# Mimicking Synaptic Plasticity: Optoionic MoS2 Memory Powered by Biopolymer Hydrogels as a Dynamic Cations Reservoir

Yeonsu Jeong, Pietro Tordi, Adrián Tamayo, Bin Han, Massimo Bonini, Paolo Samorì

► To cite this version:

Yeonsu Jeong, Pietro Tordi, Adrián Tamayo, Bin Han, Massimo Bonini, et al. Mimicking Synaptic Plasticity: Optoionic MoS2 Memory Powered by Biopolymer Hydrogels as a Dynamic Cations Reservoir. Advanced Functional Materials, 2025, 10.1002/adfm.202509607. hal-05222228

HAL Id: hal-0522228

https://univoak.hal.science/hal-0522228v1

Submitted on 25 Aug 2025

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
<figure><img src="image_2.png" /></figure>

# Mimicking Synaptic Plasticity: Optoionic MoS₂ Memory Powered by Biopolymer Hydrogels as a Dynamic Cations Reservoir

Yeonsu Jeong, Pietro Tordi, Adrián Tamayo, Bin Han, Massimo Bonini,* and Paolo Samori*

Neuromorphic devices are emerging as key components for next-generation computing, driven by the rapid growth of digital technology. To meet growing demand for energy-efficient logic operations, photonic synaptic devices have become a focal point of interest. Here, a novel molybdenum disulfide (MoS₂)-based synaptic memory field-effect transistor (FET) is presented, exploiting the photo-induced ionic gating effect through Janus functionalization with ion-conductive sodium alginate (SA) and ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF-TrFE)]. The integration of SA as a dynamic cations reservoir enables ion migration and corresponding modulation of persistent photoconductivity on MoS₂, emulating synaptic plasticity including sensory, short-term, and long-term memory operation. The SA/MoS₂ FET demonstrates over eight multilevel states adjustable by light irradiation conditions. The device also exhibits excellent visible-range photodetection (455–680 nm), with a high photoresponsivity of 20 kA W⁻¹ and a fast response time of 120 ms under 20 V gate bias and 680 nm LED illumination. Further functionality is endowed by decorating MoS₂ bottom face with P(VDF-TrFE), realizing 60 photo-induced multilevel states, and independent conductivity modulation via ferroelectric gating. This Janus SA/MoS₂/P(VDF-TrFE) configuration supports near-infrared detection governed by ferroelectric polarization. These findings highlight the transformative potential of integrating sustainable biopolymers with 2D materials for environmental-friendly neuromorphic 2D optoelectronics.

Y. Jeong[+], P. Tordi, A. Tamayo, B. Han, P. Samori

CNRS, ISIS UMR 7006

University of Strasbourg

8 Allée Gaspard Monge, Strasbourg 67000, France

E-mail: samori@unistra.fr

P. Tordi, M. Bonini

Department of Chemistry “Ugo Schiff” and CSGI

University of Florence

via della Lastruccia 3, Sesto Fiorentino 50019, Florence, Italy

E-mail: massimo.bonini@unifi.it

<figure><img src="image_3.png" /></figure>

The ORCID identification number(s) for the author(s) of this article
can be found under https://doi.org/10.1002/adfm.202509607

[+]*Present address: Department of Physics, Inha University, 100 Inha-ro, Michuhol-gu, Incheon 22212, South Korea

© 2025 The Author(s). Advanced Functional Materials published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

DOI: 10.1002/adfm.202509607

## 1. Introduction

As the global demand for data-intensive technologies like artificial intelligence, the Internet of Things, and Big Data continues to grow, conventional computing systems face an urgent bottleneck due to the energy-inefficient data shuttling between processing and memory units in traditional von Neumann architectures. This “von Neumann bottleneck” not only limits speed but also threatens the sustainability of modern computing. For decades, researchers have explored innovative memory devices to overcome the energy inefficiencies of traditional computing systems.[1,2] Among these, neuromorphic devices have gained significant interest because of their ability to blur the boundaries between processing and memory functions, mimicking the architecture and functions of the human brain.[3-5] An important category of neuromorphic devices focuses on synaptic memory, designed to emulate biological synapses—the neural connections responsible for learning and storing data in the human brain. By leveraging synaptic plasticity, these devices dynamically modulate synaptic weights, enabling efficient, adaptive, and parallel information processing.[6,7] In particular, using light as an input stimulus in optoelectronic synaptic devices offers additional advantages such as non-contact operation, high-speed signaling, and potential for wavelength-multiplexed processing. These unique features make optoelectronic synaptic devices a promising platform for building more scalable, energy-efficient, and multifunctional neuromorphic systems.[8-10] To realize these functionalities, a range of semiconductors have been proposed as active materials for optoelectronic synaptic transistors.[11-17] These cutting-edge devices promise to revolutionize computation-intensive fields including artificial neural networks, low-power electronics, and reconfigurable neuromorphic hardware, paving the way for next-generation intelligent systems.[18-20]

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have garnered significant attention for their strong electrostatic sensitivity and exceptional light-matter interactions, making them ideal building blocks for optoelectronic synaptic
devices.[21–26] Recent advancements include the development of optical memory devices leveraging persistent photoconductivity (PPC)[27–30] and hybrid structures utilizing charge trapping and de-trapping mechanisms at the interfaces.[31–36] For example, molybdenum disulfide (MoS₂)-based field-effect transistors (FETs) incorporating zero-dimensional (0D) quantum dots have demonstrated photonic multilevel memory characteristics.[37,38] However, these devices fail to capitalize on the intrinsic broad absorption spectrum of MoS₂, as their operational wavelength is limited by the narrower absorption characteristics of the 0D quantum dots. Moreover, many existing systems rely on toxic metals, such as cadmium- and lead-based quantum dots, underscoring the urgent need for sustainable, biocompatible, and environmentally friendly applications. As a second promising approach, electrolyte-gate transistors using the electrical double layer (EDL) enable ultralow energy consumption, making them attractive for neuromorphic systems.[39–42] However, these devices typically suffer from poor memory retention, as low operating voltages must be maintained to avoid undesirable electrochemical reactions or ion intercalation into TMD layers. Additionally, most electrolyte-gate transistors rely exclusively on electrical stimuli to form the EDL, with no demonstrated applicability toward synaptic devices responding simultaneously to multiple independent stimuli, such as ion concentration and light with the latter offering high spatio-temporal control over a broad range of incident wavelengths. In particular, the synaptic plasticity including both short- and long-term memory operation has yet to be realized solely by photons in 2D iontronics.

