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

The chromatographic behaviour of Cu(II), Fe(II), Ni(II) and Co(II) complexes with 4-(2-pyridylazo)resorcinol was studied. The experimental results were very sensitive even to less obvious operational parameters like the kind of the cation (sodium or ammonium) of the phosphate salt used as buffer. The puzzling pattern of the data obtained was interpreted in terms of the equations formulated by Horvath's ‘olvophobic” theory which correlates the capacity factors of the solutes with the surface tension of the mobile phase. A satisfactory rationalization of the data was obtained together with qualitative information on the stoichiometry and charge state of metal complexes. Useful suggestions about the direction to address the experimental work in order to obtain the best results was also obtained.

Reversed-phase HPLC behaviour of metal complexes with 4-(2-pyridylazo) resorcinol. A detailed study in the light of solvophobic theory

Simultaneous kinetic determination of uric acid ascorbic acid mixtures

A kinetic method for the analytical determination of binary mixtures of gallium and indium in liquid samples is described. The method is based on the spectrophotometric determination of the variation in absorbance connected with the displacement of a metallochromic ligand from the metal ions to be determined. The different reaction rates of gallium and indium enable the single metals to be distinguished and to be determined down to concentrations of 0.2 µg ml–1, in binary mixtures. Determinations in water samples from the River Po have been performed with satisfactory accuracy and precision. Standard deviations were around 4–5%, and mean relative errors were around 5–7%.

Simultaneous stopped-flow kinetic determination of gallium and indium by a ligand substitution reaction

The oxidation kinetics of some quinols with cobalt(III) perchlorate have been investigated at different temperatures and acidities by means of a stopped-flow technique. The rate law is of the form –½d [CoIII]/dt=(ka+kbKh[H+]–1)[ CoIII][Quinol]; the term ka refers to Co3+(aq) and kb to[Co(OH)]2+(aq) specjes. For Co3+(aq), comparison has been made with other systems in the light of the Marcus theory: a large number of reaction rates agree with an experimental correlation oftheformk =αZexp(–ΔG*/RT), where α= 10–5–10–6 and ΔG*=λ[1 +(δG⊖/λ)2]/4, according to Marcus theory. However, the small range of values of the second-order rate constants for [CO(OH)]2+(aq) suggests a limiting behaviour for this species.

Edoardo Mentasti

Papers

Reversed-phase HPLC behaviour of metal complexes with 4-(2-pyridylazo) resorcinol. A detailed study in the light of solvophobic theory

Simultaneous kinetic determination of uric acid ascorbic acid mixtures

Simultaneous stopped-flow kinetic determination of gallium and indium by a ligand substitution reaction

Kinetics and mechanisms of oxidation of reversible organic systems with cobalt(III) in acidic perchlorate media

Kinetic spectrophotometric determination of chloride and bromide at low concentrations