Efficient Charge Separation in Ag/PCN/UPDI Ternary Heterojunction for Optimized Photothermal-Photocatalytic Performance via Tandem Electric Fields.

Charge separation driven by the internal electric field is a research hotspot in photocatalysis. However, it remains challenging to accurately control the electric field to continuously accelerate the charge transfer. Herein, a strategy of constructing a tandem electric field to continuously accelerate charge transfer in photocatalysts is proposed. The plasma electric field, interface electric field, and intramolecular electric field are integrated into the Ag/g-C3N4/urea perylene imide (Ag/PCN/UPDI) ternary heterojunction to achieve faster charge separation and longer carrier lifetime. The triple electric fields function as three accelerators on the charge transport path, promoting the separation of electron-hole pairs, accelerating charge transfer, enhancing light absorption, and increasing the concentration of energetic electrons on the catalyst. The H2 evolution rate of Ag/PCN/UPDI is 16.8 times higher than that of pristine PDI, while the degradation rate of oxytetracycline is increased by 4.5 times. This new strategy will provide a groundbreaking idea for the development of high-efficiency photocatalysts.

Advances in Carbon Dot-Based Ratiometric Fluorescent Probes for Environmental Contaminant Detection: A Review.

Detecting environmental contaminants is crucial for protecting ecosystems and human health. While traditional carbon dot (CD) fluorescent probes are versatile, they may suffer from limitations like fluctuations in signal intensity, leading to detection inaccuracies. In contrast, ratiometric fluorescent probes, designed with internal self-calibration mechanisms, offer enhanced sensitivity and reliability. This review focuses on the design and applications of ratiometric fluorescent probes based on CDs for environmental monitoring. Our discussion covers construction strategies, ratiometric fluorescence principles, and applications in detecting various environmental contaminants, including organic pollutants, heavy metal ions, and other substances. We also explore associated advantages and challenges and provide insights into potential solutions and future research directions.

Upconversion-Powered Photoelectrochemical Bioanalysis for DNA Sensing.

In this work, we report a new concept of upconversion-powered photoelectrochemical (PEC) bioanalysis. The proof-of-concept involves a PEC bionanosystem comprising a NaYF4:Yb,Tm@NaYF4 upconversion nanoparticles (UCNPs) reporter, which is confined by DNA hybridization on a CdS quantum dots (QDs)/indium tin oxide (ITO) photoelectrode. The CdS QD-modified ITO electrode was powered by upconversion absorption together with energy transfer effect through UCNPs for a stable photocurrent generation. By measuring the photocurrent change, the target DNA could be detected in a specific and sensitive way with a wide linear range from 10 pM to 1 µM and a low detection limit of 0.1 pM. This work exploited the use of UCNPs as signal reporters and realized upconversion-powered PEC bioanalysis. Given the diversity of UCNPs, we believe it will offer a new perspective for the development of advanced upconversion-powered PEC bioanalysis.

Guiding the Driving Factors on Plasma Super-Photothermal S-Scheme Core-Shell Nanoreactor to Enhance Photothermal Catalytic H2 Evolution and Selective CO2 Reduction.

Light-induced heat has a non-negligible role in photocatalytic reactions. However, it is still challenging to design highly efficient catalysts that can make use of light and thermal energy synergistically. Herein, the study proposes a plasma super-photothermal S-scheme heterojunction core-shell nanoreactor based on manipulation of the driving factors, which consists of α-Fe2 O3 encapsulated by g-C3 N4 modified with gold quantum dots. α-Fe2 O3 can promote carrier spatial separation while also acting as a thermal core to radiate heat to the shell, while Au quantum dots transfer energetic electrons and heat to g-C3 N4 via surface plasmon resonance. Consequently, the catalytic activity of Au/α-Fe2 O3 @g-C3 N4 is significantly improved by internal and external double hot spots, and it shows an H2 evolution rate of 5762.35 µmol h-1 g-1 , and the selectivity of CO2 conversion to CH4 is 91.2%. This work provides an effective strategy to design new plasma photothermal catalysts for the solar-to-fuel transition.

A novel role for microtubule affinity-regulating kinases in neuropathic pain.