Addressing these limitations requires innovative approaches combining environmental sustainability with advanced functional performance. Nature-inspired materials such as biopolymers hold immense potential for this purpose, as they offer simultaneously flexibility, stretchability, and biocompatibility, which are essential for applications in intelligent robotics, wearable technology, smart chips, and health monitoring. Among these materials, alginate—a biocompatible and biodegradable anionic polysaccharide extracted from brown algae—stands out for its exceptional film-forming capabilities, ionic affinity, and environmental sustainability.[43,44] The —OH and —COO— functional groups in alginate's mannuronate and guluronate units enable coordination with various metal cations,[45] broadening its application across multiple fields, including sensors and energy storage.[46]

Building on these considerations, we report an unprecedented MoS₂-based optoionic synaptic memory FET through asymmetric, supramolecular Janus functionalization of its surfaces with ion-conductive sodium alginate (SA) and ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF-TrFE)]. By optimizing the concentration of SA, we uncover a novel photoinduced ionic gating effect on 2D semiconductors, where the photogating effect on MoS₂ induces ion migration in the dynamic cations reservoir provided by the SA layer, tuning the PPC behavior. This ion-mediated PPC enables the emulation of synaptic plasticity (including sensing, short-term potentiation, and long-term potentiation) in response to a 680 nm LED frequency, a capability that surpasses most 2D artificial synapses, which rely predominantly on charge trapping at hybrid interfaces (Table S1, Supporting Information). Intriguingly, the SA/MoS₂ memory FET exhibits over eight tunable multilevel states, ad-

justable through the intensity and exposure time of the incident light. While the device exhibits synaptic functionality without the need for gate bias, applying a gate voltage further enables its use as a high-performance photodetector, demonstrating a photoresponsivity of 20 kA W⁻¹ and a response time of 120 ms under 680 nm LED illumination at VGS = 20 V, which is comparable to the literature.[47–49] The incorporation of P(VDF-TrFE) as a ferroelectric bottom gate further expands functionality, thereby achieving 60 linear multilevel states with enhanced linearity. This Janus SA/MoS₂/P(VDF-TrFE) architecture also enables near-infrared (NIR) photon detection, modulated by ferroelectric polarization. These findings establish a new pathway for functional polymers, especially ion-conductive biopolymers, integrated with supramolecular Janus 2D materials, paving the way for a novel class of artificial optical synapses and energy-efficient computing systems.

## 2. Result

Figure 1a,b illustrate the three-dimensional (3D) schematic views of a MoS₂ channel FET coated with a 500 nm-thick SA top layer, highlighting the photo-induced ionic gating effect. Upon photon irradiation at λ = 680 nm, photo-excited electrons are generated in the MoS₂ channel due to a photogating effect.[50,51] The latter determines an increase in the Fermi energy of MoS₂, which drives the migration of cations within the SA layer toward the MoS₂ surface. The proposed mechanism behind this effect, which relies on the role of the SA as cations reservoir, is discussed further in the following section. A 2D hexagonal boron nitride (h-BN) layer was adopted to ensure a defect-less dielectric surface compared to hydrophilic silicon dioxide (SiO₂), thereby reducing the trap densities at the channel/gate insulator interface. Atomically-thin MoS₂ crystals are particularly vulnerable to interfacial traps, and the hydrophilic nature of SiO₂ can significantly complicate the photoresponse of MoS₂-based devices.[50,51] A detailed comparison on the photoresponse between MoS₂ FETs with and without h-BN is portrayed in Figure S1 (Supporting Information). The h-BN layer's advantages are evident under 680 nm illumination at 0.03 mW cm⁻², where the photocurrent (I<sub>PHOTO</sub>) of the MoS₂/h-BN FET was 20 times higher, and its overall photoswitching speed was 3 times faster than that of the control MoS₂ FET supported on SiO₂. Atomic Force Microscopy (AFM) height profiles of Figure S2 (Supporting Information) confirmed that MoS₂ and h-BN crystals were ≈6 nm- and 25.5 nm-thick, respectively. For a reliable photodetecting performance of MoS₂ FET (Figure S1c, Supporting Information and gray dots of Figure 1e), h-BN flakes were placed underneath the MoS₂ crystal for all the SiO₂ bottom gate devices. Next, the top surface of MoS₂ supported on h-BN was decorated with SA. The latter not only provides functionality but also acts as a protective layer for the underlying device components, as suggested by its high thermal stability (220 °C, see the thermogravimetric analysis results in Figure S3a, Supporting Information). By making use of the photo-induced ionic gating effect of our SA/MoS₂ FET, it has been possible to mimic a biological synapse, where parallel processing is achieved by analog-like modulation in synaptic efficacy. When action potentials (analogous to photon stimuli in our artificial synapse) trigger neurotransmitter release into the synaptic cleft, the connection between the presynaptic and
<figure><img src="image_4.png" /><figcaption>**Figure 1.** Optoionic synaptic plasticity of SA/MoS₂ FET. a) 3D schematic view of a MoS₂ synaptic memory FET with a 500 nm thick-SA layer. b) Cartoon of the photo-induced ionic gating effect at magnified van der Waals heterojunction between SA and MoS₂ under 680 nm LED illumination. c) Schematic illustration of a biological synapse in the human neural system. d) Memory model of the artificial synaptic device as a function of stimulus frequency, illustrating sensory memory (SM) in black, short-term memory (STM) in green, and long-term memory (LTM) in red. These correspond to the transient response, short-term plasticity (STP), and long-term plasticity (LTP) of biological synapses, respectively. e) Time-resolved photoresponse of the SA/MoS₂ synaptic memory and control sample under 680 nm LED illumination at VGS = 0 V and VDS = 1 V. f) Time-resolved photoresponse of SA/MoS₂ synaptic memory under 680 nm LED illumination at frequencies of 0.1, 0.25, and 0.5 Hz with VGS = 0 V and VDS = 1 V, demonstrating SM (black), STM (green), and LTM (red) operations, respectively.</figcaption></figure>

postsynaptic neurons is modified (Figure 1c). This modification can either strengthen or weaken the connection, corresponding to potentiation and depression, respectively. Potentiation, which is associated with learning/memory, is a key characteristic of biological synapses. Figure 1d displays a memory model characterized by different frequencies of stimulus, emulating various memory behaviors, including sensory memory (SM), short-term memory (STM), and long-term memory (LTM), as represented with black, green, and red curves. Interestingly, the SA/MoS₂ FET exhibited photonic multilevel memory characteristics (red dots in Figure 1e) when kept under continuous 680 nm LED illumination (0.03 mW cm⁻²). Remarkably, more than eight distinct mem-

ory states were achieved solely through optical stimulation, without the need for any electrical input signals. It is also noteworthy that the first $I_{\text{PHOTO}}$ of both SA/MoS₂ and pristine MoS₂ FET approached ≈200 nA, indicating that 500 nm-thick SA does not hinder the propagation of 680 nm light. In order to confirm the transparency of SA in the visible range, ultraviolet-visible (UV-vis) spectroscopy of SA was conducted and reported in Figure S4 (Supporting Information). More interestingly, all three SM, STM, and LTM can be generated by modulating the light stimulus frequency to 0.1, 0.25, and 0.5 Hz, respectively, with consistent light intensity (0.01 mW cm⁻²) and exposure time. The three operating modes of the SA/MoS₂ FET denote a unique photonic synaptic
<figure><img src="image_5.png" /><figcaption>**Figure 2.** The working mechanism of PPC in SA/MoS₂ FET. 2D schematics of the SA/MoS₂ FET and corresponding energy band diagrams of Au-MoS₂-Au under different conditions: a) equilibrium in the dark, b) photogating effect under 680 nm LED illumination, and c) photo-induced ionic gating effect after LED off, leading to PPC in the SA/MoS₂ FET via electron-cation attraction. d) Transfer curves of the SA/MoS₂ FET, showing PPC after 680 nm LED illumination at V<sub>DS</sub> = 0.1 V. e) Time-resolved photoresponse of the SA/MoS₂ FET under 680 nm LED illumination, and f) its *I*<sub>PHOTO</sub> decay over time, with a decay time constant of 0.3 s. Experimental data (black dots) were fitted using an exponential decay function to determine the decay time constants.</figcaption></figure>

plasticity that effectively emulates the transient response, STP, and LTP of biological synapses.

