Direct identification of dyes in textiles by direct analysis in real time-time of flight mass spectrometry

We present here a method requiring no sample preparation for direct identification of the organic dye compounds quercetin, indigotin, and alizarin in reference materials, in solution, and also in situ in dyed fibers by use of direct analysis in real time (DART) ionization and high-resolution time-of-flight mass spectrometry. Exact mass determinations on small samples of dyed textiles were completed in less than 1 min. With the ability to identify flavonoid, indigoid, and anthraquinone classes of dyes, this technique shows early promise as an additional analytical tool in the challenging analysis of organic dyes in rare cultural heritage materials and possesses the unique advantages of sensitivity and simplicity without the preparatory procedures required by other methods.     

染料与纤维共磨对纸浆模塑染色和强度性能的影响

目的探究深色纸浆模塑制品染色过程中出现色差的机理,研究染料与纤维共磨对染色效果和强度性能的影响,提出改善深色纸浆模塑制品染色效果与强度性能的工艺。方法在相同磨浆转数下,探究染料的加入方式对纤维形态、染色制品强度、光学性能及染料上染率的影响;将染料与纤维共磨,探究不同磨浆转数对浆料的滤水性能、染色制品的染色效果和强度的影响。结果实验证实,染料和纤维共磨有利于改善染色制品的抗张强度和耐破强度,能在显著提高染色效果的同时有效降低染色制品的正反面色差。与传统添加方式相比,染色制品的色差由2.53缩小到0.20,上染率从72.02%提高到了77.93%。显微镜图像分析显示,共磨浆料的纤维起毛现象更明显。此外,随着磨浆转数增加,染色制品的光学性能和强度性能得到提高。结论染料与纤维共磨可以提高打浆效果,改善深色纸浆模塑制品的染色效果和强度性能。     

Development of mild extraction methods for the analysis of natural dyes in textiles of historical interest using LC-diode array detector-MS

Analysis of dyes extracted from textiles of historical interest can give valuable information as to where, when, and how the textiles were made. The most widely used method for extraction of colorants involves heating with HCl, which frequently decomposes glycosidic dye components to their parent aglycons, with consequent loss of information about the source of the dye. This is particularly true for flavonoid dyes, many of which are glycosides. We have developed or improved upon two mild textile extraction methods that use ethylenediaminetetraacetic acid (EDTA) and formic acid and are efficient in extracting dyes, but preserve glycosidic linkages. The relative efficiencies of the HCl, EDTA, and formic acid extraction methods are compared by analyzing extracts of dyed samples of silk using HPLC coupled with diode array and mass spectrometric detection. HPLC profiles of EDTA or formic acid extracts of silk dyed, for example, with pagoda tree buds and onionskins are clearly distinguishable as to the plant material used, whereas profiles of HCl extracts are not. Thus, extraction of textiles with EDTA or formic acid reagents can yield significantly more information about the original dyestuff than can extraction with a strong acid.     

Trace-fiber color discrimination by electrospray ionization mass spectrometry: a tool for the analysis of dyes extracted from submillimeter nylon fibers

The application of electrospray ionization mass spectrometry (ESI-MS) to trace-fiber color analysis is explored using acidic dyes commonly employed to color nylon-based fibers, as well as extracts from dyed nylon fibers. Qualitative information about constituent dyes and quantitative information about the relative amounts of those dyes present on a single fiber become readily available using this technique. Sample requirements for establishing the color identity of different samples (i.e., comparative trace-fiber analysis) are shown to be submillimeter. Absolute verification of dye mixture identity (beyond the comparison of molecular weights derived from ESI-MS) can be obtained by expanding the technique to include tandem mass spectrometry (ESI-MS/MS). For dyes of unknown origin, the ESI-MS/MS analyses may offer insights into the chemical structure of the compound-information not available from chromatographic techniques alone. This research demonstrates that ESI-MS is viable as a sensitive technique for distinguishing dye constituents extracted from a minute amount of trace-fiber evidence. A protocol is suggested to establish/refute the proposition that two fibers--one of which is available in minute quantity only--are of the same origin.     

