Color Of Solution Research Articles

Rapid and practical colorimetric biosensor for leishmaniasis diseases

In this article, a colorimetric biosensor for detection of Leishmania major surface protease (Gp63) antibody (anti-gp63) was developed by using gold nanoparticle (AuNP) as a color reagent. The dispersion or aggregation of AuNPs leads to a distinct and sensitive change in UV-vis spectra and solution color. For this purpose, kinetoplastid membrane protein-11 (KMP-11) was labeled with AuNPs surface directly. After that, Gp63 antibody was added in the KMP-11@AuNP solution and a color change from red/pink to purple/violet was observed. As a result, anti-gp63 solution diluted at a ratio of 1:640 can be detected with the developed colorimetric leishmania biosensor. The relative standard deviation value for 1:320 diluted anti-gp63 was calculated as 1.29 %. Furthermore, the linear range of the developed colorimetric biosensor was determined as 1:80 to 1:640. Moreover, developed Leishmania biosensor was applied for detection of leishmania parasite crude antigen and rabbit serum which were used as positive and negative samples respectively. As a result, the recovery values for the measurements of aforementioned samples were calculated as 95.3 % ± 0.02, 103.1 % ± 0.02, 96.2 % ± 0.01 and 95.5 % ± 0.03 for dilutions of 1:200, 1:160, 1:320 and 1:640 anti-gp63 solutions respectively.

On-Site Quantitative Visualization of Singlet Oxygen in Crops via an Organic Small Molecule-Based Ratiometric Fluorescent Probe and a Mobile Fluorescence Analysis Device.

Singlet oxygen (1O2) plays imperative roles in a variety of biotic or abiotic stresses in crops. The change of its concentration within a crop is closely related to the crop growth and development. Accordingly, there is an urgent need to develop an efficient analytical method for on-site quantitative detection of 1O2 in crops. Here, we judiciously constructed a novel ratiometric fluorescent probe, SX-2, for the detection of 1O2 in crops. Upon treating with 1O2, probe SX-2 displayed highly selective ratiometric fluorescence response, which is favorable for the quantitative detection of 1O2. Concurrently, the fluorescence solution color of probe SX-2 was varied, obviously from blue to yellow, indicating that the probe is beneficial for on-site detection by the naked eye. Sensing reaction mechanism studies showed that the 2,3-diphenyl imidazole group in SX-2 could function as a new selective recognition group for 1O2. Probe SX-2 was utilized for the detection of photoirradiation-induced 1O2 and endogenous 1O2 in living cells. The changes in the 1O2 level in zebrafish were also tracked by fluorescence imaging. In addition, the production of 1O2 in crop leaves under a light source of different wavelengths was studied. The results demonstrated more 1O2 were produced under a light source of 365 nm. Furthermore, to achieve on-site quantitative detection, a mobile fluorescence analysis device has been made. Probe SX-2 and mobile fluorescence analysis device were capable of on-site quantitative detecting of 1O2 in crops. The method developed herein will be convenient for the on-site quantitative measurement of 1O2 in distinct crops.

A Naked-Eye Colorimetric Ratio Method for the Selective and Sensitive Detection of L-Cys Based on a Silver Nanoflakes–Chromium (III) Ion System

As a necessary sulfhydryl amino acid, L-cysteine (L-Cys) maintains many physiological functions in the biological system. However, abnormal L-Cys levels can cause a variety of diseases. In our work, a highly sensitive and selective assay has been developed for sensing L-Cys using the morphological transformation of silver-based materials induced by Cr3+. In this sensing system, Cr3+ could etch the silver nanoflakes into silver nanoparticles, accompanied by a change in absorbance, which decreases at 395 nm, creates a new peak at 538 nm, and keeps increasing the absorbance with the addition of Cr3+ concentration. Meanwhile, under the naked eye, the solution color changes from bright yellow to dark purple. Because of the strong affinity between L-Cys and Cr3+, L-Cys could inhibit the induction of Cr3+ on silver-based materials, thereby preventing changes in the configuration, absorption spectrum, and color of silver-based materials. Taking advantage of this point, we can quantitatively detect the concentration of L-Cys. A linear relationship between the absorbance ratio (A538 nm/A395 nm) and L-Cys concentration was found in the range of 0.1–0.9 μM, and the detection limit was 41.2 nM. The strategy was applied to measure L-Cys spiked in beer and urine samples, with recovery from 93.80 to 104.03% and 93.33% to 107.14% and RSD from 0.89 to 2.40% and 1.80% to 6.78%, respectively. This detection strategy demonstrates excellent selectivity and sensitivity, which makes it a practical and effective method for the detection of L-Cys in real samples.