Intriguing synaptic STM and LTM operations of the SA/MoS₂ FET can be elucidated with the movement of cations in the SA layer under and after light illumination. **Figure 2a–c** illustrates the 2D schematics of the van der Waals interface between MoS₂ and SA, along with the corresponding band diagrams. Electron-dominant band diagrams are established as a consequence of intrinsic sulfur vacancies of MoS₂ and the Fermi-level pinning between MoS₂ and thermally evaporated Au, as displayed in Figure 2a.[52,53] Upon exposure to 680 nm LED, a photogating effect occurs, as reported previously, which causes electron doping in MoS₂ (Figure 2b).[50,54–56] Driven by the photo-excited electron accumulation in MoS₂, electrostatic force can result in the migration of cations in SA toward the interface of SA/MoS₂. To make sure that no intercalation of sodium ions into MoS₂ layers occurs when 0.25 wt.% of SA was used, Raman spectroscopy and XPS measurements were conducted (Figures S5 and S6, Supporting Information). Even after turning off the LED, MoS₂ retains accumulated electrons due to the ion-electron attraction, leading to PPC in the SA/MoS₂ FET. The anionic character of alginate is essential in this process, as it retrieves sodium ions progressively and redistributes them within its network once the light is turned off. This dynamic ionic redistribution, whose kinetics can be finely tuned by modulating the SA loading on the top

of the channel, ensures the reversibility of the PPC effect, contributing to the stability and repeatability of the device’s synaptic behavior. It is noteworthy that this photo-induced ionic gating effect is fundamentally different from previously reported PPC effects in MoS₂ caused by trapped charges upon strong UV light irradiation.[29,30] While MoS₂ can exhibit both photo-gate and PPC effects under visible and UV light due to intrinsic defects in the crystal, the presence of mobile ions in our system introduces an electrostatically driven mechanism distinct from conventional defect-induced PPC. This ionic contribution enables a strong yet reversible PPC effect. The transfer curves of Figure 2d reveal that the SA/MoS₂ FET exhibits a strong PPC effect under 680 nm of visible photon stimulus. Compared to a dark condition (black square in Figure 2d), the transfer curve (red square) under 680 LED illumination showed 4 V of the threshold voltage shift toward the negative side, which indicated electron doping in MoS₂ by photogating effect. After turning off the LED, the transfer curve maintained electron accumulations, demonstrating the strong PPC effect governed by ion-electron attractions (blue square). Conversely, transfer characteristics of pristine MoS₂ FET without SA in the same device architecture showed a typical photoresponse, with the absence of the PPC effect as evidenced in supporting Figure S7b (Supporting Information). The pronounced PPC effect of SA/MoS₂ FET can be directly observed not only in the static transfer curves (Figure 2d)
but also in the time-resolved photoresponse after irradiation with 0.5 mW cm⁻² of 680 nm LED (Figure 2e). After a fast decay of I<sub>PHOTO</sub> with a time constant of 0.3 s, due to electron-hole recombination in MoS₂ (Figure 2f), PPC induced by ionic gating was retained for over 100 s. Moreover, the decay time constant (≈4 s) of a pristine MoS₂ FET without SA shown in Figure S7c,d (Supporting Information) is ≈10 times slower than the one observed in the SA/MoS₂ FET. This difference represents the unambiguous demonstration that the PPC effect in our SA/MoS₂ hybrid system is ruled by a photo-induced ionic gating effect, realizing STM and LTM. Such a prolonged retention time exceeding 100 s clearly falls within the time scale typically associated with LTM in artificial synaptic devices,<sup>[57]</sup> and is also comparable to the retention characteristics reported in previous organic/2D TMD-based synaptic hybrid devices.<sup>[24,58]</sup> Figure S8 (Supporting Information) displays the transfer curves and time-resolved photoresponse of the SA/MoS₂ FET under vacuum (1.3 mbar). In such an environment, where cations in SA are immobile due to the absence of freely diffusing water within the polymer matrix, the SA/MoS₂ FET exhibited no PPC effect. The matrix contains 17.7% (wt/wt) at RH = 40% (see Figure S3b, Supporting Information), which strongly interacts with both ions and alginate's functional groups, as evidenced by the absence of peaks in the Differential Scanning Calorimetry (DSC) thermogram in Figure S3c (Supporting Information). The I<sub>OFF</sub> of the transfer curves in Figure S8a (Supporting Information) lowers from nA in ambient condition to pA under vacuum—confirming that cations are immobilized—providing further evidence that the PPC effect driven by ion-electron interaction can occur in ambient conditions. Figure S9 (Supporting Information) highlights the importance of SA concentration in ensuring a reliable photo-induced ionic gating effect. A high concentration of SA (2.5 wt.%)—and therefore of Na⁺—caused uncontrollable electrostatic doping in the MoS₂ channel, preventing the observation of the photo-induced ionic gating effect. On the other hand, a low concentration of SA (0.025 wt.%) failed to provide sufficient cations, as revealed by I<sub>D,OFF</sub> of 1 pA, similar to pristine MoS₂ FET.

Next, the multilevel memory characteristics of the SA/MoS₂ device were assessed by varying the measurement conditions, such as light intensity, exposure time, LED wavelengths, and VGS. Figure 3a shows the gradual increase in I<sub>PHOTO</sub> upon growing the light intensity. The I<sub>MAX,PHOTO</sub> reached up to 820 nA upon exposure to 0.50 mW cm<sup>-2</sup> of 680 nm LED. Interestingly, not only I<sub>MAX,PHOTO</sub> but also the persistent photocurrent (I<sub>PPC</sub>) increased up to 350 nA. This indicates that, as the light intensity increases, the degree of photogating also increases, leading to a higher I<sub>PPC</sub>. It was also found that the transition from SM to LTM can be achieved by adjusting the light intensity. Upon applying a light stimulus exceeding 0.03 mW cm<sup>-2</sup> both STM and LTM are observed, whereas only a transient conductivity change can be induced upon illumination at 0.01 mW cm<sup>-2</sup>, serving as SM in an artificial synapse. (Figure 3a) By taking advantage of robust LTM operation under a high light intensity of 0.50 mW cm<sup>-2</sup>, a stepwise increase in I<sub>PPC</sub> depending on the exposure time can be also generated, as shown in Figure 3b. From now on, unless specified otherwise, the light intensity was fixed at 0.50 mW cm<sup>-2</sup> for all the measurements. The device exposed for a total of 20 s (5 s × 4 times) showed an I<sub>PPC</sub> of 620 nA, and for 9 s (1.5 s × 6 times), the I<sub>PPC</sub> converged to 410 nA, as presented in Figure 3b. This means

