Layer-by-Layer AuNPs-SiPy + /Prussian blue nanoparticles modified electrodes: characterization and electrocatalytic effects

Oxygen Vacancy Injection on (111) CeO2 Nanocrystal Facets for Efficient H2O2 Detection

Facet and defect engineering have achieved great success in improving the catalytic performance of CeO₂, but the inconsistent reports on the synergistic effect of facet and oxygen vacancy and the lack of investigation on the heavily doped oxygen vacancy keeps it an attractive subject. Inspired by this, CeO₂ nanocrystals with selectively exposed crystalline facets (octahedron, cube, sphere, rod) and abundant oxygen vacancies have been synthesized to investigate the synergistic effect of facet and heavily doped oxygen vacancy. The contrasting electrochemical behavior displayed by diverse reduced CeO₂ nanocrystals verifies that oxygen vacancy acts distinctly on different facets. The thermodynamically most stable CeO₂ octahedron enclosed by heavily doped (111) facets surprisingly exhibited the optimum non-enzymatic H₂O₂ sensing performance, with a high sensitivity (128.83 µA mM^-1 cm^-2), a broad linear range (20 µM~13.61 mM), and a low detection limit (1.63 µM). Meanwhile, the sensor presented satisfying selectivity, repeatability, stability, as well as its feasibility in medical disinfectants. Furthermore, the synergistic effect of facet and oxygen vacancy was clarified by the inclined distribution states of oxygen vacancy and the electronic transmission property. This work enlightens prospective research on the synergistic effect of alternative crystal surface engineering strategies.

Nanoconjugates based on a novel organic-inorganic hybrid silsesquioxane and gold nanoparticles as hemocompatible nanomaterials for promising biosensing applications

A new hybrid organic-inorganic silsesquioxane material, 3-n-propyl(2-amino-4-methyl)pyridium chloride (SiAMPy⁺Cl^-), was synthesized and successfully applied for the synthesis of stable nanoconjugates with gold nanoparticles (AuNPs-SiAMPy⁺). SiAMPy⁺Cl^- was obtained through a simple sol-gel procedure by using chloropropyltrimetoxysilane and tetraethylorthosilicate as precursors and 2-amino-4-methylpyridine as the functionalizing agent. The resulting material was characterized by employing FTIR, XRD, and ¹H-, ¹³C-, and ²⁹Si-NMR spectroscopy. The synthesis of AuNPs-SiAMPy⁺ nanoconjugates was optimized through a 2³ full factorial design. UV-VIS, FTIR, TEM, DLS, and ζ-potential measurements were used to characterize the nanoconjugates, which presented a spherical morphology with an average diameter of 5.8 nm. To investigate the existence of toxic effects of AuNPs-SiAMPy⁺ on blood cells, which is essential for their future biomedical applications, toxicity assays on human erythrocytes and leukocytes were performed. Interestingly, no cytotoxic effects were observed for both types of cells. The nanoconjugates were further applied in the construction of electrochemical immunosensing devices, aiming the detection of anti-Trypanosoma cruzi antibodies in serum as biomarkers of Chagas disease. The AuNPs-SiAMPy⁺ significantly enhanced the sensitivity of the biodevice, which was able to discriminate between anti-T. cruzi positive and negative serum samples. Thus, the AuNPs-SiAMPy⁺-based biosensor showed great potential to be used as a new tool to perform fast and accurate diagnosis of Chagas disease. The promising findings described herein strongly confirm the remarkable potential of SiAMPy⁺Cl^- to obtain nanomaterials, which can present notable biomedical properties and applications.

Electrochemical Deposition of Polyelectrolytes Is Maximum at the Potential of Zero Charge

Electrochemical deposition of cationic and anionic polyelectrolyte on a Au electrode is studied as a function of applied potential between the electrode and the solution of monovalent electrolyte. The deposition is measured by open circuit potential relative to a pristine electrode in a reference solution (100 mM NaCl). The rate of deposition is measured by a home-built electrochemical-optical method in real time. It was discovered that the polarity of the potential and magnitude of the potential are not the primary reasons to enhance deposition. For example, both the amount and rate of deposition of negatively charged poly(styrenesulfonate) in NaCl are higher when the electrode is at -200 mV than at +200 mV with respect to the solution. The results are explained in terms of the charge state of the electrical double layer that is primarily controlled by supporting (small) ions.