JP2019199555A - Composite fluorescent gold nanocluster having high quantum yield and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite fluorescent gold nanocluster having a high quantum yield, and a method for manufacturing the same. A composite fluorescent gold nanocluster (100) including a gold nanocluster (110) and a capping layer (120) encapsulating at least a part of an outer surface of the gold nanocluster. The capping layer includes a matrix 122 made of a benzene-based compound and a plurality of phosphine-based compounds 124 dispersed in the matrix. [Selection diagram] Figure 1

Description

  The present disclosure relates to composite fluorescent gold nanoclusters, and more specifically to composite fluorescent gold nanoclusters having high quantum yields.

  With rapid advances in nanotechnology, many nanomaterials (eg, fluorescent probes) are now being used for cell tracking, molecular imaging, and / or tumor targeting and diagnosis. Conventionally, an organic dye capable of emitting various colors is a preferable compound as a fluorescent probe because it has excellent water solubility and high salt tolerance. However, these organic dyes fade easily and their quantum yield is often too low for widespread use.

  Quantum dots (QDs) provide an alternative to organic dyes, and the color of the emitted light can be easily adjusted by changing the size of the QDs. In addition, by using only one light source, the QD can be excited to emit various colors. Most importantly, the QD does not suffer from the photobleaching penalty. Further, the surface of the QD can be modified so that a desired functional compound is grafted thereon. Therefore, QD is widely used in the biomedical field. However, because QD is made of heavy metals, it is considered not environmentally friendly and may be harmful to living organisms.

  Another option is to use fluorescent metal nanoclusters made from noble metals such as gold, silver, copper, platinum, palladium, etc. Noble metal nanoclusters generally consist of a few to a few tens of atoms and are typically less than 2 nanometers in size. Precious metal nanoclusters are located between bulk metals and individual atoms (and nanoparticles) in terms of electronic, optical, and chemical properties. Currently, noble metal nanoclusters with full emission spectra have been developed and used for biological analysis (eg, biomarkers). The emission spectrum (from ultraviolet to infrared) may be adjusted by changing the preparation parameters. As noble metal nanoclusters are biocompatible, they have attracted much attention in research and development. Various types of methods for the synthesis of noble metal nanoclusters have been reported, such as chemical reduction, photoreduction, chemical etching, microwave assisted methods, and phase transfer methods.

  Since bare noble metal nanoclusters are often poor in stability, additional surface ligands and stabilizers are required to prevent nanocluster aggregation. However, these surface ligands and stabilizers can have biological toxicity.

  In view of the foregoing, there is a need in the related art for improved noble metal nanoclusters and methods for preparing the same, and such improved noble metal nanoclusters are at least some of the problems that exist in the art. Can deal with crab.

  The following provides a brief overview of the present disclosure to provide a basic understanding to the reader. This summary is not an extensive overview of the disclosure and it does not identify key / critical elements of the invention or delineate the scope of the invention. Its sole purpose is to provide some concepts disclosed herein in a simplified form as a prelude to the more detailed description that is presented later.

  In one aspect, the present disclosure is directed to composite fluorescent gold nanoclusters. According to various embodiments of the present disclosure, the composite fluorescent gold nanocluster includes a gold nanocluster and a capping layer that encapsulates at least a portion of the outer surface of the gold nanocluster. The capping layer includes a matrix made of a benzene based compound and a plurality of phosphine based compounds dispersed in the matrix.

  According to embodiments of the present disclosure, the benzene-based compound is of benzene, alkylbenzene, halobenzene, phenol, benzoic acid, acetophenone, methyl benzoate, anisole, aniline, nitrobenzene, benzonitrile, benzamide, benzenesulfonic acid, naphthalene, or anthracene. Either may be sufficient. For example, the alkylbenzene is toluene, cumene, ethylbenzene, styrene, or xylene, and the halobenzene is fluorobenzene, chlorobenzene, bromobenzene, or iodobenzene. According to certain examples of the present disclosure, the benzene-based compound is toluene.

  According to embodiments of the present disclosure, phosphine-based compounds are phosphine, phosphine oxide, phosphonium, diphosphine, triphosphine, alkylphosphine, cycloalkylphosphine, arylphosphine, arylphosphine oxide, bidentate phosphine, phosphine silicone derivatives, phosphine derivatives. Either a siloxane or polysilane derivative, and an olefin phosphine. In some embodiments, the phosphine-based compound is an alkyl phosphine, such as trioctylphosphine (TOP). In other embodiments, the phosphine-based compound is an aryl phosphine oxide, such as trioctylphosphine oxide (TOPO).

  In some embodiments, the peak emission of the composite fluorescent gold nanocluster is from about 500 nm to about 580 nm.

In another aspect, the present disclosure is directed to a method for generating composite fluorescent gold nanoclusters. According to an embodiment of the present disclosure, the method comprises mixing (a) gold (III) chloride (AuCl ₃ ) and a benzene-based compound in a molar ratio of 1: 0.5 to 1: 5. Generating a gold nanocluster; and (b) treating the first fluorescent gold nanocluster with an energy source selected from the group consisting of UV, sonic, heat, microwave, and combinations thereof; Generating a fluorescent gold nanocluster; and (c) modifying the second fluorescent gold nanocluster of step (b) with a phosphine-based compound to generate the composite fluorescent gold nanocluster of claim 1. Including, this method is characterized in that any reducing agent is not used.

  According to various embodiments of the present disclosure, in step (a), gold (III) chloride and a benzene-based compound are mixed in a molar ratio of 1: 0.3 to 1: 2.5.