that I<sub>PPC</sub> exhibits a positive correlation not only with light intensity but also with exposure time, as shown in Figure 3c. Even if SA/MoS₂ could dynamically create STP and LTP, the number of non-volatile memory levels in LTP is limited due to the abrupt I<sub>PPC</sub> change mediated by the superior photogating effect of MoS₂, exhibiting a non-linear curve (black square in Figure 3c). Interestingly, the nonlinear relationship between I<sub>PPC</sub> and exposure time under VGS = 0 V can be mitigated with the help of VGS. In the case of VGS = -20 V (represented by triangles in Figure 3c), the absolute magnitude of I<sub>PPC</sub> decreased; however, the linearity, which is one of the crucial parameters for synaptic devices, improved to an ideal level. Suppressing the photogating effect of MoS₂ with negative VGS<sup>[50]</sup> enables delicate control of the number of cations migrating on MoS₂ surface. On the other hand, at VGS = 20 V, there is no photo-induced ionic gating effect, and only the typical photodetection with fast-photoswitching speed (rise/fall time of 120/120 ms) is observed, as revealed in Figure S10 (Supporting Information). This phenomenon can be ascribed to the accumulation of cations at the SA/MoS₂ interface driven by electrostatic gating on MoS₂, which induces a saturated current state. In other words, applying VGS improves multilevel characteristics (VGS < 0) as well as it endows multifunctionality on SA/MoS₂ FET, serving also as a photodetector (VGS > 0). At VGS = 20 V, photoresponsivity (R) of SA/MoS₂ FET becomes 20, 37, and 100 kA W<sup>-1</sup> upon 680, 530, and 455 nm LED irradiation, respectively. The detailed estimation of R is provided in Figure S11 (Supporting Information). Figure 3d reveals that our SA/MoS₂ FET exhibits photonic multilevel behavior also when exposed to different visible wavelengths. (Figure 3a–c were obtained from two different devices. Device 1 was used for Figure 3a–c, and Device 2 was used for Figure 3d,e. The difference in I<sub>MAX,PHOTO</sub> values under identical light exposure conditions can originate from the variation in channel areas. Supporting Figure S12 (Supporting Information) provides optical microscopy images and responsivity estimation for each device. Such a broad absorption characteristic is guaranteed by the capacity of our device to fully exploit the inherent optoelectronic properties of MoS₂, in stark contrast to previous photonic memory studies that were limited to specific wavelengths of incident light.<sup>[29,30,37,38]</sup> More interestingly, a system reset, analogous to an auto-refresh of cache data, can be achieved by turning off the V<sub>DS</sub>, which interrupts electron injection from the source and allows the previously accumulated Na⁺ ions at the SA/MoS₂ interface to diffuse back into the alginate matrix. This ion redistribution effectively restores the device to its initial state without the need for external voltage pulses. Compared to other previous reports where high voltages were required to remove trapped charges,<sup>[29,30,37,38,40–42]</sup> the photo-induced ionic gating effect provides extraordinarily energy-efficient device operation through the van der Waals ion-electron interactions. Measurements in Figure 3e provide unambiguous evidence that the reset can be achieved without the need to use high voltages, also confirming the applicability of the SA layer as a dynamic cations reservoir operating under successive light pulses. To confirm the repeatability of the switching behavior enabled by this distinctive reset process, an endurance test was performed and included in Figure S13 (Supporting Information).

As discussed in Figure 3c, linearity in LTM behavior can be achieved upon applying a controlled voltage to the bottom gate compared to adjusting the exposure time. However, applying a
<figure><img src="image_6.png" /><figcaption>**Figure 3.** Optoelectrical characteristics of SA/MoS₂ photonic-multilevel memory. a) Time-resolved photoresponse of the SA/MoS₂ FET under 680 nm LED illumination with varying light intensities from 0.01 to 0.50 mW cm⁻² at VGS = 0 V and VDS = 1 V. b) Time-resolved photoresponse of the SA/MoS₂ FET under 680 nm LED, comparing maximum IPPC values for exposure times of 20 s (top) and 9 s (bottom) at VGS = 0 V and VDS = 1 V. c) IPPC of SA/MoS₂ FET as a function of exposure time at different VGS. d) Time-resolved photoresponse upon exposure to visible LED illumination at three different wavelengths. e) Photoresponse upon device exposure at successive light pulses at VGS = 0 V and VDS = 1 V, demonstrating that the device returns to its idle (reset) state once the voltage sources are disconnected. Voltage disconnection, represented by gray segments between measurements, resets the device.</figcaption></figure>

constant voltage for all device operations will result in high power
consumption, making it undesirable for energy-efficient comput-
ing systems. In order to impart a permanent ferroelectric gating
effect on 2D MoS₂, the bottom surface of MoS₂ was decorated
with 200 nm-thick P(VDF-TrFE) layer, as shown in **Figure 4a**.
Due to the large surface roughness of crystalline P(VDF-TrFE), all
reported MoS₂ ferroelectric FETs (FeFETs) have utilized P(VDF-

TrFE) as a top gate.[59,60] However, by transferring the flake onto
the spin-coated P(VDF-TrFE) with a relatively flat surface com-
pared to that after curing for crystallization,[61,62] we successfully
transferred a 6 nm thin MoS₂ flake and fabricated an MoS₂-
based bottom gate FeFET with a 10 µm channel length. The de-
tails on FeFET device fabrication and optical and AFM examina-
tion of MoS₂ supported on crystalline P(VDF-TrFE) are given in
<figure><img src="image_7.png" /><figcaption>**Figure 4.** Non-volatile MoS₂ memory FET using ferroelectric P(VDF-TrFE). a) Side-view scheme of the MoS₂/P(VDF-TrFE) heterojunction before and after curing. b) Topographical AFM image of MoS₂/P(VDF-TrFE), showing significant changes in the root-mean-square roughness (R<sub>RMS</sub>) before and after curing. The scale bar represents 2 µm. c) Raman spectra of MoS₂ crystals supported on different insulators: black (before curing of P(VDF-TrFE)) and red (after curing of P(VDF-TrFE)) and green (h-BN). d) Side-view scheme of a MoS₂ FeFET to describe ferroelectric dipole alignment in P(VDF-TrFE) under Program state after V<sub>GS</sub> = -20 V, 1 s pulse and Erase state after V<sub>GS</sub> = +20 V, 1 s pulse. e) Transfer curves of the MoS₂ FeFET at V<sub>DS</sub> = 1 V, showing a maximum ferroelectric hysteresis of 10 V depending on the gate voltage sweep. Program and Erase states are measured at V<sub>GS</sub> = 0 V and V<sub>DS</sub> = 1 V after applying -20 V and 20 V pulses. f) Memory retention properties of the non-volatile MoS₂ FeFET for 2000 s.</figcaption></figure>

Figure S14 (Supporting Information). To confirm the crystalline β-phase responsible for the ferroelectricity of P(VDF-TrFE), X-ray diffraction analysis was conducted and included in Figure S15 (Supporting Information). Figure 4b shows the topographical AFM images of MoS₂ on the P(VDF-TrFE) before and after curing (for crystallization), revealing that the curing process is accompanied by a notable increase in the root-mean-square roughness (R<sub>RMS</sub>) from 2.1 to 12.5 nm as estimated on a MoS₂ region of 2 × 2 µm². The strain caused by crystallization hardly changed the in-plane vibrational mode of MoS₂, as shown in Figure 4c, where the MoS₂ Raman spectra remain the same regardless of the state of the bottom insulator. Considering the thickness of the 200 nm P(VDF-TrFE) layer and its coercive electric field of 80 MV m⁻¹, we applied a -20 V, 1 s pulse to the bottom Au electrode for the Program state and a +20 V, 1 s pulse for the Erase state to fully align the dipoles, as shown in Figure 4d. Figure 4e shows the transfer characteristics of our non-volatile MoS₂ FeFET, achieved under different V<sub>GS</sub> sweep ranges from 10 to 20 V to access intermediate polarization states. The memory hysteresis window increases from 5 V (-10 to 10 V sweep) to 10 V (-20 to 20 V sweep), and the Program/Erase states are clearly distinguished at V<sub>GS</sub> = 0 V after the Program and Erase pulses, as indicated by triangular-shaped points. The retention properties of the Program/Erase states are maintained for at least 2000 s,

with a ratio of 1000 throughout the entire duration, as shown in Figure 4f.

