In this work, we compared the effect of Quartzite nanoparticles (QtzNP - crystalline SiO2) and amorphous silica nanoparticles (ASNP) as scatters in a random laser (RL), correlating the laser efficiency to the morphology and refractive index (RI) of the scatterers. The RL was based on a laser media containing suspensions of QtzNPs or ASNPs in Rhodamine 6G (Rh6G) and ethylene glycol (EG) suspension. It was observed a considerable increase in RL efficiency for QtzNPs, as compared to ASNPs, even for concentrations as low as 0.5mg/mL. Such grow in the RL eficiency is attributed to the higher RI of QtzNPs (n=1.54), which increases the reflectance of light on the particles surface and the high field scattering intensity in the sharp edges of the flat slab shapes, associated to the particle's morphology. Finite Element Method (FEM) simulations were also performed for different particle size and shapes and an output increase is noticed for QtzNPs when compared with the ASNP confirming the experimental results. The comparison between the morphology of QtzNPs and ASNPs on scattering efficiency reported here contribute to optimize the performance of laser systems with natural and synthetic nanomaterials.

In this work, we developed and investigated a random laser (RL) based on Rhodamine6G (Rh6G) in ethanol solution with quartzite nanoparticles as scatters in the lasing media.

Homologues and xenogenous bones are currently the most used grafts in dentistry because of their performance. However, some inherent disadvantages of these materials have not yet been overcome, such as the lack of biological properties to improve the new bone formation in situ and the long remodeling time. The main aim of this work was to improve the performance of the commercial bone-based grafts and study its properties in vitro. For this purpose, rat bone was combined with bioglass, a synthetic biomaterial that displays high degradation kinetics and bioactivity properties, endowed with biological properties. The sol-gel method was used for 45S5 bioglass (45S5) synthesis, using TEOS and water soluble salts as starting materials. 45S5 was then associated with the rat bone, generating the new graft. FTIR results indicated the hydroxyapatite formation after the bioactivity tests. SEM and bioactivity results were used to assess the evolution of the graft. The bioactivity tests showed that after 30 days the mass gain of about 30 wt.% was due to the deposition of hydroxyapatite crystals at the surface of the grafts, suggesting the potential properties of this new graft for application in implantology.

Photonic materials featuring simultaneous iridescence and light emission are an attractive alternative for designing novel optical devices. The luminescence study of a new optical material that integrates light emission and iridescence through liquid crystal self-assembly of cellulose nanocrystal-template silica approach is herein presented. These materials containing Rhodamine 6G were obtained as freestanding composite films with a chiral nematic organization. The scanning electron microscopy confirms that the cellulose nanocrystal film structure comprises multi-domain Bragg reflectors and the optical properties of these films can be tuned through changes in the relative content of silica/cellulose nanocrystals. Moreover, the incorporation of the light-emitting compound allows a complementary control of the optical properties. Overall, such findings demonstrated that the photonic structure plays the role of direction-dependent inner-filter, causing selective suppression of the light emitted with angle-dependent detection.

Sugarcane bagasse (SB) is made up of cellulose (32-43%), hemicellulose (19-34%) and lignin (14-30%). Due to high recalcitrant nature of SB, pretreatment is required to deconstruct its structure and enrich the cellulosic fraction. A two-stage NaOH and maleic acid pretreatment was applied to SB to enrich its cellulosic fraction. SB used in the present study is composed of cellulose (40.4 wt%), hemicellulose (20.9 wt%), lignin (22.5 wt%) and ash (4.0 wt%). After one-stage NaOH pretreatment, its cellulosic fraction increased to 61.8 wt% and later increased to 80.1 wt% after the second-stage acid pretreatment. Lignin fraction decreased to 3.0 wt% after one-stage NaOH pretreatment and remained unaffected after the acid pretreatment step. Hemicellulose fraction decreased substantially after the second-stage pretreatment with maleic acid. Pretreated SB displayed high crystallinity index and improved enzymatic digestibility. Hydrolysates of pretreated SB contained very low amount of xylose and subsequent fermentation by Saccharomyces cerevisiae -IQAr/45-1 resulted to ethanol level of 8.94 g/L. Maximal ethanol yield of 0.49 g/g (95.8% of theoretical yield) and productivity of 0.28 g/L/h was attained. At the same time, biomass yield and productivity of 0.47 g/g and 0.27 g/L/h respectively were obtained. Two-stage NaOH and maleic acid pretreatment led to ~ two-fold increase in cellulosic fraction and enhanced the enzymatic digestibility of SB up to 70.4%. The resulted enzymatic hydrolysate was efficiently utilized by S. cerevisiae -IQAr/45-1 to produce high yield of ethanol. Thus, optimization of enzymatic hydrolysis at low enzyme loading is expected to further improve the process and reduce cost.

