SnO2 Nanoflowers Research Articles

Synthesis of Ag-doped SnO2 nanoflowers and applications to room temperature high-performance NO2 gas sensing

SnO2 has attracted much attention in the field of gas sensors due to its unique structure and properties. In this work, SnO2 nanoflowers doped by Ag structures were prepared by a facile hydrothermal synthesis method. Ag doping not only increases the number of oxygen vacancies in the composite, but also alters the carrier migration behavior and significantly increases the carrier concentration, promoting the electron transport rate. Additionally, Ag doping enhanced the conductivity and catalytic activity of the composite, making it highly selective for NO2. At room temperature (RT), Ag-doped SnO2 sensor exhibit excellent gas-sensitizing properties. At the NO2 concentration of 100 ppm at RT (25 °C, 25 % RH) the prepared 2 at% Ag-SnO2 sensor has a response value of 73.0 (Ra/Rg), a response time of 1.4 s, and a detection limit as low as 10 ppb. Its long-term stability is up to 90 days. Doping is an effective way to improve gas sensing performance. It solves the disadvantages of low sensitivity and poor selectivity of SnO2.

Theoretical Validation of Non-Noble Cu Sites Integrated on SnO2 Nanoflowers for Enhanced Gas Sensing of Ethanethiol at Room Temperature.

Ethanethiol (EtSH), being highly toxic, flammable, and explosive, poses significant risks to human health and safety and is capable of causing fires and explosions. Room-temperature detection using chemiresistive gas sensors is essential for managing these risks. However, the gas-sensing performance of conventional metal-oxide sensing materials may be limited by their weak interaction with EtSH at room temperature. Herein, SnO2 nanoflowers assembled with non-noble Cu-site-enriched porous nanosheets were designed and prepared by an in situ self-template pyrolysis synthesis strategy to enable highly sensitive and selective room-temperature detection of EtSH. By regulating the number of non-noble Cu sites, these nanoflowers achieved efficient EtSH sensing with a Ra/Rg value of 11.0 at 50 ppb, ensuring high selectivity, reproducibility, and stability at room temperature. Moreover, a comparative analysis of the room-temperature gas-sensing performance of SnO2 nanoflowers with non-noble Fe- or Ni-site-enriched nanosheets highlights the benefits of non-noble Cu sites for EtSH detection. Density functional theory (DFT) analysis reveals that non-noble Cu sites have a unique affinity for EtSH, offering preferential binding over other gases and explaining the outstanding sensing performance of non-noble Cu-site-enriched nanosheet-assembled SnO2 nanoflowers. The structural and interface engineering of the sensing materials presented in this work provides a promising approach for offering efficient and durable gas sensors operable at room temperature.

Efficient electrochemical degradation of ceftazidime by Ti3+ self-doping TiO2 nanotube-based Sb–SnO2 nanoflowers as an intermediate layer on a modified PbO2 electrode

Ceftazidime (CAZ) is an emerging organic pollutant with a long-lasting presence in the environment. Although some PbO2 materials exhibit degradation capabilities, inefficient electron transport in the substrate layer and the problem of electrode stability still limit their use. Here, an interfacial design in which TiO2 nanotube arrays generate Ti3+ self-doping oxide substrate layers and highly active 3D Sb–SnO2 nanoflowers-like interlayers was used to prepare PbO2 anodes for efficient degradation of CAZ. Interestingly, after implementing Ti3+ self-doping in the PbO2 anode base layer and introducing 3D nanoflowers-like structures, the capacity for •OH generation increased significantly. The modified electrode exhibited 5-fold greater •OH generation capacity compared to the unmodified electrode, and a 2.7-fold longer accelerated electrode lifetime. The results indicate that interfacial engineering of the base and intermediate layers of the electrodes can improve the electron transfer efficiency, promote the formation of •OH, and extend the anode lifetime of the activated CAZ system.

Synergistically Modulating Conductive Filaments in Ion-Based Memristors for Enhanced Analog In-Memory Computing.

