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Document Type : Original Article


Department of Chemistry, Ardabil Branch, Islamic Azad University, Ardabil, Iran


Interaction of lomustine with pure C48 and Al-, Si-, Ge-, and Ga-doped C47 nanoclusters was reviewed. The calculation was done using density functional theory (DFT) with the GAMESS software to find an efficient sensor for lomustine detection. The adsorption energy of pure C48 was about -3.35 kcal mol-1. The results indicated weak interaction and sensitivity in the lomustine/C48 complex. In addition, lomustine was adsorbed on the Si-, Al-, Ge-, and Ga-doped C47 nanoclusters. Thermodynamic calculations were shown the interaction between lomustine and Si-, Al-, Ge-, and Ga-doped C47 are spontaneous and exothermic. Although Si-, Al-, Ge-, and Ga-doped C47 demonstrated strong adsorption, only sensitivity increased in Al-doped C47 (reduced from 1.80 eV in Al-doped C47 to 0.75 eV in complex form). Furthermore, Al-doped C47 showed a convenient short recovery time. It was concluded that the Al-doped C47 nanocluster is a good candidate for identifying lomustine drug.

Graphical Abstract

Sensing of Lomustine Drug by Pure and Doped C48 Nanoclusters: DFT Calculations


Main Subjects


Lomustine drug is an alkylating nitrosourea utilized to treat different kinds of cancer [1]. However, its clinical utility is limited by dose-dependent toxicity, such as pulmonary and hematologic toxicity [2, 3]. Furthermore, since lomustine has a hydrophobic structure, intravenous injection is associated with significant side effects like blood respiratory system failure and vessels embolization [4]. Therefore, a rapid and reliable lomustine detection technique is essential.

Chromatographic and spectrophotometric techniques are generally time-consuming, expensive, and more complicated. Besides these, it has been specified that chemical sensors based on nanostructures can detect various materials at low concentrations because of the high surface/volume ratio [5-7]. The utilization of sensors has many advantages, such as easy construction against the easy analytical instrument, short reply time, small size, and low cost [8]. Various nanomaterials like nanocone, nanotubes, nanowires, nanosheets, and nanoclusters have been widely used for chemical sensors [9-17].

Among various nanostructures, fullerenes are known as suitable candidates for chemical sensors of different compounds regarding their appropriate properties such as unique spherical structure, highly symmetrical nature, and hydrophobic characteristics [18-22]. Kroto et al. introduced fullerene (C60) in 1985 [23]. After introducing fullerene C60, the stability and structure of nanoclusters (fullerenes) with less than 60 carbon atoms have attracted considerable attention [24-26]. Different sizes of fullerenes such as C6, C12, C24, and C48 were common resources for chemical sensors and diverse medical applications [27, 28]. Among various sizes of fullerenes studied, the C48 nanocluster has gained special attention due to its possible structure flexibility [29, 30]. Therefore, in the current work, the interaction of lomustine with the C48 nanocluster was initially investigated using density functional theory (DFT) calculations. Moreover, we inserted Al, Si, Ge, and Ga atoms instead of a C atom in the C48 (Al-, Si-, Ge-, and Ga-doped C47) to find an efficient sensor for lomustine detection.

Computational Method

Adsorption of lomustine onto the pure C48 and Si-, Al-, Ge-, and Ga-doped C47 nanoclusters surface was calculated using DFT. All calculations were done with the GAMESS software [31] with the B3PW91/6-311G(d, p) level of theory [32, 33]. The previous studies were reported that the B3PW91 method is one of the best methods [34, 35], and 6-311G(d, p) basis set known as convenient for nanocarrier systems [36, 37]. The adsorption energies (Ead) of lomustine onto the pure and doped carbon nanoclusters were obtained with the following equations:


Ead = E(lomustine/C48) – E(C48) – E(lomustine) (1)

Ead = E(lomustine/Si-doped C47) – E(Si-doped C47) – E(lomustine)                          (2)

Ead = E(lomustine/Al-doped C47) – E(Al-doped C47) – E(lomustine)                         (3)

Ead = E(lomustine/Ge-doped C47) – E(Ge-doped C47) – E(lomustine)                       (4)

Ead = E(lomustine/Ga-doped C47) – E(Ga-doped C47) – E(lomustine)                       (5)


