•The natural renewable biopolymer bacterial cellulose was carefully described.•Bacterial cellulose main applications are wound dressings, burning and ulcers.•Blood vessels, contact lens, dental ...implants and other applications were reviewed.•Challenging tissues such as cartilage, nerves and urethra were successfully regenerated.•More work and novel applications are expected due to the high-value-added of bacterial cellulose.
Bacterial cellulose (BC) produced by some bacteria, among them Gluconacetobacter xylinum, which secrets an abundant 3D networks fibrils, represents an interesting emerging biocompatible nanomaterial. Since its discovery BC has shown tremendous potential in a wide range of biomedical applications, such as artificial skin, artificial blood vessels and microvessels, wound dressing, among others. BC can be easily manipulated to improve its properties and/or functionalities resulting in several BC based nanocomposites. As example BC/collagen, BC/gelatin, BC/Fibroin, BC/Chitosan, etc. Thus, the aim of this review is to discuss about the applicability in biomedicine by demonstrating a variety of forms of this biopolymer highlighting in detail some qualities of bacterial cellulose. Therefore, various biomedical applications ranging from implants and scaffolds, carriers for drug delivery, wound-dressing materials, etc. that were reported until date will be presented.
Interest in lanthanide‐containing organic–inorganic hybrids has grown considerably during the last decade, with the concomitant fabrication of materials with tunable attributes offering modulated ...properties. The potential of these materials relies on exploiting the synergy between the intrinsic characteristics of sol–gel derived hosts (highly controlled purity, versatile shaping and patterning, excellent optical quality, easy control of the refractive index, photosensitivity, encapsulation of large amounts of isolated emitting centers protected by the host) and the luminescence features of trivalent lanthanide ions (high luminescence quantum yield, narrow bandwidth, long‐lived emission, large Stokes shifts, ligand‐dependent luminescence sensitization). Promising applications may be envisaged, such as light‐emitting devices, active waveguides in the visible and near‐IR spectral regions, active coatings, and bio‐medical actuators and sensors, opening up exciting directions in materials science and related technologies with significant implications in the integration, miniaturization, and multifunctionalization of devices. This review provides an overview of the latest advances in Ln3+‐containing siloxane‐based hybrids, with emphasis on the different possible synthetic strategies, photoluminescence features, empirical determination
Ln3+‐containing siloxane‐based hybrids and the latest advances in this field are reviewed. Interest in these materials has grown considerably during the last decade, with the concomitant fabrication of materials with tunable attributes and offering modulated properties. These hybrids present good optical quality and chemical and mechanical properties, and the simple incorporation of active species allows tuning of absorption and emission colors.
Abstract
The determination of temperature is essential in many applications in the biomedical, technological, and industrial fields. Optical thermometry appears to be an excellent alternative for ...conventional electric temperature sensors because it is a non-contact method that offers a fast response, electromagnetic passivity, and high temperature sensitivity. In this paper, we propose an optical thermometer probe comprising an Er
3+
/Yb
3+
co-doped tellurite glass attached to the tip of an optical fibre and optically coupled to a laser source and a portable USB spectrometer. The ratio of the up-conversion green emission integrated peak areas when excited at 980 nm was temperature dependent, and it was used to calibrate the thermometer. The thermometer was operated in the range of 5–50 °C and 50–200 °C, and it revealed excellent linearity (
r
2
> 0.99), suitable accuracy, and precisions of ±0.5 and ±1.1 °C, respectively. By optimizing Er
3+
concentration, we could obtain the high green emission intensity, and in turn, high thermal sensitivity for the probe. The probe fabricated in the study exhibited suitable properties for its application as a temperature sensor and superior performance compared to other Er
3+
-based optical thermometers in terms of thermal sensitivity.
