**2.2 Fullerene derivatives and chemical reactions**

The most isomerically found types of fullerene derivatives are C60 and C70 fullerenes. These derivatives can only be dissolved in highly non-polar liquids such as toluene and benzene. Thanks to this hydrophobic property, it can be used as a drug carrier, intercalator or modification material in hydrophobic layers as lipid layers. In computer studies about fullerene, solubility attempts that were made in 75 different solvents were examined [11].

Although it is possible to dissolve in different solvents, surface modification of fullerenes for biosensor and sensor technology is the most effective way to use fullerene. The solubility in water can be achieved by being modified with polar groups. The method developed by Hirsch and colleagues, fullerene was modified by 18 carboxyl groups, gained solubility in water as 34 mg/mL at pH = 7.4 [12]. In these studies, a nucleophilic cyclopropanation procedure was performed; the protection was removed with the help of bis-(polyamide)-malonate dendrimer; and 18 carboxyl groups were created (**Figure 2**). With this modification, a material, which can be used as an advantage in water solubility for modification of the carboxyl group, especially for sensor and biosensor technology, is obtained. With the activation of EDC/NHS, 18 carboxyl groups can be made to bind the amino group or a fullerene nanomaterial containing carboxyl groups can be modified on an amino group-modified transducer.

In another study, Cusan and his colleagues synthesized three ethylene glycol and three ammonium groups in poly charged fullerene-pyrrolidone derivatives [13]. In this study, which was carried out on two strategies, 2,2′-(ethylenedioxy)diethylamine was reacted by amino esterification with benzyl bromoacetate. Subsequently, the substance was interacted with carboxylate groups on fullerene to obtain fulleropyrrolidine in toluene. In this method, the authors have shown that purification is difficult and yield is low. For fullerene-PEG, in terms of biosensor and sensor technology, the fullerene derivative has two different arms with an amino group that can be used for modification by activating amino groups with glutaraldehyde a cross linker (**Figure 3**).

Fullerene modifications can be carried out entirely through the modification of the C = C bonds on fullerene. Fullerene modifications and derivatives of these modifications are seen in several studies. Accordingly, fullerene can be used to develop biosensors and sensors after being modified [14].

Apart from their use for modification material, another interesting feature of fullerene and fullerene-like materials is their photocatalytic advantage. The C60 shows a semiconductor-diode-like behavior and shows photo activity when

**Figure 2.** *Poly-carboxylated (18) fullerene.*

**65**

*Fullerene Based Sensor and Biosensor Technologies DOI: http://dx.doi.org/10.5772/intechopen.93316*

illuminated at a value close to 1.4 eV [1]. This photocatalytic feature shows that it

In conclusion, due to its catalytic properties, the use of fullerene is not only used as an immobilization material but also it is used in biosensor and sensor systems.

Sensor and biosensor technology is an important start line in the development of miniature analyzers. This technology is divided into two classes depending on the interaction of the sensor and analyte molecule: if the analyte molecule is transformed on the sensor surface called as catalytic based and if the analyte interacts with the surface called affinity-based sensors and biosensors [5]. The measurement can be performed electrochemically, optically, and piezoelectrically. In electrochemical sensors, electrodes are used as transducers. Different types of electrodes can be used according to the modification and measurement principle. The electrodes can be gold, carbon, platinum, and their derivatives. It is desired to create a modification layer over self-assembly monolayer; thiol containing chemicals can be used for gold and gold derivative electrodes [15]. Carbon derivative electrodes can be used for polymer production and adsorption type studies [16]. Thus, measurement is carried out with electrodes modified with the immobilized recognition agent. If the recognition agent is a catalytic agent (enzyme or nanoparticle), the electroactive species are released as a result of the target molecule that is transformed by recognition receptor. The method of measurement may also vary depending on the type of these species. For example, an amperometric technique is used if an electroactive species is formed, or a potentiometric measurement method is used if an ion is formed. In addition, interaction-based measurement is desired without a reaction between the analyte molecule and the recognition receptor on the electrode surface (DNA, antibody, MIP, polymer, etc.), and impedimetric

Optically designed sensor and biosensor systems use optic systems with optic sensitivity as transducers or surface plasmon resonance systems, which are a highly sensitive system that is used quite frequently today with laser canteen systems. The photons detected by the transducer with chemical reaction light sensing capability that occurs in optic systems can be converted into meaningful signals. In cantilever systems, measurement is performed by creating differences in the angle of the reflected laser signal as a result of the analyte molecule, which is attached to the surface of the cantilever, whose laser signal is reflected under a lever, changes the oscillation of the lever [19]. In surface plasmon resonance type sensors, the laser signal reflected behind the gold bit surface changes with the binding of the target molecule to the dielectric constant of this gold surface [20]. Here, too, the main purpose is the interaction between the analyte molecule and the recognizing receptor. If there is a catalytic effect, a photon sensing transducer, if there is an affinity-based measurement, cantilever or SPR sen-

Apart from these two techniques, piezoelectric systems, which are mass detection systems, can be designed as affinity-based instead of catalytic in biosensor and sensor systems. The method principle is the analyte molecule interacts with piezoelectric crystals used as transducers can generate signals by changing the oscillation

In conclusion, the interaction between the target molecule and the recognition receptor on sensor and biosensor systems can be measured with electrical, optic, and piezoelectric systems. The important point in these measurements is the characteristic of the modification layer on which the recognizing receptor is

can be used as a photo catalyst in optical sensors and biosensors.

**3. Fullerene-modified sensors and biosensors**

techniques can be used [15, 17, 18].

sor systems are used.

of the piezoelectric systems [21].

**Figure 3.** *Poly-charged fullerene derivative.*

*Smart Nanosystems for Biomedicine, Optoelectronics and Catalysis*

develop biosensors and sensors after being modified [14].

cross linker (**Figure 3**).

In another study, Cusan and his colleagues synthesized three ethylene glycol and three ammonium groups in poly charged fullerene-pyrrolidone derivatives [13]. In this study, which was carried out on two strategies, 2,2′-(ethylenedioxy)diethylamine was reacted by amino esterification with benzyl bromoacetate. Subsequently, the substance was interacted with carboxylate groups on fullerene to obtain fulleropyrrolidine in toluene. In this method, the authors have shown that purification is difficult and yield is low. For fullerene-PEG, in terms of biosensor and sensor technology, the fullerene derivative has two different arms with an amino group that can be used for modification by activating amino groups with glutaraldehyde a

Fullerene modifications can be carried out entirely through the modification of the C = C bonds on fullerene. Fullerene modifications and derivatives of these modifications are seen in several studies. Accordingly, fullerene can be used to

Apart from their use for modification material, another interesting feature of fullerene and fullerene-like materials is their photocatalytic advantage. The C60 shows a semiconductor-diode-like behavior and shows photo activity when

**64**

**Figure 3.**

**Figure 2.**

*Poly-carboxylated (18) fullerene.*

*Poly-charged fullerene derivative.*

illuminated at a value close to 1.4 eV [1]. This photocatalytic feature shows that it can be used as a photo catalyst in optical sensors and biosensors.

In conclusion, due to its catalytic properties, the use of fullerene is not only used as an immobilization material but also it is used in biosensor and sensor systems.