Identification of natural dyes on laboratory-dyed wool and ancient wool, silk, and cotton fibers using attenuated total reflection (ATR) Fourier transform infrared (FT-IR) spectroscopy and Fourier transform Raman spectroscopy

Attenuated total reflection (ATR) infrared and Fourier transform (FT) Raman spectra were obtained from wool threads dyed in the laboratory with natural dyes used in antiquity, following a procedure similar to ancient methods for dyeing wool. The ATR spectra were primarily dominated by the signals of the wool, making it difficult to identify the dye on the fibers only by visual inspection of the infrared spectrum. However, the Raman spectra showed more significant characteristics attributable to the dyes as previously studied in the literature on modern synthetic dyes. A library-search method was thus applied to the second derivatives of both the ATR and Raman spectra to verify the possibility of identifying the dye. Two libraries were constructed, one consisting of the ATR spectra of undyed wool (raw, washed, and mordanted) and the transmission spectra of pure dyes and the other consisting of the Raman spectra of undyed wool and of pure dyes. Correlation and first-derivative correlation search algorithms were used. The results presented here suggest that the two types of spectroscopy are complementary in this kind of work, allowing the almost complete identification of historic dyes on wool. In fact, through the combined use of the two searches, most dyes were identified with a good index of similarity and within the first five hits. Only for annatto was identification totally impossible using either technique. Subsequently the same method was applied to wool, silk, and cotton threads taken from ancient Caucasian and Chinese textiles.     

Pretreatment Strategies for SERS Analysis of Indigo and Prussian Blue in Aged Painted Surfaces

Surface-enhanced Raman scattering (SERS) spectroscopy is increasingly applied to the identification of organic colorants in cultural heritage objects because vibrational fingerprints can be measured from microscopic samples. However, the development of SERS into a reliable, broad-spectrum method for art analysis requires the study of a wide variety of organic and inorganic colorants as well as colorant mixtures in paint. Here, we demonstrate reliable protocols for SERS-based identification of insoluble indigo, Prussian blue (PB), and mixtures thereof in aged painted surfaces. The use of simple salts and acids for sample pretreatment is evaluated. High-quality SERS spectra of PB and indigo are elucidated upon sample pretreatment with H(2)SO(4). In several cases, SERS spectra of the colorants could not be obtained without sample pretreatment. We demonstrate the use of H(2)SO(4) to solubilize PB as well as perform an in situ conversion of insoluble indigo to soluble indigo carmine (IC) on indigo, indigo oil paint, and actual samples from historic painted surfaces. A microscopic H(2)SO(4)-treated sample from the Portrait of Evelyn Byrd produced a SERS spectrum that is consistent with a mixture of PB and IC. To our knowledge, this work represents the first SERS spectrum of indigo in oil paint and the first simultaneous detection of a mixture of blue organic and inorganic colorants in a single art sample using SERS.     

Nondestructive identification of natural and synthetic organic colorants in works of art by surface enhanced Raman scattering

We present a new method based on surface-enhanced Raman scattering (SERS) for the nondestructive identification of organic colorants in objects whose value or function precludes sampling, such as drawings, prints, historic and archeological textiles, handwritten or printed documents, and forensic evidence. A bead of a polymer hydrogel loaded with a solution containing water, an organic solvent, and a chelating agent is used to extract minimal amounts of the colorants from the work of art for SERS analysis. Using a gel as a medium for the solvent mixture confines its action only to the areas of the work of art covered by the gel bead. The gel bead is then removed from the work of art, covered with a drop of Ag colloid, and examined with a Raman microscope. Transfer of the dye from the substrate to the gel does not require removing a sample from the work of art, therefore preserving the physical integrity of the object. Spectrophotometric color measurements confirm that color change is below the limit perceivable by a human observer. Finally, the size of the polymer bead can be reduced to a fraction of a millimeter in order to further minimize any impact on the work of art, without detriment to the effectiveness of the method. The technique has been successfully used for the analysis of a mordant dye on the 15th century Netherlandish tapestry, "The Hunt for the Unicorn", and of a synthetic lake pigment on a Meiji period Japanese woodblock print.     

