This work presents the development of green paper-based sensors for pH detection. They were obtained with natural dyes extracted from different vegetables, fruits, and flowers: red cabbage (brassica oleracea capitata rubra), blueberry (vaccinium myrtillus), and butterfly pea flower (clitoria ternatea); filter paper was used as a substrate. The RGB indexes of the PADs' colours were extracted both by the software GIMP from the pictures taken by a n iPad, or by a homemade RGB-detector (Arduino-based and built through a 3D printer) with the aim of obtaining RGB indexes not affected by the light and the smartphone's camera sensitivity. Partial least square regression (PLS) was applied to correlate the colour of the PAD's picture with the solutions' pH. Different solutions at various pHs, ranging from 1 to 13 were obtained by titrating H3PO4 with standardized NaOH, and they were used to create the PLS model. Some real samples were examined as a test set, and the results were validated with a pH meter. The best results were obtained with red cabbage and butterfly pea flower either single or in mixtures, since a wider range of colour variation with the solution pH. The most accurate response was however given by an array with PADs made of red cabbage, butterfly pea flower, and their mixtures at 25:75, 50:50, 75:25. These devices were obtained with natural dyes and filter paper, so they are completely biodegradable and eco-friendly. Their fabrication does not require toxic or expensive reagents and sophisticated equipment. The developed RGB-detector, built-up with low-cost components and recycled batteries, is an added value for making the measure cheap, easy and feasible also by non-expert people.
In questa tesi si sono sviluppati sensori per il rilevamento del pH. Sono stati ottenuti da coloranti naturali estratti da diversi tipi di verdura, frutta, fiori: cavolo rosso (brassica oleracea capitata rubra), mirtillo (vaccinium myrtillus) e fiore di pisello blu (clitoria ternatea): la carta da filtro è stata utilizzata come substrato. Gli indici RGB dei colori dei PAD sono stati estratti sia dal software GIMP partendo dalle immagini scattate da un iPad, sia da un rilevatore RGB costruito attraverso le funzionalità di Arduino e grazie a una sampante 3D. L’obiettivo dell’utilizzo di tale strumento era di ottenere indici RGB non influenzati dalla luce e dalla sensibilità della fotocamera dello smartphone. La regressione parziale del minimo quadrato (PLS) è stata applicata per correlare il colore dell'immagine del PAD con il pH delle soluzioni. Soluzioni con pH che vanno da 1 a 13 sono state ottenute titolando H3PO4 con NaOH standardizzato e sono state utilizzate per creare il modello PLS. Alcuni campioni reali sono stati esaminati come set di test e i risultati sono stati convalidati con un pHmetro. I migliori risultati sono stati ottenuti con cavolo rosso e fiore di pisello blu, singoli o in miscele, poiché permettevano una gamma più ampia di variazioni di colore con il pH della soluzione. Si è però determinato che i risultati più attendibili fossero dati da un array che presentava PADs a base di cavolo rosso, fiore del pisello blu, e le miscele con proporzioni al 25:75, 50:50, 75:25. Questi dispositivi sono stati ottenuti con coloranti naturali e carta da filtro, quindi sono completamente biodegradabili ed eco-compatibili. La loro fabbricazione non richiede reagenti tossici o costosi e attrezzature sofisticate. Anche il rivelatore RGB sviluppato, costruito con componenti a basso costo e batterie riciclate, è un valore aggiunto per rendere la misura economica, facile e fattibile anche da parte di persone non esperte.
Green PADs@RGB-detector: dispositivo semplice ed economico per la determinazione del pH
PAZZI, BIANCA MARIA
2021/2022
Abstract
This work presents the development of green paper-based sensors for pH detection. They were obtained with natural dyes extracted from different vegetables, fruits, and flowers: red cabbage (brassica oleracea capitata rubra), blueberry (vaccinium myrtillus), and butterfly pea flower (clitoria ternatea); filter paper was used as a substrate. The RGB indexes of the PADs' colours were extracted both by the software GIMP from the pictures taken by a n iPad, or by a homemade RGB-detector (Arduino-based and built through a 3D printer) with the aim of obtaining RGB indexes not affected by the light and the smartphone's camera sensitivity. Partial least square regression (PLS) was applied to correlate the colour of the PAD's picture with the solutions' pH. Different solutions at various pHs, ranging from 1 to 13 were obtained by titrating H3PO4 with standardized NaOH, and they were used to create the PLS model. Some real samples were examined as a test set, and the results were validated with a pH meter. The best results were obtained with red cabbage and butterfly pea flower either single or in mixtures, since a wider range of colour variation with the solution pH. The most accurate response was however given by an array with PADs made of red cabbage, butterfly pea flower, and their mixtures at 25:75, 50:50, 75:25. These devices were obtained with natural dyes and filter paper, so they are completely biodegradable and eco-friendly. Their fabrication does not require toxic or expensive reagents and sophisticated equipment. The developed RGB-detector, built-up with low-cost components and recycled batteries, is an added value for making the measure cheap, easy and feasible also by non-expert people.È consentito all'utente scaricare e condividere i documenti disponibili a testo pieno in UNITESI UNIPV nel rispetto della licenza Creative Commons del tipo CC BY NC ND.
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https://hdl.handle.net/20.500.14239/14325