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The crystal violet (CV) staining technique represents a prevalent approach for the development of latent fingerprints, especially on adhesive tape surfaces. Nevertheless, the technique necessitates intricate formulations to augment its performance. In this investigation, an optimized CV staining protocol was developed, characterized by the absence of residual dye on the target substrates and the capability of facilitating fingerprint visualization under ambient light conditions. Four donors, comprising two males and two females, deposited natural fingerprints on various substrates, including glass microscope slides, aluminum foil, and 115 g glossy coated paper, without any specific guidelines. Fingerprints developed using cyanoacrylate fuming served as benchmarks and were contrasted with those generated through alternative methods: CV, ardrox, rhodamine 6G, powdering, and the optimized CV staining protocol. The fingerprint development experiment was replicated at seven distinct time intervals, encompassing 1 day, 1 week, 1, 3, 6, 9, and 12 months, resulting in a dataset of 420 fingerprints. The evaluation of fingerprint identifiability employed a scoring system established by the Home Office Centre for Applied Science and Technology. The results indicated that the optimized CV staining technique demonstrated superior performance, boasting a 92.9% rate of identifiable fingerprint development in contrast to other employed methodologies. Consequently, this optimized CV staining approach is recommended as an efficient, rapid, and straightforward critical dyeing method, applicable to a wide array of substrates in forensic investigations., (© 2024 The Authors. Journal of Forensic Sciences published by Wiley Periodicals LLC on behalf of American Academy of Forensic Sciences.)

With the advanced development of miniaturized Raman spectroscopy, surface-enhanced Raman spectroscopy (SERS) has extended its applications into the field of point-of-care testing (POCT) and demonstrated its great significance by virtue of its noninvasive property and capability of fingerprint identification. In the SERS-based analysis and/or sensing system, the preparation of a low-cost, high-performance SERS substrate is critically important. In this manuscript, vacuum filtration is utilized to fabricate the silver nanoparticles (AgNPs)-embedded nylon filter membrane (ANFM) as flexible paper-based SERS chips. By characterizing the typical analytes with a miniaturized smartphone-based Raman analyzer, the proposed SERS chips have successfully demonstrated good sensitivity, repeatability, and stability. The lowest concentration as detected can approach 1 pmol for rhodamine 6G (RH6G) and 10 pmol for both crystal violet (CV) and malachite green (MG), respectively. With the help of the microporous structure of the membrane, the ANFM-based SERS chips can implement the separation of small molecules from a complex mixture and can achieve "purified" SERS signals of targeted molecules. Besides, with the function of antifriction resistance and flexibility, the ANFM can serve as SERS papers to preconcentrate the contaminates by multiple swapping and further enhance the SERS signals for point-of-care analysis. Therefore, we demonstrate multifunctions of the flexible ANFM-based SERS chips, which provide a promising solution for the POCT analysis with the SERS technique on account of their flexibility and low fabrication cost.

Nucleic acid detection is of paramount importance in monitoring of microbial pathogens in food safety and infectious disease diagnostic applications. To address these challenges, a rapid, cost-effective label-free technique for nucleic acid detection with minimal instrumentations is highly desired. Here, we present paper microchip to detect and quantify nucleic acid using colorimetric sensing modality. The extracted DNA from food samples of meat as well as microbial pathogens was amplified utilizing loop-mediated isothermal amplification (LAMP). LAMP amplicon was then detected and quantified on a paper microchip fabricated in a cellulose paper and a small wax chamber utilizing crystal violet dye. The affinity of crystal violet dye toward dsDNA and positive signal were identified by changing the color from colorless to purple. Using this method, detection of Sus scrofa (porcine) and Bacillus subtilis (bacteria) DNA was possible at concentrations as low as 1 pg/μL (3.43 × 10 -1 copies/μL) and 10 pg/μL (2.2 × 10 3 copies/μL), respectively. This strategy can be adapted for detection of other DNA samples, with potential for development of a new breed of simple and inexpensive paper microchip at the point-of-need.

