Visualization of latent fingerprints (LFPs) on metal surfaces using curcumin (CUR) remains a largely underexplored approach. Here, CUR was applied for LFP visualization on brass, steel, Al, and Cu plates and on real-life metal objects (keys, coins, and knives). Fingerprint quality was assessed by stereomicroscopy and characterized in detail using profilometry, SEM/EDS, and vibrational spectroscopy (IR and Raman). Profilometry and SEM/EDS revealed substrate-dependent differences in CUR layer morphology, roughness, and aggregation, indicating that papillary ridge contrast is governed by interactions between fingerprint residues and the underlying surface. Vibrational spectroscopy confirmed the preferential interaction of CUR with lipid-rich LFP components rather than non-specific adsorption on metal substrates and revealed compositional differences in fingerprints deposited on brass and stainless steel. The practical applicability of CUR on real-life metal objects demonstrated that fingerprint persistence and visibility met the legal requirement for forensic usability in the Czech Republic (> 10 minutiae). Overall, these results demonstrate that, under appropriate surface conditions, CUR provides a reliable and environmentally sustainable strategy for targeted LFP visualization on metal substrates.

Polyazulene is an underrated conductive polymer characterized by its unique building blocks involving a fused-ring structure with an intrinsic dipole moment. It has been studied with a focus on the development of organic electronics, such as photovoltaic cells. However, the biological properties of polyazulene have not been reported to date. This study, the first of its kind, not only describes the properties of electrochemically and chemically synthesised polyazulenes and so-called true polyazulene, but also characterises their cytocompatibility. The physico-chemical properties of polyazulene powders and films were characterized by FTIR, Raman and UV-Vis spectroscopy, profilometry, scanning electron microscopy, voltammetry, van der Pauw conductivity measurement, and thermogravimetric analysis. Their cytocompatibility was explored using NIH/3T3 mouse embryonic fibroblasts, HaCaT human keratinocytes, and ES R1 mouse embryonic stem cells. Our results indicate that the tested polyazulenes exhibit an overall favourable short-term in vitro cytocompatibility with limitations varying according to the synthesis method and conditions. Electrochemically synthesized polyazulene formed continuous films with moderate conductivity under optimized deposition conditions, whereas chemically prepared films were inhomogeneous for reliable conductivity measurements. These differences in conductivity therefore primarily reflect variation in film morphology and deposition conditions rather than intrinsic bulk electronic properties of the respective polyazulene types.

The present study investigates the electrical stability of hybrid composites consisting of tungsten microparticles embedded in a semiconducting globular or nanotubular polypyrrole matrix. As demonstrated, the resistivity of the composites during continuous exposure to 160 °C for 5 days displayed an unexpected trend: an initial increase followed by a significant decrease after several days of heating. While energy-dispersive X-ray spectroscopy ruled out tungsten sedimentation as a cause, FTIR and Raman spectroscopies revealed that the prolonged thermal treatment induced a partial carbonization of polypyrrole. This structural transformation effectively improved the composite conductivity, thus explaining the surprising late-stage drop in resistivity.

Buffing dust, one of the collagenous wastes produced in the footwear industry, was carbonized at 400-1200 degrees C in an inert atmosphere to microfibrous nitrogen-containing biocarbons enriched with chromium. The evolution of molecular microstructure with increasing carbonization temperature or exposure time was followed with FTIR and Raman spectra. The resistivity of the powdered products was determined by van der Pauw four-point method and recorded as a function of applied pressure in the 0.1-10 MPa range. The highest conductivity 13.9 S cm- 1 at 10 MPa was found after the carbonization at 1200 degrees C. The mechanical properties, such as the change of sample volume with applied pressure, are also discussed. The specific surface area was low, ca 5-7 m2g-1, independent of the carbonization temperature. This parameter was enhanced by the chemical activation with ammonium peroxydisulfate or potassium hydroxide by two orders of magnitude, while the conductivity decreased at the same time by less than one order of magnitude.