As a final device application, we integrated SA into the MoS₂ FeFET to develop a Janus MoS₂ FET toward an energy-efficient photonic artificial synapse device, as illustrated in Figure 5a. The conductivity of the Janus MoS₂ FET can be independently modulated through two different remote controls, by either applying electrical or photonic pulses. The electrical control is achieved via pulse-induced ferroelectric modulation on the bottom P(VDF-TrFE) layer, while the photonic control is achieved through photo-induced ionic gating on the top SA layer. The transfer curves of the Janus MoS₂ FET in Figure 5b reveal that the memory hysteresis window of 10 V is retained even after the SA deposition. In fact, the Program/Erase current ratio (over 1000), measured after applying a 1 s pulse of V<sub>GS</sub> = ±20 V, remains similar to that before SA deposition. Beyond the static memory hysteresis, the device exhibits robust retention properties for over 10 000 s. This stability denotes that the ferroelectric gating predominantly modulates the MoS₂ conductivity without contributing to cation migration within the SA layer. Finally, our Janus SA/MoS₂/P(VDF-TrFE) device has been adapted to emulate a photonic synaptic device through a combination of ferroelectric and photo-induced ionic gating. As demonstrated in Figure 3, it operates in both SM and LTM modes, suggesting that multifunctionality can be also
<figure><img src="image_8.png" /><figcaption>**Figure 5.** Asymmetric supramolecular functionalization of 2D MoS₂ FET with SA and ferroelectric polymer. a) Side-view scheme of the Janus MoS₂ FET achieved by interfacing SA with the MoS₂ FeFET. b) Transfer curves of the MoS₂ FeFET (black) and Janus MoS₂ FET (red) at VGS = 1 V, showing a maximum ferroelectric hysteresis of 10 V, regardless of the presence of SA. c) Memory retention properties of the Janus MoS₂ FET over 12 000 s. Time-resolved photoresponse of the Janus MoS₂ at VGS = 0 V and VDS = 1 V, demonstrating d) sensory memory (SM) under 680 nm LED illumination at the ferroelectric Erase state, e) synaptic LTM under 680 nm LED illumination at the ferroelectric Program state, and f) SM by leveraging the ferroelectric Erase state under NIR LED illumination.</figcaption></figure>

achieved through non-volatile ferroelectric gating rather than applying high gate voltage, thus securing energy-efficient operation. For a quantified comparison, we estimated the power consumption of both the h-BN and P(VDF-TrFE) supported MoS₂ synaptic FETs (Figure S16, Supporting Information). We found that SA/MoS₂/h-BN FET exhibits an average gate power consumption (P<sub>G</sub>) of 0.2 nW at VGS = -20 V for 80 s, while the SA/MoS₂/P(VDF-TrFE) FET features P<sub>G</sub> = 0 nW at VGS = 0 V. Although the sub-nW P<sub>G</sub> of the SA/MoS₂/h-BN FET appears insignificant compared to the tens of nW of drain power consumption (P<sub>D</sub>), the complete elimination of P<sub>G</sub> is a critical factor, reducing the burden of heat dissipation and facilitating continued device downscaling. For SM operation, shown in Figure 5d, the MoS₂ is in a high-conductive Erase state, whereas the Janus MoS₂ FET in its low-conductive Program state can display up to 60 linear multilevel states (Figure 5e). The resolution of each conductance state is ≈2 nA, with the total device conductance ranging from 0 to 120 nA. Further details and supporting data are provided in Figure S18 (Supporting Information). Additionally, in the Erase state, the photodetection wavelength range extends up to 940 nm, covering the NIR spectrum (Figure 5f). Although NIR photodetection of MoS₂ has already been reported under bottom gating,<sup>[63,64]</sup> the significance of our findings lies in applying nonvolatile memory characteristics to the photodetec-

tor via molecular functionalization, effectively reducing energy consumption.

**3. Conclusion**

In summary, we have successfully fabricated an optoionic artificial synapse that responds to a broad wavelength range within the visible spectrum (455–680 nm) through the photo-induced ionic gating effect between MoS₂ and ion-conductive sodium alginate (SA), an abundant and sustainable biopolymer acting as a dynamic cations reservoir. This novel mechanism enables emulating synaptic plasticity, including SM, STM, and LTM. By tuning light intensity and exposure time, the SA/MoS₂/h-BN multilevel memory device exhibited over eight distinct states using solely photon stimulation as a remote control. Importantly, unlike previous optoelectric multilevel memories based on trap/de-trap mechanisms, our device achieves a reset state through a simple voltage disconnection, eliminating the need for a high reset voltage. To further enhance the device functionality, we developed a novel Janus MoS₂ assembly by decorating also the bottom surface of MoS₂ with nonvolatile ferroelectric P(VDF-TrFE). This configuration enables independent modulation of conductivity via electronic pulses and photons, resulting in a multifunctional photonic memory device with 60 distinct states and ideal
linearity for energy-efficient LTM operations. By leveraging the non-volatile ferroelectricity, the device works without constant back-gating, offering a significant step forward in energy-efficient neuromorphic systems. Additionally, our Janus MoS₂ device demonstrated broad-spectrum photodetection capabilities, extending from visible to NIR wavelengths of 940 nm. These findings underscore the transformative potential of supramolecular functionalization of MoS₂ with ionic-conductive biopolymers, introducing a sustainable, versatile platform for high-performance, multifunctional 2D Janus synaptic devices. With their unique combination of photonic memory, synaptic behavior, and energy-efficient design, such devices pave the way for innovations in neuromorphic computing, optoelectronic systems, and beyond.

**4. Experimental Section**

**Materials:** Bulk 2H-MoS₂ and h-BN crystals were purchased from HQ Graphene. Sodium Alginate was purchased from CARLO ERBA [Product code: 366551: the Mannuronate/Guluronate (M/G) ratio was determined to be 1.17 using FT-IR spectroscopy (Figure S17 and Table S2, Supporting Information),[65,66] the molecular weight—calculated through viscosometric analysis—was ≈317 kDa (Table S3, Supporting Information),[65,67] the Na⁺ content (determined through ICP-AES analysis) was 6.1% of the weight of the dried SA powder. P(VDF-TrFE) and 2-butanone were purchased from Sigma-Aldrich (Product codes: 900904 and 360473).

**Device Fabrication—MoS₂/h-BN FET:** SiO₂ (270 nm)/n⁺-Si substrates (Fraunhofer Institute IPMS) were cleaned sequentially with acetone and ethanol in an ultrasonicator for 30 min each. Few-layer h-BN flakes were mechanically exfoliated using polydimethylsiloxane (PDMS, SYLGARD 184 Kit). Subsequently, another PDMS stamp was used to exfoliate few-layer h-BN crystals from the original PDMS surface. The exfoliated h-BN was inspected under an optical microscope to select flakes with optimal lateral size and uniformity. Thereafter, they were transferred onto the SiO₂/n⁺-Si substrates. The semiconducting MoS₂ flakes were exfoliated through the same mechanical exfoliation process. The alignment of the MoS₂ flake on the PDMS stamp with the h-BN/SiO₂/n⁺-Si substrate was accomplished using the optical microscope and a CCD camera-equipped microaligner. The MoS₂ flake was then transferred onto the h-BN surface by applying vertical pressure. (The thickness of all h-BN and MoS₂ flakes used in this study ranged from 20 to 30 nm and 5 to 10 nm, respectively.) Source/Drain (S/D) electrodes of Au (50 nm) were patterned via photolithography (laser writer LW405B from Microtech, AZ1505 photoresist), thermal evaporation, and a lift-off process. The prepared samples were mildly annealed at 150 °C for 2 h in a nitrogen-filled glovebox to enhance contacts and minimize S-defect formation.

