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.
Optoelectronic biointerfaces have made a significant impact on modern science and technology from understanding the mechanisms of the neurotransmission to the recovery of the vision for blinds. They ...are based on the cell interfaces made of organic or inorganic materials such as silicon, graphene, oxides, quantum dots, and π-conjugated polymers, which are dry and stiff unlike a cell/tissue environment. On the other side, wet and soft hydrogels have recently been started to attract significant attention for bioelectronics because of its high-level tissue-matching biomechanics and biocompatibility. However, it is challenging to obtain optimal opto-bioelectronic devices by using hydrogels requiring device, heterojunction, and hydrogel engineering. Here, an optoelectronic biointerface integrated with a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate), PEDOT:PSS, hydrogel that simultaneously achieves efficient, flexible, stable, biocompatible, and safe photostimulation of cells is demonstrated. Besides their interfacial tissue-like biomechanics, ≈34 kPa, and high-level biocompatibility, hydrogel-integration facilitates increase in charge injection amounts sevenfolds with an improved responsivity of 156 mA W
, stability under mechanical bending , and functional lifetime over three years. Finally, these devices enable stimulation of individual hippocampal neurons and photocontrol of beating frequency of cardiac myocytes via safe charge-balanced capacitive currents. Therefore, hydrogel-enabled optoelectronic biointerfaces hold great promise for next-generation wireless neural and cardiac implants.
Luminescent solar concentrators (LSCs) are simple and cost-effective solar energy-harvesting devices. Indium phosphide (InP)-based colloidal quantum dots (QDs) are promising QDs for efficient LSC ...devices due to their environmentally benign nature. One major challenge in LSC devices is reabsorption losses. To minimize the reabsorption, Stokes shift engineering is a critical process to designing the QD material. Here, we present a protocol that contains the preparation of structurally engineered copper-doped InP/ZnSe QDs and their LSC application.
For complete details on the use and execution of this protocol, please refer to Sadeghi et al. (2020).
Display omitted
•Detailed methods for preparation of copper-doped InP/ZnSe core/shell structure•Integration of QDs into polydimethylsiloxane polymeric host material•Large-scale fabrication of LSC devices•Characterization techniques of QD-LSC devices
Luminescent solar concentrators (LSCs) are simple and cost-effective solar energy harvesting devices. Indium phosphide (InP)-based colloidal quantum dots (QDs) are promising QDs for efficient LSC devices due to their environmentally benign nature. One major challenge in LSC devices is reabsorption losses. To minimize the reabsorption, Stokes shift engineering is a critical process to designing the QD material. Here, we present a protocol that contains the preparation of structurally engineered copper-doped InP/ZnSe QDs and their LSC application.
Light-activated biointerfaces provide a non-genetic route for effective control of neural activity. InP quantum dots (QDs) have a high potential for such biomedical applications due to their uniquely ...tunable electronic properties, photostability, toxic-heavy-metal-free content, heterostructuring, and solution-processing ability. However, the effect of QD nanostructure and biointerface architecture on the photoelectrical cellular interfacing remained unexplored. Here, we unravel the control of the photoelectrical response of InP QD-based biointerfaces
nanoengineering from QD to device-level. At QD level, thin ZnS shell growth (∼0.65 nm) enhances the current level of biointerfaces over an order of magnitude with respect to only InP core QDs. At device-level, band alignment engineering allows for the bidirectional photoelectrochemical current generation, which enables light-induced temporally precise and rapidly reversible action potential generation and hyperpolarization on primary hippocampal neurons. Our findings show that nanoengineering QD-based biointerfaces hold great promise for next-generation neurostimulation devices.
Neural photostimulation has high potential to understand the working principles of complex neural networks and develop novel therapeutic methods for neurological disorders. A key issue in the ...light-induced cell stimulation is the efficient conversion of light to bioelectrical stimuli. In photosynthetic systems developed in millions of years by nature, the absorbed energy by the photoabsorbers is transported via nonradiative energy transfer to the reaction centers. Inspired by these systems, neural interfaces based on biocompatible quantum funnels are developed that direct the photogenerated charge carriers toward the bionanojunction for effective photostimulation. Funnels are constructed with indium-based rainbow quantum dots that are assembled in a graded energy profile. Implementation of a quantum funnel enhances the generated photoelectrochemical current 215% per unit absorbance in comparison with ungraded energy profile in a wireless and free-standing mode and facilitates optical neuromodulation of a single cell. This study indicates that the control of charge transport at nanoscale can lead to unconventional and effective neural interfaces.