Luminescent solar concentrators (LSCs) are devices comprising a transparent matrix embedding optically active centres that absorb the incident radiation, which is re-emitted at a specific wavelength ...and transferred by total internal reflection to photovoltaic (PV) cells located at the edges of the matrix. Organic–inorganic hybrids incarcerating trivalent lanthanide ions (Ln 3+ ) are a very promising class of materials for addressing the required challenges in the LSC design to improve solar energy harvesting and, then, PV energy conversion. This feature article offers a general overview of the potential of down-shifting-based Ln 3+ -containing organic–inorganic hybrids for the development of the area with special focus on (i) optically active layer design, (ii) energy conversion mechanisms, (iii) performance and geometry and (iv) figures of merit in PV cell enhancement. Finally, a prospective outlook on future progress, e.g. optically active centre alignment, geometry optimization and building integration, is provided. The use of Ln 3+ -containing hybrids in LSCs is at an infant initial research step and considerable basic knowledge is still needed to enable prototypes to become a commercial reality.
To address the problems associated with the use of unsupported nanomaterials, in general, and molybdenum disulfide (MoS2), in particular, we report the preparation of self-supported hybrid aerogel ...membranes that combine the mechanical stability and excellent textural properties of bacterial nanocellulose (BC)-based organic macro/mesoporous scaffolds with the excellent adsorption-cum-photocatalytic properties and high contaminant removal performance of MoS2 nanostructures. A controlled hydrothermal growth and precise tuning of the synthetic parameters allowed us to obtain BC/MoS2-based porous, self-supported, and stable hybrid aerogels with a unique morphology resulting from a molecular precision in the coating of quantum-confined photocatalytic MoS2 nanostructures (2–4 nm crystallite size) on BC nanofibrils. These BC/MoS2 samples exhibit high surface area (97–137 m2·g–1) and pore volume (0.28–0.36 cm3·g–1) and controlled interlayer distances (0.62–1.05 nm) in the MoS2 nanostructures. Modification of BC with nanostructured MoS2 led to an enhanced pollutants removal efficiency of the hybrid aerogels both by adsorptive and photocatalytic mechanisms, as indicated by a detailed study using a specifically designed membrane photoreactor containing the developed photoactive/adsorptive BC/MoS2 hybrid membranes. Most importantly, the prepared BC/MoS2 aerogel membranes showed high performance in the photoassisted in-flow removal of both organic dye (methylene blue (MB)) molecules (96% removal within 120 min, K obs = 0.0267 min–1) and heavy metal ions (88% Cr(VI) removal within 120 min, K obs = 0.0012 min–1), separately and/or simultaneously, under UV–visible light illumination as well as excellent recyclability and photostability. Samples with interlayer expanded MoS2 nanostructures were particularly more efficient in the removal of smaller species (CrO4 2–) as compared to larger (MB) dye molecules. The prepared hybrid aerogel membranes show promising behavior for application in in-flow water purification, representing a significant advancement in the use of self-supported aerogel membranes for photocatalytic applications in liquid media.
The pursuit of biocompatible, breathable and skin-conformable wearable sensors has predominantly focused on synthetic stretchable hydrophobic polymers. Microbial nanocellulose (MNC) is an exceptional ...skin-substitute natural polymer routinely used for wound dressing and offers unprecedented potential as substrate for wearable sensors. A versatile strategy for engineering wearable sensing platforms is reported, with sensing units made of screen-printed carbon electrodes (SPCEs) on MNC. As-prepared SPCEs were used to detect the toxic metals cadmium (Cd2+) and lead (Pb2+) with limits of detection of 1.01 and 0.43 μM, respectively, which are sufficient to detect these metal ions in human sweat and urine. SPCEs functionalized through anodic pre-treatments were used for detecting uric acid and 17β-estradiol in artificial sweat, with detection limits of 1.8 μM and 0.58 μM, respectively. The electrochemical treatment created oxygen groups on the carbon surfaces, thus improving wettability and hydrophilicity. MNC was herein exploited as an adhesive-free, yet highly skin-adherent platform for wearable sensing devices that also benefit from the semi-permeable, non-allergenic, and renewable features that make MNC unique within the pool of materials that have been used for such a purpose. Our findings have clear implications for the developments on greener and more biocompatible but still efficient substrates and may pave the route for combining immunosensing devices with drug delivery therapies.
Display omitted
•Skin-adherent biosensors based on pure nanocellulose fibers substrate.•SPCE on MNC enables the detection of uric acid, 17β-estradiol, Pb2+ and Cd2+ in sweat.•MNC membranes allow optimal skin integration in wearable technologies.