Luminescent solar concentrators (LSCs) are photovoltaic (PV) complementary devices to overcome the mismatch between the Si-based PV cells, response and the solar spectrum, allowing PV urban integration. Challenges for the luminescent layer include the use of abundant and sustainable natural organic molecules. Here, LSCs composed of a glass container and based on bundles of cylindrical hollow-core plastic optical fibers filled with aqueous solutions of R-phycoerythrin (R-PE), extracted from Gracilaria sp. algae are presented. The R-PE solutions absorb in the UV/visible spectral range (300-550 nm) and convert this radiation into red-emission (550-700 nm) with a maximum absolute quantum yield of approximate to 0.39. In this work, LSCs with distinct geometries are reported, in which the R-PE emission yields optical conversion efficiency values up to approximate to 6.88% and approximate to 4.74% for a planar device and for a bundle of cylindrical LSCs, respectively, which are the largest values known for liquid-based LCSs using sustainable emitting centres. Moreover, the coupling of the LSCs to commercial Si-based PV devices yields power conversion efficiency values of approximate to 0.27% (planar) and approximate to 23.03 x 10(-3)%, (bundle). These values illustrate the potential of this approach for the development of natural-based LSCs meeting the requirements of reliable, sustainable, and competitive energy systems.

Due to the growing demand for renewable energy, the energy based on biomass plays an important role in energy policies of countries all over the world. Seven different pretreatments were performed on SCB to obtain yields, chemical composition, particle sizes and crystallinity indexes. The tools used to study the effects of pretreatments on SCB were X-ray diffraction (change in crystalline and amorphous regions) and SEM images. The application of microwave-assisted irradiation allowed the obtaining of the lowest cellulose removal with the fractions PT-6 and PT-7. FTIR spectra showed the removal of hemicellulose and lignin content during pretreatments. DP values decreased significantly suggesting higher digestibility of the seven cellulosic fractions by cellulolytic enzymes. In the present work, the presence of cellulose, hemicellulose and lignin structures in the sample of sugarcane bagasse and cellulosic fractions were indicated by the characteristic absorption bands (cm−1) of groups shown by the FTIR spectrum for hemicellulose and lignin. SEM images showed extensive degradation of the buddle of fibers of some cellulosic fractions. Mass loss (ML) obtained with SCB and cellulosic fractions were much greater under O2 atmosphere than under N2 atmosphere. The most relevant novelty of the present research was the use of chemical and physical methodologies to characterize sugarcane bagasse and their cellulosic fractions. The objective of this work was to determine the chemical composition and physical characteristics such as particle sizes as well as the removal of components resulting from seven different pretreatments. Nevertheless, future work is greatly required for improvement in this area.

