Substituted naphthoquinones as novel amino acid sensitive reagents for the detection of latent fingermarks on paper surfaces

In this paper, we present our preliminary studies into naphthoquinones as novel reagents for the detection of latent fingermarks on paper. Latent fingermarks deposited on paper substrates were treated with solutions of selected naphthoquinones in ethyl acetate/HFE-7100, with subsequent heating. The selected compounds were 1,4-dihydroxy-2-naphthoic acid, 1,2-naphthoquinone-4-sulfonate, 2-methoxy-1,4-naphthoquinone and 2-methyl-1,4-naphthoquinone. All of the tested compounds yielded purple-brown visible fingermarks, which also exhibited photoluminescence when illuminated with a high intensity filtered light source at 555nm and viewed through red goggles. Indirect heat using an oven at 150 ◦C for 1 h was found to be superior to direct heat with an iron, which while providing faster development lead to increased levels of background colouration. Luminescence spectrophotometry revealed differences in photoluminescence characteristics for fingermarks developed with the different naphthoquinones, with excitation over the range 530–590 nm. Luminescence spectrophotometry of developed lysine, glycine and serine spots on paper was used to confirm that the naphthoquinones were reacting with amino acids in the latent fingermark.

Solvent extraction and purification of sugars from hemicellulose hydrolysates using boronic acid carriers

Research was performed to determine whether it was technically feasible to use boronic acid extractants to purify and concentrate the sugars present in hemicellulose hydrolysates. Initially, five types of boronic acids (phenylboronic acid, 3,5-dimethylphenylboronic acid, 4-tert-butylphenylboronic acid, trans-β-styreneboronic acid or naphthalene-2-boronic acid) dissolved in an organic diluent (Shellsol® 2046 or Exxal® 10) containing the quaternary amine Aliquat® 336 were tested for their ability to extract sugars (fructose, glucose, sucrose and xylose) from a buffered, immiscible aqueous solution. Naphthalene- 2-boronic acid was found to give the greatest extraction of xylose regardless of which diluent was used. Trials were then conducted to extract xylose and glucose from solutions derived from the dilute acid hydrolysis of sugar cane bagasse and to then strip the loaded organic solutions using an aqueous solution containing hydrochloric acid. This produced a strip solution in which the xylose concentration had been increased over 7× that of the original hydrolysate while reducing the concentration of the undesirable acid-soluble lignin by over 90%. Hence, this process can be exploited to produce high concentration xylose solutions suitable for direct fermentation.

Effect of synthesis parameters on the electrical conductivity of polypyrrole-coated poly(ethylene terephthalate) fabrics

The effects of pyrrole, anthraquinone-2-sulphonic acid (AQSA) and iron(III) chloride (FeCl3) concentrations, reaction time and temperature on the electrical conductivity of polypyrrole (PPy) - coated poly(ethylene terephthalate) (PET) fabrics were investigated. With an increase in both the AQSA and FeCl3 concentrations, resistivity decreased to a point beyond which higher concentrations led to increased surface resistivity. Erosion of the polymer coating, in dynamic synthesis from continual abrasion, manifested as an exponential increase in the resistance of the coated textile substrate. This was not encountered in static synthesis conditions. Temperature affected the degree of surface and bulk polymerisation. The effect of polymerisation temperature on conductivity was negligible. Conductive polymer coating on textiles through chemical polymerisation enabled a smooth coherent film to encase individual fibres, which did not affect the tactile properties of the host substrate. The optimum FeCl3/pyrrole and AQSA FeCl3/pyrrole molar ratios were found to be 2.22 and 0.40 respectively.

Characterization of conducting polymer coated synthetic fabrics for heat generation

Heat generation in fabrics coated with the conductive polymer polypyrrole was investigated. The PET fabrics were coated by chemical synthesis using four different oxidizing agent–dopant combinations. The samples from the four different dopant systems all show an increase in temperature when a fixed voltage is applied to the fabric. The antraquinone-2-sulfonic acid (AQSA) sodium salt doped polypyrrole coating was the most effective in heat generation whereas the sodium perchlorate dopant system was the least effective. The power density per unit area achieved in polypyrrole coated polyester–Lycra® fabric with 0.027 mol/l of AQSA acting as dopant was 430 W/m². The power density per unit area achieved for the sodium perchlorate system, using the same synthesis conditions, was 55 W/m².

