https://zenodo.org/record/1258475/files/article.pdf

Electron transfers in chemistry and biology

Detection of chemical and biological agents plays a fundamental role in biomedical, forensic and environmental sciences1–4 as well as in anti bioterrorism applications.5–7 The development of highly sensitive, cost effective, miniature sensors is therefore in high demand which requires advanced technology coupled with fundamental knowledge in chemistry, biology and material sciences.8–13

In general, sensors feature two functional components: a recognition element to provide selective/specific binding with the target analytes and a transducer component for signaling the binding event. An efficient sensor relies heavily on these two essential components for the recognition process in terms of response time, signal to noise (S/N) ratio, selectivity and limits of detection (LOD).14,15 Therefore, designing sensors with higher efficacy depends on the development of novel materials to improve both the recognition and transduction processes. Nanomaterials feature unique physicochemical properties that can be of great utility in creating new recognition and transduction processes for chemical and biological sensors15–27 as well as improving the S/N ratio by miniaturization of the sensor elements.28

Gold nanoparticles (AuNPs) possess distinct physical and chemical attributes that make them excellent scaffolds for the fabrication of novel chemical and biological sensors (Figure 1).29–36 First, AuNPs can be synthesized in a straightforward manner and can be made highly stable. Second, they possess unique optoelectronic properties. Third, they provide high surface-to-volume ratio with excellent biocompatibility using appropriate ligands.30 Fourth, these properties of AuNPs can be readily tuned varying their size, shape and the surrounding chemical environment. For example, the binding event between recognition element and the analyte can alter physicochemical properties of transducer AuNPs, such as plasmon resonance absorption, conductivity, redox behavior, etc. that in turn can generate a detectable response signal. Finally, AuNPs offer a suitable platform for multi-functionalization with a wide range of organic or biological ligands for the selective binding and detection of small molecules and biological targets.30–32,36 Each of these attributes of AuNPs has allowed researchers to develop novel sensing strategies with improved sensitivity, stability and selectivity. In the last decade of research, the advent of AuNP as a sensory element provided us a broad spectrum of innovative approaches for the detection of metal ions, small molecules, proteins, nucleic acids, malignant cells, etc. in a rapid and efficient manner.37



Figure 1

Physical properties of AuNPs and schematic illustration of an AuNP-based detection system.



In this current review, we have highlighted the several synthetic routes and properties of AuNPs that make them excellent probes for different sensing strategies. Furthermore, we will discuss various sensing strategies and major advances in the last two decades of research utilizing AuNPs in the detection of variety of target analytes including metal ions, organic molecules, proteins, nucleic acids, and microorganisms.

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Gold nanoparticles in chemical and biological sensing.

The science of the total environment

Recent developments in polysaccharide-based materials used as adsorbents in wastewater treatment

Direct And Mediated Anodic Oxidation of Organic Pollutants

Mechanism of oxidation of catechols by Mn(III) in aqueous acidic perchlorate media

Chromatographic behaviour of triazine compounds

Evaluation of stability constants of metal complexes with sulphonated azo-ligands.

Reactions between iron(iii) and catechol (o-dihydroxybenzene) part 1, equilibria and kinetics of complex formation in aqueous acid solution

The kinetics and mechanism of oxidation of adrenalin, L-dopa, and dopamine to the corresponding open-chain o-benzoquinones with periodic acid have been investigated in the pH range 0–7, at different temperatures. The reactions are of the first order in each reagent and are strongly dependent on pH. Possible mechanisms are discussed with reference to previous work on oxidation with periodic acid and the variation of the rate as a function of pH has been explained in terms of differently protonated reagent couples. At pH >4, the substituted o-benzoquinones rearranged with cyclization of the side-chain into the corresponding leuco-aminochromes (5,6-dihydroxy-2,3-dihydroindoles), which are then rapidly oxidized to aminochromes (2,3-dihydroindole-5,6-quinones). The rate law is, in the pH range 4–8, in the form kobs=kcK′1/(K′1+[H+]), where K′1 is the acid dissociation constant of the ammonium group of the side-chain, thus predicting that for pH >9 only the cyclization rates are nearly independent of pH. The cyclization rates have been found to decrease significantly in the order adrenalin L-dopa > dopamine.

Edoardo Mentasti

Papers

Mechanism of oxidation of catechols by Mn(III) in aqueous acidic perchlorate media

Chromatographic behaviour of triazine compounds

Evaluation of stability constants of metal complexes with sulphonated azo-ligands.

Reactions between iron(iii) and catechol (o-dihydroxybenzene) part 1, equilibria and kinetics of complex formation in aqueous acid solution

Kinetics and mechanism of oxidation pathways of some catecholamines with periodic acid