The development of composites with tailored surface properties and electrical conductivity is critical for various biomedical applications. However, a substantial gap remains in understanding how the unique properties of cellulose, such as biocompatibility and renewability can be effectively combined with those of polyaniline (PANI), including electrical conductivity, antibacterial, and antioxidant activity, to create composite films with advanced multifunctional performance. Indeed, conductivity can be used not only to monitor biological functions but also as a cell instructive factor. To meet these requirements, thin composite films were synthetized using oxidative polymerization of aniline hydrochloride with ammonium peroxydisulfate in the presence of either cellulose nanocrystals (CNC) or cellulose nanofibres (CNF). Their cytocompatibility was demonstrated with the NIH/3 T3 fibroblast line and highly progressive human induced pluripotent stem cells. The films also showed antibacterial activity against Staphyloccocus aureus and Escherichia coli, surpassing that of pristine PANI and meeting the EN ISO 20743 criteria for materials with significant activity (reducing CFU value to zero). Comprehensive physicochemical characterization revealed that the films possessed exceptional DPPH radical scavenging achieving their complete (100 %) removal within 15 min, and electrical conductivity within units of S cm-1. Raman spectroscopy showed that PANI/CNC composites were more resistant to deprotonation caused by laser illumination than PANI/CNF, which resulted from the presence of sulfate groups on the CNC surface. These findings highlight that PANI/CNC and PANI/CNF films are promising materials for applications requiring surfaces that are simultaneously biocompatible, electrically conductive, and antibacterial.

This work presents an electrochemical approach to the visualization of fingerprints on brass cartridges with the aim of characterizing how visualization using polyphenazine dyes affects latent fingerprints. After visualization using cyclic voltammetry and chronoamperometry, the individual layers (substrate/fingerprint/polymer film) and their interfaces were characterized profilometrically, spectroscopically by Fourier transform infrared spectroscopy (FT-IR) and via scanning electron microscopy (SEM). The morphology and surface quality observed by SEM revealed the size of the particles formed from both electrochemically deposited polymer films. Profilometry showed the homogeneity and surface roughness of the deposited layers. It was found that poly(toluidine blue) forms a thinner homogeneous layer with better adhesion to the brass substrate than the poly(neutral red) film. Based on the FT-IR spectra, it can be concluded that the polymer films of the dyes were deposited on the surface of the substrates as a result of the observed changes and band intensities belonging to the mono- and polymer forms of neutral red and toluidine blue, respectively. The electrochemical visualization method proved to be effective, gentle, and relatively fast.

Tungsten microparticles were coated with globular or nanotubular polypyrrole in situ during the oxidation of pyrrole in aqueous medium with ammonium peroxydisulfate or iron(III) chloride, respectively. The resulting core–shell composites with various contents of tungsten were obtained as powders composed of metal particles embedded in a semiconducting polymer matrix. The coating of tungsten with polypyrrole was analysed by FTIR and Raman spectroscopies. The resistivity of composite powders was determined by the four-point van der Pauw method as a function of pressure applied up to 10 MPa. The degree of compression was also recorded and its relation to electrical properties is discussed on the basis of the percolation concept. The electrical properties of composites are afforded by polypyrrole matrix and they are independent of tungsten content. As the conducting tungsten particles are separated by polypyrrole shells, they cannot produce conducting pathways and behave similarly as a nonconducting filler.

The in situ coating of polymer substrate with polypyrrole, described herein with detailed know-how, represents a novel technique of surface functionalization. The choice of oxidizing agent and the polymerization time both affect the properties of the thin polypyrrole layer. The specific conductivity, free surface energy, thickness, topography, and FTIR spectra of polypyrrole layer were determined. The conductive coatings were further used to functionalize both isotropic and anisotropic electrospun polyurethane nanofibrous mats to show their applicability and study the bioactive effect of both the anisotropy and conductivity together. The morphology of composites was studied by means of atomic force microscopy and scanning electron microscopy. A complex cytocompatibility study was performed, including determining cytotoxicity by optical and fluorescence microscopy, the advanced qualification of cell morphology by cell-image analysis, and a study of stem cell behavior. The results clearly showed the significant impact of substrate modification on cells, especially on fibroblasts while the embryonic stem cells were less affected. This study shows not only the effective way to prepare a thin conducting layer based on polypyrrole but also demonstrates its importance for the fabrication of smart biomaterials.

