Preparation method of near-infrared silver sulfide quantum dots

Abstract

Provided is a preparation method of near-infrared silver sulfide quantum dots. The silver sulfide quantum dots have hydrophilic groups derived from a mercapto-containing hydrophilic reagent attached on the surface thereof, and the hydrophilic reagent is any one of mercaptoacetic acid, mercaptopropionic acid, cysteine, cysteamine, thioctic acid and ammonium mercaptoacetate or any combination thereof. The silver sulfide quantum dots have high fluorescence yield, good fluorescence stability, good biocompatibility and uniform sizes. The preparation method has moderate reaction conditions, simple operation, short production cycle, good reproducibility and is easy to control. The silver sulfide quantum dots can be used in the application of cellular imaging and biological tissue imaging.

Claims

1. A method for preparation of near-infrared silver sulfide quantum dots, characterized in that the method comprises the following steps: 1) preparing hydrophobic silver sulfide quantum dots; and 2) reacting the hydrophobic silver sulfide quantum dots in step 1) with stoichiometric or excessive amount of mercapto-containing hydrophilic reagent in polar organic solvent to allow the surface thereof to be attached with hydrophilic groups, so as to obtain the hydrophilic near-infrared silver sulfide quantum dots; the hydrophilic reagent is any one of mercaptopropionic acid, cysteine, cysteamine, thioctic acid and ammonium mercaptoacetate or any combination thereof; wherein the step 1) comprises the following steps: 1-1) heating a mixed reaction system containing a silver source and a long chain thiol to 80-350 C. in a closed environment, to react sufficiently; and 1-2) naturally cooling the mixed reaction system to room temperature and then adding a polar solvent, centrifuging and washing to obtain the hydrophobic near-infrared silver sulfide quantum dots; wherein the silver source comprises one or more of silver nitrate, silver diethyldithiocarbamate, silver dihydrocarbyldithiophosphate, dioctyl silver sulfosuccinate, silver thiobenzoate, silver acetate, silver dodecanoate, silver tetradecanoate and silver octadecanoate; the long chain thiol comprises one or more of octanethiol, undecanethiol, dodecanethiol, tridecanethiol, tetradecanethiol, pentadecanethiol, hexadecanethiol, octadecanethiol, eicosanethiol, hexanethiol, 1,6-hexanedithiol, and 1,8-octanedithiol; wherein in step 2), the hydrophobic silver sulfide quantum dots are reacted with the mercapto-containing hydrophilic reagent in the polar organic solvent at 2-80 C. for 3 or more hours; and wherein in step 1-2), the mixed reaction system further comprises a surfactant having coordination property, selected from the group consisted of a long chain alkyl acid, alkylamine, a long chain alcohol, and ether or any combination thereof, the mixed reaction system is placed in a closed environment to react.

2. The method for preparation of near-infrared silver sulfide quantum dots according to claim 1, characterized in that in step 2), the pH value of the reaction system is adjusted to 7-14.

3. The method for preparation of near-infrared silver sulfide quantum dots according to claim 1, characterized in that in step 2), the polar organic solvent comprises any one or more of ethanol, methanol, acetone and 1-methyl-2-pyrrolidone.

4. The method for preparation of near-infrared silver sulfide quantum dots according to claim 1, characterized in that in step 2), the hydrophobic silver sulfide quantum dots are reacted with the mercapto-containing hydrophilic reagent under the condition of continuous stirring and/or vibrating and/or sonicating in the polar organic solvent at 2-80 C. for 3 or more hours.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is the TEM image of the hydrophobic Ag.sub.2S quantum dots in Example 1;

(2) FIG. 2 is the near-infrared fluorescence spectrum of the hydrophobic Ag.sub.2S quantum dots in Example 1;

(3) FIG. 3 is the near-infrared fluorescence spectrum of the hydrophilic Ag.sub.2S quantum dots in Example 1;

(4) FIG. 4 is the fluorescence photograph of cells specifically labeled with the near-infrared quantum dots of silver sulfide in Example 1; and

(5) FIG. 5 is the fluorescence photograph of the tumor in a living mouse specifically labeled with the near-infrared quantum dots of silver sulfide.

