Emergent charge order in pressurized kagome superconductor CsV3Sb5.

The discovery of several electronic orders in kagome superconductors AV3Sb5 (A means K, Rb, Cs) provides a promising platform for exploring unprecedented emergent physics1-9. Under moderate pressure (<2.2 GPa), the triple-Q charge density wave (CDW) order is monotonically suppressed by pressure, while the superconductivity shows a two-dome-like behaviour, suggesting an unusual interplay between superconductivity and CDW order10,11. Given that time-reversal symmetry breaking and electronic nematicity have been revealed inside the triple-Q CDW phase8,9,12,13, understanding this CDW order and its interplay with superconductivity becomes one of the core questions in AV3Sb5 (refs. 3,5,6). Here, we report the evolution of CDW and superconductivity with pressure in CsV3Sb5 by 51V nuclear magnetic resonance measurements. An emergent CDW phase, ascribed to a possible stripe-like CDW order with a unidirectional 4a0 modulation, is observed between Pc1 ≅ 0.58 GPa and Pc2 ≅ 2.0 GPa, which explains the two-dome-like superconducting behaviour under pressure. Furthermore, the nuclear spin-lattice relaxation measurement reveals evidence for pressure-independent charge fluctuations above the CDW transition temperature and unconventional superconducting pairing above Pc2. Our results not only shed new light on the interplay of superconductivity and CDW, but also reveal new electronic correlation effects in kagome superconductors AV3Sb5.

Charge-density-wave-driven electronic nematicity in a kagome superconductor.

Electronic nematicity, in which rotational symmetry is spontaneously broken by electronic degrees of freedom, has been demonstrated as a ubiquitous phenomenon in correlated quantum fluids including high-temperature superconductors and quantum Hall systems1,2. Notably, the electronic nematicity in high-temperature superconductors exhibits an intriguing entanglement with superconductivity, generating complicated superconducting pairing and intertwined electronic orders. Recently, an unusual competition between superconductivity and a charge-density-wave (CDW) order has been found in the AV3Sb5 (A = K, Rb, Cs) family with two-dimensional vanadium kagome nets3-8. Whether these phenomena involve electronic nematicity is still unknown. Here we report evidence for the existence of electronic nematicity in CsV3Sb5, using a combination of elastoresistance measurements, nuclear magnetic resonance (NMR) and scanning tunnelling microscopy/spectroscopy (STM/S). The temperature-dependent elastoresistance coefficient (m11 minus m12) and NMR spectra demonstrate that, besides a C2 structural distortion of the 2a0 × 2a0 supercell owing to out-of-plane modulation, considerable nematic fluctuations emerge immediately below the CDW transition (approximately 94 kelvin) and finally a nematic transition occurs below about 35 kelvin. The STM experiment directly visualizes the C2-structure-pinned long-range nematic order below the nematic transition temperature, suggesting a novel nematicity described by a three-state Potts model. Our findings indicate an intrinsic electronic nematicity in the normal state of CsV3Sb5, which sets a new paradigm for revealing the role of electronic nematicity on pairing mechanism in unconventional superconductors.

LncRNA DANA1 promotes drought tolerance and histone deacetylation of drought responsive genes in Arabidopsis.

Although many long noncoding RNAs have been discovered in plants, little is known about their biological function and mode of action. Here we show that the drought-induced long intergenic noncoding RNA DANA1 interacts with the L1p/L10e family member protein DANA1-INTERACTING PROTEIN 1 (DIP1) in the cell nucleus of Arabidopsis, and both DANA1 and DIP1 promote plant drought resistance. DANA1 and DIP1 increase histone deacetylase HDA9 binding to the CYP707A1 and CYP707A2 loci. DIP1 further interacts with PWWP3, a member of the PEAT complex that associates with HDA9 and has histone deacetylase activity. Mutation of DANA1 enhances CYP707A1 and CYP707A2 acetylation and expression resulting in impaired drought tolerance, in agreement with dip1 and pwwp3 mutant phenotypes. Our results demonstrate that DANA1 is a positive regulator of drought response and that DANA1 works jointly with the novel chromatin-related factor DIP1 on epigenetic reprogramming of the plant transcriptome during the response to drought.

