In situ, continuous monitoring of the photoinduced superhydrophilic effect: influence of uv-type and ambient atmospheric and droplet composition

A. Mills, M. Crow

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

A controlled-atmosphere chamber, combined with a CCTV system, is used to monitor continuously the change in shape of water droplets on the self-cleaning commercial glass, Activ, and a sol−gel TiO2 substrate during their irradiation with either UVA or UVC light. This system allows the photoinduced superhydrophilic effect (PSH) exhibited by these materials to be studied in real time under a variety of different conditions. UVA was less effective than UVC in terms of PSH for both titania-coated glasses, and plain glass was unaffected by either form of UV irradiation and so showed no PSH activity. With UVA, ozone increased significantly the rate of PSH for both substrates, but had no effect on the wettability of plain glass. For both titania substrates and plain glass, no PSH activity was observed under an O2-free atmosphere. A more detailed study of the PSH effect exhibited by Activ revealed that doping the water droplet with either an electron acceptor (Na2S2O8), electron donor (Na2S2O4), or simple electrolyte (KCl) in the absence of oxygen did not promote PSH. However, when Activ was UV irradiated, while immersed in a deoxygenated KCl solution, prior to testing for PSH activity, only a small change in contact angle was observed, whereas under the same conditions, but using a deoxygenated persulfate-containing immersion solution, it was rendered superhydrophilic. The correlation between organic contaminant removal and surface wetting was also investigated by using thick sol−gel films coated with stearic acid; the destruction of SA was monitored by FTIR and sudden wetting of the surface was seen to coincide with the substantial removal of the organic layer. The results of this work are discussed in the context of the current debate on the underlying cause of PSH.
LanguageEnglish
Pages6009-6016
Number of pages7
JournalJournal of Physical Chemistry C
Volume111
Issue number16
DOIs
Publication statusPublished - 26 Apr 2007

Fingerprint

atmospheric composition
Glass
Monitoring
Wetting
Chemical analysis
Sol-gels
Substrates
Titanium
Irradiation
Closed circuit television systems
plains
glass
Stearic acid
Electrons
Water
Ozone
Electrolytes
Contact angle
Cleaning
wetting

Keywords

  • continuous monitoring
  • photoinduced superhydrophilic effect
  • uv-type
  • ambient atmospheric
  • droplet composition
  • controlled-atmosphere chamber

Cite this

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title = "In situ, continuous monitoring of the photoinduced superhydrophilic effect: influence of uv-type and ambient atmospheric and droplet composition",
abstract = "A controlled-atmosphere chamber, combined with a CCTV system, is used to monitor continuously the change in shape of water droplets on the self-cleaning commercial glass, Activ, and a sol−gel TiO2 substrate during their irradiation with either UVA or UVC light. This system allows the photoinduced superhydrophilic effect (PSH) exhibited by these materials to be studied in real time under a variety of different conditions. UVA was less effective than UVC in terms of PSH for both titania-coated glasses, and plain glass was unaffected by either form of UV irradiation and so showed no PSH activity. With UVA, ozone increased significantly the rate of PSH for both substrates, but had no effect on the wettability of plain glass. For both titania substrates and plain glass, no PSH activity was observed under an O2-free atmosphere. A more detailed study of the PSH effect exhibited by Activ revealed that doping the water droplet with either an electron acceptor (Na2S2O8), electron donor (Na2S2O4), or simple electrolyte (KCl) in the absence of oxygen did not promote PSH. However, when Activ was UV irradiated, while immersed in a deoxygenated KCl solution, prior to testing for PSH activity, only a small change in contact angle was observed, whereas under the same conditions, but using a deoxygenated persulfate-containing immersion solution, it was rendered superhydrophilic. The correlation between organic contaminant removal and surface wetting was also investigated by using thick sol−gel films coated with stearic acid; the destruction of SA was monitored by FTIR and sudden wetting of the surface was seen to coincide with the substantial removal of the organic layer. The results of this work are discussed in the context of the current debate on the underlying cause of PSH.",
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In situ, continuous monitoring of the photoinduced superhydrophilic effect: influence of uv-type and ambient atmospheric and droplet composition. / Mills, A.; Crow, M.

