Herein, we report a facile synthesis, characterization, and electrochemical sensing application of ZnO nanopeanuts synthesized by a simple aqueous solution process and characterized by various techniques in order to confirm the compositional, morphological, structural, crystalline phase, and optical properties of the synthesized material. The detailed characterizations revealed that the synthesized material possesses a peanut-shaped morphology, dense growth, and a wurtzite hexagonal phase along with good crystal and optical properties. Further, to ascertain the useful properties of the synthesized ZnO nanopeanut as an excellent electron mediator, electrochemical sensors were fabricated based on the form of a screen printed electrode (SPE). Electrochemical and current-voltage characteristics were studied for the determination of picric acid sensing characteristics. The electrochemical sensor fabricated based on the SPE technique exhibited a reproducible and reliable sensitivity of ~1.2 μA/mM (9.23 μA·mM⁻¹·cm⁻²), a lower limit of detection at 7.8 µM, a regression coefficient (R²) of 0.94, and good linearity over the 0.0078 mM to 10.0 mM concentration range. In addition, the sensor response was also tested using simple I-V techniques, wherein a sensitivity of 493.64 μA·mM⁻¹·cm⁻², an experimental Limit of detection (LOD) of 0.125 mM, and a linear dynamic range (LDR) of 1.0 mM–5.0 mM were observed for the fabricated picric acid sensor.

Recyclable nano CeO₂ POD mimic records a K_m reduction (∼30% and ∼19.72% for TMB and H₂O₂, respectively) in 900 seconds at pH 4.5. ATP boosts catalytic feasibility in nano CeO₂ at physiological pH.

A label free electrochemical sensor based on pure titanium oxide and manganese (Mn)-doped titanium oxide (TiO₂) nanoparticles are fabricated and characterized for the sensitive detection of myoglobin (Mb) levels to analyze the cardiovascular infarction. Pristine and Mn-doped TiO₂ nanoparticles were synthesized via the sol-gel method and characterized in order to understand their structure, morphologies, composition and optical properties. The structural properties revealed that the pure- and doped-TiO₂ nanoparticles possess different TiO₂ planes. FTIR studies confirm the formation of metal oxide nanoparticles by exhibiting a well-defined peak in the range of 600–650 cm⁻¹. The values of the optical band gap, estimated from UV-Vis spectroscopy, are decreased for the Mn-doped TiO₂ nanoparticles. UV-Vis spectra in the presence of myoglobin (Mb) indicated interaction between the TiO₂ nanoparticles and myoglobin. The SPE electrodes were then fabricated by printing powder film over the working electrode and tested for label-free electrochemical detection of myoglobin (Mb) in the concentration range of 0–15 nM Mb. The fabricated electrochemical sensor exhibited a high sensitivity of 100.40 μA-cm^−2/nM with a lowest detection limit of 0.013 nM (0.22 ng/mL) and a response time of ≤10 ms for sample S3. An interference study with cyt-c and Human Serum Albumin (HSA) of the sensors show the selective response towards Mb in 1:1 mixture.

Cu-doped ZnO nanoparticles were used in the form of a screen-printed electrode on a prefabricated gold-plated electrode for electrochemically determining the concentration of nanomolar myoglobin (Mb), a cardiac biomarker. Initially, Cu-doped ZnO nanoparticles were synthesised through the sol gel method by using three Cu-doping concentrations (varying number of Cu atoms). Then, the synthesised material was analysed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy, and field emission secondary electron microscopy. Analysis revealed a mixed phase of ZnO and CuO, whereas the vibration band in the range of 650-700 cm ^-1 indicated metal oxide formation. Morphological observation showed uniform-sized spherical particles of approximately 15-20 nm (as nanoparticles) that were evenly distributed, which were also confirmed based on the average particle size estimated using XRD data. The developed electrodes were tested for biomarker concentration from 3 to 15 nM based on cyclic voltammogram and impedance spectroscopic curves, where the redox potential/current/charge transfer resistance changed linearly with Mb and dopant (Cu) concentration. The sensitivity was estimated as 2.13-10.14~μAnM ^-1 cm ^-2 with dopant concentration of approximately 0.46 nM as the limit of detection.

Tin oxide is a well known nonstoichiometric material with dual valency. The invariance of stoichiometry is very intriguing. As of today no report is available for preparing perfect stoichiometric tin oxide. Here we report a novel method to prepare stoichiometric tin oxide by modifying the known plasma enhanced chemical vapor deposition technique using SnCl4-xH2O as precursor and O2 as reactant gas at various temperatures from 300 to 800 °C. Tetragonal rutile structure of SnO2 was found, grown along the [110] direction. X-ray photoelectron spectroscopic measurement showed constant Sn/O ratio. Sn 3d and O 1s were found composed of only Sn4+ (487.2 eV) and O–Sn4+ (531.2 eV) with equal peak widths. Raman band intensity (∼633 cm−1) was found increasing with temperature, indicating the morphological changes. Sheet resistance of ∼0.5 kΩ/◻ at 300 °C was measured that reduces to ∼0.1 kΩ/◻ at 600 °C. It is found that film stoichiometry remains unaltered, while the structural morphology changes significantly.

Mn-doped ZnO nanostructures were synthesized with three different estimated Mn concentration (atoms/cm ³ ) using sol-gel technique. As synthesized nanostructures were analyzed using X-ray diffraction spectroscopy (XRD), Fourier-transform-infrared spectroscopy (FTIR), and field-emission secondary electron microscopy (FE-SEM). XRD pattern reveals of doped ZnO nanostructures reveal a peak related to Zn ₂ Mn ₃ O ₈ phase along with peaks related to pure ZnO. Average particle size, estimated using Scherer formula, increases with Mn-doping. FE-SEM reveals morphological change from spherical particles (~15-20 nm) to nano-rods then nano-belt like 2 D super lattice structure after doping. Optical band gap obtain from Tauc's plot is 3.82, 2.05, 2.1 and 2.47 eV for pure-ZnO and Mn-doped samples with 13×10 ¹⁷ , 20×10 ¹⁷ and 32×10 ¹⁷ Mn atoms/cm ³ , respectively. Presence of vibration band from 665 to 680 cm ^-1 in FTIR spectra endorses metal oxide formation. Nanomaterials were screen printed over working electrode of pre-fabricated three terminal electrode. This was used for electrochemical detection of myoglobin (Mb); a biomarker for acute myocardial infarction and were tested for Mb concentrations from 0-15 nM using cyclic voltammetry and electrochemical impedance spectroscopy. Redox current and charge transfer resistance varied linearly with Mb concentration. 7-fold increased sensitivity towards Mb in Mn-doped ZnO sensors is attributed to doping induced stress in nanostructures. Maximum sensitivity of 95μA-cm ^-2 nM ^-1 with LOD of 0.35 nM is observed for ZnO with 13 × 10 ¹⁷ Mn atomic/cm ³ . Response time of ~10 ms is observed. Interference carried out with 7 nM Cytochrome c and 5 mM HSA reveal different oxidation potential and current value for Mb.