Upsurgence of smartphone as an economical, portable, and consumer-friendly analytical device/interface platform for digital sensing of hazardous environmental ions

Ions play a pivotal role in the biological regulatory processes and catalyzing enzymatic reactions; however, increased levels in the human body leads to many health risks or toxicity. To circumvent this, periodic and precise monitoring of significant ions in environmental, biological, chemical, and food samples are necessary, which need to be mapped/monitored continuously. This has prompted researchers to develop cost-effective, handy, and rapid techniques which can be fruitful for even untrained personnel by obviating manual user instructions, lengthy sample preparation steps, and costly instruments. The exploitation of user-friendly behavior, affordable price, and ubiquitous usage of smartphones has led to the development of a plethora of smartphone-based methodologies whereby they can serve as devices, detectors, or interfaces. Their in-built high-resolution rear camera, ambient light sensors, wireless connectivity, internal storage, and global positioning systems minimize the cost and simplify the fabrication of developing point-of-care testing devices, making them operable in challenging conditions with limited resources. Coupling smartphones with iCloud technology allows the synchronous storing and online transmitting of databases to consumers even in remote areas, which helps in real-time monitoring and continuously scrutinizing contaminants in the environment. This is not an exhaustive review but enumerates the progress made in the development of smartphone-based analytical aids by incorporating advanced device fabrication strategies and hassle-free analytical protocols during the past years (2014–2021). An account of key features like sensing performance of the developed methods in terms of selectivity, sensitivity, and detection limits and their limitations for recognition of environmental and biologically eminent ions is also discussed. Lastly, this review paves the way for the development of advanced innovative analytical techniques employing smartphone technology for the foreseeable future to ensure point-of-care human safety.