Gold nanoparticles assisted colorimetric sensing of paroxetine, duloxetine, and olanzapine in aqueous and micellar systems with improved sensitivity

The present study explored a rapid and facile colorimetric identification of two antidepressants (paroxetine and duloxetine) and one antipsychotic drug (olanzapine) in aqueous and micellar systems using citrate-stabilized gold nanoparticles (Cit-AuNPs). The sensing approach involved hydrogen bonding and electrostatic interactions on the surface of Cit-AuNPs. The attributes of Cit-AuNPs and their interactions with the drugs were probed using characterization techniques like UV–Vis spectroscopy, scanning electron microscopy (SEM), dynamic light scattering (DLS), zeta potential measurement, and Fourier-transform infrared spectroscopy (FT-IR). Various factors including the volume of Cit-AuNPs, pH, reaction time, surfactant concentration, and the sequence of addition of reagents were optimized to inspect their impacts on sensing results. Under optimized conditions, the probe showed good linearity for the three drugs at the nanomolar (nM) range. Consequently, the color of the Cit-AuNP solution transformed from red to royal purple and blue, which was visible to the naked eye and monitored by visible absorption spectra. This label-free optical detection approach could recognize paroxetine (Prx), duloxetine (Dlx), and olanzapine (Olz) in aqueous system at concentrations ranging from 1 to 17 nM with a limit of detection (LOD) of 0.312, 0.258, and 0.418 nM (S/N = 3), respectively. Meanwhile, the sensitivity was improved in the Triton X-100 (TX-100) micellar system with LOD of 0.029, 0.030, and 0.029 nM for Prx, Dlx, and Olz, respectively accompanied by a shift in the absorption bands. The micellar system contributes stability to the Cit-AuNP-drug complex. The devised colorimetric approach was convenient and did not require any complex equipment. It was efficaciously used to detect three drugs in pharmaceutical products, spiked human urine, and blood serum samples with satisfactory recoveries of 99.83–103.45% and RSD < 3.5%. Notably, the sensing assay demonstrated good selectivity for three drugs in the existence of commonly encountered foreign species and certain common drugs with a relative error below 3%. The results of the present study were statistically compared with reference methodology. The results were validated with no significant difference between the devised and reported approaches considering precision and accuracy, respectively.

Bimetallic CuFe Prussian Blue Analogue Nanocubes as a Colorimetric Probe for the Quantification of Glutathione

Label-free bimetallic CuFe Prussian blue analogue nanocubes (CuFe PBA NCs) were directly employed as colorimetric probes for the visual determination of glutathione (GSH). CuFe PBA NCs produce an absorption peak at 400 nm. In the presence of GSH, the CuFe PBA NCs were transformed into larger hollow nanospheres based on the acid-initiated Kirkendall effect, leading to the appearance of a new peak at 520 nm and a solution color change from yellow to red. Thus, the GSH-induced color changes allowed the establishment of a double-signal colorimetric assay for GSH using the ratio of absorbance at 520 and 400 nm (Δ(A520/A400)). Facile determination of GSH from 0.1 to 8 μM with satisfactory specificity was developed, providing a detection limit as low as 0.08 μM. Additionally, GSH concentrations exceeding 3 μM can be directly identified by the naked eye. The colorimetric assay for GSH has also been demonstrated to have application for serum analysis. Compared with conventional single-signal colorimetric determination, the ratiometric probe was demonstrated to provide good selectivity and high sensitivity.