DESCRIPTION OF EMBODIMENTS

(6) The preparation process of the invention is explained in detail by the specific examples below.

EXAMPLE 1

(7) 0.1 mmol of silver diethyldithiocarbamate and 10 g of dodecanethiol were mixed in a flask, and heated to 200 C. under a N.sub.2 atmosphere for 1 h. 50 mL of anhydrous ethanol was added to the solution after the solution was cooled naturally to room temperature, and then the resultant mixture was centrifuged, washed and dispersed in cyclohexane. The sample obtained was identified to be monoclinic Ag.sub.2S quantum dots by X ray diffraction and transmission electron microscopy (the particle size thereof is about 5 nm, as shown in FIG. 1), which has a good near-infrared fluorescence emission spectrum, as shown in FIG. 2. 0.15 g of thioctic acid was added to the above cyclohexane dispersion, and equal volume of anhydrous ethanol was added, then the resultant mixture was sonicated in an ultrasonic cleaner for 4 h, centrifuged and washed with deionized water to obtain water-soluble Ag.sub.2S quantum dots with particle sizes of about 5 nm which still have very strong fluorescence emission, as shown in FIG. 3. 0.25 mg of the above Ag.sub.2S quantum dots were dispersed in 100 L of dimethyl sulfoxide (DMSO), and 50 L of DMSO solution containing 0.01 mmol of NHS was mixed with the above solution. Then 50 L of DMSO solution containing 0.01 mmol of EDC was added to the above mixed solution, and the resultant mixture was packed with aluminum foil, stirred for 1 h, centrifuged and further dispersed in 100 L, of DMSO. The mixed solution of 15 L of 2 mg/mL Erbitux and 185 L of 1 PBS was added to 100 L of Ag.sub.2S/DMSO mixed solution, and the resultant mixture was reacted in darkness at 4 C. for 12 h, then centrifuged at 400 g for 4 min, and then the supernatant was taken. MDA-MB-468 cells were added to the mixed solution of 100 L of the above supernatant and 100 L of 1 PBS, coloured at 4 C. for 2 h, and then washed 3 times with 1 PBS solution. It can clearly be seen that the luminescence was given by Ag.sub.2S quantum dots in cells by exciting with 658 nm laser, using 1100 nm filter, and photographing with a 2D InGaAs camera (see FIG. 4).

EXAMPLE 2

(8) 0.1 mmol of silver nitrate, 8 g of dodecanethiol and 5.4 g of oleylamine were mixed in a three-necked flask, and heated to 180 C. under air for 1 h. After the solution was cooled naturally to room temperature, 50 mL of anhydrous ethanol was added. The resultant mixture was centrifuged, washed and dispersed in cyclohexane. The sample obtained was identified to be monoclinic Ag.sub.2S quantum dots by X ray diffraction and transmission electron microscopy, with the particle size below 8 nm, which has a good near-infrared fluorescence emission spectrum. 0.2 g of L-cysteine was added to the above cyclohexane dispersion, then equal volume of anhydrous ethanol was added. The resultant mixture was stirred for 24 h, then centrifuged and washed with deionized water to obtain water-soluble Ag.sub.2S quantum dots with particle sizes of about 8 nm, which still have very strong fluorescence emission. 0.25 mg of the above Ag.sub.2S quantum dots was dispersed in 100 L of dimethyl sulfoxide (DMSO), and 50 L of DMSO solution containing 0.01 mmol of NHS was mixed with the above solution. Then 50 L of DMSO solution containing 0.01 mmol of EDC was added to the above mixed solution. The resultant mixture was packed with aluminum foil, stirred for 1 h, centrifuged and further dispersed in 100 L of DMSO. The mixed solution of 15 L of 2 mg/mL Erbitux and 185 L of 1 PBS was added to 100 L of Ag.sub.2S/DMSO mixed solution. The resultant mixture was reacted in darkness at 4 C. for 12 h, then centrifuged at 400 g for 4 min, and the supernatant was taken. MDA-MB-468 cells were added to the mixed solution of 100 L of the above supernatant and 100 L of 1 PBS, coloured at 4 C. for 2 h, and then washed 3 times with 1 PBS solution. It can clearly be seen that the luminescence was given by Ag.sub.2S quantum dots in cells by exciting with 658 nm laser, using 1100 nm filter, and photographing with a 2D InGaAs camera.