**Device Fabrication—MoS₂/P(VDF-TrFE) FeFET:** The Au/Cr (12 nm/3 nm) bottom gate electrodes were patterned on the SiO₂/n⁺-Si substrates using the previously described electrode fabrication method. P(VDF-TrFE) was dissolved in 2-butanone solvent to prepare a 3 wt.% solution. This solution was spin-coated onto the bottom gate electrodes, followed by thermal annealing on a hot plate at 100 °C for 1 min. The semiconducting MoS₂ channel was transferred onto the P(VDF-TrFE)/Au layers using the PDMS stamping method, followed by curing at 142 °C on a hot plate for 2 h in a nitrogen-filled glovebox to crystallize P(VDF-TrFE). Finally, S/D electrodes of Au (50 nm) were patterned using the same methods as for the bottom gate. The FeFET samples were annealed at 100 °C for 2 h in a nitrogen glovebox to improve contact quality.

**Device Fabrication—SA Deposition:** The 250 mg of SA was dissolved in 100 mL of Milli-Q water under gentle stirring for 1 h at room temperature. A 2 µL aliquot of the 0.25 wt.% SA solution was drop-casted onto the MoS₂ channel for both MoS₂/h-BN FET and MoS₂/P(VDF-TrFE) FeFET devices, respectively. Excess water was removed using an N₂ gun, leaving an SA hydrogel on the MoS₂ channel.

**Optoelectronic Measurements:** Electrical measurements were performed using a Keithley dual-channel 2636A and 4200A SCS semiconduc-

tor parameter analyzer under ambient atmosphere and dark conditions. Electrical transport characteristics in low vacuum (≈1.3 mbar) were measured using the 4200A SCS in a Lakeshore probe station. Photoresponse measurements of the transistors were conducted under the illumination of 740, 680, 530, and 455 nm LEDs.

**Material Characterization—Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES):** The amount of Na⁺ contained in the used sodium alginate was determined by means of an Agilent 720-ES Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES) equipped with a pneumatic nebulizer and a cyclonic spray chamber. Sodium alginate solutions 0.1% (w/v) in MilliQ were analyzed. The calibration lines were obtained by preparing the standard solutions starting from commercial standards certified at 1000 ppm. Sodium absorbance was evaluated at 589.592 nm. Measurements were performed in quadruplicate. After each measurement, the system was washed with a 2% HNO₃ solution.

**Material Characterization—Thermogravimetric Analysis (TGA):** TGA was carried out with a Discovery SDT650 from TA Instruments, using an alumina pan under air flux (100 mL min⁻¹). A heating ramp from room temperature (RT) to 950 °C, with a rate of 10 °C min⁻¹, was applied. For water content determination, samples were heated to 120 °C at the same rate, followed by a 10 min isotherm. Data were analyzed with Trios v5.1.1.46572 software (TA Instruments). Samples were all equilibrated at RH = 40% prior to measurement.

**Material Characterization—Differential Scanning Calorimetry (DSC):** DSC analysis was carried out by means of Discovery DSC 2500 (TA Instruments). In order to define the state of the water in the samples, the latter were subjected to a cooling ramp from 5 to -60 °C, followed by a heating ramp from -60 to 25 °C (in both cases with an heating rate of 1 °C min⁻¹). Tzero Aluminum Hermetic pans (TA Instruments) were used. Data were analyzed with Trios v5.1.1.46572 software (TA Instruments). Measurements were performed in duplicate. Samples were all equilibrated at RH = 40% prior the measurement.

**Material Characterization—X-Ray Photoelectron Spectroscopy (XPS):** XPS measurements (Thermo Scientific K-Alpha) were performed at a base chamber pressure of ~10⁻⁹ mbar using an Al Kα X-ray source (1486 eV). Spot sizes of 400 µm and pass energies of 200 eV (for wide scans) and 10–20 eV (for high-resolution scans) were used. All XPS spectra were calibrated to the C 1s peak at 284.8 eV.

**Material Characterization—Atomic Force Microscopy (AFM):** For AFM imaging, scan-assist mode atomic force microscopy was performed in the air using a Bruker Dimension Icon. The tip model was SCAN-ASSIST-AIR with a stiffness constant K = 0.4 N m⁻¹.

**Material Characterization—UV–Vis Spectrophotometry:** UV–Vis absorbance spectra of the gels were collected using a Cary UV–Vis multi-cell spectrometer (Agilent) in the 200–1000 nm range. Gels were adhered to the wall of a quartz cuvette, perpendicular to the light path.

**Material Characterization—Confocal Raman Microscopy:** Confocal Raman microscopy was carried out using a Renishaw InVia Qontor confocal microRaman system equipped with a front-illuminated CCD camera and a research-grade Leica DM 2700 microscope. Spectra were collected by using a 100× and a laser operating at 532 nm with a power of 100 mW and a grating of 2400 lines per mm. Spectra were processed with the Renishaw software WiRE 5.5, and corrected for cosmic rays, baseline, and noise.

**Material Characterization—X-Ray Diffraction Analysis:** The crystallinity of ferroelectric P(VDF-TrFE) polymer was investigated by X-ray diffraction patterns (Bruker D8 X-ray diffractometer).

**Supporting Information**

Supporting Information is available from the Wiley Online Library or from the author.

**Acknowledgements**

The authors acknowledge funding from the European Commission through the ERC project SUPRA2DMAT (GA-833707) and the
HORIZON-CL4-2023-DIGITAL-EMERGING-01-CNECT project 2D-PRINTABLE (GA-101135196) as well as the FLAG-ERA project MULTISPIN funded by the Agence Nationale de la Recherche (ANR-21-GRF1-0003-01), the Agence Nationale de la Recherche through the Interdisciplinary The-matic Institute SysChem via the IdEx Unistra (ANR-10-IDEX-0002) within the program Investissement d'Avenir, the Foundation Jean-Marie Lehn and the Institut Universitaire de France (IUF). The authors are also grate-ful to the financial supports from the CSGI (Consorzio Interuniversitario per lo Sviluppo dei Sistemi a Grande Interfase), the MUR-Italy ("Progetto Dipartimenti di Eccellenza 2023-2027" and "Progetto Dipartimenti di Eccellenza 2018-2022" (58503DIP_ECC) allocated to Department of Chemistry "Ugo Schiff"), the National Recovery and Resilience Plan (NRRP), Mission 4 Component 2 "Dalla ricerca all'impresa"-Call for tender No. 341 of 15/03/2022 of Italian Ministry of Research funded by the European Union - NextGenerationEU, CUP: B83C22004890007. Prof. Mirko Severi is gratefully acknowledged for the ICP-AES measure-ments. This work was also supported by a National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. RS-2023-00251360).

## Conflict of Interest

The authors declare no conflict of interest.

## Author Contributions

Y.J. and P.T. contributed equally to this work. Y.J., P.T., M.B., and P.S. con-ceived the experiments and designed the study. Y.J. and P.T. performed all optoelectrical and materials characterization. B.H. performed the XPS measurement. A.T. performed AFM measurement. Y.J., P.T., A.T., B.H., M.B., and P.S. discussed the results and contributed to the interpretation of data. Y.J., P.T., and P.S. co-wrote the paper with input from all co-authors.

