Nano-perovskite carbon paste composite electrode for the simultaneous determination of dopamine, ascorbic acid and uric acid

Effect of ball milling time on Sr0.7Sm0.3Fe0.4Co0.6O2.65 perovskites and their application as semiconductor layers in dye-sensitized solar cells

The practical utilization of TiO2 as a semiconductor in dye-sensitized solar cells (DSSCs) has been set back by poor visible light absorption, high charge carrier recombination, and low electrical conductivity, which reduce the power conversion efficiency (PCE) and sustainability of the device. In this respect, perovskites with excellent properties, such as large surface area, good optical properties, high electrical conductivity, and superior electrochemical stability, have recently emerged as promising alternatives capable of overcoming the drawbacks of TiO2. Herein, Sr0.7Sm0.3Fe0.4Co0.6O2.65 (SSFC) perovskites were prepared via the ball milling method at various milling times of 0, 5, and 10 h, and the obtained samples were denoted by SSFC-0, SSCF-5, and SSCF-10, respectively. Increasing the ball milling time led to a significant reduction in nanoparticle size and agglomeration, which, in turn, increased the surface area and electrical conductivity of the samples. As a consequence, the SSFC-10 perovskite exhibited the smallest average particle sizes (18.9 nm) with the largest surface area (61.8 m2 g-1) and minimum defects, which allowed for efficient electron transport, resulting in the best electrical conductivity of 49.8 S cm-1. Ultimately, DSSCs fabricated using SSFC-10 semiconductor layers achieved an optimum PCE of 6.01 %, which is an improvement of 8.67 %, 1.1 %, and 6.56 % for SSFC-0 (3.69 %), SSFC-5 (4.96 %), and TiO2 (5.64 %), respectively. Thus, varying the ball milling time can be used as an effective technique to tailor the physicochemical properties of SSFC to suit desired applications, particularly the fabrication of highly efficient and sustainable DSSC semiconductor layers.

Recent advances in perovskite oxides for non-enzymatic electrochemical sensors: A review

Non-enzymatic electrochemical sensors with significant advantages of high sensitivity, long-term stability, and excellent reproducibility, are one promising technology to solve many challenges, such as the detection of toxic substances and viruses. Among various materials, perovskite oxides have become a promising candidate for use in non-enzymatic electrochemical sensors because of their low cost, flexible structure, and high intrinsic catalytic activity. A comprehensive overview of the recent advances in perovskite oxides for non-enzymatic electrochemical sensors is provided, which includes the synthesis methods of nanostructured perovskites and the electrocatalytic mechanisms of perovskite catalysts. The better sensing performance of perovskite oxides is mainly due to the lattice O vacancies and superoxide oxygen ions (O₂^2-/O^-), which are generated by the transfer of lattice oxygen to adsorbed -OH and have performed excellent properties suitable for electrooxidation of analytes. However, the limited electron transfer kinetics, stability, and selectivity of perovskite oxides alone make perovskite oxides far from ready for scientific development. Therefore, composites of perovskite oxides with other materials like graphitic carbon, metals, metal compounds, conducting organics, and biomolecules are summarized. Furthermore, a brief section describing the future challenges and the corresponding recommendation is presented in this review.

Current Challenges and Developments in Perovskite-Based Electrochemical Biosensors for Effective Theragnostics of Neurological Disorders

Early-stage diagnosis of neurological disease and effective therapeutics play a significant role in improving the chances of saving lives through suitable and personalized courses of treatment. Biomolecules are potential indicators of any kind of disorder in a biological system, and they are recognized as a critical quantitative parameter in disease diagnosis and therapeutics, collectively known as theragnostics. The effective diagnosis of neurological disorders solely depends on the detection of the imbalance in the concentration of neurological biomarkers such as nucleic acids, proteins, and small metabolites in bodily fluids such as blood serum, plasma, urine, etc. This process of neurological biomarker detection can lead to an effective prognosis with a prediction of the treatment efficiency and recurrence. While review papers on electrochemical, spectral, and electronic biosensors for the detection of a wide variety of biomarkers related to neurological disorders are available in the literature, the prevailing challenges and developments in perovskite-based biosensors for effective theragnostics of neurological disorders have received scant attention. In this Mini-Review, we discuss the topical advancements in design strategies of perovskite-based electrochemical biosensors with detailed insight into the detection of neurological disease or disorder-specific biomarkers and their trace-level detection in biological fluids with high specificity and sensitivity. The tables in this Review give the performance analysis of recently developed perovskite-based electrochemical biosensors for effective theragnostics of neurological disorders. To conclude, the current challenges in biosensing technology for early diagnosis and therapeutics of neurological disorders are discussed along with a forecast of their anticipated developments.