BACKGROUND AND PURPOSE: Neuropathic pain affects millions of patients, but there are currently few viable therapeutic options available. Microtubule affinity-regulating kinases (MARKs) regulate the dynamics of microtubules and participate in synaptic remodelling. It is unclear whether these changes are involved in the central sensitization of neuropathic pain. This study examined the role of MARK1 or MARK2 in regulating neurosynaptic plasticity induced by neuropathic pain. EXPERIMENTAL APPROACH: A rat spinal nerve ligation (SNL) model was established to induce neuropathic pain. The role of MARKs in nociceptive regulation was assessed by genetically knocking down MARK1 or MARK2 in amygdala and systemic administration of PCC0105003, a novel small molecule MARK inhibitor. Cognitive function, anxiety-like behaviours and motor coordination capability were also examined in SNL rats. Synaptic remodelling-associated signalling changes were detected with electrophysiological recording, Golgi-Cox staining, western blotting and qRT-PCR. KEY RESULTS: MARK1 and MARK2 expression levels in amygdala and spinal dorsal horn were elevated in SNL rats. MARK1 or MARK2 knockdown in amygdala and PCC0105003 treatment partially attenuated pain-like behaviours along with improving cognitive deficit, anxiogenic-like behaviours and motor coordination in SNL rats. Inhibition of MARKs signalling reversed synaptic plasticity at the functional and structural levels by suppressing NR2B/GluR1 and EB3/Drebrin signalling pathways both in amygdala and spinal dorsal horn. CONCLUSION AND IMPLICATIONS: These results suggest that MARKs-mediated synaptic remodelling plays a key role in the pathogenesis of neuropathic pain and that pharmacological inhibitors of MARKs such as PCC0105003 could represent a novel therapeutic strategy for the management of neuropathic pain.

Edge sulfur vacancies riched MoS2 nanosheets assist PEDOT:PSS flexible film ammonia sensing enhancement for wireless greenhouse vegetables monitoring.

Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is a promising NH3 sensing material owing to its super high electrical conductivity, excellent environmental stability, and reversible doping/dedoping nature. However, the low sensitivity and sluggish recovery rate limit its further application in gas sensors. Herein, exfoliated layered MoS2 nanosheets with large-specific surface area and abundant edge sulfur (S) vacancies are utilized to assist PEDOT:PSS and achieve ideal improvement in NH3 sensing performance at room temperature (RT), including high response values, fast response/recovery ability, and excellent sensing stability in complex environment. MoS2 nanosheets are combined with PEDOT:PSS to construct p-n heterojunction, the S vacancies can improve carrier transfer rate and serve as conductive bridge, effective active sites for NH3 adsorption, this series of performance improvement strategies is the significance of this work. Meanwhile, the density-functional theory (DFT), current-voltage (I-V), and in-situ FITR are firstly employed to discuss the sensing mechanisms in detail. Furthermore, integrating MoS2/PEDOT:PSS flexible sensor into a designed printed circuit board to intelligent, visual, and wireless real-time monitoring the NH3 resistance information in a simulated greenhouse vegetables equipment through the smartphone APP has also been successfully implemented.

Organic Electrochemical Transistor with MoS2 Nanosheets Modified Gate Electrode for Sensitive Glucose Sensing.

An organic electrochemical transistor (OECT) with MoS2 nanosheets modified on the gate electrode was proposed for glucose sensing. MoS2 nanosheets, which had excellent electrocatalytic performance, a large specific surface area, and more active sites, were prepared by liquid phase ultrasonic exfoliation to modify the gate electrode of OECT, resulting in a large improvement in the sensitivity of the glucose sensor. The detection limit of the device modified with MoS2 nanosheets is down to 100 nM, which is 1~2 orders of magnitude better than that of the device without nanomaterial modification. This result manifests not only a sensitive and selective method for the detection of glucose based on OECT but also an extended application of MoS2 nanosheets for other biomolecule sensing with high sensitivity.

Plasma Ag-Modified α-Fe2O3/g-C3N4 Self-Assembled S-Scheme Heterojunctions with Enhanced Photothermal-Photocatalytic-Fenton Performances.

