Browsing by Author "Eren, Guncem Ozgun"

Now showing 1 - 3 of 3

Citation - WoS: 21
Citation - Scopus: 23
Antibacterial Type-II InP/ZnO Quantum Dots Via Multimodal Reactive Oxygen Species
(Elsevier Science SA, 2024) Khan, Saad Ullah; Eren, Guncem Ozgun; Atac, Nazli; Onal, Asim; Qureshi, Mohammad Haroon; Cooper, Francis Korshe; Nizamoglu, Sedat
The emergence of multidrug-resistant bacteria as a global health threat has necessitated the exploration of alternative treatments to combat bacterial infections. Among these, photocatalytic nanomaterials such as quantum dots (QDs) have shown great promise and type-I QDs have been investigated thus far. In this study, we introduce type-II InP/ZnO core/shell QDs that are ligand-exchanged with a short-chain inorganic sulfide ion (S2-) for antibacterial activity. Interestingly, InP/ZnO QDs simultaneously generate reactive oxygen species (ROS) including hydroxyl (center dot OH) and superoxide (O-2(center dot-) ) radicals, while only O-2(center dot-) radicals can be released by the type-I sulfide-capped InP/ZnS QDs. The optimized nanostructure achieved effective inhibition of Pseudomonas aeruginosa and Escherichia coli bacteria growth to the level of 99.99% and 70.31% under low-intensity green light illumination of 5 mW.cm(-2). Our findings highlight the importance of type-II QDs as a new avenue for developing effective antibacterial agents against drug-resistant pathogens.
Citation - WoS: 28
Citation - Scopus: 25
Quantum Dot and Electron Acceptor Nano-Heterojunction for Photo-Induced Capacitive Charge-Transfer
(Nature Portfolio, 2021) Karatum, Onuralp; Eren, Guncem Ozgun; Melikov, Rustamzhon; Onal, Asim; Ow-Yang, Cleva W.; Sahin, Mehmet; Nizamoglu, Sedat
Capacitive charge transfer at the electrode/electrolyte interface is a biocompatible mechanism for the stimulation of neurons. Although quantum dots showed their potential for photostimulation device architectures, dominant photoelectrochemical charge transfer combined with heavy-metal content in such architectures hinders their safe use. In this study, we demonstrate heavy-metal-free quantum dot-based nano-heterojunction devices that generate capacitive photoresponse. For that, we formed a novel form of nano-heterojunctions using type-II InP/ZnO/ZnS core/shell/shell quantum dot as the donor and a fullerene derivative of PCBM as the electron acceptor. The reduced electron-hole wavefunction overlap of 0.52 due to type-II band alignment of the quantum dot and the passivation of the trap states indicated by the high photoluminescence quantum yield of 70% led to the domination of photoinduced capacitive charge transfer at an optimum donor-acceptor ratio. This study paves the way toward safe and efficient nanoengineered quantum dot-based next-generation photostimulation devices.
Citation - WoS: 56
Citation - Scopus: 56
Cadmium-Free and Efficient Type-II InP/ZnO Quantum Dots and Their Application for Leds
(Amer Chemical Soc, 2021) Eren, Guncem Ozgun; Sadeghi, Sadra; Jalali, Houman Bahmani; Ritter, Maximilian; Han, Mertcan; Baylam, Isinsu; Nizamoglu, Sedat
It is a generally accepted perspective that type-II nanocrystal quantum dots (QDs) have low quantum yield due to the separation of the electron and hole wavefunctions. Recently, high quantum yield levels were reported for cadmium-based typeII QDs. Hence, the quest for finding non-toxic and efficient type-II QDs is continuing. Herein, we demonstrate environmentally benign type-II InP/ZnO/ZnS core/shell/shell QDs that reach a high quantum yield of similar to 91%. For this, ZnO layer was grown on core InP QDs by thermal decomposition, which was followed by a ZnS layer via successive ionic layer adsorption. The small-angle Xray scattering shows that spherical InP core and InP/ZnO core/ shell QDs turn into elliptical particles with the growth of the ZnS shell. To conserve the quantum efficiency of QDs in device architectures, InP/ZnO/ZnS QDs were integrated in the liquid state on blue light-emitting diodes (LEDs) as down-converters that led to an external quantum efficiency of 9.4% and a power conversion efficiency of 6.8%, respectively, which is the most efficient QD-LED using type-II QDs. This study pointed out that cadmium-free type-II QDs can reach high efficiency levels, which can stimulate novel forms of devices and nanomaterials for bioimaging, display, and lighting.