Graphene Nanodots as Substrates for SEIRAS and SERS Studies on Membrane Proteins Ariadna Murillo-Bello, Antonio Gaetano Ricciardulli, Abdul Rehman Umar, Tatjana Gerasimova, Thorsten Friedrich, Nicolas Javahiraly, Paolo Samorì, Petra Hellwig Langmuir, 2025 Graphene nanostructures are capable of supporting plasmonic resonances in the visible and infrared parts of the spectrum. Thus, they can be exploited as platforms for Surface-Enhanced Infrared Absorption Spectroscopy (SEIRAS) and Surface-Enhanced Raman Spectroscopy (SERS) studies. One application of SEIRAS and SERS is the study of proteins at very low concentrations, down to the picomolar range. Among the different forms of graphene, graphene nanodots are ideal nanostructures that can be produced on a large scale using established protocols relying on sonication-assisted exfoliation under specific experimental conditions. Their rich surface chemistry facilitates stable and nondenaturing adsorption of membrane proteins, ensuring preservation of their native secondary structure upon immobilization. In this study, we exploited graphene nanodots deposited by drop casting or spray coating onto a silicon wafer as a substrate to study the cytochrome bd-I oxidase fromE. coli, a membrane protein that is present in the respiratory chains of bacteria. The amide I signal was examined to confirm the structural integrity of the protein once immobilized onto the graphene nanodots. SEIRAS and SERS experiments revealed reproducible enhancement of the protein signal, approximately by a factor of 2 and 6-10 compared to other substrates, respectively, enabling analyte detection with a sensitivity down to the nanomolar range. Furthermore, our tailored substrate exhibited high stability of the protein exceeding 6 days, thus underscoring its high potential for biosensing.
Effective adsorption of Congo red azo dye from different water and wastewater by using porous Fe3O4-bentonite@chitosan nanocomposite: A multivariate optimization Haji Muhammad, Mustafa Tuzen, Asma Siddiqui, Abdul Rehman Umar International Journal of Biological Macromolecules, 2025 In this study, a novel Fe 3 O 4 -Chitosan@Bentonite (Fe 3 O 4 -CS/Bent) nanocomposite was synthesized via a green and scalable co-precipitation method for the efficient adsorption of toxic azo dye Congo Red (CR) from wastewater. To analyze the physicochemical changes in nanocomposite before and after CR adsorption SEM-EDS, FTIR , XRD , BET, and VSM were employed. The results revealed that Fe 3 O 4 -CS/Bent nanocomposite shows significantly enhanced surface area, pore volume , and adsorption capacity compared to pure Fe 3 O 4 NPs , making it highly effective for environmental remediation. Despite its lower magnetization due to non-magnetic additives, it retains superparamagnetic properties that facilitate efficient magnetic separation in water treatment. Furthermore, the mesoporous Fe 3 O 4 -CS/Bent nanocomposite can adsorb CR through electrostatic interactions , hydrogen bondings , and surface interaction under carefully optimized adsorption conditions (pH 5, adsorbent amount of 9 mg, and contact time of 25 min) via multivariate analyses. Subsequently, the adsorption process followed a pseudo-2nd order and Langmuir model, yielding a maximum adsorption capacity of 169 mg/g with 96 % removal efficiency, suggesting a monolayer chemisorption process on a relatively heterogeneous surface. The rate constant was determined to be 0.02 g/g-min suggesting a moderate adsorption rate. Thermodynamic analysis indicated adsorption of CR is spontaneous, exothermic, and feasible at moderate temperatures. Furthermore, Fe 3 O 4 -CS/Bent exhibits outstanding removal efficiencies in recovery experiments, with 98.6–101.4 % recovery across drinking, tap, canal, and wastewater samples. The adsorbent demonstrated excellent reusability , maintaining over 70 % efficiency after 8th regeneration cycle. These findings establish that Fe 3 O 4 -CS/Bent nanocomposite is found to be cost-effective environmentally friendly adsorbent for water treatment methods.