Memristors offer a promising solution to address the performance and energy challenges faced by conventional von Neumann computer systems. Yet, stochastic ion migration in conductive filament often leads to an undesired performance tradeoff between memory window, retention, and endurance. Herein, a robust memristor based on oxygen-rich SnO2 nanoflowers switching medium, enabled by seed-mediated wet chemistry, to overcome the ion migration issue for enhanced analog in-memory computing is reported. Notably, the interplay between the oxygen vacancy (Vo) and Ag ions (Ag+) in the Ag/SnO2/p++-Si memristor can efficiently modulate the formation and abruption of conductive filaments, thereby resulting in a high on/off ratio (>106), long memory retention (10-year extrapolation), and low switching variability (SV = 6.85%). Multiple synaptic functions, such as paired-pulse facilitation, long-term potentiation/depression, and spike-time dependent plasticity, are demonstrated. Finally, facilitated by the symmetric analog weight updating and multiple conductance states, a high image recognition accuracy of ≥ 91.39% is achieved, substantiating its feasibility for analog in-memory computing. This study highlights the significance of synergistically modulating conductive filaments in optimizing performance trade-offs, balancing memory window, retention, and endurance, which demonstrates techniques for regulating ion migration, rendering them a promising approach for enabling cutting-edge neuromorphic applications.

Improved ppb level SnO2@In2O3 sensor induced by In2O3 nanoparticles embedded on SnO2 nanoflower for superior NO2 sensing performance

The current study, accurately designed and created a two-dimensional (2D) structure of SnO2 nano-flowers and In2O3 nanoparticles using a simple hydrothermal technique and sol-gel method, respectively. On the outer surface of SnO2 nanoflowers the In2O3 nanoparticles were uniformly growing, clearly revealed by field emission scanning electron microscopic. Besides, crystal phase structure, surface area and elementals composition were characterized by XRD, BET, TEM, EDS, XPS and the gas sensing properties of In2O3@SnO2 NFs. The results exhibited that 2 wt% In2O3@SnO2 NFs sensor is highly sensitive to NO2, the response (Rg/Ra) to 30 ppm NO2 is 94.5, and at 50 ppb the response measured 0.61 at 150 °C, the response time is 32 and 51s, respectively, along with good moisture resistance. Besides along with excellent selectivity, long-term stability, and relative humidity (RH) in high-humidity environment, the 2 wt% In2O3@SnO2 NFs still maintain high response 91 at 30 ppm. More importantly, at room temperature the response was (Rg/Ra = 1.01) at detection limit 300 ppb towards NO2, which could use be for trace NO2 gas detection. The large specific surface areas of SnO2, the abundance of oxygen species adsorbed on the surface, the distinctive electron transformation between heterojunction materials, and high electron transmission channel of SnO2 and In2O3 transition layer were all considered to have a synergistic effect thatin2 contributed to excellent sensing properties of In2O3@SnO2 NFs.

CaIn2S4 nanosheets and SnO2 nanoflowers co-sensitized TiO2 nanotubes photoanode for continuous and efficient photocathodic protection of Q235 carbon steel

To solve the problem of poor photocathodic protection (PCP) effect of pure TiO2 nanotubes (NTs) on Q235 carbon steel (CS), CaIn2S4 nanosheets (NSs) and SnO2 nanoflowers (NFs) co-sensitized TiO2 NTs were prepared by anodization, hydrothermal and solvothermal method. Results showed that the absorption edge of CaIn2S4/SnO2/TiO2 NTs extended to 540 nm, indicating the utilization efficiency of visible light was greatly improved. Under light, the CaIn2S4/SnO2/TiO2 NTs exhibited an open circuit potential drop of 530 mV vs. SCE and a photocurrent density of 624 μA cm−2, which was 23 and 48 times that of TiO2 NTs, respectively. The PCP properties of CaIn2S4/SnO2/TiO2 NTs were better than that of TiO2 NTs because the separation and transfer efficiency of electrons and holes were promoted due to the heterojunction structure formed between TiO2, SnO2 and CaIn2S4. Furthermore, the CaIn2S4/SnO2/TiO2 NTs could also provide time-delay protection up to 10 h in the dark state. Obviously, CaIn2S4/SnO2/TiO2 NTs have excellent electron storage capacity and could provide efficient and continuous protection, which may be due to the presence of SnO2 NFs. This work provides an effective strategy of designing more efficient photoanodes for PCP of metals.

