# US 12,600,630 B1 · Method of synthesizing carbon quantum dots

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- Number: US 12,600,630 B1
- Document ID: US12600630B1
- Status: Granted
- Kind: B1
- Application number: 19/359,296
- Filed: 2025-10-15
- Granted: 2026-04-14
- Earliest claimed: 2025-10-15
- Assignees: King Fahd University of Petroleum and Minerals
- Applicants: King Fahd University of Petroleum and Minerals
- Inventors: Billel Salhi; Mazen Khaled Nazal; Amir Al-Ahmed; Ismail Abdulazeez
- Web page: https://patentgrep.com/patent/US12600630B1

## CPC

- C01B 32/15: Nano-sized carbon materials
- B01D 61/243: {Dialysis}
- B01D 69/02: characterised by their properties
- C09K 11/65: containing carbon (in organic compounds C09K11/06)
- B01D 2325/02834: more than 0.1 and up to 1 µm
- B82Y 20/00: Nanooptics, e.g. quantum optics or photonic crystals
- B82Y 40/00: Manufacture or treatment of nanostructures
- C01P 2002/84: by UV- or VIS- data
- C01P 2004/04: obtained by TEM, STEM, STM or AFM
- C01P 2004/32: Spheres
- C01P 2004/64: Nanometer sized, i.e. from 1-100 nanometer
- C01P 2006/60: Optical properties, e.g. expressed in CIELAB-values
- C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C}
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS

## Abstract

A method of synthesizing carbon quantum dots (CQDs) includes using a dried ground Halodule uninervis seagrass to form a suspension in water, followed by centrifuging and filtering through a filter membrane and a dialysis membrane to form a CQDs solution. The CQDs have a Stokes shift of less than 83.0 nm at an excitation wavelength of 380 to 430 nm.

## Claims

### Claim 1

A method of synthesizing carbon quantum dots (CQDs), comprising:
grinding a dry Halodule uninervis seagrass to form a seagrass powder;
heating a mixture comprising water and the seagrass powder to form a suspension;
centrifuging the suspension to obtain a supernatant;
filtering the supernatant through a filter membrane and a dialysis membrane to form a CQDs solution comprising a plurality of CQDs,
wherein the carbon quantum dots have a Stokes shift of less than 83.0 nm at an excitation wavelength of 380 to 430 nm.

### Claim 2 (depends on 1)

The method of claim 1, wherein the Halodule uninervis seagrass is obtained from the Red Sea and washed to remove water soluble impurities from the sea.

### Claim 3 (depends on 1)

The method of claim 1, wherein the mixture comprises the seagrass powder at a percentage of 1 to 10 wt./vol. % based on a total weight of the seagrass powder and a total volume of water.

### Claim 4 (depends on 1)

The method of claim 1, wherein the heating is performed in an autoclave at a temperature of 150 to 250 degrees Celsius (° C.).

### Claim 5 (depends on 1)

The method of claim 1, wherein the centrifuging is performed under at least 12,000 rpm.

### Claim 6 (depends on 1)

The method of claim 1, wherein the filtration membrane comprises a plurality of pores having an average size of 0.2 to 0.3 micrometers (μm).

### Claim 7 (depends on 1)

The method of claim 1, wherein the CQDs have a photoluminescence signal at 390 to 410 nm wavelength range at an excitation wavelength of 350 to 450 nm.

### Claim 8 (depends on 1)

The method of claim 1, wherein the CQDs have a light absorption comprising a first peak, a second peak, and a third peak.

### Claim 9 (depends on 8)

The method of claim 8, wherein the first peak is at 200 to 250 nm.

### Claim 10 (depends on 8)

The method of claim 8, wherein the second peak is at 250 to 300 nm.

### Claim 11 (depends on 8)

The method of claim 8, wherein the third peak is at 300 to 350 nm.

### Claim 12 (depends on 1)

The method of claim 1, wherein the CQDs have an optical band gap energy of 3 to 4 eV.

### Claim 13 (depends on 1)

The method of claim 1, wherein the CQDs are in the form of spherical particles having a size of 4 to 11 nm.

### Claim 14 (depends on 1)

The method of claim 1, wherein the CQDs have a Stokes shift of 80 to 82 nm at an excitation wavelength of 380 to 430 nm and an emission wavelength of 460 to 490 nm.

### Claim 15 (depends on 1)

The method of claim 1, wherein the CQDs have a Stokes shift of 80 to 83 nm at an excitation wavelength of 420 to 430 nm and an emission wavelength of 500 to 510 nm.