The separation and chemical analysis of mixtures in an emergency situation represent major challenges, especially in remote or poverty-stricken areas. A novel method was developed for the rapid separation and detection of multiple components via paper centrifugal chromatography, which costs as little as $2.26 US. The method was realized based on the combination of portable paper centrifugal chromatography and surface-enhanced Raman scattering (SERS) detection. This coupled technique was successfully implemented for the separation and qualitative analysis of a rhodamine 6G-crystal violet mixture and a colorless aniline-pyrocatechol-benzidine mixture. A chromatographic mobile phase was collected using absorbent cotton, which was demonstrated to have no effect on the SERS results. The optimized device achieved rapid and effective separation of the colorless aniline-pyrocatechol-benzidine mixture with a high centrifugal force (0.3303π 2 N). The newly developed method involving multicomponent paper centrifugal chromatography-SERS detection will be of great value for emergency-related substance separation and analysis in remote and poor areas.

Presence of copying pencils in heritage objects poses a significant challenge for conservators due to their proneness to fading, sensitivity to solvents and difficulties in differentiation from regular graphite pencils. In this paper a method of copying pencils identification by means of ATR—FTIR spectroscopy is used. A protocol for spectra processing and dimensionality reduction of spectral data by means of principal component analysis has been developed, allowing for pencil types differentiation and providing an easy to read visual representation of the collected data. The protocol has been developed on mock-up samples and tested on objects from the archives of the State Museum Auschwitz – Birkenau. [ABSTRACT FROM AUTHOR]

Enhancement of latent fingermarks on thermal paper poses a number of problems when using traditional methods used for porous substrates due to blackening of the thermal layer as a result of polar solvents present within the reagents and high temperatures oxidising the acid/dye complex. Thus, methods which prevent such reactions are favoured for the development of latent prints on said substrates. A comparative pseudo-operational trial using UV, Hot Print System (HPS), ninhydrin and ThermaNIN was performed on 1000 thermal paper substrates gathered from various sources. The results indicated that the most effective method was an acetone pre-wash followed by ninhydrin. The sequence of HPS-ninhydrin was similarly effective when compared to ninhydrin as a sole technique. ThermaNIN produced fewer marks than ninhydrin but was superior to HPS. Whilst the HPS developed some fingermarks, there was only a very small number of marks uniquely developed by it. • The Hot Print System (HPS) is inferior to chemical methods on this substrate. • The HPS uniquely developed very few number of fingermarks. • Ninhydrin was the most effective process; however, it compromises text legibility. • The HPS did not adversely affect subsequent chemical development of fingermarks. • ThermaNIN formulation modified to include HFE-71DE to avoid precipitation. [ABSTRACT FROM AUTHOR]

The present study is concerned usage of paper mill sludge (PMS) as an effective adsorbent to remove the two cationic character dyes (Basic Blue 3 [BB3] and Basic Yellow 28 [BY28]) from aqueous solutions. The surface morphology and some characteristics of PMS were determined by Fouirer Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Brunauer Emmett Teller (BET). The parameters affecting the process – temperature (10–55°C), adsorbent dose (0.5–10 g/l), initial pH (2–10 pH), initial concentration (50–250 mg/l) and contact time (0–24 h) – were examined in the batch adsorption experiments. Maximum adsorption capacities (qmax) of two dyes at 1 g/l dose and pH value of 7 were also calculated as 89.35 and 79.81, respectively. Adsorption phenomena of BB3 and BY28 cationic dyes onto PMS is controlled by pseudo-second-order model. Thereafter, equilibrium experimental data were applied to Langmuir, Freundlich and Dubinin–Redushkevich (D-R) isotherms, and Langmuir isotherm is the best represent the equilibrium adsorption process for both dyes. The processes occurred by physical adsorption because of calculated activation values (Ea) of BB3 and BY28 dyes were 19.43 and 9.35 kJ/mol, respectively. In addition, based on thermodynamic calculations such as free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°), the results clearly demonstrated that the adsorption process were of exothermic and spontaneous nature for both dyes. At the light of obtained findings, it can be stated that PMS can be used effectively in removal of cationic dyes from textile wastewaters and is an alternative to commercial adsorbents due to its low-cost and abundance in the paper industries. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman spectroscopy (SERS) is an emerging analytical technique for chemical analysis, which is favourable due to its combination of short measurement time, high sensitivity and molecular specificity. However, the application of SERS is still limited, largely because in real samples the analyte is often present in a complex matrix that contains micro/macro particles that block the probe laser, as well as molecular contaminants that compete for the enhancing surface. Here, we show a simple and scalable spray-deposition technique to fabricate SERS-active paper substrates which combine sample filtration and enhancement in a single material. Unlike previous spray-deposition methods, in which simple colloidal nanoparticles were sprayed onto solid surfaces, here the colloidal nanoparticles are mixed with hydroxyethyl cellulose (HEC) polymer before application. This leads to significantly improved uniformity in the distribution of enhancing particles as the film dries on the substrate surface. Importantly, the polymer matrix also protects the enhancing particles from air-oxidation during storage but releases them to provide SERS enhancement when the film is rehydrated. These SERS-paper substrates are highly active and a model analyte, crystal violet, was detected down to 4 ng in 10 μL of sample with less than 20% point-by-point signal deviation. The filter paper and HEC effectively filter out both interfering micro/macro particles and molecular (protein) contaminants, allowing the SERS-paper substrates to be used for SERS detection of thiram in mud and melamine in the presence of protein down to nanogram levels without sample pre-treatment or purification. [ABSTRACT FROM AUTHOR]

