This overview described the utilization of porphyrins as active compound in the design of different types of sensors. The modified electrodes with porphyrins showed a new approach in sensing of different compounds such as biogenic amines, vitamins, toxic and polyphenolic compounds, biomarkers. The porphyrins had many applications due to their large surface area, redox mediators, regular porosity and tunable structures, making them suitable for detecting small molecules. Different electrochemical and optical sensors were designed and applied successfully for clinical, food, and environmental analysis.

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Graphene nanosheets (EGr) were electrochemically prepared through one-step exfoliation of a graphite rod in a mixture of HSO:HNO (3:1) at low bias (4 V). Subsequently, gold nanoparticles were attached to the graphene surface (EGr-Au) by the reduction of the metal precursor (HAuCl) in aqueous solution containing dispersed graphene sheets. According to the XRD investigation, the synthesized material consists of a mixture of few-layer (86%) and multi-layer (14%) graphene. The interlayer distance was found to be in the range of 0.466-0.342 nm, which is larger than the interlayer distance in graphite (0.335 nm). The average size of gold nanoparticles in the EGr-Au sample was 24 nm, in excellent agreement with the TEM results. The synthesized material was then employed to modify a glassy carbon (GC) substrate, in order to obtain a modified electrode (GC/EGr-Au). Next, the electrochemical behavior of hydroquinone (HQ) in the presence and absence of interfering species, catechol (CAT) and bisphenol A (BPA) was studied and the corresponding calibration curves were plotted. Thus, in solutions without interfering species, the GC/EGr-Au electrode has a wide linear range (3 × 10-10 M), high sensitivity (0.089 A M) and low detection limit (LOD = 10 M; S/N = 3). The presence of either catechol or bisphenol A leads to the increase of LOD to 2 × 10 M, and in addition changes the electrode sensitivity, up to 0.146 A M.

Butaclamol is an antipsychotic drug used in the treatment of schizophrenia. The macrocyclic antibiotics, vancomycin and teicoplanin, are proposed as chiral selectors for the design of the enantioselective, potentiometric membrane electrodes (EPMEs) for the assay of (-)butaclamol. The slopes of the electrodes are near-Nernstian for the assay of (-) butaclamol with linear concentration ranges between 10(-10) and 10(-7) mol/L and between 10(-9) and 10(-7) mol/L for vancomycin and teicoplanin based EPMEs. Limits of detections varied. The electrodes were used reliably for the enantioanalysis of (-) butaclamol in serum samples.