Low spectral utilization and charge carrier compounding limit the application of photocatalysis in energy conversion and environmental purification, and the rational construction of heterojunction is a promising strategy to break this bottleneck. Herein, we prepared surface-engineered plasma Ag-modified α-Fe2O3/g-C3N4 S-Scheme heterojunction photothermal catalysts by electrostatic self-assembly and light deposition strategy. The local surface plasmon resonance effect induced by Ag nanoparticles broadens the spectral response region and produces significant photothermal effects. The temperature of Ag/α-Fe2O3/g-C3N4 powder is increased to 173 °C with irradiation for 90 s, ~3.2 times higher than that of the original g-C3N4. The formation of 2D/2D structured S-Scheme heterojunction promotes rapid electron-hole transfer and spatial separation. Ternary heterojunction construction leads to significant enhancement of photocatalytic performance of Ag/α-Fe2O3/g-C3N4, the H2 photocatalytic generation rate up to 3125.62 µmol g-1 h-1, which is eight times higher than original g-C3N4, and the photocatalytic degradation rate of tetracycline to reach 93.6%. This thermally assisted photocatalysis strategy improves the spectral utilization of conventional photocatalytic processes and provides new ideas for the practical application of photocatalysis in energy conversion and environmental purification.

Multisignal optical temperature-sensing properties of Eu3+ -doped NaYF4 nanoparticles.

In this paper, the multisignal (different emissions/colours) temperature sensing of NaYF4 :Eu3+ nanoparticles is investigated, which is based on fluorescence intensity ratios (FIRs) between 5 D0 →7 FJ (J=1-4) and 5 D1 →7 FJ' emissions. The 5 D1 →7 FJ' (J'=0-2) emissions can be clearly observed due to the low photon energy of NaYF4 . Based on the FIRs between different 5 D0 →7 FJ and 5 D1 →7 FJ' emissions, higher absolute/relative temperature sensitivities are obtained. Compared with the FIR between whole 5 D0 →7 FJ and 5 D1 →7 FJ' emissions, the maximum value of Sa was improved from 0.27 K-1 to 5.02 K-1 and that of Sr was improved from 0.89%·K-1 to 1.27%·K-1 . Furthermore, the FIRs between different colours of emissions were investigated for the application of wide-range multicolour temperature sensing.

Si/TiO2/Ag Multistorey Structures with Interfacial Charge Transfer for a Recyclable Surface-Enhanced Raman Scattering Substrate.

In this work, highly ordered TiO2/Ag bilayer structures on p-type silicon (Si) wafers are prepared by photolithography and electrochemical self-assembly methods. The interfacial charge transfer (CT) of this Si/TiO2/Ag multistorey structure with a specially aligned work function is studied. This is important to deduce the interfacial electron migration behavior of SERS. The three-dimensional finite-difference time-domain (3D FDTD) simulation is used to explore the combined CT-EM enhancement mechanism. The result shows that the electron movement under the CT mechanism can induce the resonance effect of free electrons to further improve EM performance. In addition, the effect of agglomerated Ag nanoparticle size distribution on the SERS property and the self-cleaning property of Si/TiO2/Ag multistorey structures is investigated. Finally, this unique structure of highly ordered Si/TiO2/Ag SERS substrate shows superior sensitivity, reproducibility, and stability. Rhodamine 6G (R6G) with trace concentrations as low as 10-15 M can be detected, and the EF is estimated to be about 8.9 × 1013. The relative standard deviation (RSD) at 1511 cm-1 is about 4.7%. These results are very promising for the practical application of the SERS technique in the rapid trace determination in many fields.

Excellent fluorescence detection of Cu2+in water system using N-acetyl-L-cysteines modified CdS quantum dots as fluorescence probe.

View of the negative influence of metal ions on natural environment and human health, fast and quantitative detection of metals ions in water systems is significant. Ultra-small grain size CdS quantum dots (QDs) modified with N-acetyl-L-cysteines (NALC) (NALC-CdS QDs) are successfully prepared via a facile hydrothermal route. Based on the changes of fluorescence intensity of NALC-CdS QDs solution after adding metal ions, the fluorescence probe made from the NALC-CdS QDs is developed to detect metal ions in water systems. Among various metal ions, the fluorescence of NALC-CdS QDs effectively quenched by the addition of Cu2+, the probe shows high sensitivity and selectivity for detecting Cu2+in other interferential metal ions coexisted system. Importantly, the fluorescence intensity of NALC-CdS QDs changes upon the concentration of Cu2+, the probe displays an excellent linear relationship between the fluorescence quenching rate and the concentration of Cu2+in ranging from 1 to 25µM. Besides, the detected limitation of the probe towards Cu2+as low as 0.48µM. The measurement of Cu2+in real water sample is also carried out using the probe. The results indicate that NALC-CdS QDs fluorescence probe may be a promising candidate for quantitative Cu2+detection in practical application.