Sustainable and fast synthesis of zinc-phthalocyanine for gamma radiation dosimeter application

In the present research, the two different systems of dye based on zinc phthalocyanine were prepared by microwave-induced synthesis and conventional methods. They were evaluated as new effective chemical-based dosimeters for gamma irradiation. The sensitivity of the prepared dosimeters was examined by studying the comparative results between them through the changes in structural and optical properties upon exposure to different gamma irradiation doses. The color bleaching of the solutions was followed spectrophotometrically. Gradual changes from blue to light yellow color of zinc phthalocyanine solution, with the increase of the gamma radiation dose, were observed due to the decomposition of the dyes based on the zinc phthalocyanine. The synthesized zinc phthalocyanine chemical-based dosimeters for measurement of gamma irradiation up to 25kGy showed excellent stability after irradiation in terms of morphology and structure, which makes them a suitable novel material as composite-based dosimeters of gamma irradiation.

Coumarinyl(pyrrolyl)ethenes for the detection of Pd2+, CN− and F− ions, test strips based on them and logic gates

New coumarinyl(pyrrolyl)ethenes with a 1,3-thiazole bridge were synthesized. When irradiated at 365 nm, a hexatriene-cyclohexadiene rearrangement of the ring-opened form into a colored non-fluorescent ring-closed isomer occurs. The back reaction takes place when exposed to visible light at 540 nm. Furthermore, the compound with terminal 2,4-di-tert-butyl-6-hydroxybenzylidene receptor group represents a multifunctional sensor exhibiting selective chromogenic activity towards palladium(II) ions and CN− and F− anions. This probe interacts with Pd2+ cations with a noticeable naked eye effect - a change in the solution color from yellow to orange. The complexation stoichiometry is 1:1 and the detection limit was found to be 4.5 × 10−7 mol L−1. Similarly, CN− and F− anions cause a contrast naked eye effect with a change in the color of the solution from yellow to rose-red. For convenient detection of the above ions, test strips containing 4-(2-(2-(2,4-di-tert-butyl-6-hydroxybenzylidene)hydrazinyl)-5-(2-oxo-2H-chromen-3-yl)thiazol-4-yl)-1,5-dimethyl-1H-pyrrole-2-carbonitrile have been developed. In addition, a combinatorial molecular logic gate was designed based on multi-controllable photoswitching properties of the obtained probe.

Near-infrared photoelectrochemical and colorimetric dual-mode aptasensor for determining osteopontin based on Er-MOF nanoballs@gold nanoparticles and Au2Pt nanozymes

A near infrared photoelectrochemical (PEC) and colorimetric dual-mode aptasensor was fabricated for efficiently determining osteopontin (OPN). Er-MOFs and Au2Pt nanoparticles were successfully synthesized. The gold nanoparticles (AuNPs) modified Er-MOF (Er-MOFs@AuNPs) nanocomposites were introduced into the glassy carbon electrode (GCE) to construct a photoelectrochemical sensing interface. OPN aptamer (Apt1) was immobilized onto the Er-MOFs@AuNPs based photoelectrochemical platform through Au-S bond for the selectively recognizing osteopontin. Au2Pt-labeled OPN aptamer (Au2Pt-Apt2) was subsequently captured onto the OPN/Apt1/MOFs@AuNPs/GCE surface to form a sandwich sensing interface, leading to an enhancement on the photocurrent response. Interestingly, Au2Pt nanozyme which possesses peroxidase activity could produce a solution color change in the presence of 3,3′,5,5′-tetramethylbenzidine (TMB) and hydrogen peroxide. The variations of photocurrent response and absorbance can be employed for the quantitative detection of OPN. Under the optimal conditions, the PEC and colorimetric sensing strategies show linear responses towards OPN in the concentration range of 0.01 ∼ 25 ng mL−1 and 1 ∼ 850 ng mL−1, respectively. The calculated determination limits were 2.6 pg mL−1 and 0.04 ng mL−1. The PEC and colorimetric dual-mode sensing platform can provide no crosstalk results and can be mutually verified, thus effectively improving the accuracy and reliability for the determination of OPN.