Core–shell inorganic/organic composites have often been applied as fillers in electromagnetic interference shielding. Those composed of conducting polymers and ferrites are of particular interests with respect to their electrical and magnetic properties. Pyrrole was oxidized in aqueous medium in the presence of manganese-zinc ferrite microparticles with ammonium peroxydisulfate or iron(III) chloride to yield polypyrrole-coated, core–shell microstructures. The effect of methyl orange dye on the conversion of globular polypyrrole to nanotubes has been demonstrated by electron microscopy when iron(III) chloride was used as an oxidant. The formation of polypyrrole was proved by FTIR spectroscopy. The completeness of ferrite coating was confirmed by Raman spectroscopy. The resistivity of composite powders was determined by four-point van der Pauw method as a function of pressure applied up to 10 MPa. The conductivity of composite powders was determined by a polypyrrole matrix and only moderately decreased with increasing content of ferrite. The highest conductivity of composites, 13–25 S cm−1, was achieved after the deposition of polypyrrole nanotubes. Magnetic properties of composites have not been affected by the polypyrrole moiety, and the magnetization of composites was proportional to the ferrite content.

Zwitterionic oligomers of 3-aminobenzoic acid (o-3ABA) were electrochemically deposited on screen-printed electrodes. The o-3ABA-modified electrodes offer new possibilities for the discrimination and determination of new psychoactive substances.

Iron microparticles were coated with polypyrrole in situ during the chemical oxidation of pyrrole with ammonium peroxydisulfate in aqueous medium. A series of hybrid organic/inorganic core–shell materials were prepared with 30–76 wt% iron content. Polypyrrole coating was revealed by scanning electron microscopy, and its molecular structure and completeness were proved by FTIR and Raman spectroscopies. The composites of polypyrrole/carbonyl iron were obtained as powders and characterized with respect to their electrical properties. Their resistivity was monitored by the four-point van der Pauw method under 0.01–10 MPa pressure. In an apparent paradox, the resistivity of composites increased from the units Ω cm for neat polypyrrole to thousands Ω cm for the highest iron content despite the high conductivity of iron. This means that composite conductivity is controlled by the electrical properties of the polypyrrole matrix. The change of sample size during the compression was also recorded and provides a parameter reflecting the mechanical properties of composites. In addition to conductivity, the composites displayed magnetic properties afforded by the presence of iron. The study also illustrates the feasibility of the polypyrrole coating on macroscopic objects, demonstrated by an iron nail, and offers potential application in the corrosion protection of iron. The differences in the morphology of micro- and macroscopic polypyrrole objects are described.

This work deals with the coating properties of synthetic latices comprising two kinds of polymers, specifically polyacrylate and polypyrrole, which were simultaneously formed by semi-continuous emulsion polymerization using a “one-pot” synthesis strategy. In this procedure, both the emulsion polymerization of acrylate monomers and the oxidative polymerization of pyrrole occurred concurrently in one reactor. Polyacrylate latices differing in polypyrrole loading were prepared by applying various dosages of pyrrole, specifically 0, 0.25, and 0.50, based on the fraction of acrylate monomers. The effect of the in situ incorporated polypyrrole component (having the nature of submicron composite polypyrrole-coated polyacrylate latex particles) on the physico-mechanical properties and chemical resistance of the resulting heterogeneous coating films was investigated. The interaction of incorporated polypyrrole and anti-corrosion pigments (see ZnS, Zn3(PO4)2, ZnFe2O4, MoS2, and ZnO) on the corrosion resistance of coatings was evaluated by using the electrochemical linear polarization technique. The polyacrylate latex prepared with the lowest polypyrrole loading (achieved by polymerizing 0.25 wt. % of pyrrole related to acrylic monomers) was found to be the optimum binder for waterborne anticorrosive coatings based on their properties and protective function. Their compatibility with the selected types of pigments was studied for these latex binders. In addition, their influence on the anti-corrosion efficiency of polyacrylate paint films was evaluated using the linear polarization electrochemical technique. For high corrosion resistance, the ZnS and MoS2 pigments, showing compatibility with polyacrylate latices containing the polypyrrole component, proved to be advantageous.

Chromium-tanned pigskin leather was carbonized in three ways: (1) pyrolysis in an inert atmosphere at 800 °C, (2) pre-carbonization at 500 °C followed by the activation with KOH at 800 °C, and (3) direct activation with excess KOH at 800 °C. The yield of biochars was comparable, 24–28 wt.

