Multifunctional Textiles from New Zealand Wool Coloured with Silver or Silver Halide Nanoparticles

<p>Significant opportunities exist for the development of innovative multifunctional textiles for high value market applications. Composites that combine the inherent properties of their all precursor components in a synergistic manner in particular are sought after. Thus the unique chemical and physical properties of silver or silver halide nanoparticles are combined with the traditional properties of wool, thereby producing an innovative multifunctional composite. The prepared wool - silver or - silver halide nanoparticle composites retain the elasticity, thermal insulation and softness of the wool, whilst the colour, conductivity and antimicrobial properties owing to the nanoparticles are also incorporated. Due to the multi functions of silver the resulting high quality, high value product has numerous applications within the fashion and interior furnishings industries. The wools employed for the preparation of wool - silver or - silver chloride nanoparticle composites are merino wool and crossbred wool. Merino wool provides the main focus of the research. The experimental approach for the colouring of merino by silver or silver halide nanoparticles follows a novel and proprietary approach. The preparation of wool - silver nanoparticle composites includes two different procedures: 1) the synthesis of nanoparticles in the presence of wool fibres, using an external reducing agent/stabilising agent (trisodium citrate (TSC)), with the in situ binding of nanoparticles to the surface of the fibre; and 2) the synthesis of nanoparticles in the presence of the merino wool substrate, using the reducing nature of wool, with the in situ binding of nanoparticles within the fibre. Merino wool - silver nanoparticle composites range in colour from very pale yellow, through gold to tan and brown. The successful preparation of wool - silver halide nanoparticle composites includes the in situ precipitation of nanoparticles within the wool fibre. This is accomplished by doping the wool, with one of the halides, Cl⁻, Br⁻ or I⁻, prior to treatment with a silver containing solution. The colour of merino wool - silver halide nanoparticle composites can be tuned from pink to peach to purple. The colour of the wool - silver or - silver halide nanoparticle composites is due to surface plasmon resonances, i.e. the interaction of electromagnetic radiation of visible light with the nanoparticles. The reflected colour is dependent upon the size and shape of the nanoparticle, in addition to the refractive index of the stabilising agent surround the particle. The refractive index of silver chloride or silver bromide differs to that of the reducing/stabilising agent implemented, TSC, or merino, and thus the reflected colour is altered. The colour of silver iodide nanoparticles appears to be due to the interaction of light with the formed nanoparticles themselves and not due to the formation of silver nanoparticles within the silver iodide nanoparticles. In addition to the colour being measured by UV-vis in reflectance mode, the characterisation of the hues of the prepared composites were monitored by obtaining CIE L*, a*, b* values via the HunterLab Colourquest. The morphological characterisation of merino wool coloured by silver or silver chloride nanoparticles was undertaken using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). When merino wool - silver nanoparticle composites are prepared using an external reducing agent, the formed nanoparticles predominantly bind to the wool fibres surfaces only. When the reducing nature of wool is used for composite preparation, nanoparticles are formed within the fibre and are dispersed throughout the fibres core, with few being present on the surface. Comparable studies of merino wool - silver halide nanoparticle composites showed that silver halide nanoparticles are formed and stabilised just below the fibres surface. The confirmation of silver or silver halide species within the prepared composites was undertaken using energy dispersive spectroscopy (EDS), scanning transmission spectroscopy (STEM), x-ray diffraction (XRD) and x-ray absorption near edge spectroscopy (XANES). Colourfastness tests to washing, rubbing and exposure to chlorinated swimming pool water were undertaken to assess the robustness of the prepared composites in terms of their colour. These tests indicate that the colours of both merino wool - silver and - silver chloride nanoparticle composites are very stable. The leaching of silver during the washing process was noted to be insignificant, suggesting a strong and stable bond between the fibre substrate and the nanoparticles. X-ray photoelectron spectroscopy (XPS) was used to elucidate the chemical bonding between the wool fibre substrate and the silver or silver halide nanoparticles. The colourfastness of merino wool - silver or - silver halide nanoparticle composites to light however, was not observed. When exposed to UV light for extended periods, a distinct change in colour occurs. Silver nanoparticle composites lighten considerably, whereas their silver chloride nanoparticle counterparts are noted to become grey in their colour. XPS was used in an attempt to determine what leads to the discolouration of the composites. Further research is required however, in order to reduce or halt the colour degradation of merino wool - silver or - silver chloride nanoparticle composites. Silver iodide nanoparticles, on the other hand, show great potential as colourants for wool, exhibiting stable colours over a long time period to light. A range of desirable colours are obtained through the colouring of wool by silver or silver halide nanoparticles. These nanoparticles are strongly bound to the fibres and thus the colours are stable to washing and rubbing, exhibiting insignificant leaching of silver during such processes. Additionally, the prepared silver and silver halide nanoparticle composites tested positive for their antistatic properties, and their antimicrobial activity, providing a high value multifunctional material. Numerous applications within fashion and interior furnishing industries are therefore apparent. However, the evident setback for applications in these fields is the colour instability to light of silver, silver chloride and silver bromide nanoparticles, and thus further studies are required to eliminate this problem. Alternative options exist for the exploitation of the photosensitivity of silver halide nanoparticles within the merino wool composites, or the possibility of using silver or silver halide nanoparticles in combination with other strong dyes for the production of coloured woollen fabrics.</p>

