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A novel optical probe has been successfully developed for the selective detection of Os(VIII) ions. This osmium-sensing platform was intricately designed by incorporating 4-(thiazol-2-yldiazenyl)benzene-1,3-diol (TDBD) as the ionophore within a plasticized PVC membrane, and tributylphosphate (TBP) serving as the plasticizer. Upon exposure to Os(VIII) ions in a 0.5 M HClO₄ acid milieu, the sensing membrane undergoes a distinctive chromatic transition, shifting from a yellow to a pink hue. The preparation of the sensor and the methodology for Os(VIII) determination were meticulously refined to achieve optimal performance. Under these carefully optimized experimental conditions, the proposed optode demonstrated an impressive linear detection range spanning from 2.5 × 10⁻⁹ to 2.5 × 10⁻⁵ M for Os(VIII), alongside remarkable detection and quantification limits of 7.24 × 10⁻¹⁰ and 2.4 × 10⁻⁹ M, respectively. The sensor consistently delivered highly reproducible results, as evidenced by relative standard deviation (RSD) values of 1.45% and 1.30% for Os(VIII) concentrations at 7.5 × 10⁻⁷ and 2.5 × 10⁻⁶ M, respectively, underscoring its precision and reliability. Furthermore, the sensor exhibited a swift response time of 3.0 min, further emphasizing its efficiency. The incorporation of PIMs into the sensor architecture led to a remarkable eight-fold enhancement in its response compared to counterparts lacking PIMs, signifying a significant performance improvement. In assessing potential interference, an investigation into the influence of other ions on Os(III) determination revealed that the prepared sensor displayed exceptional selectivity for Os(VIII) ions, with negligible responses observed in the presence of common ions. Collectively, these experimental findings underscore the sensor's efficacy as an invaluable tool for the precise analysis of osmium content in water samples, aligning it with the rigorous standards of international scientific research.

Compositional analysis of polysaccharides is crucial in many applications of analytical chemistry, and typically involves hydrolysis as initial step, to break glycosidic bonds and release individual monosaccharide units. We developed a new method for the microwave-assisted acid hydrolysis of polysaccharides, here applied for determining the composition of the polysaccharide fraction within the lignocellulosic matrix of Pinus sylvestris. The optimisation of reaction conditions was carried out using a GC–MS method after a double-step sugar derivatization process.

Under the optimized conditions, specifically, employing 2 M TFA, 40 min, and 120 °C, a high depolymerisation yield was achieved with minimal degradation. Furthermore, the amount of polysaccharides detected in pine wood aligns with the results in existing literature, substantiating the determined chemical composition.

The synergy of microwave-assisted acid hydrolysis and full factorial design not only facilitated the determination of the optimal hydrolysis conditions but also enabled the assessment of the parameters influencing the polysaccharide hydrolysis process and their relationships. This approach made it feasible to achieve maximum hydrolysis efficiency while minimizing analyte degradation, employing a method that reduces environmental impact through the use of microwave energy. This strategy effectively reduced the required reaction temperature, time, and reagent quantities.

Microwaves are electromagnetic waves which move at the speed of light. Samples directly exposed to this phenomenon are heated faster than conventional conduction heating methods. This is exploited in acid assisted digestion where a food sample in a suitable acid matrix can be completely destroyed leaving a clear solution of measurable elements. In pressurised systems the temperature can be rapidly increased far above the conventional boiling point of the solvent and the closed microwave vessel environment is ideal for volatile elements.

There is a constant aspiration to achieve lower levels of detection and advances in instrument capabilities with specialised plasma based techniques for the identification and quantification of individual elements at ultra-trace levels have evolved. To realise this; sample preparation, digestion efficiency and sample introduction need to be optimised. Exogenous inputs such as preparation environment, reagent grade, the analyst and apparatus cleaning steps all have the potential to leave an elemental footprint on the sample and therefore contribute to the uncertainty of the analytical result. Knowledge of sample composition and subsequent interaction with microwaves and plasma are an important consideration for complete digestion without which the result is not accurate.

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.