WITHDRAWN: PCC-0105002, a novel small molecule inhibitor of PSD95-nNOS protein-protein interactions, attenuates neuropathic pain and corrects motor coordination-associated side effects in neuropathic pain model.

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Chemico-Proteomics Reveal the Enhancement of Salt Tolerance in an Invasive Plant Species via H2S Signaling.

H2S is a small molecule known to have multiple signaling roles in animals. Recently, evidence shows that H2S also has signaling functions in plants; however, the role of H2S in invasive plants is unknown. Spartina alterniflora is a typical invasive species growing along the beaches of southern China. A physiological comparison proves that S. alterniflora is highly tolerant to salinity stress compared with the native species Cyperus malaccensis. To decipher the mechanism that enables S. alterniflora to withstand salinity stress, a chemico-proteomics analysis was performed to examine the salt stress response of the two species; an inhibitor experiment was additionally designed to investigate H2S signaling on salinity tolerance in S. alterniflora. A total of 86 proteins belonging to nine categories were identified and differentially expressed in S. alterniflora exposed to salt stress. Moreover, the expression level of enzymes responsible for the H2S biosynthesis was markedly upregulated, indicating the potential role of H2S signaling in the plant's response to salt stress. The results suggested that salt triggered l-CD enzyme activity and induced the production of H2S, therefore upregulating expression of the antioxidants ascorbate peroxidase, superoxide dismutase, and S-nitrosoglutathione reductase, which mitigates damage from reactive nitrogen species. Additionally, H2S reduced the potassium efflux, thereby sustaining intracellular sodium/potassium ion homeostasis and enhancing S. alterniflora salt tolerance. These findings indicate that H2S plays an important role in the adaptation of S. alterniflora to saline environments, which provides greater insight into the function of H2S signaling in the adaptation of an invasive plant species.

PCC0208009, an indirect IDO1 inhibitor, alleviates neuropathic pain and co-morbidities by regulating synaptic plasticity of ACC and amygdala.

BACKGROUND AND PURPOSE: Indoleamine 2, 3-dioxygenase 1 (IDO1) has been linked to neuropathic pain and IDO1 inhibitors have been shown to reduce pain in animals. Some studies have indicated that IDO1 expression increased after neuropathic pain in hippocampus and spinal cord, whether these changes existing in anterior cingulate cortex (ACC) and amygdala remains obscure and how IDO1 inhibition leads to analgesia is largely unknown. Here, we evaluated the antinociceptive effect of PCC0208009, an indirect IDO1 inhibitor, on neuropathic pain and examined the related neurobiological mechanisms. EXPERIMENTAL APPROACH: The effects of PCC0208009 on pain, cognition and anxiogenic behaviors were evaluated in a rat model of neuropathic pain. Motor disorder, sedation and somnolence were also assessed. Biochemical techniques were used to measure IDO1-mediated signaling changes in ACC and amygdala. KEY RESULTS: In rats receiving spinal nerve ligation (SNL), IDO1 expression level was increased in ACC and amygdala. PCC0208009 attenuated pain-related behaviors in the formalin test and SNL model and increased cognition and anxiogenic behaviors in SNL rats at doses that did not affect locomotor activity and sleeping. PCC0208009 inhibited IDO1 expression in ACC and amygdala by inhibiting the IL-6-JAK2/STAT3-IDO1-GCN2-IL-6 pathway. In addition, PCC0208009 reversed synaptic plasticity at the functional and structural levels by suppressing NMDA2B receptor and CDK5/MAP2 or CDK5/Tau pathway in ACC and amygdala. CONCLUSION AND IMPLICATIONS: These results support the role of IDO1-mediated molecular mechanisms in neuropathic pain and suggest that the IDO1 inhibitor PCC0208009 demonstrates selective pain suppression and could be a useful pharmacological therapy for neuropathic pain.

Acute and repeated dose 26-week oral toxicity study of 20(S)-ginsenoside Rg3 in Kunming mice and Sprague-Dawley rats.

