The use of silver nanoparticles stabilized with citrate and polyvinylpyrrolidone as a sensor for aluminum ions determination is proposed in this paper. These non-functionalized and specific nanoparticles provide a highly selective and sensitive detection system for aluminum in acidic solutions. The synthesized nanoparticles were characterized by transmission electron microscopy. Surface plasmon band deconvolution analysis was applied to study the interaction between silver nanoparticles and aluminum ions in solution. The interaction band in the UV-visible region was used as an analytical signal for quantitation purposes. The proposed detection system offers an effective AND wide linearity range (0.1-10 3 nM), specificity for Al(III) in THE presence of other metallic ions in solution, as well as high sensitivity (limit of detection = 40.5 nM). The proposed silver-nanoparticles-based sensor WAS successfully used for detecting Al(III) in real water samples.Materials 2020, 13, 1373 2 of 15 aluminum ions through which Al(III) enters the human food chain; plant roots are also adversely affected by the release of Al(III) ion from the acidic soil [11][12][13].Considering the strong impact of aluminum on human health and the environment, Al(III) detection is important. Analytical techniques commonly used for detecting metal ions include ion selective electrodes [14], electrochemical methods [15], atomic absorption and emission spectrometry [16,17], and colorimetric sensors [18,19].Metallic nanoparticles were proposed as colorimetric sensors for numerous metal ions in different kind of samples. Gold nanoparticles (AuNPs) as well as silver nanoparticles (AgNPs) have been used for these purposes [20][21][22][23][24][25][26]. Usually, AuNPs and AgNPs are functionalized to obtain specific and selective sensors for detecting the desired metallic ion. Chen et al. used triazole-ether functionalized gold nanoparticles for the colorimetric detection of Al(III) ions [27]. Citrate-capped gold nanoparticles were used for rapid visual detection of aluminum at concentrations down to 1.0 µM [18]. Ascorbic-acid-capped gold nanoparticles were used for the selective colorimetric detection of aluminum ions in ground water [28]. Liu et al. proposed a colorimetric assay for Al(III) based on alizarin red S-functionalized silver nanoparticles [4]. Silver nanoparticles stabilized by reduced glutathione (GSH-AgNPs) in the presence of L-cysteine were used for colorimetric detection of aluminum by Yang et al. [29]. Even stable silver nanoclusters have been used for the detection of aluminum ions [30]. Silver nanoparticles coated with citrate or polyvinylpyrrolidone (PVP) were demonstrated to be versatile due to their different applications in a wide variety of fields like electronic applications or cell imaging between others [31][32][33].As reported in the literature, the use of metallic nanoparticles as a detection system for metal ions is based on the shift to longer wavelengths of the surface plasmon resonance (SPR) absorption band due to the pr...