Neat Films Research Articles

A Non‐Halogenated Polymer Donor Based on Imide Unit for Organic Solar Cells with Efficiency Nearly 16%

Comprehensive SummaryNon‐halogenated polymers have great potential in the commercialization of organic solar cells (OSCs) due to their advantages in the manufacturing process. However, high‐performance donor polymers are limited to a small amount of building blocks. Herein, we utilize as building block 4H‐dithieno[3,2‐e:2',3'‐g]isoindole‐4,6(5H)‐dione (DTID) to design and synthesize a relevant non‐halogenated polymer PBTID for active layers in OSCs. PBTID exhibits a strong absorption in the wavelength range of 400—600 nm with a distinctly wide optical bandgap of 2.06 eV, a low‐lying highest occupied molecular orbital (HOMO) energy level of −5.53 eV. In addition, this polymer has a very strong aggregation effect in solution and could form nanoscale fibrils in the neat film. Consequently, when blended with the non‐fullerene acceptor Y6, the devices achieve a prominent PCE of 15.8% with a high Voc of 0.87 V. The Voc and PCE values are one of the highest values in the non‐halogenated polymer donor‐based OSCs reported to date.

Efficient solution-processed OLEDs featuring deep-blue triplet-triplet annihilation emitter based on pyrene derivative

Achieving high efficiency deep-blue organic light-emitting diodes (OLEDs) with a CIEy < 0.08 is still terribly urgent yet challenge. Herein, we designed and synthesized a novel blue triplet-triplet annihilation (TTA) emitter with a fan-shape torsional molecular structure, namely TbuPyB, which is based on benzene as core and three tert-butylpyrene as arm. The photophysical, electrochemical and electroluminescent performances of TbuPyB were systematically investigated. Intense deep-blue/blue emissions peaked at 413 and 472 nm are observed in the 7 wt% doped 1,3-bis(N-carbazolyl)benzene (mCP) thin film and neat film, accompanied by absolute photoluminescence (PL) quantum yield (PLQY) of 66.3% and 74.8%, respectively. Contributed by the TTA process, the solution-processed non-doped device exhibits blue emission peak at 470 nm with an impressive EQE of 10.65% and a CIE coordinates of (0.15, 0.20) at the voltage of 7.8 V. In contrary, at the 7 wt% dopant concentration, an outstandingly 57 nm violet-shifted deep-blue emission at 413 nm with an EQE of 6.87% and a CIE coordinates of (0.15, 0.06) was achieved in the doped device. These results schedule a novel avenue for designing highly efficient deep-blue emitter in the solution processable OLEDs.

Deep‐Red/Near‐Infrared Delayed Fluorescence Luminophores Based on Dipyrido[3,2‐a:2”,3”‐c]Phenazine‐11,12‐Dicarbonitrile for High‐Performance OLEDs

AbstractDeep‐red (DR) and near‐infrared (NIR) organic light‐emitting diodes (OLEDs) based on purely organic materials hold great potential in various frontier applications, but purely organic DR/NIR materials are far from satisfactory. Herein, a series of tailor‐made delayed fluorescence luminophores comprised of electron‐withdrawing dipyrido[3,2‐a:2″,3″‐c]phenazine‐11,12‐dicarbonitrile and various electron‐donating triarylamines are developed, and their thermal and electrochemical stabilities, electronic structures, photophysical properties and electroluminescence (EL) performances are investigated. They exhibit strong NIR emissions (758−767 nm) in neat films and DR/NIR emissions (680−691 nm) with good photoluminescence quantum yields (48−60%) in doped films, and prefer ordered horizontal alignment with high horizontal dipole ratios of 82−90%, which are attributed to the hybrid transition components of excited states, extended molecular plane and intramolecular hydrogen‐bonding. Their non‐doped OLEDs emit purely NIR light peaking at 820−834 nm with maximum external quantum efficiencies (ηext,maxs) of 0.66−1.06%, and thier doped OLEDs radiate DR/NIR emissions peaking at 656−748 nm with superb ηext,maxs of 14.4–31.0%. They present even better EL performances in sensitized OLEDs, with DR emissions peaking at 648−656 nm and higher ηext,maxs of 29.7−32.9%. These state‐of‐the‐art EL performances demonstrate the great potential of the developed DR/NIR delayed fluorescence luminophores in practical application.

