Transparent wood composites (TWs) offer the possibility of unique coloration effects. A colored transparent wood composite (C-TW) with enhanced fire retardancy was impregnated by metal ion solutions, followed by methyl methacrylate (MMA) impregnation and polymerization. Bleached birch wood with a preserved hierarchical structure acted as a host for metal ions. Cobalt, nickel, copper, and iron metal salts were used. The location and distribution of metal ions in C-TW as well as the mechanical performance, optical properties, and fire retardancy were investigated. The C-TW coloration is tunable by controlling the metal ion species and concentration. The metal ions reduced heat release rates and limited the production of smoke during forced combustion tests. The potential for scaled-up production was verified by fabricating samples with a dimension of 180 x 100 x 1 (l x b x h) mm(3).

The preparation of wood substrates modified by charged inorganic nanoparticles (NPs) diffusing into the internal cell wall structure is investigated for generating functional properties. The flammability problem of wood biocomposites is addressed. NPs applied from colloidal sols carry charge to stabilize them against aggregation. The influence of charge on particle diffusion and adsorption should play a role for their spatial distribution and localization in the wood substrate biocomposite. It is hypothesized that improved dispersion, infiltration, and stability of NPs into the wood structure can be achieved by charge control diffusion, also restricting NP agglomeration and limiting distribution to the wood cell wall. Cationic and anionic silica NPs of ≈30 nm are therefore allowed to diffuse into bleached wood. The influence of charge on distribution in wood is investigated as a function of initial sol concentration. Transparent wood is fabricated by in situ polymerization of a thiol­ene in the wood pore space. These biocomposites demonstrate excellent flame retardancy with self­extinguishing characteristics. The approach has potential for commercial fabrication of flame retardant transparent composites for glazing and other building applications.

Transparent wood (TW) biocomposites combine high optical transmittance and good mechanical properties and can contribute to sustainable development. The safety against fire is important for building applications. Here, a "green" bleached wood reinforcement is impregnated by water soluble and flame-retardant melamine formaldehyde (MF) in a scalable process, for a wood content of 25 vol%. FE-SEM is used for characterization of optical defects and EDX to examine MF distribution at nanoscale cell wall pore space. Curing (FTIR-ATR), mechanical properties, optical transmittance (74% at 1.2 mm thickness) and flame-retardant properties are also characterized (self-extinguishing behavior and cone calorimetry), and scattering mechanisms are discussed. The fire growth rate of transparent wood was less than half the values for neat wood. Transparent wood/MF biocomposites show interesting wood-MF synergies and are of practical interest in building applications. Critical aspects of processing are analyzed for minimization of optical defects.

A concept of transparent “quantum dot glass”(TQDG) is proposed for a combination of a quantum dot(QD)-based glass luminescent solar concentrator (LSC) and itsedge-attached solar cells, as a type of transparent photovoltaics(TPVs) for building-integrated photovoltaics (BIPVs). Differentfrom conventional LSCs, which typically serve as pure opticaldevices, TQDGs have to fulfill requirements as both powergeneratingcomponents and building construction materials. In thiswork, we demonstrate large-area (400 cm2) TQDGs based onsilicon QDs in a triplex glass configuration. An overall powerconversion efficiency (PCE) of 1.57% was obtained with back-reflection for a transparent TQDG (average visible transmittance of84% with a color rendering index of 88 and a low haze ≤3%), contributing to a light utilization efficiency (LUE) of 1.3%, which isamong the top reported TPVs based on the LSC technology with similar size. Most importantly, these TQDGs are shown to havebetter thermal and sound insulation properties compared to normal float glass, as well as improved mechanical performance andsafety, which significantly pushes the TPV technology toward practical building integration. TQDGs simultaneously exhibit favorablephotovoltaic, aesthetic, and building envelope characteristics and can serve as a multifunctional material for the realization of nearlyzero-energy building concepts.