Multifunctional Textiles from New Zealand Wool Coloured with Silver or Silver Halide Nanoparticles

<p>Significant opportunities exist for the development of innovative multifunctional textiles for high value market applications. Composites that combine the inherent properties of their all precursor components in a synergistic manner in particular are sought after. Thus the unique chemical and physical properties of silver or silver halide nanoparticles are combined with the traditional properties of wool, thereby producing an innovative multifunctional composite. The prepared wool - silver or - silver halide nanoparticle composites retain the elasticity, thermal insulation and softness of the wool, whilst the colour, conductivity and antimicrobial properties owing to the nanoparticles are also incorporated. Due to the multi functions of silver the resulting high quality, high value product has numerous applications within the fashion and interior furnishings industries. The wools employed for the preparation of wool - silver or - silver chloride nanoparticle composites are merino wool and crossbred wool. Merino wool provides the main focus of the research. The experimental approach for the colouring of merino by silver or silver halide nanoparticles follows a novel and proprietary approach. The preparation of wool - silver nanoparticle composites includes two different procedures: 1) the synthesis of nanoparticles in the presence of wool fibres, using an external reducing agent/stabilising agent (trisodium citrate (TSC)), with the in situ binding of nanoparticles to the surface of the fibre; and 2) the synthesis of nanoparticles in the presence of the merino wool substrate, using the reducing nature of wool, with the in situ binding of nanoparticles within the fibre. Merino wool - silver nanoparticle composites range in colour from very pale yellow, through gold to tan and brown. The successful preparation of wool - silver halide nanoparticle composites includes the in situ precipitation of nanoparticles within the wool fibre. This is accomplished by doping the wool, with one of the halides, Cl⁻, Br⁻ or I⁻, prior to treatment with a silver containing solution. The colour of merino wool - silver halide nanoparticle composites can be tuned from pink to peach to purple. The colour of the wool - silver or - silver halide nanoparticle composites is due to surface plasmon resonances, i.e. the interaction of electromagnetic radiation of visible light with the nanoparticles. The reflected colour is dependent upon the size and shape of the nanoparticle, in addition to the refractive index of the stabilising agent surround the particle. The refractive index of silver chloride or silver bromide differs to that of the reducing/stabilising agent implemented, TSC, or merino, and thus the reflected colour is altered. The colour of silver iodide nanoparticles appears to be due to the interaction of light with the formed nanoparticles themselves and not due to the formation of silver nanoparticles within the silver iodide nanoparticles. In addition to the colour being measured by UV-vis in reflectance mode, the characterisation of the hues of the prepared composites were monitored by obtaining CIE L*, a*, b* values via the HunterLab Colourquest. The morphological characterisation of merino wool coloured by silver or silver chloride nanoparticles was undertaken using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). When merino wool - silver nanoparticle composites are prepared using an external reducing agent, the formed nanoparticles predominantly bind to the wool fibres surfaces only. When the reducing nature of wool is used for composite preparation, nanoparticles are formed within the fibre and are dispersed throughout the fibres core, with few being present on the surface. Comparable studies of merino wool - silver halide nanoparticle composites showed that silver halide nanoparticles are formed and stabilised just below the fibres surface. The confirmation of silver or silver halide species within the prepared composites was undertaken using energy dispersive spectroscopy (EDS), scanning transmission spectroscopy (STEM), x-ray diffraction (XRD) and x-ray absorption near edge spectroscopy (XANES). Colourfastness tests to washing, rubbing and exposure to chlorinated swimming pool water were undertaken to assess the robustness of the prepared composites in terms of their colour. These tests indicate that the colours of both merino wool - silver and - silver chloride nanoparticle composites are very stable. The leaching of silver during the washing process was noted to be insignificant, suggesting a strong and stable bond between the fibre substrate and the nanoparticles. X-ray photoelectron spectroscopy (XPS) was used to elucidate the chemical bonding between the wool fibre substrate and the silver or silver halide nanoparticles. The colourfastness of merino wool - silver or - silver halide nanoparticle composites to light however, was not observed. When exposed to UV light for extended periods, a distinct change in colour occurs. Silver nanoparticle composites lighten considerably, whereas their silver chloride nanoparticle counterparts are noted to become grey in their colour. XPS was used in an attempt to determine what leads to the discolouration of the composites. Further research is required however, in order to reduce or halt the colour degradation of merino wool - silver or - silver chloride nanoparticle composites. Silver iodide nanoparticles, on the other hand, show great potential as colourants for wool, exhibiting stable colours over a long time period to light. A range of desirable colours are obtained through the colouring of wool by silver or silver halide nanoparticles. These nanoparticles are strongly bound to the fibres and thus the colours are stable to washing and rubbing, exhibiting insignificant leaching of silver during such processes. Additionally, the prepared silver and silver halide nanoparticle composites tested positive for their antistatic properties, and their antimicrobial activity, providing a high value multifunctional material. Numerous applications within fashion and interior furnishing industries are therefore apparent. However, the evident setback for applications in these fields is the colour instability to light of silver, silver chloride and silver bromide nanoparticles, and thus further studies are required to eliminate this problem. Alternative options exist for the exploitation of the photosensitivity of silver halide nanoparticles within the merino wool composites, or the possibility of using silver or silver halide nanoparticles in combination with other strong dyes for the production of coloured woollen fabrics.</p>

