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1. Insights into Spectral Distortion and Nonlinearity in UV–Vis and Fluorescence Spectroscopy of Molecular Fluorophore Solutions: Effects of Cascading Optical Processes (Part IV)

   https://doi.org/10.1021/acs.analchem.4c02173  

   Wathudura, Pathum; McEachin, Joshua; Zhang, Dongmao (August 2024, Analytical Chemistry)

   Reproducibility and linearity are crucial benchmarks for any measurement technology. However, UV–vis and fluorescence spectral distortion and nonlinearity are prevalent, even in seemingly simple fluorescent solutions that comprise only one dissolved molecular fluorophore, without exogenous absorbing or scattering species. In this report, we introduce an analytical model for the quantification of fluorescence interference on UV–vis measurements and a conceptual model for mechanistically understanding the impacts of higher-order cascading optical processes on fluorescence measurements. The experimental UV–vis transmittance can be dominated by interfering fluorescence, even for fluorophore solutions with theoretical absorbance values far below the instrument’s linear dynamic range (LDR). Absorption-inner-filter-effect (aIFE) correction drastically improves the fluorescence LDR. However, the efficacy of aIFE correction hinges on two competing factors that strongly depend on the fluorophore’s optical properties: the degree of fluorescence interference in UV–vis and the significance of secondary or higher-order emission triggered by fluorophore absorption of emitted photons. Our research sheds light on the remarkable complexity of cascading optical processes that can occur even in the simplest fluorescent solutions. It emphasizes the necessity of critically evaluating optical spectroscopic measurements of fluorescent solutions to improve the reliability of analyzing and interpreting optical spectra. Moreover, it lays the groundwork for future development of methods capable of handling challenging samples that exceed the capabilities of the current tools. 

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2. Advancing Evidence-Based Data Interpretation in UV−Vis and Fluorescence Analysis for Nanomaterials: An Analytical Chemistry Perspective

   Wamsley, Max; Zou, Shengli; Zhang, Dongmao (November 2023, Analytical chemistry)

   UV–vis spectrophotometry and spectrofluorometry are indispensable tools in education, research, and industrial process controls with widespread applications in nanoscience encompassing diverse nanomaterials and fields. Nevertheless, the prevailing spectroscopic interpretations and analyses often exhibit ambiguity and errors, particularly evident in the nanoscience literature. This analytical chemistry Perspective focuses on fostering evidence-based data interpretation in experimental studies of materials’ UV–vis absorption, scattering, and fluorescence properties. We begin by outlining common issues observed in UV–vis and fluorescence analysis. Subsequently, we provide a summary of recent advances in commercial UV–vis spectrophotometric and spectrofluorometric instruments, emphasizing their potential to enhance scientific rigor in UV–vis and fluorescence analysis. Furthermore, we propose potential avenues for future developments in spectroscopic instrumentation and measurement strategies, aiming to further augment the utility of optical spectroscopy in nano research for samples where optical complexity surpasses existing tools. Through a targeted focus on the critical issues related to UV–vis and fluorescence properties of nanomaterials, this Perspective can serve as a valuable resource for researchers, educators, and practitioners. 

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3. Spectroscopic Study on Pseudomonas Aeruginosa Biofilm in the Presence of the Aptamer-DNA Scaffolded Silver Nanoclusters

   https://doi.org/10.3390/molecules25163631  

   Sengupta, Bidisha; Adhikari, Prakash; Mallet, Esther; Havner, Ronald; and Pradhan, Prabhakar (August 2020, Molecules)

   null (Ed.)

