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The freshness indicator can detect the freshness of food through characteristic color changes, and has the advantages of high accuracy and visualization. However, existing freshness indicators cannot achieve low-cost mass production. Addressing this challenge, a printed colorimetric freshness indicator which can be used into the modified atmosphere packaging (MAP) of grass carp for freshness monitoring is developed. A printable ink based on natural purple cabbage pigment, carboxymethyl cellulose, and glycerin was prepared, then it was printed in the paper by screen printing and applied to MAP. Additionally, the indicator labels were used in an application trial, which was conducted to monitor the freshness of grass carp under refrigeration (4°C) and at room temperature (25°C). The color response of freshness label was consistent with the spoilage threshold of total volatile basic nitrogen (TVB-N) and trimethylamine (TMA) content in fish sample. Therefore, the paper-sensor label can be used as a simple and practical indicator for freshness monitoring of grass carp.

In order to investigate tunable color materials comprising metallic nanospheres, we investigated the color response of structures formed by periodic arrangements of silver nanoparticles. We use different approaches to model the dielectric function of silver in order to analyze the differences introduced in the reflection and transmission spectra and, consequently, in the obtained color. To calculate the spectral response, we use the KKR method, widely used to model structures comprising layers of periodically arranged spheres. The results obtained show the relevance of the model used for the dielectric function of silver for an accurate prediction of the color produced by systems composed of nanoparticles of different sizes and filling fractions.

Time-temperature indicators (TTIs) are cost-efficient tools that may be used to predict food quality. In this paper, a diffusion TTI was used to predict fruit quality during storage. Both the color changing characters of TTI and the quality parameters, including weight loss, soluble solids content, vitamin C content, titratable acidity, and antioxidant capacity of three kinds of fruits (kiwifruit, strawberry, and mango), were investigated for storage temperatures (5, 10, 15, and 20 °C). The relationships between the color changing properties and fruit quality parameters have been built based on the activation energy (Ea ). The results showed that the storage temperature and time had significant effects on the color changing of TTI and fruit quality. The RGB value of TTI decreased with time, and the higher the storage temperature, the faster the RGB value reduced. Also, the higher the storage temperature, the faster the fruit quality changed and the poorer they were. Furthermore, all of the differences of Ea between TTI color response and fruit quality change are less than 25 kJ/mol, which indicates that the TTI can be used to predict these fruit quality. Finally, prediction models were built and validated based on the RGB values of TTI. It provides the possibility for low-cost quality monitoring and has more application potential in food quality predicting. PRACTICAL APPLICATION: By monitoring the color change of diffuse time-temperature indicator (TTI) and the quality change of fruit, the feasibility of TTI for fruit quality monitoring was determined and the quality prediction model was established. The diffusion TTI and fruit quality prediction model can realize the monitoring and predicting of fruit quality based on the TTI, which provides a basis for the combination of TTI Quick Response Code and fruit quality monitoring, with a view to achieving fruit quality status by scanning the Quick Response Code of TTI with mobile phones in the future. This method may provide a new solution to monitor the fruit quality during storage and distribution based on visualization technology that can simplify the methods of detecting fruit quality and achieve fast quality detection. It provides the possibility for low-cost quality monitoring and has more application potential in food quality predicting. Further studies on diffusion TTI are needed to develop its application in more field of food and make the diffusion TTI an intelligent mean for food quality monitoring and predicting.

A short kanamycin-binding aptamer has been widely used for detecting kanamycin. One of the popular signaling methods is based on the color change of gold nanoparticles (AuNPs) to develop label-free colorimetric biosensors. The general perception was that aptamer binding to its target would inhibit aptamer adsorption by the AuNPs. This inhibited adsorption results in the aggregation of the AuNPs and a color change upon addition of salt. However, the potential adsorption of kanamycin was ignored. Herein, we carefully studied the adsorption of kanamycin on AuNPs and performed a comprehensive analysis using two mutated aptamers and a randomly sequenced DNA which were not supposed to bind kanamycin. In addition, a total of six antibiotics were studied over a wide concentration range. As low as 90 nM kanamycin can induce the aggregation of 3 nM citrate-capped AuNPs, indicating very strong adsorption of kanamycin. The color change was independent of DNA sequence, and all the tested sequences showed a similar color response, regardless of aptamer. Among the different antibiotics, kanamycin and streptomycin induced a color change but not the other four. Our results support an alternative mechanism that kanamycin and streptomycin adsorption by the AuNPs was the main reason for the color change instead of aptamer binding.

