WO2012035545A2

WO2012035545A2 - Non-functionalized carbon nanoparticles having fluorescence characteristics, method of preparation thereof, and their use as bioimaging and solvent sensing agents.

Info

Publication number: WO2012035545A2
Application number: PCT/IN2011/000610
Authority: WO
Inventors: Himadri Bihari Bohidar; Pardip Kumar
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-09-14
Filing date: 2011-09-07
Publication date: 2012-03-22
Anticipated expiration: 2013-03-14
Also published as: WO2012035545A3

Abstract

The invention relates to non-functionalized carbon nanoparticles having fluorescence characteristics, which are capable of causing bioimaging of cells and sensing of organic solvents. In one embodiment, it relates to method of manufacturing the non-functionalized fluorescent carbon nanoparticles comprising steps of a) depositing carbon soot emanating from flame of a burner on copper surface till at least a layer of carbon soot is deposited on copper surface, and b) removing the layer of carbon soot from copper surface to generate non-functionalized carbon nanoparticles having fluorescence characteristics, which can be directly used as bioimaging agent or solvent sensing agent.

Description

Title of the Invention :-

Non-functional ized Carbon Nanoparticles having Fluorescence Characteristics, Method of Preparation Thereof, and their Use as Bioimaging and Solvent Sensing Agents.

Field of the Invention:-

The present invention relates to non-functionalized carbon nanoparticles having fluorescent characteristics and method of preparation thereof.

In one embodiment, the present invention relates to bioimaging of cells by employing non-functionalized carbon nanoparticles having fluorescent characteristics of present invention as bioimaging agents.

In another embodiment, the present invention relates to sensing a solvent, particularly organic solvent, and more particularly common organic solvent by employing non-functionalized carbon nanoparticles having fluorescent characteristics of present invention as solvent sensing agent.

Background of the Invention :-

The imaging of cells to know their status of health and identification of various stages is need of everyday life. Various tools for in-vivo imaging of cells by Positron Electronic Telescope [PET], fluorescence tagging, NMR spectroscopy are known in the art. However, these are not only expensive, but also have limited applicability and are multistep processes.

However, the in-vitro imaging of cells to know their status of health and identification of its stage is not very common in the art. Further, such methods suffer from problems of being highly time consuming and limited applicability. For each test, one has to use a specific tool and method resulting in their limited applicability.

Further, sensing of solvents, particularly organic solvents, more particularly common organic solvents, is also need of everyday for research and analytical science. Generally, one has to perform various analytical tests to sense an organic solvent resulting not only in consumption of time, but also in consumption of money. Further, these known methods are also specific to the solvent, meaning thereby are not universally applicable.

Accordingly, presently available tools and methods for imaging cells to know their status of health and identification of its stage, and for sensing of organic solvents are not only very time consuming but are also very expensive and have limited applicability.

Need of the Invention:-

Therefore, there is a need to provide a tool and a method, which can image the cells to know their status of health and identify its stage, and can also sense organic solvents, and still being not only very time saving but also being very economical, and hence, being affordable, and also being universally applicable.

Problem to be Solved by the Invention :-

The present invention, therefore, aims to solve the existing problems of existing tools and methods of imaging cells to know their status of health and identification of its stage by providing an imaging agent, which is capable of causing imaging of the cells to know their status of health and identify their stage, by comparison studies, immediately upon mixing with the cells and a method of imaging the cells by employing the same.

The present invention, therefore, also aims to solve the existing problems of existing tools and methods of sensing of organic solvents by providing a sensing agent, which is capable of causing sensing of organic solvents, particularly of commonly used organic solvents promptly upon mixing with the solvent, by comparison studies, and a method of sensing of organic solvents by employing the same.

Accordingly, the present invention aims to overcome problems of time consumption, non-affordability and limited applicability of the existing tools and methods of imaging the cells and sensing the solvents, by providing an agent which can cause imaging of the cells or sensing of the organic solvent without wasting time and still being very economical, and hence, being affordable, and also being universally applicable.

Objects of the Invention :-

Therefore, main object of the present invention is to provide an imaging agent, which can cause imaging of cells to know their status of health and identify their stage, by comparison studies, immediately upon mixing with the cells, that is, without wasting time, and still being very economical, and hence, being affordable, and also being universally applicable, and a method of preparation thereof and a method of imaging a cell by employing said imaging agent. Another main object of the present invention is to provide a sensing agent, which can sense the organic solvents, by comparison studies, promptly upon mixing with the solvent, that is, without wasting time, and still being very economical, and hence, being affordable, and also being universally applicable, and a method of preparation thereof and a method of sensing a solvent by employing said sensing agent.

