Search

An electronic tongue was developed for the detection of lactose content in commercial foods. This was accomplished by employing optimized detection units comprised of gelatin films and information visualization methods for data analysis. The films incorporating gelatin, tannic acid, and zein, served as the basis for the sensors, whose electrodes were screen printed using carbon black ink. Self-supporting films were produced using various combinations of these materials, some of which had limited solubility in water (from 33% to 36%). They were hydrophobic and yielded reproducible electrical impedance spectra to be used as sensing units. Lactose detection experiments were conducted using various standard concentrations and commercial food samples. Capacitance decreased with lactose concentration at low frequencies, with films lacking a hydrophobic coating showing higher capacitance signals (exceeding 200 nF). Low limits of detection were obtained for the most sensitive films, as low as 2.03 × 10−19 mol/L, comparable to existing biosensors to detect lactose. Combining data from four sensing units in an electronic tongue allowed for the differentiation of lactose concentrations ranging from 1 × 10−20 mol/L to 1 × 10−6 mol/L using the interactive document mapping (IDMAP) projection technique, leading to a silhouette coefficient of 0.716. The discriminatory power of the electronic tongue was validated by distinguishing between lactose-containing and lactose-free food products. These findings highlight the potential of electronic tongues made with sustainable materials for applications in food quality assessment and lactose intolerance management.

We have developed carbon quantum dots (CQDs) with excellent photoluminescence (PL) properties from macaúba (Acrocomia aculeate) fibers; a widely available cellulosic biomass species of palm trees in South America. As-prepared CQDs showed quasi-spherical morphology with high aqueous solubility and strong excitation-dependent fluorescence behaviour. Interestingly, the CQDs display fluorescence 'turn-off' response with excellent sensitivity toward multi-metal ions including Fe3+, Cu2+ and Hg2+ with very low detection limits of 0.69 μM, 0.99 μM, 0.25 μM, respectively. Notably, ascorbic acid (AA) induced a change in the (turn-off) fluorescence of Fe3+-CQDs, which caused an almost 70% revival of fluorescence (turn-on) by displacing Fe3+ ions. We have also harnessed CQDs as the visible-light-induced photocatalyst to reduce CO2 in water. Especially, the CQDs efficiently promote the photocatalytic reduction of CO2 into methane (CH4) with an evolution rate of 99.8 nmol/g at 436 nm in aqueous conditions. This indicates that the CQDs provide abundant active sites for CO2 adsorption and thus enhance the separation and migration of photo-induced charge carriers that efficiently reduce CO2 into CH4 without any co-catalyst in 100% water. [ABSTRACT FROM AUTHOR]

Urea levels in urine play an important parameter in diagnosing bodily conditions through liver and kidney examinations. The typical reagent for detecting urea content in urine is para-dimethylaminobenzaldehyde (pDMAB). However, it has a drawback related to the instability of color in the resulting Schiff base compound (pDMAB-urea). In this study, the synthesized vanillin compound derived from clove oil serves as the foundational material for a urea chemosensor based on the colorimetric concept. The synthesized vanillin was characterized using FTIR, GCMS, and 1H-NMR. The formulation of the vanillin compound as a sensor was conducted by assessing the suitable solvent, determining the optimal mass of vanillin, and evaluating the acid-base conditions of the sensor formulation system both qualitatively and quantitatively. Subsequently, the most effective formulation was selected for detecting urea in urine samples. The synthesis of vanillin yielded a purity level of 95%. The optimal formulation was obtained at an optimum mass of vanilla of 0.75 g in 50 mL of 96% ethanol and 10 mL of 10% NaOH. The color change in the sample was from colorless to greenish yellow (436 nm). The vanillin obtained was applied to urine samples with the best results at a sample dilution level of 10,000×. [ABSTRACT FROM AUTHOR]