Ultrasensitive ethanol sensor based on Ce-modified SnO2 nanoflowers at low temperature

The improvement of ethanol gas-sensitive properties of SnO2 gas sensors is significant for the practical applications. The structures of pure SnO2 and Ce-modified SnO2 nanoflowers with different Ce contents (1 at%, 3 at% and 5 at%) were successfully prepared by a facile and environment friendly hydrothermal method with catalysis by CTAB and calcination in the air. The crystalline phase, morphology and chemical composition of the obtained SnO2 nanomaterials were analyzed, indicating that all four materials are flower-like structures assembled by nanosheets. The gas sensing behaviors of the fabricated sensors were systematically investigated. The results showed that Ce doping can significantly improve the sensing performance of the SnO2 gas sensors. The sensor based on 5 at% Ce-SnO2 nanoflowers exhibited not only high response (55), quick response/recovery time (7 s/9 s), excellent selectivity, but also long-time stability for 200 ppm ethanol at a lower operating temperature (125 °C). Furthermore, the gas sensing mechanism was also discussed in detail.

Highly Sensitive Isopropanol Gas Sensor based on SnO2 Nano-Flowers on Gold, Silver, and Aluminum Interdigitated Electrodes

In this research we have proposed a high selectivity Isopropanol gas sensor. The sensor shows significant resistance change only to Isopropanol gas. The synthesis method of flower-like SnO2 nanostructures, the electrode material and design, and the optimized working temperature provide the high selectivity and high response of the sensor. The SnO2 nanoflowers (NFs) have been synthesized in a two-step process as the gas sensitive layer. The sensor shows its best performance on Au interdigitated electrodes. The optimized working temperature is obtained at 150 °C. The proposed sensor has a high sensitivity, good repeatability, long-term stability and remarkable selectivity. The responses of the sensor to 100 ppm of isopropanol at 150 °C is 71 and the sensor is capable of keeping almost 96% of the initial response in a 40 d period.

Enhanced anode electrochemiluminescence in split aptamer sensor for kanamycin trace monitoring

Covalently modifying electrochemiluminescence (ECL) luminophores to alter their energy levels or generate energy/electron transfer processes for improved performance is hindered by the complex design and fabrication processes. In this study, non-covalent bond self-assembly was employed to enhance the ECL property of gold nanoclusters with tryptophan (Try) and mercaptopropionic acid (MPA) as ligands (Try-MPA-gold nanoclusters). Specifically, through the molecular recognition of Try by cucurbit[7]uril, some non-radiative transition channels of the charge carriers on the surface of the Try-MPA-gold nanoclusters were restricted, resulting in a significant enhancement of the ECL intensity of the nanoclusters. Furthermore, rigid macrocyclic molecules acted on the surface of the nanoclusters through self-assembly, forming a passive barrier that improved the physical stability of the nanoclusters in the water-phase and indirectly improved their luminescent stability. As an application, cucurbit[7]uril-treated Try-MPA-gold nanoclusters (cucurbit[7]uril@Try-MPA-gold nanoclusters) were used as signal probes, and Zn-doped SnO2 nanoflowers (Zn-SnO2 NFs) with high electron mobility were used as electrode modification material to establish an ECL sensor for kanamycin (KANA) detection, utilizing split aptamers as capture probes. The advanced split aptamer sensor demonstrated excellent sensitivity analysis for KANA in complex food substrates with a recovery rate of 96.2 to 106.0%.

Self-assembled 3D hierarchical S-doped SnO2 nanoflowers based room temperature ammonia sensor

Self-assembled 3D hierarchical S-doped SnO2 nanoflowers based room temperature ammonia sensor

Facile Hydrothermal Synthesis of SnO2 Nanoflowers for Low-Concentration Formaldehyde Detection.

