Ultralong room temperature phosphorescence (URTP) emitted from pure amorphous organic molecules is very rare. Although a few crystalline organic molecules could realize URTP with long lifetimes (>100 ms), practical applications of these crystalline organic phosphors are still challenging because the formation and maintenance of high-quality crystals are very difficult and complicated. Herein, we present a rational design for minimizing the vibrational dissipation of pure amorphous organic molecules to achieve URTP. By using this strategy, a series of URTP films with long lifetimes and high phosphorescent quantum yields (up to 0.75 s and 11.23%, respectively) were obtained from amorphous organic phosphors without visible fluorescence and phosphorescence under ambient conditions. On the basis of the unique features of URTP films, a new green screen printing technology without using any ink was developed toward confidential information encryption and decryption. This work presents a breakthrough strategy in applying amorphous organic materials for URTP.

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Ultralong room temperature phosphorescence from amorphous organic materials toward confidential information encryption and decryption.

Although conversion of low value but high-volume lignin by-product to its usable form is one of the determinant factors for building an economically feasible integrated lignocellulose biorefinery, it has been challenged by its structural complexity and inhomogeneity. We and others have shown that uniform lignin nanoparticles can be produced from a wide range of technical lignins, despite the varied lignocellulosic biomass and the pretreatment methods/conditions applied. This value-added nanostructure lignin enriched with multifunctional groups can be a promising versatile material platform for various downstream utilizations especially in the emerging nanocomposite fields. Inspired by the story of successful production and application of nanocellulose biopolymer, two types of uniform lignin nanoparticles (LNPs) were prepared through self-assembling of deep eutectic solvent (DES) and ethanol-organosolv extracted technical lignins derived from a two-stage fractionation pretreatment approach, respectively. Both LPNs exhibited sphere morphology with unique core–shell nanostructure, where the DES–LNPs showed a more uniform particle size distribution. When incorporated into the traditional polymeric matrix such as poly(vinyl alcohol), these LPN products displayed great potential to formulate a transparent nanocomposite film with additional UV-shielding efficacy (reached ~80% at 400 nm with 4 wt% of LNPs) and antioxidant functionalities (reached ~160 μm mol Trolox g−1 with 4 wt% of LNPs). At the same time, the abundant phenolic hydroxyl groups on the shell of LNPs also provided good interfacial adhesion with PVA matrix through the formation of hydrogen bonding network, which further improved the mechanical and thermal performances of the fabricated LNPs/PVA nanocomposite films. Both LNPs are excellent candidates for producing multifunctional polymer nanocomposites using facile technical route. The prepared transparent and flexible LNPs/PVA composite films with high UV-shielding efficacy, antioxidant activity, and biocompatibility are promising in the advanced packaging field, which potentially provides an additional high-value lignin product stream to the lignocellulose biorefinery. This study could open the door for the production and application of novel LNPs in the nascent bioeconomy.

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Lignin valorization: lignin nanoparticles as high-value bio-additive for multifunctional nanocomposites

Solid polymer electrolyte films of polyvinyl alcohol (PVA) doped with a different weight percent of potassium permanganate (KMnO 4 ) were prepared by standard solution cast method. XRD and FTIR techniques were performed for structural study. Complex formation between the PVA polymer and KMnO 4 salt was confirmed by Fourier transform infrared (FTIR) spectroscopy. The description of crystalline nature of the solid polymer electrolyte films has been confirmed by XRD analysis. The UV-Visible absorption spectra were analyzed in terms of absorption formula for non-crystalline materials. The fundamental optical parameters such as optical band gap energy, refractive index, optical conductivity, and dielectric constants have been investigated and showed a clear dependence on the KMnO 4 concentration. The observed value of optical band gap energy for pure PVA is about 6.27 eV and decreases to a value 3.12 eV for the film sample formed with 4 wt% KMnO 4 salt. The calculated values of refractive index and the dielectric constants of the polymer electrolyte films increase with increasing KMnO 4 content.

Structural and optical characterization of PVA:KMnO 4 based solid polymer electrolyte

Sepia eumelanin (SE), a biomacromolecule, was developed to prepare the excellent UV-shielding polymer material with better photostability. UV–vis transmittance spectra showed that poly(vinyl alcohol) PVA/SE film blocked most ultraviolet light below 300 nm even with a low concentration of SE (0.5 wt %), which still kept its high transparency in the visible spectrum. Rhodamine B photodegradation measurement further confirmed the excellent UV-shielding properties of PVA/SE film. FTIR indicated that the carbonyl absorption bands resulting from phtodegradation for PVA/SE film did not change after UV exposure for 2700 h. The tensile properties of neat PVA were deceased intensely after UV irradiation; however, those of PVA/SE film were reduced a little. Moreover, AFM indicated that the surface roughness of PVA/SE film was much lower than that of a neat PVA one. It could be concluded that SE reduced the PVA degradation rate dramatically, revealing enhanced photostability of PVA/SE film. The mechanism for outstand...