Facile fabrication of flexible substrates containing high concentration of nanoparticles (NPs) is very promising owing to their capability of swab-based surface-enhanced Raman scattering (SERS) trace detection. However, the background signal of the substrate could compromise the trace-detection capabilities. Moreover, the presence of fluorescent molecules may result in intense fluorescence background which could overshadow the Raman peaks. Herein, we demonstrate that the surfactant-free bimetallic (Ag and Au) NPs, synthesized directly on the filter paper, are very effective in reducing the background signal in SERS-based trace detection. Simple soaking of filter paper in a mixture of HAuCl 4 and AgNO 3 solution, and its immediate drying and reduction produces Au-Ag alloy NPs on the filter paper. Interestingly, the substrates are very effective in quenching the background fluorescence of both filter paper and the analyte, thereby effectively detecting the SERS signature of the fluorescent molecules. In particular, Rhodamine6G (R6G) concentrations down to 10−10 M were detected under resonance excitation, both by solution drying and swabbing. The swab detection of ammonium nitrate, which is usually used in homemade explosives, was also demonstrated. Moreover, owing to the fluorescence quenching properties, the Au-Ag alloy substrates (AuAgS) were able to carry out the swab-based multiplex-detection of crystal violet (CV), Brilliant Cresyl Blue (BCB), and R6G upon resonance excitation of R6G. Finally, the substrates have shown good reproducibility, stability, and signal uniformity. This verifies the potential of AuAgS for real-world trace-detection applications. [ABSTRACT FROM AUTHOR]

A disposable surface-enhanced Raman scattering (SERS) substrate was prepared by successively spraying silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) onto commercial filter paper using an inexpensive consumer sprayer. The strong surface enhancement of AgNPs and chemical stability of AuNPs can be advantageously combined. The substrate exhibited excellent SERS activity for malachite green (MG), methylene blue (MB), and crystal violet (CV) under 785-nm excitation, with limits of detection (LODs) of 4.3 × 10−9, 2.0 × 10−8, and 8.1 × 10−8 M, respectively. The substrate exhibited long-term stability, and it can be stored under ambient conditions for 4 weeks with a relative standard deviation of less than 3% among peak intensities. The substrate also showed good reproducibility with a relative standard deviation of 7.1% among different substrate peak intensities. The substrates enable on-site determination of residual fishery drugs and distinguish MG, MB, and CV mixtures in spiked fish within 5 min, and the average recoveries in fish scales and fish meat were better 90.1% and 76.9%, respectively. The method exhibited rapidity, simplicity, and high sensitivity and is expected to be used for the screening of additives in food. [ABSTRACT FROM AUTHOR]