Nanogold and nanosilver hybrid polymer materials

<p>Significant opportunities exist in both the scientific and industrial sectors for the development of new generation hybrid materials. These multifunctional hybrid materials favourably combine the often disparate characteristics of both precursor components in one material. As such, this field can be very innovative due to the many possible combinations of components providing the opportunity to create a wide variety of new generation materials with a range of known and as yet unknown properties. In this manner the research carried out in this PhD research programme combines particular polymer substrates with gold, silver or silver halide nanoparticles, generating multifunctional hybrid materials which exhibit novel and useful optical, antimicrobial and antifouling properties. As such, these hybrid materials are well suited for applications in the healthcare and biomedical devices, food and packaging, surface coatings and the personal hygiene industries. The novel approach developed and used for the production of these nanogold, nanosilver and nanosilver halide hybrid polymer materials did not use conventional external reducing or stabilising agents. Instead, for the nanogold and nanosilver hybrid polymer materials, the Au3+ or Ag+ ions were first absorbed into the polymer substrates (polyurethane, nylon 6,6, polyurethane K5000 latex paint base and amine coated polyethylene terephthalate) and then upon heating the nitrogen-containing functional groups in the polymer matrices reduced the metal ions to their respective metal nanoparticles Au0 and Ag0. Simultaneously a chemical interaction between the metal nanoparticles and the polymer matrix was facilitated. Hence the reduction reaction was effected by the coupled to the oxidation reaction of the nitrogen-containing functional groups. The polymer matrix also afforded control over the nanoparticle size. Silica based BULK ISOLUTE® SORBENTS were used to help elucidate this particular chemistry taking place in the formation of the hybrid polymer materials. The synthesis of the nanosilver halide hybrid polymer materials involved the initial absorption of halide ions into the polymer matrix followed by treatment with silver ions to effect precipitation of nanosize silver halide particles within the polymer matrix, wherein the particle size was similarly controlled by the polymer matrix and precipitation conditions. All formed nanoparticles were therefore stabilised by the polymer matrix. The colour of the resultant hybrid polymer materials is due to the surface plasmon resonance effect of gold and silver nanoparticles. The colour is dependent on the particle size and shape of the nanoparticles and on the refractive index of the surrounding medium. Nanogold hybrid polymers are pink/purple in colour whereas nanosilver hybrid polymers reflect yellow/brown colour. Nanosilver halide hybrid polymers absorb light in the UV range of light and are therefore white in colour. However, due to their photosensitive properties, once exposed to light, silver halides undergo a self-photosensitisation process resulting in formation of silver nanodomains (smaller nanoparticles) on the surface of the silver halide nanoparticles. This gives rise to their absorption in the visible range of light making the hybrid polymer materials appear purple/brown in colour. Nanosilver iodide hybrid polymer materials do not show this effect to any extent and remain as their typical yellow colour. The reflected colours of the hybrid polymer materials and therefore the particle sizes and shapes of metal nanoparticles were investigated by the UV-Vis spectroscopy. The electron microscopy (SEM and TEM) studies showed the morphology of the hybrid polymer materials and that the nanoparticles were not only deposited on the surface but distributed within the polymer matrix. The metal nanoparticles varied in sizes and shapes, particle agglomerates were observed. The confirmation of gold, silver or silver halide species was undertaken using energy dispersive spectroscopy (EDS), scanning transmission spectroscopy (STEM) and X-ray diffraction (XRD). Furthermore, X-ray photoelectron spectroscopy (XPS) was carried out in order to study the nature of the interaction between the formed metal nanoparticles and the polymer matrix. It was demonstrated that the gold and silver nanoparticles are bound to the polymer matrices via Au-N and Ag-N bonds respectively, through the nitrogen-containing functional groups of the polymer matrices. The presence of the oxidised nitrogen species (NOx) confirmed that the electrons required for the reduction of Au3+ and Ag+ to the respective nanoparticles were provided by the coupled oxidation reaction of the nitrogen-containing groups in the polymer matrices. The XPS studies showed there is an interaction between the silver on the surface of the AgX nanoparticles and the nitrogen and oxygen groups present in the polymer matrix. The observation that only very small amounts of Au3+ and Ag+ ions could be leached from the nanogold and nanosilver hybrid materials confirmed the integrity of this chemical bonding between the gold or silver nanoparticles and the polymer matrix. The nanogold, nanosilver and nanosilver halide polymer materials showed effective antimicrobial properties. They were successfully tested against gram negative bacteria Escherichia coli. Additionally, the new generation nanogold and nanosilver hybrid polymer materials have been shown to exhibit antifouling properties.</p>

