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

A functionalized cellulose filter, with iminodiacetate chelating units, has been characterized for the uptake of ultratrace Pb(II) (1 to 10−6 mg · l−1) with the use of210Pb. The different behaviour in batch and in flow-through experiments has been observed both in the rate of metal uptake, as well as in the relative yield of metal recovery. Flow-through uptake appeared to be a faster process and to occur with higher % yield in the entire range investigated. A radioanalytical method for the determination of Pb(II) in liquid samples (10 to 10−2 mg · l−1) has been developed, based on the measurement of the210Pb activity exchanged between a iminodiacetic acid filter loaded with210Pb and the solution under analysis. Results and interferences are considered and discussed.

A RADIOANALYTICAL METHOD FOR THE DETERMINATION OF Pb(II) WITH THE USE OF A CHELATING CELLULOSE FILTER

The stoicheiometries and kinetics of the silver(II) oxidation of formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, and pivaldehyde have been investigated at 8.0, 14.0, and 22.0 °C in aqueous perchloric acid media (1.00 ⩽[HClO4]⩽ 4.00M; µ 4.0M). The kinetics were monitored by a stopped flow technique. The reactions occur with the stoicheiometry H2O + 2AgII+ RCHO → 2AgI+ 2H++ RCOOH. The rate-determining step is first order in each reactant, and involves both Ag2+ and AgOH+ species. No direct evidence for complex formation between the reactants was obtained. The results are discussed with reference to enolization and hydration equilibria of the substrates. gem-Diol forms of the aldehydes are suggested as the active species.

Kinetics of oxidation of organic compounds by silver(II) in aqueous perchloric acid solution. Part 3. Aliphatic aldehydes

The kinetics and mechanism of the silver(II) oxidation of methanol, ethanol, 1-propanol, 1-methyl- ethanol, 1-butanol, 2-methyl-1-propanol, 2-butanol, 2-methyl-2-propanol, D4-methanol, and D6-methanol have been investigated at 8.0 and 20.0°C in aqueous perchloric acid media (1.00 ≤ [HClO4] ≤ 4.00M; μ = 4.0M). The kinetics were monitored by following the disappearance of Ag(II) with a spectrophotometric stopped-flow technique. The reactions are first order in each reactant and involve both Ag2+ and AgOH+ species. No kinetic or spectroscopic evidence for complex formation between reactants was obtained. The results are discussed with reference to electron density on the OH or αC-H substrate sites and to the isotopic hydrogen/deuterium rate quotients found for methanol and ethanol.

Kinetics of oxidation of organic compounds by silver(II) in aqueous perchloric acid solution. IV. Aliphatic alcohols

If sulfonato ligands are to be used in metal ion preconcentration techniques based on ion-exchange, the chelate stability constant must be available. An ion-exchange procedure is described for the determination of the stability constants for some metal-Plasmocorinth B complexes. The results are compared with those obtained spectrophotometrically. log K values are in good agreement for two methods. The enrichment of anionic complexes is obtained with an ion-exchange procedure.

Ion Exchange for the Determination of Stability Constants of Metal- Plasmocorinth B Complexes and Preconcentration Procedure

The kinetics and mechanism of oxidation of a series of alcohols, namely cyclohexanol, cyclopentanol, pentan-2-ol and benzyl alcohol, by silver(II) perchlorate in perchloric acid solution. have been investigated by the stopped-flow technique. These oxidations proceed through two parallel pathways involving Ag2+ and AgOH+ species. In the case of benzyl alcohol, the hydroxo species, which has been found to be almost universally reactive toward different organic substrates, is inactive; this behaviour has been interpreted in terms of interaction of the oxidant with the aromatic moiety in the alcohol. The reactivities are discussed in terms of substrate reaction sites with reference to electronic availability and reaction products.

Edoardo Mentasti

Papers

A RADIOANALYTICAL METHOD FOR THE DETERMINATION OF Pb(II) WITH THE USE OF A CHELATING CELLULOSE FILTER

Kinetics of oxidation of organic compounds by silver(II) in aqueous perchloric acid solution. Part 3. Aliphatic aldehydes

Kinetics of oxidation of organic compounds by silver(II) in aqueous perchloric acid solution. IV. Aliphatic alcohols

Ion Exchange for the Determination of Stability Constants of Metal- Plasmocorinth B Complexes and Preconcentration Procedure

Kinetics of oxidation of organic compounds by silver(II) in aqueous perchloric acid solution. Part 5