Identification and characterization of artists' red dyes and their mixtures by surface-enhanced Raman spectroscopy

Silver film over nanospheres (AgFONs) were successfully employed as surface-enhanced Raman spectroscopy (SERS) substrates to characterize several artists' red dyes including: alizarin, purpurin, carminic acid, cochineal, and lac dye. Spectra were collected on sample volumes (1 x 10(-6) M or 15 ng/microL) similar to those that would be found in a museum setting and were found to be higher in resolution and consistency than those collected on silver island films (AgIFs). In fact, to the best of the authors' knowledge, this work presents the highest resolution spectrum of the artists' material cochineal to date. In order to determine an optimized SERS system for dye identification, experiments were conducted in which laser excitation wavelengths were matched with correlating AgFON localized surface plasmon resonance (LSPR) maxima. Enhancements of approximately two orders of magnitude were seen when resonance SERS conditions were met in comparison to non-resonance SERS conditions. Finally, because most samples collected in a museum contain multiple dyestuffs, AgFONs were employed to simultaneously identify individual dyes within several dye mixtures. These results indicate that AgFONs have great potential to be used to identify not only real artwork samples containing a single dye but also samples containing dyes mixtures.     

Pigment identification by spectroscopic means: evidence consistent with the attribution of the painting Young Woman Seated at a Virginal to Vermeer

Technical examination of the painting Young Woman Seated at a Virginal by cross section and polarized light microscopy, chemical tests, surface microscopy, energy-dispersive X-ray analysis, and Raman microscopy has led to the identification of the pigments lead tin yellow (type I), lazurite, vermilion, calcite, lead white, red and yellow iron oxides, umber, lamp black, and green earth on the canvas. These pigments are entirely typical of Vermeer's palette and are consistent with a large body of other technical and art historical findings on paintings by Vermeer and other Dutch 17th century artists. While not authenticating the painting as being by Vermeer, the results provide further critical material that is consistent with this attribution. This case study also provides an opportunity to outline the role of analytical and forensic sciences in the examination and attribution of art objects.     

Functional Silk: Colored and Luminescent

Silkworm silk is among the most widely used natural fibers for textile and biomedical applications due to its extraordinary mechanical properties and superior biocompatibility. A number of physical and chemical processes have also been developed to reconstruct silk into various forms or to artificially produce silk‐like materials. In addition to the direct use and the delicate replication of silk's natural structure and properties, there is a growing interest to introduce more new functionalities into silk while maintaining its advantageous intrinsic properties. In this review we assess various methods and their merits to produce functional silk, specifically those with color and luminescence, through post‐processing steps as well as biological approaches. There is a highlight on intrinsically colored and luminescent silk produced directly from silkworms for a wide range of applications, and a discussion on the suitable molecular properties for being incorporated effectively into silk while it is being produced in the silk gland. With these understanding, a new generation of silk containing various functional materials (e.g., drugs, antibiotics and stimuli‐sensitive dyes) would be produced for novel applications such as cancer therapy with controlled release feature, wound dressing with monitoring/sensing feature, tissue engineering scaffolds with antibacterial, anticoagulant or anti‐inflammatory feature, and many others.     

Competitive Reaction Pathway for Site‐Selective Conjugation of Raman Dyes to Hotspots on Gold Nanorods for Greatly Enhanced SERS Performance

Common methods to prepare SERS (surface‐enhanced Raman scattering) probes rely on random conjugation of Raman dyes onto metal nanostructures, but most of the Raman dyes are not located at Raman‐intense electromagnetic hotspots thus not contributing to SERS enhancement substantially. Herein, a competitive reaction between transverse gold overgrowth and dye conjugation is described to achieve site selective conjugation of Raman dyes to the hotspots (ends) on gold nanorods (GNRs). The preferential overgrowth on the nanorod side surface creates a barrier to prevent the Raman dyes from binding to the side surface except the ends of the GNRs, where the highest SERS enhancement factors are expected. The SERS enhancement observed from this special structure is dozens of times larger than that from conjugates synthesized by conventional methods. This simple and powerful strategy to prepare SERS probes can be extended to different anisotropic metal nanostructures with electromagnetic hotspots and has immense potential in in‐depth SERS‐based biological imaging and single‐molecule detection.     