Visually identifying pathogens favors rapid diagnosis at the point-of-care testing level. Here, we developed a microenvironment-sensitive aggregation-induced emission luminogen (AIEgen), namely IQ–Cm, for achieving fast discrimination of Gram-negative bacteria, Gram-positive bacteria and fungi by the naked-eye. With a twisted donor–acceptor and multi-rotor structure, IQ–Cm shows twisted intramolecular charge transfer (TICT) and AIE properties with sensitive fluorescence color response to the microenvironment of pathogens. Driven by the intrinsic structural differences of pathogens, IQ–Cm with a cationic isoquinolinium moiety and a membrane-active coumarin unit as the targeting and interacting groups selectively locates in different sites of three pathogens and gives three naked-eye discernible emission colors. Gram-negative bacteria are weak pink, Gram-positive bacteria are orange-red and fungi are bright yellow. Therefore, based on their distinctive fluorescence response, IQ–Cm can directly discriminate the three pathogens at the cell level under a fluorescence microscope. Furthermore, we demonstrated the feasibility of IQ–Cm as a visual probe for fast diagnosis of urinary tract infections, timely monitoring of hospital-acquired infection processes and fast detection of molds in the food field. This simple visualization strategy based on one single AIEgen provides a promising platform for rapid pathogen detection and point-of-care diagnosis., A simple AIEgen with three emission colors achieves rapid identification of Gram-negative bacteria, Gram-positive bacteria and fungi.

The degradation effects of artificial aging on the “true” pigment color of Byzantine iconography are thoroughly investigated in this work. For this purpose, a multi-material palette is fabricated, consisting of various popular egg-tempera pigments, while the original recipes from the literature are utilized in order to mimic the genuine art of Byzantine painters. Then, artificial aging procedures are appropriately employed to simulate environmental fluctuations in historical buildings, such as churches. A total of four time steps are investigated, including the initial condition, and pigments’ spectra in the ultraviolet/visible (UV/Vis) area are acquired in the diffuse reflectance mode at each individual step. Moreover, a color characterization procedure is realized via the quantification of lightness and saturation by means of the measured UV/Vis spectrum. The main objectives of this work are to determine the color stability, the type of color degradation, and generally the color response through time of the studied pigments. The extracted results indicate that a couple of pigments suffer severe color degradation while the majority present moderate darkening or discoloration.

While color-related responses to the Rorschach test have been interpreted as reflecting respondents’ emotional characteristics, their validity has been criticized. Since Rorschach validity should be confirmed by both unconscious and conscious processes, this study focused on implicit positive attitudes toward emotion regulation (considered an unconscious mechanism that motivates regulating emotions) and emotion-regulation strategy. In total, 39 undergraduates (two of whom were excluded from the analyses) completed the Rorschach test, the Implicit Association Test (IAT; measures implicit attitudes toward emotion regulation), and a questionnaire about emotion-regulation strategies. The results showed that positive attitudes toward emotion regulation increased participants’ form-chromatic color (FC) responses, and people who habitually used adaptive strategies to regulate emotions gave more FC responses with high form quality. These results support the interpretation of FC as a mature and controlled emotional response. Additionally, affective ratio (Afr) scores positively correlated with the behavioral suppression of emotions. This result suggests that high Afr, which activates reactivity to Rorschach color cards, can be interpreted as emotional excitement caused by the dysfunction of emotion regulation.

