Discoloration Process Research Articles

Dual physical stimuli fluorescence response of an α-cyanostilbene derivative for dynamic information storage

α-cyanostilbene derivatives, known as AIE molecules, have the potential to serve as optical recorders and vapor sensor by altering the molecular aggregation and / or stacking models. Despite the significant scientific and technological importance of the correlation between molecular stacking modes and modulated optical properties, relevant research remains scarce. Herein, two thermodynamically stable crystalline phase (BCr and GCr) were found for a biphenyl-based cyanostilbenic compound, DSB-SQ, condensed from its solution. Uniquely, the BCr demonstrated reversible mechanochromism and irreversible thermalchromism, whereas GCr remained unaffected by exposure to light, heat, grinding, etc. The discoloration process was correlated with the variation of local dipole coupling modes during the phase transition, leading to a significant change in π-π overlap and delocalization of excited states. Finally, the BCr was doped with polyvinyl alcohol (PVA) to prepare a composite membrane with dynamic information storage and encryption function.

Screening of Azo-Dye-Degrading Bacteria from Textile Industry Wastewater-Activated Sludge

This study investigates the biodegradation of Reactive Red 141 (RR 141), an azo dye prevalent in the textile industry, by bacteria isolated from activated sludge in a textile effluent treatment plant. RR 141, characterized by nitrogen–nitrogen double bonds (-N=N-), contributes to environmental issues when improperly disposed of in textile effluents, leading to reduced oxygen levels in water bodies, diminished sunlight penetration, and the formation of potentially carcinogenic and mutagenic aromatic amines. This research focuses on identifying bacteria from activated sludge with the potential to decolorize RR 141. Microbiological identification employs MALDI-TOF-MS, known for its precision and rapid identification of environmental bacteria, enhancing treatment efficiency. Results highlight Bacillus thuringiensis and Kosakonia radicincitans as the most promising strains for RR 141 decolorization. Analysis of micro-organisms in activated sludge and database exploration suggests a correlation between these strains and the decolorization process. It is worth noting that this is the first report on the potential use of K. radicincitans for azo dye decolorization. Three distinct culture media—BHI, MSG, and MS—were assessed to investigate their impact on RR 141 decolorization. Notably, BHI and MSG media, incorporating a carbon source, facilitated the bacterial growth of both tested species (B. thuringiensis and K. radicincitans), a phenomenon absent in the MS medium. This observation suggests that the bacteria exhibit limited capability to utilize RR 141 dye as a carbon source, pointing towards the influence of the culture medium on the discoloration process. The study evaluates performance kinetics, decolorization capacity through UV-VIS spectrophotometry, potential degradation pathways via HPLC-MS analysis, phytotoxicity, and enzymatic activity identification. B. thuringiensis and K. radicincitans exhibit potential in decolorizing RR141, with 38% and 26% removal individually in 120 h. As a consortium, they achieved 36% removal in 12 h, primarily through biosorption rather than biodegradation, as indicated by HPLC-MS analyses. In conclusion, the research emphasizes the importance of exploring bacteria from activated sludge to optimize azo dye degradation in textile effluents. B. thuringiensis and K. radicincitans emerge as promising candidates for bioremediation, and the application of MALDI-TOF-MS proves invaluable for rapid and precise bacteria identification.

Interactions between Damaged Hair Keratin and Juglone as a Possible Restoring Agent: A Vibrational and Scanning Electron Microscopy Study.

Juglone, a quinonic compound present in walnut extracts, was proposed as a restoring agent for hair keratin treated with permanent or discoloration processes. The proposed mechanism of restoration by juglone involves the formation of a Michael adduct between the quinone and the thiol moieties of cysteine residues. To this purpose, the first part of the present paper involved the spectroscopic study of the product of the reaction between juglone and N-acetyl-L-cysteine as a model compound. IR spectroscopy and Scanning Electron Microscopy (SEM) monitored the chemical and morphological variations induced by applying juglone to hair keratin. In order to simulate the most common hair treatments (i.e., permanent and discoloration), juglone was applied to hair that had been previously treated with a reducing agent, i.e., methyl thioglycolate (MT) or with bleaching agents (based on hydrogen peroxide and persulfates) followed by sodium hydrogen sulfite. IR spectroscopy allowed us to monitor the formation of Michael adducts between juglone and cysteine residues: the Michael adducts' content was related to the cysteine content of the samples. In fact, MT and sodium hydrogen sulfite favored the reduction of the disulfide bonds and increased the content of free cysteine residues, which can react with juglone. SEM analyses confirmed the trend observed by IR spectroscopy since hair samples treated with juglone adopted a more regular hair surface and more imbricated scales, thus supporting the possible use of juglone as a restoring agent for damaged hair keratins.