Characterizations of biogenic selenium nanoparticles and their anti-biofilm potential against Streptococcus mutans ATCC 25175

IntroductionS. mutans has been identified as the primary pathogenic bacterium in biofilm-mediated dental caries. The biogenic selenium nanoparticles (SeNPs) produced by L. plantarum KNF-5 were used in this study against S. mutans ATCC 25175. ObjectivesThe aims of this study were: (1) the biosynthesis of SeNPs by L. plantarum KNF-5, (2) the characterization of SeNPs, (3) the investigation of the inhibitory effect of biogenic SeNPs against S. mutans ATCC 25175, and (4) the determination of the anti-biofilm potential of SeNPS against S. mutans ATCC 25175. Methodology3 mL of the culture was added to 100 mL of MRS medium and incubated. After 4 h, Na2SeO3 solution (concentration 100 μg/mL) was added and incubated at 37 °C for 36 h. The color of the culture solution changed from brownish-yellow to reddish, indicating the formation of SeNPs. The characterization of SeNPs was confirmed by UV-Vis spectrophotometry, FTIR, SEM-EDS and a particle size analyzer. The antibacterial activity was determined by the disk diffusion method, the MIC by the micro-double dilution method, and the biofilm inhibitory potential by the crystal violet method and the MTT assay. The effect of SeNPs on S. mutans ATCC 25175 was determined using SEM and CLSM spectrometry techniques. The sulfate-anthrone method was used to analyze the effect of SeNPs on insoluble extracellular polysaccharides. The expression of genes in S. mutans ATCC 25175 was analyzed by real-time quantitative polymerase chain reaction (RT-qPCR). Preparation of nanoparticlesSeNPs produced by probiotic bacteria are considered a safe method. In this study, L. plantarum KNF-5 (probiotic strain) was used for the production of SeNPs. ResultsThe biogenic SeNPs were spherical and coated with proteins and polysaccharides and had a diameter of about 270 nm. The MIC of the SeNPs against S. mutans ATCC 25175 was 3.125 mg/mL. Biofilm growth was also significantly suppressed at this concentration. The expression of genes responsible for biofilm formation (GtfB, GtfC, BrpA and GbpB,) was reduced when S. mutans ATCC 25175 was treated with SeNPs. ConclusionIt was concluded that the biogenic SeNPs produced by L. plantarum KNF-5 was highly effective to inhibit the growth of S. mutans ATCC 25175. Novelty statementThe application of biogenic SeNPs, a natural anti-biofilm agent against S. mutans ATCC 25175. In the future, this study will provide a new option for the prevention and treatment of dental caries.

Machine vision-based online detection method for color characteristics of cobalt extraction solution

Cobalt, as a rare metal, plays an important role in strategic resources due to its physical, chemical, and mechanical properties in applications. In order to achieve automatic control of the cobalt extraction process, it is necessary to conduct online detection of the color characteristics of the cobalt extraction solution. Unfortunately, due to the lack of online automatic detection methods for the color of cobalt extraction solution, the automatic control of the extraction process has not yet been achieved. Currently, the color of cobalt extraction solution needs to be observed and judged by operators based on experience. This will result in significant detection errors and time lag. To change this situation, an online detection method for color features of cobalt extraction solution based on machine vision is proposed in this article. Firstly, we establish a real-time image acquisition environment for detecting object colors, and then use the Gaussian filters and K-means algorithm to denoise and segment the image. In order to correct color distortion in images caused by ambient light, we measure the color feature values of a set of standard color cards using the machine vision system and a standard spectrophotometer. Based on this test data, we establish chromaticity correction models for the extraction solution using back propagation (BP) network and radial basis function (RBF) network, respectively. The models can correct the color characteristic values of the extraction solution, overcome environmental interference, and thus obtain more accurate color characteristic values of the extraction solution. The established model can be used for online automatic color detection of cobalt extraction solution. The modeling results indicate that in the established color measurement environment, the RBF network model outperforms the BP network model in color feature detection accuracy.

A Dual-Mode Fluorescent Nanoprobe for the Detection and Visual Screening of Pathogenic Bacterial Spores.

