Search Results (27)

This paper reports several preliminary investigations concerning the relative humidity (RH) detection response of a chemiresistive sensor that uses a novel sensing layer based on pristine carbon nano-onions (CNOs) and polyvinyl alcohol (PVA) at a 1/1 and 2/1 w/w ratio. The sensing device, including a Si/SiO₂ substrate and gold electrodes, is obtained by depositing the CNOs–PVA aqueous suspension on the sensing structure by drop casting. The composition and morphology of the sensing film are explored by means of scanning electron microscopy, Raman spectroscopy, atomic force microscopy, and X-ray diffraction. The manufactured sensor’s room temperature RH detection performance is examined by applying a continuous flow of the electric current between the interdigitated electrodes and measuring the voltage as the RH varies from 5% to 95%. For RH below 82% (sensing layer based on CNOs–PVA at 1/1 w/w ratio) or below 50.5% (sensing layer based on CNOs–PVA at 2/1 w/w ratio), the resistance varies linearly with RH, with a moderate slope. The newly developed sensor, using CNOs–PVA at a 1:1 ratio (w/w), responded as well as or better than the reference sensor. At the same time, the recorded recovery time was about 30 s, which is half the recovery time of the reference sensor. Additionally, the changes in resistance (ΔR/ΔRH) for different humidity levels showed that the CNOs–PVA layer at 1:1 was more sensitive at humidity levels above 80%. The main RH sensing mechanisms considered and discussed are the decrease in the hole concentration in the CNOs during the interaction with an electron donor molecule, such as water, and the swelling of the hydrophilic PVA. The experimental RH detection data are analyzed and compared with the RH sensing results reported in previously published work on RH detectors employing sensing layers based on oxidized carbon nanohorns–polyvinylpirrolidone (PVP), oxidized carbon nanohorns–PVA and CNOs–polyvinylpyrrolidone. Full article

The study presents the ethanol vapor sensing performance of a resistive sensor that utilizes a quaternary nanohybrid sensing layer composed of holey carbon nanohorns (CNHox), graphene oxide (GO), SnO₂, and polyvinylpyrrolidone (PVP) in an equal mass ratio of 1:1:1:1 (w/w/w/w). The sensing device includes a flexible polyimide substrate and interdigital transducer (IDT)-like electrodes. The sensing film is deposited by drop-casting on the sensing structure. The morphology and composition of the sensitive film are analyzed using scanning electron microscopy (SEM), Energy Dispersive X-ray (EDX) Spectroscopy, and Raman spectroscopy. The manufactured resistive device presents good sensitivity to concentrations of alcohol vapors varying in the range of 0.008–0.16 mg/cm³. The resistance of the proposed sensing structure increases over the entire range of measured ethanol concentration. Different types of sensing mechanisms are recognized. The decrease in the hole concentration in CNHox, GO, and CNHox due to the interaction with ethanol vapors, which act as electron donors, and the swelling of the PVP are plausible and seem to be the prevalent sensing pathway. The hard–soft acid-base (HSAB) principle strengthens our analysis. Full article

Tert-butylhydroquinone (TBHQ) is a phenolic substance that is commonly employed to prevent food oxidation. Excessive or improper utilization of this antioxidant can not only impact food quality but may also pose potential risks to human health. In this study, an ultrasensitive, stable, and easily operable ratiometric electrochemical sensor was successfully fabricated by combining the tubular (3,4-ethylenedioxythiophene) (T-PEDOT) with single-wall carbon nanohorns (SWCNHs) for the detection of TBHQ antioxidants in food. The SWCNHs/T-PEDOT nanocomposite fabricated through ultrasound-assisted and template approaches was employed as the modified substrate for the electrode interface. The synergistic effect of SWCNHs and T-PEDOT, which possess excellent electrical conductivity and catalytic properties, enabled the modified electrode to showcase remarkable electrocatalytic performance towards TBHQ, with the redox signal of methylene blue serving as an internal reference. Under optimized conditions, the SWCNHs/T-PEDOT-modified electrode demonstrated good linearity within the TBHQ concentration range of 0.01–200.0 μg mL⁻¹, featuring a low limit of detection (LOD) of 0.005 μg mL⁻¹. The proposed ratiometric electrochemical sensor displayed favorable reproducibility, stability, and anti-interference capacity, thereby offering a promising strategy for monitoring the levels of TBHQ in oil-rich food products. Full article

Oxidized carbon nanohorn (CNHox) a carbon nanomaterial that has attracted attention due to its unique material properties. It is expected to be applied in various areas like cancer treatment, gene-expression technology, fluids with high thermal conductivity, lubricants, and so on. While the rheological measurements of suspensions provide information on the effective size and interactions of suspended particles, the rheological behaviors of aqueous suspensions of CNHox have never been systematically investigated. To clarify the rheological behaviors of aqueous suspensions of CNHox, their viscosity and dynamic viscoelasticity were measured with changing particle concentration and salt concentration. The viscosity of a CNHox suspension showed yield stress at low shear rates and showed shear-thinning behavior with increasing shear rates. The viscosity of 5 weight % CNHox suspensions was comparable to that of 60 weight % silica suspensions. This high viscosity at a low CNHox concentration is probably due to the porous structure and large effective volume of the CNHox particle. The estimated effective volume of CNHox calculated by the Krieger−Dougherty equation was 18.9 times larger than the actual volume calculated by the mass concentration and density. The dependence of rheological behavior of the CNHox suspension on salt concentration was weak compared to that of the colloidal silica suspension. This weak dependence on salt concentration may be due to the roughness of the particle surface, which would weaken the effect of electric double-layer interactions and/or van der Waals interactions between particles. These rheological behaviors of the aqueous suspension of CNHox shown in this research will be useful in efforts to improve the efficiency of its utilization for the various applications. Full article