Genome-wide association mapping reveals loci for enzymatic discoloration on cut lettuce

Enzymatic discoloration is a major postharvest flaw in cut lettuce, leading to significant food waste. Identifying the genetic determinants and factors associated with this physiological process can facilitate the development of cost-effective and environmentally friendly methods that minimize the loss of product. In this study, a diverse panel of 376 lettuce accessions was investigated for the relationship between enzymatic discoloration and agronomic traits, as well as the genetic characteristics of the discoloration process. The discoloration did not correlate significantly with plant developmental rate, resistance to yellow spot malady, bacteria leaf spot, or downy mildew; but it showed a significant although not strong correlation with the initial levels of brownness (r = −0.146, p < 0.05) and greenness (r = −0.255, p < 0.001) in midribs, and the deterioration rate (r = 0.391, p < 0.001) of fresh-cut lettuce packaged in modified atmosphere. The trait exhibited a relatively high broad-sense heritability (H2 = 0.669) in four trials conducted at three locations in three years. The genome-wide association study (GWAS) revealed the significant effects of six loci (qDis1.1, qDis4.1, qDis6.1, qDis8.1, qDis8.2, and qDis9.1) defined by eight SNP markers. A total of 965 genes were predicted in the identified chromosomal regions, with three quinone oxidation-reduction (redox) enzymes and 19 transcription factors being potentially the most promising candidate genes involved in regulating postharvest discoloration.

Differential Photoaging Effects on Colored Nanoplastics in Aquatic Environments: Physicochemical Properties and Aggregation Kinetics.

Nanoplastics (NPs) have different colors, which could affect their photoaging processes in aquatic environments. This study investigated the effects of irradiation on physicochemical properties and aggregation kinetics of five colored NPs. Photodegradation rates and photooxidation degrees ranked white ≈ yellow > red > blue ≈ black NPs, indicating that NPs with longer color wavelengths photoaged faster. The discoloration process followed color fading (2-14 days, except for white NPs), yellowing (10-16 days), yellow fading (18 days), and turning transparent (20-22 days). White NPs exhibited a different photoaging sequence (C-H → C-OH → C═O → O-C═O) from others. Photodegradation was mainly controlled by singlet oxygen, producing 13 chemicals that were mostly organic acids. The overall colloidal stability of pristine NPs ranked blue > yellow > red > black > white. Irradiation for 16 days retarded aggregation of white and other NPs in NaCl solution, raising the critical coagulation concentration (CCC) by 82.14 and 0.85-7.90%, respectively. Contrarily, irradiation promoted aggregation in CaCl2 solution by reducing the CCC of white (67.37%) and other (33.33-37.58%) NPs. The findings demonstrate that colored NPs underwent photoaging processes different from white/transparent NPs, which were focused by previous work, highlighting the important role of color in their environmental fate and transport.

Multi-Scale X-ray Imaging of the Pigment Discoloration Processes Triggered by Chlorine Compounds in the Upper Basilica of Saint Francis of Assisi.