Logic-in-memory based on an atomically thin semiconductor.

The growing importance of applications based on machine learning is driving the need to develop dedicated, energy-efficient electronic hardware. Compared with von Neumann architectures, which have separate processing and storage units, brain-inspired in-memory computing uses the same basic device structure for logic operations and data storage1-3, thus promising to reduce the energy cost of data-centred computing substantially4. Although there is ample research focused on exploring new device architectures, the engineering of material platforms suitable for such device designs remains a challenge. Two-dimensional materials5,6 such as semiconducting molybdenum disulphide, MoS2, could be promising candidates for such platforms thanks to their exceptional electrical and mechanical properties7-9. Here we report our exploration of large-area MoS2 as an active channel material for developing logic-in-memory devices and circuits based on floating-gate field-effect transistors (FGFETs). The conductance of our FGFETs can be precisely and continuously tuned, allowing us to use them as building blocks for reconfigurable logic circuits in which logic operations can be directly performed using the memory elements. After demonstrating a programmable NOR gate, we show that this design can be simply extended to implement more complex programmable logic and a functionally complete set of operations. Our findings highlight the potential of atomically thin semiconductors for the development of next-generation low-power electronics.

Chiral superconductivity in heavy-fermion metal UTe2.

Spin-triplet superconductors are condensates of electron pairs with spin 1 and an odd-parity wavefunction1. An interesting manifestation of triplet pairing is the chiral p-wave state, which is topologically non-trivial and provides a natural platform for realizing Majorana edge modes2,3. However, triplet pairing is rare in solid-state systems and has not been unambiguously identified in any bulk compound so far. Given that pairing is usually mediated by ferromagnetic spin fluctuations, uranium-based heavy-fermion systems containing f-electron elements, which can harbour both strong correlations and magnetism, are considered ideal candidates for realizing spin-triplet superconductivity4. Here we present scanning tunnelling microscopy studies of the recently discovered heavy-fermion superconductor UTe2, which has a superconducting transition temperature of 1.6 kelvin5. We find signatures of coexisting Kondo effect and superconductivity that show competing spatial modulations within one unit cell. Scanning tunnelling spectroscopy at step edges reveals signatures of chiral in-gap states, which have been predicted to exist at the boundaries of topological superconductors. Combined with existing data that indicate triplet pairing in UTe2, the presence of chiral states suggests that UTe2 is a strong candidate for chiral-triplet topological superconductivity.

Development potential of nanoenabled agriculture projected using machine learning.

The controllability and targeting of nanoparticles (NPs) offer solutions for precise and sustainable agriculture. However, the development potential of nanoenabled agriculture remains unknown. Here, we build an NP-plant database containing 1,174 datasets and predict (R2 higher than 0.8 for 13 random forest models) the response and uptake/transport of various NPs by plants using a machine learning approach. Multiway feature importance analysis quantitatively shows that plant responses are driven by the total NP exposure dose and duration and plant age at exposure, as well as the NP size and zeta potential. Feature interaction and covariance analysis further improve the interpretability of the model and reveal hidden interaction factors (e.g., NP size and zeta potential). Integration of the model, laboratory, and field data suggests that Fe2O3 NP application may inhibit bean growth in Europe due to low night temperatures. In contrast, the risks of oxidative stress are low in Africa because of high night temperatures. According to the prediction, Africa is a suitable area for nanoenabled agriculture. The regional differences and temperature changes make nanoenabled agriculture complicated. In the future, the temperature increase may reduce the oxidative stress in African bean and European maize induced by NPs. This study projects the development potential of nanoenabled agriculture using machine learning, although many more field studies are needed to address the differences at the country and continental scales.