Bacterial vegetative cells turn into metabolically dormant spores in certain environmental situations. Once suitable conditions trigger the germination of spores belonging to the pathogenic bacterial category, public safety and environmental hygiene will be threatened, and lives will even be endangered when encountering fatal ones. Instant identification of pathogenic bacterial spores remains a challenging task, since most current approaches belonging to complicated biological methods unsuitable for onsite sensing or emerging alternative chemical techniques are still inseparable from professional instruments. Here we developed a polychromatic fluorescent nanoprobe for ratiometric detection and visual inspection of the pathogenic bacterial spore biomarker, dipicolinic acid (DPA), realizing rapidly accurate screening of pathogenic bacterial spores such as Bacillus anthracis spores. The nanoprobe is made of aminoclay-coated silicon nanoparticles and functionalized with europium ions, exhibiting selective and sensitive response toward DPA and Bacillus subtilis spores (simulants for Bacillus anthracis spores) with excellent linearity. The proposed sensing strategy allowing spore determination of as few as 0.3 × 105 CFU/mL within 10 s was further applied to real environmental sample detection with good accuracy and reliability. Visual quantitative determination can be achieved by analyzing the RGB values of the corresponding test solution color via a color recognition APP on a smartphone. Different test samples can be photographed at the same time, hence the efficient accomplishment of examining bulk samples within minutes. Potentially employed in various on-site sensing occasions, this strategy may develop into a powerful means for distinguishing hazardous pathogens to facilitate timely and proper actions of dealing with multifarious security issues.

Ratiometric fluorescent probes based on carbon dots and europium for rapid detection of tetracycline

Tetracycline (TC) is a typical emerging pharmaceuticals and personal care products (PPCPs) pollutants in the environment. However, TC residues cause severe effects on human health. It is crucial to exploit simple, rapid and sensitive methods to detect TC in water samples. A ratiometric fluorescent probes (CDs-Eu3+) is constructed using carbon dots (CDs) and europium ions (Eu3+) for the visual detection of tetracycline (TC). Under 390 nm excitation, CDs-Eu3+ shows a strong yellow fluorescence at 545 nm and a weak red fluorescence at 619 nm, respectively. In the presence of TC, the fluorescence intensity at 545 nm decreased while the fluorescence intensity at 619 nm increased, which attributed to the internal filtering effect (IFE) and “antenna effect”, respectively. Sensing performance of CDs-Eu3+ probes is further evaluated with respect to various conditions, including salt concentration, Eu3+ concentration, pH, and reaction time. Results reveal that the proposed ratiometric fluorescent probes exhibits a specific recognition ability toward TC. An excellent linear relationship is observed between the fluorescence intensity ratio (F619/F545) and TC concentrations (1⁓100 μM), with a low detection limit (LOD) of 31 nM. The solution (CDs-Eu3+-TC) color gradually changes from yellow to red after adding TC. The probes are successfully applied to determine TC in water with recoveries of 85.43⁓97.53%. Finally, a fluorescent test strip is prepared and used for rapid visual semi-quantitative TC detection.

In-situ highly selective colorimetric trace level recognition of lead and copper ion in real samples by silver nanoparticles