Still another main object of the present invention is to provide an agent which can cause imaging of the cells or sensing of the organic solvent without wasting time and still being very economical, and hence, being affordable, and also being universally applicable, and a method of preparation thereof.

Yet another main object of the present invention is to provide use of agent to cause imaging of cells or sensing of organic solvents without wasting time and still being very economical, and hence, being affordable, and also being universally applicable.

The other objects and advantages of the present invention will become more apparent from the following description when read in conjunction with the accompanying figures, which are not intended to limit scope of present invention. Brief Description of the Invention :-

Accordingly, the present invention relates to non-functionalized carbon nanoparticles having fluorescence characteristics, which are capable of causing bioimaging of cells.

In one embodiment, the present invention relates to non-functionalized carbon nanoparticles having fluorescence characteristics, which are capable of causing sensing of organic solvents, particularly of commonly used organic solvents.

In one embodiment, the present invention relates to method of manufacturing the non-functionalized carbon nanoparticles having fluorescence characteristics, wherein the method comprises steps of:

a) depositing carbon soot emanating from flame of a burner on copper surface till at least a layer of carbon soot is deposited on copper surface; and

b) removing the layer of carbon soot from copper surface to generate non- functionalized carbon nanoparticles having fluorescence characteristics, which can be directly used as bioimaging agent or solvent sensing agent.

In one embodiment, the present invention relates to method of using non- functionalized carbon nanoparticles having fluorescence characteristics for imaging the cells of sensing the solvents.

In one embodiment, the present invention relates to method of imaging cells by employing non-functionalized carbon nanoparticles having fluorescence characteristics.

In one embodiment, the present invention relates to method of sensing solvents by employing non-functionalized carbon nanoparticles having fluorescence characteristics.

Brief Description of the Accompanying Figures:-

The accompanying figures 1, 2, 3 and 4A and 4B are originally color figures. Therefore, coloured prints of these figures are also enclosed because the black and white figures may not be illustrative of the intended imaging of cells and sensing of cells - benefits of present invention.

Figure 1 illustrates that non-functionalized carbon nanoparticles, prepared in accordance with one of the embodiments of present invention, when dispersed in water and viewed by fluorescence microscope, emit [or show] distinct fluorescence under ultra-violet [UV]-excitation of wavelength varying from about 330 to about 385 nm [Figure IB], blue excitation of wavelength varying from about 470 to about 495 nm [Figure 1C], and green excitation of wavelength varying from about 530 to about 550 nm [Figure ID] confirming that the non-functionalized carbon nanoparticles of present invention are capable of being imaged and to cause imaging under different excitations due to their capability to emit different and distinct fluorescence of different and distinct colour contrast under different excitations. Figure 1A illustrates image of non-functionalized carbon nanoparticles of present invention under bright field.

Figure 2 illustrates that when cells are viewed by Laser Scanning Confocal Microscope, they show very light fluorescence due to their auto fluorescence characteristics under ultra-violet [UV] -excitation of wavelength about 405 nm [Figure 2B], blue excitation of wavelength of about 488 nm [Figure 2C], and green excitation of wavelength of about 543 nm [Figure 2D] confirming that the cells without non- functionalized carbon nanoparticles of present invention are not capable of causing distinguishable imaging under different excitations due to their inability to emit or produce distinguishable, different and distinct fluorescence of distinguishable, different and distinct colour contrast under different excitations. Figure 2A illustrates image of cells under bright field.

Figure 3 illustrates that non-functionalized carbon nanoparticles, prepared in accordance with one of the embodiments of present invention, when mixed with cells and viewed by Laser Scanning Confocal Microscope, emit [show] distinguishable and distinct fluorescence under ultra-violet [UV]-excitation of wavelength about 405 nm [Figure 3B], blue excitation of wavelength of about 488 nm [Figure 3C], and green excitation of wavelength of about 543 nm [Figure 3D] confirming that the non- functionalized carbon nanoparticles of present invention are capable of causing imaging of cells under different excitations due to their capability to emit different and distinct fluorescence of different and distinct colour contrast under different excitations. Figure 3 A illustrates image of non-functionalized carbon nanoparticles of present invention mixed with cells under bright field.