  According to embodiments of the present disclosure, the benzene-based compound is of benzene, alkylbenzene, halobenzene, phenol, benzoic acid, acetophenone, methyl benzoate, anisole, aniline, nitrobenzene, benzonitrile, benzamide, benzenesulfonic acid, naphthalene, or anthracene. Either may be sufficient. For example, the alkylbenzene is toluene, cumene, ethylbenzene, styrene, or xylene, and the halobenzene is fluorobenzene, chlorobenzene, bromobenzene, or iodobenzene. According to certain examples of the present disclosure, the benzene-based compound is toluene.

  According to embodiments of the present disclosure, phosphine-based compounds are phosphine, phosphine oxide, phosphonium, diphosphine, triphosphine, alkylphosphine, cycloalkylphosphine, arylphosphine, arylphosphine oxide, bidentate phosphine, phosphine silicone derivatives, phosphine derivatives. Either a siloxane or polysilane derivative, and an olefin phosphine. In some embodiments, the phosphine-based compound is an alkyl phosphine, such as trioctyl phosphine (TOP). In other examples, the phosphine-based compound is an aryl phosphine oxide, such as trioctyl phosphine oxide (TOPO).

  According to embodiments of the present disclosure, the first and second fluorescent gold nanoclusters emit blue and yellow light, respectively, and the composite fluorescent gold nanocluster has a yellow or green color with a peak emission wavelength in the range of 500 nm to 580 nm. Emits light.

According to an alternative embodiment of the present disclosure, the composite fluorescent gold nanocluster comprises (a) gold (III) chloride (AuCl ₃ ), a benzene-based compound, and a phosphine-based compound at 1: 0.5: 0. Mixing at a molar ratio of 1 to 1: 5: 20 to produce a third fluorescent gold nanocluster; and (b) selected from the group consisting of UV, sonic, thermal, microwave, and combinations thereof Treating the third fluorescent gold nanocluster with an energy source to produce a composite fluorescent gold nanocluster, wherein the method is characterized in that it does not use any reducing agent. .

  According to embodiments of the present disclosure, the benzene-based compound is of benzene, alkylbenzene, halobenzene, phenol, benzoic acid, acetophenone, methyl benzoate, anisole, aniline, nitrobenzene, benzonitrile, benzamide, benzenesulfonic acid, naphthalene, or anthracene. Either may be sufficient. For example, the alkylbenzene is toluene, cumene, ethylbenzene, styrene, or xylene, and the halobenzene is fluorobenzene, chlorobenzene, bromobenzene, or iodobenzene. According to certain examples of the present disclosure, the benzene-based compound is toluene.

  According to embodiments of the present disclosure, phosphine-based compounds are phosphine, phosphine oxide, phosphonium, diphosphine, triphosphine, alkylphosphine, cycloalkylphosphine, arylphosphine, arylphosphine oxide, bidentate phosphine, phosphine silicone derivatives, phosphine derivatives. Either a siloxane or polysilane derivative, and an olefin phosphine. In some embodiments, the phosphine-based compound is an alkyl phosphine, such as trioctyl phosphine (TOP). In other examples, the phosphine-based compound is an aryl phosphine oxide, such as trioctyl phosphine oxide (TOPO).

  According to embodiments of the present disclosure, the composite fluorescent gold nanocluster emits yellow or green light having a peak emission wavelength in the range of 500 nm to 580 nm.

  Many of the features and advantages associated with the present disclosure may be better understood with reference to the following detailed description considered in conjunction with the accompanying drawings.

  The present description will be better understood by reading the following detailed description in light of the accompanying drawings, in which:

1 is a schematic diagram illustrating a fluorescent gold nanocluster according to an embodiment of the present disclosure. FIG. FIG. 3 shows a ¹ H-NMR spectrum of a fluorescent gold nanocluster according to an example of the present disclosure. FIG. 3 shows a ¹ H-NMR spectrum of a fluorescent gold nanocluster according to an example of the present disclosure. FIG. 3 shows a representative photograph of a fluorescent gold nanocluster according to one embodiment of the present disclosure. It is a diagram showing ¹ H-NMR spectrum of the fluorescent gold nanoclusters Figure 3A. FIG. 3 provides a representative photograph and fluorescence spectrum of a fluorescent gold nanocluster according to one embodiment of the present disclosure. FIG. 3 provides a representative fluorescence spectrum of a fluorescent gold nanocluster according to one embodiment of the present disclosure. FIG. 3 provides a representative fluorescence spectrum of a fluorescent gold nanocluster according to one embodiment of the present disclosure. It is a figure which shows the field emission gun transmission electron microscope image of the fluorescent gold nanocluster according to one Example of this indication. FIG. 2 shows a representative photograph and fluorescence spectrum of a fluorescent gold nanocluster according to one embodiment of the present disclosure. FIG. 2 shows a representative photograph and fluorescence spectrum of a fluorescent gold nanocluster according to one embodiment of the present disclosure. It is a figure which shows the field emission gun transmission electron microscope image of the fluorescent gold nanocluster according to one Example of this indication. It is a figure which shows the field emission gun transmission electron microscope image of the fluorescent gold nanocluster according to one Example of this indication. FIG. 3 is a diagram illustrating a representative fluorescence spectrum of a fluorescent gold nanocluster according to one embodiment of the present disclosure. FIG. 3 is a diagram illustrating a representative fluorescence spectrum of a fluorescent gold nanocluster according to one embodiment of the present disclosure. FIG. 2 shows a representative photograph and fluorescence spectrum of a fluorescent gold nanocluster according to one embodiment of the present disclosure. FIG. 2 shows a representative photograph and fluorescence spectrum of a fluorescent gold nanocluster according to one embodiment of the present disclosure. FIG. 3 is a diagram illustrating a fluorescence spectrum of a fluorescent gold nanocluster according to an embodiment of the present disclosure. FIG. 3 is a diagram illustrating a fluorescence spectrum of a fluorescent gold nanocluster according to an embodiment of the present disclosure. FIG. 3 is a diagram illustrating a fluorescence spectrum of a fluorescent gold nanocluster according to an embodiment of the present disclosure. FIG. 3 is a diagram illustrating a fluorescence spectrum of a fluorescent gold nanocluster according to an embodiment of the present disclosure. FIG. 3 is a diagram illustrating a fluorescence spectrum of a fluorescent gold nanocluster according to an embodiment of the present disclosure. FIG. 3 is a diagram illustrating a fluorescence spectrum of a fluorescent gold nanocluster according to an embodiment of the present disclosure.