The U1 small nuclear RNA enhances drought tolerance in Arabidopsis.

Alternative splicing (AS) is an important posttranscriptional regulatory mechanism that improves plant tolerance to drought stress by modulating gene expression and generating proteome diversity. The interaction between the 5' end of U1 small nuclear RNA (U1 snRNA) and the conserved 5' splice site of precursor messenger RNA (pre-mRNA) is pivotal for U1 snRNP involvement in AS. However, the roles of U1 snRNA in drought stress responses remain unclear. This study provides a comprehensive analysis of AtU1 snRNA in Arabidopsis (Arabidopsis thaliana), revealing its high conservation at the 5' end and a distinctive four-leaf clover structure. AtU1 snRNA is localized in the nucleus and expressed in various tissues, with prominent expression in young floral buds, flowers, and siliques. The overexpression of AtU1 snRNA confers enhanced abiotic stress tolerance, as evidenced in seedlings by longer seedling primary root length, increased fresh weight, and a higher greening rate compared with the wild-type. Mature AtU1 snRNA overexpressor plants exhibit higher survival rates and lower water loss rates under drought stress, accompanied by a significant decrease in H2O2 and an increase in proline. This study also provides evidence of altered expression levels of drought-related genes in AtU1 snRNA overexpressor or genome-edited lines, reinforcing the crucial role of AtU1 snRNA in drought stress responses. Furthermore, the overexpression of AtU1 snRNA influences the splicing of downstream target genes, with a notable impact on SPEECHLESS (SPCH), a gene associated with stomatal development, potentially explaining the observed decrease in stomatal aperture and density. These findings elucidate the critical role of U1 snRNA as an AS regulator in enhancing drought stress tolerance in plants, contributing to a deeper understanding of the AS pathway in drought tolerance and increasing awareness of the molecular network governing drought tolerance in plants.

RNA splicing modulates the postharvest physiological deterioration of cassava storage root.

Rapid postharvest physiological deterioration (PPD) of cassava (Manihot esculenta Crantz) storage roots is a major constraint that limits the potential of this plant as a food and industrial crop. Extensive studies have been performed to explore the regulatory mechanisms underlying the PPD processes in cassava to understand their molecular and physiological responses. However, the exceptional functional versatility of alternative splicing (AS) remains to be explored during the PPD process in cassava. Here, we identified several aberrantly spliced genes during the early PPD stage. An in-depth analysis of AS revealed that the abscisic acid (ABA) biosynthesis pathway might serve as an additional molecular layer in attenuating the onset of PPD. Exogenous ABA application alleviated PPD symptoms through maintaining ROS generation and scavenging. Interestingly, the intron retention transcript of MeABA1 (ABA DEFICIENT 1) was highly correlated with PPD symptoms in cassava storage roots. RNA yeast 3-hybrid and RNA immunoprecipitation (RIP) assays showed that the serine/arginine-rich protein MeSCL33 (SC35-like splicing factor 33) binds to the precursor mRNA of MeABA1. Importantly, overexpressing MeSCL33 in cassava conferred improved PPD resistance by manipulating the AS and expression levels of MeABA1 and then modulating the endogenous ABA levels in cassava storage roots. Our results uncovered the pivotal role of the ABA biosynthesis pathway and RNA splicing in regulating cassava PPD resistance and proposed the essential roles of MeSCL33 for conferring PPD resistance, broadening our understanding of SR proteins in cassava development and stress responses.

PSEUDO-RESPONSE REGULATOR 3b and transcription factor ABF3 modulate abscisic acid-dependent drought stress response in soybean.

