In the present study, we investigated the effect of an anode temperature on current transient process during porous anodic alumina growth and morphology of the anodic layers. Alumina films were formed in a 0.4 M oxalic acid at a constant voltage mode and electrolyte temperature. The temperature of the Al anode was controlled by thermoelectric Peltier element and varied in the range of 5 °C–60 °C. Surface morphology of both sides of anodic films and their cross-sections were analyzed by scanning electron microscopy (SEM) with subsequent statistical analysis of the SEM images by ImageJ software. It was found that when anode temperature was increased from 5 °С to 50 °С the pores diameter and interpore distance has not changed, but the porous structure became more ordered. According to these results, the rate of chemical dissolution of the barrier layer and pore walls did not depend on the anode temperature. At the anode temperature of 60 °С, pores diameter has increased 1.7 times and there was a distortion of the ordering of porous cells. It was concluded that the temperature difference between the aluminum substrate and electrolyte is an important parameter affecting the formation of ordered structure of nanoporous anodic alumina.

Herein, a novel electrochemical aptasensor using a broad-spectrum aptamer as a biorecognition element was constructed based on a screen-printed carbon electrode (SPCE) for simultaneous detection of aminoglycoside antibiotics (AAs). The ordered mesoporous carbon (OMC) was firstly modified on 2D Ti₃C₂ MXene. The addition of OMC not only effectively improved the stability of the aptasensor, but also prevented the stacking of Ti₃C₂ sheets, which formed a good current passage for signal amplification. The prepared OMC@Ti₃C₂ MXene functioned as a nanocarrier to accommodate considerable aptamers. In the presence of AAs, the transport of electron charge on SPCE surface was influenced by the bio-chemical reactions of the aptamer and AAs, generating a significant decline in the differential pulse voltammetry (DPV) signals. The proposed aptasensor presented a wide linear range and the detection limit was 3.51 nM. Moreover, the aptasensor, with satisfactory stability, reproducibility and specificity, was successfully employed to detect the multi-residuals of AAs in milk. This work provided a novel strategy for monitoring AAs in milk.

The effect of electrolyte temperature and anodizing voltage on the surface morphology of thin oxalic acid anodic alumina films formed on the SiO₂/Si and glass-ceramic substrate was studied. It was shown when anodizing voltage increased from 10 to 20 V pore diameter increased from 12.2 to 15.5 nm and from 14.5 to 17.7 nm for the films formed on SiO₂/Si and glass ceramic substrates, respectively. For the films formed at anodizing voltage (U_a) 30 and 40 V, pore diameter was 20.5 and 25.5 nm, respectively, and it was independent of the substrate type. It was demonstrated that when thin aluminum films were oxidized in oxalic acid, anodizing voltage of 30 V was a turning point at which the mechanism of the formation of anodic porous structure changed. By performing the experiments on the substrates with different thermal conductivity, we showed that at U_a < 30 V generated in the barrier layer Joule heating was absorbed by the substrate, but at U_a > 30 V the heat warmed up the electrolyte at the pore bottom that resulted in the changes of morphology of the films. We also suggested the empiric equation that connected pore diameter, anodizing current and generated Joule heating.