Nanogold and nanosilver hybrid polymer materials

<p>Significant opportunities exist in both the scientific and industrial sectors for the development of new generation hybrid materials. These multifunctional hybrid materials favourably combine the often disparate characteristics of both precursor components in one material. As such, this field can be very innovative due to the many possible combinations of components providing the opportunity to create a wide variety of new generation materials with a range of known and as yet unknown properties. In this manner the research carried out in this PhD research programme combines particular polymer substrates with gold, silver or silver halide nanoparticles, generating multifunctional hybrid materials which exhibit novel and useful optical, antimicrobial and antifouling properties. As such, these hybrid materials are well suited for applications in the healthcare and biomedical devices, food and packaging, surface coatings and the personal hygiene industries. The novel approach developed and used for the production of these nanogold, nanosilver and nanosilver halide hybrid polymer materials did not use conventional external reducing or stabilising agents. Instead, for the nanogold and nanosilver hybrid polymer materials, the Au3+ or Ag+ ions were first absorbed into the polymer substrates (polyurethane, nylon 6,6, polyurethane K5000 latex paint base and amine coated polyethylene terephthalate) and then upon heating the nitrogen-containing functional groups in the polymer matrices reduced the metal ions to their respective metal nanoparticles Au0 and Ag0. Simultaneously a chemical interaction between the metal nanoparticles and the polymer matrix was facilitated. Hence the reduction reaction was effected by the coupled to the oxidation reaction of the nitrogen-containing functional groups. The polymer matrix also afforded control over the nanoparticle size. Silica based BULK ISOLUTE® SORBENTS were used to help elucidate this particular chemistry taking place in the formation of the hybrid polymer materials. The synthesis of the nanosilver halide hybrid polymer materials involved the initial absorption of halide ions into the polymer matrix followed by treatment with silver ions to effect precipitation of nanosize silver halide particles within the polymer matrix, wherein the particle size was similarly controlled by the polymer matrix and precipitation conditions. All formed nanoparticles were therefore stabilised by the polymer matrix. The colour of the resultant hybrid polymer materials is due to the surface plasmon resonance effect of gold and silver nanoparticles. The colour is dependent on the particle size and shape of the nanoparticles and on the refractive index of the surrounding medium. Nanogold hybrid polymers are pink/purple in colour whereas nanosilver hybrid polymers reflect yellow/brown colour. Nanosilver halide hybrid polymers absorb light in the UV range of light and are therefore white in colour. However, due to their photosensitive properties, once exposed to light, silver halides undergo a self-photosensitisation process resulting in formation of silver nanodomains (smaller nanoparticles) on the surface of the silver halide nanoparticles. This gives rise to their absorption in the visible range of light making the hybrid polymer materials appear purple/brown in colour. Nanosilver iodide hybrid polymer materials do not show this effect to any extent and remain as their typical yellow colour. The reflected colours of the hybrid polymer materials and therefore the particle sizes and shapes of metal nanoparticles were investigated by the UV-Vis spectroscopy. The electron microscopy (SEM and TEM) studies showed the morphology of the hybrid polymer