Cellulose nanofiber-based pH indicator integrated with resazurin-modified carbon dots for real-time monitoring of food freshness

Modified carbon dots with resazurin (R-CD) were prepared using a hydrothermal method to fabricate a CNF-based pH-responsive indicator for real-time food freshness monitoring. FE-SEM and FTIR results confirmed that the R-CD was uniformly distributed in the CNF matrix. The thermal stability of the CNF/R-CD indicator film was increased, and the water contact angle of the film was slightly lower than that of the neat CNF film. The CNF/R-CD film showed excellent UV-barrier properties, with ∼98.3% and 87.7% blocking the UV-B and UV-A light. The indicator film showed excellent color stability even after 2 months of storage at 25 °C and responded rapidly to alkaline pH and NH3 through a color change from yellow to brownish-red. The CNF/R-CD indicator films exhibited distinct color changes during shrimp packaging depending on pH and TVB-N concentration. Therefore, the CNF/R-CD indicator can be used as a promising pH-sensitive color-changing intelligent packaging application for freshness monitoring.

The influence of the capping ligands on the optoelectronic performance, morphology, and ion liberation of CsPbBr3 perovskite quantum dots

Perovskite quantum dots (PeQDs) endowed with capping ligands exhibit impressive optoelectronic properties and enable for cost-efficient solution processing and exciting application opportunities. We synthesize and characterize three different PeQDs with the same cubic CsPbBr3 core, but which are distinguished by the ligand composition and density. PeQD-1 features a binary didodecyldimethylammonium bromide (DDAB) and octanoic acid capping ligand system, with a high surface density of 1.53 nm−2, whereas PeQD-2 and PeQD-3 are coated by solely DDAB at a gradually lower surface density. We show that PeQD-1 endowed with highest ligand density features the highest dispersibility in toluene of 150 g/L, the highest photoluminescence quantum yield of 95% in dilute solution and 59% in a neat film, and the largest core-to-core spacing in neat thin films. We further establish that ions are released from the core of PeQD-1 when it is exposed to an electric field, although it comprises a dense coating of one capping ligand per four surface core atoms. We finally exploit these combined findings to the development of a light-emitting electrochemical cell (LEC), where the active layer is composed solely of solution-processed pure PeQDs, without additional electrolytes. In this device, the ion release is utilized as an advantage for the electrochemical doping process and efficient emissive operation of the LEC.

Biodegradability of Starch Nanocomposite Films Containing Different Concentrations of Chitosan Nanoparticles in Compost and Planting Soils

Starch-based nanocomposite films containing chitosan nanoparticles (S/CNP films) are biodegradable and promising alternatives for non-biodegradable synthetic plastics. Nonetheless, limited work has been conducted to investigate the biodegradability of the films in soil. Thus, this work is aimed at investigating the biodegradation of starch-based films containing different concentrations of CNP (0, 10, 15, 20, 25% w/w solid starch) via a soil burial test using compost and planting soils. The biodegradability was investigated in terms of weight loss, visual appearance, morphology, and structural changes. It was found that S/CNP films biodegraded slower than neat starch films, and the degradation rate was reduced by 46 and 44% in compost and planting soils, respectively, with the increase in the concentrations of CNP from 10 to 25% w/w incorporated into the films. The degradation rate of films in compost soil after 8 days was found to be higher (0.0617 g/day) than in planting soil (0.0266 g/day). Visual appearance, morphology, and structural change results also supported these findings. The biodegradable S/CNP films can be used to reduce the usage of synthetic plastic.