In the current study, an advanced and highly discriminating scheme was developed to detect Pb+2 and Cu+2 using Maltol-capped silver nanoparticles (McAgNPs). Various metal ions i.e. Fe+3, Ce+4, Ni+2, Mg+2, Cd+2, Mo+6, Zn+2, Na+1, Co+2, Ba+2, Cu+2, and Pb+2 was studied, among them, only Pb+2 and Cu+2 caused substantial changes in solution color, shifting from yellow to green and pink immediately after adding AgNPs. This color transformation was accompanied by the emergence of new visible bands at 674 nm for Pb+2 and 608 nm for Cu+2. The characterization of complexes (McAgNPs-Pb+2 and McAgNPs-Cu+2) was carried out by state of art techniques such as visible spectrophotometry, Fourier transform infrared spectroscopy (FTIR), and Atomic force microscopy (AFM). AFM results indicated an increase in particle size after the interaction (i.e., 40 to 150 (Cu+2) and 250 nm (Pb+2)). McAgNPs are remarkably selective for Pb+2 and Cu+2 in the presence of other metal ions (i.e., Fe+3, Ce+4, Mg+2, Ni+2, Mo+6, Zn+2, Cd+2, Co+2, Na+1, Ba+2). The pH effect on both complexes was also investigated over a range of pH 1.0–13.0, revealing that McAgNPs-Pb+2 remained stable across the entire pH range, while McAgNPs-Cu+2 was stable only under acidic conditions. Both interactions exhibited good linearity (0.4–1.0 μM), binding stoichiometry (1-Pb+2:1McAgNPs and 2-Cu+2:3McAgNPs), and their respective limit of detection (LOD) was found to be 0.035 for McAgNPs-Cu+2 and 0.067 μM for McAgNPs-Pb+2. Additionally, the suggested scheme was effectively utilized to detect Pb+2 and Cu+2 in environmental (e.g., lake, tap, mineral, and well water) and biological (e.g., urine and plasma) samples, with recoveries ranging from 94.7 to 105%. Consequently, our approach paves the way for creating innovative and efficient suitable nanoprobe for highly selective and sensitive sensing.

Peroxidase-like activity and mechanism of gold nanoparticle-modified Ti3C2 MXenes for the construction of H2O2 and ampicillin colorimetric sensors.

Transition metal carbides modified by Au nanoparticles (Au/Ti3C2) were synthesized and developed as a colorimetric sensor for the determination of H2O2 and ampicillin. The surface electrical properties of Ti3C2 were changed, and Au nanoparticles (AuNPs) and gold growth solution were synthesized simultaneously. Au/Ti3C2 was obtained by seed growth method with AuNPs modified on the surface of transition metal carbides, nitrides or carbon-nitrides (Ti3C2 MXenes). The synthesized AuNPs and Ti3C2 had no peroxidase-like activity, but Au/Ti3C2 had. The peroxidase catalytic mechanism was due to electron transfer. The peroxidase activity of Au/Ti3C2 can be utilized for the determination of H2O2. The linear range of Au/Ti3C2 for H2O2 was 1-60 µM, and the detection limit was 0.12 µM (S/N = 3). A colometric sensor for ampicillin detection based on Au/Ti3C2 was further constructed since S in ampicillin formed an Au-S bond with Au/Ti3C2, leading to the weakening of its peroxidase-like property. The change of peroxidase-like property attenuated oxidation of TMB, and the ampicillin content was inversely proportional to the concentration of oxidized TMB, and the blue color of solution faded, which enabled the determination of ampicillin. The linear range for ampicillin was 0.005-0.5µg mL- 1, and the detection limit was 1.1 ng mL- 1 (S/N = 3). The sensor was applied to the detection of ampicillin in milk and human serum.

Tuning the fluorescence emission of water-stable CsPb(Br/I)3 perovskite nanocrystal probes for naked-eye visual detection of mercury ion

All-inorganic cesium lead halide perovskite nanocrystals (PNCs) have rarely been reported in analytical chemistry, especially in water environment analysis, due to their high susceptibility to environmental conditions. Herein, we investigate and report a method of visual detection of Hg2+ concentration in aqueous solution using CsPb(Br/I)3 PNCs. In this strategy, three kinds of CsPb(Br/I)3 PNCs with FL emission peaks of 551 nm, 591 nm, and 617 nm were used to detect Hg2+, and it was found that Hg2+ can quench the fluorescence of CsPb(Br/I)3 PNCs and blue-shift the maximum FL emission peak. We also found that the Hg2+ concentration has a good linear relationship with the fluorescence quenching rate (I0/I) and FL emission peak shift (Δλ) of CsPb(Br/I)3 PNCs. With the red-shift of the probe FL emission peak, the detected concentration range of Hg2+ gradually expanded. Therefore, the possibility of detecting Hg2+ concentration without huge equipment was detailed by examining the red (R), green (G), and blue (B) values of photographs of CsPb(Br/I)3 PNCs with Hg2+. Under a 365 nm ultraviolet (UV) lamp, the solution color of CsPb(Br/I)3 PNCs emission peaks at 591 nm gradually changes from orange to green with the increase of Hg2+ concentration, which has an excellent visualization effect. The method presented here has the potential to establish a new analytical method for the visual detection of Hg2+ in aqueous environments, and may also facilitate the application of all-inorganic cesium lead halide perovskite nanocrystals for analytical detection in aqueous environments.