  In accordance with common practice, the various described features / components are not drawn to scale but are drawn to best illustrate certain features / components related to the present invention.

  The detailed description provided below in connection with the accompanying drawings is intended as a description of the present embodiments and is not intended to represent the only forms in which the embodiments may be constructed or used. . This description illustrates the functionality of the example and the order of steps for constructing and operating the example. However, the same or equivalent functions and sequences may be achieved by different embodiments.

  For convenience, certain terms employed in the specification, examples, and appended claims are collected here. Unless otherwise defined herein, scientific and technical terms used in this disclosure have the meanings that are commonly understood and used by those of ordinary skill in the art.

  It will be understood that singular terms include the plural of the same and plural terms include the singular unless the context requires otherwise. In addition, the terms “at least one” and “one or more” as used herein and in the claims have the same meaning and include 1, 2, 3, or more. Further, as used throughout this specification and the appended claims, “at least one of A, B, and C”, “at least one of A, B, or C”, and “of A, B, and / or C” The phrase “at least one” is intended to encompass A alone, B alone, C alone, both A and B, both B and C, both A and C, and all of A, B, and C. Is done.

  Although the numerical ranges and parameters indicating the broad scope of the present invention are approximate, the numerical values shown in the specific examples are reported as accurately as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. In addition, the term “about” as used herein generally means within 10%, 5%, 1%, or 0.5% of a given value or range. Alternatively, the term “about” means within an acceptable standard error of the average value as considered by one of ordinary skill in the art. All disclosed herein, for example, amounts of materials, durations, temperatures, operating conditions, ratios of amounts, and the like, unless otherwise specified otherwise than in operation / working examples The numerical ranges, amounts, values and percentages of should be understood to be modified by the term “about” in all cases.

  As used herein, the term “nanocluster” refers to a bond of several to tens of atoms of a metal (eg, gold, etc.). Nanoclusters may have a diameter in the range of about 0.1 nm to about 3 nm.

  As used herein, the term “fluorescence” or “fluorescent” refers to a physical phenomenon based on the ability of a particular compound to absorb and emit light of different wavelengths. After absorption of light (photons) at the first wavelength, photons at the second wavelength and emission of different energies occur. As used herein, the term “red shift” indicates that the point of maximum amplitude of one or more peaks of the fluorescence emission profile shifts to a longer wavelength. Although named “red”, redshifts can occur in any part of the electromagnetic spectrum. The term “quantum yield” here refers to the efficiency of converting photons absorbed by the fluorescent gold nanoclusters into fluorescence.

  The present invention is based at least in part on the discovery that modifying the surface of a nanocluster core with functional groups such as phenyl and phosphine improves the fluorescent characteristics (eg, tunability and quantum yield) of the nanocluster. It is.

  Reference is made to FIG. 1, which is a schematic diagram illustrating a composite fluorescent gold nanocluster 100 according to one embodiment of the present disclosure. As shown, the composite fluorescent gold nanocluster 100 includes a gold nanocluster 110 and a capping layer 120.

  Specifically, the gold nanocluster 110 is an aggregate of gold atoms 110 ′. As can be appreciated, although a specific number of gold atoms 110 'is shown in FIG. 1, embodiments of the present invention are not so limited. Gold nanocluster 110 may include any suitable number of gold atoms 110 'ranging from a few to a few tens. Preferably, the gold nanoclusters described herein are 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, Contains 45, 46, 47, 48, 49, or 50 atoms. In other preferred embodiments, the gold nanocluster comprises 2 to 30 atoms, 5 to 25 atoms, 5 to 20 atoms, or 5 to 15 atoms. In general, the diameter of the gold nanocluster 110 is from about 0.1 nm to about 3 nm, preferably less than about 2 nm.

  The capping layer 120 includes a matrix 122 made of a benzene-based compound and a plurality of phosphine-based compounds 124 dispersed in the matrix 122. As shown in FIG. 1, the capping layer 120 encapsulates the entire gold nanocluster 110, but in other alternative embodiments, the capping layer 120 is only a portion of the outer surface of the gold nanocluster 110, or the gold nanocluster 110. Some portions of the outer surface of the cluster 110 are encapsulated or coated. As is apparent from the experimental data of the examples provided herein, the presence of both benzene and phosphine functional groups in the capping layer provides satisfactory fluorescent characteristics for the composite fluorescent gold nanocluster 100.

  According to various embodiments of the present disclosure, the matrix 122 is made of a benzene-based compound. Examples of benzene-based compounds include benzene, alkylbenzenes (eg, toluene, cumene, ethylbenzene, styrene, and xylene), halobenzenes (eg, fluorobenzene, chlorobenzene, bromobenzene, and iodobenzene), oxygen-containing benzenes (eg, phenol) , Benzoic acid, acetophenone, methyl benzoate, and anisole), nitrogen-containing benzene (eg, aniline, nitrobenzene, benzonitrile, and benzamide), sulfur-containing benzene (eg, benzenesulfonic acid), or polyaromatic (eg, naphthalene) , And anthracene). According to some embodiments of the present disclosure, the benzene-based compound is toluene.

