Liquid crystals（LCs）represent a class of self-assembling dynamic functional soft materials with significant anisotropy，primarily reflected in their shape，dielectric，and optical properties^［1-3］. These materials exhibit high degrees of order and mobility at the molecular，supramolecular，and macroscopic levels. LCs are highly sensitive to minor external perturbations such as electric and magnetic fields，a sensitivity that underpins their indispensable role in display applications^［4-5］. In recent years，the doping of LCs with nanoparticles has garnered considerable attention. The doping process is not only straightforward but also enhances the performance of nanoparticles and their host LCs in terms of spatial properties^［6-8］. Different nanoparticles doped into LCs may yield diverse effects. For instance，the incorporation of ferroelectric nanoparticles significantly enhances dielectric properties，optical anisotropy，and electro-optical response，while also improving the refractive light performance of LC composites^［9-11］. Doping with carbon nanotubes（CNTs）brings substantial benefits. LCs can control the alignment of CNTs，which in turn alter the characteristics of LCs，thus accelerating electro-optical responses，enhancing dielectric constants，and producing greater nonlinear optical and memory effects^［12-13］. Semiconductor nanoparticles，due to their semiconductor properties，have attracted interest. When doped into LCs，they provide pathways for electrons or holes to move between electrodes，showing broad research prospects in photovoltaic applications^［14-15］. Certain metal nanoparticles doped into LCs also yield unexpected effects. By leveraging the sensitivity of LCs to external stimuli，the plasmon resonance frequency of metal nanoparticles dispersed in anisotropic fluids can be actively controlled，thereby modulating the electro-optical properties of LCs and enhancing the possibilities for luminescence or fluorescence^［16-18］.

LCs serve not only as a medium for doping nanoparticles to improve the photoelectric performance of LC-based devices but also as a mediator in the self-assembly of nanoparticles to construct novel tunable metamaterials for optical applications，which has become a research focus^［19-21］. This non-synthetic method of modifying LCs by adding nanoparticles is more straightforward than traditional chemical synthesis methods and induces new electro-optical characteristics，such as memory effects，opening up numerous rich application prospects. Among these applications，the optical memory effect stands out^［22-23］. It originates from the memory effect of LCs. In nematic LCs filled with nanoparticle suspensions，nanoparticles create defects in the LC phase，breaking the continuous rotational symmetry. Defects generated by doping nanoparticles can cause the LCs surrounding the nanoparticles to tend toward an equilibrium orientation state^［24-25］. Furthermore，under the influence of an electric field，the polarization of nanoparticles will align LCs along the local electric field direction generated by the nanoparticles，thereby altering the overall optical properties of the LCs. This enables LCs to rapidly switch from one optical state to another under the influence of an electric field，facilitating the writing of information^［26］. When the electric field is removed，due to the anchoring effect of the nanoparticles on the LC molecules，the LC molecules can maintain the orientation state formed under the influence of the electric field，thus achieving information storage. These characteristic paves a shortcut for future optical communication，storage，and computing^［27-29］.

In this study，we doped LCs with varying concentrations of molybdenum disulfide（MoS₂）nanoflakes and evaluated the threshold voltage and response time under the influence of an electric field. Since MoS₂ nanosheets can aggregate within the LC matrix and regulate the orientation of the surrounding LCs，they can affect their photoelectric response. Additionally，due to the natural optical anisotropy and orientation changes of LCs under an external electric field，noticeable color changes will also occur under a POM. We attempted to switch the LCs hybrids with varying concentrations of MoS₂ nanoflakes under external electric fields of 5 V and 10 V，respectively，and observed the time required for color changes under POM. Finally，we employed COMSOL software to simulate the electric field variations of MoS₂ at different sizes under 5 V and 10 V voltages. The size and distribution of the doped MoS₂ nanoflakes，and the changes in the external electric field will significantly impact the coupling between LC molecules and MoS₂ nanoflakes.

