An Ultraviolet Spectroscopic Method for Monitoring Surface Acidity of Clay Minerals under Varying Water Content

Bailey, George W.

doi:10.1346/ccmn.1973.0210607

Cited by 15 publications

(10 citation statements)

References 30 publications

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“…16,18,30 The peak at 371 nm may also be contributed by phenazine. 31 Hence, from the UV-Vis and FTIR results, case (A) samples should be composed of the phenazine-like AN oligomers with some substituted quinones. 14,16,18,30 For case (B), the shape of the spectrum is similar to that obtained from case (A), except that a shifted band at 361 nm (from 371 nm) and a weak broad band B614 nm are observed, which are caused by the para-coupled branches growing from the phenazine-like structures.…”

Section: Uv-vis Resultsmentioning

confidence: 99%

Polymerization of aniline under various concentrations of APS and HCl

Tang

Wang

Lin

et al. 2011

Polym J

103

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Effects from various initial molar ratios of aniline (AN), ammonium peroxydisulfate (APS) and HCl ( [AN]: [APS]: [HCl]) on the polymerization of AN were investigated. First, a scheme derived from a molecular point of view was proposed to distinguish formation mechanisms based on their initial conditions. Thereafter, by choosing a relatively low ratio of Keywords: aniline; formation mechanism; phenazine-like oligomers; polyaniline INTRODUCTION Polyaniline (PANI) is one of the most important conducting and semi-conducting polymers widely used in organic optoelectronic devices and has attracted considerable attention recently because of its tunable electrical conductivity, easy preparation from common chemicals and excellent thermal and environmental stabilities. 1,2 The electrical properties of PANI are sensitively dependent on its oxidation and protonation states, of which the emeraldine state (see Figure 1) with a wide range of electrical conductivity can be achieved by simple doping/dedoping chemistry based on acidic/basic reactions. 1-3 The conventional chemical oxidative polymerization of aniline (AN) is carried out in a strong acidic solution and initiated by adding an oxidant (such as ammonium peroxydisulfate, APS). 3 From a technical point of view, the above-mentioned preparation for PANI is a simple process, but the formation mechanism involves an intricate interplay of consecutive chemical and physical reactions. [3][4][5][6][7][8][9][10][11][12] To account for the formation of PANI, the following basic mechanisms were reported. The redox reaction of neutral ANs with APS produces AN radicals. 4 Under a neutral or alkaline condition, the mixed ortho-para coupling of AN radicals together with oxidative intramolecular cyclization forms AN oligomers with phenazine-like structures at the initial stage (see Figures 2a and b for phenazine and phenazine-like trimer). 9-13 The oxidation of AN and AN oligomers with APS both release protons, and the pH of the solution falls. [12][13][14][15][16][17][18][19][20] In a strong acidic environment, the formation of a para-coupled structure

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Section: Uv-vis Resultsmentioning

confidence: 99%

Polymerization of aniline under various concentrations of APS and HCl

Tang

Wang

Lin

et al. 2011

Polym J

103

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“…A nitrogen (99.999%) purge was maintained while transferring the cuvette from the desiccator to the UV-visible spectrophotometer to minimize any contamination of surface acidity. Bailey and Karickhoff (1973) found that the presence of CO2 influenced the final surface acidity value, so care was taken to exclude CO2 as well as O2.…”

Section: Iron-bearing Minerals-indicator Filmsmentioning

confidence: 99%

“…The concept of employing molecular probes serving as indicators and UV-visible spectroscopy to investigate surface properties of mineral surfaces was proposed by Bailey and Karickhoff (1973) and Karickhoff and Bailey (1976). They investigated the interaction of various organic bases and basic pesticides with clay mineral surfaces, and monitored the protonation of these indicators of basic organic compounds at the mineral surfaces under varying water contents by UV-visible spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

“…They investigated the interaction of various organic bases and basic pesticides with clay mineral surfaces, and monitored the protonation of these indicators of basic organic compounds at the mineral surfaces under varying water contents by UV-visible spectroscopy. UV-visible spectroscopy has several advantages over other methods (Bailey and Karickhoff 1973) in that: 1) it can measure protonation in situ, in suspension as well as films and slurries; and 2) it is very sensitive. Low levels of indicator loadings, for example <0.1% of cation exchange capacity for t Current address: Equifax, Inc., Decision Systems, External Maildrop 425, 1525 Windward Concourse, Alpharetta, Georgia 30202. some indicator-mineral systems, can be quantitatively and reproducibly monitored.…”

Section: Introductionmentioning

confidence: 99%

“…Organic molecules whose protonated and unprotonated forms (acidity), oxidized and reduced forms (redox capacity) can serve as such monitors if these forms are spectroscopically different (Bailey and Karickhoff 1973 employed a UV-visible method for monitoring the surface acidity of clay minerals. They reported that this method could measure protonation in situ under wet or dry conditions and was very sensitive.…”

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confidence: 99%

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Redox Characterization of the Surfaces of Seven Iron-Bearing Minerals: Use of Molecular Probes and UV-Visible Spectroscopy

Bailey

1996

Clays and clay miner.

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Abstract--Redox properties of iron-bearing mineral surfaces may play an important role in controlling the transport and transformation of pollutants into ground waters. Suspensions of seven iron-bearing minerals were reacted with pH and redox indicators under anaerobic conditions at the pH of the natural suspension. The responses of the indicators to the mineral surfaces were monitored by UV-visible spectroscopy using a scattered transmission technique. The Hammett surface acidity function (H~) and the surface redox potential (Eh~) of these iron-bearing minerals were measured. These measured values were used to calculate Eh values for the seven minerals: goethite = +293 mV; chlorite = +290 mV; hematite = +290 mV; almandite = +282 mV; ferruginous smectite = +275 mV; pyrite = +235 mV; and Na-vermiculite = +223 mV. Calculated surface redox potentials of minerals are different from their potentials measured by platinum electrode in bulk suspensions. UV-visible spectroscopy provides a quick and nondestructive way of monitoring organic probe response at the mineral surface.

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Adsorchromism: Molecular Nanoarchitectonics at 2D Nanosheets—Old Chemistry for Advanced Chromism

et al. 2021

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Chromism induced by changes in the electronic states of dye molecules due to surface adsorption is termed "adsorchromism" in this article. These changes of molecular electronic states are induced by protonation, aggregation, intramolecular structural changes, and other processes, depending on the surface environment. Intramolecular structural changes, such as co-planarization and decreased molecular motion are the most characteristic and interesting behavior of dye molecules at the surfaces, resulting in spectral shift and/or emission enhancement. In this review, adsorchromism at the surfaces of layered materials are summarized since their flexibility of interlayer distance, surface flatness, and transparency is suitable for a detailed observation. By understanding the relationship between adsorchromism and the electronic states of molecules on the surfaces, it will be possible to induce some desired functions which can be realized simply by adsorption, instead of complicated organic syntheses. Thus, adsorchromism has potential applications such as effective solar energy harvesting systems, or biological/chemical sensors to visualize environmental changes.

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An Ultraviolet Spectroscopic Method for Monitoring Surface Acidity of Clay Minerals under Varying Water Content

Cited by 15 publications

References 30 publications

Polymerization of aniline under various concentrations of APS and HCl

Polymerization of aniline under various concentrations of APS and HCl

Redox Characterization of the Surfaces of Seven Iron-Bearing Minerals: Use of Molecular Probes and UV-Visible Spectroscopy

Adsorchromism: Molecular Nanoarchitectonics at 2D Nanosheets—Old Chemistry for Advanced Chromism

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