Emmanuel Karungani Simiyu

@maseno.ac.ke

Msc student, Department of Physics and Material Science
Maseno University

Emmanuel Karungani Simiyu


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https://researchid.co/karungani

RESEARCH, TEACHING, or OTHER INTERESTS

Materials Science, Organic Chemistry, Condensed Matter Physics, Chemistry
3

Scopus Publications

4

Scholar Citations

2

Scholar h-index

Scopus Publications

  • Synthesis and Solvatochromic Photophysics of Novel Benzanthrone-Based Schiff Base and Amine Derivatives for Next-Generation Optoelectronic and Photovoltaic Applications
    Emmanuel Karungani, Jeļena Kirilova, Titus Ochodo, Mildred Airo, Francis Otieno
    Journal of Chemistry, 2026
    The rational design of organic chromophores with tunable photophysical and charge transfer properties is a key strategy for advancing next‐generation optoelectronic and photovoltaic (PV) applications. In this work, we report the synthesis and detailed characterization of two novel benzanthrone derivatives: the Schiff base 2‐bromo‐3‐[N‐(4‐methoxybenzylidene)amino]benzo[de]anthracen‐7‐one (EK1) and its reduced secondary amine analog 2‐bromo‐3‐[N‐(4‐methoxybenzyl)amino]benzo[de]anthracen‐7‐one (EK2). Structural confirmation was achieved using FTIR, MS, HRMS, NMR, and UV–vis spectroscopy. Their photophysical, solvatochromic, and excited‐state behaviors were systematically evaluated in eight solvents spanning a wide polarity range. EK1 exhibited higher molar absorptivity, wider bandgap, and significantly larger Stokes shifts, reflecting strong intramolecular charge transfer (ICT) enabled by its rigid, conjugated C=N linkage. In contrast, EK2 displayed redshifted absorption and emission maxima due to enhanced donor–acceptor interactions and a narrower HOMO–LUMO gap, while producing narrower emission profiles and reduced Stokes shifts associated with its more flexible–NH–functionality. These contrasting trends reveal clear structure–property relationships that demonstrate how imine‐to‐amine conversion regulates ICT strength, excited‐state stabilization, and solvent‐dependent fluorescence response. The pronounced solvatochromism, tunable visible‐range emission, and strong environment sensitivity exhibited by both derivatives underscore their promise as versatile fluorophores for applications in chemical sensing, spectral conversion layers, fluorescence imaging, and energy‐efficient optoelectronic devices.
  • Processing-directed optimization of gold nanoparticles—poly(3-hexylthiophene) composites for high-performance hole transport layers in organic photovoltaics
    Titus Ochodo, Emmanuel Karungani, Ivy Ambonya, Austine Amukayia Mulama, Francis Otieno
    Aip Advances, 2025
    Organic photovoltaics (OPVs) are attractive for their flexibility, light weight, and scalability. Poly(3-hexylthiophene) (P3HT) is widely used as a hole transport layer due to its stability and device compatibility, but its weak absorption and limited charge transfer reduce efficiency. Embedding gold nanoparticles (Au NPs) into P3HT can address these issues by exploiting localized surface plasmon resonance (LSPR) to enhance light–matter interactions. In this study, P3HT:Au NP thin films were spin coated at 1000–4000 rpm for 30 s, systematically varying P3HT and Au NP concentrations. Optimal films were formed at 1000 and 2000 rpm, where lower speeds yielded thicker, more absorptive films. The 75% Au NP in 25% P3HT showed the highest absorption; at 1000 rpm, it displayed a 42% increase over pristine P3HT due to plasmonic enhancement and greater thickness. The optical bandgap varied with composition and spin speed, increasing at higher speeds as thinner films reduced intermolecular interactions. Extinction coefficients indicated enhanced photon harvesting from NP-driven LSPR. Scanning electron microscopy revealed uniform Au NP dispersion at 50% and 75% loadings, with limited aggregation that may promote plasmonic coupling. Surface roughness rose with NP concentration, from 6 nm for pristine P3HT to 37 nm for pristine Au NPs, reflecting the granular morphology of the metallic phase and its role in light scattering. These findings demonstrate that Au NP embedding and spin-speed control serve as complementary levers for tuning optical and morphological properties, enabling scalable strategies for more efficient OPVs.
  • Photoluminescence Dependance of 2-Bromo-3-aminobenzo[de]anthracene-7-one on Solvent Polarity for Potential Applications in Color-Tunable Optoelectronics
    Emmanuel Karungani, Elena Kirilova, Liga Avotina, Aleksandrs Puckins, Sergejs Osipovs, et al.
    Molecules, 2025
    The novel benzanthrone derivative, 2-bromo-3-aminobenzo[de]anthracene-7-one (2-Br-3-NH2BA), was synthesized and extensively characterized to investigate its photophysical behavior in various solvents. It was prepared through selective bromination of 3-aminobenzanthrone using N-bromosuccinimide in dimethylformamide at −20 °C. Featuring a donor–π–acceptor (D–π–A) structure, 2-Br-3-NH2BA exhibits pronounced solvatochromism due to the intramolecular charge transfer (ICT) between the amino donor and the carbonyl acceptor groups. Optical measurements conducted in eight solvents of varying polarity revealed a significant bathochromic shift in both absorption and fluorescence emission, with emission maxima red-shifting by over 110 nm from non-polar to polar environments. Corresponding reductions in the optical band gap energies, as calculated from Tauc plots, further support solvent-induced electronic state modulation. Additionally, quantum yield analysis showed higher fluorescence efficiency in non-polar solvents, while polar solvents induced twisted intramolecular charge transfer (TICT), leading to emission quenching. These findings demonstrate the sensitivity of 2-Br-3-NH2BA to environmental polarity, making it a promising candidate for color-tunable luminescent applications in optoelectronics and sensing. However, further studies in the solid state are required to validate its applicability in device architectures such as OLEDs.