Near‐infrared (NIR) nanothermometers are sought after in biomedicine when it comes to measuring temperatures subcutaneously. Yet, temperature sensing within the third biological imaging window ...(BW‐III), where the highest contrast images can be obtained, remains relatively unexplored. Here, LiErF4/LiYF4 rare‐earth nanoparticles (RENPs) are studied as NIR nanothermometers in the BW‐III. Under 793 nm excitation, LiErF4/LiYF4 RENPs emit around 1540 nm, corresponding to the 4I13/2 → 4I15/2 radiative transition of Er3+. The fine Stark structure of this transition allows to delineate intensity regions within the emission band that can be used for single‐band ratiometric nanothermometry. These nanothermometers have a relative temperature sensitivity of ≈0.40% °C−1. The temperature‐dependent energy transfer to the surrounding solvent molecules plays a significant role in the thermometric properties of the RENPs. In addition, Ce3+ ions are doped in the core of the RENPs to examine whether it affects the NIR emission and temperature sensitivity. Ce3+ at 1 mol% marginally influences the downshifting emission intensity of the RENPs, yet increases the relative thermal sensitivity to ≈0.45% °C−1. Furthermore, Ce3+ quenches the visible upconversion emission of the RENPs. Together, LiErF4:Ce3+/LiYF4 RENPs enable single‐band photoluminescence nanothermometry in the BW‐III, with the future possibility of its integration within multifunctional decoupled theranostic nanostructures.
Er3+ near‐infrared (NIR) emission is harnessed for temperature sensing in the third optical imaging window. Single‐band nanothermometry around 1.54 µm can be achieved in water‐dispersed Li+‐based rare earth nanoparticles, while additional Ce3+ doping can suppress the sometimes undesirable visible upconversion emission. Thermometric behavior and potential for real‐life application of this luminescence thermometry approach are thoroughly examined.
•BC were successfully used for the fabrication of antimicrobial nanocomposites by hydrothermal deposition of Cu derivative nanoparticles.•The nanoparticles over BC became more compact and smother for ...longer heating times and this increase lead to decrease of BC crystallinity.•BC-Cu nanocomposites showed antimicrobial activity in vitro against Gram-positive and Gram-negative bacterial species and yeast C. albicans.
In this work, for the first time bacterial cellulose (BC) hydrogel membranes were used for the fabrication of antimicrobial cellulosic nanocomposites by hydrothermal deposition of Cu derivative nanoparticles (i.e.Cu(0) and CuxOy species). BC-Cu nanocomposites were characterized by FTIR, SEM, AFM, XRD and TGA, to study the effect of hydrothermal processing time on the final physicochemical properties of final products. XRD result show that depending on heating time (3–48h), different CuxOy phases were achieved. SEM and AFM analyses unveil the presence of the Cu(0) and copper CuxOy nanoparticles over BC fibrils while the surface of 3D network became more compact and smother for longer heating times. Furthermore, the increase of heating time placed deleterious effect on the structure of BC network leading to decrease of BC crystallinity as well as of the on-set degradation temperature. Notwithstanding, BC-Cu nanocomposites showed excellent antimicrobial activity against E. coli, S. aureus and Salmonella bacteria suggesting potential applications as bactericidal films.
Natural rubber (NR) is a renewable polymer with a wide range of applications, which is constantly tailored, further increasing its utilizations. The tensile strength is one of its most important ...properties susceptible of being enhanced by the simple incorporation of nanofibers. The preparation and characterization of natural-rubber based nanocomposites reinforced with bacterial cellulose (BC) and bacterial cellulose coated with polystyrene (BCPS), yielded high performance materials. The nanocomposites were prepared by a simple and green process, and characterized by tensile tests, dynamical mechanical analysis (DMA), scanning electron microscopy (SEM), and swelling experiments. The effect of the nanofiber content on morphology, static, and dynamic mechanical properties was also investigated. The results showed an increase in the mechanical properties, such as Young’s modulus and tensile strength, even with modest nanofiber loadings.
PDF