EXAMPLE 3

(9) 0.1 mmol of silver thiobenzoate, 8 g of hexadecanethiol and 2 g of trioctylphosphine oxide were mixed in a three-necked flask, heated to 160 C. under air for 4 h. After the solution was cooled naturally to room temperature, 50 mL of anhydrous ethanol was added. The resultant mixture was centrifuged, washed and dispersed in cyclohexane. 0.1 g of mercaptopropionic acid was added to the above cyclohexane dispersion, then equal volume of anhydrous ethanol was added. The resultant mixture was vibrated in a vibrator for 8 h, centrifuged and washed with deionized water to obtain water-soluble Ag.sub.2S quantum dots with a particle size of about 6 nm, which still have very strong fluorescence emission. 0.25 mg of the above Ag.sub.2S quantum dots was dispersed in 100 L of dimethyl sulfoxide (DMSO), and 50 L of DMSO solution containing 0.01 mmol of NHS was mixed with the above solution. Then 50 L of DMSO solution containing 0.01 mmol of EDC was added to the above mixed solution. The resultant mixture was packed with aluminum foil, stirred for 1 h, centrifuged and further dispersed in 100 L of DMSO. The mixed solution of 15 L of 2 mg/mL Erbitux and 185 L of 1 PBS was added to 100 L of Ag.sub.2S/DMSO mixed solution. The resultant mixture was reacted in darkness at 4 C. for 12 h, then centrifuged at 400 g for 4 min, and then the supernatant was taken. MDA-MB-468 cells were added to the mixed solution of 100 L of the above supernatant and 100 L of 1 PBS, coloured at 4 C. for 2 h, and then washed 3 times with 1 PBS solution. It can clearly be seen that the luminescence was given by Ag.sub.2S quantum dots in cells by exciting with 658 nm laser, using 1100 nm filter, and photographing with a 2D InGaAs camera.

EXAMPLE 4

(10) 0.1 mmol of silver hexadecanoate, 5 g of hexadecanethiol and 4 g of octadecylamine were mixed in a three-necked flask and heated to 200 C. under an Ar atmosphere for 1 h. After the solution was cooled naturally to room temperature, 50 mL of anhydrous ethanol was added. The resultant mixture was centrifuged, washed and dispersed in cyclohexane. 0.12 g of mercaptoacetic acid was added to the above cyclohexane dispersion, then equal volume of anhydrous ethanol was added. The resultant mixture was stirred for 24 h, then centrifuged and washed with deionized water to obtain water-soluble Ag.sub.2S quantum dots with a particle size of about 6 nm, which still have very strong fluorescence emission. 0.25 mg of the above Ag.sub.2S quantum dots was dispersed in 100 L of dimethyl sulfoxide (DMSO), and 50 L of DMSO solution containing 0.01 mmol of NHS was mixed with the above solution. Then 50 L of DMSO solution containing 0.01 mmol of EDC was added to the above mixed solution. The resultant mixture was packed with aluminum foil, stirred for 1 h, centrifuged and further dispersed in 100 L of DMSO. The mixed solution of 15 L of 2 mg/mL Erbitux and 185 L of 1 PBS was added to 100 L of Ag.sub.2S/DMSO mixed solution and the resultant mixture was reacted in darkness at 4 C. for 12 h, then centrifuged at 400 g for 4 min, and then the supernatant was taken. MDA-MB-468 cells were added to the mixed solution of 100 L of the above supernatant and 100 L of 1 PBS, coloured at 4 C. for 2 h, and then washed 3 times with 1 PBS solution. It can clearly be seen that the luminescence was given by Ag.sub.2S quantum dots in cells by exciting with 658 nm laser, using 1100 nm filter, and photographing with a 2D InGaAs camera.

