Single Nanosheets Research Articles

2D-layered Bi-functional direct solid-Z-scheme heterogenous vanadium and oxygen doped graphitic carbon nitride single layered nanosheet catalysis for detection and photocatalytic removal of toxic heavy metal

In this Research, the “Get the two Mangoes with one stone” strategy was utilized to investigate the electrochemical detection and photocatalytic removal of mercury ions (Hg2+) using vanadium pentoxide doped graphitic carbon nitride (V2O5/gCN) nanosheets for the first time. The proposed materials can be better choice for environmental issues. In this research, a novel direct Z-scheme V2O5/gCN nanosheets were prepared through direct thermal decomposition techniques with the different (0.1–0.5 wt%) weight ratios of dopant materials. The prepared nanosheets physiochemical properties can be obtained through various characterizations techniques. Moreover, the prepared nanosheets exhibit an excellent electrochemical ability for the detection of Hg2+ ions with a limit of detection is 9.2 nM, linear range from 0.2 to 100 μM, and enormous sensitivity (9.9857 μA μM−1 cm−2), respectively. Furthermore, the higher photocatalytic removal efficiency was obtained in this optimized dopant (0.2 wt%) concentration of V2O5-doped gCN nanosheets. In addition, the complete removal was obtained within a short treatment time under the visible light irradiation. Furthermore, the target (Hg2+) ions removals are quantified by ICP-OES, and quantification values were found to be 2762 ppm and 101 ppm before and after treatments, respectively. Therefore, this research work will be beneficial for the design of direct Z-scheme photo-electrocatalytic systems for application in real-time detection and environmental remediation.

Design of InAs nanosheet arrays for high-performance polarization-sensitive infrared photodetection

Polarization-sensitive infrared photodetectors are widely needed to distinguish an object from its surrounding environment. Polarization-sensitive detection can be realized by using semiconductors with anisotropic geometry or anisotropic crystal arrangement, such as semiconductor nanowires and two-dimensional (2D) materials. However, these photodetectors show drawbacks in low light absorption, weak polarization sensitivity and stability issues. Here, we designed 2D InAs nanosheet based arrays that are highly suitable for polarization-sensitive infrared photodetection. By using the finite element method (FEM) based on COMSOL Multiphysics, we optimized the geometry of single free-standing InAs nanosheets, obtaining dichroic ratio up to 127 (average) in the wavelength range of 2–3 μm by reducing the thickness and increasing the height. Extending this to a nanosheet array with an optimized geometry, an enhancement of the absorption intensity from 45% (for a single nanosheet) to over 67% with a dichroic ratio exceeding 50 in the wavelength range of 2–3 μm can be achieved. Moreover, these unique light absorption properties are tolerant to incident angles up to 30°. The design of such nanosheet array provides a new route for the development of high-performance infrared photodetectors for polarization photodetection.

Hierarchical simulation of nanosheet field effect transistor: NESS flow

Nanosheet gate-all-around transistor devices have been an important contenders for future technology nodes. Compared to FinFETs they have superior electrostatic control. The nanosheet architecture can also be vertically stacked thus achieving higher drive current on a same footprint area compared to a single nanowire or nanosheet. Accurate device simulations are crucial for the development and the optimization of the nanosheet transistors. With this in mind, we have developed and report a hierarchical simulations flow implemented in the Glasgow Nano-Electronic Simulation Software (NESS) in order to enable the accurate simulation and optimization of the nanosheet transistors. In this work we have carried out device simulations and showed that the more accurate NEGF simulations can be used for the calibration of the classical DD simulations within one single toolbox. Additionally we showed that the EME module can be used to extract the effective masses for confined structure like the nanosheet.

Liquid-phase exfoliation of graphitic carbon nitrides studied by molecular dynamics simulation

HypothesisThe superiority of graphitic carbon nitride (g-C3N4) nanosheet results from its large specific surface area, which can be achieved by exfoliation of the bulk layered structure. Liquid-phase exfoliation (LPE) is the best-known method for the synthesis of two-dimensional (2D) g-C3N4 nanosheets. However, experimental investigations do not allow for a molecular-level understanding of the process. Molecular dynamics (MD) simulations are expected to provide microscopic insights and quantitative evaluation of the energy consumption during LPE, thus facilitating the search of effective solvents for the LPE of 2D materials. SimulationsMD simulations are carried out to simulate the LPE process by performing potential of mean force calculations for the separation of two stacked g-C3N4 nanosheets. Free energy of exfoliation is evaluated and compared among nine common solvents with distinct molecular structures. FindingsThe most probable path for the exfoliation process is identified. The free energy of exfoliation is found to correlate directly with the solvent free energy of a single g-C3N4 nanosheet. The solvation is enthalpy-driven and affected by the mobility of the solvent molecules around the nanosheet. Based on the MD results, several strategies are proposed to guide the selection of solvents for effective LPE.