In: Journal of Physical Chemistry C, Vol. 111, No. 16, 26.04.2007, p. 6009-6016.

Research output: Contribution to journalArticle

TY - JOUR

T1 - In situ, continuous monitoring of the photoinduced superhydrophilic effect: influence of uv-type and ambient atmospheric and droplet composition

AU - Mills, A.

AU - Crow, M.

PY - 2007/4/26

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N2 - A controlled-atmosphere chamber, combined with a CCTV system, is used to monitor continuously the change in shape of water droplets on the self-cleaning commercial glass, Activ, and a sol−gel TiO2 substrate during their irradiation with either UVA or UVC light. This system allows the photoinduced superhydrophilic effect (PSH) exhibited by these materials to be studied in real time under a variety of different conditions. UVA was less effective than UVC in terms of PSH for both titania-coated glasses, and plain glass was unaffected by either form of UV irradiation and so showed no PSH activity. With UVA, ozone increased significantly the rate of PSH for both substrates, but had no effect on the wettability of plain glass. For both titania substrates and plain glass, no PSH activity was observed under an O2-free atmosphere. A more detailed study of the PSH effect exhibited by Activ revealed that doping the water droplet with either an electron acceptor (Na2S2O8), electron donor (Na2S2O4), or simple electrolyte (KCl) in the absence of oxygen did not promote PSH. However, when Activ was UV irradiated, while immersed in a deoxygenated KCl solution, prior to testing for PSH activity, only a small change in contact angle was observed, whereas under the same conditions, but using a deoxygenated persulfate-containing immersion solution, it was rendered superhydrophilic. The correlation between organic contaminant removal and surface wetting was also investigated by using thick sol−gel films coated with stearic acid; the destruction of SA was monitored by FTIR and sudden wetting of the surface was seen to coincide with the substantial removal of the organic layer. The results of this work are discussed in the context of the current debate on the underlying cause of PSH.

AB - A controlled-atmosphere chamber, combined with a CCTV system, is used to monitor continuously the change in shape of water droplets on the self-cleaning commercial glass, Activ, and a sol−gel TiO2 substrate during their irradiation with either UVA or UVC light. This system allows the photoinduced superhydrophilic effect (PSH) exhibited by these materials to be studied in real time under a variety of different conditions. UVA was less effective than UVC in terms of PSH for both titania-coated glasses, and plain glass was unaffected by either form of UV irradiation and so showed no PSH activity. With UVA, ozone increased significantly the rate of PSH for both substrates, but had no effect on the wettability of plain glass. For both titania substrates and plain glass, no PSH activity was observed under an O2-free atmosphere. A more detailed study of the PSH effect exhibited by Activ revealed that doping the water droplet with either an electron acceptor (Na2S2O8), electron donor (Na2S2O4), or simple electrolyte (KCl) in the absence of oxygen did not promote PSH. However, when Activ was UV irradiated, while immersed in a deoxygenated KCl solution, prior to testing for PSH activity, only a small change in contact angle was observed, whereas under the same conditions, but using a deoxygenated persulfate-containing immersion solution, it was rendered superhydrophilic. The correlation between organic contaminant removal and surface wetting was also investigated by using thick sol−gel films coated with stearic acid; the destruction of SA was monitored by FTIR and sudden wetting of the surface was seen to coincide with the substantial removal of the organic layer. The results of this work are discussed in the context of the current debate on the underlying cause of PSH.

KW - continuous monitoring

KW - photoinduced superhydrophilic effect

KW - uv-type

KW - ambient atmospheric

KW - droplet composition

KW - controlled-atmosphere chamber

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U2 - 10.1021/jp068327v

DO - 10.1021/jp068327v

M3 - Article

VL - 111

SP - 6009

EP - 6016

JO - Journal of Physical Chemistry C

T2 - Journal of Physical Chemistry C

JF - Journal of Physical Chemistry C

SN - 1932-7447

IS - 16

ER -