New psychoactive substances, including 2-aminoindane, pose significant health risks due to their availability and structural similarity to amphetamines. Current detection methods are limited by lengthy analysis times and complex sample preparation. To address this, we present the first voltammetric determination of 2-aminoindane in oral fluid using a graphite electrode modified with a methoxyphenylthiophene-based layer. The electrochemically deposited layer was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and both infrared and Raman spectroscopies. After the electropolymerization of methoxyphenylthiophene, the electrode was homogeneously covered with shorter oligomers of the substituted polythiophene. Cyclic and square-wave voltammetry were used to gain insight into the interaction between the modified electrode and 2-aminoindane. The modification of the electrode surface enables to record the oxidation of the primary amino group at 0.85 V, with an additional signal assigned to specific interactions being observed at 1.33 V. Determination of a 1.0 × 10–4 M 2-aminoindane concentration in oral fluids was possible, with a recovery ranging from 98 to 100

Macroporous melamine/formaldehyde sponge was coated in situ during the oxidation of pyrrole with iron(III) chloride hexahydrate in aqueous medium. The reaction mixture contained a heteropolyacid, silicotungstic acid, which protonated polypyrrole. Polypyrrole/silicotungstate deposits were prepared either in globular form or as nanotubes. The resulting hybrid composites thus combine an organic conducting polymer with inorganic component known, e.g., for its proton conductivity and electrocatalytic activity. The specific surface area of all materials was of the order of tens m2g- 1. The molecular structure is discussed on the basis of FTIR and Raman spectra. The resistivity of the sponges was recorded as a function of compression to 10 MPa and it decreased from the order of 10 omega cm to 0.1 omega cm. The sponges were tested in electromagnetic interference shielding and absorbed over 80% of 9 GHz radiation frequency. The shielding is based mainly on the radiation absorption efficiency,-8.2 dB for globular polypyrrole and-13.1 dB for nanotubes, afforded by silicotungstic component. Hybrid composite sponges were subsequently carbonized at 650 degrees C in inert atmosphere when they converted to a sponge-like macroporous carbons enriched with nitrogen atoms. Their resistivity increased by two orders of magnitude after this process. The absorption of electromagnetic radiation, however, fell below 10%. Original and carbonized hybrid sponges may be of interest in the construction of macroporous electrodes.

Conductive polypyrrole nanotubes were synthesized with a two-step one-pot synthesis. During synthesis, the nanotubes were decorated with magnetite nanoparticles at different concentrations granting them magnetic properties. The characterization of the tubes revealed differences from the theoretical reactions. A bidisperse magnetorheological fluid (MRF) was prepared by mixing the composite polypyrrole nanotubes/magnetite nanoparticles with commercial carbonyl iron spherical microparticles in silicone oil. The rheological properties of the bidisperse system were studied under the presence of magnetic field at room and elevated temperature. An enhancement of the MR effect with the presence of the nanotubes was observed when compared with a standard MRF consisted only of magnetic microparticles. Due to the faster magnetic saturation of the nanotubes, this enhancement is exceptionally high at low magnetic fields. The stability of the system is studied under dynamic conditions where it is revealed that the nanotubes keep the standard particles well dispersed with the sedimentation improving by more than 50%.

Hybrid organic/inorganic conducting and magnetic composites of core–shell type have been prepared by in-situ coating of nickel microparticles with polypyrrole. Three series of syntheses have been made. In the first, pyrrole was oxidised with ammonium peroxydisulfate in water in the presence of various amounts of nickel and the composites contained up to 83 wt% of this metal. The second series used 0.1 M sulfuric acid as a reaction medium. Finally, the composites with polypyrrole nanotubes were prepared in water in the presence of structure-guiding methyl orange dye. The nanotubes have always been accompanied by the globular morphology. FTIR and Raman spectroscopies confirmed the formation of polypyrrole. The resistivity of composite powders of the order of tens to hundreds Ω cm was monitored as a function of pressure up to 10 MPa. The resistivity of composites slightly increased with increasing content of nickel. This apparent paradox is explained by the coating of nickel particles with polypyrrole, which prevents their contact and subsequent generation of metallic conducting pathways. Electrical properties were practically independent of the way of composite preparation or nickel content and were controlled by the polypyrrole phase. On the contrary, magnetic properties were determined exclusively by nickel content. The composites were used as a solid phase to prepare a magnetorheological fluid. The test showed better performance when compared with a different nickel system reported earlier.

