Steady-State Fluorescence and Excitation–Emission Matrix Analysis of Sunlight-Assisted Silver Nanoparticle Formation Using Cucurbita pepo Peel Extract
5 affiliations
- 1Department of Physics, College of Science and Humanities in Al-Kharj, Prince Sattam Bin Abdul Aziz University, Al-Kharj 11942, Saudi Arabia
- 2Department of Physics, College of Science, Qassim University, Buraydah, Saudi Arabia
- 3Department of Pharmaceutics, College of Pharmacy, Prince Sattam Bin Abdulaziz University, P.O. Box 173, Al-Kharj 11942, Saudi Arabia
- 4Bioenergy Research Unit, Department of Biophysics, Institute for Research and Medical Consultations, Imam Abdulrahman Bin Faisal University, P.O. Box 1982, Dammam 31441, Saudi Arabia
- 5Department of Chemistry, Faculty of Applied Sciences, Taiz University, Taiz 6803, Yemen
Abstract
Sunlight-assisted plant-mediated synthesis of silver nanoparticles (AgNPs) is well established, yet the complementary use of fluorescence spectroscopy to examine the optical response of complex phytochemical-containing media remains of interest. Here, Cucurbita pepo peel extract (CPE) was used for rapid AgNP formation under natural sunlight using single-step (A-Sun) and dropwise (B-Sun) addition strategies. The characteristic localized surface plasmon resonance (LSPR) band developed near 445–450 nm within 5 min, while corresponding dark controls showed negligible nanoparticle formation over the same period. Both dispersions retained their characteristic LSPR response during six months of optical monitoring. Steady-state photoluminescence (PL) measurements at excitation wavelengths of 300–350 nm and excitation–emission matrix (EEM) fluorescence mapping revealed lower recorded fluorescence intensities in the order CPE > A-Sun > B-Sun, with the principal emission region remaining broadly preserved near 435–440 nm. These observations provide complementary fluorescence fingerprints of the investigated preparations; however, inner-filter effects and light scattering may contribute to the measured attenuation, preventing its exclusive assignment to molecular quenching. FTIR revealed changes in oxygen-containing functional-group vibrations, while TEM showed predominantly spherical to quasi-spherical AgNPs, with mean particle diameters of 11.88 ± 3.60 nm for A-Sun and 9.77 ± 3.43 nm for B-Sun. The resulting dispersions also exhibited antibacterial activity against the six investigated bacterial strains. Overall, integrating PL and EEM with conventional characterization provides additional information on fluorescence changes accompanying sunlight-assisted AgNP formation without directly establishing the individual phytochemical reducing species, electron-transfer steps, or molecular surface-capping mechanisms.
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BibTeX
@article{alhakami2026steadystate,
title = {{Steady-State Fluorescence and Excitation–Emission Matrix Analysis of Sunlight-Assisted Silver Nanoparticle Formation Using Cucurbita pepo Peel Extract}},
author = {Fatehia S. Alhakami and Ashjan M. Alharbi and Aliaa Alrashidi and Mohammed S. Alotaibi and Ehssan Moglad and Nourah A. Albarrak and Afnan A. Alamri and Emre Cevik and Amani M. Alansi and Talal F. Qahtan},
journal = {Nanomaterials},
year = {2026},
month = oct,
doi = {10.3390/nano16211387},
url = {https://www.mdpi.com/2079-4991/16/21/1387},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Steady-State Fluorescence and Excitation–Emission Matrix Analysis of Sunlight-Assisted Silver Nanoparticle Formation Using Cucurbita pepo Peel Extract
AU - Fatehia S. Alhakami
AU - Ashjan M. Alharbi
AU - Aliaa Alrashidi
AU - Mohammed S. Alotaibi
AU - Ehssan Moglad
AU - Nourah A. Albarrak
AU - Afnan A. Alamri
AU - Emre Cevik
AU - Amani M. Alansi
AU - Talal F. Qahtan
PY - 2026
DA - 2026/10/29
JO - Nanomaterials
DO - 10.3390/nano16211387
UR - https://www.mdpi.com/2079-4991/16/21/1387
AB - Sunlight-assisted plant-mediated synthesis of silver nanoparticles (AgNPs) is well established, yet the complementary use of fluorescence spectroscopy to examine the optical response of complex phytochemical-containing media remains of interest. Here, Cucurbita pepo peel extract (CPE) was used for rapid AgNP formation under natural sunlight using single-step (A-Sun) and dropwise (B-Sun) addition strategies. The characteristic localized surface plasmon resonance (LSPR) band developed near 445–450 nm within 5 min, while corresponding dark controls showed negligible nanoparticle formation over the same period. Both dispersions retained their characteristic LSPR response during six months of optical monitoring. Steady-state photoluminescence (PL) measurements at excitation wavelengths of 300–350 nm and excitation–emission matrix (EEM) fluorescence mapping revealed lower recorded fluorescence intensities in the order CPE > A-Sun > B-Sun, with the principal emission region remaining broadly preserved near 435–440 nm. These observations provide complementary fluorescence fingerprints of the investigated preparations; however, inner-filter effects and light scattering may contribute to the measured attenuation, preventing its exclusive assignment to molecular quenching. FTIR revealed changes in oxygen-containing functional-group vibrations, while TEM showed predominantly spherical to quasi-spherical AgNPs, with mean particle diameters of 11.88 ± 3.60 nm for A-Sun and 9.77 ± 3.43 nm for B-Sun. The resulting dispersions also exhibited antibacterial activity against the six investigated bacterial strains. Overall, integrating PL and EEM with conventional characterization provides additional information on fluorescence changes accompanying sunlight-assisted AgNP formation without directly establishing the individual phytochemical reducing species, electron-transfer steps, or molecular surface-capping mechanisms.
SN - 2079-4991
ER -