which material is most expensive in the world

 As of my last knowledge update in September 2021, one of the most expensive materials in the world is antimatter. Antimatter is composed of antiparticles (e.g., antiprotons and positrons) that have the opposite charge of regular particles. When antimatter comes into contact with matter, it annihilates, releasing a tremendous amount of energy.

The high cost of producing and containing antimatter is primarily due to the energy-intensive processes required to create and store it. Additionally, there are very limited practical applications for antimatter at this time, so its production is mostly for scientific research.

Please note that the cost of materials can change over time due to advances in technology, changes in supply and demand, and other factors. There may be new developments in material science or other materials that have become more expensive since my last update. I recommend checking the latest sources for up-to-date information on the most expensive materials as of 2023.