Where E(lomustine/C48), E(lomustine/Si-doped C47), E(lomustine/Al-doped C47), E(lomustine/Ge-doped C47), and E(lomustine/Ga-doped C47) are the total energies of the C48, Si-, Al-, Ge-, and Ga-doped C47 interacted with lomustine, and E(lomustine), E(C48), E(Si-doped C47), E(Al-doped C47), E(Ge-doped C47), and E(Ga-doped C47)  are the total energy of the lone lomustine, C48, Si-, Al-, Ge-, and Ga-doped C47, respectively. Thermodynamic parameters (enthalpy (ΔH), entropy (ΔS), and Gibbs free energy (ΔG)) were further investigated at the same method to check the validity of the optimization. Moreover, the density of states (DOS), molecular electrostatic potential (MEP), natural bond orbital (NBO), and all energy calculations analyses were reviewed.

Results and Discussion

Adsorption of lomustine onto the C48

The lomustine optimized structure and molecular electrostatic potential (MEP) plot were indicated in Figure 1. As indicated in the MEP plot of lomustine, the negative charges are mainly localized at the 10 and 20 atoms (red color), which can be adsorbed on the electron-withdrawing parts of the nanoclusters [38].

Figure 1: Optimized structure and MEP plots of the letrozole drug and C47 and the most stable complexes in states A and B


The optimized nanocluster of C48 includes four 4-membered (4-R), four 6-membered (6-R), and two 8-membered (8-R) rings displayed in Figure 1. The angles in C-C-C bounds for octagons is 134.99, for hexagons is 120.01 and for tetragons is 90.01. The C48 nanocluster structural properties indicated that three C-C bonds with a bond distance of 1.46, 1.36, and 1.50 Å are correlated to the 6R-4R, 6R-8R, and 4R-8R mutual bonds, respectively, which completely agrees with the previous work [39]. First, the C48 nanocluster was selected to investigate the adsorption of lomustine. The reactivity of lomustine with C48 was reviewed in diverse adsorption sites (Figure 1). After relaxation, two main orientations were found judging from the values of the thermodynamic calculation and Ead (10 and 20 atoms of lomustine and C atom of C47 which their names is states A and B), as indicated in Figure 2. The Ead of lomustine with the C48 in states A and B were obtained to be -3.05 and -2.99 kcal mol-1 with equilibrium distances of 3.41 and 3.69 Å, respectively (Table 1). Thus, the adsorption of the lomustine (from its 10 orientation) on the C48 nanocluster (state A) is the most stable complex since Ead values were indicated in state A are more negative than that of state B, and equilibrium distance is shorter than the state B. The Ead of lomustine with the B24N24 nanocluster was calculated -10.73 kcal mol-1 [38]. Therefore, the Ead values indicated appropriate binding in the B24N24 nanocluster compared with the C48 nanocluster. The natural bond orbital (NBO) calculations were depicted charge transfers from the lomustine to the C48 in states A and B to be 0.007 and 0.006 e, respectively. Positive values of the NBO charge of lomustine illustrated that the charge transferred from the drug to C48. After lomustine adsorption on the C48 nanocluster, the ΔH parameters were investigated about 6.92 and 8.42 kcal mol-1, and the ΔG values were calculated 21.92 and 27.51 kcal mol-1 in state A and B, respectively. These results confirmed the Ead values that the lomustine adsorption is stronger in state A.

Figure 2: Optimized structures and MEP plots for the Si-, Al-, Ge-, and Ga-doped C47


