My Master's thesis was aimed at developing and testing paper-based SERS sensors for the detection and quantification of selected examples of anti-epileptic drugs, namely Perampanel (PER) and Cannabidiol (CBD). Properly prepared filter-paper supports were loaded with silver or gold nanoparticles by means of simple, rapid and inexpensive techniques, such as dip-coating with colloidal dispersions and in situ reduction of a metallic precursor, and the dipping procedure was further accelerated by the use of a centrifuge. Both the colloids and the final substrates were characterized by UV-VIS-NIR spectroscopy and the nanostructured morphology was investigated with scanning electron microscopy (SEM). Silver substrates produced by dip-coating (via both natural sedimentation and centrifugation) were tested using acidified PER solutions in a concentration range between 10-4 M and 10-6 M and SERS measurements were carried out using the 632.8 nm excitation and adopting the spinning-cell setup to overcome the problem of spatial non-uniformity. At the same time, the relevant problem of the strong contribution originating from the background was addressed and chloride-containing solutions proved to be effective in significantly reducing the background. The same substrates were employed for quantitative SERS measurements of PER; despite quite large error bars, arising primarily from the poor inter-sample repeatability, a linear correlation between the average peak height and the PER concentration was observed. Moving to the second analyte, silver substrates produced via centrifugation were tested with a 10-4 M solution of CBD, although the final spectra, even upon the addition of the complexing and enhancing agent MgCl2, were quite unsatisfactory. Finally, the last chapter is devoted to substrates prepared by in situ reduction of silver onto paper supports. PER was clearly detected on substrates produced with trisodium citrate (TSC) as reducing agent, whereas the silver content in the absence of TSC was low, resulting in poor SERS properties. The final results highlighted the potential of rapidly and easily prepared paper-made sensors for the SERS detection of specific analytes, paving the way for future development and optimization.
Il mio lavoro di tesi magistrale è finalizzato a sviluppare e testare sensori SERS basati su carta per il rilevamento e la quantificazione di alcuni esempi di farmaci antiepilettici, ossia il Perampanel (PER) e il Cannabidiolo (CBD). Alcuni supporti di carta da filtro opportunamente preparati sono stati caricati con nanoparticelle d’argento e d’oro mediante tecniche semplici, rapide e poco costose, come il dip-coating con dispersioni colloidali e la riduzione in situ di un precursore metallico, e la procedura di immersione è stata ulteriormente accelerata dall’utilizzo di una centrifuga. Sia i colloidi, sia i substrati finali sono stati caratterizzati mediante spettroscopia UV-VIS-NIR e la morfologia nanostrutturata è stata indagata mediante microscopia elettronica a scansione (SEM). I substrati d’argento prodotti per dip-coating (sia attraverso sedimentazione naturale, sia per centrifugazione) sono stati testati usando soluzioni acidificate di PER nell’intervallo di concentrazione tra 10-4 M e 10-6 M, e le misure SERS sono state condotte utilizzando un laser 632.8 nm e adottando un set-up con rotazione (spinning-cell) per risolvere il problema della mancanza di uniformità spaziale. Contemporaneamente, è stato affrontato il problema del forte contributo derivante dal fondo e alcune soluzioni contenenti cloruri si sono dimostrate efficaci nel ridurlo in modo significativo. I medesimi substrati sono stati poi impiegati per misure SERS quantitative di PER: nonostante barre di errore abbastanza ampie, dovute principalmente alla scarsa ripetibilità inter-substrato, è stata osservata una correlazione lineare tra l’altezza media dei picchi e la concentrazione di PER. Considerando il secondo analita, substrati d’argento prodotti mediante centrifugazione sono stati testati con una soluzione di CBD 10-4 M, sebbene gli spettri finali, anche dopo l’aggiunta di MgCl2 come agente complessante e intensificante, sono risultati abbastanza insoddisfacenti. Infine, l’ultimo capitolo è dedicato ai substrati preparati attraverso riduzione in situ di argento sui supporti di carta. Il PER è stato distintamente rilevato sui substrati prodotti con citrato di trisodio (TSC) come agente riducente, mentre il contenuto d’argento in assenza di TSC era basso, causando proprietà SERS insufficienti. I risultati finali hanno evidenziato le potenzialità di sensori di carta preparati in modo rapido e semplice nel rilevamento SERS di specifici analiti, aprendo la strada a sviluppi e ottimizzazioni futuri.
Development of paper-based SERS sensors for the detection of drugs
Macrelli, Andrea
2019/2020
Abstract
My Master's thesis was aimed at developing and testing paper-based SERS sensors for the detection and quantification of selected examples of anti-epileptic drugs, namely Perampanel (PER) and Cannabidiol (CBD). Properly prepared filter-paper supports were loaded with silver or gold nanoparticles by means of simple, rapid and inexpensive techniques, such as dip-coating with colloidal dispersions and in situ reduction of a metallic precursor, and the dipping procedure was further accelerated by the use of a centrifuge. Both the colloids and the final substrates were characterized by UV-VIS-NIR spectroscopy and the nanostructured morphology was investigated with scanning electron microscopy (SEM). Silver substrates produced by dip-coating (via both natural sedimentation and centrifugation) were tested using acidified PER solutions in a concentration range between 10-4 M and 10-6 M and SERS measurements were carried out using the 632.8 nm excitation and adopting the spinning-cell setup to overcome the problem of spatial non-uniformity. At the same time, the relevant problem of the strong contribution originating from the background was addressed and chloride-containing solutions proved to be effective in significantly reducing the background. The same substrates were employed for quantitative SERS measurements of PER; despite quite large error bars, arising primarily from the poor inter-sample repeatability, a linear correlation between the average peak height and the PER concentration was observed. Moving to the second analyte, silver substrates produced via centrifugation were tested with a 10-4 M solution of CBD, although the final spectra, even upon the addition of the complexing and enhancing agent MgCl2, were quite unsatisfactory. Finally, the last chapter is devoted to substrates prepared by in situ reduction of silver onto paper supports. PER was clearly detected on substrates produced with trisodium citrate (TSC) as reducing agent, whereas the silver content in the absence of TSC was low, resulting in poor SERS properties. The final results highlighted the potential of rapidly and easily prepared paper-made sensors for the SERS detection of specific analytes, paving the way for future development and optimization.| File | Dimensione | Formato | |
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2020_12_Macrelli.pdf
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https://hdl.handle.net/10589/171368