In this study, three minerals were chosen as the host of colorimetric humidity sensor, and Bromothymol blue (BTB) was used as the indicator. The BTB based on titanium dioxide (BTB-TiO2), BTB based on palygorskite (BTB-palygorskite) and BTB based on mullite (BTB-mullite) exhibited the readable response to the relative humidity (RH) of 11, 43 and 75% at 1 min at 25 °C. Moreover, the BTB-palygorskite exhibited the rapid and stable color response, especially under the low humidity (11% RH). The surface area played an important role on the cover density of BTB and water adsorption which made the humidity sensor with excellent performances.

It is great significance to develop an effective eye-readable gas detection technology that would be safe, low-cost, and highly sensitive, serving as a vital complement to traditional H2 sensors. In this work, a class of flexible MoO3 nanowire labels (NWLs) modified with Pd nanoparticles have been successfully developed and studied as eye-readable hydrogen indicators at room-temperature. The nanowire labels turn from white to blue-gray even at a very low concentration (0.1%), where the eye-readable color change takes place in 65 s, and the color changes gradually from white to blue-gray. The reaction of MoO3 nanowire label with hydrogen is of high sensitivity, fast response and time-resolved. The process can be divided into two stages, i.e., fast and slow responses, which are dominated by H2 concentration and intrinsic properties of Pd MoO3, respectively. The color response is also reversible by annealing under air ambient at 200 °C for 2 h, and selective to hydrogen compared with other flammable gases (i.e., CO, CH3CH2OH, CH3OH). The gasochromic NWLs involve Pd-catalyzed reduction of MoO3 in the presence of hydrogen. They also exhibit the superior advantage of being flexible, which have promises applications in efficient eye-readable hydrogen detection.

The application of a colorimetric indicator for monitoring the degree of fermentation in Kimchi was studied. Changes in total color difference (TCD) occurred continuously from the initial to final fermentation stage with a maximum TCD value of 36.08 ± 0.72 after 28 days. The experimental data for the converted color response function, F(Xc) were demonstrated to be more linear (R2 = 0.986) than for TCD values. The coefficients of determination of pH: F(Xc) (R2 = 0.9583) and titratable acidity: F(Xc) (R2 = 0.9828) were sufficient to meet the zero-order reaction. Results of standardized residuals evidenced their normal distribution, indicating that 95% of the residuals of predicted pH or titratable acidity were in the range of −1.96 to 1.96. The coefficients of determination between predicted- and observed data were 0.841 (pH) and 0.912 (titratable acidity). Based on regression analysis, the colorimetric indicator could thus be applied as a Kimchi fermentation indicator.

8.8 MT of food wastes are annually generated in the EU, in part due to the lack of real-time food freshness information provided by current food data labels. To address this issue, intelligent packaging strategies are being developed. In this study, in search of new natural and food grade pH-indicators, color stability and variability of curcumin (E−100), betanin (E−162), and anthocyanin (E−163) containing food colorants were studied in solution under different food storage conditions and pHs by light absorbance, color, pH and turbidity measurements. E−100 provided color variations (yellow/brown-yellow) at pH > 9 and was particularly photosensitive since a color loss of 67% was observed after 1 day of storage. E−162 and E−163 colorants, however, were thermosensitive and showed significant lower loss of color (30%) after 28 days of storage. E−163, especially, presented a broader color response (red-purple-blue-green) over a wider pH range. Furthermore, color variations at different pHs were dependent upon colorant type and concentration. A.E. thanks the Ministry of Science, Innovation and Universities (Juan de la Cierva contract).

