Transparent and conductive paper from nanocellulose fibers

Abstract

Here we report on a novel substrate, nanopaper, made of cellulose nanofibrils, an earth abundant material.Compared with regular paper substrates, nanopaper shows superior optical properties. We have carried out the first study on the optical properties of nanopaper substrates. Since the size of the nanofibrils is much less than the wavelength of visible light, nanopaper is highly transparent with large light scattering in the forward direction. Successful depositions of transparent and conductive materials including tin-doped indium oxide, carbon nanotubes and silver nanowires have been achieved on nanopaper substrates, opening up a wide range of applications in optoelectronics such as displays, touch screens and interactive paper. We have also successfully demonstrated an organic solar cell on the novel substrate. Broader contextWood ber cellulose has been used for more than 2000 years as an ingredient for making paper. The cellulose paper that we see in our everyday lives consists of bers with diameters of tens of micrometers. Using chemical or enzymatic pretreatments followed by high-pressure homogenization, the micrometer-sized cellulose bers can be disintegrated into nanobrillated cellulose (NFC) with a diameter of around 10-20 nm and a length of 2 mm. By compressing the NFC pulp with the right composition in a sheet-former, highly transparent nanocellulose paper can be produced. The nanocellulose paper has large light scattering in the forward direction, which is very useful for solar cell applications. The nanocellulose paper can be coated with a wide variety of conductive materials, such as carbon nanotubes, silver nanowires and tin-doped indium oxide (ITO), to produce transparent conductive paper. By depositing a thin layer of ITO, the conductive nanocellulose paper can be used as a substrate for making organic solar cells.

Nanocellulose in Thin Films, Coatings, and Plies for Packaging Applications: A Review

“…Hu et al (2013) showed that nanocellulose films could be rendered conductive by deposition of tindoped indium oxide, while still retaining their transparency; solar cells prepared with such films were successfully demonstrated. In general, it has been found that good transparency can be achieved as long as the cellulosic material is small enough, fully wetted by the matrix material (if any) in the layer, and not clumped up or entangled.…”

“…A number of researchers have demonstrated such a process when using nano-fibrillated cellulose (Nakagaito and Yano 2004Henriksson et al 2008;Nogi et al 2009;Syverud and Stenius 2009;Sehaqui et al 2010Sehaqui et al , 2011Larsson et al 2012;Hu et al 2013;Rojo et al 2015). Keshvarzi et al (2015) prepared paper-like films from a gelled mixture of nanocellulose and zeolites.…”

“…They also demonstrated a large difference in properties, depending on which of the successive layers was the last to be deposited in a multilayer film structure. By incorporating tin-doped indium oxide, carbon nanotubes, and silver nanowires into a multilayer structure with nanocellulose, Hu et al (2013) prepared films that were electrically conductive, in addition to being transparent.…”

“…They also demonstrated a large difference in properties, depending on which of the successive layers was the last to be deposited in a multilayer film structure. By incorporating tin-doped indium oxide, carbon nanotubes, and silver nanowires into a multilayer structure with nanocellulose, Hu et al (2013) prepared films that were electrically conductive, in addition to being transparent.Application procedures for polyelectrolyte multilayer deposition are inherently slow, relative to high-speed manufacturing processes. Time is required at each step for the respective polyelectrolyte to diffuse from a solution and form a charged complex with the REVIEW ARTICLE bioresources.com .…”

Cellulose nanopapers as tight aqueous ultra-filtration membranes

“…Nanocellulose (NFC) has gained considerable attention in recent years due to its outstanding mechanical and chemical properties [9,10], especially when used in composites [11,12]. Nanocellulose used in paper form, herein termed nanopapers, possesses excellent mechanical properties, low thermal expansion coefficients, high optical transparency and good gas barrier properties [13][14][15][16][17][18][19][20].…”