The cells employed in experiments of Figure 3 are human embryonic kidney (HEK-297) cells obtained from National Center for Cell Science [NCCS], Pune.

Figure 4A illustrates that non-functionalized carbon nanoparticles, prepared in accordance with one of the embodiments of present invention, when mixed in a solvent and viewed under white light and UV light of wavelength of about 300 nm, emit [or show] distinct fluorescence of distinct colour under UV light of wavelength of about 300 nm, wherein

Figure 4(A)(a) illustrates fluorescence of acetic acid under white light;

Figure 4(A)(b) illustrates fluorescence of acetic acid under UV light;

Figure 4(A)(c) illustrates fluorescence of methanol under white light;

Figure 4(A)(d) illustrates fluorescence of methanol under UV light;

Figure 4(A)(e) illustrates fluorescence of ethanol under white light;

Figure 4(A)(f) illustrates fluorescence of ethanol under UV light;

Figure 4(A)(g) illustrates fluorescence of propanol under white light;

Figure 4(A)(h) illustrates fluorescence of propanol under UV light;

Figure 4(A)(i) illustrates fluorescence of butanol under white light;

Figure 4(A)(j) illustrates fluorescence of butanol under UV light; Figure 4(A)(k) illustrates fluorescence of toluene under white light;

Figure 4(A)(1) illustrates fluorescence of toluene under UV light;

Figure 4(A)(m) illustrates fluorescence of benzene under white light;

Figure 4(A)(n) illustrates fluorescence of benzene under UV light;

Figure 4(A)(o) illustrates fluorescence of p-xylene under white light;

Figure 4(A)(p) illustrates fluorescence of p-xylene under UV light;

Figure 4(A)(q) illustrates fluorescence of pyridine under white light;

Figure 4(A)(r) illustrates fluorescence of pyridine under UV light;

Figure 4(A)(s) illustrates fluorescence of tetrahydrofuran (THF) under white light;

Figure 4(A)(t) illustrates fluorescence of tetrahydrofuran (THF) under UV light;

confirming that the non-functionalized carbon nanoparticles of present invention are capable of sensing the common organic liquids under different excitations due to their capability to emit different and distinct fluorescence of different and distinct color in different solvents.

Figure 4B illustrates that non-functionalized carbon nanoparticles, prepared in accordance with one of the embodiments of present invention, when mixed in a solvent and viewed under white light and UV light of wavelength of about 300 nm, emit [or show] distinct fluorescence of distinct colour under UV light of wavelength of about 300 nm, wherein

Figure 4(B)(a) illustrates fluorescence of iso-octane under white light;

Figure 4(B)(b) illustrates fluorescence of iso-octane under UV light;

Figure 4(B)(c) illustrates fluorescence of ethyl acetate under white light;

Figure 4(B)(d) illustrates fluorescence of ethyl acetate under UV light;

Figure 4(B)(e) illustrates fluorescence of acetonitrile under white light;

Figure 4(B)(f) illustrates fluorescence of acetonitrile under UV light;

Figure 4(B)(g) illustrates fluorescence of diethyl ether under white light;

Figure 4(B)(h) illustrates fluorescence of diethyl ether under UV light;

Figure 4(B)(i) illustrates fluorescence of cyclohexane under white light;

Figure 4(B)(j) illustrates fluorescence of cyclohexane under UV light;

Figure 4(B)(k) illustrates fluorescence of acetone under white light;

Figure 4(B)(1) illustrates fluorescence of acetone under UV light; Figure 4(B)(m) illustrates fluorescence of pentane under white light;

Figure 4(B)(n) illustrates fluorescence of pentane under UV light;

Figure 4(B)(o) illustrates fluorescence of hepatne under white light;

Figure 4(B)(p) illustrates fluorescence of heptane under UV light;

Figure 4(B)(q) illustrates fluorescence of carbon tetrachloride (CC1₄) under white light;

Figure 4(B)(r) illustrates fluorescence of carbon tetrachloride (CC )under UV light;

Figure 4(B)(s) illustrates fluorescence of dimethyl sulphoxide (DMSO) under white light;

Figure 4(B)(t) illustrates fluorescence of dimethyl sulphoxide (DMSO) under UV light;

Figure 5(A) illustrates fluorescence spectra obtained under excitation at 225 nm of solvents mixed with non-functionalized carbon nanoparticles prepared in accordance with one of the embodiments of present invention, wherein graphs I, II, III, IV and V of Figure 5(A)(a) illustrate fluorescence spectra of acetic acid, methanol, ethanol, propanol, butanol respectively; and graphs I, II, III, IV and V of Figure 5(A)(b) illustrate fluorescence spectra of benzene, THF, toluene, p-xylene and pyridine respectively as obtained after mixing these solvents with non-functionalized carbon nanoparticles of present invention.