Sensitive Electrochemical Detection of Bioactive Molecules (Hydrogen Peroxide, Glucose, Dopamine) with Perovskites-Based Sensors

Perovskite-modified electrodes have received increasing attention in the last decade, due to their electrocatalytic properties to undergo the sensitive and selective detection of bioactive molecules, such as hydrogen peroxide, glucose, and dopamine. In this review paper, different types of perovskites involved for their electrocatalytic properties are described, and the proposed mechanism of detection is presented. The analytical performances obtained for different electroactive molecules are listed and compared with those in terms of the type of perovskite used, its nanostructuration, and its association with other conductive nanomaterials. The analytical performance obtained with perovskites is shown to be better than those of Ni and Co oxide-based electrochemical sensors. Main trends and future challenges for enlarging and improving the use of perovskite-based electrochemical sensors are then discussed.

A selective sensing platform for the simultaneous detection of ascorbic acid, dopamine, and uric acid based on AuNPs/carboxylated COFs/Poly(fuchsin basic) film

In this study, an electrochemical sensing strategy was developed based on the synergies of gold nanoparticles (AuNPs) doped carboxylated covalent organic frameworks (ACOFs) and poly(fuchsin basic) film for the simultaneous detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA). This strategy not only took advantage of the adopted materials but also made use of the H-bonding and electrostatic interaction between the three compounds and materials. For this sensing, a poly-BFu film was formed on the surface of bare glass carbon electrode (GCE) under a constant potential. AuNPs was highly dispersed and immobilized on the constructed ACOF-TaTp to obtain AuNPs@ACOF. The constructed sensor AuNPs@ACOF/p-BFu/GCE combined the merits of high surface area, hydrophilicity, conductivity, and selective affinity, consequently exhibiting high sensitivity and selectivity toward the simultaneous detection of AA, DA, and UA with wide linear response ranges of 25-1500 μM, 0.75-40 μM, and 1-200 μM, respectively. The corresponding detection limits were 12.0 μM, 0.15 μM, and 0.22 μM. The simultaneous determination of UA in real human urine sample further confirmed the practicability of the designed electrode.

Graphene and Perovskite-Based Nanocomposite for Both Electrochemical and Gas Sensor Applications: An Overview

Perovskite and graphene-based nanocomposites have attracted much attention and been proven as promising candidates for both gas (H₂S and NH₃) and electrochemical (H₂O₂, CH₃OH and glucose) sensor applications. In this review, the development of portable sensor devices on the sensitivity, selectivity, cost effectiveness, and electrode stability of chemical and electrochemical applications is summarized. The authors are mainly focused on the common analytes in gas sensors such as hydrogen sulfide, ammonia, and electrochemical sensors including non-enzymatic glucose, hydrazine, dopamine, and hydrogen peroxide. Finally, the article also addressed the stability of composite performance and outlined recent strategies for future sensor perspectives.

Developing Low-Cost, High Performance, Robust and Sustainable Perovskite Electrocatalytic Materials in the Electrochemical Sensors and Energy Sectors: “An Overview”

Since its discovery in 1839, research on the synthesis and application of perovskite materials has multiplied largely due to their suitability to be used in the fields of nanotechnology, chemistry and material science. Appropriate changes in composition or addition of other elements or blending with polymers may result in new hybrid and/or composite perovskite materials that will be applied in advanced fields. In this review, we have recapitulated the recent progress on perovskite nanomaterial in solar cell, battery, fuel cell and supercapacitor applications, and the prominence properties of perovskite materials, such as excellent electronic, physical, chemical and optical properties. We discussed in detail the synthesis and results of various perovskite hybrid nanomaterials published elsewhere. We have also discussed the results of various studies on these low dimensional composite nanomaterials in broad sectors such as electronics/optoelectronics, batteries, supercapacitors, solar cells and electrochemical sensors.

Study of the Oxygen Evolution Reaction at Strontium Palladium Perovskite Electrocatalyst in Acidic Medium

The catalytic activity of Sr2PdO3, prepared through the sol-gel citrate-combustion method for the oxygen evolution reaction (OER) in a 0.1 M HClO4 solution, was investigated. The electrocatalytic activity of Sr2PdO3 toward OER was assessed via the anodic potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The glassy carbon modified Sr2PdO3 (GC/Sr2PdO3) electrode exhibited a higher electrocatalytic activity, by about 50 times, in comparison to the unmodified electrode. The order of the reaction was close to unity, which indicates that the adsorption of the hydroxyl groups is a fast step. The calculated activation energy was 21.6 kJ.mol-1, which can be considered a low value in evaluation with those of the reported OER electrocatalysts. The Sr2PdO3 perovskite portrayed a high catalyst stability without any probability of catalyst poisoning. These results encourage the use of Sr2PdO3 as a candidate electrocatalyst for water splitting reactions.

