High-Sensitivity Metal Oxide Sensors Duplex for On-the-Field Detection of Acetic Acid Arising from the Degradation of Cellulose Acetate-Based Cinematographic and Photographic Films

Daniele Zappi,Igor Iatsunskyi,Gabriele Varani,Maria Teresa Giardi,Nadja Wallaszkovits,Josef Bailer

doi:10.3390/chemosensors10020060

Abstract

In this work, a system consisting of two resistive sensors working in tandem to detect and quantify the acetic acid released during the degradation of cellulose acetate-based ancient cinematographic and photographic films is presented. Acetic acid must be constantly monitored to prevent reaching concentrations at which autocatalytic degradation processes begin. The sensors are constituted by a thin layer of metal oxide (tungsten oxide and tin oxide) deposited over an interdigitated electrode capable of being heated, chosen to maximize the array response towards acetic acid vapors. The signals obtained from the sensor array are mathematically processed to reduce the background signal due to interferent gases produced during degradation of ancient cinematographic films. The sensor array reported a LOD of 30 ppb for acetic acid, with a linearity range up to 30 ppm. Finally, the sensor array was tested with different cinematographic and photographic film samples made of cellulose acetate, whose degradation state and acetic acid production was validated using the conventional technique (A-D strips). The presented array is suitable for remote monitoring large number of films in collections since, compared to the official technique, it has a lower detection limit (30 ppb vs. 500 ppb) and is much quicker in providing accurate acetic acid concentration in the film boxes (15 min vs. 24 h).

Highlights

Cultural heritage (CH) preservation is nowadays understood as a two-phase action: on one hand, it consists of restoring and recovering damaged CH elements; on the other hand, increasing attention is directed to monitoring the parameters responsible for the CH artifacts’ degradation.A new emerging problem in CH preservation regards the phenomena of degradation caused by compounds produced by the CH items themselves
We present an alternative, innovative solution for monitoring the conditions of cellulose-based films by quantifying the acetic acid released during degradation
Real-time estimation of the amount of acetic acid accumulating during cellulose acetate films degradation, it was necessary firstly to identify the most common species released by the film during the degradation process

Summary

Introduction

Cultural heritage (CH) preservation is nowadays understood as a two-phase action: on one hand, it consists of restoring and recovering damaged CH elements; on the other hand, increasing attention is directed to monitoring the parameters responsible for the CH artifacts’ degradation. A new emerging problem in CH preservation regards the phenomena of degradation caused by compounds produced by the CH items themselves. This problem is complicated for numerous factors: compounds to be monitored depend on the nature of the CH item [1,2,3]. Even objects of the same general type may produce different compounds depending on specific previous treatments and restorations performed on them.

Methods

Results

Discussion

Conclusion