Triazolotriazine-based mixed host for pure-red phosphorescent organic light-emitting diodes exhibiting ultra-low efficiency roll-off

The development of high-performance pure-red phosphorescent organic light-emitting diodes (Ph-OLEDs) especially with low efficiency roll-off at high brightness is still an appealing yet challenging task. Despite success of well-documented 1,3,5-triazine (TRZ)-based thermally activated delayed fluorescence (TADF) hosts in green Ph-OLEDs, the limited electron-withdrawing ability of the TRZ acceptor makes the TADF hosts unsuitable enough for usage in the assembly of high-performance red Ph-OLEDs. Herein, pure-red Ph-OLEDs with ultra-low efficiency roll-off at luminance above 10000 cd m−2 are achieved by developing two triazolotriazine-based TADF hosts (23aIC-TAZTRZ and 32aIC-TAZTRZ) with balanced bipolar transporting property, good morphological stability and high photoluminescence quantum yield in neat film. Particularly, the phosphor-doped 23aIC-TAZTRZ and 32aIC-TAZTRZ emitting layers display high horizontal orientation factors (Θ//) of 84% and 85%, respectively. Ph-OLEDs utilizing 50 wt% 23aIC-TAZTRZ and 50 wt% 32aIC-TAZTRZ as the mixed host exhibit pure-red emission with Commission Internationale de l’Eclairage (CIE) coordinate of [0.66, 0.34], high maximum external quantum efficiency (EQEmax) of 27.4% and ultra-low efficiency roll-off at 10000 cd m−2 (EQE10000 = 23.9%). This work not only discloses the potential of triazolotriazine acceptor for the construction of efficient TADF hosts, but also provides alternative candidates to TRZ-based hosts for the assembly of high-performance red Ph-OLEDs.

Tuning Photophysical Properties via Positional Isomerization of the Pyridine Ring in Donor–Acceptor-Structured Aggregation-Induced Emission Luminogens Based on Phenylmethylene Pyridineacetonitrile Derivatives

A series of aggregation-induced emission (AIE)-featured phenylmethylene pyridineacetonitrile derivatives named o-DBCNPy ((Z)-3-(4-(di-p-tolylamino)phenyl)-2-(pyridin-2-yl)acrylonitrile), m-DBCNPy ((Z)-3-(4-(di-p-tolylamino)phenyl)-2-(pyridin-3-yl)acrylonitrile), and p-DBCNPy ((Z)-3-(4-(di-p-tolylamino)phenyl)-2-(pyridin-4-yl)acrylonitrile) have been synthesized by tuning the substitution position of the pyridine ring. The linkage manner of the pyridine ring had influences on the molecular configuration and conjugation, thus leading to different photophysical properties. The absorption and fluorescence emission peak showed a bathochromic shift when the linking position of the pyridine ring changed from the meta to the ortho and para position. Meanwhile, o-DBCNPy exhibited the highest fluorescence quantum yield of 0.81 and the longest fluorescence lifetime of 7.96 ns as a neat film among all three isomers. Moreover, non-doped organic light-emitting diodes (OLEDs) were assembled in which the molecules acted as the light-emitting layer. Due to the relatively prominent emission properties, the electroluminescence (EL) performance of the o-DBCNPy-based OLED was superior to those of the devices based on the other two isomers with an external quantum efficiency (EQE) of 4.31%. The results indicate that delicate molecular modulation of AIE molecules could endow them with improved photophysical properties, making them potential candidates for organic photoelectronic devices.

Efficient Purely Organic Room-Temperature Phosphorescence from Selenium-Containing Conjugated Polymers for Signal-Amplified Oxygen Detection

Purely organic room-temperature phosphorescent (RTP) polymers with good processability and flexibility over small molecular crystals are highly attractive. Although many non-conjugated polymers (non-CPs) with efficient RTP emission have been reported, the development of metal-free RTP CPs remains a formidable challenge. Herein, CPs with clear RTP emission in both doped and neat films are readily prepared by introducing a selenium-containing phenoselenazine unit into conjugated backbones. The resulting RTP CPs can achieve phosphorescence lifetimes ranging from microseconds to milliseconds and phosphorescence quantum yields of up to 17.2% in film states, representing the highest value for metal-free CPs. Moreover, these RTP polymer films can be used for ratiometric oxygen detection due to their sensitive RTP emission to oxygen. Remarkably, for the first time, these metal-free CPs demonstrate significant phosphorescent signal amplification with a Stern–Volmer quenching constant (KSV) value of up to 5.54 × 10–3 ppm–1, which is 250 times higher than that of their molecule counterpart.