In this study, effects of control parameters (protein type, hydrocolloid concentration, hydrocolloid type and mixing temperature) on density response of model foams and color response of model foam halvas. Signal/Noise ratio for the lowest density and the highest L* values were obtained using Taguchi L16 experimental design (44). As a result of the analysis, model foam obtained by mixing solution containing whey protein isolate (0.5%), saponin (0.096%) and pectin (0.05%) at 80oC was determined as the best foaming sample. For density response, Signal/Noise ratio of this sample (13.98 dB) was also detected higher than control (11.49 dB). There was no significant difference between the model foam halva produced by whipping the solution (whey protein isolate (0.5%), saponin (0.096%) and xanthan gam (0.1%)) at 40oC and traditional method. Consequently, it was determined that model foams/foam halvas with reduced saponin content and targeted density and color could be produced using Taguchi method., Bu çalışmada; kontrol parametrelerinin (protein çeşidi, hidrokolloid konsantrasyonu, hidrokolloid çeşidi ve çırpma sıcaklığı) model köpüklerin yoğunluklarına ve köpük helvaların renklerine etkileri Taguchi yöntemi kullanılarak belirlenmiştir. En düşük yoğunluk ve en yüksek L* değerleri için Sinyal/Gürültü oranları Taguchi L16 deney tasarımı (44) kullanılarak saptanmıştır. Analiz sonuçlarına göre; peynir altı suyu protein izolatı (%0.5), saponin (%0.096) ve pektin (%0.05) çözeltisinin 80 oC’de çırpılmasıyla elde edilen model köpüğün en iyi köpürebilen örnek olduğu belirlenmiştir. Ayrıca, bu örneğin yoğunluk yanıtı Sinyal/Gürültü oranının (13.98 dB) kontrolden (11.49 dB) daha yüksek olduğu tespit edilmiştir. Peynir altı suyu protein izolatı (%0.5), saponin (%0.096) ve ksantan gam (%0.1) ile hazırlanan çözeltinin 40 oC’de çırpılmasıyla üretilen model köpük helva ve geleneksel yöntemle üretilen helvanın parlaklıkları arasında istatistiksel açıdan önemli fark bulunmamıştır. Sonuç olarak; saponin içeriği azaltılmış, hedeflenen yoğunlukta ve renkte köpüklerin/köpük helvaların üretilebileceği Taguchi optimizasyon yöntemiyle belirlenmiştir.

The Zn(II) MOF with a tripyridinium-based hexacarboxylate shows direct color change on exposure to small primary amines and UV-assisted color response on exposure to small alcohols. The reversible, group-specific and size-selective chemochromic/chemophotochromic behaviours are ascribed to spontaneous/photoinduced guest-to-host electron transfer within the unique confined space furnished with electron-deficient sites.

The color viewing angles of diffractive-plasmonic reflective color filters are assessed using BFP microscopy images and numerical simulations. The results indicate an asymmetric color response useful for data privacy enhancement in display applications.

As described in Chap. 11, color is crucial in many specialisms within clinical photography, particularly those where the colors form some of the diagnostic criteria. In that chapter, color was introduced as a concept, in the context of the color response of the human visual system, the need for color management to standardize colors within imaging chains, and the difference in the balance of requirements of color accuracy and color consistency in different imaging scenarios.

The method of monitoring the freshness of seafood is not satisfactory for ensuring food safety. Here, we develop a filter membrane-based smart fluorescent tag with excellent biogenic amine response, which can monitor the freshness of seafood in real time and visually. We use green fluorescent fluorescein as an indicator and red fluorescent carbon quantum dots (RQDs) with aggregation-induced emission property as an internal reference. After simple mixing, they are deposited on the commercial filter membrane by physical deposition method to prepare the fluorescent tag. When amine molecules are present, the molecular conformation of fluorescein changes and the fluorescence increases rapidly, while RQDs have no obvious response, thus achieving a clear fluorescence color response to biogenic amines. Under UV light of 254 nm and 365 nm, the fluorescent tag showed sensitive, rapid, and color-responsive to ammonia in a wide range of 250–2.5 × 104 ppm. To further verify the practical application potential, the fluorescent tag was used to monitor the freshness of shrimp and crab in situ in real time, and satisfactory results were achieved. More importantly, owing to the reversible conformational change of fluorescein, the fluorescent tag can be reused and manufactured at low cost, making it a more attractive platform for freshness monitoring in the field of food safety.

A new sensitive sensor for Zn2+ based on diarylethene with an imidazole unit has been synthesized. Its photochromic and fluorescent behaviors have been systematically investigated by the stimulation of UV/vis lights and Zn2+ ion in THF solution. It displayed a dual-mode with a “turn on” fluorescence and color response to Zn2+. With the addition of Zn2+, the emission intensity enhanced 26-fold, accompanied by the fluorescent color changed from dark red to bright yellow. The 1:1 stoichiometry between the sensor and Zn2+ was verified by Job's plot and MS. The LOD for Zn2+ was determined to be 6.12 × 10−9 mol L−1. Furthermore, a logic circuit was designed by using the fluorescence at 578 nm as output and the combinational stimuli of UV/vis and Zn2+/EDTA as inputs.

