Enhancing photoluminescence of carbon quantum dots doped PVA films with randomly dispersed silica microspheres

Abstract

As a kind of excellent photoluminescent material, carbon quantum dots have been extensively studied in many fields, including biomedical applications and optoelectronic devices. They have been dispersed in polymer matrices to form luminescent films which can be used in LEDs, displays, sensors, etc. Owing to the total internal reflection at the flat polymer/air interfaces, a significant portion of the emitted light are trapped and dissipated. In this paper, we fabricate free standing flexible PVA films with photoluminescent carbon quantum dots embedded in them. We disperse silica microspheres at the film surfaces to couple out the total internal reflection. The effects of sphere densities and diameters on the enhancement of photoluminescence are experimentally investigated with a homemade microscope. The enhancement of fluorescence intensity is as high as 1.83 when the film is fully covered by spheres of 0.86 $${\boldsymbol{\mu }}$$µm diameter. It is worth noting that the light extraction originates from rather the scattering of individual spheres than the diffraction of ordered arrays. The mechanism of scattering is confirmed by numerical simulations. The simulated results show that the evanescent wave at the flat PVA/air interface can be effectively scattered out of the film.

Multicolor Emitting Carbon Dot-Reinforced PVA Composites as Edible Food Packaging Films and Coatings with Antimicrobial and UV-Blocking Properties

“…Recently, carbon materials have been given great importance as nanofillers in the preparation of functional polymer nanocomposites to improve the properties of PVA films. , Sapalidis et al have produced PVA nanocomposite films containing dendritic polymer (QPEI)-functionalized multi-walled carbon nanotubes (oxCNTs) using various oxCNT QPEI contents ranging from 0.05 to 1.0% w/w and reported that these films exhibited enough optical transparency, advanced mechanical properties, and exceptionally high antibacterial behavior . Kovalchuk and co-workers have produced luminescent PVA composite films containing coal-derived graphene quantum dots (GQDs) by a simple and environmentally friendly solution method.…”

Transfer of a Well-Aligned TiO2 Nanorod Array onto GaN-Based LEDs for Light Extraction Enhancement

“…For the transfer of TiO 2 NRs, PVA was used as a binder as explained at Figure 1d, which can affect the light extraction efficiency of LEDs. 21 Therefore, we compare the three samples: Bare LED(LED-I), an LED with PVA(LED-II), The LEE was obtained from the ratio of the amount of light output power in the air to the generated power in the dipole source. Figure 7 shows the far-field radiation patterns of LED-I, LED-II, and LED-III, which showed similar radiation symmetry, and the calculated LEEs of the LED-I, LED-II, and LED-III were 100%, 135%, and 220%, respectively.…”

“…To investigate the optical effects of the transferred TiO 2 NR array on LED chips, we measured the light extraction efficiency (LEE). For the transfer of TiO 2 NRs, PVA was used as a binder as explained at Figure d, which can affect the light extraction efficiency of LEDs . Therefore, we compare the three samples: Bare LED­(LED-I), an LED with PVA­(LED-II), and a PVA-coated LED with the TiO 2 NRs array (LED-III).…”

Effects of Heteroatom Doping of Carbon Dots from Sugar on Optical Properties, Phenolic Content, Antioxidant Activity, Photostability, and Cytotoxicity

“…The photoluminescence of CDs is important because it is widely used in several applications, ranging from sensing, drug tracking, bioimaging, optoelectronic devices [25,48–52] . Several studies have indicated that heteroatom doping can improve the QY values of CDs [8,11,13,53] .…”

“…The photoluminescence of CDs is important because it is widely used in several applications, ranging from sensing, drug tracking, bioimaging, optoelectronic devices. [25,[48][49][50][51][52] Several studies have indicated that heteroatom doping can improve the QY values of CDs. [8,11,13,53] To confirm that, in this work, the fluorescence QYs of all CDs were measured using quinine sulfate as a reference (Figure 8).…”