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SYNTHESIS
OF WATER-SOLUBLE POLYHYDROXYLATED FULLERENES (FULLERENOLS) C60(OH)n
BY DIRECT HYDROXYLATION OF FULLERENE C60 FROM SUSPENSIONS OF FULLERENE IN WATER


          Abstract
         By now there are 2 main methods of fullerenol synthesis: hydroxylation of toluene solution of fullerene by crystal hydroxide of sodium or potassium and hydrolysis of fullerene bromide C60Br. These methods of C60(OH)n (polyhydroxylated fullerenes) fullerenol synthesis cannot have prospects for industrial use because of low efficiency, high complexity, high prices, non-manufacturability of such syntheses.
        Water‐soluble fullerenol was conveniently synthesized via the direct solvent‐free reaction of fullerene with a mixture of H2O2 and NaOH in air at low temperature. This practical method provides a novel and efficient access to water‐soluble fullerenol in excellent yield.

         Keywords: Fullerene, polyhydroxylated fullerenol, hydroxylation, synthesis, suspensions in water, sodium hydroxide, hydrogen peroxide H2O2 , sodium hydroxide, solvent‐free reaction.

The existing methods for synthesis of fullerenols C60(OH)n (polyhydroxylated fullerenes) cannot have prospects for industrial applications due to low efficiency, complexity, costliness, and poor processability of such a synthesis. The price of fullerenol (polyhydroxylated fullerene) in the process of synthesis grow exponentially as compared to the price of the fullerene itself, and today, the world market price of fullerenol C60(OH)22-26 is USD 380-800 per 1 g, which makes it unpromising for production on industrial scale. Moreover, the fullerenol produced using the classic method will always contain the traces of toluene or of another aromatic solvent which are used for classic syntheses. These methods allow producing only mildly-hydroxylated fullerenols C60(OH)18-28 but cannot be used for synthesis of highly-hydroxylated fullerenols C60(OH)36-42. For production of highly-hydroxylated fullerenols C60(OH)36-42, additional synthesis with the use of hydrogen peroxide is needed. One of such methods is discussed in the article Water-Soluble Single-Nano Carbon Particles: Fullerenol and Its Derivatives,  Ken Kokubo,  Division of Applied Chemistry, Graduate School of Engineering, Osaka University Japan http://cdn.intechopen.com/pdfs/36889.pdf.         
         

At Scientific and Technology Center Nanocluster (STC Nanocluster), an alternative to the existing methods has been developed, one-stage synthesis of fullerene hydroxylation into water-soluble polyhydroxylated fullerenes (fullerenols) 60(OH)n from a suspension of fullerene in water. The synthesis is completed in one stage and is carried out only in water environment, without the use of any solvents, including benzene, toluene, and ortho-xylene.

Fullerenol C60(OH)n

Polyhydroxylated fullerenes, water-soluble
Synonym: C60(OH)n, Fullerenols, Polyhydroxy fullerenes, water-soluble C60
Empirical Formula C60(OH)n (n>40)

        

Only 3 components are needed for the synthesis: fullerene, sodium hydroxide, and hydrogen peroxide. The conversion rate (level of transformation) of fullerene into water-soluble derivatives is around 99.5-99.8%. Fullerene can be used not only in the form C60, but also in any other form, including a mixture of fullerenes. The synthesis can be scaled up to industrial volumes.