The emitting species formed by the oxidation of hydrazides with hypohalites or N-halosuccinimides

The chemiluminescence accompanying the oxidation of salicylic hydrazide (2-hydroxybenzoic acid hydrazide) with hypochlorite, hypobromite, N-chlorosuccinimide, N-bromosuccinimide or hydrogen peroxide with cobalt(II) matched the photoluminescence emission of salicylic acid. In a related reaction, the oxidation of a mixture of isoniazid and ammonia, a synergistic effect was observed. The chemiluminescence spectrum for this reaction matches that accompanying the oxidation of the hydrazide, rather than the oxidation of ammonia. These results were used to assess mechanisms proposed by previous authors.

Generating heat from conducting polypyrrole-coated PET fabrics

Heating effects in polypyrrole-coated polyethyleneterephthalate (PET)-Lycra® fabrics were studied. Chemical synthesis was employed to coat the PET fabrics by polypyrrole using ferric chloride as oxidant and antraquinone- 2-sulfonic acid (AQSA) and naphthalene sulfonic acid (NSA) as dopants. The coated fabrics exhibited reasonable electrical stability, possessed high electrical conductivity, and were effective in heat generation. Surface resistance of polypyrrole-coated fabrics ranged from approximately 150 to 500 /square. Different connections between conductive fabrics and the power source were examined. When subjected to a constant voltage of 24 V, the current transmitted through the fabric decreased about 10% in 72 h. An increase in resistance of conductive fabrics subjected to constant voltage was observed

Electromagnetic shielding properties of polypyrrole/polyester composites in the 1–18 GHz frequency range

The dielectric characteristics of conducting polymer-coated textiles in the frequency range 1–18 GHz were investigated using a non-contact, non-destructive free space technique. Polypyrrole coatings were applied by solution polymerization on fabric substrates using a range of concentrations of para-toluene-2-sulfonic acid (pTSA) as dopant and ferric chloride as oxidant. The conducting polymer coatings exhibited dispersive permittivity behaviour with a decrease in real and imaginary components of complex permittivity as frequency increased in the range tested. Both the permittivity and the loss factor were affected by the polymerization time of the conductive coating. It was found that the total shielding efficiency of these conductive fabrics is significant at short polymerization times and increases to values exceeding 80% with longer polymerization times. The reflection contribution to electromagnetic shielding also increases with polymerization time.

The effects of dye dopants on the conductivity and optical absorption properties of polypyrrole

Ten anionic compounds, including four acidic dyes, were used to dope polypyrrole powder. The effects of the dopants on density, optical absorption and conductivity of the polypyrroles were studied. The presence of the dopant in the conducting polymer matrix was verified by ATR-FTIR spectroscopy. Density function theory (DFT) simulation was used to understand the effect of the dopants on the solid structure, optical absorption and energy band structures. Anthraquinone-2-sulfonic acid-doped polypyrrole yielded the highest conductivity. The dye-doped polypyrrole showed an enhancement in its UV–vis optical absorption.

Conductive fabrics for heating applications

By coating textiles with electrically conductive organic polymers, we are able to produce functional, intelligent fabrics. These fabrics can be utilised in applications such as gas sensors, actuators, electromagnetic shielding, radar absorption, selected frequency filtering in indoor wireless applications, and heating applications where vital parts of the body can be heated without embedding any wiring through the fabric.

Heat generation in fabrics coated with the conductive polymer polypyrrole was investigated. The fabrics were coated by chemical synthesis methods by oxidizing the pyrrole monomer in the presence of the fabric substrate. Ferric chloride was selected as the oxidizing agent and anthraquinone-2-sulfonic acid (AQSA) sodium salt monohydrate as the dopant.

Conductive fabrics were characterized by resistivity measurements, scanning electron microscopy, thermal imaging, current transmission over a period of time and calculations of power density per unit area. Effects of reaction conditions on the electrical properties and heat generated are presented. Polypyrrole coated fabrics were stable and possessed high electrical conductivity. Resistivity values ranged from 100-500 ohms/square depending on the reaction parameters. When subjected to a constant voltage of 24V, the polypyrrole coated polyester-Lycra® fabric doped with AQSA reached a maximum temperature of 42°C and a power density per unit area of 430 W/m² was achieved.