Rational Design of NiSe/ReSe2 Nanocomposite For Efficient Electrochemical Hydrogen Evolution Reaction

The hydrogen evolution reaction (HER) in renewable energy systems has long been a fascinating process, but designing highly efficient and ultrastable electrocatalysts is challenging. Transition metal-based heterostructure nanohybrids are currently drawing more interest in the field of electrolysis because nanohybids can optimize kinetic processes while simultaneously lowering charge transfer resistance and increasing the electrochemically active electrode’s surface area at the reaction interface. Here, we propose a concept for a two-step colloidal hot injection electrocatalyst based on NiSe/ReSe2 nanocomposites that is extremely effective for hydrogen evolution under acidic conditions. The as-obtained nanocomposite material worked efficiently, attaining a current density of 10 mA cm−2 at a substantially lower over-potential of 120 mV vs RHE as compared to each of the individual components i.e. NiSe nanoparticles and ReSe2 nanosheets. As single component catalysts, ReSe2 nanosheets and NiSe nanoparticles, however, achieved current densities of 10 mA cm−2 at higher overpotentials of 172 mV and 221 mV, respectively. Even more intriguingly, the NiS/ReSe2 nanocomposite is believed to give a faster kinetic process for HER, as evidenced by a Tafel slope of 115 mV dec−1, which certainly is lower than that of the 179 mV dec−1 and 190 mV dec−1 for pure NiSe and ReSe2, respectively. NiSe nanocrystallites and ReSe2 nanosheets were assumed to be working in a synergistic manner to generate the electronic structural modification that led to the noticeably increased electrocatalytic properties. In order to make highly tuned electrocatalysts in solids, we anticipate that the fabrication of hybrid structures will be a successful strategy.

Highly Tunable Beyond-Room-Temperature Intrinsic Ferromagnetism in Cr-Doped Topological Crystalline Insulator SnTe Crystals.

The combination of topological phase and intrinsic beyond-room-temperature ferromagnetism is expected to realize the quantum anomalous Hall effect at a high temperature. However, no beyond-room-temperature intrinsic ferromagnetism has been reported in either topological insulator or topological crystalline insulator (TCI) so far. Here, we report Cr-doping in TCI-phase SnTe crystals which possess highly tunable beyond-room-temperature intrinsic ferromagnetism including Tc, magnetic moment, and coercivity by varying Cr contents and crystal thickness. With the increase of the Cr content, the Tc increases by 159 K from 221 to 380 K and the saturation magnetic moments increase by ∼23.6 times from 0.018 to 0.421 μB/f.u. This intrinsic beyond-room-temperature ferromagnetism is fully demonstrated by the anomalous Hall effect and magneto-optical Kerr effect in a single CrxSn1-xTe nanosheet. Moreover, the room-temperature tunneling magnetoresistance effect has been realized by using a CrxSn1-xTe flake, a Fe thin film, and a commercially compatible ultrathin AlOx tunneling barrier. This work indicates a great potential of CrxSn1-xTe crystals in room-temperature magnetoelectronic and spintronic devices.

Lithographic Multicolor Patterning on Hybrid Perovskites for Nano-Optoelectronic Applications.

Ultrathin hybrid perovskites, with exotic properties and two-dimensional geometry, exhibit great potential in nanoscale optical and optoelectronic devices. However, it is still challenging for them to be compatible with high-resolution patterning technology toward miniaturization and integration applications, as they can be readily damaged by the organic solvents used in standard lithography processes. Here, a flexible three-step method is developed to make high-resolution multicolor patterning on hybrid perovskite, particularly achieved on a single nanosheet. The process includes first synthesis of precursor PbI2 , then e-beam lithography and final conversion to target perovskite. The patterns with linewidth around 150nm can be achieved, which can be applied in miniature optoelectronic devices and high-resolution displays. As an example, the channel length of perovskite photodetectors can be down to 126nm. Through deterministic vapor-phase anion exchange, a perovskite nanosheet can not only gradually alter the color of the same pattern in a wide wavelength range, but also display different colors simultaneously. The authors are optimistic that the method can be applied for unlimited perovskite types and device configurations for their high-integrated miniature applications.