A novel fluorescent probe 3′-hydroxy-3-oxo-3H-spiro [isobenzofuran-1,9′-xanthene]-6′-yl-2,4-dinitrobenzenesulfonate (probe 1) was designed and synthesized as a visual sensor for the detection of cysteine levels in milk and water samples. The addition of cysteine to the solution of probe 1 resulted in an increase in fluorescence intensity and color change, from light yellow to yellow-green. The distinct color response indicated that probe 1 could be used as a visual sensor for cysteine. Cysteine can be detected quantitatively at concentrations between 0 and 400 μM and the detection limit of the fluorescence response to the probe was 6.5 μM. This suggests that probe 1 could be used as a signaling tool to determine the cysteine levels in samples, such as milk and water.

A new highly selective and visible colorimetric fluorescent probe (probe 1) was developed to detect hydrazine (N2H4) concentration in real water samples. As different concentrations of N2H4 were added, the color of the probe solution was graded gradually from colorless to pink, which could be observed by the naked eye under UV light at 365 nm. Our research indicates that probe 1 offers a certain practical significance for use as a visible detection agent to detect N2H4 efficiently by distinct color response. Furthermore, our work showed that probe 1 can be successfully applied to detect N2H4 concentrations in real water samples.

An optical sulfonamides sensor is fabricated based on a molecular imprinted resin templated by nanocrystalline cellulose. A chiral nematic imprinted composite film is synthesized which is subsequently treated with removal of templates to generate a red reflecting photonic film. The film shows a naked-eye color response to sulfanilamide, which is related to reassemble imprinted sites in the chiral nematic structure, resulting in a yellow reflecting film. Upon exposure to various antibiotics, it can be simultaneously in selectively response to three sulfonamides. This strategy facilitates enormously potential application of the resin as battery-free and portative optical monitoring sensors.

Metasurfaces provide applications for a variety of flat elements and devices due to the ability to modulate light with subwavelength structures. The working principle meanwhile gives rise to the crucial problem and challenge to protect the metasurface from dust or clean the unavoidable contaminants during daily usage. Here, taking advantage of the intelligent bioinspired surfaces which exhibit self-cleaning properties, a versatile dielectric metasurface benefiting from the obtained superhydrophilic or quasi-superhydrophobic states is shown. The design is realized by embedding the metasurface inside a large area of wettability supporting structures, which is highly efficient in fabrication, and achieves both optical and wettability functionality at the same time. The superhydrophilic state enables an enhanced optical response with water, while the quasi-superhydrophobic state imparts the fragile antennas an ability to self-clean dust contamination. Furthermore, the metasurface can be easily switched and repeated between these two wettability or functional states by appropriate treatments in a repeatable way, without degrading the optical performance. The proposed design strategy will bring new opportunities to smart metasurfaces with improved optical performance, versatility, and physical stability.

Mycotoxin contamination of food and feed is a significant health hazard in humid areas of the world. Fungal development can be halted if the water activity of dried products is kept below 0.65. This preliminary study evaluates the color response and response time of a low-cost humidity indicator that estimates water activity. The DryCard TM has a consistent color response to relative humidity and its response time is fast enough to be used in practical situations for estimating water activity. The card comes with use instructions and it can be reused many times. It is a crucial tool to assist smallholder farmers and traders in ensuring their crops have been adequately dried.