The circadian system plays a pivotal role in facilitating the ability of crop plants to respond and adapt to fluctuations in their immediate environment effectively. Despite the increasing comprehension of PSEUDO-RESPONSE REGULATORs and their involvement in the regulation of diverse biological processes, including circadian rhythms, photoperiodic control of flowering, and responses to abiotic stress, the transcriptional networks associated with these factors in soybean (Glycine max (L.) Merr.) remain incompletely characterized. In this study, we provide empirical evidence highlighting the significance of GmPRR3b as a crucial mediator in regulating the circadian clock, drought stress response, and abscisic acid (ABA) signaling pathway in soybeans. A comprehensive analysis of DNA affinity purification sequencing and transcriptome data identified 795 putative target genes directly regulated by GmPRR3b. Among them, a total of 570 exhibited a significant correlation with the response to drought, and eight genes were involved in both the biosynthesis and signaling pathways of ABA. Notably, GmPRR3b played a pivotal role in the negative regulation of the drought response in soybeans by suppressing the expression of abscisic acid-responsive element-binding factor 3 (GmABF3). Additionally, the overexpression of GmABF3 exhibited an increased ability to tolerate drought conditions, and it also restored the hypersensitive phenotype of the GmPRR3b overexpressor. Consistently, studies on the manipulation of GmPRR3b gene expression and genome editing in plants revealed contrasting reactions to drought stress. The findings of our study collectively provide compelling evidence that emphasizes the significant contribution of the GmPRR3b-GmABF3 module in enhancing drought tolerance in soybean plants. Moreover, the transcriptional network of GmPRR3b provides valuable insights into the intricate interactions between this gene and the fundamental biological processes associated with plant adaptation to diverse environmental conditions.

WRKY53 negatively regulates rice cold tolerance at the booting stage by fine-tuning anther gibberellin levels.

Cold tolerance at the booting (CTB) stage is a major factor limiting rice (Oryza sativa L.) productivity and geographical distribution. A few cold-tolerance genes have been identified, but they either need to be overexpressed to result in CTB or cause yield penalties, limiting their utility for breeding. Here, we characterize the function of the cold-induced transcription factor WRKY53 in rice. The wrky53 mutant displays increased CTB, as determined by higher seed setting. Low temperature is associated with lower gibberellin (GA) contents in anthers in the wild type but not in the wrky53 mutant, which accumulates slightly more GA in its anthers. WRKY53 directly binds to the promoters of GA biosynthesis genes and transcriptionally represses them in anthers. In addition, we uncover a possible mechanism by which GA regulates male fertility: SLENDER RICE1 (SLR1) interacts with and sequesters two critical transcription factors for tapetum development, UNDEVELOPED TAPETUM1 (UDT1), and TAPETUM DEGENERATION RETARDATION (TDR), and GA alleviates the sequestration by SLR1, thus allowing UDT1 and TDR to activate transcription. Finally, knocking out WRKY53 in diverse varieties increases cold tolerance without a yield penalty, leading to a higher yield in rice subjected to cold stress. Together, these findings provide a target for improving CTB in rice.

Ultrathin Transistors and Circuits for Conformable Electronics.

Adapting electronics to perfectly conform to nonplanar and rough surfaces, such as human skin, is a challenging task, which could open up new applications in fields of high economic and scientific interest, ranging from health to robotics, human-machine interface, and Internet of Things. The key to success lies in defining a technology that can lead to ultrathin devices, exploiting ultimately thin materials, with high mechanical flexibility and excellent electrical properties. Here, we report a hybrid approach for the development of high-performance, ultrathin and conformable electronic devices, based on the integration of semiconducting transition metal dichalcogenides, i.e., MoS2, with organic gate dielectric material, i.e., polyvinyl formal (PVF) combined with inkjet printed PEDOT:PSS electrodes. Through this novel approach, transistors and simple digital and analogue circuits are fabricated by a sequential stacking of ultrathin (nanometer) layers on a few micrometers thick polyimide substrate, which guarantees the high flexibility mandatory for the targeted applications.

Uncovering Maximum Chirality in Resonant Nanostructures.