艺术设计中的黄金分割视觉结构分析

借助PhiMatrix图像软件,对古希腊时期的建筑及雕塑、文艺复兴时期的绘画艺术、19世纪以后的现代平面设计及产品设计等经典作品进行了黄金分割视觉结构分析,结果表明,这些作品均符合黄金分割比例关系。在长期的艺术实践中,黄金分割比例关系逐渐成为人们的审美标准,因此,具有黄金分割比例的设计构图更符合大众的审美心理。     

Surface-enhanced Raman scattering based approach for quantitative determination of creatinine in human serum

A novel surface-enhanced Raman scattering (SERS) based approach for the quantitative determination of creatinine in human serum is described. Using isotopically labeled (2-13C, 2,3-15N2) creatinine as internal standard, SERS acquires the character of a ratio method that works similar to the well-established isotope dilution techniques. In conjunction with multivariate data analysis, the method was successfully applied for quantifying creatinine at clinically relevant levels and below. A partial least-squares regression model was generated from a set of 87 calibration spectra covering the full range of mole fractions of neat creatinine. The prediction performance of the model was thereafter validated with independent reference samples giving a standard deviation of less than 2%. Finally, a conditioning procedure to prepare real serum samples for SERS-based creatinine analysis was worked out and validated. Measured serum creatinine concentrations are within 3% of the values obtained from gas chromatography/isotope dilution mass spectrometry on the same serum starting material.     

Spider silk as an active scaffold in the assembly of gold nanoparticles and application of the gold-silk bioconjugate in vapor sensing

Spider silk is being viewed with interest by materials scientists due to its excellent resilience and mechanical properties. In this paper we show that spider silk is an excellent scaffold for the one-step synthesis and assembly of gold nanoparticles. Formation of a gold nanoparticle-spider-silk bioconjugate material is accomplished by simple reaction of the fibers with aqueous chloroauric acid. The gold nanoparticles thus formed are strongly bound to the spider-silk fiber surface enabling study of the electrical properties of the nanobioconjugate. Using the well-known contraction/expansion behavior of the fibers in solvents of varying polarity, we show that exposure of the gold nanoparticle-spider silk bioconjugate to vapors of methanol and chloroform leads to changes in electrical transport through the nanoparticles and thus, the possibility of developing a vapor sensor. The bioconjugate shows excellent response time and cycling efficiency to methanol vapors. The activation energy of electron transport from one gold nanoparticle to another in the nanobiocojugate was determined from temperature-dependent electron-transport measurements to be approximately 1.7 eV.     

Surface-enhanced Raman spectroscopy of soft-landed polyatomic ions and molecules

Surface-enhanced Raman spectroscopy (SERS) was used to detect and characterize polyatomic cations and molecules that were electrosprayed into the gas phase and soft-landed in vacuum on plasma-treated silver substrates. Organic dyes such as crystal violet and Rhodamine B, the nucleobase cytosine, and nucleosides cytidine and 2'-deoxycytidine were immobilized by soft landing on plasma-treated metal surfaces at kinetic energies ranging from near thermal to 200 eV. While enhancing Raman scattering 10(5)-10(6)-fold, the metal surface effectively quenches the fluorescence that does not interfere with the Raman spectra. SERS spectra from submonolayer amounts of soft-landed compounds were sufficiently intense and reproducible to allow identification of Raman active vibrational modes for structure assignment. Soft-landed species appear to be microsolvated on the surface and bound via ion pairing or pi-complexation to the Ag atoms and ions in the surface oxide layer. Comparison of spectra from soft-landed and solution samples indicates that the molecules survive soft landing without significant chemical damage even when they strike the surface at hyperthermal collision energies.     