Carbon nanosheets prepared with a vermiculite template for high-performance lithium-ion batteries via space-confined carbonization strategy

Carbon nanosheets (CNSs) having both graphite microcrystalline layers and amorphous carbon structures are prepared by a space-confined carbonization strategy using glucose, sucrose and starch as carbon sources which are inserted into the confined space of vermiculite templates by liquid-phase impregnation intercalation. The microstructures of CNSs are strongly depended on the molecular weight of carbon precursors. In the Starch-CNSs synthesized from starch with larger molecular weight, single nanosheets contain more ordered graphite microcrystalline layers and fewer microporous defects as well as richer oxygen-containing functional groups, and the disordered stacking of single nanosheets form more mesoporous structures. The specific surface area and nanosheets thickness of Starch-CNSs are 400 m2·g−1 and 3.934 nm. Starch-CNSs as anode for lithium-ion batteries exhibit excellent lithium storage properties, combining initial Coulombic efficiency (56 %), high specific capacity (637mAh/g at 0.05 A/g), excellent rate performance (253 mAh/g at 2 A/g) and cycling stability (262 mAh/g at 2 A/g after 500 cycles). These results show the CNSs derived from larger molecular weights outperform these from lower counterparts, providing strong evidence and reference for selecting suitable molecular weight carbon precursors to prepare high-performance CNSs anode for lithium ion batteries.

Large bandgap insulating superior clay nanosheets

One can find conductive, semiconducting, and insulating single nanosheets with unique electronic properties that are tied to their two-dimensional (2D) structure. Here, we report on wide-bandgap 2D insulator nanosheets obtained by delamination of a synthetic 2D fluorohectorite clay mineral showing one of the largest bandgap insulators in the world. The bandgap was determined experimentally to be up to 7.1–8.2 eV measured by electron energy-loss spectroscopy in a high-resolution transmission electron microscope. The experimental data were supported by DFT calculations giving a bandgap of 5.5 eV. The single fluorohectorite clay crystalline nanosheets are 0.95-nm, and they can be synthetized with high-aspect ratios and lateral dimensions up to dozens of microns. These properties render these nanosheets promising candidates for practical applications in manually assembled or self-assembled electronic heterostructures, potentially serving as insulating nanosheets in graphene or various (semi)conductive 2D material-based devices.Impact statementProperties of the synthetic fluorohectorite clay presented in this article render these 0.95-nm-thin nanosheets promising candidates for practical applications in manually assembled or self-assembled electronic heterostructures, potentially serving as insulating nanosheets in graphene or various (semi)conductive 2D material-based devices.The information provided in this work can be essential for the growing community focused on the study of 2D materials and their wide range of applications.Graphical abstract

Flash dual-engineering of surface carboxyl defects and single Cu atoms of g-C3N4 via unique CO2 plasma immersion approach for boosted photocatalytic activity

Single transition metal atom embedding and functional group defect engineering is commonly utilized to optimize the electronic band structure of g-C3N4. However, most dual modification method suffers from the destruction of structure and active sites. Herein, single atom Cu and carboxyl group dual-endowed g-C3N4 nanosheets with a tunable bandgap were prepared by employing a facile CO2 plasma method. Experiments and density functional theory calculation show that the dual modification leads to a decreased bandgap and reconstructed local charge distribution to promote the separation of photogenerated charge carriers. As a result, the optimal Cu–CN–CO2-6min perform well in photo-Fenton degradation of dye and photocatalytic generation of H2. The synergy mechanism can be ascribed to the local imbalance electronic environment, in which single-atom Cu sites serve as H2 evolution center, and the carboxyl defect sites provide separate derivative site for various free radicals. The unique CO2 plasma method developed here can be completed in minutes with merits of environmental-friendless and waste-free, thus provides a promising route not only for the precise complex multiple modification of photocatalysts, but also for the sustainable industrial use of carbon dioxide.