Fluorescent sensors for the detection of free-base illicit drugs – Effect of tuning the electronic properties

Fluorescence-based detection of chemical vapours is of interest for low power, portable devices that can be used in the field. Detection using fluorescence quenching via photoinduced electron transfer has been widely explored for the detection of chemicals that have high electron affinities. However, the method cannot be used for compounds that have low electron affinities such as illicit drugs. In this manuscript we describe a family of four compounds that are designed to have large ionisation potentials and are capable of detecting free-base illicit drugs via a photoinduced hole transfer process. The materials are composed of a 2-(9,9-di-n-propylfluoren-2-yl)benzothiadiazole (Fl-BT) base unit, with its properties tuned through addition of different donor (9,9-di-n-propylfluorene) (Fl-BT-Fl) and acceptor [aldehyde (Fl-BT-CHO) and dicyanovinyl (Fl-BT-DCV)] units. The compounds could be solution processed to form good quality, neat thin films with photoluminescence quantum yields of between 35 % and 87 %. The films of the compounds containing the aldehyde and dicyanovinyl electron withdrawing groups were able to detect the vapours of (+)-methamphetamine, (±)-3,4-methylenedioxyamphetamine, cocaine, and fentanyl, whereas the parent Fl-BT could not detect cocaine nor (±)-3,4-methylenedioxyamphetamine. In contrast, Fl-BT-Fl could only detect fentanyl. Combining the response of all four sensing materials provides a method for discriminating both fentanyl and (+)-methamphetamine. Finally, we found that while the ionisation potential was a key parameter for detecting free-base drugs, factors such as the physical interaction of the analytes with the sensing films were also important.

Polythiophenes with alkylthiophene side chains for efficient polymer solar cells

We synthesized two polythiophene derivatives with alkylthiophene side chains, named PT4T-0F and PT4T-2F. The introduction of alkylthiophene side chains endowed PT4T-0F with more ordered edge-on stacking in film, resulting in higher hole mobility of 0.45 cm2V−1s−1 in organic field-effect transistors in comparison to P3HT. Further introducing fluorine atoms, a mainly face-on orientation was achieved for PT4T-2F neat film, which was facilitated to charge transport and collection in polymer solar cells (PSCs). Using F8IC as acceptor, the PSC devices based on PT4T-2F achieved the champion efficiency of 10.48%, owing to the appropriate film morphology with moderate phase separation and favorable face-on molecular orientation. Such efficiency greatly outperformed those of PT4T-0F (2.85%) and P3HT (0.35%) based devices.

Enhanced strength and toughness of polylactic acid by blending with modified natural rubber having acetate pendant group

Among biobased and biodegradable polymers, polylactic acid (PLA) is most widely used one. However, its poor mechanical properties need to be enhanced. In this study, PLA blend film with improved mechanical properties were developed without compromising any bio-content. For this, natural rubber derivative with acetate pendant group (ANR) and PLA blend films were prepared. First, natural rubber was epoxidized, and then partial acetylation was achieved by the ring-opening reaction of the epoxy groups. The epoxidation and the acetylation were examined by FTIR analysis. 1H-NMR spectrum revealed a 29% epoxidation and 8.25% acetylation degree. The Tg of natural rubber (−66°C) increased to −41°C and −31°C after epoxidation and acetylation, respectively. The compatibility of ENR and ANR with PLA was evident from the DSC results and Molau test. The morphology of PLA blend film containing 25 wt% of ANR (ANR25) was observed as well-dispersed fine droplets by SEM images. The tensile strength, elastic modulus, and yield strength of ANR25 were measured as 11.6 MPa, 397.3 MPa, and 6.9 MPa, respectively. These values are considerably higher than neat PLA film. Compared to reported studies on PLA toughening so far, increments in both the strength and elongation of ANR25 were observed by tensile tests. Moreover, highest toughness among all samples was determined as 18.8 MJm−3 for ANR25, which is 1.8 times higher than neat PLA. Thus, a strong and tough bio-based PLA blend was developed for film application such as packaging and sheeting.