Figure 5(B) illustrates fluorescence spectra obtained under excitation at 225 nm of solvents mixed with non-functionalized carbon nanoparticles prepared in accordance with one of the embodiments of present invention, wherein graphs I, II, III, IV and V of Figure 5(B)(a) illustrate fluorescence spectra of acetone, carbon tetrachloride (CCI₄), pentane, heptane and cyclohexane respectively; and graphs I, II, III, IV and V of Figure 5(B)(b) illustrate fluorescence spectra of acetonitrile, diethyl ether, DMSO, iso-octane and ethyl acetate respectively as obtained after mixing these solvents with non-functionalized carbon nanoparticles of present invention. It can be observed from Figures 5(A)(a), 5(A)(b), 5(B)(a), and 5(B)(b) that the fluorescence spectra of the non-functionalized carbon nanoparticles in different organic solvents give the different and distinct fluorescence spectra, which confirms that the non-functionalized carbon nanoparticles of present invention are capable of emitting different and distinct fluorescence spectra in different solvents, and thereby are capable of sensing (or identifying) the solvent.

Description of the Invention:-

With aim to overcome above-described problems of prior art, the inventors have found that when carbon nanoparticles having non-functionalized surface produced by depositing carbon soot emanating from flame of a burner on copper surface are mixed with cells, the cells, surprisingly and unexpectedly, emit [or show] distinguishable and distinct fluorescence of different and distinct colour contrast under various excitations including ultra-violet [UV] -excitation of wavelength about 405 nm, blue excitation of wavelength of about 488 nm, and green excitation of wavelength of about 543 nm, and such fluorescence from cells has been found to be capable of causing imaging of cells. It has also been observed that such image of cells may be used to know status of health of the cells being imaged and identification of its stage by comparison method.

The inventors have also found that when carbon nanoparticles having non- functionalized surface produced by depositing carbon soot emanating from flame of a burner on copper surface are mixed with solvents, the solvents, surprisingly and unexpectedly, emit [or show] distinguishable and distinct fluorescence of different and distinct colour contrast under various excitations including ultra-violet [UV]-light of wavelength of about 300 nm, excitation of wavelength of about 225 nm, and such fluorescence from solvents has been found to be capable of causing sensing of solvents.

The "comparison method" referred herein means that image of the cell to be imaged is compared with image of the normal cell, wherein said image is obtained after mixing the cells with non-functionalized carbon nanoparticles of present invention having fluorescence characteristics.

Accordingly, the present invention relates to non-functionalized carbon nanoparticles having fluorescence characteristics, which are capable of causing bioimaging of cells. The image thus obtained from the cell after mixing it with non- functionalized carbon nanoparticles of the present invention can be compared with image of a normal cell obtained from the normal cell after mixing it with non- functionalized carbon nanoparticles of the present invention to know status of health of the cell being imaged and identify its stage.

In accordance with one of the embodiments of the present invention, the cell is selected from a group comprising animal cell, human cell, wherein the human cell for example is human embryonic kidney (HEK-297) cell.

In another embodiment, the present invention relates to non-functionalized carbon nanoparticles having fluorescence characteristics, which are capable of causing sensing of organic solvents, particularly of commonly used organic solvents. The fluorescence thus obtained from the solvent after mixing it with non- functionalized carbon nanoparticles of the present invention and the fluorescence spectra obtained from mixture of solvent and non-functionalized carbon nanoparticles of the present invention can be used to identify the solvent.

In accordance with one of the embodiments of the present invention, the solvent is organic solvent, wherein the organic solvent is selected from a commonly available organic solvent.

In accordance with one of the embodiments of the present invention, the organic solvent is selected from a group comprising acetic acid, methanol, ethanol, propanol, butanol, toluene, benzene, p-xylene, pyridine, tetrahydrofuran (THF), iso- octane, ethyl acetate, acetonitrile, diethyl ether, cyclohexane, acetone, pentane, hepatne, carbon tetrachloride (CC ), and dimethyl sulphoxide (DMSO).

