Total Luminescence Spectroscopy for Quantification of Temperature Effects on Photophysical Properties of Photoluminescent Materials

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

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.

Effects of Cascading Optical Processes: Part II: Impacts on Experimental Quantification of Sample Absorption and Scattering Properties

In Part I of the three companion articles, we reported the effects of light scattering on experimental quantification of scattering extinction, intensity, and depolarization in solutions that contain only scatterers with no significant absorption and photoluminescence activities. The present work (Part II) studies the effects of light scattering and absorption on a series of optical spectroscopic measurements done on samples that contain both absorbers and scatterers, but not emitters. The experimental UV-vis spectrum is the sum of the sample absorption and scattering extinction spectra. However, the upper limit of the experimental Beer's-law-abiding extinction can be limited prematurely by the interference of forward scattered light. Light absorption reduces not only the sample scattering intensity but also the scattering depolarization. The impact of scattering on sample light absorption is complicated, depending on whether the absorption of scattered light is taken into consideration. Scattering reduces light absorption along the optical path length from the excitation source to the UV-vis detector. However, the absorption of the scattered light can be adequate to compensate the reduced light absorption along such optical path, making the impacts of light scattering on the sample total light absorption negligibly small (<10%). The latter finding constitutes a critical validation of the integrating-sphere-assisted resonance synchronous spectroscopic method for experimental quantification of absorption and scattering contribution to the sample UV-vis extinction spectra. The techniques and general guidelines provided in this work should help improve the reliability of optical spectroscopic characterization of nanoscale or larger materials, many of which are simultaneous absorbers and scatterers. The insights from this work are foundational for Part III of this series of work, which is on the cascading optical processes on spectroscopic measurements of fluorescent samples.