  With respect to the phosphine-based compound 124, this indicates a molecule having at least one phosphine group (eg, phosphine, phosphine oxide, or phosphonium form). Phosphine-based compounds are known to those skilled in the art, and suitable examples of phosphine-based compounds are phosphine, phosphine oxide, phosphonium, diphosphine, triphosphine, alkylphosphine, cycloalkylphosphine, arylphosphine, arylphosphine oxide, bidentate. Including but not limited to phosphine, phosphine silicone derivatives, phosphine siloxane or polysilane derivatives, and olefin phosphines. In some embodiments, the phosphine-based compound is an alkyl phosphine, such as trioctyl phosphine (TOP). In other examples, the phosphine-based compound is an aryl phosphine oxide, such as trioctyl phosphine oxide (TOPO).

  According to certain embodiments of the present disclosure, the peak emission of the composite fluorescent gold nanocluster 100 is from about 500 nm to about 580 nm, eg, 500, 505, 510, 515, 520, 525, 530, 535, 540, 545, 550, 555. 560, 565, 570, 575, and 580 nm. In some embodiments, the composite fluorescent gold nanocluster 100 has a peak emission wavelength of about 570 nm, and in other embodiments has a peak emission wavelength of about 575 nm.

  According to various embodiments of the present disclosure, the present composite fluorescent gold nanocluster 100 may be produced by any method shown in the examples. The method is advantageous in at least the following aspects. (1) Since the method does not require the use of any reducing agent, the resulting gold nanoclusters do not contain any toxicity that may be caused by the reducing agent used in conventional methods. (2) This fluorescent gold nanocluster is biocompatible. (3) By applying one or more of the energy treatments including but not limited to light, sonic energy, heat, and microwaves, the fluorescence characteristics (eg, peak emission and fluorescence intensity) of the composite fluorescent gold nanocluster Etc.) can be adjusted.

According to some embodiments of the present disclosure, composite fluorescent gold nanoclusters are prepared by a method comprising the following steps.
(A) mixing gold (III) chloride (AuCl ₃ ) and a benzene-based compound in a molar ratio of about 1: 0.5 to 1: 5 to produce a first fluorescent gold nanocluster;
(B) treating the first fluorescent gold nanocluster with an energy source selected from the group consisting of UV, sonic, heat, microwave, and combinations thereof to produce a second fluorescent gold nanocluster; And (c) modifying the second fluorescent gold nanocluster of step (b) with a phosphine-based compound to produce a composite fluorescent gold nanocluster, wherein the method does not use any reducing agent And

  Examples of benzene-based compounds suitable for use in the present method include benzene, alkylbenzenes (eg, toluene, cumene, ethylbenzene, styrene, and xylene), halobenzenes (eg, fluorobenzene, chlorobenzene, bromobenzene, and iodobenzene) , Oxygen-containing benzene (eg, phenol, benzoic acid, acetophenone, methyl benzoate, and anisole), nitrogen-containing benzene (eg, aniline, nitrobenzene, benzonitrile, and benzamide), sulfur-containing benzene (eg, benzenesulfonic acid), Or including, but not limited to, polyaromatics (eg, naphthalene and anthracene). According to some embodiments of the present disclosure, the benzene-based compound is toluene.

  According to some embodiments, to produce the first fluorescent gold nanocluster, the gold (III) chloride is about 0.5 to about 10 micrograms per microliter of benzene-based compound and benzene-based compound. Are mixed at a ratio of Preferably, this ratio is about 1 to 7.5 micrograms of gold (III) chloride per microliter of benzene-based compound. For example, about 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5 per microliter of benzene-based compound. , 7, 7.5, 8, 8.5, 9, 9.5, or 10 micrograms of gold (III) chloride may be used. In other words, gold (III) chloride and the benzene-based compound are mixed in a molar ratio of about 1: 0.5 to 1: 5. Specifically, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2, 2.5, 1 mole part of gold chloride (III) There are 3, 3.5, 4, 4.5, or 5 mole parts of a benzene-based compound.

  The first fluorescent gold nanoclusters thus generated emit blue light upon excitation. In order to adjust the peak wavelength and / or radiation intensity, the first fluorescent gold nanocluster is further exposed to at least one energy source for a specific period of time (ie step (b)). Examples of energy sources include, but are not limited to, UV light, sonic energy, heat, microwaves, and the like. According to embodiments of the present disclosure, the first fluorescent gold nanocluster is exposed to UV light for 1-5 hr (eg, 2 hr) to produce a second fluorescent gold nanocluster that emits yellow light upon excitation. . Alternatively or optionally, the first fluorescent gold nanocluster is exposed to heat (eg, 80 ° C. or 120 ° C.) for 1-5 hr, preferably about 2 hr, to produce a second fluorescent gold nanocluster. More optionally, the first fluorescent gold nanocluster is exposed to heat (eg, 80 ° C.) for 1-5 hr and then exposed to UV for 1-5 hr to produce a second fluorescent gold nanocluster.