Systematic Field Electron Emission Investigations of Vapor‐Phase‐Grown Sb2Te3 Nanosheets

Micron‐sized Sb2Te3 nanosheets are grown on p‐type Si substrate by facile vapor‐phase route. Physicochemical properties of the Sb2Te3 nanosheets are revealed using X‐ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscopy (AFM), transmission electron microscope (TEM), Raman spectroscopy, and X‐ray photoelectron spectroscopy (XPS). Owing to their high aspect ratio, field emission (FE) characteristics of the Sb2Te3 nanosheets grown on Si substrate (termed as a “planar emitter”) are investigated. Furthermore, the FE behavior of a single Sb2Te3 nanosheet attached to a blunt tungsten needle is studied. The single nanosheet emitter exhibited superior emission behavior in contrast to the planar emitter. The Fowler–Nordheim (F–N) plot for the single nanosheet emitter exhibits linear nature, whereas for the planar emitter it shows deviation from linearity. An attempt has been made to reveal the FE properties of a single Sb2Te3 nanosheet in an “in‐plane” configuration, similar to the vacuum field emission transistor (VFET). In this case, a maximum emission current of 1 μA is observed at 290 V, which is comparable to other VFETs. The observed results clearly imply the potential of the single nanosheet emitters due to topological insulators, like Sb2Te3, for the development of new generation nanoscale vacuum electronic devices.

Mechanically Induced Highly Efficient Hydrogen Evolution from Water over Piezoelectric SnSe nanosheets.

Piezoelectric nanomaterials open new avenues in driving green catalysis processes (e.g., H2 evolution from water) through harvesting mechanical energy, but their catalytic efficiency is still limited. The predicted enormous piezoelectricity for 2D SnSe, together with its high charge mobility and excellent flexibility, renders it an ideal candidate for stimulating piezocatalysis redox reactions. In this work, few-layer piezoelectric SnSe nanosheets (NSs) are utilized for mechanically induced H2 evolution from water. The finite elemental method simulation demonstrates an unprecedent maximal piezoelectric potential of 44.1V for a single SnSe NS under a pressure of 100MPa. A record-breaking piezocurrent density of 0.3mA cm-2 is obtained for SnSe NSs-based electrode under ultrasonic excitation (100 W, 45kHz), which is about three orders of magnitude greater than that of reported piezocatalysts. Moreover, an exceptional H2 production rate of 948.4 µmol g-1 h-1 is achieved over the SnSe NSs without any cocatalyst, far exceeding most of the reported piezocatalysts and competitive with the current photocatalysis technology. The findings not only enrich the potential piezocatalysis materials, but also provide useful guidance toward high-efficiency mechanically driven chemical reactions such as H2 evolution from water.

Synthesis of upconverting nanosheets derived from Er-Yb and Tm-Yb Co-doped layered perovskites and their layer-by-layer assembled films

Here, we investigated the structure and upconversion (UC) properties of new-type of single oxide nanosheets, derived from the Er3+/Yb3+ and Tm3+/Yb3+ co-doped Ruddlesden-Popper type layered perovskites, and their layer-by-layer (LBL) self-assembled nanofilms. The single oxide nanosheets, obtained by exfoliation of the proton-exchanged K2La2Ti3O10, had the thickness in the range of 2–3 nm indicating good consistency with the theoretical thickness and lateral size from 500 nm up to 2 µm. Er3+/Yb3+, Tm3+/Yb3+ and Tm3+/Er3+co-doped nanosheets were used as building blocks of the multilayer films deposited by layer-by-layer procedure. The LBL films composed of 2.5 % Er3+ + 5 % Yb3+, 2.5 % Tm3+ + 20 % Yb3+, 2.5 % Tm3+ + 20 % Er3+ after 60 sequences have shown a white emission confirmed by the CIE chromaticity diagram. The possible UC energy transfer of LBL films fabricated after 30 sequences using the nanosheets derived from the 2.5 % Er3+ + 5 % Yb3+ co-doped layered perovskites was also suggested. The number of photons participating in the UC process was confirmed as two-photon for both green and red UC emissions due to the 4F9/2 →4I15/2 and 2H11/2, 4S3/2→ 4I15/2 transitions, respectively.

Quantum oscillations in a hexagonal boron nitride-supported single crystalline InSb nanosheet

A gated Hall-bar device is made from an epitaxially grown, free-standing InSb nanosheet on a hexagonal boron nitride (hBN) dielectric/graphite gate structure and the electron transport properties in the InSb nanosheet are studied by gate-transfer characteristic and magnetotransport measurements at low temperatures. The measurements show that the carriers in the InSb nanosheet are of electrons and the carrier density in the nanosheet can be highly efficiently tuned by the graphite gate. The mobility of the electrons in the InSb nanosheet is extracted from low-field magneotransport measurements and a value of the mobility exceeding ∼ 1.8 × 104 cm2⋅V−1⋅s−1 is found. High-field magentotransport measurements show well-defined Shubnikov–de Haas (SdH) oscillations in the longitudinal resistance of the InSb nanosheet. Temperature-dependent measurements of the SdH oscillations are carried out and key transport parameters, including the electron effective mass m* ∼ 0.028m 0 and the quantum lifetime τ ∼ 0.046 ps, in the InSb nanosheet are extracted. It is for the first time that such experimental measurements have been reported for a free-standing InSb nanosheet and the results obtained indicate that InSb nanosheet/hBN/graphite gate structures can be used to develop advanced quantum devices for novel physics studies and for quantum technology applications.