Platelet-structured strontium titanate perovskite decorated on graphene oxide as a nanocatalyst for electrochemical determination of neurotransmitter dopamine

In this work, we synthesized strontium titanate (SrTiO₃) by a simple co-precipitation technique and decorated it with graphene oxide (SrTiO₃/GO) for the effective determination of neurotransmitter agent dopamine (DA).

Novel Design of a Layered Electrochemical Dopamine Sensor in Real Samples Based on Gold Nanoparticles/β-Cyclodextrin/Nafion-Modified Gold Electrode

Change in the level of dopamine (DA) concentration in the human body causes critical diseases such as schizophrenia and Parkinson's disease. Therefore, the determination of DA concentration and monitoring its level in human body fluids is of great importance. An electrochemical sensor based on modification of the gold electrode surface with Nafion (NF), β-cyclodextrin (CD), and gold nanoparticles (AuNPs) was fabricated for the determination of DA in biological fluids. Combined impact of all the modifiers enhances the catalytic activity of the sensor. Gold nanoparticles increase the surface area of the sensor and enhance the electron transfer rate. CD plays a main role in enhancing the accumulation of protonated DA and forming stable complexes via electrostatic interactions and hydrogen bond formation. In addition, extra preconcentration of positively charged DA is achieved through ionic selectivity of NF. High electrocatalytic activity was achieved using the modified sensor for determination of DA in real urine samples in a wide concentration range, 0.05-280 μM with a low detection limit of 0.6 nM in the small linear dynamic range, 0.05-20 μM. Furthermore, common overlapped oxidation peaks of DA in presence of biologically interfering compounds at the gold electrode were resolved by using the modified sensor. Excellent recovery results were obtained using the proposed method for determination of DA in real urine samples.

Synthesis, structural and morphological characterizations of nano-Ru-based perovskites/RGO composites

Highly-dispersed Ru-based perovskites supported on reduced graphene oxide (A-RG) nanocomposites are prepared using different A-metal salts (Sr(NO₃)₂, Ba(NO₃)₂ and Ca(NO₃)₂). The procedure is based on a redox reaction between the metal precursors and graphene oxide (GO) using two different routes of reaction initiation: through thermal heating or by microwave-assisted heating. The resulting nanocomposites do not require further calcination, making this method less energy-demanding. In addition, no additional chemical reagents are required for either the GO reduction or the metal precursor oxidation, leading to an overall simple and direct synthesis method. The structure and morphology of the as-prepared A-RG (non-calcined) nanocomposites are characterized using various structural analyses including XRD, XPS, SEM/EDX and HR-TEM. Changing metal A in the perovskite as well as the “activation method” resulted in significant structural and morphological changes of the formed composites. SrRuO₃ and BaRuO₃ in combination with RuO₂ are obtained using a conventional combustion method, while SrRuO₃ (~1 nm size) in combination with Ru nanoparticles are successfully prepared using microwave irradiation. For the first time, a microwave-assisted synthesis method (without calcination) was used to form crystalline nano-CaRuO₃.

Energy and cost-efficient nano-Ru-based perovskites/RGO composites for application in high performance supercapacitors

Nano-Ru-based perovskites RGO are prepared simultaneously in presence of various A-metal salts (A = Sr, Ba or Ca salts) using two different methods for reaction initiation. No further calcination step is needed for the formation of well-defined perovskite structure. Graphene oxide (GO) is used as a fuel to prepare various Ru-based perovskites for the first time. The resulted low-Ru content nanocomposites are used as supercapacitor electrodes in a neutral electrolyte (1.0 M NaNO₃). The results show that the specific capacitance of the resulted nanocomposites strongly depends on the method of their preparation as well as the type of A-site of the nanocomposites. Ru-based perovskites RGO nanocomposites that are prepared by combustion method show higher specific capacitance than those prepared by microwave irradiation. The maximum specific capacitance of Sr-, Ba- and Ca-RG-C composites at scan rate 2 mV s^-1 are 564 (598 mF cm^-2), 460 (487 mF cm^-2) and 316 (336 mF cm^-2) F g^-1, respectively. This value is higher than our previous work using a physical mixture between the individually prepared RGO and SrRuO₃. Lowest values for specific capacitance are obtained when using CaRuO₃/RGO prepared using microwave-assisted method (Ca-RG-M). The resulted A-RG-nanocomposites show very high cycling stability and good specific capacitance compared to other Ru-based structures previously reported in the literature. A correlation is defined between the structure and specific capacitance of the nanocomposites. It is confirmed that the nanocomposite size, morphology and distribution over the RGO matrix influence the supercapacitor characteristics.

The effect of A-site doping in a strontium palladium perovskite and its applications for non-enzymatic glucose sensing

The catalytic activity of a strontium palladium perovskite, Sr₂PdO₃, toward non-enzymatic glucose sensing is strongly affected by the Sr²⁺ A-site partial substitution by Ca²⁺ ions; Sr_2−xCa_xPdO₃ with x = 0–0.7.