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• BC/ZnO nanocomposite strengthens paper and improves aging resistance. • The nanocomposite imparts antifungal properties to paper. • The nanocomposite helps in deacidification of paper. Paper, commonly used as an information carrier, can become acidified and brittle over time. In this study, 0.3 % bacterial cellulose (BC) composite with 1.0% zinc oxide (ZnO) nanoparticles was prepared and used to coat brittle book paper for deacidification and consolidation. The BC/ZnO nanocomposite was characterized using zeta potential, micro morphology, elemental mapping, X-ray photoelectron spectra, Fourier transform infrared, and thermogravimetric analyses. The results indicated that the composite exhibited good stability. ZnO nanoparticles were bonded to the hydroxyl groups on BC, enhancing the thermal stability of BC. The composite was uniformly sprayed on the paper surface, and the mechanical properties, color difference, readability, pH, and micromorphology of the paper samples were examined before and after the treatment. The BC/ZnO nanocomposite exhibited good deacidification and consolidation effects on paper samples with low impact on the original paper appearance. Moreover, the BC/ZnO nanocomposite showed a good inhibitory effect on fungi growth on paper. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sonication improves the absorption of metallic salt in the paper. • Ultrasound catalyzes the synthesis of metallic nanoparticles. • A longer sonication time during salt absorption increases the number of nanoparticles obtained. • Nanoparticles obtained by sonochemistry are an easy and reproducible method to modify paper. This work focuses on a systematic method to produce Ag, Cu, and Ag/Cu metallic nanoparticles (MNPs) in situ assisted with ultrasound on cellulose paper. By tuning the concentration of AgNO 3 and CuSO 4 salt precursors and ultrasound time, combined with a fixed concentration of ascorbic acid (AA) as a reducing agent, it was possible to control the size, morphology, and polydispersity of the resulting MNPs on cellulose papers. Notably, high yield and low polydispersity of MNPs and bimetallic nanoparticles are achieved by increasing the sonication time on paper samples pre-treated with salt precursors before reduction with AA. Moreover, mechanical analysis on paper samples presenting well-dispersed and distributed MNPs showed slightly decreasing values of Young's modulus compared to neat papers. The strain at break is substantially improved in papers containing solely Ag or Cu MNPs. The latter suggests that the elastic/plastic transition and deformation of papers are tuned by cellulose and MNPs interfacial interaction, as indicated by mechanical analysis. The proposed method provides insights into each factor affecting the sonochemistry in situ synthesis of MNPs on cellulose papers. In addition, it offers a straightforward alternative to scale up the production of MNPs on paper, ensuring an eco-friendly method. [ABSTRACT FROM AUTHOR]

Understanding water absorbency in paper is challenging as fibre swelling and out-of-plane deformation occur simultaneously during liquid imbibition. Liquid absorption is commonly accessed by gravimetric tests, which provides limited information on the local spatial and temporal distribution of fluid in the substrate. In this work, we developed iron tracers to map liquid imbibition in paper by in situ precipitation of iron oxide nanoparticles during passage of the wetting front. The iron oxide tracers were found to be robustly attached to the cellulosic fibres. After liquid absorption tests, absorbency was investigated by mapping the distribution of iron in 3D using X-ray micro-computed tomography (μCT) and in 2D using energy-dispersive X-ray spectroscopy. We demonstrate a difference in tracer distribution between the wetting front and the fully saturated region supporting that imbibition proceeds in two phases, i.e. liquid percolation through the cell wall initially prior to filling of the external pore spaces. Critically, we demonstrate that these iron tracers enhance image contrast and allow for new imaging modalities in μCT for fibre networks. [Display omitted] [ABSTRACT FROM AUTHOR]

The purpose of this article is to evaluate the potential risk of exposure to nanoparticles of workers in paper mills. In the final stage of the paper production, the very large sheets are wound onto large reels, where these are processed depending on their ultimate use. Paper is smoothed and compacted by passing through metal rollers. During these mechanical treatments nanometric ultrafine particles are generated. In particular, the nanoparticle presence, size and morphology were investigated and differences between particles produced either in summer or winter seasons were explored. To this aim Atomic Force Microscopy (AFM) and Dynamic Light Scattering (DLS) were employed to analyze nano powders filtered in environments of different paper mills to determine structural morphology and sizes. Large breathable particles, with size in the range from 4 μm to 250 nm have been sampled to evaluate the mean level of exposure. By comparing nanoparticles collected from paper mills in summer and in winter we revealed that the number of nanoparticles collected in winter is strictly related to heat generated by the heating system. [ABSTRACT FROM AUTHOR]