Electrochemical method integrating exfoliation and in-situ growth to synthesize MoS2 nanosheets/MnO2 heterojunction for performance-enhanced supercapacitor

Two-dimensional (2D) molybdenum disulfide (MoS2) nanomaterials have become one of the promising options for constructing excellent supercapacitors. However, the application of MoS2 materials is limited by low energy density, and the difficulty of large-scale and low-cost preparation seriously hinders its practical application in the field of energy storage. Here, the exfoliation of the MoS2 nanosheets and the loading of MnO2 nanoparticles on the MoS2 nanosheets are realized in one step by electrochemical method. A series of characterization methods have fully confirmed that the electrochemical method has successfully prepared the MoS2 nanosheet/MnO2 (MoS2 NS/MnO2) heterojunction. The experimental results show that the MoS2 NS/MnO2 heterojunction has better electrochemical performance than a single MoS2 nanosheet. It has a good capacitance even in a neutral solution, and its specific capacitance is 275 F g−1 at a current density of 2 A g−1. In addition, a supercapacitor device based on MoS2 NS/MnO2 heterojunction was constructed, which not only exhibited excellent capacitive performance, but also exhibited 10,000 charge-discharge cycle stability under 10 A g−1 conditions. This work provides an experimental basis for the preparation of 2D nanosheets and the large-scale preparation of functionalized 2D material heterojunctions by electrochemical methods.

Experimental investigation of the mobility in the ITIC single crystal based field-effect transistor

The A-π-A electron acceptors, e.g. ITIC and its derivatives have attracted tremendous attention for optoelectronic applications since they can catch up with or even surpass the high performances based on the fulleren-based devices. The charge transport in the A-π-A electron acceptor depends heavily on the molecular packing structure. Tremendous theoretical works have been performed to investigate the correlation between the intermolecular arrangement and the mobility of A-π-A electron acceptors. The studies have simulated the mobility comparison between ITIC crystal and thin film. Although some researchers have measured the mobility of the ITIC thin films using space charge limit current (SCLC) technique and field-effect transistor (FET) measurement, the direct mobility measurements of ITIC crystals remain scarce. In this work, the ITIC single crystal nanosheets were grown by the solvent-non-solvent interfacial precipitation method, providing an effective way to investigate the mobility difference between the ITIC amorphous films and the ITIC single crystals. The measurements unravel that the resulting ITIC cystal has an edge-to-face stacking structure and it is anisotropic. The corresponding OFETs have been fabricated to investigate their mobilities: the single crystal devices exhibit mobility up to 5.4 × 10−2 cm2V−1s−1 while the amorphous ITIC film has a mobility of 2.1 × 10−3 cm2V−1s−1. This experimental result is consistent with the previous theoretical prediction and demonstrates that the crystalline ITIC has a more effective charge transport path along the b crystallographic axis than the amorphous film. This work provides a method to investigate the intrinsic charge transport property of the ITIC crystal.

UV-activated WS2/SnO2 2D/0D heterostructures for fast and reversible NO2 gas sensing at room temperature

2D Transition metal dichalcogenide (TMDs) has been recognized as a potential candidate for constructing wearable and safe room temperature gas sensor. Especially, the heterostructures of TMDs/ metal oxide semiconductors (MOS) have been proved to be potential candidates as NO2 sensors at room temperature. However, the response/recovery rate and reversibility of the sensors is still not satisfactory due to the inefficient charge transfer on TMDs/MOS hetero-interface. In this study, SnO2 quantum dots (QDs) were simply decorated on the surface of few or single layer WS2 nanosheets to form 2D/0D heterostructures via a facile room temperature aqueous solution process and self-assembly method. The 2D/0D WS2/SnO2 heterostructure-based optoelectronic gas sensor showed fast response/recovery rates and full reversibility to NO2 at room temperature with enhanced response. The remarkable improvement in NO2 sensing was because of the efficient interfacial charge separation rendered by 2D/0D heterostructures under ultraviolet illumination. Therefore, this study points out a potential strategy for the design of light-enhanced gas sensing materials.

