We have developed a simple approach for the large-scale synthesis of water-soluble green carbon nanodots (G-dots) from many kinds of large food waste-derived sources. About 120 g of G-dots per 100 kg of food waste can be synthesized using our simple and environmentally friendly synthesis approach. The G-dots exhibit a high degree of solubility in water because of the abundant oxygen-containing functional groups around their surface. The narrow band of photoluminescence emission (400-470 nm) confirms that the size of the G-dots (∼4 nm) is small because of a similar quantum effects and emission traps on the surfaces. The G-dots have excellent photostability; their photoluminescence intensity decreases slowly (∼8%) under continuous excitation with a Xe lamp for 10 days. We carried out cell viability assay to assess the effect of cytotoxicity by introducing G-dots in cells such as Chinese hamster ovary cells (CHO-K1), mouse muscle cells (C2C12), and African green monkey kidney cells (COS-7), up to a concentration of 2 mg mL(-1) for 24 h. Due to their high photostability and low cytotoxicity, these G-dots are excellent probes for in vitro bioimaging. Moreover, the byproducts (not including G-dots) of G-dot synthesis from large food-waste derived sources promoted the growth and development of seedlings germinated on 3DW-supplemented gauze. Because of the combined advantages of green synthesis, high aqueous stability, high photostability, and low cytotoxicity, the G-dots show considerable promise in various areas, including biomedical imaging, solution state optoelectronics, and plant seed germination and/or growth.

The flexible sensing platform is a key component for the development of smart portable devices targeting healthcare, environmental monitoring, point-of-care diagnostics, and personal electronics. Herein, we demonstrate a simple, scalable, and cost-effective strategy for fabrication of a sensing electrode based on a waste newspaper with conformal coating of parylene C (P-paper). Thin polymeric layers over cellulose fibers allow the P-paper to possess improved mechanical and chemical stability, which results in high-performance flexible sensing platforms for the detection of pathogenic E. coli O157:H7 based on DNA hybridization. Moreover, P-paper electrodes have the potential to serve as disposable, flexible sensing platforms for point-of-care testing biosensors.

Highly ordered and flexible nanopillar arrays have received considerable interest for many applications of electrochemical devices because of their unique mechanical and structural properties. Here, we report on highly ordered polyoxometalate (POM)-doped polypyrrole (Ppy) nanopillar arrays produced by soft lithography and subsequent electrodeposition. As-prepared POM-Ppy/nanopillar films show superior electrochemical performances for pseudocapacitor and enzymeless electrochemical sensor applications and good mechanical properties, which allowed them to be easily bent and twisted. Regarding electrochemical characteristics for pseudocapacitive electrodes, the POM-Ppy/nanopillar electrodes are capable of delivering high areal capacitance of 77.0 mF cm(-2), high rate performance, and good cycle life of ∼100% retention over 3500 cycles even when bent. Moreover, the study suggests that the POM-Ppy/nanopillar electrodes have an excellent electrocatalytic activity toward hydrogen.

Flexible and highly ordered nanopillar arrayed electrodes have brought great interest for many electrochemical applications, especially to the biosensors, because of its unique mechanical and topological properties. Herein, we report an advanced method to fabricate highly ordered nanopillar electrodes produced by soft-/photo-lithography and metal evaporation. The highly ordered nanopillar array exhibited the superior electrochemical and mechanical properties in regard with the wide space to response with electrolytes, enabling the sensitive analysis. As-prepared gold and silver electrodes on nanopillar arrays exhibit great and stable electrochemical performance to detect the amplified gene from foodborne pathogen of Escherichia coli O157:H7. Additionally, lightweight, flexible, and USB-connectable nanopillar-based electrochemical sensor platform improves the connectivity, portability, and sensitivity. Moreover, we successfully confirm the performance of genetic analysis using real food, specially designed intercalator, and amplified gene from foodborne pathogens with high reproducibility (6% standard deviation) and sensitivity (10 × 1.01 CFU) within 25 s based on the square wave voltammetry principle. This study confirmed excellent mechanical and chemical characteristics of nanopillar electrodes have a great and considerable electrochemical activity to apply as genetic biosensor platform in the fields of point-of-care testing (POCT).

Design and fabrication of electrodes is key in the development of electrochemical sensors with superior electrochemical performances. Herein, an enzymeless electrochemical sensor is developed for detection of hydrogen peroxide based on the use of highly ordered polyoxometalate (POM)-doped polyaniline (PANI) nanopillar films. The electrodeposition technique enables the entrapment of POMs into PANI during electropolymerization to produce thin coatings of POM-PANI. Electrochemical investigations of the POM-PANI/nanopillar electrode showed well-defined multiple pairs of redox peaks and rapid electron transfer. The nanopillar structure facilitated the diffusion of the electrolyte and thus, enhanced the redox reaction. In particular, the POM-PANI/nanopillar electrode was incorporated into a flow injection biosensor and it demonstrates its electrocatalytic activity to detect hydrogen peroxide with high sensitivity, rapid response time, and low detection limit.