Method for preparing ultrathin two-dimensional nanosheets and applications thereof

The method, comprising:

• 1) placing BiBr3 powder in a crucible, and putting the crucible on a first heating zone of a furnace disposed at a gas inlet of a quartz tube;
• placing substrates covered with copper sheets on a second heating zone of the furnace disposed at a gas outlet of the quartz tube;
• wherein a confined spacing gap between the copper sheets and the substrates is 0-100 μm;
• 2) vacuumizing the quartz tube to less than 0.1 Pa;
• pumping Ar gas into the quartz tube until an air pressure is equal to one atmosphere pressure;
• pumping mixed gas of Ar and H2 to the quartz tube and adjusting and maintaining a steady flow rate of the mixed gas;
• and
• 3) heating the second heating zone to a temperature of 275-325° C. and keeping the temperature for 10-60 min;
• heating the first heating zone to 200-275° C. for 3-20 min until producing chemical reaction between BiBr3 and metal sheets, and preparing ultrathin 2D nanosheets on the substrates simultaneously;
• and cooling the substrate naturally to 15-30° C., thereby yielding a two-dimensional ultrathin monocrystalline CuBr nanosheet.

A method, comprising:

• 1) placing BiI3 powder in a crucible, and putting the crucible on a first heating zone of a furnace disposed at a gas inlet of a quartz tube;
• placing substrates covered with naturally oxidized iron sheets on a second heating zone of the furnace disposed at a gas outlet of the quartz tube;
• 2) vacuumizing the quartz tube to less than 1 Pa;
• pumping Ar gas into the quartz tube until an air pressure is equal to one atmosphere pressure;
• continuously pumping the Ar gas to the quartz tube with a flow velocity of 10-75 sccm;
• and
• 3) heating the second heating zone to a temperature of 370-450° C. and keeping the temperature for 10-60 min;
• heating the first heating zone to 450-520° C. for 5-20 min until producing chemical reaction between BiI3 and metal sheets, and preparing ultrathin 2D nanosheets on the substrates simultaneously;
• and cooling the substrate naturally to 15-30° C., thereby yielding a two-dimensional ultrathin monocrystalline Fe3O4 nanosheet.

A method, comprising:

• 1) placing BiBr3 powder in a crucible, and putting the crucible on a first heating zone of a furnace disposed at a gas inlet of a quartz tube;
• placing substrates covered with naturally oxidized copper sheets on a second heating zone of the furnace disposed at a gas outlet of the quartz tube;
• 2) vacuumizing the quartz tube to less than 0.1 Pa;
• pumping Ar gas into the quartz tube until an air pressure is equal to one atmosphere pressure;
• continuously pumping the Ar gas to the quartz tube with a flow velocity of 25-50 sccm;
• and
• 3) heating the second heating zone to a temperature of 380-400° C. and keeping the temperature for 1-60 min;
• heating the first heating zone to 220-275° C. for 5-30 min until producing chemical reaction between BiI3 and metal sheets, and preparing ultrathin 2D nanosheets on the substrates simultaneously;
• and cooling the substrate naturally to 15-30° C., thereby yielding a two-dimensional ultrathin monocrystalline BiOBr nanosheet.