In this paper functionalized multiwall carbon nanotubes (FMWCNT) were modified using atenolol as a class of drugs that were used in cardiovascular diseases containing reactable nitrogen, which could attach chemically to functionalized MWCNT. This product was characterized by Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy. These spectrums proved the existence of nitrogen atoms of amide due to new functional group. The morphology were also determined by scanning electron microscopy (SEM) and showed that this product was synthesized in the nanometer dimension. Thermal gravimetery (TGA) analysis was also used to evaluate thermal properties.
In recent years attentions from researchers have been focused on carbon nanotubes (CNTs) due to their size, properties and their electronic, mechanical, optical, and chemical characteristics [
We know that the presence of different functional groups is the starting point for binding a variety of different chemical molecules onto the nanotube surfaces. The aim of this study is the linkage of atenolol as a drug containing an amine group with FMWCNTs as illustrated in Scheme 2.
Carboxylated multiwall carbon nanotube (MWNT-COOHs) (95% purity, 20 - 30 nm) was used in this work were purchased from nanocarbon Co. Thionyl chloride (SOCl2), THF and DMF from fluka and atenolole were purchased from Aldrich and used as received. Deionized water was also used. Fourier transform infra red (FT- IR) spectrum was recorded using KBr tablets on a Perkin Elmer Spectrum-100 FT-IR spectrometer. Raman spectra recorded on Bruker Sentrra-2009 spectrometer. Scanning electron microscope (SEM) was used to study the morphology of the MWNTs. SEM measurement was carried out on the Hitachi 4160 Electron Microscope. And thermal gravimetery (TGA) was also carried out with ASTME-1131 apparatus.
100 mg of MWCNT-COOH were dispersed in 30 mL of thionyl chloride, then 1 mL of THF added to the vessel and sonicated for 2 hours at room temperature. Then refluxed in 70˚C by mixing for 54 hours. The residue thionyl chloride were removed in vacuum by rotary evaporation. Then filtered and washed with THF, the solids were dried in an oven overnight, in this step the surface-bound of carboxylic acid groups were converted into acyl chloride groups. 80 mg of this solid ( MWCNT-COCl) were mixed with 25 mL of DMF and 200 mg of atenolol were added and ultrasonicated for one hours. The mixture were refluxed in 90˚C for 72 hours, then cooled to room temperature, filtered and washed with DMF, ethanol and THF, so the residue were dried in an oven for overnight and the solid (modified MWCNT with atenolol) was ready for more evaluations.
Scheme 1. (RS)-2-{4-[2-Hydroxy-3-(propan-2-ylamino) propoxy] phenyl} acetamide.
Scheme 2. Strategy for modified FMWCNT synthesis.
3.1. FT-IR Characterization
FT-IR spectra of atenolol is illustrated in
As described in experimental section caroxylated MWCNT was reacted with thionyl chloride to change the acidic functional groups to acyl clorides. The IR spectrums of these two compounds are illustrated in
In
In
FT-IR spectrum of pure atanolol
FT-IR spectrum of MWNT-COOH
FT-IR spectrum of MWNT-COCl
FT-IR spectrum of modified FMCNT with atenolol
shifted from 1721 to 1709 and the peak at 1180 cm−1 is assigned to the C-N stretching of amide group. The peak at 3400 cm−1 is also for stretching vibration of N-H [
Raman spectra results are powerful tool for characterizing functionalized CNTs. The disorder D band in MWCNTs is observed when the symmetry of hexagonal lattice is disrupted due to, for example, covalent side- wall functionalization. The G mode at around 1600 cm−1 represents the tangential vibration mode of the graphitic structure of the nanotubes. As shown in the spectra from
Since Raman scattering is strongly sensitive to the electronic structure so the Raman data in
Characteristic bands of raman spectra for MWCNT-COOH; MWCNT-COCl and FMWCNT-atenolol
Comparison of ID/IG ratio values in MWCNT-COOH; MWCNT-COCl and FMWCNT-atenolol
The morphology of the compounds were investigated by SEM and are shown in
3.4. Thermo Gravimetric Analysis (TGA)
Thermo gravimetric analysis (TGA) is a widly used technique for determining the thermal resistance of materials, so in this paper the enhancement of thermal stability for nano compounds are investigated. In
SEM images of the FMWCNT and FMWCNT-atenolol
TGA curve of pristine FMWCN
TGA curve of FMWCNT-atenolol
In summary, atenolol was successfully attached to MWCNTs surface by chemical functionalization. The modified functionalized MWCNTs obtained were evaluated, using TGA, FT-IR, SEM and Raman spectroscopy. SEM images showed the formation of the FMWCNT-atenolol and presence of the chemical bonding the matrix. FT-IR results showed the formation of amide in the products and finally the thermo gravimetric analysis (TGA) analysis data has shown the presence of the functional groups attached to the surface of MWCNT and their corresponding degradation with increasing temperature in inert atmosphere.
This work was supported by Islamic Azad University.