## Data Availability Statement

The data that support the findings of this study are available from the cor-responding author upon reasonable request.

## Keywords

ionic gating, MoS₂ synaptic memory, P(VDF-TrFE), persistent photocon-ductivity, sodium alginate

Received: May 19, 2025

Revised: June 6, 2025

Published online:

[1] A. Sebastian, M. L. Gallo, R. Khaddam-Aljameh, E. Eleftheriou, *Nat. Nanotechnol.* **2020**, *15*, 529.

[2] C. Liu, H. Chen, S. Wang, Q. Liu, Y.-G. Jiang, D. W. Zhang, M. Liu, P. Zhou, *Nat. Nanotechnol.* **2020**, *15*, 545.

[3] A. Mehonic, A. J. Kenyon, *Nature* **2022**, *604*, 255.

[4] S. Choi, S. H. Tan, Z. Li, Y. Kim, C. Choi, P.-Y. Chen, H. Yeon, S. Yu, J. Kim, *Nat. Mater.* **2018**, *17*, 335.

[5] V. K. Sangwan, H.-S. Lee, H. Bergeron, I. Balla, M. E. Beck, K.-S. Chen, M. C. Hersam, *Nature* **2018**, *554*, 500.

[6] G. M. Shepherd, *The Synaptic Organization of the Brain*, Oxford University Press, Oxford **2004**.

[7] H. de Garis, C. Shuo, B. Goertzel, L. Ruiting, *Neurocomputing* **2010**, *74*, 3.

[8] K. Chen, H. Hu, I. Song, H. B. Gobeze, W.-J. Lee, A. Abtahi, K. S. Schanze, J. Mei, *Nat. Photonics* **2023**, *17*, 629.

[9] M. Lee, Y. Kim, S. H. Mo, S. Kim, K. Eom, H. Lee, *Small* **2024**, *20*, 2309851.

[10] S. Seo, J.-J. Lee, R.-G. Lee, T. H. Kim, S. Park, S. Jung, H.-K. Lee, M. Andreev, K.-B. Lee, K.-S. Jung, S. Oh, H.-J. Lee, K. S. Kim, G. Y. Yeom, Y.-H. Kim, J.-H. Park, *Adv. Mater.* **2021**, *33*, 2102980.

[11] B. Pradhan, S. Das, J. Li, F. Chowdhury, J. Cherusseri, D. Pandey, D. Dev, A. Krishnaprasad, E. Barrios, A. Towers, A. Gesquiere, L. Tetard, T. Roy, J. Thomas, *Sci. Adv.* **2020**, *6*, aay5225.

[12] Y. Wang, Z. Lv, J. Chen, Z. Wang, Y. Zhou, L. Zhou, X. Chen, S.-T. Han, *Adv. Mater.* **2018**, *30*, 1802883.

[13] Y. Chen, H. Wang, H. Chen, W. Zhang, M. Pätzel, B. Han, K. Wang, S. Xu, V. Montes-García, I. McCulloch, S. Hecht, P. Samori, *Adv. Mater.* **2024**, *36*, 2402515.

[14] S.-G. Kim, S.-H. Kim, J. Park, G.-S. Kim, J.-H. Park, K. C. Saraswat, J. Kim, H.-Y. Yu, *ACS Nano* **2019**, *13*, 10294.

[15] J. Yu, X. Yang, G. Gao, Y. Xiong, Y. Wang, J. Han, Y. Chen, H. Zhang, Q. Sun, Z. L. Wang, *Sci. Adv.* **2021**, *7*, abd9117.

[16] S. Gao, G. Liu, H. Yang, C. Hu, Q. Chen, G. Gong, W. Xue, X. Yi, J. Shang, R.-W. Li, *ACS Nano* **2019**, *13*, 2634.

[17] T. Li, J. Miao, X. Fu, B. Song, B. Cai, X. Ge, X. Zhou, P. Zhou, X. Wang, D. Jariwala, W. Hu, *Nat. Nanotechnol.* **2024**, *18*, 1303.

[18] S. Park, Y. Jeong, H.-J. Jin, J. Park, H. Jang, S. Lee, W. Huh, H. Cho, H. G. Shin, K. Kim, C.-H. Lee, S. Choi, S. Im, *ACS Nano* **2020**, *14*, 12064.

[19] W. Huh, D. Lee, S. Jang, J. H. Kang, T. H. Yoon, J.-P. So, Y. H. Kim, J. C. Kim, H.-G. Park, H. Y. Jeong, G. Wang, C.-H. Lee, *Adv. Mater.* **2023**, *35*, 2211525.

[20] M. Xu, X. Chen, Y. Guo, Y. Wang, D. Qiu, X. Du, Y. Cui, X. Wang, J. Xiong, *Adv. Mater.* **2023**, *35*, 2301063.

[21] X. Liu, K. Katti, D. Jariwala, *Matter* **2023**, *6*, 1348.

[22] B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti, A. Kis, *Nat. Nanotechnol.* **2011**, *6*, 147.

[23] V. K. Sangwan, D. Jariwala, I. S. Kim, K.-S. Chen, T. J. Marks, L. J. Lauhon, M. C. Hersam, *Nat. Nanotechnol.* **2015**, *10*, 403.

[24] Y. Wang, B. Han, M. Mayor, P. Samori, *Adv. Mater.* **2024**, *36*, 2307359.

[25] J. M. Pereira, D. Tezze, I. Niehues, Y. Asensio, H. Yang, L. Mester, S. Chen, F. Casanova, A. M. Bittner, M. Ormaza, F. Schiller, B. Martín-García, R. Hillenbrand, L. E. Hueso, M. Gobbi, *Adv. Funct. Mater.* **2022**, *32*, 2208761.

[26] D. Lin, J. Lynch, S. Wang, Z. Hu, R. K. Rai, H. Zhang, C. Chen, S. Kumari, E. A. Stach, A. V. Davydov, J. M. Redwing, D. Jariwala, *Nano Lett.* **2024**, *24*, 13935.

[27] M. M. Islam, D. Dev, A. Krishnaprasad, L. Tetard, T. Roy, *Sci. Rep.* **2020**, *10*, 21870.

[28] J. Lee, S. Pak, Y.-W. Lee, Y. Cho, J. Hong, P. Giraud, H. S. Shin, S. M. Morris, J. I. Sohn, S. Cha, J. M. Kim, *Nat. Commun.* **2017**, *8*, 14734.

[29] A. George, M. V. Fistul, M. Gruenewald, D. Kaiser, T. Lehnert, R. Mupparapu, C. Neumann, U. Hübner, M. Schaal, N. Masurkar, L. M. R. Arava, I. Staude, U. Kaiser, T. Fritz, A. Turchanin, *Npj 2D Mater. Appl.* **2021**, *5*, 15.

[30] Y.-C. Wu, C.-H. Liu, S.-Y. Chen, F.-Y. Shih, P.-H. Ho, C.-W. Chen, C.-T. Liang, W.-H. Wang, *Sci. Rep.* **2015**, *5*, 11472.

[31] S. Seo, S.-H. Jo, S. Kim, J. Shim, S. Oh, J.-H. Kim, K. Heo, J.-W. Choi, C. Choi, S. Oh, D. Kuzum, H.-S. P. Wong, J.-H. Park, *Nat. Commun.* **2018**, *9*, 5106.