In this paper, the chromatic alteration of various types of paints, present on mural painting fragments derived from the vaults of The Upper Basilica of Saint Francis of Assisi in Italy (12th-13th century), is studied using synchrotron radiation. Six painted mural fragments, several square centimeters in size, were available for analysis, originating from the ceiling paintings attributed to Cimabue and Giotto; they correspond to originally white, blue/green, and brown/yellow/orange areas showing discoloration. As well as collecting macroscopic X-ray fluorescence and diffraction maps from the entire fragments in the laboratory and at the SOLEIL synchrotron, corresponding paint cross-sections were also analyzed using microscopic X-ray fluorescence and powder diffraction mapping at the PETRA-III synchrotron. Numerous secondary products were observed on the painted surfaces, such as (a) copper tri-hydroxychloride in green/blue areas; (b) corderoite and calomel in vermillion red/cinnabar-rich paints; (c) plattnerite and/or scrutinyite assumed to be oxidation products of (hydro)cerussite (2PbCO3·Pb(OH)2) in the white areas, and (d) the calcium oxalates whewellite and weddellite. An extensive presence of chlorinated metal salts points to the central role of chlorine-containing compounds during the degradation of the 800-year-old paint, leading to, among other things, the formation of the rare mineral cumengeite (21PbCl2·20Cu(OH)2·6H2O).

Electrochemical investigation of a photochromic spiropyran containing a pyrrolidinofullerene moiety

Reversible transformations of a hybrid molecule based on [60]fullerene and a spiropyran moiety under conditions of combined photo- and electrochemical exposure were found. It has been established that the electrochemical oxidation of the UV-photoinduced colored form of the hybrid spiropyran in solution significantly accelerates the discoloration process and does not affect the fullerene part of the hybrid molecule. The research results are promising for designing a photo-electrochromic device that modulates electromagnetic radiation in the visible range of the spectrum.

Promoting the discoloration of PdO in low concentration H2 by using PdAu bimetallic catalyst for eye-readable hydrogen leakage detection

Developing reliable and low-cost optical hydrogen sensors for hydrogen leakage detection at room temperature is extremely important. It requires that hydrogen sensors have a remarkable and rapid color change in low concentration H2/air mixtures, which it is still quite challenging at present. Herein, we demonstrate an eye-readable hydrogen sensor based on Pd-decorated Au@PdO core-shell nanoparticle arrays (Pd-Au@PdO NAs). Pd-Au@PdO NAs show an obvious color change from brownish-yellow to yellow-gray in 1 v/v% H2/air and gray in 4 v/v% H2/air, with ΔE values of 8.1 and 22.5, respectively. Detailed investigation showed that, at the cracks of PdO shell where Au core is exposed, PdAu bimetallic catalyst is generated during the sample-synthesis process. Compared with Pd catalyst, PdAu bimetallic catalyst significantly prompts the reduction of PdO in low concentration H2, represented as a faster discoloration process and more obvious color change. Additionally, the core-shell structure ensures a long-term stability through protecting the PdAu catalyst. We further show that the irreversible sensing performance of Pd-Au@PdO NAs can be reactivated repeatedly, which favors extending the lifetime of the optical sensor and reducing the cost.

Some approximations on the effect of the supporting electrolyte towards electrochemical advanced oxidation degradation of Reactive Orange 84 (RO84)

In this paper, some advanced oxidation electrochemical processes such as anodic oxidation (AO), electro-Fenton (EF), and photoelectro-Fenton (PEF) to carry out the degradation of the azo dye Reactive Orange 84 (RO84) are presented. For this, boron-doped diamond (BDD) electrodes were used, and different configurations were taken in a stirred tank cell, like BDD/graphite and BDD/BDD. The effect of different operating parameters on the discoloration process was evaluated, including the concentration of the supporting electrolyte, namely 50 and 75 mM of Na2SO4, along with 50 mM NaCl and mixtures of Na2SO4 + 25 mM NaCl. The effect of the applied current density at 25, 50, and 100 mA cm−2 over the loss of color was also analyzed using initial RO84 concentrations of 100 and 200 mg/L. The production of free radicals was evaluated in the bulk solution. The decrease in chemical oxygen demand (COD) was determined and the evolution of oxalic acid, a nontoxic, short-chain carboxylic acid was quantified as a final product of all treatments by using ion-exclusion high-performance liquid chromatography.

