Preparation of antimicrobial/ultraviolet protective bacterial nanocellulose film with carbon dots synthesized from lactic acid bacteria

Fluorescent carbon nanoparticles or carbon quantum dots (CQDs) are a new class of carbon nanomaterials that have emerged recently and have garnered much interest as potential competitors to conventional semiconductor quantum dots. In addition to their comparable optical properties, CQDs have the desired advantages of low toxicity, environmental friendliness low cost and simple synthetic routes. Moreover, surface passivation and functionalization of CQDs allow for the control of their physicochemical properties. Since their discovery, CQDs have found many applications in the fields of chemical sensing, biosensing, bioimaging, nanomedicine, photocatalysis and electrocatalysis. This article reviews the progress in the research and development of CQDs with an emphasis on their synthesis, functionalization and technical applications along with some discussion on challenges and perspectives in this exciting and promising field.

We systematically summarize the recent progress in the green synthesis and formation mechanism of CDs with the hope to provide guidance for developing CDs with the concept of green chemistry. In addition, we discuss and organize the current opinions on the fluorescence origin of CDs and the latest progress of CDs in fluorescence sensing applications. Carbon dots (CDs) have received an increasing amount of attention because of their significant advantages in terms of low toxicity, chemical inertness, tunable fluorescence, good water solubility, and physicochemical properties. Due to these desirable properties, they have been used in numerous fields, including chemo- and biosensing, fluorescence imaging, and drug delivery. In this review, we aim to demonstrate the recent progress in the green synthesis and formation mechanism of CDs, and provide guidance for developing CDs with the concepts of green chemistry. In addition, we discuss three kinds of most accepted luminescence origins: surface state, quantum confinement effect and molecular fluorescence. Finally, we systematically summarize the latest progress of CDs in fluorescence sensing applications, including both solution phase sensing and solid phase sensing. Furthermore, the challenges and future direction of CDs in this emerging field are discussed.

Highly photoluminescent carbon dots with a PL quantum yield of 26% have been prepared in one step by hydrothermal treatment of orange juice. Due to high photostability and low toxicity these carbon dots are demonstrated as excellent probes in cellular imaging.