Practical applications require scalable, low cost and facile approaches to fabricate coatings that are repellent to liquids and yet are resistant to mechanical impact and abrasion which may occur during service operation of these materials. Here we report fabrication of superhydrophobic (SHP) coatings on paper substrates by one-step spray-coating of fluorinated silica nanoparticles. The coatings were extremely repellent to water and organic liquids with surface tensions higher than ~ 45 mN/m, as demonstrated by the sliding angles that are lower than 5°. The coated paper substrates retained their liquid repellency behavior without any discernable change in their static contact and sliding angles following different mechanical wear tests. Mechanical robustness together with demonstrations in self-cleaning, anti-icing and food-packaging show great promise for the use of fabricated paper substrates in different applications. A significant finding of the present work is that the mechanical robustness of the spray-coated fluorinated silica nanoparticles in the absence of any polymeric matrix/binder was dramatically higher on paper in comparison to flat substrates. These results suggest that the inherent microstructure of the paper provides a suitable matrix for protecting the functionalized nanoparticles against external mechanical effects and present an effective strategy for improving the mechanical robustness of the coatings fabricated by one-step spray-coating of nanomaterials. [ABSTRACT FROM AUTHOR]

Monodisperse aqueous upconverting nanoparticles (UCNPs) were covalently immobilized on aldehyde modified cellulose paper via reductive amination to evaluate the multiplexing capacity of luminescence resonance energy transfer (LRET) between UCNPs and quantum dots (QDs). This is the first account of a multiplexed bioassay strategy that demonstrates the principle of use of a single form of UCNP as donor and three different color emitting QDs as acceptors to concurrently determine three analytes. Broad absorbance profiles of green, orange and red QDs that spanned from the first exciton absorption peak to the UV region were in overlap with a blue emission band from UCNPs composed of NaYF 4 that was doped with 30% Yb 3+ , 0.5% Tm 3+ , allowing for LRET that was stimulated using 980 nm near-infrared radiation. The characteristic narrow and well-defined emission peaks of UCNPs and QDs allowed for the collection of luminescence from each nanoparticle using a band-pass optical filter and an epi-fluorescence microscope. The LRET system was used for the concurrent detection of uidA, Stx1A and tetA gene fragments with selectivity even in serum samples, and reached limits of detection of 26 fmol, 56 fmol and 76 fmol, respectively. [ABSTRACT FROM AUTHOR]

Clotrimazole is a well-known antimycotic agent, listed in the World Health Organization List of essential medicines, with minimal health side effects acknowledged throughout a long certification period. In this study, clotrimazole in isopropanol was tested as a potential antifungal treatment for paper objects. The antifungal properties of this azole compound were evaluated against five of the most common fungal species affecting paper collections. The addition of a deacidifying agent, calcium hydroxide nanoparticles, resulted in a multipurpose formulation also aimed at neutralizing the deleterious effects of acids excreted by fungi. Clotrimazole showed antifungal activity against all tested fungal species and its effectiveness followed the ascending order: Chaetomium globosum < Cladosporium cladosporioides < Penicillium chrysogenum < Aspergillus niger < Penicillium corylophilum . The best relationship between minimal concentration and fungal inhibition was achieved for 0.05% clotrimazole. The impact of the tested formulation on paper preservation was evaluated in terms of pH, colour and folding endurance, using moist heat artificial ageing. Clotrimazole and calcium hydroxide nanoparticles protected the paper from acidification and loss of folding endurance in the long term, thus representing a non-aqueous alternative treatment for paper affected by fungi. [ABSTRACT FROM AUTHOR]

Fourier transform Raman spectroscopy and (dispersive) confocal Raman microscopy have been applied to quantitatively and qualitatively describe the local distribution of chemical moieties of poly(styrene- co -maleimide) coatings on paper substrates containing different amount of imide. In parallel, local coating defects have been imaged for a better understanding of the influence of the coating composition on homogeneity at macro- to microscale levels. From FT-Raman spectroscopy, the imide content was calculated in quantitative agreement with previous thermoanalytical data. From dispersive spectroscopy, the measuring parameters were optimized for single-point measurements including signals of the coating and macropoint measurements including more intense signals of the paper. The large surface maps (5 × 5 mm 2 ) provided good quantification for the lateral distribution of imide moieties and coverage for coatings with different thickness and imide content, based on relative intensities of imide/styrene and imide/cellulose bands. The inhomogeneities were related to the formation of surface patterns for coatings with high viscosity and presence of non-imidized residues. From detailed surface maps (1 × 1 mm 2 ), sensitive Raman bands were selected to describe variations in imide and styrene concentrations, conformations and interactions with fillers and cellulose. Based on data from Raman analysis, interactions between nanoparticles and cellulose possibly happened through hydrogen bonding. [ABSTRACT FROM AUTHOR]