  The second fluorescent gold nanocluster is then mixed with a phosphine-based compound to produce the desired composite fluorescent gold nanocluster that emits green or yellow light (ie, step (c)). Suitable examples of phosphine-based compounds are phosphine, phosphine oxide, phosphonium, diphosphine, triphosphine, alkylphosphine, cycloalkylphosphine, arylphosphine, arylphosphine oxide, bidentate phosphine, phosphine silicone derivatives, phosphine siloxanes or polysilanes Including, but not limited to, derivatives and olefin phosphines. In some embodiments, the phosphine-based compound is an alkyl phosphine, such as trioctyl phosphine (TOP). In other examples, the phosphine-based compound is an aryl phosphine oxide, such as trioctyl phosphine oxide (TOPO).

  According to embodiments of the present disclosure, the methods described herein are characterized by not using any reducing agent such as sodium citrate.

According to another embodiment of the present disclosure, the composite fluorescent gold nanocluster comprises (a) gold (III) chloride (AuCl ₃ ), a benzene-based compound, and a phosphine-based compound at 1: 0.5: 0. Mixing at a molar ratio of 1 to 1: 5: 20 to produce a third fluorescent gold nanocluster, and (b) selected from the group consisting of UV, sonic, heat, microwave, and combinations thereof Treating the third fluorescent gold nanocluster with an energy source to produce a composite fluorescent gold nanocluster. This method is characterized by not using any reducing agent (eg, sodium citrate).

  The method of these embodiments differs from the method described above in that the phosphine-based compound is added in step (a) rather than after energy treatment. However, whether the phosphine-based compound is included first (eg, in step (a)) or later (eg, after UV and / or heat treatment), the resulting composite fluorescent gold nanoclusters are The timing of adding the phosphine-based compound is not critical to the method because it emits all green or yellow light. As will be apparent from the experimental data provided below, the fluorescence intensity of the composite fluorescent gold nanoclusters is further increased by adding the phosphine-based compound multiple times both before and after thermal and / or UV treatment.

  As can be appreciated by one of ordinary skill in the art, benzene-based compounds and phosphine-based compounds suitable for use in the present methods can be any compound described above in connection with the present composite fluorescent gold nanocluster.

  The following examples are provided to clarify certain aspects of the present invention and to assist one of ordinary skill in carrying out the invention. These examples should in no way be considered as limiting the scope of the invention in any way. Those skilled in the art will be able to make the most of the present invention based on the description herein without further elaboration.

Example 1
Preparation of Blue and Yellow Fluorescent Gold Nanoclusters Capped with a Matrix Made of Benzene-Based Compounds In this example, a hydrophobic inorganic gold-containing compound is used as a starting material, and a benzene-based compound is used as a solvent. Fluorescent gold nanoclusters were prepared without using any reducing agent.

1.1 Preparation of blue fluorescent gold nanoclusters capped with toluene In an oxygen-free and anhydrous glove box, 1 mg of gold (III) chloride (AuCl ₃ ) was added to 1 ml of toluene (approximately 1: 2.85). Molar ratio). The mixture was shaken for about 1 minute to facilitate mixing and then centrifuged at 3,000 rpm for 5 minutes and the supernatant was collected. This supernatant contained blue fluorescent gold nanoclusters (or nanoclusters) capped with toluene (hereinafter referred to as blue fluorescent gold nanocluster 1).

  The product was subjected to nuclear magnetic resonance (NMR) spectroscopy using a Bruker NMR 400 MHz spectrometer to determine whether aromatic components were present on the surface of the resulting gold nanocluster. It was. 2A and 2B are 1H-NMR spectra of the standard toluene solution and the present blue fluorescent gold nanocluster 1, respectively. As shown in FIG. 2A, significant signals appeared in the vicinity of 7 to 8 ppm, which were characteristic signals of the benzene ring due to the diamagnetic ring current. Also in FIG. 2B, a benzene ring signal of about 7-8 ppm was observed. It is considered that the fluorescence characteristics and adjustability of the gold nanoclusters in this example were due to the presence of a benzene ring structure on the surface of the gold nanoclusters.

1.2 Preparation of Toluene Capped Yellow Fluorescent Gold Nanoclusters The blue fluorescent gold nanocluster 1 of Example 1.1 is placed in a quartz cell and using a handheld ultraviolet (UV) lamp with a peak emission of 365 nm. Irradiated for 2 hours. FIG. 3A is a photograph of the gold nanocluster composition before (left panel) and after (right panel) UV irradiation. As can be seen from these photographs, the fluorescence emitted from the gold nanoclusters changed from blue fluorescence to yellow fluorescence after UV irradiation. FIG. 3B is a 1H-NMR spectrum of the yellow fluorescent gold nanocluster (hereinafter referred to as yellow fluorescent gold nanocluster) capped with toluene thus produced, and this 1H-NMR spectrum also shows a characteristic benzene ring signal at about 7-8 ppm. It was.

  Based on the results of both Examples 1.1 and 1.2, UV radiation can lead to a red shift in the color of fluorescent gold nanoclusters, and each of the gold nanoclusters thus prepared has a benzene ring component on the surface. I have confirmed that I have.

Example 2
Modulation of the fluorescence characteristics of the fluorescent gold nanoclusters of Example 1 by heat and / or UV In this example, the fluorescence characteristics of the fluorescent gold nanoclusters of Example 1 were investigated by using heat and / or UV irradiation. .

Briefly, gold chloride (III) (AuCl ₃ ) and toluene are mixed at a molar ratio of about 1: 0.33 (7.5 mg AuCl ₃ per microliter of toluene) and further heat and / or UV A blue fluorescent gold nanocluster was prepared according to the same procedure as in Example 1.1 except that the treatment was performed. In the case of UV treatment, the reaction mixture was pre-centrifuged and the supernatant was collected for further processing and analysis.