Mechanical Properties and Synergistic Interfacial Interactions of ZnO Nanorod-Reinforced Polyamide–Imide Composites

Metal oxide nanoparticle -reinforced polymers have received considerable attention due to their favorable mechanical properties compared to neat materials. However, the effect of nanoscale reinforcements of the interface on the composites' mechanical properties has not been investigated in-depth to reach their optimal performance in structural applications. Aiming at revealing the effect of synergistic interfacial interactions on the mechanical properties of polymer composites, using a nanoscale reinforcement, herein, a series of zinc oxide nanorod-reinforced polyamide-imide (PAI)/ZnO) composites were fabricated and their mechanical properties and viscoelastic responses were investigated. The composite prepared by reinforcing them with 5 wt % ZnO nanorods resulted in improved elastic modulus, stiffness, and hardness values by 32%, 14% and 35%, respectively, compared to neat polymer thin films. The viscoelastic dynamics of the composites revealed that there was an 11% increase in elastic wave speed in the composite, containing 5 wt % ZnO nanorods, indicating better response to high impacts. Delayed viscoelastic response decreased by 67% spatially and 51% temporally, with a corresponding decrease in the creep rate, for the 5 wt % ZnO nanorod- containing composite, evidencing its potential applicability in high strength lightweight structures. The improved mechanical properties with respect to the filler concentration evidence strong particle-polymer interfacial interactions, creating "chain-bound" clusters, providing clear reinforcement and polymer chain mobility retardation. However, hypervelocity impact testing revealed that all the composites' films were vulnerable to hypervelocity impact, but the spallation region of the composite films reinforced with 2.5 wt % and 5 wt % ZnO nanorods exhibited a cellular-like matrix with shock-induced voids compared to a rather hardened spallation region with cracks in the neat film.

Isomeric Small Molecule Donor with Terminal Branching Position Directly Attached to the Backbone Enables Efficient All‐Small‐Molecule Organic Solar Cells with Excellent Stability

AbstractAll‐small‐molecule organic solar cells (ASM‐OSCs) are challenging for their inadequate efficiency and device stability due to their more susceptive morphology. Herein, a family of isomeric small molecule donors (SMDs) is synthesized based on the benzodithiophene–terthiophene core with linear, 1st carbon, and 2nd carbon position branched butyl‐based rhodanine for ASM‐OSCs, respectively. The single crystal of thiophene‐substituted model T‐s‐Bu forms a more compact intermolecular packing with herringbone structure than slip‐layered packing‐based T‐n‐Bu and T‐i‐Bu. SM‐i‐Bu and SM‐s‐Bu show slightly blue‐shifted absorption and deepened HOMO levels in the neat film compared to SM‐n‐Bu. SM‐s‐Bu:BO‐4Cl blend films have distinct face‐on packing orientations and suitable fibrous phase separation along with more apparent microcrystals. Finally, SM‐s‐Bu:BO‐4Cl‐based device yields an improved power conversion efficiency of 16.06% compared to 15.12% and 8.22% for SM‐n‐Bu:BO‐4Cl and SM‐i‐Bu:BO‐4Cl, which is one of the top‐ranked results for BTR‐series SMDs in binary ASM‐OSCs. More importantly, the excellent storage stability with a T80 lifetime of over 1700 h and decent thermal stability is realized in SM‐s‐Bu:BO‐4Cl. This work highlights that the isomeric terminal alkyl with a branching point directly connected to the backbone for SMDs is a promising strategy for improving the crystal packing and film morphology and achieving highly efficient and stable ASM‐OSCs.

Tunable enzymatic biodegradation of poly(butylene succinate): biobased coatings and self-degradable films

Biodegradation of polyesters driven by enzymes is considered as one of the most effective way of degradation of these materials, as a way to control plastics accumulation in the environment. In this study, we present two different strategies to tune the enzymatic degradation of PBS films triggered by a lipase from Pseudomonas cepacia. Firstly, the kinetics of enzymatic degradation of PBS films was regulated by applying multilayer coats of polysaccharide alginate and chitosan (Alg/Chi) films. Secondly, self-degradable PBS films were prepared by embedding lipase-filled alginate particles. For comparison purposes, a detailed enzymatic degradation study of neat PBS films exposed to a lipase from P. cepacia in solution was made to determine the main experimental parameters influencing their degradation in solution. The results showed that an increase in enzyme concentration increased the degradation extent and rate of neat PBS films. At a fixed enzyme concentration, stirring of the solution containing the enzyme and the PBS also increased the biodegradation rate. In the case of the PBS films coated with a different number of Alg/Chi layers by spray-assisted LbL and subjected to enzymatic degradation experiments in solution, the extent of degradation was found to be dependent on the number of protective coating layers. Therefore, the Alg/Chi biobased coating constitutes an effective barrier to the diffusion of the lipase, thus proving its effectiveness in modulating the enzymatic activity as a function of coating thickness. In the case of self-degradable PBS containing lipase-embedded alginate beads (employed to protect the enzyme during high-temperature processing), only limited biodegradation was observed as the amount of encapsulated enzyme employed was too small. Nonetheless, these results are promising, as the enzymatic activity –indicative of the degradation capacity of the enzyme– determined for all these samples was about 2 orders of magnitude lower than that of previous assays.