In accordance with present invention, the term "non-functionalized" means the surface of carbon nanoparticles of present invention is not functionalized and is used without any preparation or modifications.

As the "carbon nanoparticles" of present invention emit fluorescence under excitations of different wavelength, these are also referred to as "non-functionalized fluorescent carbon nanoparticles".

In one embodiment, the present invention relates to method of preparation of non-functionalized fluorescent carbon nanoparticles of present invention, wherein the method comprises steps of:- a) depositing carbon soot emanating from flame of a burner on copper surface; b) continuing step - a) till at least a layer of carbon soot is deposited on copper surface;

c) removing the layer of carbon soot from copper surface to generate non- functionalized fluorescent carbon nanoparticles of present invention, which are directly used as bioimaging agent or solvent sensing agent.

In accordance with present invention, the carbon nanoparticles produced are of about 30 nm or larger, preferably of size varying from about 30 nm to about 180 nm. It has been found that method of present invention spontaneously produces non- functionalized fluorescent carbon nanoparticles of about 30 nm size. Therefore, further step to separate out the nanoparticles is not required in accordance with advantage of method of present invention.

It has been observed that if carbon soot is deposited on a surface of another metal, for example aluminium, platinum, silver, gold, the particles produced surprisingly do not emit the fluorescence meaning thereby cannot be used as bioimaging agent or solvent sensing agents. Therefore, production of carbon nanoparticles on reaction of flame from a burner with surface of copper metal, and said carbon nanoparticles having fluorescent characteristics and being capable of bioimaging cells and sensing solvents, that's too, without any surface preparation is highly surprising and unexpected.

In accordance with process of present invention, in step b), it is sufficient if an amount of carbon soot is deposited which is required for the intended purpose.

In accordance with one of the preferred embodiments of the present invention, the carbon soot is generated from oil lamp provided with cotton wick.

In accordance with one of the preferred embodiments of the present invention, the oil in oil lamp is commercially available vegetable oil selected from a group comprising mustard oil, refined vegetable oil, coconut oil and butter oil.

Accordingly, it is clear from the foregoing that non-functionalized fluorescent carbon nanoparticles of present invention can be prepared just in one step in minimum possible time sufficient to deposit an amount required for the intended purpose.

The present invention is now described with the help of following examples, which are not intended to limit scope of the invention, but have been incorporated for better understanding of the invention.

Exam pies: - Bioimaging of the Cells:

The human embryonic kidney (HEK-297) cells obtained from National Center for Cell Science [NCCS], Pune, India were mixed with non-functionalized fluorescent carbon nanoparticles of present invention and viewed by Laser Scanning Confocal Microscope under ultra-violet [UV]-excitation of wavelength about 405 nm, blue excitation of wavelength of about 488 nm, and green excitation of wavelength of about 543 nm. The scans obtained were recorded, which have been illustrated in Figure 3B, Figure 3C, Figure 3D respectively, and upon comparing these scans with corresponding scans of HEK-297 cells without non-functionalized fluorescent carbon nanoparticles of present invention [Figure 2B, Figure 2C and Figure 2D respectively], it was found that the non-functionalized carbon nanoparticles of present invention cause imaging of cells under different excitations as the non-functionalized carbon nanoparticles of present invention emit different and distinct fluorescence of different and distinct colour contrast under different excitations. Figure 3A illustrates image of non-functionalized carbon nanoparticles of present invention mixed with cells under bright field. These experiments confirm that the non-functionalized carbon nanoparticles of present invention are capable of causing imaging of cells under different excitations due to their capability to emit different and distinct fluorescence of different and distinct colour contrast under different excitations.

Sensing of the Organic Solvents:

The commonly used organic solvents - acetic acid, methanol, ethanol, propanol, butanol, benzene, tetrahydrofauran (THF), toluene, p-xylene, pyridine, acetone, carbon tetrachloride (CC ), pentane, heptanes, cyclohexane, acetonitrile, diethyl ether, dimethyl sulphoxide (DMSO), iso-octane and ethyl acetate were mixed with non-functionalized fluorescent carbon nanoparticles of present invention. It was found that the solvents emit particular and characteristic fluorescence of distinguishable and distinct colour as illustrated in accompanying Figures 4A and 4B. The fluorescence thus emitted was used to identify the solvents. The fluorescence emitted was combined with particular and characteristic fluorescence spectra obtained under excitation at 225 nm of respective solvent mixture and recorded as illustrated in accompanying figures 5A and 5B to further identify the solvent. The wavelengths of particular and characteristic fluorescence peaks of each solvent mixed with non-functionalized carbon nanoparticles of present invention are given in Table - 1:-

Table - 1

It can be observed from the above table and the fluorescence as illustrated in Figure 4A and Figure 4B, the commonly used solvents can be identified by using non- functionalized fluorescent carbon nanoparticles of present invention.