materials and that the nanoparticles were not only deposited on the surface but distributed within the polymer matrix. The metal nanoparticles varied in sizes and shapes, particle agglomerates were observed. The confirmation of gold, silver or silver halide species was undertaken using energy dispersive spectroscopy (EDS), scanning transmission spectroscopy (STEM) and X-ray diffraction (XRD). Furthermore, X-ray photoelectron spectroscopy (XPS) was carried out in order to study the nature of the interaction between the formed metal nanoparticles and the polymer matrix. It was demonstrated that the gold and silver nanoparticles are bound to the polymer matrices via Au-N and Ag-N bonds respectively, through the nitrogen-containing functional groups of the polymer matrices. The presence of the oxidised nitrogen species (NOx) confirmed that the electrons required for the reduction of Au3+ and Ag+ to the respective nanoparticles were provided by the coupled oxidation reaction of the nitrogen-containing groups in the polymer matrices. The XPS studies showed there is an interaction between the silver on the surface of the AgX nanoparticles and the nitrogen and oxygen groups present in the polymer matrix. The observation that only very small amounts of Au3+ and Ag+ ions could be leached from the nanogold and nanosilver hybrid materials confirmed the integrity of this chemical bonding between the gold or silver nanoparticles and the polymer matrix. The nanogold, nanosilver and nanosilver halide polymer materials showed effective antimicrobial properties. They were successfully tested against gram negative bacteria Escherichia coli. Additionally, the new generation nanogold and nanosilver hybrid polymer materials have been shown to exhibit antifouling properties.</p>

Synthesis and Characterisation of Photocatalyst Silver/Silver Halide Nanocomposites

<p>The photochemical activity of silver halides forms the basis of photography and latent image formation. More recently it has been used to create hybrid silver/silver halide nanoparticles. These are formed through partial reduction of Ag⁺ to Ag⁰ by a photochemical self-sensitisation when irradiated with light. This gives the silver/silver halide nanoparticles interesting photocatalytic properties. As such, these silver/silver halide nanoparticles have seen to be part of group of photocatalysts known as plasmonic photocatalysts. Where, the photocatalytic mechanism is enhanced by the surface plasmon resonance of noble metal nanodomains on the surface of the silver halide nanoparticle. The silver/silver halide nanoparticles of Cl⁻, Br⁻ and I⁻ were synthesised and characterised. Silver/silver halide nanoparticles were then incorporated into porous support materials creating silver/silver halide nanocomposite materials. This was through a straight forward aqueous synthesis method, where silver halide nanoparticles precipitated from solution, and nanoparticle size, shape and stabilisation was controlled by the porous support material. Silver/silver halide nanocomposite samples using Cl⁻, Br⁻ and I⁻ were synthesised using wool fibres, kraft paper fibres and nanostructured calcium silicate as supports. UV/Vis and XRD showed Ag⁰ nanodomains were formed during the self-sensitisation process. SEM showed the morphology of the nanocomposites and that the nanoparticles were distributed within the nanocomposite matrix, not deposited on the surface. Preliminary photocatalytic activity of Ag/AgCl nanoparticles and nanocomposites was evaluated through the degradation of methylene blue when irradiated with light. All samples showed increased photocatalytic activity with the Ag/AgCl nanoparticles.</p>

Synthesis and Characterisation of Photocatalyst Silver/Silver Halide Nanocomposites