Chiral nanostructures allow engineering of chiroptical responses; however, their design usually relies on empirical approaches and extensive numerical simulations. It remains unclear if a general strategy exists to enhance and maximize the intrinsic chirality of subwavelength photonic structures. Here, we suggest a microscopic theory and uncover the origin of strong chiral responses of resonant nanostructures. We reveal that the reactive helicity density is critically important for achieving maximum chirality at resonances. We demonstrate our general concept on the examples of planar photonic crystal slabs and metasurfaces, where out-of-plane mirror symmetry is broken by a bilayer design. Our findings provide a general recipe for designing photonic structures with maximum chirality, paving the way toward many applications, including chiral sensing, chiral emitters and detectors, and chiral quantum optics.

Unraveling Eumelanin Radical Formation by Nanodiamond Optical Relaxometry in a Living Cell.

Defect centers in a nanodiamond (ND) allow the detection of tiny magnetic fields in their direct surroundings, rendering them as an emerging tool for nanoscale sensing applications. Eumelanin, an abundant pigment, plays an important role in biology and material science. Here, for the first time, we evaluate the comproportionation reaction in eumelanin by detecting and quantifying semiquinone radicals through the nitrogen-vacancy color center. A thin layer of eumelanin is polymerized on the surface of nanodiamonds (NDs), and depending on the environmental conditions, such as the local pH value, near-infrared, and ultraviolet light irradiation, the radicals form and react in situ. By combining experiments and theoretical simulations, we quantify the local number and kinetics of free radicals in the eumelanin layer. Next, the ND sensor enters the cells via endosomal vesicles. We quantify the number of radicals formed within the eumelanin layer in these acidic compartments by applying optical relaxometry measurements. In the future, we believe that the ND quantum sensor could provide valuable insights into the chemistry of eumelanin, which could contribute to the understanding and treatment of eumelanin- and melanin-related diseases.

Quantitative regulation of electron-phonon coupling.

Electron-phonon (e-p) coupling plays a crucial role in various physical phenomena, and regulation of e-p coupling is vital for the exploration and design of high-performance materials. However, the current research on this topic lacks accurate quantification, hindering further understanding of the underlying physical processes and its applications. In this work, we demonstrate quantitative regulation of e-p coupling, by pressure engineering andin-situspectroscopy. We successfully observe both a distinct vibrational mode and a strong Stokes shift in layered CrBr3, which are clear signatures of e-p coupling. This allows us to achieve precise quantification of the Huang-Rhys factorSat the actual sample temperature, thus accurately determining the e-p coupling strength. We further reveal that pressure efficiently regulates the e-p coupling in CrBr3, evidenced by a remarkable 40% increase inSvalue. Our results offer an approach for quantifying and modulating e-p coupling, which can be leveraged for exploring and designing functional materials with targeted e-p coupling strengths.

Revealing Hydrogen Spillover on 1T/2H MoS2 Heterostructures for an Enhanced Hydrogen Evolution Reaction by Scanning Electrochemical Microscopy.

The in situ characterization of the heterostructure active sites during the hydrogen evolution reaction (HER) process and the direct elucidation of the corresponding catalytic structure-activity relationships are essential for understanding the catalytic mechanism and designing catalysts with optimized activity. Hence, exploring the underlying reasons behind the exceptional catalytic performance necessitates a detailed analysis. Herein, we employed scanning electrochemical microscopy (SECM) to in situ image the topography and local electrocatalytic activity of 1T/2H MoS2 heterostructures on mixed-phase molybdenum disulfide (MoS2) with 20 nm spatial resolution. Our measurements provide direct data about HER activity, enabling us to differentiate the superior catalytic performance of 1T/2H MoS2 heterostructures compared to other active sites on the MoS2 surface. Combining this spatially resolved electrochemical information with density functional theory calculations and numerical simulations enables us to reveal the existence of hydrogen spillover from the 1T MoS2 surface to 1T/2H MoS2 heterostructures. Furthermore, it has been verified that hydrogen spillover can significantly enhance the electrocatalytic activity of the heterostructures, in addition to its strong electronic interaction. This study not only contributes to the future investigation of electrochemical processes at nanoscale active sites on structurally complex electrocatalysts but also provides new design strategies for improving the catalytic activity of 2D electrocatalysts.