Improvement of adhesion of conductive polypyrrole coating on wool and polyester fabrics using atmospheric plasma treatment

In this paper wool and polyester fabrics were pretreated with atmospheric plasma glow discharge (APGD) to improve the ability of the substrate to bond with anthraquinone-2-sulfonic acid doped conducting polypyrrole coating. A range of APGD gas mixtures and treatment times were investigated. APGD treated fabrics were tested for surface contact angle, wettability and surface energy change. Effect of the plasma treatment on the binding strength was analyzed by studying abrasion resistance, surface resistivity and reflectance. Investigations showed that treated fabrics exhibited better hydrophilicity and increased surface energy. Surface treatment by an APGD gas mixture of 95% helium/5% nitrogen yielded the best results with respect to coating uniformity, abrasion resistance and conductivity.

Electromagnetic interference shielding and radiation absorption in thin polypyrrole films

Results of permittivity measurements, electromagnetic interference shielding effectiveness, and heat generation due to microwave absorption in conducting polymer coated textiles are reported and discussed. The intrinsically conducting polymer, polypyrrole, doped with anthraquinone-2-sulfonic acid (AQSA) or para-toluene-2-sulfonic acid (pTSA) was applied on textile substrates and the resulting materials were investigated in the frequency range 1–18 GHz. The 0.54 mm thick conducting textile/polypyrrole composites absorbed up to 49.5% of the incident 30–35 W microwave radiation. A thermography station was used to monitor the temperature of these composites during the irradiation process, where absorption was confirmed via visible heat losses. Samples with lower conductivity showed larger temperature increases caused by microwave absorption compared to samples with higher conductivity. A sample with an average sheet resistivity of 150 Ω/sq. showed a maximum temperature increase of 5.27 °C, whilst a sample with a lower resistivity (105 Ω/sq.) rose by 3.85 °C.

Dielectric characterization of conducting textiles using free space transmission measurements: accuracy and methods for improvement

The dielectric behaviour of in-situ polymerized thin polypyrrole (PPy) films on synthetic textile substrates were obtained in the 1–18 GHz region using free space transmission and reflection methods. The PPy/para-toluene-2-sulphonic acid (pTSA) coated fabrics exhibited an absorption dominated total shielding effectiveness (SE) of up to −7.34 dB, which corresponds to more than 80% of incident radiation. The permittivity response is significantly influenced by the changes in ambient conditions, sample size and diffraction around the sample. Mathematical diffraction removal, time-gating tools and high gain horns were utilized to improve the permittivity response. A narrow time-gate of 0.15 ns produced accurate response for frequencies above 6.7 GHz and the high gain horns further improved the response in the 7.5–18 GHz range. Errors between calculated and measured values of reflection were most commonly within 2%, indicating good accuracy of the method.

Conducting polymer coated fabrics for potential applications in microwave frequencies : a study of electromagnetic properties

The microwave reflection, transmission and complex permittivity of paratoluene-2-sulfonic acid doped conducting polypyrrole (PPy/pTSA) coated Nylon-Lycra textiles in the 1-18 GHz frequency were investigated. The real part of permittivity increased with polymerization time and dopant concentration, reaching a plateau at certain dopant concentration and polymerization time. The imaginary part of permittivity showed a frequency dependent change throughout the tested range. All the samples had higher values of absorption than reflection. The total electromagnetic shielding effectiveness exceeded 80% for the highly pTSA doped samples coated for 3 hours.

Thermal conductivity studies on wool fabrics with conductive coatings

Methods of improving the thermal conductivity of wool fabrics have been investigated. Thermal conductivity measurement techniques, influence of synthesis parameters on the thermal conductivity of polypyrrole (PPy)-coated wool fabrics, and the relationship between electrical conductivity and thermal conductivity of PPy-coated wool fabrics are presented. An improvement in thermal conductivity was observed when fabrics were coated with the PPy. The thermal conductivity increased with the increase of pyrrole concentration and synthesis time. Anthraquinone-2-sulfonic acid and ferric chloride showed an optimal concentration for their influence on the thermal conductivity of the coated fabric. The improvement of thermal conductivity of wool fabrics is also investigated by Physical Vapor Deposition technique.