One of the methods to solve the problem of lead metal in water is adsorption. One of the adsorbents that can be used is cellulose because it has an active group that can bind Pb(II). In this study, cellulose from the HVS wastepaper was used as the adsorbent to adsorb the Pb metal. HVS wastepaper was extracted with 10% w/v NaHCO3 and refluxed with 5% w/v Na2HPO4. Cellulose was characterized using Fourier Transforms Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM). Pb(II) adsorption was carried out by the batch method, and it was evaluated using Atomic Absorption Spectrophotometry (AAS) with varying adsorbent mass, concentration, contact time, and pH. FTIR characterization showed that the presence of O - H, C - H, C = O, and C - O groups played a role in the adsorption process. The surface morphology of cellulose from SEM analysis showed form like a fiber shape with agglomerated fine particles. The optimum conditions for adsorption were 0.100 g of adsorbent mass, Pb(II) concentration of 105 ppm, contact time of 10 minutes, and pH of solution 5. An adsorption isotherm model that is preferable for this adsorption process is the Freundlich isotherm model. From the results of this study, HVS paper waste can be used as an adsorbent to handle Pb(II) metal ions to be an alternative as a lowcost adsorbent. [ABSTRACT FROM AUTHOR]

We present a tilted fiber Bragg grating (TFBG) sensor coated with crystal violet/perfluorinated sulfonic acid (CV/Nafion) composite film for relative humidity (RH) monitoring. The composite film demonstrates the characteristics of an optical "humidity test paper" by exhibiting a color transition from yellow to green within a RH range of 10 % to 80 %. This color variation indicates its potential to effectively monitor RH levels in diverse environments. To achieve a quantitative RH sensing, we coat CV/Nafion composite film on an etched TFBG (ETFBG), where surrounding RH changes can be measured from spectral responses of ETFBG transmission. In experiments, the proposed the CV/Nafion-coated ETFBG sensor exhibits RH sensitivities of 0.068 dB/%RH and 3 pm/%RH for intensity change and wavelength shift measurements, respectively, within a relative humidity (RH) range of 10 % to 80 %. Additionally, based on intensity measurement, short response and recovery times of ∼4.4 and ∼4.6 s are estimated from a continuous RH monitoring. • The proposed sensor's color will change from yellow to green with the increasing of the RH. • The proposed sensor could be used for RH detection of liquids, gases, and solids. • High RH detection sensitivity of 0.068 dB/% RH was obtained. • The response and recovery times are 4.4 s and 4.6 s respectively. [ABSTRACT FROM AUTHOR]

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Surface‐enhanced Raman scattering (SERS) substrate is the key to SERS technology and it is still a basic focus to fabricate desirable SERS substrates offering multiple advantages of strong Raman enhancement and good reproducibility and portability. A flexible paper‐based SERS substrate were fabricated involving the use of Au nanocubes (NCs) monolayer. Au NCs were generated with tunable size in the range of 24 to 63 nm through seed‐mediated growth method. The effect of support on SERS properties of Au NCs–assembled monolayer was systemically explored. As a result, more excellent SERS performance could be obtained by assembling Au NCs on the filter paper. Besides, the influence of Au NCs' size on SERS‐enhanced effect of paper‐based substrate was also investigated. Our results clearly indicated that paper‐based substrate with 39 nm Au NCs possessed the optimal SERS enhancement. This SERS substrate exhibited high sensitivity with enhancement factor (EF) up to 9.75 × 107 and demonstrated good uniformity and time stability. Furthermore, based on this superior paper‐based SERS substrate with advantage of powerful sample extraction performance, the measurement of crystal violet (CV) on shell surface were successfully carried out with detection limit down to 2.17 × 10−7 M. And linear quantification were achieved in the range from 5 × 10−5 to 5 × 10−7 M. To sum up, the as‐prepared SERS substrate is applicable for on‐site detection and analysis of CV on various shell surfaces. [ABSTRACT FROM AUTHOR]

Analytical studies of ancient Chinese handmade papers and paper-based materials have long faced challenges, due to the need for high-quality, scientifically sound data that can lead to suitable diagnostic criteria. This study applies Herzberg staining, micro-computed tomography (micro-CT), Raman spectroscopy, pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS), and high-resolution mass spectrometry (HRMS) to five Hetian Administration Banknotes (HABs), a particular type of regional banknotes issued by Ma Hu-shan (1910–1954), a Hui warlord, in southern Xinjiang between 1933 and 1937. The results shed important insights into the use of fiber and dyes on HABs, revealing how locally handmade Sangpi (bark of the mulberry tree, Morus alba L.) papers and imported synthetic dyes (Rhodamine B, Methyl Violet 2B, Direct Black 38, and presumably Sudan II) were combined to serve the needs of the regional economy in southern Xinjiang during the 1930s. We conclude the paper by tentatively proposing guidelines for applying low- and high-resolution analytical methods to understand the manufacture and use of ancient Chinese handmade papers and paper-based materials. [ABSTRACT FROM AUTHOR]