Optimization and multivariate analysis of Schiff Base functionalized gold nanoparticle sensor for efficient bifenthrin detection in food samples SB Anwar, S Yaqoob, S Rasheed, S Ali, AR Umar, K Hussain, N Kousar, ... Food Chemistry, 148687 , 2026 2026
Multivariate optimized poly (3-hydroxybutyrate)-graft-poly (2-ethyl oxazoline)-zinc oxide nanocomposite for high-efficiency malachite green adsorption H Muhammad, M Tuzen, B Hazer, AR Umar Journal of Industrial and Engineering Chemistry 147, 522-534 , 2025 2025 Citations: 15
Graphene nanodots as substrates for SEIRAS and SERS studies on membrane proteins A Murillo-Bello, AG Ricciardulli, AR Umar, T Gerasimova, T Friedrich, ... Langmuir 41 (25), 16468-16476 , 2025 2025 Citations: 3
Effective adsorption of Congo red azo dye from different water and wastewater by using porous Fe3O4-bentonite@ chitosan nanocomposite: A multivariate optimization H Muhammad, M Tuzen, A Siddiqui, AR Umar International Journal of Biological Macromolecules 310, 143439 , 2025 2025 Citations: 31
Smartphone-integrated inkjet-printed paper sensor and UV/Vis spectrophotometric method for on-site detection of As3+ and L-cysteine in food samples using novel AMTPP … S Rasheed, K Hussain, S Arif, AR Umar, SB Anwar, H Muhammad, ... Food Chemistry 464, 141921 , 2025 2025 Citations: 12
Smartphone-Integrated resorcinarene macrocycle capped silver nanoparticles (RMF-AgNPs) probe for enhanced La (III) detection in diverse environments K Hussain, AR Umar, S Rasheed, M Hassan, MH Laiche, H Muhammad, ... Journal of Industrial and Engineering Chemistry 138, 256-269 , 2024 2024 Citations: 7
Electrochemical studies of the cytochrome bd oxidase from the anaerobic sulfate-reducing bacterium Solidesulfovibrio fructosivorans PH Melin, Frederic, Abdul Rehman Umar, Mohamad Najjar, Arlette Kpebe, Myriam ... Biochimica et Biophysica Acta (BBA)-Bioenergetics 1865, 149273 , 2024 2024
Efficient synergistic degradation of Congo red and omeprazole in wastewater using rGO/Ag@ ZnO nanocomposite N Kousar, S Rasheed, K Yasmeen, AR Umar, MH Laiche, M Masood, ... Journal of Water Process Engineering 58, 104775 , 2024 2024 Citations: 18
Ultra-trace level colorimetric composite sensor based on novel DH-1, 6-NAPY-8-CN-AgNPs for the detection of Clonazepam in aqueous and human plasma samples S Ali, AR Umar, K Hussain, H Muhammad, M Hanif, MH Laiche, ... Journal of Industrial and Engineering Chemistry 125, 136-143 , 2023 2023 Citations: 7
Highly selective sub-micromolar level colorimetric sensor for lanthanum detection based on l-tyrosine functionalized silver nanoparticles MAU Haq, K Hussain, Z Aslam, AR Umar, MR Shah, STH Sherazi, J Nisar Microchemical Journal 185, 108289 , 2023 2023 Citations: 16
Ultra-trace level voltammetric sensor for MB in human plasma based on a carboxylic derivative of Calix [4] resorcinarene capped silver nanoparticles AR Umar, K Hussain, Z Aslam, MAU Haq, H Muhammad, MR Shah Journal of Industrial and Engineering Chemistry 107, 81-92 , 2022 2022 Citations: 19
MOST CITED SCHOLAR PUBLICATIONS
Effective adsorption of Congo red azo dye from different water and wastewater by using porous Fe3O4-bentonite@ chitosan nanocomposite: A multivariate optimization H Muhammad, M Tuzen, A Siddiqui, AR Umar International Journal of Biological Macromolecules 310, 143439 , 2025 2025 Citations: 31
Ultra-trace level voltammetric sensor for MB in human plasma based on a carboxylic derivative of Calix [4] resorcinarene capped silver nanoparticles AR Umar, K Hussain, Z Aslam, MAU Haq, H Muhammad, MR Shah Journal of Industrial and Engineering Chemistry 107, 81-92 , 2022 2022 Citations: 19
Efficient synergistic degradation of Congo red and omeprazole in wastewater using rGO/Ag@ ZnO nanocomposite N Kousar, S Rasheed, K Yasmeen, AR Umar, MH Laiche, M Masood, ... Journal of Water Process Engineering 58, 104775 , 2024 2024 Citations: 18
Highly selective sub-micromolar level colorimetric sensor for lanthanum detection based on l-tyrosine functionalized silver nanoparticles MAU Haq, K Hussain, Z Aslam, AR Umar, MR Shah, STH Sherazi, J Nisar Microchemical Journal 185, 108289 , 2023 2023 Citations: 16
Multivariate optimized poly (3-hydroxybutyrate)-graft-poly (2-ethyl oxazoline)-zinc oxide nanocomposite for high-efficiency malachite green adsorption H Muhammad, M Tuzen, B Hazer, AR Umar Journal of Industrial and Engineering Chemistry 147, 522-534 , 2025 2025 Citations: 15
Smartphone-integrated inkjet-printed paper sensor and UV/Vis spectrophotometric method for on-site detection of As3+ and L-cysteine in food samples using novel AMTPP … S Rasheed, K Hussain, S Arif, AR Umar, SB Anwar, H Muhammad, ... Food Chemistry 464, 141921 , 2025 2025 Citations: 12
Smartphone-Integrated resorcinarene macrocycle capped silver nanoparticles (RMF-AgNPs) probe for enhanced La (III) detection in diverse environments K Hussain, AR Umar, S Rasheed, M Hassan, MH Laiche, H Muhammad, ... Journal of Industrial and Engineering Chemistry 138, 256-269 , 2024 2024 Citations: 7
Ultra-trace level colorimetric composite sensor based on novel DH-1, 6-NAPY-8-CN-AgNPs for the detection of Clonazepam in aqueous and human plasma samples S Ali, AR Umar, K Hussain, H Muhammad, M Hanif, MH Laiche, ... Journal of Industrial and Engineering Chemistry 125, 136-143 , 2023 2023 Citations: 7
Graphene nanodots as substrates for SEIRAS and SERS studies on membrane proteins A Murillo-Bello, AG Ricciardulli, AR Umar, T Gerasimova, T Friedrich, ... Langmuir 41 (25), 16468-16476 , 2025 2025 Citations: 3
Optimization and multivariate analysis of Schiff Base functionalized gold nanoparticle sensor for efficient bifenthrin detection in food samples SB Anwar, S Yaqoob, S Rasheed, S Ali, AR Umar, K Hussain, N Kousar, ... Food Chemistry, 148687 , 2026 2026
Electrochemical studies of the cytochrome bd oxidase from the anaerobic sulfate-reducing bacterium Solidesulfovibrio fructosivorans PH Melin, Frederic, Abdul Rehman Umar, Mohamad Najjar, Arlette Kpebe, Myriam ... Biochimica et Biophysica Acta (BBA)-Bioenergetics 1865, 149273 , 2024 2024