EXAMPLE 5

(11) 0.1 mmol of silver dihydrocarbyldithiophosphate, 10 g eicosanethiol and 4 g of hexadecylamine were mixed in a three-necked flask and heated to 230 C. under an Ar atmosphere for 0.5 h. After the solution was cooled naturally to room temperature, 50 mL of anhydrous ethanol was added. The resultant mixture was centrifuged, washed and dispersed in cyclohexane. 0.1 g of cysteamine was added to the above cyclohexane dispersion, then equal volume of anhydrous ethanol was added. The resultant mixture was stirred for 24 h, then centrifuged and washed with deionized water to obtain water-soluble Ag.sub.2S quantum dots with a particle size of about 5 nm, which still have very strong fluorescence emission. 0.25 mg of the above Ag.sub.2S quantum dots was dispersed in 100 L of dimethyl sulfoxide (DMSO), and 50 L of DMSO solution containing 0.01 mmol of NHS was mixed with the above solution. Then 50 L of DMSO solution containing 0.01 mmol of EDC was added to the above mixed solution. The resultant mixture was packed with aluminum foil, stirred for 1 h, centrifuged and further dispersed in 100 L of DMSO. The mixed solution of 15 L of 2 mg/mL Erbitux and 185 L of 1 PBS was added to 100 L of Ag.sub.2S/DMSO mixed solution, and the resultant mixture was reacted in darkness at 4 C. for 12 h, then centrifuged at 400 g for 4 min, and the supernatant was taken. MDA-MB-468 cells were added to the mixed solution of 100 L of the above supernatant and 100 L of 1 PBS, coloured at 4 C. for 2 h, and then washed 3 times with 1 PBS solution. It can clearly be seen that the luminescence was given by Ag.sub.2S quantum dots in cells by exciting with 658 nm laser, using 1100 nm filter, and photographing with a 2D InGaAs camera.

EXAMPLE 6

(12) 0.1 mmol of silver dodecanoate, 8 g of octanethiol and 4 g of dodecylamine were mixed in a three-necked flask and heated to 200 C. under an Ar atmosphere for 0.5 h. After the solution was cooled naturally to room temperature, 50 mL of anhydrous ethanol was added. The resultant mixture was centrifuged, washed and dispersed in cyclohexane. 0.12 g of mercaptoacetic acid was added to the above cyclohexane, then equal volume of anhydrous ethanol was added, stirred for 24 h, then the resultant mixture was centrifuged and washed with deionized water to obtain water-soluble Ag.sub.2S quantum dots with a particle size of about 5 nm, which still have very strong fluorescence emission. 0.25 mg of the above Ag.sub.2S quantum dots was dispersed in 100 L of dimethyl sulfoxide (DMSO), and 50 L of DMSO solution containing 0.01 mmol of NHS was mixed with the above solution. Then 50 L of DMSO solution containing 0.01 mmol of EDC was added to the above mixed solution, and the resultant mixture was packed with aluminum foil, stirred for 1 h, centrifuged and further dispersed in 100 L of DMSO. The mixed solution of 15 L of 2 mg/mL Erbitux and 185 L of 1 PBS was added to 100 L of Ag.sub.2S/DMSO mixed solution, and the resultant mixture was reacted in darkness at 4 C. for 12 h, and then centrifuged at 400 g for 4 min, and the supernatant was taken. MDA-MB-468 cells were added to the mixed solution of 100 L of the above supernatant and 100 L of 1 PBS, coloured at 4 C. for 2 h, and then washed 3 times with 1 PBS solution. It can clearly be seen that the luminescence was given by Ag2S quantum dots in cells by exciting with 658 nm laser, using 1100 nm filter, and photographing with a 2D InGaAs camera.

(13) In conclusion, the method of the invention has moderate reaction conditions, simple operation, short production cycle, good reproducibility, and is easy to control. The as-prepared Ag.sub.2S quantum dots have high fluorescence yield, good fluorescence stability, excellent biocompatibility and homogeneous sizes, and can well be used for cellular imaging and in vivo animal tissue imaging. Furthermore, the method of the present invention is easy to be implemented in large scale, thus is applicable for the industrial production.

(14) The above examples are only the representative ones of numerous examples of the invention, and do not limit the protection scope of the invention at all. All the technical solutions having the equivalent variations or equivalent substitutions fall within the protection scope of the invention.