Cellulose (2023) 30:5447–5471
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quantum dots to ETW resulted in multi colour lumi- nescence that can be used for planar light sources, building construction elements and furniture (Li et al. 2017b). Yu et al. (2017) produced CsxWO 3 -ETW with an optical transmittance of 86% and haze of 90%, temperature and humidity resistance (i.e. excel- lent shielding ability of near-infrared ranging from 780 to 2500 nm). Additionally, the mechanically properties (tensile strength = 60.1 MPa, and modu- lus = 2.72 GPa fracture strength = 59.8 MPa) of the CsxWO 3 -ETW were favourable for heat shield- ing window applications. The transmittance of the CsxWO3/ETW was observed to increase slowly in high temperature (85 °C) and humidity conditions (90% RH). Model houses were developed to com- pare the thermoregulation effects of CsxWO 3 /ETW to glass. After continuous application of solar radiation, the ordinary glass house model temperature increased from 21.5 °C to 41.5 °C whereas the CsxWO 3 -ETW model increased from 21.6 °C to 26.8 °C (Yu et al. 2017). Mi et al. (2020a) produced aesthetic ETW with preserved wood patterns by spatial selectively removing lignin from Douglas fir (softwood). The aesthetic wood possessed good mechanical properties (strength = 91.95 MPa, toughness = 2.73 MJm −3 ), low thermal conductivity (0.24Wm −1 K −1 ), and excel- lent optical properties (transparency ~ 80%, optical haze ~ 93%). These properties are desirable for pat- terned ceilings, rooftops, transparent decorations, and indoor panels (Mi et al. 2020a). Wang et al. (2019a) fabricated photochromic ETW containing 3’,3’-dime- thyl-6-nitro-spiro[2H-1-benzopyran-2,2’-indoline]- 1’-ethanol. The ETW exhibited a multi colour change under the illumination of light making it suitable for photo-switchable, and colourful smart windows (Wang et al. 2019a; Al-Qahtani et al. 2021).
overall conversion efficiency of GaAs with and with- out ETW was 18.02% and 12.21% respectively. It was concluded that ETW was efficient in broadband light management which led to efficient light scat- tering and adsorption within the solar cell, hence the improved conversion efficiency. Li et al. (2019b) fab- ricated photovoltaic cells on transparent wood sub- strates which led to a power conversion efficiency of 16.8%.
Other applications
Addition of γ-Fe2O3@YVO4:Eu3+and Fe3O4 nan- oparticles has been reported to reported to endow ETW with magnetic properties that were desirable in applications such as electromagnetic interference shielding, LED lighting equipment, luminescent mag- netic switches, and anti-counterfeiting facilities (Gan et al. 2017a, 2017b). ETW can be used in speciality applications such as smart phone screens (Magrini et al. 2021). Wang et al. (2022) produced ETW which possessed flexibility, solid shape plasticity, shape manipulation capabilities and unique guiding effects. The ETW was produced through polymerisation of epoxy-based dynamic covalent polymers into a delig- nified wood template. Applications such as curved or irregularly shaped glass, windows, ceilings, rooftops were suggested for the ETW (Wang et al. 2022). Bi et al. (2018) fabricated multi colour emission ETW containing carbon dots. The properties of the multi colour emission ETW exhibited excellent optical and mechanical properties desirable for use as encapsulat- ing material for white light-emitting diodes. Conclusion Generally, ETW was manufactured in two steps, i.e., delignification of wood and infiltration of RI match- ing polymers. The main focus in ETW production was reducing lignin or lignin chromophores while maintaining the structural integrity of wood, elimi- nating polymer cell wall interface gaps by improving polymer infiltration, improving the short and long term integrity of ETW, especially in outdoor appli- cations, by surface modification, and exploiting the natural characteristics of wood to the benefit of the ETW (e.g. aesthetic patterns) (Jia et al. 2019; Mi et al. 2020a).
Photovoltaic and optoelectronic devices
ETW are not only energy efficient but result in green disposable optoelectronic and photovoltaic devices (Zhu et al. 2016a). Fang et al. (2014) reported that a combination of high optical transparency and high optical haze is beneficial for solar cell substrates to adsorb active materials and increase the light scatter- ing thereby ensuring solar cell efficiency. Zhu et al. (2016a) compared the efficiency of GaAs (Gallium arsenide) solar with or without attachment of ETW (optical transmittance of 90% and haze of 80%). The
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