Ensuring accurate and precise measurements of analytes is crucial in gravimetric analysis but can be jeopardized by overlooking analyte in the filtrate, washing solutions, residue during analytical procedure, and weighing form of analyte. To address this issue, a stoichiometric approach for the purity determination of high-purity BeO was developed using gravimetric analysis. This method involved the systematic stoichiometric evaluation of the stepwise conversion of the different weighing forms of Be. The initial BeO sample underwent sequential conversion to the Be complex with N-benzoyl-N-phenyl hydroxylamine, BeO, and BeSO₄; each was evaluated for stoichiometry via gravimetric analysis. The amounts of Be in the filtrate and washing solution, and their loss during sample preparation were measured using inductively coupled plasma-optical emission spectrometry (ICP-OES). Additionally, the sulfate content in the BeSO₄ precipitate was determined by the gravimetric analysis of BaSO₄ to validate the stoichiometry of the precipitate. The observed mass ratios of different Be weighing forms were compared with the theoretical values at each conversion step. The composition of the final converted BeSO_4, i.e., the observed mass ratio of BaSO₄/BeSO₄, was comparable to the theoretical composition. The purity of the initial BeO sample was determined to be 100.03 % ± 0.17 % (k=2). The measured purity was successfully validated by comparing it with that of NIST SRM 3105a Be standard solution using ICP-OES.

Background

Upconverting nanophosphors (UCNPs) are composed of certain nanosized inorganic host materials doped with specific rare earth ions. They exhibit the phenomenon of photon upconversion, whereby the sequential absorption of two or more low energy photons is followed by luminescent emission of multiple photons with higher energy. In addition, they have other attractive optical features such as NIR-absorption, sharp emission bands, exceptional photostability and high quantum yield. These properties make UCNPs lucrative probes for number of optical applications, such as imaging, sensing and theranostics.

Overview

UCNPs have been used as specific and ultrasensitive probes for sensing of variety of analytes, such as gas molecules, metal ions, fine particles, pH and a number of molecules, biochemicals and macromolecules. Their absorption and emission in the NIR range facilitates the background free biosensing in situ, in vitro and in vivo. Their multicoloured emissions allow a suitable emission band to serve as a donor for energy transfer to another attached optical probe, while a separate emission band to serve as an internal reference in ratiometric sensing applications. This comprehensive review provides an in-depth exploration of the versatile applications of UCNPs in the optical sensing of various analytes based on energy transfer mechanisms, with emphasis on the recent developments. . The focus is on synthesizing UCNPs, surface functionalization, and their effective utilization especially in detecting gas molecules, pH changes, ions, free radicals, and disease biomarkers. Through a meticulous examination of the use of UCNPs, this review aims to contribute to a deeper understanding of their potential and pave the way for future advancements and challenges in optical sensing.

The slightly sweet and acidic taste offered by Pontianak Siam oranges is influenced by the total soluble solids (TSS) and acidity in the fruit, in which, measuring these attributes is commonly performed using instruments that potentially damage the fruit's structure, thus, impractical for fresh fruit products. Moreover, the process of classifying the quality of fresh oranges has been based on physical appearance, leading to subjective results. Correspondingly, the objective of the study is to develop a prediction method for the physicochemical characteristics of Pontianak Siam oranges based on VIS-NIR-Fluorescence spectroscopy and an artificial neural network (ANN) model. The method is applicable to classify oranges based on physicochemical characteristics without damaging the fruit's structure. As a result, the best model for classifying the maturity level of Pontianak Siam oranges was obtained using a dataset with all feature combined spectra, attaining a training accuracy of 0.99 and testing accuracy of 1. The best model for predicting TSS was obtained using all feature combined spectra dataset, attaining R² training = 0.89 and R² testing = 0.91. The best model for predicting acidity was obtained using all feature reflectance spectra datasets, attaining R² training = 0.96 and R² testing = 0.97. The best model for predicting fruit firmness was obtained using all feature reflectance spectra dataset, attaining R² training = 0.97, R² testing = 0.89. Overall, the combination of Vis-NIR reflectance and fluorescence spectroscopy have the potential to be applied for non-destructive assessment of citrus quality in terms of visual classification and maturity parameters prediction.