        Water-soluble polyhydroxylated fullerenes (fullerenols) C60(OH)n  from C60(OH)40 of dark yellow color to C60(OH)60 of light yellow color (40 ≤ n ≤ 60) are formed during the synthesis. This fully corresponds to multiple researches of world leading specialists in the sphere of fullerenols, particularly professor Ken Kokubo (Japan), who proved that all the fullerenols higher than C60(OH)36 must be yellow in color. The more hydroxyl groups fullerenol has, the brighter yellow color tinge becomes. (Hydration or hydroxylation: direct of fullerenol from pristine fullerene [C60] via acoustic cavitation in the presence of hydrogen peroxide.  Sadia Afreen,  Ken Kokubo,  Kasturi Muthoosamy  and Sivakumar Manickam, The Royal Society of Chemistrys, 2017, 7, 31930-31939 http://pubs.rsc.org/en/content/articlehtml/2017/ra/c7ra03799f).
     But some companies, which produce polyhydroxylated fullerenes (fullerenols) C60(OH)n, for example, NANOGRAFI (Germany/Turkey) https://nanografi.com/, describe color of their product, announced as fullerenol C60(OH)n, which has more than 40 hydroxyl groups (n>40), as dark brown https://nanografi.com/fullerene/polyhydroxylated-fullerenes-fullerenols-c60-oh-functional-fullerene-dry-powder/. This is fully against researches of professor Ken Kokubo, because color of fullerenol even with smaller amount of hydroxyl groups C60(OH)36 must be yellow, not dark-brown (see Fig.10 Hydration or hydroxylation). Thus, company NANOGRAFI actually sells its fullerenols, which correspond to fullerenols with the amount of hydroxyl groups less than 36 (n<36) as fullerenols C60(OH)n with the amount of hydroxyl groups more than 40 (n>40). This concerns company US Research Nanomaterials, Inc http://www.us-nano.com/, which also sells fullerenols of dark brown color http://www.us-nano.com/inc/sdetail/44719, which correspond to fullerenols with the amount of hydroxyl groups less than 36 (n<36). Only company Sigma-Aldrich (USA, St. Louis) https://www.sigmaaldrich.com/ produces polyhydroxylated fullerenes (fullerenols) C60(OH)n with n>40 of yellow color - light yellow to yellow: https://www.sigmaaldrich.com/catalog/product/aldrich/793248?lang=en&region=US&cm_sp=Insite-_-recent_fixed-_-recent5-1 
But Sigma-Aldrich sells its fullerenol C60(OH)n (n>40) at price of 296 USD per 100 mg (*price for USA), which complicates its use in applied directions.
       2 individual fullerenols are sorted out and identified from the products of synthesis: dark yellow C60(OH)42 and  light yellow C60(OH)60. Highly polyhydroxylated fullerenol C60(OH)42 is a dark yellow crystalline product. The solubility of this fullerenol in water is 50-60 grams per liter. The color of the solution of this fullerene in water is dark yellow (see Fig. 1). The solubility of fullerenol C60(OH)60 in water is 60-70 grams per liter. The color of the solution of this fullerene in water is yellow (see Fig. 2).


Solution of a highly  polyhydroxylated fullerenol 60(OH)42 in the water

Solution of a highly  polyhydroxylated fullerenol 60(OH)60 in the water2


Fig. 1
Solution of a highly  polyhydroxylated fullerenol
60(OH)42 in the water


Fig. 2
Solution of a highly  polyhydroxylated fullerenol
60(OH)60 in the water
   
              Mass spectrum of dark yellow fullerenol (see Fig. 3) corresponds to the fullerenol 60(OH)42: Base Peaks 1433,9913 is equal to the molecular weight of fullerenol 60(OH)60 (M=1434).
Mass spectrum of the fullerenol C60(OH)42

Fig. 3 Mass spectrum of the fullerenol C60(OH)42


Mass spectrum of light yellow fullerenol (see Fig. 4) corresponds to the fullerenol 60(OH)60: Base Peaks 1739.9879 is equal to the molecular weight of fullerenol 60(OH)60 (M=1740).


Mass spectrum of the fullerenol C60(OH)60

Fig. 4 Mass spectrum of the fullerenol C60(OH)60

According to the data of the Elemental Analysis (EA), the synthesized hyperhydroxylated light yellow fullerenol has a molecular formula 60(OH)6022 (see Fig. 5).

Result of Elemental Analysis of hyper fullerenol

Element

Percentage (%)

Analytical

Method

Date

Remark

 

C

 

 

40.5972

 

40.6017

 

 

Flash EA

1112

 

 

12/12/2016

 

 

H

 

 

3.6098

 

3.6113

Fig. 5  Result of Elemental Analysis of highly fullerenol C60(OH)60

Synthesized Polyhydroxylated fullerenes, water-soluble C60(OH)n (40 ≤ n ≤ 60) are light yellow crystalline product (see Fig. 6). The solubility of this fullerenol in water is 60-70 grams per liter. The color of the solution of this fullerene in water is  yellow (see Fig. 2).