Efficient Cyan Delayed Fluorescence Luminogen as Sensitizing Host for OLEDs with High Efficiencies and Extremely Low Roll-Offs.

Organic light-emitting diodes (OLEDs) using thermally activated delayed fluorescence (TADF) materials to sensitizing conventional fluorescence dopants (CFDs) have attracted intensive research interest due to the extraordinary device performances. Herein, a cyan luminogen (TCz-BP-SFAC) with TADF and aggregation-enhanced emission (AEE) character is developed as a sensitizing host for CFDs. TCz-BP-SFAC owns excellent thermal and electrochemical stabilities, prefers horizontal dipole orientation and demonstrates violent delayed fluorescence with high photoluminescence quantum yields in neat and doped films. It exhibits preeminent electroluminescence (EL) performances with maximum external quantum efficiencies (ηext s) of 25.1% and 30.0% and very low efficiency roll-offs. TCz-BP-SFAC also performs well as a sensitizing host for CFDs of different colors. When TCz-BP-SFAC sensitizing green emitter TTPA and orange emitter TBRB, the devices achieve high ηext s of 16.9% and 17.1% as well as very low efficiency roll-offs of 2.4% and 1.2%, respectively. Moreover, TCz-BP-SFAC can serve as a sensitizing host for two-color all-fluorescence white OLEDs, resulting in high ηext s of ∼18% and very low efficiency roll-offs of ∼5%. The outstanding EL performances predict the great potential of TCz-BP-SFAC as emitter and host in practical display and lighting devices.

Construction of fully biodegradable poly(L-lactic acid)/poly(D-lactic acid)-poly(lactide-co-caprolactone) block polymer films: Viscoelasticity, processability and flexibility

Development of biodegradable polymer films is essential for sustainable energy conservation and ecological protection. In this work, to improve the processability and toughness of poly(lactic acid) (PLA) films, poly(lactide-co-caprolactone) (PLCL) segments were introduced into poly(L-lactic acid) (PLLA)/poly(D-lactic acid) (PDLA) chains via chain branching reactions during reactive processing, and fully biodegradable/flexible PLLA/D-PLCL block polymer with long-chain branches and stereocomplex (SC) crystalline structure was prepared. Compared with neat PLLA, PLLA/D-PLCL exhibited much higher complex viscosity/storage modulus, lower tanδ values in terminal region and obvious strain-hardening behavior. Through biaxial drawing, PLLA/D-PLCL films were prepared, which showed improved uniformity and non-preferred orientation. With increasing draw ratio, the total crystallinity (Xc) and Xc for SC crystal both increased. By introduction of PDLA, the two phases of PLLA and PLCL penetrated and entangled with each other, and the phase structure transformed from “sea-island” structure to “co-continuous network” structure, which was beneficial for exerting the toughening effect of flexible PLCL molecules on PLA matrix. The tensile strength and elongation at break of PLLA/D-PLCL films increased from 51.87 MPa and 28.22 % of neat PLLA film to 70.82 MPa and 148.28 %. This work provided a new strategy for developing fully biodegradable polymer films with high performance.

Potato Chips Byproducts as Feedstocks for Developing Active Starch-Based Films with Potential for Cheese Packaging.