In parallel with the development of nanoparticle coatings for protection of paper substrates, detailed descriptions of the surface topography with micro- to nanoscale roughness features are needed. In this work, papers have been coated with poly(styrene-co-maleic anhydride) nanoparticles including different types of vegetable oils and the surface roughness was evaluated at 2000 × 2000 μm 2 to 0.2 × 0.2 μm 2 length scales by combining non-contact optical profilometry (NCP) and atomic force microscopy (AFM). The relationships between roughness data were studied for statistical roughness parameters, spatial roughness parameters and in the frequency domain. In order to compare AFM roughness more accurately, the original images were flattened to remove effects of the underlaying fibrous substrate and highlight features of the nanoparticle coating. More detailed information on the coating topography could be obtained by considering bearing ratio curves and histograms, where it was concluded that the oil-filled coatings form a rather thin and continuous coating that closely follows the shape of the cellulose fibers. The relation between statistical roughness parameters from NCP and AFM follows an exponential trend with relatively low coefficient of determination. The increase in surface roughness with length scale showed a transition point attributed to short- and long-range surface features. Therefore, the correlation length was used as a spatial roughness parameter that provides a successful extrapolation of the average roughness over different length scales in a double logarithmic diagram with very high coefficient of determination. Based on the power spectral density, it was difficult to exactly distinguish between the different types of SMI/oil coatings, as they include similar nanoscale features. The frequency roughness parameters were better suited for extrapolation than statistical roughness parameters but little less efficient than the spatial roughness parameters. [ABSTRACT FROM AUTHOR]

A severe decay process, catalyzed by acidity and metal ions, affects cellulose in historical manuscripts and books that contain iron gall inks. The inhibition of this process can be achieved by alkaline-earth nanoparticles dispersions in alcohols, which create a neutral environment in which both oxidation and depolymerization of cellulose are hindered. As a result of the degradation process, paper in historical manuscripts and books is fragile and very difficult to handle. A reinforcement intervention with gelatin and Japanese tissue could be used for the strengthening of historical manuscripts, even if this method could not prevent paper degradation due to iron gall inks. Therefore, a new method, combining a deacidification treatment based on calcium hydroxide nanoparticles and a reinforcement process using Japanese tissue has been developed and tested on mockups containing iron gall inks. The protective action arising from the combined treatment was evaluated by performing cellulose viscosimetric degree of polymerization (DPv) and pH measurements on artificially aged systems. Scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDX) was used for the evaluation of calcium distribution from the deacidification agent within samples cross section. Determinations of DPv clearly showed that the degradation of untreated inked paper was significantly slowed down by the combined treatment. The method was also tested on original manuscripts from 16th and 18th century. SEM-EDX maps showed that the applied treatment, which raised the pH to an appropriate value, is homogenously distributed over the treated surfaces. [ABSTRACT FROM AUTHOR]

Paper, a readily available renewable resource, comprises of interwoven cellulosic fibers, which can be functionalized to develop interesting low-cost adsorbent material for water purification. In this study, polyethyleneimine (PEI)-functionalized paper was used for the removal of hazardous pollutants such as Au and Ag nanoparticles, Cr(VI) anions, Ni 2+ , Cd 2+ , and Cu 2+ cations from spiked water samples. Compared to untreated paper, the PEI-coated paper showed significant improvement in adsorption capacities toward the pollutants investigated in this study. Kinetics, isotherm models, pH, and desorption studies were carried out to study the adsorption mechanism of pollutants on the adsorbent surface. Adsorption of pollutants was better described by pseudo-second order kinetics and Langmuir isotherm model. Maximum adsorption of anionic pollutants was achieved at pH 5 while that of cations was at pH > 6. Overall, the PEI-functionalized paper showed interesting Langmuir adsorption capacities for heavy metal ions such as Cr(VI) (68 mg/g), Ni 2+ (208 mg/g), Cd 2+ (370 mg/g), and Cu 2+ (435 mg/g) ions at neutral pH. In addition, the modified paper was also used to remove Ag-citrate (79 mg/g), Ag-PVP (46 mg/g), Au-citrate (30 mg/g), Au-PVP (17 mg/g) nanoparticles from water. Desorption of NPs from the adsorbent was done by washing with 2 M HCl or thiourea solution, while heavy metal ions were desorbed using 1 M NaOH or HNO 3 solution. The modified paper retained its extraction efficiencies upon desorption of pollutants. [ABSTRACT FROM AUTHOR]