2.1 UV treatment Referring to FIG. 4A, the blue fluorescent gold nanoclusters thus prepared are colorless under a normal light source (left panel) and have a blue emission with a peak emission that appears at 470 nm when UV light is used as the light source. The photograph shows that fluorescence was emitted (right panel).

  The blue fluorescent gold nanoclusters were then diluted with toluene to produce 1/2, 1/4, 1/8, or 1/16 times diluted blue fluorescent gold nanoclusters that were subjected to 3 hours of UV exposure ( Irradiation wavelength: 365 nm; irradiation power: 100 W), and the emission spectrum was measured at an excitation wavelength of 350 nm. Similar to the findings in FIG. 3B, during the UV treatment, the blue fluorescent gold nanoclusters changed to yellow fluorescent gold nanoclusters capped with toluene. Furthermore, the trend (eg, red shift from about 450 nm to 550 nm, and increased quantum yield) was the same for all dilutions of gold nanoclusters tested (FIG. 4B).

  In addition, when the blue fluorescent gold nanoclusters were exposed to UV for up to 5 hours, the peak emission of the yellow fluorescent gold nanoclusters was observed at 550 nm (excitation wavelength: 350 nm) after 2 hours of UV irradiation as shown in FIG. 4C. However, this peak remained relatively the same even when UV exposure was continued for a total of 5 hours. This same emission peak (about 550 nm) was also observed in fluorescent gold nanoclusters treated with UV for 24 hours (data not shown).

  FIG. 4D is a field emission gun transmission electron microscope (FEG-TEM) photograph of yellow fluorescent gold nanoclusters after 24 hours exposure to UV light, which shows the average diameter of the nanoclusters. It is about 2.6 nm.

  The results of this example showed that the fluorescence band of fluorescent gold nanoclusters can be tuned by UV treatment and that the fluorescence intensity (ie quantum yield) is also enhanced by UV treatment. Gold nanoclusters after UV exposure had a peak emission of about 550 nm when excited using a 350 nm fluorescence spectrometer, which gave yellow fluorescence.

2.2 Heat Treatment In this example, the blue fluorescent gold nanocluster of Example 2.1 was subjected to a heat treatment at 80 ° C. or 120 ° C. for 1 hour. The results are shown in FIGS. 5A and 5B. Heat was found to be as effective as UV radiation in causing a red shift of the emission wavelength of blue fluorescent gold nanoclusters, where peak emission after heating for 1 hour at 80 ° C. and 120 ° C., respectively. Shifted from 450 nm to about 495 nm (green fluorescence, FIG. 5A) and 570 nm (yellow fluorescence, FIG. 5B).

  5C and 5D are TEM photographs of the green and yellow fluorescent gold nanoclusters of FIGS. 5A and 5B, respectively. Although the average diameter of these fluorescent gold nanoclusters was about 2.6 nm, it was found that heat treatment tends to produce more gold nanoparticles of relatively large size, probably due to heat-induced aggregation of the clusters. I found it.

2.3 Combination of heat and UV treatment In this example, the green fluorescent gold nanoclusters and yellow fluorescent gold nanoclusters of Example 2.2 were independently diluted 2-fold and then treated with UV irradiation for up to 5 hours. (Irradiation wavelength: 365 nm; irradiation power: 100 W).

  Similar to the findings in FIG. 5A, the heat treatment at 80 ° C. changed the blue fluorescent gold nanoclusters to green fluorescent gold nanoclusters, and the peak emission shifted red to about 500 nm (FIG. 6A). When green fluorescent gold nanoclusters are diluted to 1/2, 1/4, 1/8, 1/16 /, and 1/32 of the original concentration, the peak emission is slightly blue shifted to about 480 nm. , The fluorescence intensity increased significantly (FIG. 6A, only data for 1/2 and 1/4 dilutions are shown). When the heat-treated gold nanoclusters were irradiated with UV light for 3 hours, the fluorescent gold nanoclusters thus generated emitted yellow fluorescence instead of green fluorescence, and peak emission appeared at 575 nm at an excitation wavelength of 350 nm ( FIG. 6A). Furthermore, the UV-induced red shift in the emission spectrum of heat-treated fluorescent gold nanoclusters reaches a plateau after 2 hours of UV exposure, and the peak emission is relatively the same at 575 nm even when UV exposure is continued for up to 5 hours. Noted that it remained (FIG. 6B).

  FIGS. 7A and 7B are the results when fluorescent gold nanoclusters were subjected to a combination of heating at 120 ° C. for 1 hour and UV exposure for up to 5 hours. It has been found that heating at a higher temperature (ie 120 ° C. rather than 80 ° C.) shifts the peak emission towards the red end of the spectrum (ie 570 nm). When the heat-treated gold nanoclusters were further exposed to UV light for 2 hours, the peak emission moved further to 575 nm towards the red edge (FIG. 7A), and these gold nanoclusters were exposed to UV for longer periods, for example up to 5 hours. Even if it continued to expose, it did not change as it is (FIG. 7B).

  In summary, it was confirmed from the data of this example that the fluorescence characteristics (eg, emission peak and fluorescence intensity) of gold nanoclusters can be adjusted by treatment with heat or UV or both.

Example 3
Preparation of Composite Fluorescent Gold Nanoclusters and Adjustment of Fluorescent Characteristics In this example, various surfactants were used as capping agents to investigate whether surfactants affect the fluorescent characteristics of composite fluorescent gold nanoclusters. It was.