ELECTROCHEMICAL OZONE GENERATION FOR PALM OIL MILL WASTEWATER TREATMENT USING NICKEL/ANTIMONY DOPED TIN OXIDE ANODES

Ozonation have been employed in organic matter degradation and discoloration process of wastewater. In this study, nickel-antimony doped tin oxide (NATO) anode was employed to generate ozone for palm oil mill effluent (POME) wastewater treatment. NATO was synthesized varying Ni concentrations and calcination temperatures. The materials were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX) and X-ray Photoelectron Spectroscopy (XPS) techniques. All materials showed rutile structure. The electrode displayed a smooth cracked mud surface morphology. Regarding the oxidation state, the binding energies of the Sb 3d3/2 peak were observed at 540.62 eV and 541.51 eV corresponding to Sb3+ and Sb5+, respectively. The key findings show that increasing calcination temperature increases ozone current efficiency obtained from the absorbances of dissolved ozone in liquid phase and current density, which decreases with increasing Ni content. The highest current efficiency and current density (i.e. ca. 30% and 0.18 Acm-2 in 1 M H2SO4 at 2.7V) was achieved at 2%mole ratio Ni content calcined at 650°C. Regarding POME treatment, discoloration and degradation efficiency increased with electrolysis time from the initial chemical oxygen demand (COD) and total organic carbon (TOC) of 1,780 and 96 mgL-1, respectively under the aforementioned conditions. The highest removal efficiency of 80% was achieved within 10 min discoloration and 15 min for TOC and COD. The electrochemical ozone generation using NATO anode have shown high efficiency in the POME treatment due to •OH radicals and O3. NATO is a promising electrocatalyst candidate for wastewater treatment.

An In Vitro Staining Effect of Different Children's Health Drinks on Esthetic Restorative Materials.

To evaluate the staining effect of different children's health drinks (Boost, Complan, and Pediasure) on esthetic restorative materials (giomer, nanohybrid composite, and ormocer). The specimens consist of giomer, nanohybrid composite, and ormocer. Before the discoloration process, 80 disks of each material were fabricated, each measuring 5 mm in diameter and 2 mm in thickness. These disks were then measured for lightness*red/green*blue/yellow (L*a*b*) values. Around 10 samples from each subgroup were then submerged in each of the four staining solutions. Analysis of discoloration levels was done at baseline and 48 hours after immersion in the staining solution. Each specimen's staining effect was evaluated using a spectrophotometer.Each specimen's L*a*b* values were measured three times by placing it on the measurement head. The internal energy (ΔE) unit, which expresses resistance to the staining effect, was derived using each specimen's L*a*b* values. All the tested materials showed a color change. However, giomer showed greater ΔE values compared to nanohybrid composite and ormocer. Of all the immersion media used, Boost samples resulted in the highest color change, followed by Complan, Pediasure, and milk. Out of the three restorative materials used in the study, ormocer showed more resistance to color change than nanohybrid composite and giomer with all the tested media. Ponnala SL, Punithavathy R, Birapu UKC, et al. An In Vitro Staining Effect of Different Children's Health Drinks on Esthetic Restorative Materials. Int J Clin Pediatr Dent 2023;16(2):211-217.

Automation and Optimization of Rat Heart Decellularization Using a Vibrating Fluid Column.

This paper presents the validation of a software application to optimize the discoloration process in simulated hearts and to automate and determine the final moment of decellularization in rat hearts using a vibrating fluid column. The implemented algorithm specifically for the automated verification of a simulated heart's discoloration process was optimized in this study. Initially, we used a latex balloon containing enough dye to reach the opacity of a heart. The complete discoloration process corresponds to complete decellularization. The developed software automatically detects the complete discoloration of a simulated heart. Finally, the process stops automatically. Another goal was to optimize the Langendorff-type experimental apparatus, which is pressure-controlled and equipped with a vibrating fluid column that shortens the decellularization time by mechanically acting directly on cell membranes. Control experiments were performed with the designed experimental device and the vibrating liquid column using different decellularization protocols for hearts taken from rats. In this work, we used a commonly utilized solution based on sodium dodecyl sulfate. Ultraviolet spectrophotometry was used to measure the evolution of the dye concentration in the simulated hearts and, similarly, to determine the concentrations of deoxyribonucleic acid (DNA) and proteins in the rat hearts.

