An overview of luminescent bio-based composites

High-resolution particle size and shape analysis of the first Samarium nanoparticles biosynthesized from aqueous solutions via cyanobacteria Anabaena cylindrica

Samarium (Sm) is one of the most sought-after rare earth metals. Price trends and dwindling resources are making recovery increasingly attractive. In this context, the use of cyanobacteria is highly promising. For Sm it was unclear whether Anabaena cylindrica produces particles through metabolically active Sm³⁺ uptake. High-resolution (HR) imaging now clearly demonstrates microbe generated biosynthesis of Sm nano-sized particles (Sm NPs) in vivo. Furthermore, a simple method to determine particle size and shape with high accuracy is presented. Digital image analysis with ImageJ of HR-TEMs is used to characterize Sm NPs revealing a nearly uniform local size distribution. Assuming round particles, the overall average area size is 135.5 nm², resp. 11.9 nm diameter. In HR, where different cell sections of the same cell are averaged, the mean particle is smaller, 76.7 nm² resp. 8.9 nm diameter. The reciprocal aspect ratio is 0.63. The Feret major axis ratio is calculated as shape factor, with 35% of the particles between 1.2 and 1.4. A roundness classification shows that 38% of particles are fairly round and 41% are very round. Consequently, A. cylindrica represents a suitable microorganism for possible Sm recovery and biosynthesis of roundish nano-sized particles.

Chiroptical property enhancement of chiral Eu(III) complex upon association with DNA-CTMA

DNA-based materials have attracted much attention due to their unique photo-functional properties and potential applications in various fields such as luminescent and biological systems, nanodevices, etc. In this study, the photophysical properties of a chiral Eu(III) complex, namely (Eu(D-facam)₃), within DNA films were extensively investigated. The enhancement of photoluminescence (more than 25-folds increase of luminescence quantum yield) and degree of circularly polarization in luminescence (g_lum = − 0.6) was observed upon interaction with DNA. Various photophysical analyses suggested that the emission enhancement was mainly due to an increase of the sensitization efficiency (high η_sens) from the ligands to Eu(III) and suppression of the vibrational deactivation upon immobilization onto the DNA molecule. From CD and VCD measurements, it was suggested that the coordination structure of Eu(D-facam)₃ was affected by the interaction with DNA, suggesting that the structural change of Eu(D-facam)₃ contributed to the improvement of its luminescent properties.

One-Step Multicomponent Polymerizations for the Synthesis of Multifunctional AIE Polymers

As a new class of functional luminescent materials, polymers with aggregation-induced emission (AIE) feature attract much attention because of their advantages of efficient solid-state fluorescence, excellent processability, structural diversity, and multifunctionalities. Among all polymerization methods toward AIE polymers, multicomponent polymerizations (MCPs) exhibit the merits of simple operation, good atom economy, high polymerization efficiency, broad functional-group tolerance, etc. In this feature article, the recent progress on the development of one-step MCPs for the synthesis of AIE polymers is highlighted. The representative functionalities of the resulting AIE polymers are illustrated. Perspectives on the challenges and future development directions of this field are also discussed.

Luminescence properties of the Ln-EDTA complexes covalently linked to the chitosan biopolymers containing β-diketonate as antenna ligands

This paper reports on the preparation, characterization, and photoluminescence properties of novel hybrid materials, in which the EDTA-Ln-L complexes (where L: H₂ O, acac, bzac, dbm, and tta ligands, and Ln: Eu, Gd, and Tb) were covalently linked to the precursor medium molecular weight chitosan surface (CS) matrices or on the chitosan surfaces previously crosslinked with epichlorohydrin (CSech). The emission spectra of these materials were characterized by intraconfigurational-4fN transitions centred on the Eu³⁺ and Tb³⁺ ions. Some broad bands from the polymeric matrix were also observed in the emission spectra, however the relative intensities of the intraconfigurational bands increased significantly for systems containing diketonate ligands when the antenna effect became more efficient. The values of the radiative rates (A_rad ) were higher for crosslinked hybrid systems with epichlorohydrin, while nonradiative rates (A_nrad ) presented the opposite behaviour. These data contributed to an increase in the values of emission quantum efficiency (η) for crosslinked materials. The effect of the modification process and antenna ligand on the values of intensities, intensity parameters Ω₂ e Ω₄ of the Eu³⁺ complexes were also investigated. The results showed that the crosslinked biopolymer surfaces have great potential for applications in molecular devices light converters.

Near infra-red polymeric nanoparticle based optical imaging in Cancer diagnosis

Cancer disease is a foremost health concern and top basis of death in comparison with many diseases including cardiovascular disorders. During initial diagnosis (usually late diagnosis), a majority of cancer patients suffer from metastatic and advanced cancer stages which resulted in limited therapeutic modalities based interventions and effectiveness. Though considerable advancement has been made in combating the disease, continuous and intense efforts are ongoing for early diagnosis and development of therapies. Generally applied treatment options for cancer are surgery, chemotherapy and radiotherapy, which are restricted by failure to early diagnose, insufficient on-targeted drug delivery, systemic toxicity, and lack of real-time monitoring of therapeutic responses in cancer. Noninvasive imaging or minimally invasive imaging methodology is valuable in clinical diagnostic settings. Specifically, noninvasive optical imaging integrated with polymeric nanomaterial have been extensively investigated in the field of cancer diagnostics and therapy. Currently, optical imaging methods go together with polymer-based fluorescent nanoparticles in accomplishing the molecular level detection of tumor boundaries. NIR probe tagged polymeric nanoparticles have potential to provide an advantage in the early cancer detection, therapeutic monitoring and image guided surgery procedures. This article review the recent progress in state-of-the-art NIRF polymeric nanoparticles used for optical imaging particularly on cancer diagnosis.

A Tunable Photoluminescent Composite of Cellulose Nanofibrils and CdS Quantum Dots

The preparation of fluorescent nanocomposite materials with tunable emission wavelengths by combining cellulose nanofibrils (CNFs) with inorganic nanoparticles is important for promoting CNFs applications. A CNF/CdS nanocomposite was prepared via in situ compositing at room temperature on oxidized CNFs with CdS quantum dots. By controlling the -COOH/Cd²⁺ ratio on the CNF, the feeding time of Na₂S and the ultrasonic maturing time, the size of the CdS quantum dots on the CNF surface could be adjusted so that to obtain the CNF/CdS nanocomposite material with different fluorescent colors. The results indicated that the CdS particles quantized were evenly distributed on the CNF. The maximum average size of the CdS nanoparticles glowed red under the excitation of UV light was 5.34 nm, which could be obtained with a -COOH/Cd²⁺ ratio of 1.0, a Na₂S feeding time of 20 min, and an ultrasonic maturing time of 60 min. A series of CNF/CdS nanocomposite materials were obtained with CdS nanoparticle sizes varying from 3.44 nm to 5.34 nm, the emission wavelength of which varied from 546 nm to 655 nm, and their fluorescence color changed from green to yellow to red. This is the first time the fluorescence-tunable effect of the CNF/CdS nanocomposite has been realized.

Multi-component assembly and luminescence tuning of lanthanide hybrids through the inside–outside double modification of zeolite A/L

A novel inside–outside double modification path is used to functionalize ZA/L to construct multi-component hybrids presenting multi-color luminescence.