<p>The photochemical activity of silver halides forms the basis of photography and latent image formation. More recently it has been used to create hybrid silver/silver halide nanoparticles. These are formed through partial reduction of Ag⁺ to Ag⁰ by a photochemical self-sensitisation when irradiated with light. This gives the silver/silver halide nanoparticles interesting photocatalytic properties. As such, these silver/silver halide nanoparticles have seen to be part of group of photocatalysts known as plasmonic photocatalysts. Where, the photocatalytic mechanism is enhanced by the surface plasmon resonance of noble metal nanodomains on the surface of the silver halide nanoparticle. The silver/silver halide nanoparticles of Cl⁻, Br⁻ and I⁻ were synthesised and characterised. Silver/silver halide nanoparticles were then incorporated into porous support materials creating silver/silver halide nanocomposite materials. This was through a straight forward aqueous synthesis method, where silver halide nanoparticles precipitated from solution, and nanoparticle size, shape and stabilisation was controlled by the porous support material. Silver/silver halide nanocomposite samples using Cl⁻, Br⁻ and I⁻ were synthesised using wool fibres, kraft paper fibres and nanostructured calcium silicate as supports. UV/Vis and XRD showed Ag⁰ nanodomains were formed during the self-sensitisation process. SEM showed the morphology of the nanocomposites and that the nanoparticles were distributed within the nanocomposite matrix, not deposited on the surface. Preliminary photocatalytic activity of Ag/AgCl nanoparticles and nanocomposites was evaluated through the degradation of methylene blue when irradiated with light. All samples showed increased photocatalytic activity with the Ag/AgCl nanoparticles.</p>

Creating nanoscale luminescence centres in silver halides suitable for infrared application

This study shows the possibility of creating luminescence centres in silver halide media using substances based on rare-earth elements such as neodymium, ytterbium and dysprosium. These luminescent substances in the form of fine particles of both nanoscale and microscale dimensions can be introduced into the AgCl0.25Br0.75 ceramic matrix highly transparent in the spectral range of 0.5–35 μm. Our theoretical and experimental studies showed that the introduction of luminescent nanoparticles or microparticles at the amount of 0.5 wt.% into AgCl0.25Br0.75 ceramics neither reduces the level of its transmission in the MIR region nor shortens the range of transmission. What is more, we proved that the luminescent properties of nanoparticles remain well preserved after doping silver halide ceramic media with them. Therefore, silver halides doped with rare-earth elements in question can be used for developing the sources of coherent middle infrared radiation, with appropriate energy levels being excited by optical radiation or pulsed electric field.

Thermal conductivity measurement of infrared optical fibers based on silver halide solid solution crystals

The aim of the study is to measure the thermal conductivity of silver halide light guides based on crystals of the AgCl-AgBr system used in PSD production technologies. The conductivity temperature coefficient of the samples under study were determined by the laser flash method using the LFA 467 (Hyper Flash) installation. We studied mono- and polycrystalline samples of solid solutions with the composition AgCl0,25AgBr0,75 in the temperature range 298–523 K. The thermal conductivity of the investigated materials was then calculated using literature data on density and heat capacity. The thermal conductivity coefficient ranges from 0.80±0,04 to 0.53±0,03 (W/mK), depending on the microstructure of the sample.

Paper-Based Device for Sweat Chloride Testing Based on the Photochemical Response of Silver Halide Nanocrystals

A new method for the determination of chloride anions in sweat is described. The novelty of the method relies on the different photochemical response of silver ions and silver chloride crystals when exposed to UV light. Silver ions undergo an intense colorimetric transition from colorless to dark grey-brown due to the formation of nanosized Ag while AgCl exhibits a less intense color change from white to slightly grey. The analytical signal is obtained as mean grey value of color intensity on the paper surface and is expressed as the absolute difference between the signal of the blank (i.e., in absence of chloride) and the sample (i.e., in the presence of chloride). The method is simple to perform (addition of sample, incubation in the absence of light, irradiation, and offline measurement in a flatbed scanner), does not require any special signal processing steps (the color intensity is directly measured from a constant window on the paper surface without any imager processing) and is performed with minimum sample volume (2 μL). The method operates within a large chloride concentration range (10–140 mM) with good detection limits (2.7 mM chloride), satisfactory recoveries (95.2–108.7%), and reproducibility (<9%). Based on these data the method could serve as a potential tool for the diagnosis of cystic fibrosis through the determination of chloride in human sweat.