Layer-by-Layer Thin Film of Iron Phthalocyanine as a Simple and Fast Sensor for Polyphenol Determination in Tea Samples

Recent Advances in Analytical Methods for Determination of Polyphenols in Tea: A Comprehensive Review

Polyphenols, the most abundant components in tea, determine the quality and health function of tea. The analysis of polyphenols in tea is a topic of increasing interest. However, the complexity of the tea matrix, the wide variety of teas, and the difference in determination purposes puts forward higher requirements for the detection of tea polyphenols. Many efforts have been made to provide a highly sensitive and selective analytical method for the determination and characterization of tea polyphenols. In order to provide new insight for the further development of polyphenols in tea, in the present review we summarize the recent literature for the detection of tea polyphenols from the perspectives of determining total polyphenols and individual polyphenols in tea. There are a variety of methods for the analysis of total tea polyphenols, which range from the traditional titration method, to the widely used spectrophotometry based on the color reaction of Folin–Ciocalteu, and then to the current electrochemical sensor for rapid on-site detection. Additionally, the application of improved liquid chromatography (LC) and high-resolution mass spectrometry (HRMS) were emphasized for the simultaneous determination of multiple polyphenols and the identification of novel polyphenols. Finally, a brief outline of future development trends are discussed.

Evaluation of Antioxidants Using Electrochemical Sensors: A Bibliometric Analysis

The imbalance of oxidation and antioxidant systems in the biological system can lead to oxidative stress, which is closely related to the pathogenesis of many diseases. Substances with antioxidant capacity can effectively resist the harmful damage of oxidative stress. How to measure the antioxidant capacity of antioxidants has essential application value in medicine and food. Techniques such as DPPH radical scavenging have been developed to measure antioxidant capacity. However, these traditional analytical techniques take time and require large instruments. It is a more convenient method to evaluate the antioxidant capacity of antioxidants based on their electrochemical oxidation and reduction behaviors. This review summarizes the evaluation of antioxidants using electrochemical sensors by bibliometrics. The development of this topic was described, and the research priorities at different stages were discussed. The topic was investigated in 1999 and became popular after 2010 and has remained popular ever since. A total of 758 papers were published during this period. In the early stages, electrochemical techniques were used only as quantitative techniques and other analytical techniques. Subsequently, cyclic voltammetry was used to directly study the electrochemical behavior of different antioxidants and evaluate antioxidant capacity. With methodological innovations and assistance from materials science, advanced electrochemical sensors have been fabricated to serve this purpose. In this review, we also cluster the keywords to analyze different investigation directions under the topic. Through co-citation of papers, important papers were analyzed as were how they have influenced the topic. In addition, the author’s country distribution and category distribution were also interpreted in detail. In the end, we also proposed perspectives for the future development of this topic.

A hybrid boronate affinity probe for the selective detection of cis-diols containing compounds in tea beverages

UiO-66-NH₂ nanocomposite was post-modified with 4-mercaptophenylboronic acid (MPBA) by the method of in-situ hybridization reaction. The hybrid boronate affinity material UiO-NH₂ @P (TEPIC-co-MPBA) was characterized by Scanning electron microscope, X-ray diffraction, Fiurier transform infrared spectroscopy. It was applied as fluorescent probe for the detection of cis-diols containing compounds based on the boronate affinity mechanism, and exhibited high specific selectively. The proposed method exhibited good liearnity for the detection of catechol in the range of 0.50-8.00 μg·mL^-1 . The detection limit was 0.13 μg·mL^-1 . The tactic was successfully applied to analyze the total polyphenols in tea beverages for catechol, and relative recovery was in 98.86-106.00%. Therefore, this work provided a promising strategy for recognization of cis-diols containing compounds.

Electrochemical Sensors and Biosensors for the Analysis of Tea Components: A Bibliometric Review

Tea is a popular beverage all around the world. Tea composition, quality monitoring, and tea identification have all been the subject of extensive research due to concerns about the nutritional value and safety of tea intake. In the last 2 decades, research into tea employing electrochemical biosensing technologies has received a lot of interest. Despite the fact that electrochemical biosensing is not yet the most widely utilized approach for tea analysis, it has emerged as a promising technology due to its high sensitivity, speed, and low cost. Through bibliometric analysis, we give a systematic survey of the literature on electrochemical analysis of tea from 1994 to 2021 in this study. Electrochemical analysis in the study of tea can be split into three distinct stages, according to the bibliometric analysis. After chromatographic separation of materials, electrochemical techniques were initially used only as a detection tool. Many key components of tea, including as tea polyphenols, gallic acid, caffeic acid, and others, have electrochemical activity, and their electrochemical behavior is being investigated. High-performance electrochemical sensors have steadily become a hot research issue as materials science, particularly nanomaterials, and has progressed. This review not only highlights these processes, but also analyzes and contrasts the relevant literature. This evaluation also provides future views in this area based on the bibliometric findings.

Phthalocyanine Modified Electrodes in Electrochemical Analysis

Phthalocyanines are aromatic or macrocyclic organic compounds and attract great attention due to their numerous properties. They have many high-tech applications in different areas of the industry such as dyestuffs, thermal printing screens, photovoltaic solar cells, membrane catalytic reactors, semiconductor materials and gas sensors. In the last decade, electrochemical sensor studies have accelerated with the catalytic lighting. It plays a dominant role in the development and implementation of new generation sensors. The aim of this study is to review the electrochemical methods based on electrode modification with phthalocyanines and to shed light on new application areas of phthalocyanines. The focal point was based on the sensor applications of phthalocyanines in the determination of drugs, pesticides, organic materials and metals etc. by electrochemical methods. Experimental conditions and some validation parameters of the sensor applications such as metal phthalocyanine types, indicator electrodes, selectivity, working ranges, detection limits, and analytical applications were discussed. Consequently, this is the first review dealing with the applications of phthalocyanines in electrochemical sensors for the sensitive determination of analytes in a variety of matrices.