Well-dispersed Fe 3 O 4 nanoparticles (NPs) were synthesized by a co-precipitation method in the presence of cellulose nano-crystals (CNC) as the template. The thus prepared Fe 3 O 4 NPs were then used as a coating agent for the preparation of conductive paper. Fourier transform infrared spectroscopy (FTIR) results revealed that the Fe 3 O 4 NPs were immobilized on the CNC through interactions between the hydroxyl groups of CNC and Fe 3 O 4 . Scanning transmission electron microscopy (STEM) images showed that the Fe 3 O 4 NPs prepared in the presence of CNC can be dispersed in the CNC network, while the Fe 3 O 4 NPs prepared in the absence of CNC tended to aggregate in aqueous solutions. The conductivity of the Fe 3 O 4 NPs coated paper can reach to 0.0269 S/m at the coating amount of 14.75 g/m 2 Fe 3 O 4 /CNC nanocomposites. Therefore, the thus obtained coated paper can be potentially used as anti-static packaging material in the packaging field. [ABSTRACT FROM AUTHOR]

Monodisperse aqueous upconverting nanoparticles (UCNPs) were covalently immobilized on aldehyde modified cellulose paper via reduction amination to develop a luminescence resonance energy transfer (LRET)-based nucleic acid hybridization assay. This first account of covalent immobilization of UCNPs on paper for a bioassay reports an optically responsive method that is sensitive, reproducible and robust. The immobilized UCNPs were decorated with oligonucleotide probes to capture HPRT1 housekeeping gene fragments, which in turn brought reporter conjugated quantum dots (QDs) in close proximity to the UCNPs for LRET. This sandwich assay could detect unlabeled oligonucleotide target, and had a limit of detection of 13 fmol and a dynamic range spanning nearly 3 orders of magnitude. The use of QDs, which are excellent LRET acceptors, demonstrated improved sensitivity, limit of detection, dynamic range and selectivity compared to similar assays that have used molecular fluorophores as acceptors. The selectivity of the assay was attributed to the decoration of the QDs with polyethylene glycol to eliminate non-specific adsorption. The kinetics of hybridization were determined to be diffusion limited and full signal development occurred within 3 min. [ABSTRACT FROM AUTHOR]

Highlights: [•] We prepared a series of paper sheets incorporating titania-anchored hollow silica. [•] The papers showed high photocatalytic activity in the degradation of ethanol. [•] A new model coupling mass transfer and UV penetration has been developed. [•] The simulated UV profiles suggest a strong UV attenuation within the paper thickness. [•] Counter- and co-current modes show comparable photocatalytic activities. [Copyright &y& Elsevier]

Cellulosic nanomaterials are in the focus of academia and industry to realize light-weight biobased materials with remarkable strength. While the effect is well known, the distribution of these nanomaterials are less explored, particularly for paper sheets. Here, we explore the 3D distribution of micro and nanosized cellulosic particles in paper sheets and correlate their extent of fibrillation to the distribution inside the sheets and subsequently to paper properties. To overcome challenges with contrast between the particles and the matrix, we attached probes on the cellulose nano/microparticles, either by covalent attachment of fluorescent dyes or by physical deposition of cobalt ferrite nanoparticles. The increased contrast enabled visualization of the micro and nanosized particles inside the paper matrix using multiphoton microscopy, X-ray microtomography and SEM-EDX. The results indicate that fibrillary fines enrich at pores and fiber-fiber junctions, thereby increasing the relative bonded area between fibers to enhance paper strength while CNF seems to additionally form an inner 3D network. [ABSTRACT FROM AUTHOR]

Solution-phase deposition of nanomaterials represents a highly promising technology with strong industrial application potential for the fabrication of superhydrophobic surfaces. An important barrier towards the adaptation of such materials and processes in a broad range of applications is the limited mechanical durability of the nanostructures. Herein, we present a universal solution to this challenge by benefiting from the unique micro-structure of paper. Our approach is based on transferring the structure of paper into a target material, to form a mechanical protection layer for nanomaterials that were deposited from solution-phase, i.e. spray-coating. We demonstrate this concept through the transfer of the structure of paper to a free-standing PDMS film using a simple molding process. Spraying a dispersion of alkyl-silane functionalized silica nanoparticles on the structured free-standing film results in a hierarchically structured superhydrophobic surface with a water contact angle of 175° ± 2° and a sliding angle <2° ± 1°. The fabricated superhydrophobic surface displays high levels of mechanical, chemical and thermal stability. The robust, inexpensive, scalable, flexible, and environmentally friendly nature of the presented approach may be a key enabler in superhydrophobic coating applications. Unlabelled Image • Transferring the structure of paper as a generalizable strategy for fabrication of robust superhydrophobic surfaces • All-solution processable, inexpensive, scalable, and environmentally friendly fabrication • Inherently flexible coatings adaptable to virtually all types of substrates [ABSTRACT FROM AUTHOR]