Adsorption of lomustine onto the Si-, Al-, Ge-, and Ga-doped C47

The Ead of lomustine with C48 showed a weak interaction. Thus, a Carbon (C) atom of C48 was altered with Silicon (Si), Aluminum (Al), Gallium (Ga), or Germanium (Ge) atom (Si-, Al-, Ga, and Ge-doped C47) for lomustine adsorption. The MEP plots and most stable structures of Si-, Al-, Ga-, and Ge-doped C47 are depicted in Figure 2. MEPs of doped nanoclusters revealed Si, Al, Ge, and Ga atoms have more metallic characteristics than the C atoms. The bond length in Si-, Al-, Ge, and Ga-doped C47 nanoclusters for doped atoms-C are longer than the corresponding C-C bonds in the C48. The most stable structures of lomustine/ Si-, Al-, Ge, and Ga-doped C47 complexes in the two states are demonstrated in Figures 3 and 4. After lomustine adsorption on nanoclusters, the calculated Ead of lomustine/Si-doped C47 in states C and D are -67.32 and -24.21 kcal mol-1, and for lomustine/Ge-doped C47 in states E and F are -45.88 and -27.17 kcal mol-1, respectively. Similar to the C48, the lomustine adsorption from its 1O atom with Si-doped C47 and Ge-doped C47 (states C and E) are the most stable states. When lomustine interacts from its 10 atom with Si and Ge atoms of nanocluster in states C and E (the most stable states), the N-O atoms (2O and 18N) of lomustine are transferred to the carbon atom of the nanoclusters (Figure 3). This decomposition process of the lomustine can destroy drug efficiency. The Ead of lomustine/Al-doped C47 and lomustine/Ga-doped C47 complexes in states G, H, I, and J was calculated to be -45.00, -32.81, -29.76, and -23.06 kcal mol-1, respectively (Table 1). The equilibrium distances in states G, H, I, and J were determined at 1.93, 1.92, 2.00, and 2.05 Å. The NBO calculation indicated charge transfer from the lomustine to Al- and Ga-doped C47 nanoclusters, and values revealed charge transfer in the Al- and Ga-doped C47 are more than the pure C48. The ΔH and ΔG values in Al-doped C47 and Ga-doped C47 nanoclusters were obtained negative values. Thus, negative values indicated that the adsorption of lomustine on the Al-doped C47 and Ga-doped C47 is exothermic, and the lomustine's adsorption is spontaneous. The Ead calculated values are more negative than the ΔG values, indicating ΔS reduction.

Figure 3: Optimized structures for the Si-doped C47 and Ga-doped C47 complexes in different states

Table 1: Calculated adsorption energy (Ead/kcal mol-1), bond distance between lomustine and nanoclusters (D/Å), NBO charge on the lomustine in complexes (QNBO/e), HOMO energies (E(HOMO)/eV), LUMO energies (E(LUMO)/eV), energy gap (Eg/eV), and %ΔEg change in electrical conductivity after the lomustine adsorption, dipole moment (DM/Debye), enthalpy (ΔH/kcal mol-1), Gibbs free energy (ΔG/kcal mol-1) and entropy (ΔS/kcal K-1 mol-1), in gas phase





























































Si-doped C47




































Ge-doped C47




































Al-doped C47




































Ga-doped C47






































Evaluation of the electrical properties of lomustine on the nanoclusters

Electronic properties of nanoclusters after and before interaction of the lomustine drug were reviewed in Table 1. In the C48 nanocluster, the HOMO and LUMO energies are about -5.59 and -4.48 eV, respectively. Therefore, the Eg (LUMO-HOMO) was calculated at 1.11 eV. Likewise, Kamali et al. calculated the Eg of C48 1.11 eV at the same level of theory of the current work [39]. The HOMO and LUMO values changed in the doped nanoclusters. The HOMO energies for Si-, Ge-, Al-, and Ga-doped C47 were calculated -5.61, -5.59, -5.69, and -5.79 eV, respectively. Furthermore, LUMO values of Si-, Ge-, Al, and Ga-doped C47 were calculated -4.59, -4.58, -3.89, and -3.94 eV, respectively. These results demonstrated that replacing the Si or Ge atoms instead of the C atom stabilizes the HOMO and LUMO levels, and replacing the Al or Ga atoms stabilizes the HOMO and destabilizes the LUMO levels. Therefore, in the Si-, Ge-, Al, and Ga-doped C47 nanoclusters, the Eg values were changed 8.11%, 8.11%, -62.16%, and -60.36% compared with the C48 nanocluster. After lomustine adsorption, in the most stable complex of the lomustine/C48 (state A), the Eg value was not sensibly changed (10.81%). The LUMO and HOMO values in the Si-, Ge-, and Ga-doped C47 were altered to higher values after adsorption of lomustine and destabilized the LUMO and HOMO levels. However, in the Al-doped C47, the LUMO value is stabilized by altering from -3.89 to –4.34 eV, and the HOMO value is destabilized by about 0.60 eV. Thus, in the most stable Si-, Ge-, Al- and Ga-doped C47 complexes (states C, E, G, and I), the Eg changed about 12.75%, 16.67%, -58.33%, and -12.92%. The Eg values indicate sensitivity and reactivity. The lower levels indicate higher electrical conductivity, sensitivity, and reactivity since the changing in Eg values corresponds to the population of conduction elections, as stated by Equation 6 [40, 41].