Mullite is a low cost ceramic material based on aluminous silicate and synthesized via solid state reaction. Mullite displays potential properties for application in the biomedical field, specially its high mechanical strength, however it is poorly characterized with respect to its specific cytotoxicity and capability to allow the cell adhesion to its surface. Here, mullite was prepared by sintering the mixture of Al2O3 and SiO2 at 1500°C and characterized. Its elastic modulus was 135GPa and its flexural strength, 109MPa. The study of the viability of GM07492 human cells in presence of mullite revealed the proliferation and adhesion of the cells on its surface, which is an indication of biocompatibility. Its good mechanical properties and cytocompatibility suggested that mullite can be used as an alternative material for biomedical applications and dentistry.

In this work, we developed and investigated a random laser based on rhodamine6G (Rh6G) in ethylene glycol (EG) solution with varying cellulose nanocrystalline (CNC) needles as scatterers in the lasing media. Besides the suspension-in-cuvette scheme, an alternative configuration was also employed: a dye-CNC flexible self-supported thick-film (70 µm) random laser made by drop casting of the C N C s + R h 6 G + h y d r o x y p r o p y l cellulose suspension. In relation to conventional scatterers, the biodegradable cellulose nanocompounds showed a comparable reduction in both the spectral full width at half-maximum and the energy threshold values, with an optimal concentration of 5 mg [CNC]/ml[EG] in suspension. Its performance was also compared with other cellulose-based random lasers, presenting advantages for some parameters. The flexible film configuration showed similar results, but contained 10% less Rh6G than the suspension.

Silica aerogel is a lightweight material, well known for its good mechanical and thermal characteristics, but its optical properties have received less attention, because it is weakly scattering. Here we present for the first time the lasing properties and their complex dynamics of silica aerogel doped with R6G. It is shown that the Q factors of the lasing modes determine the operation of the laser, being either resonant or ASE-lasing. For resonant lasing, the number of resonators is easily varied and the number of modes in a single resonator and their emission frequency can be dynamically adjusted, making this a truly versatile photonics material.

Luminescent solar concentrators (LSCs) are luminescent waveguide layers that convert sunlight into specific wavelengths which are then guided by total internal reflection to a PV device located at the edges of the LSC. Their ability to concentrate sunlight onto small areas makes LSCs a useful complement to silicon-based PVs in a series of applications, such as urban integration and flexible fabrics towards mobile solar-energy. Challenges for the luminescent layer include the use of low-cost and sustainable nature-based organic molecules. We report novel chlorophyll-based LSCs with emission properties in the red/NIR spectral region. Here, chlorophyll molecules extracted from Spirulina maxima, an abundant cyanobacterium and an attractive natural source, are immobilized in organic–inorganic di- and tri-ureasil matrices enabling the production of sustainable LSCs. At low chlorophyll concentrations (<3 × 1017 molecules per cm3), the photophysical properties of the chlorophyll molecules after incorporation into the hybrids closely resemble those in ethanolic solution (with an absolute emission quantum yield of ∼0.16 and a fluorescence lifetime of ∼8 ns). The LSCs were coupled to a Si-based commercial PV device revealing optical conversion efficiency and power conversion efficiency values of ∼3.70% and 0.10%, respectively, illustrating the potential of this approach for the development of nature-based LSCs meeting the requirements of reliable, sustainable and competitive energy systems.

Luminescent solar concentrators (LSCs) appear as an intriguing way to cope with the limitation of the mismatch between the photovoltaic (PV) cells response and the solar spectrum, with the additional advantage of facilitating urban integration of photovoltaics. A new LSCs geometry based on triangular hollow‐core plastic optical fibers (POFs) filled with organic–inorganic hybrid materials doped with Rhodamine 6G, Rhodamine 800, or an Europium β‐diketonate complex is presented. Large‐area LSCs are built from POFs bundle structures, whose assembling is favored by the fiber triangular cross section that also maximizes the coverage of a PV cell surface compared with cylindrical POFs. Each bundle fiber behaves as an individual LSC absorbing UV/blue components of the solar spectrum and emitting visible/NIR radiation. The LSCs are characterized by optical conversion efficiency values up to ηopt ≈5.3%, among the largest values reported for single‐layer LSCs. Moreover, the coupling between the LSCs to commercial Si PV cells yields maximum power conversion efficiency values of PCE ≈0.74%. The individual waveguiding features of each fiber in the bundle contribute to reduce the reabsorption, as lower performance values (ηopt ≈1.5%; PCE ≈0.09%) are estimated for a planar LSC with analogous surface collection area and light‐harvesting absorbance.

