Dopamine (DA) is an important neurotransmitter in the kidney, cardiovascular system, and central nervous system, which abnormality is associated with many diseases. In this work, we synthesized a functionalized multi-walled carbon nanotube/silver nanoparticle (f-MWCNT/AgNP) nanocomposites as the biosensing material to detect DA. The SEM, EDS, and TEM characterizations indicated the success of the functionalization process with MWCNT as the base material. The values of the linear range, the limit of detection (LOD), and the selectivity of the nanocomposite were all obtained from the Differential Pulse Voltammetry (DPV) measurements. The obtained LOD value was 0.2778 µM in the linear range of 0–8 µM, which is lower than the required concentration value for detecting DA in human urine (0.3–3 µM). The biosensor’s high selectivity on DA with the presence of other human-related biofluids was also reported. These results show that f-MWCNT/AgNP nanocomposites are a promising biosensor material for the detection of DA. Graphical abstract

Label-free hepatitis B surface antigen electrochemical immunosensors by Cu-NH₂BDC MOFs.

Electrochemical method is often chosen to analyze various bio-chemical reactions due to its operation simplicity with versatile applications. Thus, for this purpose, the procurement of potentiostat, an electrochemical-based analysis instrument, also needs to focus on the low price, but maintaining its rich analysis features. In this paper, we designed a low-cost and portable potentiostat system based on the ESP32 microcontroller. Even with the low-cost system design, it supports various electrochemical measurement methods, i.e. cyclic voltammetry (CV), linear sweep voltammetry (LSV), square wave voltammetry (SWV), differential pulse voltammetry (DPV), normal pulse voltammetry (NPV), and the observation of electrochemical current against time based on chronoamperometry measurement method. The potentiostat performance was assessed by the electrochemical signal accuracy and errors. Furthermore, the measurements can also be carried out semi-parallelly within three measurement channels simultaneously. The results showed that it could produce voltammograms with an average accuracy of more than 90%, compared to the commercial Emstat Pico. Even though having this comprehensive and extensive electrochemical analysis, the cost of the total system realization could be downsized to only USD 21.4.

As saving the energy inside a house is an important issue to address, more home appliances are now implementing IoT technology. Here, we propose an IoT based smart home software application that are able to intelligently control the home appliances automatically based on our instruction set or behavior. The smart home uses the software to receive input from the user and forward the input to the server or host. In addition to receiving input from the user, the smart home software is also used to display all information about the house condition to the user. The smart home system uses AMQP as the communication protocol between software, server, and host. To ensure the security, all of the communication data is encrypted by the system using either RSA or AES algorithm.

The hardware prototyping of an IrDA-based remote infrared (IR) device has been presented. The designed IR remote capable of controlling the smart home devices that use IR to interact with them such as the generic air conditioner (AC), Televisions (TV), and projector, in which the mentioned electronics appliances haven't an encryption system embedded. Hence, we can read the installed source-code of these devices, then stored in our IR remote. We used STM32L100 as a microcontroller. According to the test results, our prototype able to perform well as expected. The TV and AC can be controlled ”on” as well as ”off” at a certain maximum distance depends on power level used.