Precise monitoring of pesticide with portable device was challenging because it required high sensitivity, short response time, strong stability and excellent selectivity. Herein, we newly constructed a stimuli-responsive hydrogel (SRHg)-based portable kit by embedding copper nanoparticles (CuNPs) in agarose hydrogel. In this work, dimethoate as inhibitor of urease restrained the generation of ammonia, which reduced in-situ etching of CuNPs, resulting in the fluorescence color response of test kit under ultraviolet illumination. Interestingly, by means of smartphone-based nanocolorimetry, the photo image of portable kit could be translated into digital information using ImageJ software, achieving a direct quantitative tool for dimethoate identification. The simplicity of SRHg-based portable kit combined with smartphone-based color recognition not only improved the analysis sensitivity (detection limit of 1.0 μg L−1), accuracy and stability, but also simplified operation process and shortened sample-to-answer analysis time (55 min), demonstrating that the methodology met the needs of daily testing and provided a new sight for on-site monitoring of food safety and human health.

26th International Mining Congress and Exhibition of Turkey, IMCET 2019, 16 April 2019 through 19 April 2019, , 151960 Quartz beneficiation has been applied to meet market requirements by physical and/or chemical methods. Chemical beneficiation has long been investigated by inorganic (e.g. sulfuric acid) and organic (e.g. oxalic acid) acids. Oxalic acid bleaching of quartz ore has taken great interest. This work was conducted to investigate the relationship between metal (Fe, Al, Mg) rejection rates and color responses of bleached quartz ore. Bleaching tests were conducted in agitated pulp condition at different oxalic acid concentrations (0.01M, 0.04M, 0.1M and 0.4M) and temperatures (80°C, 90°C and 95°C) for 90 min. Efficiency of process was measured by colorimetric analysis applied on bleached quartz and chemical analysis (ICP-MS) applied on metal loaded leach liquor. Experimental results revealed that mineralogical composition of ore affected the oxalic acid bleaching of quartz ore. Whiteness could considerably be increased, and yellowness was decreased by manipulating the leaching temperature and acid concentration. But, proportional improvement in the redness could not be achieved possible due to presence of insufficiently leached free dark colored particles in addition to the necessity to apply oxidizing potential in strongly acid environment. Copyright © IMCET 2019 International Mining Congress and Exhibition of Turkey. All rights reserved.

A new efficient and practical fluorescent probe 6-(benzo[d]thiazol-2-yl)naphthalen-2-yl-thiophene-2-carboxylate (probe 1) was synthesized to detect hydrogen sulfide (H2S). The addition of H2S caused the solution of probe 1 to change from colorless to yellow, and the solution of probe 1 changes to different colors with respect to different concentrations of H2S. Importantly, probe 1 could help detect H2S efficiently by a distinct color response as a visible detection agent. Probe 1 reacted with various concentrations of H2S (0–200 μM), and the detection limit for H2S was 0.10 μM. Particularly, probe 1 can be applied as a sensor to detect H2S accurately in wine samples.

Luminescent materials are one of the most fascinating candidates for the field of data communication and information security because of their special optical characteristics. Unfortunately, unimodal output of luminescent performance reaches unsatisfied security of anti-counterfeiting. Hence, achieving multicolor, multitemporal, and multimodal luminescence performance simultaneously is still a fascinating target, especially in a single host. Here, multi-model optical output is realized for the multiple emission centers of CaAl2Si2O8 doped with Eu3+/Eu2+ ions. Moreover, a successive defect structure is constructed via the introduction of Nd3+ ions, which enables the thermo-/photon- responded luminescence properties. Herein, an efficient three-path authenticating model that performs a dynamic multiple color response and stimulated-sources dependent emission is accomplished in the CaAl2Si2O8 host matrix. The explored multichannel approach offers a unique insight for designing advanced anti-counterfeiting technology.

Television and cinema displays are both trending toward greater ranges and saturation of reproduced colors, which are made possible by near-monochromatic illumination technologies. Through current broadcast and digital cinema standards work, system designs employing laser light sources, narrowband light-emitting diodes, quantum dots, and others are being actively endorsed in promotion of a wide color gamut. However, spectrally selective excitations of naturally different human color response functions exacerbate variability of observer experience. Furthermore, singular “standard observer” summaries of human color vision, such as those found in the International Commission on Illumination (CIE)'s 1931 and 1964 color-matching functions and extensively used in motion picture color management, are deficient in recognizing expected human vision variability. Many researchers have confirmed the magnitude of observer metamerism in color matching, but few have shown explicit color management with an aim of minimized observer perception variability. This paper shows that not only can observer metamerism influences be quantitatively predicted and confirmed psychophysically but that intentionally engineered multiprimary displays employing more than three primaries can also offer an increased color gamut with drastically improved consistency of experience.