Green-synthesized flattened rice-shaped CuO and metal doped CuO nanoparticles using Bauhinia racemosa Lam. leaves extract and their photocatalytic and biological applications

In the present investigation, a sustainable approach to the biogenic fabrication of CuO nanoparticles (NPs) and transition metals (Co, Mn, and Zn) doped CuO NPs (TMDC NPs) was proposed by employing the Bauhinia racemosa (BR) Lam. leaves extract as a stabilizing and capping agent. The fabrication of CuONPs was immediately verified by a change in the color of the Cu solution from blue to dark grey. Characterizations of the bare CuO and TMDC NPs were done to attribute the physical and chemical characteristics of the NPs employing Fourier Transform Infrared (FT-IR), X-ray Diffraction (XRD), UV–Vis Diffuse Reflectance Spectroscopy (UV–Vis DRS), Photoluminescence (PL), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray analysis (EDX), Transmission Electron Microscopy (TEM), and Brunauer − Emmet − Teller (BET) studies. The acquired Co-CuO NPs demonstrated a substantial crystallinity, smaller crystallite size of ∼10.87 nm, lower bandgap, and reduced recombination rate and were implemented as an effective photocatalyst for the degradation of the amoxicillin (AMX) and tetracycline (TC) antibiotics, as examined by UV − vis spectrophotometric study and confirmed by a hypochromic shift. Based on UV − vis analysis, Co-CuO NPs demonstrated a potent and rapid photocatalytic degradation performance of ∼99 and ∼93 % for the AMX and TC antibiotics within 150 and 210 min respectively. Co-CuO NPs also demonstrated strong antimicrobial performance against Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Aspergillusflavus, Aspergillusniger, and Bacillus subtilis. Further investigation of in-vitro cytotoxic potential against the A549 cell line, utilizing MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay and the free radical scavenging performance of the Co-CuO NPs was estimated by DPPH (2,2-diphenyl-1-picrylhydrazyl) assay utilizing L-ascorbic acid as reference were also performed.

Ultrafast sensitive colorimetric detection of cyanide based on dissolving AgI on Au-AgI heterodimeric nanoparticles via UV–vis spectroscopy and single nanoparticle imaging

The high toxicity of cyanide and its great variety of uses in industrial processes make it necessary to develop sensitive and selective sensors for its determination in food and environmental samples. However, the developed methods usually require long time and expensive instrument, hindering on-site detection. In this work, novel colorimetric assays for cyanide detection were achieved by using UV–vis spectroscopy and single nanoparticle (NP) imaging technology based on a mechanism wherein cyanide dissolves AgI on Au-AgI heterodimeric NPs by forming Ag(CN)2-. The reaction occurred in less than 1 s, leading to the change from Au-AgI NPs to Au NPs and thus blueshift of localized surface plasmon resonance. The solution color turned to purple, and then pink from blue, while single NPs under darkfield microscopy transformed from red to yellow and green. In UV–vis spectroscopy, the shift of peak wavelength (Δλ) is linear to cyanide concentration with an equation of Δλ=0.8784 Ccyanide-2.4910 over the range of 0–75 µM. Under darkfield microscopy, the linear regression equations were G/R=0.0677 Ccyanide+0.3717 (R2=0.992) with cyanide over the range of 0.2–4.0 μM and G/R=0.2945 Ccyanide+0.4835(R2=0.994) in the range of 4.0–15.0 μM, where G/R is the intensity ratio in green and red channel. The methods were applied for analysis of waters and foods, achieving recovery rates of 97.4–106.3% for UV–vis spectroscopy and 98.6–108.1% for single NP imaging. The techniques offer expeditious, highly discriminating, and on-site capable solutions for cyanide detection, with high practicality.