Photocatalytic Degradation of Organic Dyes from Clinical Laboratory Wastewater

Clinical laboratory wastewaters are of important environmental concern due to the highly complex chemical reagents and dyes used to identify various pathologies, which are difficult to degrade by conventional treatment methods. The present research aimed to assess the effects of ilmenite use in the discoloration process of clinical laboratory wastewater. The wastewater originates from a Gram staining process used to identify pathogenic microorganisms present in biological samples. The active ingredient is crystal violet, a triphenylmethane dye derivative, highly toxic and non-biodegradable that causes a shiny purple color in the wastewater. The ilmenite was characterized by X-ray Fluorescence, X-ray Diffraction, Scanning Electron Microscopy, energy-dispersive spectroscopy and Nitrogen adsorption isotherm, while the discoloration process of the wastewater was measured by UV–Vis spectrophotometry and pH change trough the reaction time, evaluating different ilmenite loads, particle size and stability under light sources with different energies. Chemical oxygen demand analysis confirmed that acid formation and discoloration were associated with organic substance mineralization. Type C ultraviolet light and 0.7 g/L load were identified as the best operating conditions for the discoloration process. It was possible to establish that ilmenite is stable after four uses in the discoloration process, obtaining, in all cases, discoloration percentages higher than 90% after 3 h of irradiation.

Rewritable Paper Based on Layered Metal–Organic Frameworks with NIR‐Triggered Reversible Color Switching

AbstractPhotoreversible color‐switching materials, which can reversibly change color in response to external light stimuli, have attracted increasing attention for their applications in time‐sensitive information storage and optical data storage fields. But most of the related materials are dyes or redox compounds with ultraviolet as the light source, dramatically limiting the cycling stability during discoloration processes. To address this problem, a near‐infrared (NIR)‐responsive rewritable paper via doping layered Co‐metal–organic frameworks (MOFs) into the stable polyvinylidene fluoride matrix is reported for the first time. Layered Co‐MOF shows a rapid color‐switching characteristic between orange and black blue upon NIR illumination on/off because of the interlayer spacing changes. Benefiting from the soft network structures of the matrix, Co‐MOF can be homogeneously distributed to deliver an outstanding reversibility performance, including rapid response, coloration in a short period, and decoloration within about 3 min in ambient air. The fabrication of new photoreversible color switching system holds great potential in communication security, which offers a viable pathway to achieve ink‐free photoreversible printing.

Correlation between physical properties and electrochromic performances of DC magnetron sputtered a-WOx thin films

Tungsten oxide thin films were grown on different substrates by the conventional process of direct current magnetron sputtering. A series of amorphous WOx (a-WOx) films, with variable stoichiometry and porosity, were achieved with different total pressure (Pt) induced by oxygen flow rate (Q(O2)) variation. The objective of this study is to determine the couple (Q(O2); Pt) necessary to achieve optimal electrochromic performances of WOx and also study the correlation between physical properties and electrochromic performances. The WOx films optical transmittance evolved from opaque to transparent with the increase of Q(O2). A degradation of films refractive index and the increase of their porosity, both mainly due to the increase of Pt, were observed. The Raman spectroscopy indicated the presence of different W valence states in the as deposited a-WOx films. They all contain W4+, but W6+ were found only into transparent or semi-transparent films. A weak peak of W5+ was observed into the semi-transparent film. Electrical properties studied by Metal-Oxide-Semiconductor structures showed a decrease of the oxide capacitance when Q(O2) and Pt increase. The WOx transparent and optically reversible films, deposited with lower values of (Q(O2); Pt), i.e., Q(O2) = 4.5 sccm and 6 sccm, and Pt = 1.13 Pa and 1.37 Pa, respectively, exhibited the highest values of WOx/Si interface traps average density and positive ions density (Nss). The positive Nss reflects the oxygen deficiency amount in the films. These films were resistive to the discoloration process but showed the highest coloration efficiency CE632nm = 44.4 cm2/C and 42.2, respectively. Their coloration times were tc = 19 s and 22 s, and their discoloration times were td = 180 s and 75 s, respectively. They exhibited the highest optical modulation close to Δ T632nm = 76 %.

A New Insight into the Mechanisms Underlying the Discoloration, Sorption, and Photodegradation of Methylene Blue Solutions with and without BNOx Nanocatalysts.