In this work, SnO2 nanoflowers were prepared by a simple one-step hydrothermal process. The morphology and structure of SnO2 nanoflowers were characterized by SEM, TEM, Raman spectroscopy, and XRD, which demonstrated the good crystallinity of the SnO2 tetrahedron structure of the as-synthesized materials. In addition, the sensing properties of SnO2 nanoflowers were studied in detail. It was found that the SnO2 nanoflower-based gas sensor exhibits excellent gas response (9.2 to 120 ppm), fast response and recovery (2/15 s to 6 ppm), good linearity of correlation between response (S) vs. concentration (C) (lgS = 0.505 lgC − 0.147, R2 = 0.9863), superb repeatability, and selectivity at 300 °C. The outstanding performance can also be attributed to the high specific surface area ratio and size of SnO2 nanoflowers close to the thickness of the electron depletion layer that can provide abundant active sites, promote the rate of interaction, and make it easier for gas molecules to diffuse into the interior of the material. Therefore, SnO2 nanoflowers can be an ideal sensing material for real-time monitoring of low-concentration HCHO.

Enhanced n-butanol sensing performance of SnO2/ZnO nanoflowers fabricated via a facile solvothermal method

High-performance gas sensors have important application prospects in the detection and monitoring of toxic and harmful gases that exist in the environment and workshop. Herein, SnO2/ZnO nanoflowers with core-shell like structure were successfully fabricated by a two-step solvothermal method. Morphology and mineral phase characterizations demonstrate that the nanoflowers, composed of a SnO2 flower core in a diameter of about 50 nm and ZnO nanoparticles embedded in the interstice of SnO2 petals, has a novel mesoporous hierarchical structure with pore size distributed in about 3 nm and 30 nm and a specific surface area of 36.474 m2/g, benefitting to gas-sensing. The results reveal that, compared to pure SnO2 nanoflowers, the optimal SnO2/ZnO (Zn/Sn is 5%) based gas sensor shows 2.7-fold sensing enhancement, fast response (3 s), long-term stability toward n-butanol. It has an outstanding selectivity to n-butanol rather than other gas, its response toward 100 ppm n-butanol at 200 °C is up to 13, 34, 15 and 32 times of that to acetone, xylene, ammonia and carbon monoxide respectively. Hence, SnO2/ZnO nanoflowers can be considered as a practical sensing material for n-butanol detection.

Hierarchical SnO2 nanoflower sensitized by BNQDs enhances the gas sensing performances to BTEX

In this study, the SnO2 nanoflowers with hierarchical structures sensitized by boron nitride quantum dots (BNQDs) were prepared through a simple hydrothermal method. It was applied for the detection of the BTEX vapors. Further investigation showed that the response value of SnO2 sensitized by different amounts of BNQDs to the BTEX gases have a certain improvement. Especially 10-BNQDs/SnO2 gas sensor exhibited a significant improvement in gas sensing performance and its response values to different BTEX gases was increased up to 2–4 folds compared with the intrinsic SnO2 sensor. In addition, SnO2 nanoflowers based gas sensor showed surprisingly fast response and recovery time for BTEX gases with 1–2 s. That can be attributed to the sensitization of BNQDs and the hierarchical structure of SnO2 nanoflowers, which provided an easy channel for the gas diffusion. An economically viable gas sensor based on BNQDs sensitized SnO2 nanoflowers exhibited a great potential in BTEX gas detection due to the simple synthesis method, environmentally friendly raw materials and excellent gas sensing performance.