RECENT SCHOLAR PUBLICATIONS

  • Synthesis and Solvatochromic Photophysics of Novel Benzanthrone‐Based Schiff Base and Amine Derivatives for Next‐Generation Optoelectronic and Photovoltaic Applications
    E Karungani, J Kirilova, T Ochodo, M Airo, F Otieno
    Journal of Chemistry 2026 (1), 6375071 , 2026
    2026
    Citations: 2
  • Processing-directed optimization of gold nanoparticles—poly (3-hexylthiophene) composites for high-performance hole transport layers in organic photovoltaics
    T Ochodo, E Karungani, I Ambonya, AA Mulama, F Otieno
    AIP Advances 15 (10) , 2025
    2025
  • Photoluminescence Dependance of 2-Bromo-3-aminobenzo[ de ]anthracene-7-one on Solvent Polarity for Potential Applications in Color-Tunable Optoelectronics
    E Karungani, E Kirilova, L Avotina, A Puckins, S Osipovs, T Ochodo, ...
    Molecules 30 (13), 2677 , 2025
    2025
    Citations: 2
  • Investigating the Effect of Doping Indium (iii) Selenide (In 2 Se 3 ) with Rare Earth Ions Terbium (Tb 3+ ) and Europium (Eu 3+ ) for Potential Spectral Conversion for …
    EK Simiyu
    247th ECS Meeting (May 18-22, 2025) , 2025
    2025

MOST CITED SCHOLAR PUBLICATIONS

  • Synthesis and Solvatochromic Photophysics of Novel Benzanthrone‐Based Schiff Base and Amine Derivatives for Next‐Generation Optoelectronic and Photovoltaic Applications
    E Karungani, J Kirilova, T Ochodo, M Airo, F Otieno
    Journal of Chemistry 2026 (1), 6375071 , 2026
    2026
    Citations: 2
  • Photoluminescence Dependance of 2-Bromo-3-aminobenzo[ de ]anthracene-7-one on Solvent Polarity for Potential Applications in Color-Tunable Optoelectronics
    E Karungani, E Kirilova, L Avotina, A Puckins, S Osipovs, T Ochodo, ...
    Molecules 30 (13), 2677 , 2025
    2025
    Citations: 2
  • Processing-directed optimization of gold nanoparticles—poly (3-hexylthiophene) composites for high-performance hole transport layers in organic photovoltaics
    T Ochodo, E Karungani, I Ambonya, AA Mulama, F Otieno
    AIP Advances 15 (10) , 2025
    2025
  • Investigating the Effect of Doping Indium (iii) Selenide (In 2 Se 3 ) with Rare Earth Ions Terbium (Tb 3+ ) and Europium (Eu 3+ ) for Potential Spectral Conversion for …
    EK Simiyu
    247th ECS Meeting (May 18-22, 2025) , 2025
    2025