Biosensors Platform Based on Chitosan/AuNPs/Phthalocyanine Composite Films for the Electrochemical Detection of Catechol. The Role of the Surface Structure

Biosensor platforms consisting of layer by layer films combining materials with different functionalities have been developed and used to obtain improved catechol biosensors. Tyrosinase (Tyr) or laccase (Lac) were deposited onto LbL films formed by layers of a cationic linker (chitosan, CHI) alternating with layers of anionic electrocatalytic materials (sulfonated copper phthalocyanine, CuPcS or gold nanoparticles, AuNP). Films with different layer structures were successfully formed. Characterization of surface roughness and porosity was carried out using AFM. Electrochemical responses towards catechol showed that the LbL composites efficiently improved the electron transfer path between Tyr or Lac and the electrode surface, producing an increase in the intensity over the response in the absence of the LbL platform. LbL structures with higher roughness and pore size facilitated the diffusion of catechol, resulting in lower LODs. The [(CHI)-(AuNP)-(CHI)-(CuPcS)]2-Tyr showed an LOD of 8.55∙10-4 μM, which was one order of magnitude lower than the 9.55·10-3 µM obtained with [(CHI)-(CuPcS)-(CHI)-(AuNP)]2-Tyr, and two orders of magnitude lower than the obtained with other nanostructured platforms. It can be concluded that the combination of adequate materials with complementary activity and the control of the structure of the platform is an excellent strategy to obtain biosensors with improved performances.

Metallic Phthalocyanines: impact of the film deposition method on its supramolecular arrangement and sensor performance

This short review gives a concise overview of the impact of deposition methods on the supramolecular arrangement of metallic phthalocyanine films and their applications. Primarily, an introduction about the possible phthalocyanine molecular structures and derivatives obtained from modification on the phthalocyanine rings was presented. The possibility of perfecting/improving the supramolecular arrangement of metallic phthalocyanine (MPcs) films by using different deposition techniques such as Langmuir-Blodgett (LB), Langmuir-Schaefer (LS), Layer-by-Layer (LbL), physical vapor deposition (PVD) and electrodeposition was discussed in further details. Herein, we highlighted some techniques used on the characterization of supramolecular arrangement (morphology, optical properties, and molecular organization), including the impact on sensing applications. The main scope of this short review is focused on the advances made in this research field in the last five years.

Electrochemical Sensors Modified with Combinations of Sulfur Containing Phthalocyanines and Capped Gold Nanoparticles: A Study of the Influence of the Nature of the Interaction between Sensing Materials

Voltametric sensors formed by the combination of a sulfur-substituted zinc phthalocyanine (ZnPc^RS) and gold nanoparticles capped with tetraoctylammonium bromide (AuNP^tOcBr) have been developed. The influence of the nature of the interaction between both components in the response towards catechol has been evaluated. Electrodes modified with a mixture of nanoparticles and phthalocyanine (AuNP^tOcBr/ZnPc^RS) show an increase in the intensity of the peak associated with the reduction of catechol. Electrodes modified with a covalent adduct-both component are linked through a thioether bond-(AuNP^tOcBr-S-ZnPc^R), show an increase in the intensity of the oxidation peak. Voltammograms registered at increasing scan rates show that charge transfer coefficients are different in both types of electrodes confirming that the kinetics of the electrochemical reaction is influenced by the nature of the interaction between both electrocatalytic materials. The limits of detection attained are 0.9 × 10⁻⁶ mol∙L⁻¹ for the electrode modified with the mixture AuNP^tOcBr/ZnPc^RS and 1.3 × 10⁻⁷ mol∙L⁻¹ for the electrode modified with the covalent adduct AuNP^tOcBr-S-ZnPc^R. These results indicate that the establishment of covalent bonds between nanoparticles and phthalocyanines can be a good strategy to obtain sensors with enhanced performance, improving the charge transfer rate and the detection limits of voltammetric sensors.

Investigation of pH and concentration influence on layer-by-layer self-assembly for nickel(II)phthalocyanine-tetrasulfonic acid tetrasodium salt coatings

Porphyrins and phthalocyanines are widely studied molecules for various functional applications. Researchers have investigated these photoactive compounds for electrochemical, sensor, semiconductor and photodynamic therapy purposes. Layer-by-layer (LbL) self-assembly is preferred for its simple, environmentally-friendly and water-based features compared to other coating techniques in the literature. Coating thickness can be controlled on the order of nanometers by LbL mechanism. Multilayer thin film formation of diverse phthalocyanine-based molecules is examined in terms of molecular orientation and temperature dependency by the LbL method. However, as well as concentration and temperature, the pH of the coating medium is another challenging parameter in the LbL approach. Film thickness and layer distribution are influenced by pH value, changing ionic density and hence the strength of electrostatic interactions during LbL assembly. In this study, layer-by-layer deposition of branched poly(ethyleneimine)/nickel(II)phthalocyanine-tetrasulfonic acid tetrasodium salt (NiPcTS) coating pair is studied. Impact of pH and concentration of NiPcTS on thin film properties are tested for four different pH conditions. Corresponding analysis is made by UV-vis spectroscopy, surface profiler and quartz-crystal microbalance. LbL deposition of NiPcTS is homogeneously controlled and 98 nm thick films are obtained in the presence of acidic media.