3.1 Preparation of Composite Fluorescent Gold Nanoclusters Containing Trioctylphosphine (TOP) and Adjustment of Fluorescent Characteristics Briefly, the blue color of Example 1.1 to produce TOP / toluene capped fluorescent gold nanoclusters Fluorescent gold nanoclusters and a toluene solution containing 200 mM TOP were mixed at a volume ratio of 9: 1. Next, TOP / toluene capping fluorescent gold nanoclusters were irradiated with a UV lamp (365 nm) for a maximum of 2 hours, and the fluorescence spectrum of TOP / toluene capping fluorescent gold nanoclusters was measured every 10 minutes.

  Referring to FIG. 8A, this figure shows that the peak emission of the TOP / toluene capping fluorescent gold nanocluster before UV treatment (0 min) is red-shifted from about 450 nm to about 470 nm, and its full width at half maximum (FWHM) is shown. half maximum) was 0.55 eV, indicating that the fluorescence intensity was significantly increased. As the duration of the UV treatment increased, the peak emission of the composite fluorescent gold nanocluster gradually shifted red to 500 nm and the final FWHM was 0.64 eV. Overall, the results summarized in FIG. 8A showed that modification with TOP increased the fluorescence intensity of the composite fluorescent gold nanocluster. In addition, UV treatment could be used to tune the emission spectrum of TOP-modified fluorescent nanoclusters.

  Alternatively, composite fluorescent gold nanoclusters containing TOP were prepared by adding gold (III) chloride (1 mg / mL) to a toluene solution containing 200 mM TOP. As expected, the peak emission of the TOP / toluene capped fluorescent gold nanocluster thus produced appeared at about 470 nm and the FWHM was about 0.45 eV. Furthermore, after UV irradiation, the peak emission of the composite fluorescent gold nanocluster further moved toward the red edge to 500 nm, the FWHM was about 0.66 eV, and the fluorescence intensity also increased significantly (Fig. 8B).

  In summary, the data from this example confirmed that TOP not only caused a red shift in the peak emission wavelength of fluorescent gold nanoclusters, but also enhanced fluorescence intensity. In addition, TOP incorporation does not adversely affect the tunability of fluorescent gold nanoclusters by UV treatment.

3.2 Preparation of composite fluorescent gold nanoclusters containing trioctylphosphine oxide (TOPO) and modulation of fluorescent characteristics In this example, fluorescent gold nanoclusters in a manner similar to that described in Example 3.1 In this preparation, TOPO was used instead of TOP. The results are provided in FIG.

  Similar to the findings in Example 3.1, the addition of TOPO resulted in a red shift of the emission spectrum of the fluorescent gold nanocluster, the peak emission of the fluorescent gold nanocluster shifted from 450 nm to 470 nm, and the FWHM is It was about 0.49 eV (FIG. 9). When the fluorescent gold nanoclusters were further irradiated with UV for 2 hours, the peak emission moved further toward the red edge to about 500 nm and the FWHM rose to about 0.64 eV. Furthermore, the fluorescence intensity of the composite fluorescent gold nanoclusters thus generated also increased after UV treatment (FIG. 9).

  Similar to the findings of FIG. 8B, the gold produced in this way was prepared when a composite gold nanocluster containing TOPO was prepared by directly adding gold (III) chloride (1 mg / mL) to a toluene solution containing 200 mM TOPO. The peak emission of the nanoclusters appeared at about 470 nm, the FWHM was about 0.43 eV, and after treatment with UV light for 2 hours, the emission peak shifted to 550 nm and the FWHM was about 0.66 eV (data is Not shown). Furthermore, the fluorescence intensity of the composite fluorescent gold nanoclusters thus generated also increased after UV treatment (data not shown).

  In summary, from the results of this example, it was confirmed that TOPO was also effective in redshifting the peak emission of fluorescent gold nanoclusters and enhancing their fluorescence intensity, similar to TOP. In addition, TOPO incorporation does not adversely affect the tunability of fluorescent gold nanoclusters by UV treatment.

3.3 Preparation of fluorescent gold nanoclusters containing 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP: 1,2-dioleoyl-3-trimethylammonium-propane) and modulation of fluorescent characteristics In this example, DOTAP was used instead of TOP in the preparation of fluorescent gold nanoclusters in a manner similar to that described in Example 3.1. The difference between DOTAP and TOP in Example 3.1 or TOPO in Example 3.2 is that the molecule does not contain a phosphine group. The results are provided in FIG.

  The peak emission of blue fluorescent gold nanoclusters was red-shifted from 450 nm to 470 nm by adding DOTAP, and the FWHM was about 0.52 eV. However, the fluorescence intensity was significantly increased as compared to the fluorescent gold nanocluster not containing DOTAP (FIG. 10). When the DOTAP-containing fluorescent gold nanoclusters were further irradiated with UV for 2 hours, the peak emission shifted slightly to about 480 nm, which was still in the blue light range. In addition, the FWHM rose to about 0.71 eV. Furthermore, the fluorescence intensity of DOTAP-containing fluorescent gold nanoclusters was not increased by UV irradiation for up to 2 hours (FIG. 10).

  Alternatively, fluorescent gold nanoclusters containing DOTAP were prepared by adding gold (III) chloride (1 mg / mL) directly to a toluene solution containing 200 mM DOTAP, and as with the findings in FIG. Peak emission appeared at 470 nm and the FWHM was about 0.4 eV. After treating the fluorescent gold nanoclusters with UV light for an additional 2 hours, the peak emission shifted slightly to 480 nm and the FWHM was about 0.7 eV (data not shown).

  In summary, the data in this example showed that inclusion of phosphine-free surfactants such as DOTAP compromised the tunability of the fluorescent characteristics of fluorescent gold nanoclusters. In particular, the composite fluorescent gold nanoclusters of Examples 3.1 and 3.2 showed desirable tunability in that both peak emission and fluorescence intensity were significantly adjusted by external energy. On the other hand, the peak emission of DOTAP-containing fluorescent gold nanoclusters could not reach above 500 nm after 2 hours of UV irradiation. In addition, in some cases, UV treatment failed to substantially increase the fluorescence intensity of DOTAP-containing fluorescent gold nanoclusters.