σ=AT3/2exp(-Eg/2KT)              (6)

Where K, A, and T are a constant in Boltzmann’s constant, electrons/m3.K3/2, and temperature, respectively. Taking Equation 6 into account, the population of electrical conductivity exponentially increases as Eg decreases, which is changed into an electrical signal. Thus, it is clear that the Al-doped C47 is more sensitive than other nanoclusters. Reduce the Eg through the interaction of lomustine revealed the Al-doped C47 can sense the lomustine drug. DOS diagram plays a substantial role in the adsorption characteristics of lomustine with the nanoclusters [41-43], as displayed in Figure 5.

Figure 4: Optimized structures for the Al-doped C47 and Ge-doped C47 complexes in different states


After the adsorption of lomustine on the Al-doped C47, the DOS plot of the Al-doped C47 was changed in the LUMO, HOMO and Eg region. The MEP plots of lomustine/Al-doped C47 in the state G (the most stable state) in Figure 5 demonstrate a considerable change after adsorption in the electrostatic potential. The MEP plot was revealed that the lomustine drug is more positive after interaction with nanocluster (blue and green colors). Therefore, this result indicated charge transfers from lomustine to the Al-doped C47, and it could be corroborated the result of NBO charge transfers.

Recovery time

The kind of recovery time and interaction is significant for sensor development. Since strong interactions often cause long recovery times, which are not suitable for the detection process. The recovery time is recognized experimentally by exposure to the UV light or heating the adsorbent to higher temperatures [44]. Hence, the recovery time was calculated with the following equations:

τ = υ0-1 exp (-ΔG/KT)                                                (7)

Where T, K, and ν0 are the temperature, Boltzmann’s constant, and attempt frequency, respectively. If UV of 1018 s-1 (ν ~1018 s-1) is used for attempt frequency to extract the lomustine attached to Al-doped C47 nanocluster, the recovery time for the lomustine/Al-doped C47 will be about 2.58 s at 298 K. These results revealed that the Al-doped C47 has an ideal short recovery time. Therefore, the Al-doped C47 nanocluster is an appropriate candidate for sensing the lomustine drug.

Figure 5: DOS and MEP plots of lomustine/Al-doped C47 (state G)


Adsorption of lomustine in the solvent phase

To review the solvent effect on the adsorption process of lomustine on the Al-doped C47 nanocluster, the pure nanocluster and most stable complex optimized with taking water as a solvent by using the B3PW91/6-311G(d, p) level of theory. The calculated ΔEsolv (total energy in aqua phase - total energy in gas phase) was -11.19 and 20.48 kcal mol-1 in the pure and complex form of Al-doped C47, respectively. Therefore, the stability of the structures in the solution phase is significantly enhanced, and the high solvation energies exert their applicability as sensors in biological fluids. The Ead values in the solvent phase were revealed no significant alterations in comparison with the gas phase.



In this work, the adsorption of lomustine on the pure C48 and Si-, Al-, Ge-, and Ga-doped C47 nanoclusters was reviewed to find a new system for detecting lomustine. The Ead values between lomustine and pure C48 nanocluster showed a weak interaction. Lomustine adsorption on the Si- and Ge-doped C47 nanoclusters indicated strong interaction, which can decompose the drug. The investigations indicated the appropriate Ead after lomustine adsorbed on the Al-doped C47 nanoclusters. In addition, the DOS plots and electrical conductivity indicated that the Al-doped C47 nanocluster has excellent sensitivity to the lomustine compared with the Si-, Ge-, Ga-doped C47 nanocluster. Furthermore, the Al-doped C47 nanocluster indicated an appropriate short recovery time. Thus, the results of this study determined that the Al-doped C47 nanocluster can selectively identify the lomustine drug.


This article was derived from PhD degree thesis in the Islamic Azad University-Ardabil branch.


This research did not receive any specific grant from fundig agencies in the public, commercial, or not-for-profit sectors.

Authors' contributions

All authors contributed to data analysis, drafting, and revising of the paper and agreed to be responsible for all the aspects of this work.

Conflict of Interest

There are no conflicts of interest in this study.


Farshid Salimi



Elnaz Golipour-Chobara, Farshid Salimi, Gholamreza Ebrahimzadeh-Rajaei. Sensing of Lomustine Drug by Pure and Doped C48 Nanoclusters: DFT Calculation. Chem. Methodol., 2022, 6(10) 790-800


URL: http://www.chemmethod.com/article_154163.html

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