Surfactant-induced alterations in optoelectronic properties of perylene diimide dyes: modulating sensing responses in the aqueous environment.

The compartmentalization effect of microheterogeneous systems, like surfactant aggregates, showcases altered optoelectronic properties of a perylene diimide-based chromogenic dye (PDI-Ala) compared to bulk water. The relatively hydrophobic microenvironment, poor hydration, and exceptionally large local concentration of dye molecules in the confined environment affect their interaction with target analytes. This realization intrigued us to investigate if micellization can modify the sensing properties (selectivity, sensitivity, response kinetics, output signal, etc.) of the encapsulated dye molecules in the aqueous medium. Response comparisons of PDI-Ala to the ionic analyte (Fe3+) and biomolecule (heparin) in aqueous and surfactant-bound states highlighted significant variations. Fe3+ interaction exhibited a "turn-off" fluorescence response in a water medium, while surfactant-bound conditions triggered "turn-on" fluorescence, enhancing selectivity at the micelle-water interface. Conversely, the native probe showed no interaction with heparin in water but displayed a turn-on fluorescence response in cetyltrimethylammonium bromide (CTAB) micelles, indicating the transformation of a silent molecule into a turn-on fluorescence sensor. This study underscores the influence of micellar environments on dye molecules, altering the sensing responses and selectivity toward analytes, crucial for applications in understanding cellular pathways and toxicity mechanisms.

Tuning sensing efficacy of anthraimidazoledione-based charge transfer dyes: nitro group positioning impact.

Anthraimidazoledione-based optical sensors have been designed by varying the position of the nitro functional group. All three positional isomers showed highly colored, photostable optical signals owing to intramolecular charge transfer interactions. Despite having the same anion-binding site (imidazole unit), the selectivity and sensitivity of the compounds depend on the positioning of the nitro group. The selectivity was fairly good for the meta isomer, followed by the ortho and para isomers, respectively. In contrast, the sensitivity towards anions followed a completely opposite trend, with the para isomer being the most sensitive one towards anions. Interestingly, the color changing response along the turn-on fluorescence signal was observed only with CN- ions in a semi-aqueous environment. Though the introduction of water as a co-solvent could improve the selectivity, the sensitivity was found to be slightly less than that observed in pure organic medium. Mechanistic studies indicated hydrogen bonding interactions between the imidazole -NH proton and cyanide, which further facilitated the extent of intramolecular charge transfer.

Oxidized Bisindolyl-Based Amphiphilic Probe for Dual Mode Analysis of Heavy Metal Pollutants in Aqueous Medium.

The oxidized bisindolyl-based amphiphilic, chromogenic probe has been synthesized that can form nanoscopic aggregates in the aqueous medium. Along with solvent polarity and pH of the medium, it was observed that the addition of heavy metal pollutants, like Hg2+ can cause significant alteration in the charge transfer state. This resulted in the immediate change in the solution color from yellow to orange. Additionally, we could excite either the monomer species or the aggregates of the probe by choosing the proper excitation wavelength. Upon exciting at 390 nm, the compound exhibited a broad fluorescence spectrum with maxima at 450 nm, presumably due to twisted state charge transfer. On the contrary, the aggregated species (λex = 465 nm) displayed a comparatively weaker fluorescence band centered at 565 nm. Interestingly, the fluorescence intensity at the 450 nm band experience fluorescence quenching in the presence of Hg2+ ion, while the aggregate emission band remained unaffected. Finally, the present system was utilized for detection of mercury ions in natural water samples.

Measurement and risk perception of non-ionizing radiation from base transceiver stations in Dhaka City of Bangladesh.

Multiple harmful health effects can have on the population from non-ionizing radiation (NIR) sources. To date, there has been no extensive data collection about NIR emitted from base transceiver stations in Dhaka City, Bangladesh. This study aims to remedy that by collecting data and comparing the processed data to the international standards, International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines, and standards of other countries. For this, measurement data were collected from 361 different publicly accessible locations in Dhaka City applying a convenience sampling approach. The measured average electric field exceeded the 1800 MHz threshold values of 36.84, 33.5, and 7.5% of the time compared with the thresholds of China, India, and Japan, respectively, followed by the measured average electromagnetic field values, which were 57, 52, and 29%, respectively. No exceedance was seen for radiofrequency power flux for the investigated countries. Approximately 35% of the calculated average specific energy absorption rate values exceeded the ICNIRP recommended public exposure limit of 0.08 W/kg. Based on this data, it is suggested that detailed NIR exposure regulations need to be created and proper oversight and enforcement over operators are required to avoid potential health effects.

A Critical Review of the Removal of Radionuclides from Wastewater Employing Activated Carbon as an Adsorbent.

