The applied potential, time, and water content are crucial factors in the electrochemical anodization process because the growth of one-dimensional nanotubes can be accelerated by enhancing the corrosive effect. We investigated the effect of the water content on the resistive switching (RS) properties of Ti foils by anodizing the foils and varying the water content in an electrolyte (1–10 vol %). By increasing the water content, we facilitated a slow transition from nanopores to nanotubes and realized an increase in the tube wall diameter and tube length. All of the fabricated memristive devices exhibited a reliable and reproducible bipolar resistive switching effect. The optimized device exhibited bipolar RS properties with good dc endurance (104 cycles) and data retention capability (105 s). Our results suggest that as the water content increases to 5 vol %, the RS process improves; further increases in the water content impair the RS process.

In this work, we have developed a versatile three-in-one single beam visible colorimeter for undergraduate laboratory courses. The battery and mains electricity supply (utility power), wired and wireless data logging, and 3D-printed components are three important highlights of the developed visible colorimeter. The system is based on a low-cost ARDUINO UNO microcontroller and can measure the absorbance of the liquid samples in the visible region of the electromagnetic spectrum. For on-field measurements, the present colorimeter can work on a small 9 V battery. Therefore, the present portable colorimeter can be used for different field studies. In addition to this, the system can also work on a mains electricity supply for benchtop measurements. The measurement results can be displayed on an OLED display or can be recorded using an open-source data acquisition tool on personal computers/laptops. In addition to this, measured data can be transmitted using a Bluetooth module to Android phones. For this, an open-source Android application was developed using the MIT App Inventor web application. For rapid prototyping of the system, all components of the visible colorimeter are designed and developed using 3Dprinting technology. The functioning of the colorimeter was tested by measuring the absorbance of aqueous KMnO 4 and K 2 Cr 2 O 7 samples, and experimental results were compared with the commercially available single beam visible colorimeter. The measurement difference between the present colorimeter and commercial spectrophotometer was less than 4%, suggesting the satisfactory performance of the colorimeter. Therefore, students can use the present system to understand some basic concepts of the colorimeter.