Example 4
Modulation of fluorescence characteristics of composite fluorescent gold nanoclusters by heat and / or UV In this example, fluorescent gold nanoclusters were prepared according to the steps described in Example 2, followed by further addition of TOP and composites capped with TOP Fluorescent gold nanoclusters were generated.

  Briefly, the fluorescent gold nanocluster of Example 2.1 (UV treatment) or Example 2.2 (heat treatment) and a toluene solution containing 200 mM TOP were mixed at a volume ratio of 9: 1. , Fluorescent gold nanoclusters capped with TOP were generated. The fluorescent gold nanoclusters thus produced were then further treated with UV irradiation for 24 hours.

  It was found that the peak emission of the TPO-containing fluorescent gold nanoclusters remained relatively unchanged compared to the control (ie the TPO-free fluorescent gold nanocluster of Example 2.1). On the other hand, the fluorescence intensity of TPO-containing fluorescent gold nanoclusters increased compared to the control (FIG. 11). After UV treatment, the fluorescence intensity of the composite fluorescent gold nanoclusters thus generated increased significantly and the peak emission shifted red to about 555 nm (FIG. 11).

  In some cases, composite fluorescent gold nanoclusters were further treated with TOP. The results showed that further addition of TOP to the TOP-containing fluorescent gold nanoclusters further improved the fluorescence intensity while the peak emission remained substantially the same (FIG. 11).

  For the heat treated (80 ° C.) fluorescent gold nanoclusters of Example 2.2, the diluted nanoclusters were capped with TOP and then UV irradiated for 24 hours. According to FIG. 12, the addition of TOP does not affect the tunability of the peak emission of heat treated fluorescent gold nanoclusters by UV treatment. On the other hand, the fluorescence intensity of the composite fluorescent gold nanoclusters thus generated was greatly enhanced by the addition of TOP (FIG. 12).

  In conclusion, the experimental results of Examples 1 to 4 show that when the fluorescent gold nanoclusters are capped with a benzene-containing compound (eg, toluene), external energy such as UV irradiation, heat, or a combination of both is applied. It was shown that the peak emission and fluorescence intensity of fluorescent gold nanoclusters can be adjusted by adding. In this manner, the emission peak of the fluorescent gold nanocluster shifts red from a blue wavelength to a green or yellow wavelength (typically in the range of about 500-580 nm, such as 575 nm), and its fluorescence intensity increases significantly. . On the other hand, for fluorescent gold nanoclusters with emission peaks in or near the blue wavelength range, capping the fluorescent gold nanoclusters with a phosphine-based surfactant can also reduce the red to the green or yellow wavelength of the emission peak. Promote the shift. However, for fluorescent gold nanoclusters with relatively stable green or yellow wavelength emission peaks, no further redshift occurs due to capping of the phosphine-based surfactant. Furthermore, capping of the phosphine-based surfactant increases the fluorescence intensity of the fluorescent gold nanocluster to a higher degree. As can be appreciated, gold nanoclusters have a blue wavelength emission peak, and as apparent from the experimental data provided herein, capping the gold nanoclusters with a benzene-containing compound and a phosphine-containing compound results in The resulting composite fluorescent gold nanoclusters may emit green or yellow fluorescence and their fluorescence intensity is greatly increased. In view of the foregoing, the proposed composite fluorescent gold nanocluster has a better (or higher) quantum yield (ie, luminous efficiency).

  It will be understood that the above description of embodiments is given by way of example only and various modifications may be made by those of ordinary skill in the art. The above specification, examples, and data provide a complete description of the structure and use of exemplary embodiments of the invention. While various embodiments of the present invention have been described above in some detail or with reference to one or more individual embodiments, those of ordinary skill in the art will not depart from the spirit or scope of the present invention. Numerous changes may be made to the disclosed embodiments.

Claims (6)

With gold nanoclusters,
A capping layer comprising a matrix made of a benzene-based compound and a plurality of phosphine-based compounds dispersed in the matrix;
The composite fluorescent gold nanocluster, wherein the capping layer encapsulates at least a portion of the outer surface of the gold nanocluster.   The benzene-based compound is selected from the group consisting of benzene, alkylbenzene, halobenzene, phenol, benzoic acid, acetophenone, methyl benzoate, anisole, aniline, nitrobenzene, benzonitrile, benzamide, benzenesulfonic acid, naphthalene, and anthracene. The composite fluorescent gold nanocluster according to claim 1. The alkylbenzene is toluene, cumene, ethylbenzene, styrene, or xylene;
The composite fluorescent gold nanocluster according to claim 2, wherein the halobenzene is fluorobenzene, chlorobenzene, bromobenzene, or iodobenzene.   The composite fluorescent gold nanocluster according to claim 3, wherein the benzene-based compound is toluene.   The phosphine-based compounds include phosphine, phosphine oxide, phosphonium, diphosphine, triphosphine, alkylphosphine, cycloalkylphosphine, arylphosphine, arylphosphine oxide, bidentate phosphine, phosphine silicone derivatives, phosphine siloxanes or polysilane derivatives, and olefins The composite fluorescent gold nanocluster according to claim 1, which is selected from the group consisting of phosphine.   The composite fluorescent gold nanocluster according to claim 5, wherein the alkylphosphine is trioctylphosphine (TOP) and the arylphosphine oxide is trioctylphosphine oxide (TOPO).