Neuromorphic electronics, inspired by the functions of neurons, have the potential to enable biomimetic communication with cells. Such systems require operation in aqueous environments, generation of ...sufficient levels of ionic currents for neurostimulation, and plasticity. However, their implementation requires a combination of separate devices, such as sensors, organic synaptic transistors, and stimulation electrodes. Here, a compact neuromorphic synapse that combines photodetection, memory, and neurostimulation functionalities all‐in‐one is presented. The artificial photoreception is facilitated by a photovoltaic device based on cell‐interfacing InP/ZnS quantum dots, which induces photo‐faradaic charge‐transfer mediated plasticity. The device sends excitatory post‐synaptic currents exhibiting paired‐pulse facilitation and post‐tetanic potentiation to the hippocampal neurons via the biohybrid synapse. The electrophysiological recordings indicate modulation of the probability of action potential firing due to biomimetic temporal summation of excitatory post‐synaptic currents. These results pave the way for the development of novel bioinspired neuroprosthetics and soft robotics, and highlight the potential of quantum dots for achieving versatile neuromorphic functionality in aqueous environments.
In this work, a compact neuromorphic synapse that combines photodetection, memory, and neurostimulation functionalities all‐in‐one is presented. The photovoltaic device based on cell‐interfacing InP/ZnS quantum dots induces photo‐faradaic charge‐transfer mediated plasticity. The electrophysiological recordings indicate modulation of the probability of action potential firing due to biomimetic temporal summation of excitatory post‐synaptic currents.
Neuromorphic electronics, inspired by the functions of neurons, have the potential to enable biomimetic communication with cells. Such systems require operation in aqueous environments, generation of ...sufficient levels of ionic currents for neurostimulation, and plasticity. However, their implementation requires a combination of separate devices, such as sensors, organic synaptic transistors, and stimulation electrodes. Here, a compact neuromorphic synapse that combines photodetection, memory, and neurostimulation functionalities all‐in‐one is presented. The artificial photoreception is facilitated by a photovoltaic device based on cell‐interfacing InP/ZnS quantum dots, which induces photo‐faradaic charge‐transfer mediated plasticity. The device sends excitatory post‐synaptic currents exhibiting paired‐pulse facilitation and post‐tetanic potentiation to the hippocampal neurons via the biohybrid synapse. The electrophysiological recordings indicate modulation of the probability of action potential firing due to biomimetic temporal summation of excitatory post‐synaptic currents. The results pave the way for the development of novel bioinspired neuroprosthetics and soft robotics and highlight the potential of quantum dots for achieving versatile neuromorphic functionality in aqueous environments.
In this work, a compact neuromorphic synapse that combines photodetection, memory, and neurostimulation functionalities all‐in‐one is presented. The photovoltaic device based on cell‐interfacing InP/ZnS quantum dots induces photo‐faradaic charge‐transfer mediated plasticity. The electrophysiological recordings indicate modulation of the probability of action potential firing due to biomimetic temporal summation of excitatory post‐synaptic currents.
Photovoltaic biointerfaces offer wireless and battery-free bioelectronic medicine via photomodulation of neurons. Near-infrared (NIR) light enables communication with neurons inside the deep tissue ...and application of high photon flux within the ocular safety limit of light exposure. For that, nonsilicon biointerfaces are highly demanded for thin and flexible operation. Here, we devised a flexible quantum dot (QD)-based photovoltaic biointerface that stimulates cells within the spectral tissue transparency window by using NIR light (λ = 780 nm). Integration of an ultrathin QD layer of 25 nm into a multilayered photovoltaic architecture enables transduction of NIR light to safe capacitive ionic currents that leads to reproducible action potentials on primary hippocampal neurons with high success rates. The biointerfaces exhibit low in vitro toxicity and robust photoelectrical performance under different stability tests. Our findings show that colloidal quantum dots can be used in wireless bioelectronic medicine for brain, heart, and retina.
•Type-II InP/ZnO core/shell QDs functionalized with sulfide ligands are synthesized.•Type-II InP/ZnO QDs exihibit dual generation of superoxide and hydroxyl radicals.•QDs show antibacterial property ...against gram-negative bacteria.•Over 99.99% growth inhibition of P. aeruginosa under low-intensity green light.
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 (•OH) and superoxide (O2•−) radicals, while only O2•− 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.
PDF
