phase via strong covalent Au–S/Se interfacial interactions, preventing phase reversion to 2H.
3. Phase Purity: The method yields monolayers with near-100% 1T’ phase purity, confirmed by HAADF-STEM, XPS, and Raman spectroscopy.
Advantages
- High Phase Purity: Produces 1T’-TMD monolayers without 2H-phase impurities.
- Stability: Covalent bonding with metal substrates (e.g., 4H-Au) prevents phase degradation.
- Scalability: Wet-chemical synthesis is cost-effective and suitable for large-scale production.
- Versatility: Applicable to various TMDs (WS₂, WSe₂, MoS₂, MoSe₂) and metal substrates (Au, Ag, Pd).
Applications
- SERS Substrates: Ultrasensitive detection of molecules (e.g., attomolar-level SARS-CoV-2 spike protein).
- Electrocatalysis: Enhanced hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR).
- Flexible Electronics: Transparent conductive films for wearable devices.
- Biomedicine: Real-time monitoring of biomarkers or pathogens.