Hydrophobic barrier-free laminated paper-based analytical device (LPAD) using a diameter-based measurement for determination of iodide in pharmaceutical products

This work presents, for the first time, an exploitation of an argentometric Mohr's method for iodide detection using diameter-based measurement on laminated paper-based analytical device (LPAD). Our LPAD is simplified fabricated with no required hydrophobic barrier for patterning a detection flow channel. In the absence of a flow channel, the liquid is imbibed radially into the filter paper outward from the small center inlet hole. This imbibition leads to the measurement of diameter after the formation of the precipitation product. For LPAD, a rectangular piece of Whatman filter paper is cut and positioned between a top laminating sheet, which has a hole punched for inlet, and a bottom laminating sheet. The central inlet hole enables access to the liquid on the paper. For iodide analysis, silver nitrate is dispensed first, followed by the iodide standard/sample. This process leads to the formation of pale-yellow silver iodide solids on the paper. The chromate indicator solution is subsequently loaded to the paper. The color of the chromate solution imparts a tint to the circular band of silver iodide solids, resulting in an intense yellow color. When the silver iodide precipitates are stained, the chromate solution typically serves as an indicator, chemically reacting to an excess silver nitrate solution moistened on paper. This reaction generates an outer reddish-brown ring of silver chromate. The distinct color contrast between the intense yellow (tinted silver iodide) and reddish-brown (silver chromate) allows for clear observation of the measurement boundary, facilitating diameter-based measurements of the circular band of silver iodide. We demonstrate the applicability in analysis of pharmaceutical KI tablets. The quantitative results obtained from diameter-based measurement LPAD show good agreement with those obtained from the potentiometric method. Our hydrophobic barrier-free LPAD is rapid, cost-effective, low liquid consumption and applicable for onsite analysis.

A Chromogenic Probe for Detection of Biologically Important Anions and its Implications for Designing Molecular Logic Gates.

Detection of fluoride (F-), acetate (AcO-), and cyanide (CN-) anions is vital from the biological and environmental aspects. In the present contributions, we have introduced a simple Salen-type chromogenic sensor, BEN, to detect these biologically important anions. Changes in UV-visible absorption spectra and color of BEN solution from very pale yellow to pink color are similar for each of these anions and found to be reversible only in the case of F- ions in attendance of HSO4- ions. The estimated limit of detection of BEN solution for detecting F-, AcO-, and CN- anions is found to be below the micromolar (μM) concentration level. Our fabricated handy paper test kit is suitable for qualitatively naked-eye detection of the anions. An immediate quantitative estimation of these important anions is possible using our BEN employing a smartphone, avoiding any costly experimental setup.

An “on-off-on” fluorescent sensor based on TSPP-gallic acid: Visual detection of S2− in actual samples

A novel “on-off-on” switches fluorescence sensor based on TSPP-gallic acid (GA) for S[Formula: see text]-detecting was designed in this article. 5,10,15,20- (4-sulphonatophenyl) porphyrin (TSPP) was synthesized by a modified “one-pot” method. The synthesized TSPP was used as a fluorescence probe for the construction of a fluorescence sensing system. At room temperature, the maximum fluorescence emission wavelength could be obtained at 642 nm when the excitation wavelength was 515 nm when the fluorescence signal was in the “on” mode. The TSPP solution appeared pink in color at this moment. When GA was introduced into the TSPP solution, the fluorescence signal was turned off (fluorescence intensity was quenched) due to the protonation of TSPP, which was caused by the weak acidity of GA. The color of the TSPP solution changed from pink to green. Following that, an acid-base reaction between S[Formula: see text]and GA was initiated when S[Formula: see text]was introduced into the TSPP-GA system, leading to the liberation of TSPP and restoration of fluorescence intensity. The solution color reverted to red, indicating that the fluorescence sensing system had returned to the “on” mode. The TSPP-GA system had good selectivity and sensitivity to S[Formula: see text], the linear range was 4.52 × 10[Formula: see text] M [Formula: see text] 4.34 × 10[Formula: see text] M, and the detection limit (LOD) was 0.87 [Formula: see text] M. It could be used to detect sulfur ions in actual samples with satisfactory recoveries and RSD values.