Oxalate is commonly employed as adjuvant of pesticide agent, causing renal injury of human even in trace residues. Despite the great achievements of the existing point-of-care testing (POCT) technology, accurate on-site screening of oxalate remains a tricky issue. To this aim, we proposed a “lab in a tube” platform which integrated portable hydrogel kit with smartphone for real-time monitoring of oxalate to achieve quantitatively precise analysis. In this work, a stimuli-responsive hydrogel-based kit was constructed via embedding manganese dioxide (MnO2) nanosheets into sodium alginate hydrogel system. Based on the intrinsic oxidase-like activity, MnO2 nanosheets-based nanozyme triggered color reaction by introducing a common sensing probe 3,3′,5,5′-tetramethylbenzidine. Meanwhile, the presence of oxalate would decompose MnO2 nanosheets, inducing the decrease of nanozyme activity, which resulted in the color response of portable kit. Coupling with ImageJ software, the image information of kit captured via smartphone could be transduced into the hue intensity, which provided a directly quantitative tool to detect oxalate with a detection limit of 8.0 μmol L−1. This portable smartphone biosensor was successfully applied for screening urine sample within 10 min for high-throughput analysis (twelve samples) without the need for any advanced analytical instruments. Based on the merits of simple operation, cost-efficiency, and good selectivity, the availability of the miniaturized biosensor platform for POCT will achieve the requirements of routine screening and disease prevention.

Foodborne bacterial infection poses a serious threat to human health. As most diseases are caused by living bacteria, real-time assessment of bacterial viability is vitally important to the public health sector. Herein, we developed a simple and novel colorimetric assay based on the Glucose oxidase (GOD)/Horseradish peroxidase (HRP) bienzyme system for real-time monitoring of bacterial viability in food and drinking water. This bienzyme system is free of any chemical synthesis and only requires 3 sample handling steps. The color response is easily observable with the naked eye or recordable with a smartphone for precise determination of bacterial viability. The proposed strategy was validated with various bacteria both Gram-positive and Gram-negative, indicating its capability for broad-spectrum bacteria viability detection. Therefore, the proposed strategy shows promise for rapid and reliable quality control in food and drinking water.

A new fluorescent probe made from (E)-2-(benzo[d]thiazol-2-yl)-3-(6-hydroxynaphthalen-2-yl) acrylonitrile (Probe 1) was synthesized for the determination of bisulfite concentrations in real food samples (red wine and sugar). Adding bisulfite to a Probe 1 solution caused a marked decrease in fluorescence intensity and a visual color change from yellow to light yellow. This distinct color response indicates that Probe 1 could be used as a visual sensor for bisulfite. Probe 1 can detect bisulfite quantitatively in the range 0–400 μM with a detection limit of 0.10 μM. This makes Probe 1 a convenient signaling instrument for determining bisulfite levels in sugar and red wine samples. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s10068-019-00571-2) contains supplementary material, which is available to authorized users.

A new colorimetric film using natural dye for detection of ammonia gas was developed and investigated. The natural dye was extracted from Syzygium oleana fruit (ESO). For developing the colorimetric films, the extracted dye was immobilized in chitosan/nanocellulose (CH/NC) films. Color of the natural dye extract was observed to change from reddish purple to purple by the influence of pH ranges from 7-11. Scanning Electron Microscopy (SEM) was used to characterize the CH/NC/ESO films. The results showed that ESO can be combined with CH/NC. Color response of the films toward ammonia gas was evaluated. It was found that the color of the films changes from brownish violet to light yellowish brown after contact with ammonia gas. This result indicates that the CH/NC/ESO films can detect ammonia gas by the way of its color change. The advantages of this colorimetric films are simple, cheap, environmentally friendly, and can be candidate for a label detection of meat spoilage.