The experimental data in accompanying Figures 5(A)(a), 5(A)(b), 5(B)(a), and 5(B)(b) confirm that the fluorescence spectra of the non-functionalized carbon nanoparticles in different organic solvents give different and distinct fluorescence spectra due to surprising and unexpected emission of different and distinct fluorescence from non-functionalized carbon nanoparticles of present invention in different solvents, and therefore, the non-functionalized carbon nanoparticles of present invention have been found to be capable of sensing (or identifying) the solvent.

These experiments confirm that the non-functionalized carbon nanoparticles of present invention are capable of sensing the common organic liquids under different excitations due to their capability to emit different and distinct fluorescence of different and distinct color in different solvents.

It may be noted the embodiments of present invention have been described with the help of limited cells and solvents. However, a person skilled in the art would know that the present invention may be extended to other cells and solvents without deviating from scope of present invention.

Claims

Non-functionalized carbon nanoparticles having fluorescence characteristics for bioimaging of cells.

Non-functionalized carbon nanoparticles as claimed in claim 1, wherein the cell is selected from a group comprising animal cell, human cell.

Non-functionalized carbon nanoparticles as claimed in claim 2, wherein human cell is human embryonic kidney (HEK-297) cell.

Non-functionalized carbon nanoparticles having fluorescence characteristics for sensing of solvents.

Non-functionalized carbon nanoparticles as claimed in claim 4, wherein the solvent is organic solvent.

Non-functionalized carbon nanoparticles as claimed in claim 5, wherein the organic solvent is selected from a commonly available organic solvent.

Non-functionalized carbon nanoparticles as claimed in claim 5, wherein the organic solvent is selected from a group comprising acetic acid, methanol, ethanol, propanol, butanol, toluene, benzene, p-xylene, pyridine, tetrahydrofuran (THF), iso-octane, ethyl acetate, acetonitrile, diethyl ether, cyclohexane, acetone, pentane, hepatne, carbon tetrachloride (CC1₄), and dimethyl sulphoxide (DMSO).

Non-functionalized carbon nanoparticles as claimed in any one of the preceding claims, wherein the carbon nanoparticles are of size varying from about 30 nm to about 180 nm.

A method for producing non-functionalized fluorescent carbon nanoparticles, wherein the method comprises steps of:- a) depositing carbon soot emanating from flame of a burner on copper surface;

b) continuing step - a) till at least a layer of carbon soot is deposited on copper surface;

c) removing the layer of carbon soot from copper surface to generate non- functionalized fluorescent carbon nanoparticles of present invention.

A method as claimed in claim 9, wherein carbon nanoparticles are of size varying from about 30 nm to about 180 nm. A method as claimed in claim 9 or 10, wherein, in step b), carbon soot is deposited till amount of non-functionalized fluorescent carbon nanoparticles sufficient for causing imaging cell or sensing solvent is deposited.

A method as claimed in any one of claims 9 to 11, wherein carbon soot is generated from oil lamp provided with cotton wick.

A method as claimed in any one of claims 9 to 12, wherein burner is oil burner containing commercially available vegetable oil selected from a group comprising mustard oil, refined vegetable oil, coconut oil and butter oil.

Use of non-functionalized fluorescent carbon nanoparticles produced from method as claimed in any one of claims 9 to 13 for bioimaging of cells and sensing of solvents.

Use of non-functionalized fluorescent carbon nanoparticles as claimed in claim 14, wherein non-functionalized fluorescent carbon nanoparticles are used without any surface preparation.

Non-functionalized carbon nanoparticles having fluorescence characteristics substantially as herein described with reference to foregoing examples and as illustrated with the help of accompanying figures.

A method for producing non-functionalized fluorescent carbon nanoparticles substantially as herein described with reference to foregoing examples and as illustrated with the help of accompanying figures.