BACKGROUND: 20(S)-ginsenoside-Rg3 (C42H72O13), a natural triterpenoid saponin, is extracted from red ginseng. The increasing use of 20(S)-ginsenoside Rg3 has raised product safety concerns. METHODS: In acute toxicity, 20(S)-ginsenoside Rg3 was singly and orally administrated to Kunming mice and Sprague-Dawley (SD) rats at the maximum doses of 1600 mg/kg and 800 mg/kg, respectively. In the 26-week toxicity study, we used repeated oral administration of 20(S)-ginsenoside Rg3 in SD rats over 26 weeks at doses of 0, 20, 60, or 180 mg/kg. Moreover, a 4-week recovery period was scheduled to observe the persistence, delayed occurrence, and reversibility of toxic effects. RESULTS: The result of acute toxicity shows that oral administration of 20(S)-ginsenoside Rg3 to mice and rats did not induce mortality or toxicity up to 1600 and 800 mg/kg, respectively. During a 26-week administration period and a 4-week withdrawal period (recovery period), there were no significant differences in clinical signs, body weight, food consumption, urinalysis parameters, biochemical and hematological values, or histopathological findings. CONCLUSION: The mean oral lethal dose (LD50) of 20(S)-ginsenoside Rg3, in acute toxicity, is above 1600 mg/kg and 800 mg/kg in mice and rats, respectively. In a repeated-dose 26-week oral toxicity study, the no-observed-adverse-effect level for female and male SD rats was 180 mg/kg.

Repeated-dose 26-week oral toxicity study of ginsenoside compound K in Beagle dogs.

ETHNOPHARMACOLOGICAL RELEVANCE: Ginsenoside compound K (CK), a product produced by the intestinal bacteria-mediated breakdown of ginsenoside, exhibits a wide array of pharmacological activities against diverse targets. However, few of preclinical safety evaluation of CK is reported. AIMS OF THE STUDY: The present study therefore sought to assess the toxicity of oral CK in Beagle dogs over a 26-week period. MATERIAL AND METHODS: All dogs received 4, 12, or 36 mg/kg oral CK doses for 26 weeks with regular monitoring, followed by a 4-week recovery period. Animals were monitored through measurements of temperature, weight, food intake, blood chemistry and hematological findings, electrocardiogram (ECG) measurements, urinalysis, gross necropsy and organ weight and tissue histopathology. RESULTS: Animals in the 36 mg/kg group exhibited an apparent reduction in body weight over the study period, in addition to the presence of focal liver necrosis and increased plasma enzyme levels (alanine aminotransferase, ALT; alkaline phosphatase, ALP) consistent with hepatotoxicity, although there was some evidence suggesting this toxicity was reversible. Animals in the 4 and 12 mg/kg groups did not exhibit any apparent toxicity for any measured parameters. CONCLUSION: These results thus indicate that the no observed adverse effect level (NOAEL) in dogs is 12 mg/kg.

L-Aspartic Acid Capped CdS Quantum Dots as a High Performance Fluorescence Assay for Sliver Ions (I) Detection.

A new high performance fluorescence assay for detection of Ag+ based on CdS quantum dots (QDs) using L-Aspartic acid (L-Asp) as a stabilizer was proposed in this work. The CdS quantum dots conjugation with L-Aspartic acid (L-Asp@CdS QDs) were successfully synthesized via a simple hydrothermal process. The QDs have a fluorescence emission band maximum at 595 nm with a quantum yield of 11%. The obtained CdS QDs exhibit a particle size of 1.63 ± 0.28 nm and look like quantum dot flowers. Basically, the fluorescence intensity of L-Asp@CdS QDs can be enhanced only upon addition of Ag+ and a redshift in the fluorescence spectrum was observed. Under optimum conditions, the fluorescence enhancement of L-Asp@CdS QDs appeared to exhibit a good linear relationship in between 100-7000 nM (R2 = 0.9945) with the Ag+ concentration, with a detection limit of 39 nM. The results indicated that the L-Asp@CdS QDs were well used in detection for Ag+ as fluorescence probe in aqueous solution with high sensitivity and selectivity. Moreover, the sensing system has been applied in detection Ag+ in real water samples. The recovery test results were 98.6%~113%, and relative standard deviation (n = 5) is less than 3.6%, which was satisfactory.