Photoluminescence properties of single bead silica-gel (SG) embedded with a laser-dye were studied aiming at the operation of near-infrared (NIR) Random Lasers (RLs). The operation of RLs in the NIR spectral region is especially important for biological applications since the optical radiation has deep tissue penetration with negligible damage. Since laser-dyes operating in the NIR have poor stability and are poor emitters, ethanol solutions of Rhodamine 640 (Rh640) infiltrated in SG beads were used. The Rh640 concentrations in ethanol varied from 10−5 to 10−2 M and the excitation at 532 nm was made by using a 7 ns pulsed laser. The proof-of-principle RL scheme herein presented was adopted in order to protect the dye-molecules from the environment and to favor formation of aggregates. The RL emission from ≈650 nm to 720 nm, beyond the typical Rh640 monomer and dimer wavelengths emissions range, was attributed to the trade-off between reabsorption and reemission processes along the light pathways inside the SG bead and the contribution of Rh640 aggregates.

The evolution of research on luminescent phosphors led to research on materials doped with rare earth ions (RE3+), not only because of their photoluminescent properties, but also for their potential applications in photonics. The search for new photoluminescent materials has led to an investigation of the photoluminescence of RE3+ present in an aluminum oxide (Al2O3) matrix. This oxide has a transparent window on the short ultraviolet to near infrared, excellent mechanical properties and good chemical stability. Within this context, this work aims to obtain Al2O3: Er3+/Yb3+. The preparation of Al2O3:Er3+/Yb(3+ )involved two synthesis processes. For the co-precipitation process, rings of aluminum cans were used as precursors, and for the sol-gel process, the precursor used was tri-sec-butoxide aluminum. From the XRD results, high heat-treatment temperatures were observed to favor the formation of the alpha-Al2O3 phase and low temperatures were observed to favor the formation the gamma-Al2O3 phase. The analysis of the photoluminescence emission spectra when excited at 980 nm, showed the up-conversion phenomenon with an emission in the visible region. The emission spectra also showed emission between 1400 and 1650 nm, with a maximum at about 1530 nm. The materials exhibit efficient energy absorption in the infrared region, with light emission in the visible region. Furthermore, the spectra show an intense emission in the infrared region assigned to the I-4(13/2 )-> I-4(15/2) transition of Er3+, demonstrating excellent potential to be used in optical amplifier device at the third telecommunications window.

Bombyx mori silk fibroin offers unlimited opportunities for functionalization, processing, and biological integration.

45S5 bioglass has been widely studied in the last few decades because of its bioactivity and promising applications in the biomedical field. Boron, even few studied, represents a potential element to improve the properties of the 45S5 bioglass derivatives. The bioglasses are conventionally prepared by heat treatment of oxides and silicon. Here, the sol−gel method is proposed for the preparation of the boron-based 45S5 bioglass (45S5B) and the classical 45S5 bioglass (45S5), using water-soluble salts as raw materials. The bioglasses were characterized by FTIR, XRD, and SEM, indicating the success of the sol−gel method for preparation of the samples. The bioglasses were also tested in vitro for bioactivity in biological conditions and cytotoxicity against eukaryotic cells. The bioactivity of 45S5B was similar to the bioactivity of 45S5 bioglass, indicated by the deposition of hydroxyapatite crystals at the surface of the pristine bioglasses. The results of cytotoxicity tests revealed that the IC 50 of 45S5B (IC 50 = 7.56 mg mL −1 ) was similar to the IC 50 of 45S5 (IC 50 = 8.15 mg mL −1 ), indicating its safety for application in the biomedical field.