Waterproof Cellulose-Based Substrates for In-Drop Plasmonic Colorimetric Sensing of Volatiles: Application to Acid-Labile Sulfide Determination in Waters

Abstract

The present work reports on the assessment of widely available waterproof cellulose-based substrates for the development of sensitive in-drop plasmonic sensing approaches. The applicability of three inexpensive substrates, namely, Whatman 1PS, polyethylene-coated filter paper, and tracing paper, as holders for microvolumes of colloidal solutions was evaluated. Waterproof cellulose-based substrates demonstrated to be highly convenient platforms for analytical purposes, as they enabled in situ generation of volatiles and syringeless drop exposure unlike conventional single-drop microextraction approaches and can behave as sample compartments for smartphone-based colorimetric sensing in an integrated way. Remarkably, large drop volumes (≥20 μL) of colloidal solutions can be employed for enrichment processes when using Whatman 1PS as holder. In addition, the stability and potential applicability of spherical, rod-shaped, and core–shell metallic NPs onto waterproof cellulose-based substrates was evaluated. In particular, Au@AgNPs showed potential for the colorimetric detection of in situ generated H 2 S, I 2 , and Br 2 , whereas AuNRs hold promise for I 2 , Br 2 , and Hg 0 colorimetric sensing. As a proof of concept, a smartphone-based colorimetric assay for determination of acid-labile sulfide in environmental water samples was developed with the proposed approach taking advantage of the ability of Au@AgNPs for H 2 S sensing. The assay showed a limit of detection of 0.46 μM and a repeatability of 4.4% ( N = 8), yielding satisfactory recoveries (91–107%) when applied to the analysis of environmental waters.

Detection of gases and organic vapors by cellulose-based sensors

“…1 filter paper Fluorimetric 37 µM 5.8% Water and sediments 25 min [ 90 ] Bromide and bromate Citric acid/cysteamine fluorophore Whatman no. 1 filter paper Fluorimetric (smartphone) 5.4 and 0.9 µg/L 8.3 and 6.3% Water 30 min [ 91 ] Nickel(II) CdTe QDs Chromatography paper Fluorimetric (smartphone) 6.2 µg/L 3.2% Tea infusion 20 min [ 92 ] Arsenic, antimony, and bismuth AgNPs Whatman 602H filter paper ICP-MS 1–15 ng/L 1.2–2.7% Water 10 min [ 93 ] Selenium(IV) AuNPs Whatman grade 44 Colorimetric (scanner) 12 µg/L 4–5% Water 3 min [ 94 ] Sulfide Au@AgNPs Whatman 1PS Colorimetric (smartphone) 14.7 µg/L 4.4% Water 22 min [ 95 ] Microfluidic PADs Ammonium 3-nitrophenol, bromothymol blue Whatman grade 4 filter pa...…”

“…The analysis, however, usually required spotting the enriched microdrop on a hydrophilic paper substrate [ 94 ]. In a recent contribution, we have demonstrated the applicability of waterproof cellulose–based substrates as holders for carrying out in-drop enrichment and smartphone-assisted plasmonic colorimetric detection without the requirement of transferring the enriched microdrop to a sample compartment for analysis [ 95 ].…”

Bacterial nanocellulose, a sustainable alternative, to implement cleaner production in the design of biosensors to detect heavy metals in surface waters

“…48,49 The concept of "flexible plasmonic substrates" refers to plasmonic nanoparticles (metals such as Au and Ag) impregnated into flexible solid substrates such as bacterial nanocellulose. [50][51][52] Which presents advantages over conventional rigid substrates in terms of cost, processability and sustainability. 53 Flexible substrates can be used, for example as packaging, can be wrapped around non-flat substrates, or as swabs to collect wound samples.…”