Biocompatibility and biodegradability of spider egg sac silk

Spider egg sac silk (SpESS) were enzymatically cleaned and their biodegradation in vivo and in vitro, as well as their biocompatibility were studied. Proteinase K treatment diminished the tenacity and the strain of the SpESS fibers in proportion to the enzyme concentration. Fibers treated with trypsin were not significantly affected. Tensile properties of Vicryl, SpESS and of silkworm (Bombyx mori) silk fibers (SWS) were measured after incubation in phosphate buffered saline (PBS) at 37 degrees C up to 12 weeks. Biodegradation of SpESS and SWS was insignificant compared to Vicryl. Five milligram SpESS fibers from laboratory grown spiders (Araneus diadematus) were treated with proteinases before sterilization and subcutaneously implanted in Wistar rats. After 1, 4 and 7 weeks the immunological reaction was compared to untreated SpESS and polyglactin (Vicryl) control samples. SpESS samples treated with trypsin only or in combination with a Proteinase K treatment induced less inflammatory reactions than untreated silk fibers. The enzymatical cleaning could diminish the tensile properties, but enhanced the biocompatibility of the SpESS fibers rendering them appropriate for use in biomaterial application where the slow biodegradability is an advantage.     

Cationization of cotton for industrial scale salt-free reactive dyeing of garments

Reactive dyeing of cotton garments involves two stages, namely exhaustion and fixation of dyes. The exhaustion stage in reactive dyeing requires high quantity of salt. After dyeing process, the highly saline coloured effluent is discharged and the treatment of this effluent at present is not economically viable and making industries look for other alternatives for usage of salt. Cationization of cotton is one of the effective alternatives to overcome the usage of the salt. The present work focuses on the exhaust method of cationization of garments at an industrial scale using 3-chloro-2-hydroxypropyl trimethylammonium chloride as a cationic agent. Two commercially popular reactive dyes namely Navy Blue and Green dyes were chosen for dyeing the garments at 10% shade. The results of dyeing were evaluated on the basis of colour strength, dyeing levelness and colour fastness. The uniformity of dye on the fabrics was evaluated based on dyeing levelness and was found to be good for cationized cotton dyed garments. The fastness properties of dyed fabrics to washing and light were good. The dye utilization in the cationized cotton dyed garments was twice as that of the conventionally dyed cotton garments. The environmental hazard posed by the highly saline coloured effluent could be easily mitigated by the salt-free reactive dyeing process.     

A novel route to synthesize CdS quantum dots on the surface of silk fibers via γ-radiation

CdS quantum dots (QDs) were successfully synthesized on the surface of silk fibers via γ-ray irradiation. Scanning electron microscope (SEM) measurement revealed that the particles on the silk fibers were less than 15nm in diameter. The energy dispersion spectrum (EDS), X-ray diffraction (XRD), laser scanning confocal microscope (LSCM) were also used to identify and investigate the properties of products. Moreover, a mechanism for the formation of CdS QDs on silk fibers under γ-radiation was generally discussed. The resulting silk fibers coated with CdS QDs might be useful as smart structural fabrics in a range of applications.     

Surface-enhanced Raman scattering dendritic substrates fabricated by deposition of gold and silver on silicon

This paper reports a study on the preparation of gold nanoparticles and silver dendrites on silicon substrates by immersion plating. Firstly, gold was deposited onto silicon wafer from HF aqueous solution containing HAuCl4. Then, the silicon wafer deposited gold was dipped into HF aqueous solution of AgNO3 to form silver coating gold film. Scanning electron microscopy reveals a uniform gold film consisted of gold nanoparticles and rough silver coating gold film containing uniform dendritic structures on silicon surface. By SERS (surface-enhanced Raman scattering) measurements, the fabricated gold and silver coating gold substrates activity toward SERS is assessed. The SERS spectra of crystal violet on the fabricated substrates reflect the different SERS activities on gold nanoparticles film and silver coating gold dendrites film. Compared with pure gold film on silicon, the film of silver coating gold dendrites film significantly increased the SERS intensity. As the fabrication process is very simple, cost-effective and reproducible, and the fabricated silver coating gold substrate is of excellent enhancement ability, spatial uniformity and good stability.