Preparation of MoS₂ doped LCs：5 mg MoS₂ nanoflakes in the mean size of 2 μm was mixed with 0.5 g 5CB LC to prepare a mass fraction of 0.1% MoS₂ doped LCs，and the prepared mixture was following ultrasonicated for 30 min to increase the suspension of MoS₂ flakes. The mixture was then centrifuged by a desktop high speed centrifuge at 2 000 r/min for 30 s to remove large agglomerates at the bottom，and a series of MoS₂ doped LCs with a much lower concentration of the mass fraction of 0.01% and 0.05%，respectively，were prepared by diluting themass fraction of 0.1% MoS₂ doped LCs with 5CB LCs.

Fabrication of LC-cells：Indium tin oxide（ITO）glass substrates（10 Ω/sq）were washed in acetone and isopropanol under ultrasonication for 20 min，respectively，in order to improve the surface wettability and enhance the adhesion. The substrates then were further cleaned using a digital UV ozone system（PSD UV12，Novascan Technologies，USA）for 30 min. Commercially available PI solution was spin-coated on ITO glass substrates，and the as-prepared substrates were following pre-baked at 100 ℃ for 10 min and baked at 230 ℃ for 1 h by electronic hot plate to evaporate the residual solvents. After being rubbed using a velvet cloth，PI coated substrates were parallelly assembled in rubbing direction to fabricate vertical alignment（VA）mode LC-cells using 60 μm-thick tapes to control the cell gap，and the prepared MoS₂ doped LCs were injected by the usual capillary action method. In addition，VA LC-cells with cell gap 5 μm were fabricated for electro-optical performances evaluation.

Alignment and the electro-optical performance characterization on MoS₂ doped LCs：Alignment of LCs was confirmed by using a polarized optical microscope（POM，DMP750P，Leica），and the voltage-transmittance（V-T）characteristic and the switching time of cells were evaluated using an automatic LC testing system（ALCT-EO1S，Instec）with a step bias voltage of 0.2 V and the maximum bias voltage of 5 V.

The MoS₂ nanoflakes in LCs form agglome‍rates，which influence the orientation of the surrounding LCs. Furthermore，an inner electric field was generated between the two conductive layers when the external voltage was applied to the cell. This was due to the fact that the agglomerates are electrically polarized as a result of their intrinsic excellent surface plasmon polariton（SPP）characteristic. Therefore，the LCs were driven to switch by a dual field under a lower driving voltage. As illustrated in Fig.1 and Tab.1，the blending of MoS₂ nanoflakes in LCs resulted in a notable reduction in the threshold voltage required to attain 90% transmittance. However，the response time for switching between transparent and opaque states exhibited a slight increase. In particular，the threshold voltage of the cell was reduced to 3.90 V by blending with the mass fraction of 0.05% MoS₂ nanoflakes in LCs，representing a 17.20% decrease compared to a pure LC-cell. Additionally，the corresponding decaying time was extended to 70.62 ms，primarily contributing to an increase in the total response time by 10.49%. The extended response time can be attributed to the slow naturalization of electrically charged dipoles on MoS₂ agglomerates.

The switching of LCs under an external electric field was found to induce a significant and noticeable color change under POM due to their natural optical anisotropy and orientation change. This color change observation is believed to be applicable for a wide range of memory devices. The LCs with a negative dielectric permittivity were aligned homeotropically within the cell，and LCs were typically switched to a homogeneous alignment by the external electric field. As shown in Fig.2，the application of an external voltage of 5 V to the cell resulted in the switching of the LCs，which exhibited a pink hue under POM observation. However，the observed pink appearance of LCs was a transient state，and it gradually turned to sand yellow within 261.0 s. The origin of this memory effect is believed to be caused by an alignment defect in the LCs，and the alignment differences and continuity of LCs make this defect expanding，and thus visualized at different paces and times.