Fullerenol 60(OH)60 is a light yellow crystalline product
Fig. 6 Fullerenols 60()n (n>40) are a light yellow crystalline product

    

        The self-cost of Polyhydroxylated fullerenes, water-soluble C60(OH)n (40 ≤ n ≤ 60) are relatively not high because the cost of reagents used in the synthesis is not high as compared to the cost of fullerene. The synthesis is simple and easily producible, and it can be used for synthesis of fullerenol on industrial scale. In order to decrease the self-cost, fullerene with low level of purification (97-98%) can be used.

IR spectrum (see Fig. 7) was taken from polyhydroxylated fullerene (fullerenol) sample C60(OH)n (n>40). It is practically identical to IR spectrum of fullerenol, taken from Journal of Materials Chemistry A  (see Fig. 8). IR spectrum of polyhydroxylated fullerene (fullerenol) sample C60(OH)n (n>40) shows: broad band of absorption with maximum of 3382 cm1 in the area of stretching vibrations of OH groups; band of stretching vibrations C = C groups  1605 cm1;  band of vibrations COH 1386 cm1.


IR spectrum of polyhydroxylated fullerenes C60(OH)n

Literary IR spectrum of polyhydroxylated fullerenes C60(OH)n


Fig. 7
IR spectrum of sample of polyhydroxylated fullerene (fullerenol)  C60(OH)n with n>40  STC NANOCLASTER  production, made in the Instituteof organic synthesis (IOS) of Urals branch of the Academy of Sciences   (Ekaterinburg city)


Fig. 8

Literary IR spectrum of fullerenol, taken from

  Journal of Materials Chemistry A


WATER-SOLUBLE POLYHYDROXYLATED FULLERENES (FULLERENOLS) C60(OH)n  (n>40)  CAN BE USED FOR:

Pharmaceutics and cosmetology
    Antiviral medicine without cytotoxicity;
    Antioxidants, comparable to fullerenes under their effectiveness;
    Wound and burn healing medicine.

Materials science
    Modifiers of polymers, resins, glues, paint-and-lacquer and other materials;
    Modifiers of materials on base of silicate binding agents, including concretes;
    Component of electrolytes for metal galvanic coatings;
    Component of ultra-hard composite materials with metal matrix.

Agroindustry plant cultivation and animal husbandry
    Plant growth stimulants;
    Antiviral and antimycotic agents;
    Preparations, which increase stability of crops by complex nonspecific action;
    Additives to fodders, which increase resistibility of agricultural animals and birds to different diseases, and which do not accumulate in their organ
ism.

LIST OF LITERATURE

1.  Water-Solubl Single-Nano Carbon Particles: Fullerenol and Its Derivatives. Ken Kokubo,  Division of Applied Chemistry, Graduate School of Engineering, Osaka University Japan http://cdn.intechopen.com/pdfs/36889.pdf.

2. Hydration or hydroxylation: direct of fullerenol from pristine fullerene [C60] via acoustic cavitation in the presence of hydrogen peroxide.  Sadia Afreen,  Ken Kokubo,  Kasturi Muthoosamy  and Sivakumar Manickam, The Royal Society of Chemistrys, 2017, 7, 31930-31939 http://pubs.rsc.org/en/content/articlehtml/2017/ra/c7ra03799f)

3. C60(OH)60 .    . 05.02.2017  http://rusnor.org/pubs/articles/15067.htm

4. C60(OH)60 .  .., ii. ii , III i i i i ,  (.   31 2018.), 2 , . 2018, .80-83 http://www.cnp.org.ua/files/Archive/January_2018/Kiev_january_2018_part_2.pdf

5. C60(OH)60 .  .., Danish Scientific Journal No 9, 2018, Vol.1, CHEMICAL SCIENCES,  page 3-5 http://www.danscij.com/wp-content/uploads/2018/03/DSJ_9_1.pdf

6.   C60(OH)42 C60(OH)60 60 . .. Sciences of Europe, VOL 1, No 24, (2018), CHEMICAL SCIENCES, (Praha, Czech Republic), page 12-15  http://european-science.org/wp-content/uploads/2018/03/VOL-1-No-24-2018.pdf

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