Methylene blue (MB) is widely used as a test material in photodynamic therapy and photocatalysis. These applications require an accurate determination of the MB concentration as well as the factors affecting the temporal evolution of the MB concentration. Optical absorbance is the most common method used to estimate MB concentration. This paper presents a detailed study of the dependence of the optical absorbance of aqueous methylene blue (MB) solutions in a concentration range of 0.5 to 10 mg·L-1. The nonlinear behavior of optical absorbance as a function of MB concentration is described for the first time. A sharp change in optical absorption is observed in the range of MB concentrations from 3.33 to 4.00 mg·L-1. Based on the analysis of the absorption spectra, it is concluded that this is due to the formation of MB dimers and trimers in the specific concentration range. For the first time, a strong, thermally induced discoloration effect of the MB solution under the influence of visible and sunlight was revealed: the simultaneous illumination and heating of MB solutions from 20 to 80 °C leads to a twofold decrease in the MB concentration in the solution. Exposure to sunlight for 120 min at a temperature of 80 °C led to the discoloration of the MB solution by more than 80%. The thermally induced discoloration of MB solutions should be considered in photocatalytic experiments when tested solutions are not thermally stabilized and heated due to irradiation. We discuss whether MB is a suitable test material for photocatalytic experiments and consider this using the example of a new photocatalytic material-boron oxynitride (BNOx) nanoparticles-with 4.2 and 6.5 at.% of oxygen. It is shown that discoloration is a complex process and includes the following mechanisms: thermally induced MB photodegradation, MB absorption on BNOx NPs, self-sensitizing MB photooxidation, and photocatalytic MB degradation. Careful consideration of all these processes makes it possible to determine the photocatalytic contribution to the discoloration process when using MB as a test material. The photocatalytic activity of BNOx NPs containing 4.2 and 6.5 at.% of oxygen, estimated at ~440 μmol·g-1·h-1. The obtained results are discussed based on the results of DFT calculations considering the effect of MB sorption on its self-sensitizing photooxidation activity. A DFT analysis of the MB sorption capacity with BNOx NPs shows that surface oxygen defects prevent the sorption of MB molecules due to their planar orientation over the BNOx surface. To enhance the sorption capacity, surface oxygen defects should be eliminated.

Application of Biocomposite Films of Chitosan/Natural Active Compounds for Shelf Life Extension of Fresh Poultry Meat

Active packaging based on chitosan (Ch) incorporated with six different natural hydro-alcoholic extracts (HAE) (rosemary, green tea, black tea, ginger, kenaf, and sage) were developed and tested to extend the shelf life of fresh poultry meat. The quality of the meat packaged was assessed through physical-chemical and microbiological characterization over 15 days of refrigerated storage. In vitro antimicrobial activity of pure extracts and films against Gram-positive (B. cereus) and Gram-negative (S. enterica) foodborne bacteria was also addressed. Pure extracts and the films developed showed antimicrobial activity by the diffusion agar method only against the Gram-positive bacteria. Microbial analysis of the meat wrapped with films incorporated with HAE showed a reduction of 3.1–4.5 log CFU/g and 2.5–4.0 log CFU/g on the total viable microorganisms and total coliforms, respectively. Ch + Kenaf and Ch + Sage films presented the highest antimicrobial activity. Regarding the oxidation degradation, as expected, TBARS values increased for all samples over time. However, the meat wrapped in the biocomposites, except for CH + Sage, presented lower secondary oxidation metabolites (reduction of 75–93%) in the content of malonaldehyde. This protection was superior for the meat wrapped with Ch + Rosemary. Active film also showed promising results by retarding the discoloration process and the increase of pH over time. Thus, the biocomposites produced can pose as an alternative technology to enhance the shelf life of fresh poultry meat and maintain its quality.

Surface roughness and color changes of dental PEEK related to staining beverages and cleaning methods