Persistent Luminescence Nanoplatform for Autofluorescence-Free Tracking of Submicrometer Plastic Particles in Plant.

The uptake of plastic particles by plants and their transport through the food chain make great risks to biota and human health. Therefore, it is important to trace plastic particles in the plant. Traditional fluorescence imaging in plants usually suffers significant autofluorescence background. Here, we report a persistent luminescence nanoplatform for autofluorescence-free imaging and quantitation of submicrometer plastic particles in plant. The nanoplatform was fabricated by doping persistent luminescence nanoparticles (PLNPs) onto polystyrene (PS) nanoparticles. Cr3+-doped zinc gallate PLNP was employed as the dopant for autofluorescence-free imaging due to its persistent luminescence nature. In addition, the Ga element in PLNP was used as a proxy to quantify the PS in the plant by inductively coupled plasma mass spectrometry (ICP-MS). Thus, the developed nanoplatform allows not only dual-mode autofluorescence-free imaging (persistent luminescence and laser-ablation ICP-MS) but also ICP-MS quantitation for tracking PS in plant. Application of this nanoplatform in a typical plant model Arabidopsis thaliana revealed that PS mainly distributed in the root (>99.45%) and translocated very limited (<0.55%) to the shoot. The developed nanoplatform has great potential for quantitative tracing of submicrometer plastic particles to investigate the environmental process and impact of plastic particles.

Transcriptome sequencing and expression analysis in peanut reveal the potential mechanism response to Ralstonia solanacearum infection.

BACKGROUND: Bacterial wilt caused by Ralstonia solanacearum severely affects peanut (Arachis hypogaea L.) yields. The breeding of resistant cultivars is an efficient means of controlling plant diseases. Therefore, identification of resistance genes effective against bacterial wilt is a matter of urgency. The lack of a reference genome for a resistant genotype severely hinders the process of identification of resistance genes in peanut. In addition, limited information is available on disease resistance-related pathways in peanut. RESULTS: Full-length transcriptome data were used to generate wilt-resistant and -susceptible transcript pools. In total, 253,869 transcripts were retained to form a reference transcriptome for RNA-sequencing data analysis. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis of differentially expressed genes revealed the plant-pathogen interaction pathway to be the main resistance-related pathway for peanut to prevent bacterial invasion and calcium plays an important role in this pathway. Glutathione metabolism was enriched in wilt-susceptible genotypes, which would promote glutathione synthesis in the early stages of pathogen invasion. Based on our previous quantitative trait locus (QTL) mapping results, the genes arahy.V6I7WA and arahy.MXY2PU, which encode nucleotide-binding site-leucine-rich repeat receptor proteins, were indicated to be associated with resistance to bacterial wilt. CONCLUSIONS: This study identified several pathways associated with resistance to bacterial wilt and identified candidate genes for bacterial wilt resistance in a major QTL region. These findings lay a foundation for investigation of the mechanism of resistance to bacterial wilt in peanut.

Unraveling the Role of Metal Vacancy Sites and Doped Nitrogen in Enhancing Pseudocapacitance Performance of Defective MXene.