Nanomaterials，including graphene and Bi₄Ti₃O₁₂ nanoparticles，have been incorporated into LCs to induce artificial defects. The LCs surrounding the nanoparticles tend to orientate in an equilibrium state，rather than aligning in the direction predicted by theoretical models，which would result from rubbing or other treatments. Additionally，some light leakage is observed. The interaction between LCs and nanoparticles，along with the shape effects and electromagnetic characteristics of these nanoparticles，has led to the conclusion that alignment defects in the LCs host are responsible for accelerating the fading and refreshing of noticeable color changes，which thus features the hybrids with the distinctive memory effect. In this study，MoS₂ nanoflakes were incorporated into LCs to facilitate the positioning of hot spots for defects，thereby accelerating the refresh rate of memory. Upon blending the LCs host with the mass fraction of 0.01% MoS₂ nanoflakes，it was observed that the MoS₂ nanoflakes agglomerated and could be distinguished from the LCs. This phenomenon was clearly visible under POM as shown in Fig.3. The precise alignment of LCs around agglomerates of MoS₂ nanoflakes was identified through the observation of light leakages under POM. When an external voltage of 5 V was applied to the cell，the LCs began to switch，and the cell immediately exhibited a pink hue，similar to that observed in a cell containing only pure LCs. Concurrently，a transient change in color from pink to sand yellow was observed in the vicinity of the MoS₂ agglomerates，with this change occurring rapidly and spreading throughout the observation area. It was observed that in some regions，a distinct grey color emerged concurrently with the sand yellow during the transient process，subsequently diminishing，self-healing and reverting to sand yellow. This is primarily due to the differing orientations of the LCs in response to the external voltage. The transit alignment under the 5 V external voltage was completed in 120.0 s.

Upon the removal of the external voltage，the LCs reverted to their original orientation，resulting in a dark cell. The rate of reorientation was also significantly faster than that observed in the pure LCs cell，indicating that LCs oriented in equilibrium under the external voltage tend to switch to their original orientation. Moreover，it was observed that LCs situated within grey regions exhibit a considerably slower response. It is postulated that this phenomenon is attributable to the fact that the LCs in question were subjected to a considerable degree of external electric field stimulation，which necessitates a longer recovery period for their initial alignment state. This over driving can be observed in the neighboring images，particularly the notable transition of the grey region to sand yellow upon the removal of the external voltage，which subsequently underwent a gradual darkening. Following the removal of the external voltage，some bright lines were observed. A comparison with the preceding POM images revealed that these lines manifested at junctures. This finding corroborates the hypothesis that the chaotic orientation of LCs is impeded by barriers from the neighboring region，thereby preventing the recovery of their initial alignment state.

The rate of color switching increased in a linear fashion as the concentration of MoS₂ nanoflakes in LCs was augmented. As illustrated in Fig.3（b）. Upon increasing the blending concentration of MoS₂ nanoflakes to the mass fraction of 0.05%，the pink LCs exhibited a rapid transition and became a uniform sand yellow within the following 140.0 s. This is due to an increase in the number of agglomerates in the LCs host，which act as hotspots for the generation of alignment defects in LCs. Consequently，the orientation delay occurs in multiple regions and occupies the entire observation area in a short period. The formation of dense agglomerates of MoS₂ nanoflakes not only facilitates the acceleration of alignment delay but also expedites the recovery of LC alignment，and the cell immediately transitioned to a dark state upon the removal of the external voltage. A comparable trend，comprising a transit alignment of 94.0 s was also observed in cells doped with the mass fraction of 0.1% MoS₂ nano-flakes as shown in Fig.3（c）. However，these cells exhibited a greater number of smaller regions in which the LCs were oriented in different directions and displayed a range of colors，including shades of yellow. In addition to the mass fraction of 0.1% MoS₂ nanoflakes blending LCs cell，the aforementioned color differences persist over an extended period and are challenging to self-heal. Such orientation discrepancies may also result in the emergence of bright regions under POM.

When the cells were driven to switch with memory color under an increased external voltage of 10 V，a rapid color change was observed in LCs cells，as illustrated in Fig.4. It was demonstrated that the cell exhibited a markedly accelerated rate of electrically induced alignment switch between the glass slides in the absence of the observed transit pink. Moreover，the transit alignment changes of LCs were observed to be accelerated by approximately 200 s in comparison to the observation of a cell driven at 5 V as shown in Fig.2. This shortened period of alignment transit of LCs thus introduced complications in the coding process during the observation of the transit color. The blending of MoS₂ nanoflakes in LCs was observed to result in a further acceleration of the transit alignment as shown in Fig.5.