Preparation of a novel Ce and Sb co-doped SnO2 nanoflowers electrode by a two-step (hydrothermal and thermal decomposition) method for organic pollutants electrochemical degradation

Nanostructured Sb-SnO2 electrodes with high electrochemical activity and stability are urgently desired for electrochemical oxidation of refractory organics in wastewater treatment, yet hard to be controlled and synthesized. Hence, we combined the hydrothermal method and thermal decomposition technologies to prepare a novel Ce and Sb co-doped SnO2 nanoflowers electrode (Ti/Ce-Sb-SnO2NFs). The incorporation of Ce endowed the Ti/Ce-Sb-SnO2NFs anode with an increased oxygen evolution over-potential (OEP) (1.99 V vs.SCE), lower charge transfer resistance (7.54 Ω⋅cm2), large specific electrochemical active surface area (141.83), a great number of active sites and superior •OH generation ability. Consequently, nearly 100% decolorization efficiency and 91.45% chemical oxygen demand (COD) mineralization efficiency of methylene blue (MB) (20 mg/L) were achieved by the Ti/Ce-Sb-SnO2NFs anode within 90 min. Additionally, the Ti/Ce-Sb-SnO2NFs anode stability was also improved with a longer accelerated lifetime (15.5 h) than the given Ti/Sb-SnO2NFs electrode (8.2 h). We also prepared other nanostructured (nanoparticles, nanoclusters and nanosheets) Sb-SnO2 electrodes with high oxidation capacity utilizing this two-step method, which demonstrated its great versatility. Accordingly, this work could provide a new strategy for fabricating efficient and stable rare earth elements (Ce, Nd, La, etc.) and Sb co-doped SnO2 nanostructured electrodes for decomposition organic pollutants in the field of wastewater treatment.

Super-Hydrophobic F-Doped SnO2 (FTO) Nanoflowers Deposited by Spray Pyrolysis Process for Solar Cell Applications

Super-Hydrophobic F-Doped SnO2 (FTO) Nanoflowers Deposited by Spray Pyrolysis Process for Solar Cell Applications

Enhanced Methane Sensing Properties of SnO2 Nanoflowers With Ag Doping: A Combined Experimental and First-Principle Study

Ag-doped SnO2 nanoflowers (NFs) are prepared via a simple one-step hydrothermal method and subsequent Ag-doping using AgNO3 solution as precursors. The crystal structure, morphology and elements of the Ag-doped SnO2 NFs are investigated in detail. The maximal response of Ag-doped SnO2 sensor with 1.0 wt.% Ag doping to 500 ppm methane is increased by a factor of 1.6 as compared to that of pure SnO2 sensor. The long-term stability and the selectivity of the SnO2-based sensor are improved by Ag-doping as well. Meanwhile, pre-adsorption of oxygen molecules on the surface of the SnO2-based substrate is studied in-depth with the method of first-principle calculation. Ag doping lowers adsorption energy for all the adsorption sites, demonstrating a higher adsorption stability of chemisorbed oxygen ions on the Ag-doped SnO2 as compared to the pristine phase. More electron transfer from the semiconductor to the chemisorbed oxygen is revealed by the Mulliken charge analysis and the electron density difference for the Ag-doped SnO2, explaining the better sensitivity of gas sensors based on Ag-doped SnO2 nanostructures as compared to its undoped counterpart.

Controllable acid vapor oxidation growth of complex SnO2 nanostructures for ultrasensitive ethanol sensing

Controllable assembly from one-dimensional (1-D) and two-dimensional (2-D) nanoscale structures to three-dimensional (3-D) complex nanostructures has attracted great interest. For the first time, nanorods and nanosheets were controllably assembled into 3-D SnO2 nanoflower architectures based on a facile and shape-controlled acid vapor oxidation (AVO) method from the substrate in a simple reaction system. The as-prepared 3-D SnO2 nanoflowers have diameters ranging from 625 to 875 nm and are self-assembled by many nanorods and nanosheets with diameters and thicknesses of 33 nm. The growth of SnO2 with different morphologies was studied by controlling the reaction temperature and hydrochloric acid concentration. Their application in gas sensing was evaluated, indicating that the 3-D SnO2 nanoflower-based sensor is ultrasensitive to ethanol with a response of 2.54–50 ppb at the optimal working temperature of 230 °C. This work offers a facile, shape-controlled, and efficient route to synthesize complex SnO2 nanoflowers for gas detection with high performance, including ultrahigh sensitivity, good selectivity, and reversibility.

