Photoluminescence, Self cleaning and Photocatalytic Behavior of Waterborne Hyperbranched Polyester/Carbon dot@TiO₂ Nanocomposite

Abstract

Functional materials with innovative optical features have attracted cumulative attention owing to their indispensable and inimitable roles in the advanced human‐civilization. Thus, in the present work, an excellent excitation wavelength dependent down‐ and up‐conversion photo‐luminescent carbon dot@TiO2 containing waterborne hyperbranched polyester nanocomposite was reported for the first time. Further, the thermosets of the nanocomposite were transparent and emitted different colors on exposure of different wavelengths of UV light. Most interestingly, the nanocomposite showed anti‐reflecting as well as self‐cleaning properties. The self‐cleaning behavior was achieved through photocatalytic degradation of different organic contaminants namely pesticide, phenol, bis‐phenol A and mixed dyes under normal sunlight. Further, the thermosetting nanocomposite can be used as an efficient photocatalyst for reduction of common nitro‐aromatic compound under normal sunlight. The nanocomposites also exhibited strong antibacterial activity against Staphylococcus aureus, Bacillus subtilis, Klebsiella pneumoniae and Pseudomonas aeruginosa bacterial strains. Thus, the studied nanocomposite has remarkable prospect in different advanced applications.

Carbon Nanodots in Photodynamic Antimicrobial Therapy: A Review

“…Typical absorption and sample emission spectra are shown in Figure 2 b, demonstrating the strong UV absorption and visible absorption tail inherent to carbon dot structures; studies have been conducted to further extend the absorption of carbon dots into the visible or even NIR region [ 37 , 38 , 39 ]. Carbon dots are also known to be capable of up-conversion photoluminescence [ 27 , 40 ] which will be discussed further in the context of antimicrobial applications in Section 4.2 . Beyond synthetic optimization of excitation/emission properties, carbon dot samples also uniquely have an excitation-dependent emission profile, as shown in Figure 2 c. This allows, to a degree, luminescence tuning simply by adjusting the excitation source used in an experiment; however, varying carbon dot quantum efficiencies at each wavelength must be carefully considered.…”

“…In fact, the structural, chemical, and photophysical characteristics of carbon dots imbue a strong versatility in their potential through tuning and modification. Accordingly, carbon dots are mentioned to have been employed for photocatalytic dye degradation [ 22 , 27 , 40 , 51 ], photocatalytic/electrical water splitting [ 22 , 52 ], solar devices [ 22 , 40 , 53 ], detection and biosensing [ 3 , 16 , 27 , 51 ], drug delivery [ 3 , 27 , 51 ], bioimaging [ 3 , 17 , 27 , 51 ], gene transmission [ 3 , 17 ], and even in LED technologies [ 27 , 54 ]—although this list is far from exhaustive and is ever-expanding, including APDT applications.…”

“…Simultaneously, incorporation of carbon dots also broadened the absorbing region of the material [ 12 ]. In a report by Hazarika et al, carbon dots were used for both down- and up-conversion photoluminescence characteristics in a carbon dot and titanium dioxide (CD@TiO 2 ) polyester nanocomposite material [ 27 ]. It is also worth noting that in some cases, carbon dots are simply incorporated for their multi-color emission capabilities, namely as an imaging agent within a hybrid system.…”

“…Although this study could benefit from deeper analysis into bracket surface morphology changes, long term efficacy, and biofilm formation, it sets a promising foundation for the use of carbon dots in hybrid materials for APDT and photocatalytic applications. Additional studies in this vein include the previously discussed CD-DNA-PpIX hydrogel [ 59 ], the Langmuir-Blodgett thin films of hydrophobic carbon quantum dots [ 36 ], and the CD@TiO 2 polyester materials [ 27 ].…”

“…By optimizing these characteristics, it is possible to improve the efficiency of light utilization by the photosensitizer, and even to select for activation wavelengths that are themselves not inherently harmful, unlike short-wavelength ultraviolet light (UV-C) [ 24 ]. In contrast, TiO 2 materials, which are commonly used for photocatalytic disinfection applications, suffer from low utilization of solar energy [ 22 , 25 ] and require UV activation [ 26 , 27 ]. Beyond quantum efficiency, it is also desirable to tune the proximity or adherence of the photosensitizer to bacterial cells [ 21 ].…”