This is due to the fact that the higher external voltage induced the super-fast and strong dipole polarization in MoS₂ nanoflakes，which resulted in the generation of super-fast inner electric fields between MoS₂ nanoflakes and thus switched LCs along with the external voltage. It can be observed that the blending of LCs with the mass fraction of 0.1% MoS₂ nano-flakes resulted in a time reduction of 15.5 s in switching transit alignment as shown in Fig.‍5‍（c）. This represents a 48.59% increase in speed compared to the alignment of LCs alone. Furthermore，the recovery time for the alignment to return to a vertical alignment between the slides following the removal of the external voltage was found to be 6.60 s，representing a 50.38% increase in speed compared to the alignment of LCs alone.

A further investigation was conducted to examine the electric field generated around the MoS₂ nanoflakes under the external electric field on cells，with the objective of elucidating the response of MoS₂ in facilitating the faster flip-flop movement of LCs. As shown in Fig.‍6，MoS₂ nanoflakes are initially supposed to be homogeneously aligned in the cell，and the application of an external voltage of 5 V to the cell resulted in the observation of an internal electric field surrounding the thin MoS‍₂ nanoflakes. When the thickness of the thin MoS₂ nanoflakes was 90 nm，the generated field was observed to be relatively small at each side point of the flakes. Upon increasing the thickness of the flakes to 2 µm，a notable enhancement in the generated electric field was observed，accompanied by the formation of a robust electric field around the surface of the flakes. Moreover，the electric field distribution on each side is less pronounced in comparison to that on the top and bottom surfaces. Additionally，the generated electric field was observed to become significantly more pronounced when the surface area of the flakes was significantly increased. The electric field was also observed to be significantly enhanced by increasing the external voltage to 10 V. These findings indicate that both the intrinsic volume and the external voltage on the cells are crucial factors in the alignment defect of the LCs around the MoS₂ nanoflakes，thereby enabling the hybrid to function as an optical memory.

In comparison to homogenously aligned MoS₂ nanoflakes in LCs host，the generation of an electric field at each side point of the MoS₂ nanoflakes was found to be significantly enhanced when they were homeotropically aligned between conductive glass slides as shown in Fig.7. This suggests that under the influence of an external voltage，the orientation of the MoS₂ nanoflakes is biased towards homotropic alignment with the direction of the generated electric field. It can therefore be concluded that the differential thickness of the blended MoS‍₂ flakes，their initial orientation，and their propensity to undergo switching events are the underlying causes of the observed alterations in topological transmission under POM. This provides a clear explanation for why the orientation recovery of the LCs was observed to be significantly slower upon the removal of the external voltage，due to the electrically polarized state of the MoS₂ nanoflakes impeding the recovery of the LCs.

This paper proposed a forward hybrid of MoS‍₂ nanoflakes blending LCs，which exhibits tunable memory behavior. The MoS‍₂ nanoflakes in LCs tend to form agglomerates and become homeotropically aligned under the influence of an external electric field. It was observed that when the driving force exceeded a certain threshold，the alignment of the LCs was disrupted，which in turn resulted in the cessation of their memory behavior. An increase in the concentration of MoS₂ in the hybrid resulted in a significant acceleration of the electro-optical response，thereby enabling the tunable memory behavior. Moreover，an external voltage comparable to the threshold voltage was identified as the optimal voltage for refreshing the memory behavior in the hybrids. In particular，the LCs blended with the mass fraction of 0.1% 2 μm thick MoS‍₂ nanoflakes were found to exhibit a threshold voltage of the hybrid of 3.94 V and a rising time of 63.62 ms. These values represent a 16.3% decrease in comparison to the pure LCs. Upon applying a voltage of 5 V to the hybrid，the memory behavior of the hybrid persisted for 94.0 s before the LCs were fully aligned. The findings presented here indicate a promising approach for the preparation of a memory-behavior-featured LCs hybrid. Furthermore，they elucidate the optimal means of controlling the memory behavior in the hybrid for real-world applications，namely the blending concentration and the applied external driving voltage.