Nitrogen-doped titanium carbides (MXene) films exhibit extraordinary volumetric capacitance when high-concentration sulfuric acid electrolyte is utilized owing to the enhancement of pseudocapacitance. However, the energy storage mechanism of nitrogen-doped MXene is unclear due to the complex electrode structure and electrolyte ions' behavior. Here, based on pristine MXene (Ti3C2O2), three different MXene structures are constructed by introducing metal vacancy sites and doped nitrogen atoms, namely, defective MXene (Ti2.9C2O2), nitrogen-doped MXene (Ti3C2O1.9N0.1), and nitrogen-doped MXene with metal vacancy sites (Ti2.9C2O1.9N0.1). Then, the density functional theory (DFT)-based calculations coupled with the effective screening medium reference interaction site method (ESM-RISM) are applied to reveal the electrochemical behavior at the electrode/electrolyte interfacial area. Through analyzing the electronic structure, electrical double-layer capacitance (EDLC), and equilibrium potential of the pseudocapacitance reaction, the specific effect of structural changes on their performance can be clarified: metal vacancy sites can reduce the potential difference of gap layer (Outer Helmholtz plane) at charged state and increase the electronic capacity of Ti, which can be used to explain the high pseudocapacitance, low charge transfer resistance and high-rate capacity properties of nitrogen-doped MXene observed in experiments.

3D Printing-Induced Hierarchically Aligned Nanocomposites With Exceptional Multidirectional Strain Sensing Performance.

High-performance sensors capable of detecting multidirectional strains are indispensable to understand the complex motions involved in flexible electronics. Conventional isotropic strain sensors can only measure uniaxial deformations or single stimuli, hindering their practical application fields. The answer to such challenge resides in the construction of engineered anisotropic sensing structures. Herein, a hierarchically aligned carbon nanofiber (CNF)/polydimethylsiloxane nanocomposite strain sensor is developed by one-step 3D printing. The precisely controlled printing path and shear flow bring about highly aligned nanocomposite filaments at macroscale and orientated CNF network within each filament at microscale. The periodically orientated nanocomposite filaments along with the inner aligned CNF network successfully control the strain distribution and the appearance of microcracks, giving rise to anisotropic structural response to external deformations. The synergetic effect of the multiscale structural design leads to distinguishable gauge factors of 164 and 0.5 for applied loadings along and transverse to the alignment direction, leading to an exceptional selectivity of 3.77. The real-world applications of the hierarchically aligned sensors in multiaxial movement detector and posture-correction device are further demonstrated. The above findings propose new ideas for manufacturing nanocomposites with engineered anisotropic structure and properties, verifying promising applications in emerging wearable electronics and soft robotics.

Unraveling the Ionic Storage Mechanism of Flexible Nitrogen-Doped MXene Films for High-Performance Aqueous Hybrid Supercapacitors.

2D MXene nanomaterials have excellent potential for application in novel electrochemical energy storage technologies such as supercapacitors and batteries, but the existing pure MXene is difficult to meet the practical needs. Although the electrochemical properties of modified MXene have been improved, the unclear ion storage mechanism still hinders the development of MXene-based electrode materials. Herein, the study develops flexible self-supported nitrogen-doped Ti3C2 (Py-Ti3C2) films by the highly mobile, high nitrogen content, oxygen-free pyridine-assisted solvothermal method, and then deeply investigates the energy storage mechanism of hybrid supercapacitors in four aqueous electrolytes (H2SO4, Li2SO4, Na2SO4, and MgSO4). The experimental results suggest that the Py-Ti3C2 film electrode exhibits a pseudocapacitance-dominated energy storage mechanism. Particularly, the specific capacity of the Py-Ti3C2 in 1 M H2SO4 (506 F g-1 at 0.1 A g-1) is 4-5 times higher than other electrolytes (≈110 F g-1), which could be attributed to the substantially higher ionic diffusion coefficient of H+ than those of Li+, Na+, Mg2+ with small ionic size, high ionic conductivity, and fast pseudocapacitance response. Theoretical analysis further confirms that Py-Ti3C2 has strengthened conductivity and electrical double-layer capacitance performance. Meanwhile, it has lower free energy for protonation and deprotonation of functional groups, which gives excellent pseudocapacitance performance.