Gamma radiations are known to bring about radiolysis of myriad compounds / dyes which is used to measure of the energy of the incident radiation on the system. The use of various dye solutions for chemical dosimetry is reported in literature. Various thin film dosimeters, semi-conductor dosimeters are also reported and widely used. Similarly ? - dose quantification using paper or polymer impregnated with dyes has also been reported. In the present study, decolouration due to gamma radiation of various dye impregnated papers viz. Gentian Violet (GV), Malachite Blue (MB), Malachite Green (MG), Brilliant Yellow (BY) and Congo Red (CR) has been investigated using device independent colour parameters. The colour analysis was done by standard procedures of Commission Internationale de l'Eclairage CIE. Color has mind dependency so to eliminate the errors in determination colour parameters are evaluated. [ABSTRACT FROM AUTHOR]

Abstract: Triphenylmethanes – Malachite Green (MG), Crystal Violet (CV) and Brilliant Green (BG) are dyes with known genotoxic and carcinogenic properties. Apart from being illegally used in aquaculture for treatment of fish diseases they are also applied in industry such as paper production to colour paper towels widely used in hospitals, factories and other locations for hand drying after washing. The present study provides evidence that the triphenylmethane dye (BG) present in green paper towels can migrate through the skin even when the exposure time is short (30–300s). The transfer of the dye from the towel to food (fish) was also studied and a high amount of colour was found to migrate during overnight exposure. The risk to humans associated with these two dye transfer studies was assessed using a ‘margin of exposure approach’ on the basis of the toxicological data available for the closely related dye MG and its metabolite Leucomalachite Green. The data indicated that the risk associated with the use of triphenylmethane containing paper towels is of a similar proportion to the risk associated with consumption of fish contaminated with these dyes due to the illegal application in aquaculture. [Copyright &y& Elsevier]

In this paper, we have developed a paper-based optical imaging material responding to visible light. This material consists of a thioxanthone (TX) derivative with the additional phenyl carbazole chromophore, namely 1-phenyl-11,12a-dihydrothiochromeno (3,2-b) carbazol-13 (5H)-one (TX-PC), and leuco crystal violet (LCV). TX-PC is newly synthesized and characterized by 1 HNMR, FTIR and high-resolution mass spectrometer. As a visible light absorbing Type II photoinitiator, TX-PC has an excellent absorption property in the visible region in the absence of an added co-initiator. In other words, TX-PC degrades into lively free radicals when irradiating under visible light which resulting in a color reaction on LCV. The degree of reaction is characterized by UV–vis spectrophotometer. In this study, this material is used for imaging within visible light because of the high efficiency color reaction. We coat a paper substrate with this TX-PC/LCV solution and cover with a pattern photomask. Under the irradiation of the visible light, color reaction occurs to irradiated area while the rest remains colorless. Thus the two areas are distinguished to obtain a clear image as same as the original version. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the activity, resistance, clonality of MIC distribution, and the correlation between virulence and resistance genes and biofilm formation of omadacycline (OMC) in clinics for Streptococcus agalactiae isolates from China. 162 isolates were collected retrospectively in China. The S. agalactiae were collected from the body's cervical secretions, wound secretions, ear swabs, secretions, semen, venous blood, cerebrospinal fluid, pee, etc. The MIC of OMC against S. agalactiae was determined by broth microdilution. The inhibition zone diameters of OMC and other common antibiotics were measured using filter paper. D-test was performed to determine the phenotype of cross resistance between erythromycin and clindamycin. In Multilocus sequence typing (MLST), some commonly-detected resistance genes and virulence gene of these S. agalactiae isolates were investigated using polymerase chain reaction (PCR). Biofilms were detected by crystal violet staining. Our data demonstrated the correalation of the biofilm formation and OMA antimicrobial susceptibility of S.agalactiae clinical isolates with the carrier of virulence gene scpB. Conclusively, OMC exhibits the robust antimcirobial activity against clinical S. agalactiae isolates from China compared with DOX or MIN, and the carrier of the virulence gene scpB might correlate with the biofilm formation in OMC-resistant S. agalactiae. [ABSTRACT FROM AUTHOR]