Recent advancements in synthetic biology have facilitated the concept of a cell-based and cell-free biosensing platform, which enables the identification of molecular signals encompassing metal/chemical to disease biomarkers. The artificial sensing incorporates the concept of both whole-cell and cell-free biosensing strategies, which include highly regulated natural and synthetic components to exhibit genetically encoded molecular sensing properties. These sensors utilize protein expression to release signalling molecules as the result of received input to facilitate the detection of analytes. Intending to use modified living cells or artificial cells in biosensing, the proposed study highlights the importance of cell-based and cell-free sensors in biomedical and diagnostics. The article's first section will explain the biosensing types including cell-free, cell-based, vesicle-based, and paper-based sensing where sensing relies on cell, cellular components, and cell-free systems which mostly involve transcriptional or translational machinery. It highlights the advantages, disadvantages, and challenges of advancing approaches. The second section of the article elaborates on the principle of sensing and the strategies involved. Though very few studies have been reported on this topic, therefore, the current article focuses on the artificial sensors that have been designed for medical and diagnostic purposes. The review also marks the current and future advancements in the field including artificial intelligence, nanotechnology, stem cells, and omics. Sensing recently has a big impact on disease diagnosis as well as drug development and targeted therapies. While newly developed biology-based diagnostics technologies still have high costs, require highly trained personnel, suffer stability issues and reduce sensor performance. Therefore, this review brings readers’ attention to advances and challenges in the following field and promotes the resolution of medical and diagnostics issues in the future.

We developed a two-step dual-layer solid-phase extraction (SPE) method to separate and concentrate minor bioactive compounds of golden oyster mushroom (Pleurotus citrinopileatus) methanol extract. The mushroom extract is rich in fatty acids, including the highly abundant (20–35 %) and antibacterial linoleic acid. To eliminate the masking effect of linoleic acid in the bioassay, its removal was achieved by homemade dual-layer SPE that consisted of a lower C₁₈ phase and an upper silica gel phase with the dried-on extract. In the first step the elution was performed with water (aqueous eluate), and then the dried C₁₈ and silica gel phases were eluted separately with methanol (C₁₈ methanol eluate and silica gel methanol eluate, respectively). Thin-layer chromatography (TLC)-effect-directed analysis demonstrated that the aqueous eluate contained sugars and antioxidants (TLC-DPPH); fatty acids were present in the silica gel methanol eluate, in the C₁₈ methanol eluate the biologically active minor secondary metabolites were concentrated (TLC–Bacillus subtilis assay) beside 2 % remained linoleic acid according to HPLC-UV measurement. As a result, the antioxidant and antibacterial metabolites divided, and the low-abundant antibacterial compounds could be detected. Based on this study, the substance found at R_F 0.25 by TLC-DPPH played the most significant role in generating the antioxidant effect of the aqueous eluate, equivalent to 5.07 ± 0.09 µg of gallic acid. Moreover, each SPE fraction and raw extract were tested for antibacterial effect using a microplate assay with a non-pathogenic Gram-positive Bacillus subtilis. The P. citrinopileatus extract (MIC-value – 50 µg/mL) and C₁₈ methanol eluate (MIC-value - 25 µg/mL) inhibited the growth of B. subtilis while the other eluates did not.

Here we report on fine-tuning of highly bright fluorogenic cyanine dye, benzo[c,d]indole-oxazolo[5,4-c]pyridine (BIOP: λ_em = 570 nm, Φ_free = 0.00038, Φ_bound = 0.52), recently developed by our group for nucleolar RNA imaging in living cells. We tuned an emission maximum to the longer wavelength by replacing oxazolopyridine unit with its isomer. The resulting probe with oxazolo[4,5-b]pyridine, named BIOP [4,5-b], exhibited a significant off-on signaling ability for RNA (λ_em = 580 nm, Φ_free = 0.002, Φ_bound = 0.46) that almost compared with BIOP. BIOP [4,5-b] was applicable to live-cell imaging, where wash-free protocol was available. Importantly, the slight change in spectral features would be expected to minimize the false signal from BIOP [4,5-b] in co-staining experiments with typical green-emissive dyes. In addition, thanks to the unique spectral shape that is typical of cyanine dyes, we demonstrate that yellow-emissive BIOP [4,5-b] also did work as a pseudo red-emissive dye (λ_em > 600 nm) for live-cell RNA imaging, for which we just switch filter set to typical one for real red-emissive dyes (Ex 560/40 nm; Em 645/75 nm).