   We report the effectiveness of silver nanocluster (Ag-NC) against the biofilm of Pseudomonas aeruginosa (PA). Two DNA aptamers specific for PA and part of their sequences were chosen as templates for growing the Ag-NC. While circular dichroism (CD) studies determined the presence of secondary structures, UV/Vis absorption, and fluorescence spectroscopic studies confirmed the formation of the fluorescent Ag-NC on the DNA templates. Furthermore, mesoscopic physics-based partial wave spectroscopy (PWS) was used to analyze the backscattered light signal that can detect the degree of nanoscale mass density/refractive index fluctuations to identify the biofilm formation, comparatively among the different aptamers with respect to the control sample. The importance of the secondary structure of the aptamer DNA in targeting, successfully binding with the cells and delivering the Ag-NC, is evidenced by the decrease in disorder strength (Ld) of the Ag-NC treated samples compared to the untreated PA cells, which showed the abundance of higher Ld in the PWS studies. The higher Ld value attributed to the higher mass density fluctuations and the formation of biofilm. We envision this study to open a new avenue in using a powerful optical microscopic technique like PWS in detection, and DNA aptamer enclosed silver nanoclusters to prevent biofilms for opportunist pathogens like Pseudomonas aeruginosa. 

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4. Spectroscopic Study on Pseudomonas Aeruginosa Biofilm in the Presence of the Aptamer-DNA Scaffolded Silver Nanoclusters

   Sengupta, Bidisha; et, al. (August 2020, Molecules)

   null (Ed.)

   We report the effectiveness of silver nanocluster (Ag-NC) against the biofilm of Pseudomonas aeruginosa (PA). Two DNA aptamers specific for PA and part of their sequences were chosen as templates for growing the Ag-NC. While circular dichroism (CD) studies determined the presence of secondary structures, UV/Vis absorption, and fluorescence spectroscopic studies confirmed the formation of the fluorescent Ag-NC on the DNA templates. Furthermore, mesoscopic physics-based partial wave spectroscopy (PWS) was used to analyze the backscattered light signal that can detect the degree of nanoscale mass density/refractive index fluctuations to identify the biofilm formation, comparatively among the different aptamers with respect to the control sample. The importance of the secondary structure of the aptamer DNA in targeting, successfully binding with the cells and delivering the Ag-NC, is evidenced by the decrease in disorder strength (Ld) of the Ag-NC treated samples compared to the untreated PA cells, which showed the abundance of higher Ld in the PWS studies. The higher Ld value attributed to the higher mass density fluctuations and the formation of biofilm. We envision this study to open a new avenue in using a powerful optical microscopic technique like PWS in detection, and DNA aptamer enclosed silver nanoclusters to prevent biofilms for opportunist pathogens like Pseudomonas aeruginosa. 

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5. 1,2,3-Triazoles: Controlled Switches in Logic Gate Applications

   https://doi.org/10.3390/s23157000  

   Ghosh, Debanjana; Atkinson, Austin; Gibson, Jaclyn; Subbaiahgari, Harini; Ming, Weihua; Padgett, Clifford; Aiken, Karelle S.; Landge, Shainaz M. (August 2023, Sensors)

   A 1,2,3-triazole-based chemosensor is used for selective switching in logic gate operations through colorimetric and fluorometric response mechanisms. The molecular probe synthesized via “click chemistry” resulted in a non-fluorescent 1,4-diaryl-1,2,3-triazole with a phenol moiety (PTP). However, upon sensing fluoride, it TURNS ON the molecule’s fluorescence. The TURN-OFF order occurs through fluorescence quenching of the sensor when metal ions, e.g., Cu2+, and Zn2+, are added to the PTP-fluoride ensemble. A detailed characterization using Nuclear Magnetic Resonance (NMR) spectroscopy in a sequential titration study substantiated the photophysical characteristics of PTP through UV-Vis absorption and fluorescence profiles. A combination of fluorescence OFF-ON-OFF sequences provides evidence of 1,2,3-triazoles being controlled switches applicable to multimodal logic operations. The “INH” gate was constructed based on the fluorescence output of PTP when the inputs are F− and Zn2+. The “IMP” and “OR” gates were created on the colorimetric output responses using the probe’s absorption with multiple inputs (F− and Zn2+ or Cu2+). The PTP sensor is the best example of the “Write-Read-Erase-Read” mimic. 

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