The potato chip industry generates brownish frying residues, which are usually landfilled. While spent frying oil has value as biodiesel, the defatted brownish water-soluble extract (BrE) does not yet have an application. In this work, it was hypothesized that BrE can be a source of compounds for active packaging. BrE is composed of carbohydrates (66.9%), protein (5.7%), and a small amount of phenolics and esterified fatty acids. When incorporated into starch-based formulations and casted, BrE at 5%, 10%, and 15% w/w (dry starch weight) conferred a yellowish coloration while maintaining the transparency of neat films. The BrE increased the films' traction resistance, elasticity, and antioxidant activity while decreasing their hydrophilicity. Furthermore, starch/15% BrE-based films showed diminished water vapor and good UV-light barrier properties. Their contact with sliced cheese did not change the products' hardness during storage (14 days). Weight loss of the cheese was observed after 7 days of storage, stabilizing at 6.52%, contrary to the cheese packed in polyamide (PA)/polyethylene (PE), already used in food packaging. The cheese packed in the starch/15% BrE-based films showed a significant yellowish darkening and lower content of volatile oxidation products compared to the PA/PE. Therefore, BrE revealed to have compounds with the potential to tune the performance of starch-based films for food packaging.

Benzoxazole-Based Hybridized Local and Charge-Transfer Deep-Blue Emitters for Solution-Processable Organic Light-Emitting Diodes and the In fluences of Hexahydrophthalimido.

Hybridized local and charge-transfer (HLCT) emitters have attracted extensive attention, but the insolubility and severe self-aggregation tendency restrict their applications in solution-processable organic light-emitting diodes (OLEDs), particularly deep-blue OLEDs. Herein, two novel benzoxazole-based solution-processable HLCT emitters (BPCP and BPCPCHY) are designed and synthesized, in which benzoxazole acts as an acceptor, carbazole acts as a donor, and hexahydrophthalimido (HP, with a large intramolecular torsion angle and spatial distortion characteristics) acts as a bulky modified end-group with weak electron-withdrawing effects. Both BPCP and BPCPCHY exhibit HLCT characteristics and emit near ultraviolet in toluene at 404 and 399 nm. Compared to the BPCP, the BPCPCHY solid shows much better thermal stability (Tg, 187 vs 110 °C), higher oscillator strengths of the S1-to-S0 transition (0.5346 vs 0.4809), and faster kr (1.1 × 108 vs 7.5 × 107 s-1) and thus a much higher ΦPL in the neat film. The introduction of HP groups greatly suppresses the intra-/intermolecular charge-transfer effect and self-aggregation trends, and the BPCPCHY neat films placed in air for 3 months can still maintain an excellent amorphous morphology. The solution-processable deep-blue OLEDs utilizing BPCP and BPCPCHY achieved a CIEy of 0.06 with maximum external quantum efficiency (EQEmax) values of 7.19 and 8.53%, respectively, which are among the best results of the solution-processable deep-blue OLEDs based on the "hot exciton" mechanism. All of the above results indicate that benzoxazole is an excellent acceptor for constructing deep-blue HLCT materials, and the strategy of introducing HP as a modified end-group into an HLCT emitter provides a new perspective to develop solution-processable efficient deep-blue OLEDs with high morphological stability.

Synthesis of lignin from waste leaves and its potential application for bread packaging: A waste valorization approach

In this study, lignin was synthesized from the waste leaves of Ficus auriculata obtained after the extraction of gallic acid. The synthesized lignin was incorporated into PVA films, and the neat and blended films were characterized using different techniques. Lignin addition improved the UV-shielding, thermal, antioxidant, and mechanical properties of PVA films. The water solubility decreased from 31.86 % to 7.14 ± 1.94 %, while the water vapor permeability increased from 3.85 ± 0.21 × 10−7 g.m.h−1 Pa−1 to 7.84 ± 0.64 × 10−7 g.m.h−1 Pa−1 for pure PVA film and the film containing 5 % lignin, respectively. The prepared films showed a much better performance than commercial packaging films in inhibiting mold growth during the storage of preservative-free bread. The bread samples packed with commercial packaging showed signs of mold growth on the 3rd day, while the growth was inhibited entirely till the 15th day for PVA film containing 1 % lignin. The pure PVA film and the ones containing 3 % and 5 % of lignin inhibited growth till the 12th and 9th day, respectively. Findings from the current study show that safe, cheap, and eco–friendly biomaterials can hinder the growth of spoilage microorganisms and potentially be used in food packaging.