Fabrication of a Ti/PbO2 electrode with Sb doped SnO2 nanoflowers as the middle layer for the degradation of methylene blue, norfloxacin and p-dihydroxybenzene

In the preparation of Sb-SnO2 internal layer of PbO2 electrode, the traditional thermal decomposition method has many problems, such as environmental pollution, short service life and low catalytic activity. Herein, a three-dimensional (3D) Sb doped SnO2 nanoflowers interlayer with good conductivity was prepared on the titanium substrate by the hydrothermal strategy to fabricate a novel PbO2 electrode (Ti/Sb-SnO2NFs/PbO2). Compared to the traditional PbO2 anode, a more compact and undulating 3D morphology of Ti/Sb-SnO2NFs/PbO2 electrode exhibited a higher total and inner active sites and stronger ·OH generation ability. Specifically, three typical organics, methylene blue (MB), norfloxacin (NOR) and p-dihydroxybenzene (p-DHB), were effectively degraded by the novel Ti/Sb-SnO2NFs/PbO2 electrode with economic energy consumption and the degradation mechanism of MB was also investigated. This 3D interlayer also improved the anode stability and safety with the lifetime prolonged about 2.70 times (from 30.1 h to 81.3 h). Consequently, this work offers a meaningful method to prepare PbO2 anode with high catalytic activity and good stability for wastewater treatment.

Versatile photoelectrochemical and electrochemiluminescence biosensor based on 3D CdSe QDs-DNA nanonetwork-SnO2 nanoflower coupled with DNA walker amplification for HIV detection

A novel 3D CdSe quantum dots (QDs)-DNA nanonetwork was assembled to sensitize the mesoporous SnO2 photoelectrochemical (PEC) substrate, which was coupled with a biped-DNA walker multiple amplification technique to design a versatile electrochemiluminescence (ECL) and PEC biosensor for dual detection of HIV. Firstly, the photosensitive CdSe QDs and SnO2 nanoflowers have well-matched band-edge energy level, thus their complex can promote effective transfer of the photogenerated carriers, and show better PEC and ECL property. Then, a novel 3D CdSe QDs-DNA nanonetwork was assembled and loaded with a large amount of QDs, which was used as multifunctional PEC and ECL probes. Moreover, the target-triggered biped DNA walker-cascade amplification method was introduced to generate a large amount of output DNA, which was used to link numerous 3D CdSe QDs-DNA nanonetwork probes to the electrode, generating greatly amplified signals for sensitive assay of HIV. The highly photosensitive 3D CdSe QDs-DNA reticulated nanomaterials have high stability and controllability, and display significantly improved PEC and ECL signals of the biosensor. This method opened a new photoelectric nanocomposite of QDs-sensitized SnO2 nanoflower, and developed a versatile biosensing strategy using the 3D CdSe QDS DNA sensitization probes for ultra-sensitive detection of biomolecules, which is important for the early diagnosis of diseases.

Hierarchical nanostructured Au–SnO2 for enhanced energy storage performance

Electrode materials with high energy and power density are mostly essential to overcome traditional fossil fuel use. Herein, we demonstrate the synthesis of Au decorated self-assembled SnO2 nanoflowers consisting of nanorods by a cost-effective and eco-friendly solvothermal process. The as-synthesized SnO2 based materials were employed as electrode material in the energy storage system, which delivered considerably high specific capacitance of 634.3 F/g at a current density of 1 A/g. The electrode material also exhibits excellent cycle stability of 83.52% after 4000 galvanostatic charge–discharge (GCD) cycles. The high specific capacitive value is attributed to the hybrid performance of battery and supercapacitor, more active sites, and higher surface area. A solid state asymmetry device was fabricated using Au–SnO2 and activated carbon (AC) as positive and negative electrodes. The asymmetry device shows an excellent energy density of 168.9 Wh/kg at a power density of 1 kW/kg with an applied current density of 1 A/g.