Radionuclide-contaminated water is carcinogenic and poses numerous severe health risks and environmental dangers. The activated carbon (AC)-based adsorption technique has great potential for treating radionuclide-contaminated water due to its simple design, high efficiency, wide pH range, quickness, low cost and environmental friendliness. This critical review first provides a brief overview of the concerned radionuclides with their associated health hazards as well as different removal techniques and their efficacy of removing them. Following this overview, this study summarizes the surface characteristics and adsorption capabilities of AC derived from different biomass precursors. It compares the adsorption performance of AC to other adsorbents, such as zeolite, graphene, carbon nano-tubes and metal-organic frameworks. Furthermore, this study highlights the different factors that influence the physical characteristics of AC and adsorption capacity, including contact time, solution pH, initial concentration of radionuclides, the initial dosage of the adsorbent, and adsorption temperature. The theoretical models of adsorption isotherm and kinetics, along with their fitting parameter values for AC/radionuclide pairs, are also reviewed. Finally, the modification procedures of pristine AC, factors determining AC characteristics and the impact of modifying agents on the adsorption ability of AC are elucidated in this study; therefore, further research and development can be promoted for designing a highly efficient and practical adsorption-based radionuclide removal system.

A critical overview of adsorption kinetics for cooling and refrigeration systems.

The dynamic uptake of adsorbate onto the porous adsorbent plays a crucial role in determining the performance of the adsorption-based cooling system. Therefore, it is imperative to know the kinetics parameters of an adsorbate - adsorbent pair to design a system to be operated at variable working conditions. The kinetics models of adsorption, used to simulate the adsorption rate of different pairs, are derived and presented in this paper. Besides, the limitations and advantages of the models are also mentioned. Moreover, the dynamic performance of different adsorption pairs is analyzed, and the values of kinetics parameters, determined through experimental procedures and fitting of kinetics models, are also summarized. It is opined that during the initial unsaturated condition of adsorption, the semi-infinite model can be preferred to determine the diffusion time constant. The modification of different models, e.g., Langmuir and linear driving force models, can significantly overcome the drawbacks of the models, as shown by several researchers. However, research may be carried out to investigate different models' fitting errors from a statistical perspective. Furthermore, to evaluate the dynamic performance of different adsorbates, a lot of research needs to be done, specifically, on the adsorption of the newly developed environment-friendly refrigerants, onto the promising composite adsorbents possessing high thermal conductivity and significantly improved adsorption uptakes.

Statistical techniques for the optimization of cesium removal from aqueous solutions onto iron-based nanoparticle-zeolite composites.

Statistical optimization of performance determining factors is essential for the development of a cesium removal system from aqueous solutions. Therefore, factorial experimental design and multiple regression techniques were employed to assess the primary and interaction effects of the pH, initial concentration, and contact time in the cesium removal process using nanoscale zero-valent iron-zeolite (nZVI-Z) and nano-Fe/Cu-zeolite (nFe/Cu-Z) as an adsorbent. The optimum region of cesium removal was identified by constructing a contour plot. The study revealed that initial concentration was the most significant factor followed by contact time. The study also suggested that maximum cesium removal occurred at pH, initial concentration, and contact time of 6, 200 mg/L, and 30 min, respectively. Moreover, the statistically significant interaction effect was observed between contact time and initial concentration. The experimental data were also fitted with Tόth, Langmuir, Dubinin-Astakhov (D-A), Freundlich, and Hill models and found that the Tόth model fitted better compared with the other four models based on Akaike information criterion (AIC) and root-mean-square deviation (RMSD). The findings of this paper can undoubtedly contribute to constructing the optimum statistical process of removing hazardous pollutants from the water, which significantly impacts on human health and the environment. Graphical abstract.

Is the Use of Antimicrobial Photodynamic Therapy or Systemic Antibiotics More Effective in Improving Periodontal Health When Used in Conjunction with Localised Non-Surgical Periodontal Therapy? A Systematic Review.

Periodontal disease can be treated in several ways. This paper reviewed whether antimicrobial photodynamic therapy (aPDT) in addition to scaling and root planing (SRP) produces improved clinical results over systemic antibiotics (ABs) in conjunction with SRP in adults with periodontitis. Studies were searched using the following electronic databases: MEDLINE, the Cochrane Database of Systematic Reviews, and the Web of Science Core Collection up to and including November 2018. Four randomized controlled trials (RCTs) were reviewed to maximise the reliability of the evidence. All participants suffered from either chronic or aggressive periodontitis and each study contained SRP as an adjunct to ABs or aPDT. To determine whether groups showed improvement after treatment, the outcome parameters chosen were probing depth (PD), clinical attachment level (CAL), and bleeding on probing (BOP). Despite finding significant improvements in all groups, the differences among groups were not consistently statistically significant. The lack of homogeneity in the results among these studies indicates that it was not possible to determine a conclusion about whether aPDT or AB as an adjunct to SRP provides better improvements in periodontitis as measured by PD, CAL, and BOP. Further studies with more similar study designs are required before firm conclusions can be deduced.