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We suggest the use of a simple and cheap synthesis of micro- and nanosized copper­(I) oxide particles with variable color as a demonstration of size-dependent optical properties of semiconductors for high school students. The synthesis of Cu2O particles is performed by reducing alkaline copper­(II)–citrate complex (Benedict’s reagent) with glucose. Significant color and size changes of Cu2O particles at various reaction conditions are observed and discussed. Proposed demonstration is very useful for introducing students (including undergraduate students) to size-dependent optical properties of semiconductors and principles of synthesis of nanosized objects.

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The aim of the work is the development of the procedure for ceftriaxone (antibiotic drug of cephalosporin class) detection in urine using surface-enhanced Raman spectroscopy (SERS). Hydroxylamine stabilized silver nanoparticles were used as SERS-active material. Additional urine pretreatment steps were developed in order to eliminate the influence of creatinine on the ceftriaxone SERS signal. These steps include adjusting of the sample pH to alkaline value (pH 13) and purification of the sample using silica gel column chromatography. Alkali pH increases SERS signal of ceftriaxone, while silica gel separates the analyte from creatinine-the main admixture in urine which provides inappropriate SERS signal background. Additionally, it was found that total protein content up to 0.2 mg/mL (upper level for urine of healthy person) and pH deviation of initial urine do not influence on SERS signal of ceftriaxone. The proposed detection procedure enables fast (~ 10 min) determination of ceftriaxone in artificially spiked urine samples within 5 to 500 μg/mL range of concentrations which matches the range of the drug concentrations in urine after injection of therapeutically required dosages. Limits of detection (3σ) and quantification (10σ) were found to be 0.4 and 2.0 μg/mL, correspondingly. Graphical abstract Application of urine pretreatment enables the purification of target analyte from intrinsic urine components and improves SERS-based detection of ceftriaxone (antibiotic drug).

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