[32] Y. Wang, J. Yang, W. Ye, D. She, J. Chen, Z. Lv, V. A. L. Roy, H. Li, K. Zhou, Q. Yang, Y. Zhou, S.-T. Han, *Adv. Electron. Mater.* **2020**, *6*, 1900765.

[33] M. M. Islam, A. Krishnaprasad, D. Dev, R. Martinez-Martinez, V. Okonkwo, B. Wu, S. S. Han, T.-S. Bae, H.-S. Chung, J. Touma, Y. Jung, T. Roy, *ACS Nano* **2022**, *16*, 10188.

[34] Y. Zhang, B. Wang, Z. Han, X. Shi, N. Zhang, T. Miao, D. Lin, Z. Jiang, M. Liu, H. Guo, J. Zhang, H. Hu, L. Wang, *ACS Photonics* **2023**, *10*, 1575.
[35] Y. Sun, M. Li, Y. Ding, H. Wang, H. Wang, Z. Chen, D. Xie, *InfoMat* **2022**, *4*, 12317.

[36] D. Xie, G. Gao, B. Tian, Z. Shu, H. Duan, W.-W. Zhao, J. He, J. Jiang, *Adv. Mater.* **2023**, *35*, 2212118.

[37] H.-S. Ra, T. W. Kim, D. A. Taylor, J.-J. Lee, S. Song, J. Ahn, J. Jang, T. Taniguchi, K. Watanabe, J. W. Shim, J.-S. Lee, D. K. Hwang, *Adv. Mater.* **2023**, *35*, 2303664.

[38] D. Xie, L. Wei, M. Xie, L. Jiang, J. Yang, J. He, J. Jiang, *Adv. Funct. Mater.* **2021**, *31*, 2010655.

[39] J. Yan, J. P. K. Armstrong, F. Scarpa, A. W. Perriman, *Adv. Mater.* **2024**, *36*, 2403937.

[40] J. Jiang, W. Hu, D. Xie, J. Yang, J. He, Y. Gao, Q. Wan, *Nanoscale* **2019**, *11*, 1360.

[41] B.-W. Yao, J. Li, X.-D. Chen, M.-X. Yu, Z.-C. Zhang, Y. Li, T.-B. Lu, J. Zhang, *Adv. Funct. Mater.* **2021**, *31*, 2100069.

[42] R. A. John, F. Liu, N. A. Chien, M. R. Kulkarni, C. Zhu, Q. Fu, A. Basu, Z. Liu, N. Mathews, *Adv. Mater.* **2018**, *30*, 1800220.

[43] K. Y. Lee, D. J. Mooney, *Prog. Polym. Sci.* **2012**, *37*, 106.

[44] K. Norajit, K. M. Kim, G. H. Ryu, *J. Food Eng.* **2010**, *98*, 377.

[45] P. Tordi, F. Ridi, P. Samorì, M. Bonini, *Adv. Funct. Mater.* **2025**, *35*, 2416390.

[46] P. Tordi, A. Tamayo, Y. Jeong, M. Bonini, P. Samorì, *Adv. Funct. Mater.* **2024**, *34*, 2410663.

[47] F. Huang, Q. Yang, Y. Sun, J. Chen, C. Liu, Y. Chao, J. Hu, G. Hu, W. Huang, *ACS Appl. Nano Mater.* **2025**, *8*, 5805.

[48] J.-Y. Wu, Y. T. Chun, S. Li, T. Zhang, J. Wang, P. K. Shrestha, D. Chu, *Adv. Mater.* **2018**, *30*, 1705880.

[49] J. Kwon, Y. K. Hong, G. Han, I. Omkaram, W. Choi, S. Kim, Y. Yoon, *Adv. Mater.* **2015**, *27*, 2224.

[50] O. Lopez-Sanchez, D. Lembke, M. Kayci, A. Radenovic, A. Kis, *Nat. Nanotechnol.* **2013**, *8*, 497.

[51] M. M. Furchi, D. K. Polyushkin, A. Pospischil, T. Mueller, *Nano Lett.* **2014**, *14*, 6165.

[52] C. Kim, I. Moon, D. Lee, M. S. Choi, F. Ahmed, S. Nam, Y. Cho, H.-J. Shin, S. Park, W. J. Yoo, *ACS Nano* **2017**, *11*, 1588.

[53] S. Bertolazzi, S. Bonacchi, G. Nan, A. Pershin, D. Beljonne, P. Samorì, *Adv. Mater.* **2017**, *29*, 1606760.

[54] H. Fang, W. Hu, *Adv. Sci.* **2017**, *4*, 1700323.

[55] M. Liu, J. Wei, L. Qi, J. An, X. Liu, Y. Li, Z. Shi, D. Li, K. S. Novoselov, C.-W. Qiu, S. Li, *Nat. Commun.* **2024**, *15*, 141.

[56] Y. Jeong, T. Kim, H. Cho, J. Ahn, S. Hong, D. K. Hwang, S. Im, *Adv. Mater.* **2023**, *35*, 2304599.

[57] Y. Choi, D. H. Ho, S. Kim, Y. J. Choi, D. G. Roe, I. C. Kwak, J. Min, H. Han, W. Gao, J. H. Cho, *Sci. Adv.* **2023**, *9*, adg5946.

[58] J. Zhu, Y. Yang, R. Jia, Z. Liang, W. Zhu, Z. U. Rehman, L. Bao, X. Zhang, Y. Cai, L. Song, R. Huang, *Adv. Mater.* **2018**, *30*, 1800195.

[59] H. S. Lee, S. W. Min, M. K. Park, Y. T. Lee, P. J. Jeon, J. H. Kim, S. Ryu, S. Im, *Small* **2012**, *8*, 3111.

[60] X. Wang, P. Wang, J. Wang, W. Hu, X. Zhou, N. Guo, H. Huang, S. Sun, H. Shen, T. Lin, M. Tang, L. Liao, A. Jiang, J. Sun, X. Meng, X. Chen, W. Lu, J. Chu, *Adv. Mater.* **2015**, *27*, 6575.

[61] Y. Cho, H. Cho, S. Hong, D. Kang, Y. Yi, C. Park, J. H. Park, S. Im, *Nano Energy* **2021**, *81*, 105686.

[62] H. J. Lee, Y. Cho, J. Park, H. Cho, H. Han, C. Park, Y. Yi, T. K. An, J. H. Park, S. Im, *Mater. Sci. Eng. R Rep.* **2024**, *161*, 100859.

[63] P. Han, E. P. Adler, Y. Liu, L. S. Marie, A. E. Fatimy, S. Melis, E. V. Keuren, P. Barbara, *Nanotechnology* **2019**, *30*, 284004.

[64] W. Choi, M. Y. Cho, A. Konar, J. H. Lee, G.-B. Cha, S. C. Hong, S. Kim, J. Kim, D. Jena, J. Joo, S. Kim, *Adv. Mater.* **2012**, *24*, 5832.

[65] P. Tordi, R. Gelli, F. Ridi, M. Bonini, *Carbohydr. Polym.* **2024**, *326*, 121586.

[66] K. Sakugawa, A. Ikeda, A. Takemura, H. Ono, *J. Appl. Polym. Sci.* **2004**, *93*, 1372.

[67] M. A. Masuelli, C. O. Illanes, *Int. J. Biomater. Sci. Eng.* **2014**, *1*, 1.