Transparent wood (TW), a biocomposite material demonstrating optical transparency in the visible range, has attracted much interest in recent years due to great potential for ecofriendly applications, for instance, in construction industry and functionalized organic materials. Optical properties of TW, including transparency and haze, depend on a particular structure of cellulose-based backbone compound, (mis-)matching of the refractive indices (RIs) between TW compounds, and the polymer matrix. Although there are data of cellulose RIs for various forms of cellulose (fibers, powder, hot-pressed films, etc.), these values might differ from an effective RI of the TW substrate. Herein, a numerical model of light propagation in the TW, based on the real cellular structure in wood, is presented and applied to estimate an effective RI of the delignified wood reinforcement in the experimentally investigated TW material. Ray-tracing and rigorous electromagnetic approaches are compared for modeling light propagation in the TW. Ray tracing demonstrates considerably simplified yet accurate and efficient solutions. The work brings substantial progress toward realistic and practical wood modeling for the purpose of applications, materials design, and fundamental studies.

As a cost-effective batch synthesis method, Si quantum dots (QDs) with nearinfrared photoluminescence, high quantum yield (>50% in polymer nanocomposite), and nearunity internal quantum efficiency were fabricated from an inexpensive commercial precursor (triethoxysilane, TES), using optimized annealing and etching processes. The optical properties of such QDs are similar to those prepared from state-of-the-art precursors (hydrogen silsesquioxane, HSQ) yet featuring an order of magnitude lower cost. To understand the effect of synthesis parameters on QD optical properties, we conducted a thorough comparison study between common solid precursors: TES, HSQ, and silicon monoxide (SiO), including chemical, structural, and optical characterizations. We found that the structural nonuniformity and abundance of oxide inherent to SiO limited the resultant QD performance, while for TES-derived QDs this drawback can be avoided. The presented low-cost synthetic approach would significantly favor applications requiring high loading of good-quality Si QDs, such as light conversion for photovoltaics.

Transparent wood (TW)-based composites are of significant interest for smart window applications. In this research, we demonstrate a facile dual-stimuli-responsive chromic TW where optical properties are reversibly controlled in response to changes in temperature and UV-radiation. For this functionality, bleached wood was impregnated with solvent-free thiol and ene monomers containing chromic components, consisting of a mixture of thermo- and photoresponsive chromophores, and was then UV-polymerized. Independent optical properties of individual chromic components were retained in the compositional mixture. This allowed to enhance the absolute optical transmission to 4 times above the phase change temperature. At the same time, the transmission at 550 nm could be reduced 11−77%, on exposure to UV by changing the concentration of chromic components. Chromic components were localized inside the lumen of the wood structure, and durable reversible optical properties were demonstrated by multiple cycling testing. In addition, the chromic TW composites showed reversible energy absorption capabilities for heat storage applications and demonstrated an enhancement of 64% in the tensile modulus as compared to a native thiol−ene polymer. This study elucidates the polymerization process and effect of chromic components distribution and composition on the material’s performance and perspectives toward the development of smart photoresponsive windows with energy storage capabilities.

A straightforward process that enabled electrospinning of bioactive starch-based nanofiber scaffolds was developed by utilizing starch derived nano graphene oxide (nGO) as a property enhancer and formic acid as a solvent and esterification reagent. The reaction mechanism and process were followed by detailed spectroscopic investigation. Furthermore, the incorporation of nGO as a “green bioactive additive” endorsed starch nanofibrous scaffolds several advantageous functionalities including improved electrospinnability and thermal stability, good cytocompatibility, osteo-bioactivity, and retained biodegradability. The biodegradable starch/nGO nanofibers underwent simultaneous degradation and mineralization process during 1 week of cell culture and mineralization test, thus, mimicking the structure and function of extracellular matrices (ECMs) and indicating promise for bone tissue engineering applications.

A liquid flow through a channel is studied based on the Orr-Sommerfeld eigenvalue problem, where the lower wall of the channel is occupied by the saturated poroelastic medium. The linear stability analysis is investigated in detail for arbitrary value of the wavenumber. The eigenvalues are computed numerically by using the Chebyshev spectral collocation method. The effect of physical parameters, for instance, permeability, elasticity as well as their combined effect on the unstable modes are examined.