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A paper-based microfluidic detection device for the detection of ethanol is demonstrated in this work. The method is based on a fluorophore consisting of short-chain conjugated molecular unit susceptible to the protonation of its terminal pyridine groups, along with a carboxyl-functionalized sidechain that acts as a binder and renders it water-soluble. The resulting fluorescent paper device yields large fluorescence changes when exposed to reactions that yield H2O2 in aqueous solutions. Using an enzyme-catalyzed rection that produces H2O2 from ethanol, we developed a two-zone, cut-out paper device containing a reaction zone in which the ethanol-containing analyte is placed, and an adjacent sensor zone where we observe a fluorescence color shift proportional to the ethanol concentration. The limit of detection of the fluidic ethanol biosensor was 0.05 v/v% and the dynamic range was 0.05-2 v/v%. This method was employed to detect the alcohol concentration of consumer vodkas using only a paper sensor and a smartphone camera. [ABSTRACT FROM AUTHOR]

Cellulose oxidative and hydrolytical degradation is one of the greatest problems for the conservation of paper supports. To contrast these degradation processes, both deacidification and reduction of the oxidized functions are needed. Dealing with original documents, it is often impossible to perform the two mentioned treatments in aqueous solutions and in a distinct subsequent way, because of the fragility of the artifacts. After studying, in a separate way, an effective deacidifier (calcium propionate) soluble in ethyl alcohol and many reducers (boron complexes), able to act in different non-aqueous solvents, it was decided to test a simultaneous method of deacidification and reduction in ethanol. This paper presents the chemical-physical results obtained by applying simple deacidification and simultaneous deacidification-reduction on laboratory paper samples that were artificially aged and then re-measured after 10 and 15 years of natural aging. Results show that all alcoholic treatments are very effective: papers are stable also after a long period of both artificial and natural aging. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO)/cellulose paper was prepared by adding aqueous dispersion of GO into cellulose fiber pulp in a traditional papermaking procedure. Cationic polyacrylamide (CPAM) was added as a mordant to induce the self-assembly of GO layers on the fiber surfaces. The surface morphology, mechanical properties and gas permeability of GO/cellulose paper with varying GO contents were investigated by scanning electron microscopy (SEM), tensile test, burst test, tear test and densometer. It was found that CPAM could prevent the self-aggregation of GO in fiber matrix and increase the loading efficiency of GO to up to 16 wt% without sacrificing the mechanical performances of the paper. This finding permitted the large scale preparation of GO/cellulose paper with high doping amount of GO, which exhibited dense and compact geometry and low gas permeability ideal for potential packaging applications. [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]

In this study we investigated the underlying mechanisms of coffee stain formation on paper – a porous substrate. When a drop of aqueous liquid containing dispersed materials dries on paper, the faster water evaporation rate at the edge of the drop drives the redistribution of the dispersed materials to the edge of the drop-covered area on paper. Deegan׳s discovery has been accepted as the “coffee ring” phenomenon, which has wide implications. However, stains left by dried aqueous liquids on paper are not always ring-shaped. This is because, besides Deegan׳s coffee ring effect, the transport of dispersed materials in porous media is affected by chromatographic and filtration effects, which are highly dependent upon the properties of the substrates. In this work we clarify the influences of different mechanisms to the dispersed materials redistribution in paper. [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]

The paper is on introducing carbamate groups in sheets of cellulose fiber assemblies by pad-dry-cure treatments with aqueous solutions of polyethylene glycol, amide and salt. The effects of process variables-on carbamation levels and on mechanical properties of the substrate-are reported. Depending on treatment conditions, the nitrogen contents in substrates are in the range 0.668-2.252 wt%, corresponding to nominal degrees of carbamate group substitution of 0.08-0.28. The carbamation is initiated at 140 °C curing, and the levels rise with temperature up to 220 °C, but decrease at higher temperatures. The duration of curing also exerts an influence. There is a catalytic effect of sodium acetate on the carbamation, but the salt also induces a brown coloration in samples, which is likely a result of Maillard-type reactions. The treatments cause hydrolytic degradation in substrates, but there are options to adjust treatment conditions and minimize damage. Pad-dry-cure treatments are a common operation in the textile and paper industries, and the process may be adopted in commercial-scale operations to create derivatized paper or fabrics (woven, knitted or non-woven) for utilization in applications such as adsorbents for heavy metals from waste water, in hygiene products, in the creation of flame retardant products, or in creating all-cellulose composites by further treatment with alkali. [ABSTRACT FROM AUTHOR]

Abstract: In certain conditions, iron gall inks induce substantial damages on cellulosic supports. Existing curative treatments necessitate the immersion of the documents in aqueous solutions. This implies several undesirable side effects: mechanical stress of the most damaged papers, substantial colour changes, and a drastic modification of the paper/ink composition. This work investigated an alternative treatment that consists in compressing the document between two interleaves that are charged with active compounds. When this operation is operated in moist conditions, active compounds may migrate from the interleaves to the document, and thus achieve the treatment of the paper. As high humidity conditions may additionally induce some migration of iron and acidic compounds out of the ink line, it first appeared necessary to research humidity conditions which minimize these undesirable migrations. This investigation was performed on a set of 53 original manuscripts and led us to consider that a relative humidity of 80% was quite reasonable. The second part of the paper deals with the evaluation of interleaving treatment efficiency. It was performed on laboratory samples, using several types of antioxidant halide salts (NaCl, NaBr, CaBr2) (halides are known to act as radical scavengers). These compounds were tested separately or in combination with calcium carbonate as an alkaline buffer. The samples were made of Whatman paper that was preliminary impregnated with iron gall ink. It has shown that a charge of 2% calcium carbonate in the interleaves has no impact on the treatment efficiency, which mainly depends upon the concentration of salts, the contact pressure and the duration of the treatment. Elemental measurements show that the mobility of the salts is much higher than that of iron, suggesting the possibility to find optimum treatment conditions that minimize the iron migration risk while achieving an effective migration of halides. [Copyright &y& Elsevier]

Abstract: This study examines and quantifies the effect of cationic polyelectrolyte adsorption on paper on the aggregation and retention of gold nanoparticles (AuNPs) to optimize their Surface Enhanced Raman Scattering (SERS) enhancement factor and sensitivity. Aggregation of metallic nanoparticles is known as a key factor for intense SERS enhancement. Paper substrates were treated with aqueous solutions of cationic polyacrylamide (CPAM) varying in concentration, charge density, and molecular weight to control the AuNPs’ aggregate size distribution and surface coverage on paper. The Raman Enhancement Factor of AuNPs-CPAM paper was almost an order of magnitude greater than for the untreated AuNPs paper. The high loading and uniform distribution of AuNPs aggregates on CPAM pre-treated paper contributed toward the excellent SERS reproducibility, sensitivity, and high enhancement factor. This configuration of AuNP on paper was favoured by treating the substrate with CPAM solutions of higher concentrations, higher charge density, and greater molecular weight. [Copyright &y& Elsevier]