In this paper we report on the magnetic properties of pure bulk ferromagnetic graphite, obtained by a chemical route previously described. This magnetic graphite has been obtained by a vapor reaction consisting of a controlled etching on the graphite structure. By magnetic force microscopy we have verified that its magnetic properties are related to the topographic defects introduced in the pristine material. Also, the magnetic properties have been verified through magnetization measurements as a function of temperature and applied magnetic field. At low temperatures ͑2 K͒ the saturation magnetization reaches a value of 0.58 emu/ g, leading to a defect concentration of 1250 ppm. The system is highly irreversible due to the inhomogeneity of the distribution of defects in the material. Two transition temperatures are detected, T c1 = 115͑5͒ K and T c2 = 315͑5͒ K. These transitions could be associated to the weak coupling between ferromagnetic regions related to defects and to the ferromagnetism inside the defect regions.

In this work we report on structural and Raman spectroscopy measurements of pure and Sn-doped In 2 O 3 nanowires. Both samples were found to be cubic and high quality single crystals. Raman analysis was performed to obtain the phonon modes of the nanowires and to confirm the compositional and structural information given by structural characterization. Cubic-like phonon modes were detected in both samples and their distinct phase was evidenced by the presence of tin doping. As a consequence, disorder effects were detected evidenced by the break of the Raman selection rules.

We report on (magneto-) transport measurements of individual In2O3 nanowires. We observed that the presence of a weak disorder arising from doping and electron-boundary collisions leads to weak localization of electrons as revealed by the positive magnetoconductivity in a large range of temperatures ( approximately 77 K). From temperature-dependent resistance and magnetoconductivity data, the electron-electron interaction was pointed out as the mechanism responsible for the increase of resistance in the low temperature range and the dominant source of the dephasing at low temperatures. The experimental data provided the phase coherence time tau(phi) approximately T(-2/3) expected for 1D systems, giving consistent support to the mechanisms underlying the weak-localization and electron-electron scattering theories.

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Using low-resistance indium contacts, we measured some transport properties of undoped vapor-liquid-solid grown tin oxide monocrystals with a belt shape. From the transport measurements, the two following conduction mechanisms were investigated: thermal activation and variable range hopping. An energy gap of 3.8 eV was found. The energy gap was confirmed by thermally activated measurements in the range between 10 and 300 K. For high temperatures (T>300 K), the influence of the disorder caused by the superficial ions layer is measurable. The electron transport in this case was found to be governed by the well known variable range hopping mechanism and the spatial extension of carrier’s wavelength was calculated to be 4 nm.

Even after over 2 years of the COVID-19 pandemic, research on rapid, inexpensive, and accurate tests remains essential for controlling and avoiding the global spread of SARS-CoV-2 across the planet during a potential reappearance in future global waves or regional outbreaks. Assessment of serological responses for COVID-19 can be beneficial for population-level surveillance purposes, supporting the development of novel vaccines and evaluating the efficacy of different immunization programs. This can be especially relevant for broadly used inactivated whole virus vaccines, such as CoronaVac, which produced lower titers of neutralizing antibodies. and showed lower efficacy for specific groups such as the elderly and immunocompromised. We developed an impedimetric biosensor based on the immobilization of SARS-CoV-2 recombinant trimeric spike protein (S protein) on zinc oxide nanorod (ZnONR)-modified fluorine-doped tin oxide substrates for COVID-19 serology testing. Due to electrostatic interactions, the negatively charged S protein was immobilized via physical adsorption. The electrochemical response of the immunosensor was measured at each modification step and characterized by scanning electron microscopy and electrochemical techniques. We successfully evaluated the applicability of the modified ZnONR electrodes using serum samples from COVID-19 convalescent individuals, CoronaVac-vaccinated with or without positive results for SARS-CoV-2 infection, and pre-pandemic samples from healthy volunteers as controls. ELISA for IgG anti-SARS-CoV-2 spike protein was performed for comparison, and ELISA for IgG anti-RBDs of seasonal coronavirus (HCoVs) was used to test the specificity of immunosensor detection. No cross-reactivity with HCoVs was detected using the ZnONR immunosensor, and more interestingly, the sensor presented higher sensitivity when compared to negative ELISA results. The results demonstrate that the ZnONRs/spike-modified electrode displayed sensitive results for convalescents and vaccinated samples and shows excellent potential as a tool for the population’s assessment and monitoring of seroconversion and seroprevalence.

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The magnetic and superconducting properties of RuSr 2 Gd 1.5 Ce 0.5 Cu 2 O 10−␦ polycrystalline samples with different oxygen-doping levels are presented. A strong suppression of the superconducting temperature ͑T c ͒, as well as a reduction in the superconducting fraction, occurs as the oxygen content is reduced by annealing the samples in oxygen-deprived atmospheres. Drastic changes in the electrical resistivity are observed above T c , possibly associated with oxygen removal, mainly from grain boundaries. However, the magnetic ordering is relatively less affected by the changes in oxygen content of the samples. The spin-glass transition is enhanced and shifted to higher temperatures with the reduction in oxygen content. This could be correlated with an increase in the spin disorder and frustration for the oxygen-depleted samples. Also, the same oxygen-vacancyinduced disorder could explain the reduction in the fraction of the sample showing antiferromagnetic order. We also report significant changes in the measured properties of the samples as a function of time.