[Display omitted] • Inkjet printing Ag nanoparticles on paper coated with chitosan or N,N, N -trimethyl chitosan to obtain SERS substrates. • Biopolymer coatings not only reduce the rugosity and porosity of the paper but also confer hydrophobicity to the paper. • SERS sensitivity and reproducibility was improved when compared with non-coated counterparts. Paper-based sensors for surface-enhanced Raman scattering (SERS) detection of water pollutants have gained much attention in the last decades. However, most of the fabricated paper-based SERS substrates still face some limitations regarding reproducibility and uniformity. In this work, we report the fabrication of hydrophobic paper-based SERS substrates with high reproducibility and uniformity by inkjet printing Ag colloidal nanoparticles (NPs) on office paper pre-treated with chitosan (CH) or N,N, N -trimethyl chitosan (TMC). We demonstrate that the previous coating of paper with such biopolymers substantially improves the SERS performance of the paper substrates. In screening experiments, crystal violet (CV) 100 μM was used as molecular probe, leading to an increase of about 9- and 7-fold in the observed SERS intensity when the papers were coated with CH and TMC, respectively. Also, the reproducibility of the substrates coated with the biopolymers increased more than 2 times compared to non-coated office paper. We suggest that the improved performance of the coated substrates is related to a more uniform deposition of the AgNPs on the paper surface due to the hydrophobic nature, low porosity and roughness of the coated paper. [ABSTRACT FROM AUTHOR]

The Escherichia coli lon(-) mutants apparently are defective in the ability to recommence cell division after temporary periods of deoxyribonucleic acid (DNA) synthesis inhibition. They are also more susceptible to cell division inhibition by the basic dye, crystal violet (CV), than are lon(+) strains. In enriched broth, the lon(+) strain continued to grow and divide in the presence of CV, but lon(-) cell division was inhibited and filamentous growth resulted. In a supplemented minimal medium containing CV, lon(-) cell division was only temporarily inhibited. There was no detectable specific effect on DNA synthesis, although CV slowed the rate of mass increase in both media. Trichloroacetic acid-insoluble lipid synthesis was preferentially inhibited in both lon(+) and lon(-) strains. In CV-containing enriched broth, diaminopimelic acid incorporation into trichloroacetic acid-insoluble compounds occurred at a rate greater than the rate of mass increase in both lon(+) and lon(-) strains. In a CV-containing supplemented minimal medium, diaminopimelic acid was incorporated to a greater extent by lon(-) cells than by lon(+) cells.

In this work, we have proposed a new approach to study the mechanism of crystal violet (CV) photodegradation on TiO 2 surface using kinetic Monte Carlo simulation. The TiO 2 surface was considered as a set of reactive centers, which is essential in dye photodegradation. A new variable "the effective photon concentration" (I eff ) is defined. A detailed chemical understanding of the photocatalytic reaction is provided. This approach provides a simple and effective method to find the optimal conditions of the studied system. This goal was achieved by investigating the effects of some operational parameters, including initial concentration of CV, pH, loading TiO 2 , light intensity and volume, on the degradation percent, and also, on the effective photon concentration. The perfect agreements between the experimental and simulated data at different conditions confirmed the proposed approach for describing the CV photodestruction. Also, the simulation results indicated that: (1) a significant fraction of the scattered UV irradiation into the reaction vessel does not lead to charge carrier generation; (2) the generation and recombination of charge carriers have crucial roles in the photodegradation. This is the first time that a method based on the reactive centers is employed to investigate the dye degradation by a photocatalyst., (© 2021 American Society for Photobiology.)