Considering that the microstructure, texture and surface characteristics are relevant factors that could affect the appearance and resistance of a material, the study aims to evaluate in vitro, the surface roughness development and color changes related to staining beverages and cleaning methods after simulated periods of clinical use. The discoloration processes of PEEK materials are caused by intrinsic or extrinsic factors and still require elucidation. Three types of unmodified or modified PEEK CAD/CAD materials were selected for investigation: Finoframe, Juvora medical and BioHPP-a reinforced material. Four different staining media were involved: hot coffee, black tea, cold juice, and distilled water as control. For staining thermal cycling was performed between a hot coffee/tea bath (55 °C) and a bath filled with distilled water (37 °C), respective between a cold juice bath (5 °C) and a bath filled with distilled water (37 °C). For cleaning, a chemical method and mechanical brushing were selected. Simulated periods of clinical use were taken into consideration. Roughness measurements (Ra and Rz) were done after each period. Color changes (ΔE*) were calculated based on the CIE L*a*b* color system. Statistical analyses were performed, paired t-Test for comparisons between the means and Spearman correlations to assess relationships between roughness and color changes. After staining beverages, a significant decreased in Ra values for all three materials that were immersed in juice and, for B and F in tea, were measured. Perceivable changes have been identified for J in coffee and for B in tea. After brushing, Ra significant decreased for J, in all immersion environments and no perceivable color changes were reported. The chemical cleaning caused a significant decrease in surface roughness values for B and F, in all immersion environments and color changes were perceivable for J in juice. Surface characteristics were affected by staining, mechanical and chemical cleaning; during the study, no marked color changes of PEEK were detected.

Batch mode treatment of wastewater from the Maroua artisanal tannery using silica extracted from rice husks and silica/sand mixture

&lt;p&gt;&lt;strong&gt;ABSTRACT.&lt;/strong&gt; Tanning activity consumes high volumes of water resulting in large volumes of highly colored polluted wastewater being discharged to the environment. In this study, the discoloration of the wastewater of the local artisanal tannery using SiO&lt;sub&gt;2&lt;/sub&gt; synthesized from rice husks and silica/sand mixture at different process conditions was investigated. The results revealed that the discoloration process is favorable for both adsorbents at 35&lt;sup&gt;o&lt;/sup&gt;C with maximum of 61% for sand/SiO&lt;sub&gt;2&lt;/sub&gt; mixture system and 64% for SiO&lt;sub&gt;2&lt;/sub&gt; system. The presence of NaCl electrolyte enhanced the discoloration for both adsorbents increasing from 44% for sand/SiO&lt;sub&gt;2&lt;/sub&gt; mixture at 0 NaCl to 72% at 0.5M NaCl and from 49% for SiO&lt;sub&gt;2&lt;/sub&gt; system at 0 NaCl to 63 % at 0.5M NaCl. Increasing the amount of sand from 0.2 to 1 g at fixed SiO&lt;sub&gt;2&lt;/sub&gt; of 0.1 g in sand/SiO&lt;sub&gt;2&lt;/sub&gt; mixture showed discoloration from 40-41 % while increasing SiO&lt;sub&gt;2&lt;/sub&gt; in SiO&lt;sub&gt;2&lt;/sub&gt; alone system from 0.05 to 0.5 g had a discoloration of 45-71%. Results of this study shows that sand a very abundant local and worldwide material can be complemented with silica in a very low cost tannery wastewater discoloration process.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Keywords:&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;Tannery, Wastewater, Silica, Sand, Discoloration&lt;/p&gt;

Pd-decorated PdO nanoparticle nanonetworks: A low-cost eye-readable H2 indicator with reactivation ability

Developing low-cost optical hydrogen sensors for applications in the fields related to hydrogen economy has attracted great attentions, but still remains challenging. Herein, a new type of optical indicator based on Pd-decorated PdO nanoparticle nanonetworks (Pd-PdO NNs) is reported. Pd-PdO NNs have the capability to indicate the presence of hydrogen in concentration range of 0.5% to 100 vol% H2 in air background by a tunable color change. Detailed investigations show the reduction of PdO in H2 is an autocatalytic reaction, and decorated Pd species act as catalysts to accelerate the rate-determining step, so the response time can be dramatically shortened by more than 400 times. The as-prepared H2 indicator does not require expensive detectors, and the discoloration process can be observed conveniently by naked eyes or quantitively analyzed by cameras on smartphones. Moreover, this work highlights the used indicator can be recycled and reactivated repeatedly due to the interconvertibility between Pd and PdO, which opens a new strategy toward extending the sensor lifetime and reducing the cost. As such, Pd-PdO NNs hold the promise to be used as low-cost eye-readable H2 indicators that provide basic sensing services for a broad application scenarios.