Simultaneous Enhancements of UV-Shielding Properties and Photostability of Poly(vinyl alcohol) via Incorporation of Sepia Eumelanin

We report preparation of Titanium dioxide (TiO2) nanoparticles doped PVA/PVP polymer nanocomposites by solvent casting technique. FTIR spectra and XRD studies signify the structural modifications taking place in the nanocomposites. The optical energy gap decreases by the addition of TiO2 nanoparticles. The mechanical properties such as tensile strength and Young’s modulus are enhanced by the addition of Titanium dioxide (TiO2) nanoparticles. The Fluorescence studies indicate that photoluminescence intensity is maximum for 4 wt% doping concentration of TiO2. The AFM analysis provides information about the surface roughness of the polymer film. The dielectric plot shows that the dielectric constant increases up to 12 wt% doping of TiO2, a further increase in the doping concentration results in the reduction of dielectric constant. The dielectric constant decreases with an increase in the frequency for all the films. The above properties show TiO2 doped PVA/PVP nanocomposite films are a prominent material for potential applications.

Structural, optical, mechanical and dielectric properties of titanium dioxide doped PVA/PVP nanocomposite

Optical and microstructural studies on electron irradiated PMMA: A positron annihilation study

Polymer blends along with 1-(4-methylphenyl)-3-(4-N,N,
dimethyl amino phenyl)-2-propen-1-one (MPDMAPP)
NLO-chromophore-doped composite films were prepared
by solvent casting method using DMF. The optical
properties were studied using UV–visible, refractive
index, steady state fluorescence, and fluorescence microscopic imaging techniques. The UV–vis absorption
spectra showed three absorption bands and were assigned to localized n?p*, n?p* inter band, and p?p* transition of charge transfer groups. The observed changes in the absorption peak, edges, and intensity with dopant concentration are understood based on charge transfer complex (CTC) formation. The refractive indices of the composite films varied from 1.4937–1.5398 for red and 1.5165–1.5516 for green light respectively. The steady state fluorescence data showed both emission peak wavelengths and intensity changes with MPDMAPP doping level in blend. The fluorescence anisotropy (r) variations in the composite films indicate the suppressed molecular motion of
MPDMAPP in the solid composite film. The fluorescence microscopic image of these composite films showed that the films are photochromatic in nature. These modified properties are thought to be due to the charge transfer upon excitation from the donor to the acceptor connected through benzene ring and CTC formation. POLYM. ENG. SCI., 49:903–909, 2009. a2009 Society of Plastics Engineers

Studies on fluorescent PVA + PVP + MPDMAPP composite films

The optical, electrical, and microstructurtal properties
of pure and TiO2/Poly(vinyl alcohol) (PVA) composite
polymer films were carried out using FTIR, XRD, UVVisible,
DC electrical conductivity, and Positron annihilation
lifetime spectroscopy (PALS) techniques. The FTIR study reveals that the Ti1 ions of TiO2 interacts
with the OH groups of PVA via intra/inter molecular
hydrogen bonding and forms charge transfer complex
(CTC). These formed CTC will affect the optical property
of the composite film, which is reflected from UVVisible
study. Using the observed UV–Visible spectra,
optical energy band gap is estimated and its value
decreases with increasing dopant concentration. The
positron annihilation studies show that the considerable
effect on free volume related microstructure of
the PVA due to doping and complex formation. These
microstructural modifications are also enhances PVA
crystallinity which is reflected from XRD studies. It is
also observed that the TiO2 particle forms cluster
within the PVA due to the aggregation of particles and
these particle cluster size increases with dopant concentration.
These microstructural variations due to doping affects the DC electrical conductivity and its variations are understood based on the intra chain one-dimensional interpolaron hopping conduction mechanism.

Ismayil

Papers

Optical and microstructural studies on electron irradiated PMMA: A positron annihilation study

Studies on fluorescent PVA + PVP + MPDMAPP composite films

Dopant‐induced microstructural, optical, and electrical properties of TiO2/PVA composite

Free volume related fluorescent behavior in electron beam irradiated chalcone doped PVA

Third order nonlinear optical studies of 1-(4-chloro phenyl)-3-(4- dimethylamino phenyl) prop-2-en-1-one