Thioglycolic acid-capped ZnSe quantum dots as nanoprobe for cobalt(II) and iron(III) via measurement of grey level, UV-vis spectra and dynamic light scattering.

Thioglycolic acid-functionalized ZnSe quantum dots (QDs) as a colorimetric nanoprobe were prepared and applied to the determination of cobalt(II) and iron(III). Test strips were obtained by a dipping-drying process. On exposure to Co(II), they undergo a color change from white to brown, and on exposure to Fe(III) from white to pink. The limits of detection (LOD) are 2.6 mg L-1 for Co(II) and 2.2 mg L-1 for Fe(III). Test strips introduce a low-cost, portable, rapid and convenient tool for determination of Co(II) and Fe(III). In addition, two other analytical methods have been studied for detection of Co(II) and Fe(III) at low concentration. The first is UV-vis spectrometry which has a LOD as low as 0.14 mg L-1 for Co(II) (at 412 nm) and 0.12 mg L-1 for Fe(III) (at 400 nm). The second is dynamic light scattering (DLS) with a LOD of 3.0 µg L-1 for Co(II) and 2.5 µg L-1 for Fe(III). Graphical abstract Thioglycolic acid-functionalized ZnSe quantum dots (TGA-ZnSe QDs) show high sensitivity and low detection limits for Co2+ and Fe3+.

The Fluorescent Quenching Mechanism of N and S Co-Doped Graphene Quantum Dots with Fe3+ and Hg2+ Ions and Their Application as a Novel Fluorescent Sensor.

The fluorescence intensity of N, S co-doped graphene quantum dots (N, S-GQDs) can be quenched by Fe3+ and Hg2+. Density functional theory (DFT) simulation and experimental studies indicate that the fluorescence quenching mechanisms for Fe3+ and Hg2+ detection are mainly attributed to the inner filter effect (IFE) and dynamic quenching process, respectively. The electronegativity difference between C and doped atoms (N, S) in favor to introduce negative charge sites on the surface of N, S-GQDs leads to charge redistribution. Those negative charge sites facilitate the adsorption of cations on the N, S-GQDs' surface. Atomic population analysis results show that some charge transfer from Fe3+ and Hg2+ to N, S-GQDs, which relate to the fluorescent quenching of N, S-GQDs. In addition, negative adsorption energy indicates the adsorption of Hg2+ and Fe2+ is energetically favorable, which also contributes to the adsorption of quencher ions. Blue fluorescent N, S-GQDs were synthesized by a facile one-pot hydrothermal treatment. Fluorescent lifetime and UV-vis measurements further validate the fluorescent quenching mechanism is related to the electron transfer dynamic quenching and IFE quenching. The as-synthesized N, S-GQDs were applied as a fluorescent probe for Fe3+ and Hg2+ detection. Results indicate that N, S-GQDs have good sensitivity and selectivity on Fe3+ and Hg2+ with a detection limit as low as 2.88 and 0.27 nM, respectively.

Pd-Functionalized SnO2 Nanofibers Prepared by Shaddock Peels as Bio-Templates for High Gas Sensing Performance toward Butane.

Pd-functionalized one-dimensional (1D) SnO2 nanostructures were synthesized via a facile hydrothermal method and shaddock peels were used as bio-templates to induce a 1D-fiber-like morphology into the gas sensing materials. The gas-sensing performances of sensors based on different ratios of Pd-functionalized SnO2 composites were measured. All results indicate that the sensor based on 5 mol % Pd-functionalized SnO2 composites exhibited significantly enhanced gas-sensing performances toward butane. With regard to pure SnO2, enhanced levels of gas response and selectivity were observed. With 5 mol % Pd-functionalized SnO2 composites, detection limits as low as 10 ppm with responses of 1.38 ± 0.26 were attained. Additionally, the sensor exhibited rapid response/recovery times (3.20/6.28 s) at 3000 ppm butane, good repeatability and long-term stability, demonstrating their potential in practical applications. The excellent gas-sensing performances are attributed to the unique one-dimensional morphology and the large internal surface area of sensing materials afforded using bio-templates, which provide more active sites for the reaction between butane molecules and adsorbed oxygen ions. The catalysis and "spillover effect" of Pd nanoparticles also play an important role in the sensing of butane gas as further discussed in the paper.