• Fabrication of an inkjet-printed paper-based SERS platform. • An effective AuSph Ink was developed with high stability over 1 year of storage. • Improvement of SERS capabilities by a hydrophobic modification of the paper. • Ultrasensitive quantification of thiram at 10−11 M with low sample volume (2 μL). • Reliable, robust and ultralow-cost SERS substrates (less than $ 0.01 per spot). We report the fabrication of a low-cost paper-based SERS platform with enhanced sensing capabilities. The sensor consists of a highly concentrated glycerol/ethanol dispersion of ca. 77 nm Au nanospheres (AuSph) inkjet-printed on hydrophobic chromatographic paper forming circular sensing spots of 1 mm in diameter. The AuSph ink exhibits high stability for 1 year. Interestingly, we demonstrate that the modification of the paper surface with hydrophobic ligands improve the sensing capabilities by confining the analyte solution in the AuSph sensing platform. It contributes to both concentrate the analyte, as well as, to decrease the sample volume to just a few μl. We also analyze the effect of the amount of the nanoparticles, tunable by the number of printing cycles, in the SERS performance of the plasmonic spots. The results show that 5 printing cycles give rise to sensing platforms with great SERS response in terms of intensity and uniformity. The spot-to-spot reproducibility is also analyzed observing good results even for AuSph spots from different printed papers. The paper-based SERS platform was tested towards the detection of crystal violet (CV) and the fungicide thiram. Additionally, applying a digital protocol for SERS analysis, a good linear correlation between the digital counts (or positive events) and the analyte concentration was obtained at the single-molecule SERS regime. In both cases, the quantification region threshold was 10−11 M. The great sensitivity performance of the inkjet-printed SERS substrate is reflected by the low sample volume needed (only 2 μL). The inkjet-printed SERS substrate and the fabrication method demonstrated to be efficient, reliable, reproducible and robust, with a cost less than $ 0.01 per spot. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate a seeded approach for in-situ growth of Ag nanostructures directly on filter paper. Multiple growth steps were used to increase the size of Ag NPs grown from Au seeds. Essentially, this procedure generated a high density of NPs on filter paper which in turn provided high enhancement of Raman signals. We have seen a marked increase in the SERS enhancement factor with each growth step. Moreover, the relative standard deviation (RSD) values decreased with each growth step, indicating the relatively uniform distribution of NPs on the substrate. With four growth steps, we were able to achieve an EF of 9.28 × 104 with RSD values of 14%. In particular, the detection limit of 10 nM for CV has been achieved by both solution drying and swabbing. Moreover, swab detection of explosive material ammonium nitrate down to 100 µM has also been demonstrated. [ABSTRACT FROM AUTHOR]

It is shown that Malachite Green and Crystal Violet immobilized on viscose fabrics can be used as reagents for the rapid determination of selenium(IV) and tellurium(IV). Selenium is determine by the color intensity of ion associates formed by the reagents with the triiodide ion formed upon the reduction of selenium(IV) with potassium iodide and tellurium, by the color intensity of reagent ion associates with telluromolybdic heteropoly acid. The analytical ranges for selenium and tellurium(IV) were 0.005–0.5 and 0.01–0.1 mg/L upon passing 20 and 100 mL of a test solution through the indicator matrix, respectively. The duration of analysis does not exceed 15–20 min. The relative standard deviation is 50%. Test strips were proposed for determining 0.1–100 mg/L selenium(IV) and 1–1000 mg/L tellurium(IV) by the length of the colored zone. The determination of selenium(IV) is based on the oxidation of 4-nitrophenylgydrazine to its diazonium salt and salt interaction with naphthylamine chemically immobilized on paper with the formation of a red azo compound. The determination of tellurium(IV) is based on its reaction with Bismuthol II immobilized on a paper. [ABSTRACT FROM AUTHOR]

As a powerful analytical tool of molecular detection, surface-enhanced Raman spectroscopy (SERS) has attracted great attention in varied fields. However, it has seriously impeded the development of SERS that the preparation process is generally complicated and traditional substrates lack eco-friendliness, economy and flexibility. Herein, we fabricated the inkjet-printed paper-based semiconducting SERS substrates for the first time via an inexpensive office inkjet printer with representative two-dimensional MoO3−x nanosheets ink. Compared with conventional substrates, these paper-based semiconducting substrates not only could meet the requirements of simple and large-scale preparation, but also realize efficient sample collection by merely swabbing the surface. We obtained the detection limit concentration of rhodamine 6G as low as 10–7 M. Furthermore, these flexible paper-based substrates were successfully applied to detect crystal violet and malachite green on the fish surface by swabbing. With immense potentiality in practical applications, the inkjet-printed paper-based semiconducting SERS substrates are expected to open a new prospect for SERS. [ABSTRACT FROM AUTHOR]