The conductivity of chromium-tanned pigskin leather waste carbonized in various manner to nitrogen-containing carbons is reported. Four protocols have been tested: (1) The simple carbonization at 800 & DEG;C in inert atmosphere, (2) the carbonization at 500 & DEG;C followed by the activation with potassium hydroxide at 800 & DEG;C, (3) direct activation with the alkali at 800 & DEG;C and (4) the similar activation with potassium hydroxide excess. The fibrous collagen morphology was preserved after the carbonization except for some shrinkage. The yield in the simple carbonization, 26.9 wt%, was reduced to 23.9 wt% for the activated products. Elemental analysis indicated reduced content of organic elements after carbonization, and X-ray fluorescence the composition of growing inorganic part. The chromium content in biochar was close to 12 wt% and the X-ray diffraction revealed also the presence of metallic chromium in addition to expected chromium(III) oxide and sulfide. FTIR and Raman spectroscopies demonstrated the typical pattern of carbonized materials. The specific surface area and pore volume increased after the activation. The resistivity of the powdered carbonized leather was determined in four-point van der Pauw setup. It decreased by more than one order of magnitude as applied pressure increased from 0.1 to 10 MPa. The sample conductivity depended only a little on the way of carbonization and was of the order of tenths to units S cm-1 at 10 MPa. The precarbonization followed by the activation provided the best result with respect to the yield, nitrogen-content, specific surface area and conductivity of the carbonized material.

In the search for functional organic biomaterials, leather constituted by collagen fibers was coated with a conducting polymer, polypyrrole. The coating was carried out during the oxidation of pyrrole in an aqueous solution of poly(N-vinylpyrrolidone) in the presence of five organic dyes: crystal violet, neutral red, methyl orange, acriflavine, and methylene blue. This technique ensures the uniform coating of collagen fibers with polypyrrole and incorporation of organic dyes. The surface morphology was observed with scanning electron microscopy and the transverse profile, reflecting the penetration of the conducting phase into the leather body with optical microscopy. While the polypyrrole coating endows leather with electrical conductivity, organic dyes are expected to affect the polymer morphology and to provide an antibacterial effect. The lowest sheet resistance and antibacterial activity were obtained with crystal violet. This type of coating was characterized in more detail. Infrared spectroscopy confirmed the coating of collagen fibers with polypyrrole and dye incorporation. Mechanical properties were extended to the cyclic bending of the leather at various angles over 5000 cycles. The relative resistance changes were a few percent, indicating good electrical stability during repeated mechanical stress.

Melamine foam became a popular flexible material, which can be used as a free-standing scaffold of electrically conductive fillers for development of experimental low-pressure sensors. Here, melamine foam was covered with conducting polymer polypyrrole of nanotubular morphology (PPy-NT) to obtain a material with high conductivity and mechanical flexibility. A surfactant polyvinylpyrrolidone and two carbonaceous fillers (carbon black and expanded graphite) serving as modifying agents of electrical and mechanical properties were used as composite components during in situ polymerization and deposition of PPy-NT on the surface of melamine foam. Electrical, mechanical, and structural properties of the fillers and their melamine composites were assessed and discussed. Effects of the surfactant and the fillers on pressure sensing properties of melamine composites were studied using low pressure testing (Delta p < 160 kPa) in terms of a characteristic curve, stability, repeatability, hysteresis and memory effect. Impedance spectroscopy in the range of 4 Hz to 5 MHz was employed as a tool for better understanding of electrical behavior of a melamine foam under the stress. An equivalent electrical circuit of foam samples consisting of parallel RC and distributed elements was estimated, modelled and compared with all measured data. Overall, prepared melamine composites exhibit practically applicable piezoresistive effect (impedance Z changes approx. in four orders of magnitude in the measured range, which can be modified by addition of carbonaceous components), DC electrical resistivity, volt-ampere characteristics as well as interesting AC electrical properties. On the other side, they suffer from memory effect (up to 40%) and hysteresis (30 - 45%) appearing especially when a testing pressure was too high. Hence, the goal of this work was to assess and present strengths and weaknesses of electromechanical properties of melamine foams, which have substantial influence on their application in highly sensitive piezoresistive pressure sensors or flexible supercapacitors and batteries.