Study on the shift of ultraviolet spectra in aqueous solution with variations of the solution concentration

Tong, Angxin; Tang, Xinde; Zhang, Feng; Wang, Bin

doi:10.1016/j.saa.2020.118259

Cited by 35 publications

(12 citation statements)

References 31 publications

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“…Deprotonation on the other hand is expected to have an opposite effect by contracting the spectra and enhancing the absorbances − at least at lower concentrations − as previously observed on other chromogens. 27,28 However, this may decrease the absorbance at higher concentrations of NaOL, since intramolecular charge transfer is increased, 56,57 which was also observed in this study (Figure 5). As explained above, the introduction of acids (H + ) in the system will displace the equilibrium of oleic acid dissociation toward the formation of the molecular form (since it is a weak acid), while the introduction of bases tends to deprotonate the solution and prevents the formation of molecular oleic acid.…”

Section: Influence Of Ph Regulators On the Naol Uv Spectrasupporting

confidence: 68%

Effect of (De-)protonation on the UV Spectra of Sodium Oleate: Experimental and Electronic Structure Investigation

Murhula

Arellano

Cook

et al. 2023

ACS Appl. Opt. Mater.

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Sodium oleate (NaOL), an anionic surfactant used in mineral processing, is challenging to quantify in aqueous solutions using UV spectroscopy. This study examined ultraviolet spectral shifts of sodium oleate with and without common pH regulators. Experimental results were supported by quantum chemical calculations at the CAM-B3LYP//6–31++G(d,p) level of theory. Two main absorbance peaks appeared in sequence, at 190 and 232 nm, corresponding to the π → π* and the n → π* electronic transitions of the CC double bond and COO– functional group, respectively. Under the typical concentration range used in adsorption and flotation studies, the first peak redshifted to reach λmax = 203 nm at 2 mM NaOL, while both solution deprotonation and protonation resulted in hypo/hyperchromicity. By influencing the electronic environment, acidic and alkaline treatments triggered a broadening and narrowing of the NaOL UV spectra. This difference in behavior was associated with the dissociative equilibrium of oleic acid, where protonation was favorable to molecular species, whereas deprotonation favored the ionic oleate species. The HOMO-LUMO excitation energies were higher in the protonated than in the deprotonated environment, explaining the broader spectra obtained experimentally in the former and higher reactivity in the latter. The peak disruptions give rise to significant discrepancies during quantitative measurements of NaOL in aqueous solutions, which may be managed by appropriate precautions and corrective techniques. These findings can be extended to systems similar to the oleate system and may guide experimental and data-processing procedures in UV spectrometry.

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Section: Influence Of Ph Regulators On the Naol Uv Spectrasupporting

confidence: 68%

Effect of (De-)protonation on the UV Spectra of Sodium Oleate: Experimental and Electronic Structure Investigation

Murhula

Arellano

Cook

et al. 2023

ACS Appl. Opt. Mater.

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“…Moreover, the spectroscopic feature of the PC1 (λ max = 437 nm) was completely restored upon a reverse scan from −1.5 to 0 V (see the SI). From the spectroelectrochemical studies, it is evident that there is a significant overlap between the absorption spectra of PC1 and PC1 •– ; however, upon the formation of PC1 •– , a red shift was observed . From the reversible CV and EPR analysis, it is evident that this PC1 •– is a persistent radical with a sufficient lifetime that allows the PC1 •– to absorb a second photon to generate PC1 •– * using our photochemical setup which helps to transform it into a stronger reductant that can engage in the hydrodehalogenation reaction.…”

Section: Resultsmentioning

confidence: 82%

Transforming Non-innocent Phenalenyl to a Potent Photoreductant: Captivating Reductive Functionalization of Aryl Halides through Visible-Light-Induced Electron Transfer Processes

Pathania

Roy

2022

J. Org. Chem.

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Herein, we have established a phenalenyl-based molecular scaffold which serves as a potent photoreductant utilizing the empty NBMO in the presence of a base to form a radical anion which, upon photoexcitation, behaves as a stronger reductant and accomplishes the cleavage of strong C−X (X = Cl, Br, I) bonds under milder reaction conditions. The base was found to be involved in a dual role of electron and hydrogen atom donor. Further, the aryl radical formed by the homolysis of C−X bonds in this technique was captured for the C sp2 −C sp2 coupling with unactivated arenes. The photoreductant potency of the phenalenylbased catalytic system was further extended to C−P as well as C−B bond formation reactions. EPR and lifetime studies reveal the formation of a persistent radical having a sufficient lifetime to take part in the reaction by the PET mechanism. Different spectroscopic techniques combined with DFT calculations were utilized for the characterization of active catalytic species and for the elucidation of plausible mechanistic pathways. This not only is the initial report of the application of phenalenyl as a photoreductant but also provides a completely metal-free (alkali and transition metal) approach for the challenging reductive functionalization of aryl halides at room temperature.

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“…Because, the remaining captured Na + ions in the modified starch gel, even after washing the stirred solution, leads to creating sodium salt in the drying process which is a super absorber of moisture. [58] In addition, the presence of glycerin in the system enhanced the water absorption of the modified starches, due to its tendency to the water molecules. Another important point is that the increment of the content of modification agents after a particular amount did not influence on the water absorption of the modified starches, and the M value was almost constant beyond that.…”

Section: Hydrophobicity Behavior Of Modified Starchmentioning

confidence: 99%

Thermal Characteristics, Kinetics and Thermodynamics of Thermal Degradation Reaction, and Hydrophobicity of Corn Starch Affected by Chemical and Physical Modifications

2022

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In this work, glacial‐acetic (A) and citric (C) acids from organic acids “family with one and three functional groups, respectively", oleic acid (O) from the fatty acids family and sodium acetate (S) are used for esterification of corn starch in solution in the absence and the presence of 15%wt glycerin as a physical modifier. Discoloration test using CIELAB and as well as thermal gravimetric analysis shows that the glacial‐acetic acid leads to lower reduction in thermal characteristics of the modified starch. The variations of thermal properties start from T > 112 °C, T>136 °C, T>100 °C, and T> 124 °C for the modified starches with C, A, O, and S reagents, respectively, and the changes are constant beyond the amount of 4%wt reagent. The evaluations of kinetics and thermodynamics of thermal degradation reaction for the modified starches via a Coats–Redfern (CR) model prove that the acetic acid causes more activation energy for degradation compared to other reagents. Also, acetic acid‐modified starch demonstrates the highest hydrophobicity among other modified starches – even native starch – in the moisture sorption examination at 75% relative humidity (RH). The results illustrate that glycerin has the worst effect on the thermal and hydrophobicity properties of the modified starches.

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Study on the shift of ultraviolet spectra in aqueous solution with variations of the solution concentration

Cited by 35 publications

References 31 publications

Effect of (De-)protonation on the UV Spectra of Sodium Oleate: Experimental and Electronic Structure Investigation

Effect of (De-)protonation on the UV Spectra of Sodium Oleate: Experimental and Electronic Structure Investigation

Transforming Non-innocent Phenalenyl to a Potent Photoreductant: Captivating Reductive Functionalization of Aryl Halides through Visible-Light-Induced Electron Transfer Processes

Thermal Characteristics, Kinetics and Thermodynamics of Thermal Degradation Reaction, and Hydrophobicity of Corn Starch Affected by Chemical and Physical Modifications

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