The article presents a case in which the patient, an office clerk got an irritant vesicular rash on the palms which spread to the back and sides of her fingers. Her work entailed day-long handling of significant quantities of Carbonless copy paper and carbon paper and operating a visual display unit. Initial patch tests to a standard battery and to carbonless copy paper gave positive allergic reactions to nickel sulphate 5%, cobalt chloride 1% and fragrance mix 8%, but no reaction to the paper handled. Further tests indicated an allergic reaction to crystal violet lactone present in the carbonless copy paper.

In this paper, a NiAl-LDH with the characteristic structure of a hydrotalc-like compound was applied as a carrier in a two-step hydrothermal process, and a MnCdS/In2S3/NiAl-LDH composite material was successfully prepared by loading MnCdS and In2S3 on the flower spherical-like surface of NiAl-LDH. The combination of NiAl-LDH with In2S3 and MnCdS made the band gap smaller and the light absorption range larger, thus increasing the utilization rate of light. 50% MnCdS/In2S3/NiAl-LDH composites had the best photoinduced charge separation and highest surface enrichment of photogenerated electrons. In the degradation experiment of crystal violet (CV), 50% MnCdS/In2S3/NiAl-LDH composites showed superior photocatalytic degradation efficiency (>98.5%) under full spectrum light. Furthermore, the applicability and universality of photocatalysts were studied by observing the degradation of CV by MnCdS/In2S3/NiAl-LDH composites under different conditions. In addition, the composites showed excellent hydrogen production capacity in the photolysis of water, in which hydrogen production within 8 hours was about 7661.51 μmol g−1. By combining the results of active species capture experiments, density functional theory (DFT) calculations and photoelectrochemical experiments, the possible mechanism of double S-scheme heterojunction photocatalysis among NiAl-LDH, In2S3 and MnCdS was inferred, which is one of the main reasons for the enhancement of photocatalytic activity. [ABSTRACT FROM AUTHOR]

Chemical enhancement methods for fingermark in blood deposited on the surface of a thermal paper substrate were examined. The blood-sensitive reagents compared were LCV (leuco crystal violet), Amido black and Hungarian red. Fingermark in blood on the surface of thermal paper can be fixed with 2% 5-sulfosalicylic acid solution. LCV was found as an inadequate blood staining reagent because of bubbling, diffusion, and blurring on the surface of thermal paper. Hungarian red was also an inadequate blood staining reagent because excess Hungarian red on the surface of thermal paper was not washed away in the de-staining procedure. Amido black was the best staining reagent among three staining reagents compared. The maximum dilution ratio visible to the naked eye after Amido black staining was 1 in 80 for the thermally sensitive surface and 1 in 20 for the thermally non-sensitive surface. [ABSTRACT FROM AUTHOR]

Concerned about water treatment, it is of great importance to present new approaches for improving photocatalytic activity. Since photocatalysis is ubiquitous in almost all chemical manufacturing processes, the development of photocatalytic systems carries significance for our environment. In this regard, three different amounts of covalent organic frameworks decorated with titanium(IV) oxide nanoparticles (TiO 2 /COF hybrids) in Alginate-Carboxymethyl cellulose (Alg-CMC) blend matrix were prepared under ultrasound irradiation, which Citric acid and Calcium chloride acted as two green cross-linkages. Based on the physio-chemical analyses of these bio-nanocomposite (bio-NC) beads, the Alg-CMC blend polymer appeared to be the best candidate for a disparity of TiO 2 /COF hybrids. Not only did COF aid to increase the distribution of TiO 2 nanoparticles, but it declined the bandgap energies. The resultant Alg-CMC/TiO 2 /COF (TiO 2 /COF = 15:6) bio-NC beads demonstrated efficient photodegradation activity towards Methyl violet (MV) under Ultraviolet light. The obtained results of scavenger studies indicated that superoxide radicals and electron agents played a major role in MV degradation. Further investigation confirmed that single oxygen addition and N-de-methylation could be two important pathways for the decomposition of MV by these bio-NC beads., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)