Carbon dots (CDs) are optically active carbon-based nanomaterials. These nanomaterials can change their light emission properties in response to various external stimuli such as pH, temperature, pressure, and light. The CD’s remarkable stimuli-responsive smart material properties have recently stimulated massive research interest for their exploitation to develop various sensor platforms. Herein, an effort has been made to review the major advances made on CDs, focusing mainly on its smart material attributes and linked applications. Since the CD’s material properties are largely linked to their synthesis approaches, various synthesis methods, including surface passivation and functionalization of CDs and the mechanisms reported so far in their photophysical properties, are also delineated in this review. Finally, the challenges of using CDs and the scope for their further improvement as an optical signal transducer to expand their application horizon for developing analytical platforms have been discussed.

A novel smartphone-based, multi-channel, optic fiber platform for quantitative detection of Plasmodium falciparum glutamate dehydrogenase (PfGDH) has been explored in this study. A four-channel smartphone slip-on accessory was fabricated to couple one end of the optic fibers to the smartphone flashlight and the other end to the smartphone camera. The optic fiber probes for this setup were prepared with gold-sputtered U-bent plastic optic fibers and functionalized with an aptamer specific for PfGDH. The images of the light spots from the fiber were captured from this setup at specific time intervals after incubation with simulated malaria samples. The blue histogram values (B-value) of the light spots in the captured images were obtained using ImageJ software. The sensor statistically exhibited a limit of detection (LOD) of 264 pM and utilized only 175 μL of the sample. The specificity of this system was evaluated by exposing it to interferents like human glutamate dehydrogenase (HGDH), Plasmodium lactate dehydrogenase (PfLDH), and Plasmodium falciparum Histidine Rich Protein-II (PfHRP-II) and the response to these interferents was found to be very minimal when compared to the response to the aptamer–PfGDH interaction. A shelf-life study was also performed, with probes maintained at room temperature (25–30 °C) with relative humidity in the range of 70–90%. The efficiency of the probes on the 20th day was found to be 91.38% of the initial output.

The development of robust bioanalytical devices and biosensors for infectious pathogens is progressing well with the advent of new materials, concepts, and technology. The progress is also stepping towards developing high throughput screening technologies that can quickly identify, differentiate, and determine the concentration of harmful pathogens, facilitating the decision-making process for their elimination and therapeutic interventions in large-scale operations. Recently, much effort has been focused on upgrading these analytical devices to an intelligent technological platform by integrating them with modern communication systems, such as the internet of things (IoT) and machine learning (ML), to expand their application horizon. This review outlines the recent development and applications of bioanalytical devices and biosensors to detect pathogenic microbes in environmental samples. First, the nature of the recent outbreaks of pathogenic microbes such as foodborne, waterborne, and airborne pathogens and microbial toxins are discussed to understand the severity of the problems. Next, the discussion focuses on the detection systems chronologically, starting with the conventional methods, advanced techniques, and emerging technologies, such as biosensors and other portable devices and detection platforms for pathogens. Finally, the progress on multiplex assays, wearable devices, and integration of smartphone technologies to facilitate pathogen detection systems for wider applications are highlighted.