Tunable multiplexed fluorescence biosensing platform for simultaneous and selective detection of paraquat and carbendazim pesticides

The monitoring of multiple pesticides commonly used in food is a prerequisite for public health safety. Herein, a multiplexed biosensor based on fluorescence resonance energy transfer (FRET) from multicolor upconversion nanoparticles (UCNPs)to single black phosphorus nanosheets (BPNSs) was successfully developed for simultaneous and selective detection of paraquat and carbendazim pesticides. Due to the strong π-π stacking interactions, aptamers functionalized UCNPs may adsorb on the BPNSs surface, allowing strong upconversion fluorescence quenching. In the presence of paraquat and carbendazim, the aptamers preferentially integrated with their corresponding targets and altered the aptamer’s conformation, restoring the fluorescence. An excellent linear correlation was observed from 1.0 to 1.0 × 105 ng/mL, with a limit of detection of 0.18 ng/mL for paraquat and 0.45 ng/mL for carbendazim. The developed aptasensor was further validated by commercial enzyme-linked immunoassays without significant differences in practical detection. Additionally, this work offers new insights into monitoring multiple targets simultaneously.

Regulating the Spin State of Single Noble Metal Atoms by Hydroxyl for Selective Dehydrogenation of CH4 Direct Conversion to CH3OH.

The key scientific challenge for methane (CH4) direct conversion to methanol (CH3OH) is considered to be the prevention of overoxidation of target products, which is restrained by the difficulty in the well-controlled process of selective dehydrogenation. Herein, we take single noble metal atom-anchored hexagonal boron nitride nanosheets with B vacancies (MSA/B1-xN) as the model materials and first propose that the dehydrogenation in the direct conversion of CH4 to CH3OH is highly dependent on the spin state of the noble metal. The results reveal that the noble metal with a higher spin magnetic moment is beneficial to the formation of the spin channels for electron transfer, which boosts the dissociation of C-H bonds. The promoted process of dehydrogenation will lead not only to the effective activation of CH4 but also to the easy overoxidation of CH3OH. More importantly, it is found that the spin state of noble metals can be regulated by the introduction of hydroxyl (OH), which realizes the selective dehydrogenation in the process of CH4 direct conversion to CH3OH. Among them, AgSA/B1-xN exhibits the best performance owing to the dynamic regulation spin state of a single Ag atom by OH. On the one hand, the introduction of OH significantly reduces the energy barrier of C-H bond dissociation by the increase in the spin magnetic moment. On the other hand, the high spin magnetic moment of a single Ag atom during the process of subsequent dehydrogenation can be modulated to nearly zero. As a result, the spin channel for electron transfer between the adsorbed CH3OH and reactive sites is broken, which hinders its overoxidation. This work opens a new path to designing catalysts for selective dehydrogenation by tuning the spin state of local electronic structures.

A Multilayer Interlaced Ag Nanosheet Film Prepared by an Electrodeposition Method on a PPy@PEDOT:PSS Film: A Strategy to Prepare Sensitive Surface-Enhanced Raman Scattering Substrates.

A highly sensitive multilayer interlaced silver (Ag) nanosheet (MISN) film was prepared on a PPy@PEDOT:PSS film via an electrodeposition method for surface-enhanced Raman scattering (SERS) applications. After the PPy@PEDOT:PSS film was pretreated with ascorbic acid solution, many sparse Ag nanoparticles (NPs) could be directly reduced on the surface of the PPy@PEDOT:PSS film in AgNO3 solution. Then, the MISN film was directionally grown along the surface of sparse Ag NPs by using an electrochemical galvanostatic method to form a Ag/PPy@PEDOT:PSS film for a SERS substrate. The results indicated that with the increase in electrodeposition time, the density of Ag nanosheets was also increased for boosting the SERS effect. Accordingly, owing to the directional growth of Ag NPs, the increase in the length–width ratio of single Ag nanosheets would further promote the SERS signal of the substrate. Moreover, the maximum enhancement factor of the SERS substrate could reach to 12,478, and the minimum limit of detection of melamine solution was down to 5.42 ng/mL. The SERS sensitivity of the Ag nanosheet film reached 100.65. This method of preparing the SERS substrate provides a novel and robust strategy for the low-cost and high-sensitivity detection in biomedicine, drugs, and food.