In this study, oxidized single-walled carbon nanohorns (oxSWCNHs) were prepared using nitric acid oxidation and subsequently combined with 3′6-carboxyfluorescein through charge transfer to prepare fluorescent probes. These oxSWCNHs were used to quench fluorogen signals at short distances and dissociate ssDNA using cryonase enzymes. We established a method for rapidly detecting tetracycline (TC) in complex samples based on the amplification of cryonase enzyme signals. After optimizing the experimental conditions, our method showed a detection limit of 5.05 ng/mL, with good specificity. This method was used to determine the TC content in complex samples, yielding a recovery rate of 90.0–103.3%. This result validated the efficacy of our method in detecting TC content within complex samples. Full article

To clarify the effect of proteins on the charging and aggregation–dispersion characteristics of oxidized carbon nanohorn (CNHox), we measured the electrophoretic mobility and stability ratios as a function of concentrations of a model protein, lysozyme (LSZ), and KCl. The zeta potential from the electrophoretic mobility of CNHox was neutralized and reversed by the addition of oppositely charged LSZ. Electrical and hydrophobic interactions between CNHox and LSZ can be attributed to the adsorption and charge reversal of CNHox. The stability ratio of CNHox in the presence or absence of LSZ showed Derjaguin–Landau and Verwey–Overbeek (DLVO) theory-like behavior. That is, the slow aggregation regime, fast aggregation regime, and critical coagulation concentration (CCC) were identified. At the isoelectric point, only the fast aggregation regime was shown. The existence of patch-charge attraction due to the charge heterogeneity on the surface was inferred to have happened due to the enhanced aggregation of CNHox at high LSZ dosage and low electrolyte concentration. The relationship between critical coagulation ionic strength and surface charge density at low LSZ dosage showed that the aggregation of CNHox is in line with the DLVO theory. An obvious decrement in the Hamaker constant at high LSZ dosage can probably be found due to an increased interaction of LSZ-covered parts. Full article

Combination therapy for cancer is expected for the synergetic effect of different treatments, and the development of promising carrier materials is demanded for new therapeutics. In this study, nanocomposites including functional nanoparticles (NPs) such as samarium oxide NP for radiotherapy and gadolinium oxide NP as a magnetic resonance imaging agent were synthesized and chemically combined with iron oxide NP-embedded or carbon dot-coating iron oxide NP-embedded carbon nanohorn carriers, where iron oxide NP is a hyperthermia reagent and carbon dot exerts effects on photodynamic/photothermal treatments. These nanocomposites exerted potential for delivery of anticancer drugs (doxorubicin, gemcitabine, and camptothecin) even after being coated with poly(ethylene glycol). The co-delivery of these anticancer drugs played better drug-release efficacy than the independent drug delivery, and the thermal and photothermal procedures enlarged the drug release. Thus, the prepared nanocomposites can be expected as materials to develop advanced medication for combination treatment. Full article

The prognosis of castration-resistant prostate cancer (CRPC) is technically scarce; therefore, a novel treatment for CRPC remains warranted. To this end, hyperthermia (HT) was investigated as an alternative therapy. In this study, the analysis focused on the association between CRPC and heat shock protein nuclear import factor “hikeshi (HIKESHI)”, a factor of heat tolerance. Silencing the HIKESHI expression of 22Rv1 cells (human CRPC cell line) treated with siRNAs inhibited the translocation of heat shock protein 70 from the cytoplasm to the nucleus under heat shock and enhanced the effect of hyperthermia. Moreover, a novel magnetic nanoparticle was developed via binding carbon nanohorn (CNH) and iron oxide nanoparticle (IONP) with 3-aminopropylsilyl (APS). Tumor-bearing model mice implanted with 22 Rv1 cells were examined to determine the effect of magnetic HT (mHT). We locally injected CNH-APS-IONP into the tumor, which was set under an alternative magnetic field and showed that tumor growth in the treatment group was significantly suppressed compared with other groups. This study suggests that HIKESHI silencing enhances the sensitivity of 22Rv1 cells to HT, and CNH-APTES-IONP deserves consideration for mHT. Full article

In this study, a resistive humidity sensor for moisture detection at room temperature is presented. The thin film proposed as a critical sensing element is based on a quaternary hybrid nanocomposite CNHox//SnO₂/ZnO/PVP (oxidated carbon nanohorns–tin oxide–zinc oxide–polyvinylpyrrolidone) at the w/w/w/w ratios of 1.5/1/1/1 and 3/1/1/1. The sensing structure consists of a Si/SiO₂ dielectric substrate and interdigitated transducers (IDT) electrodes, while the sensing film layer is deposited through the drop-casting method. Morphology and composition of the sensing layers were investigated through scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction, and Raman spectroscopy. Each quaternary hybrid nanocomposite-based thin film’s relative humidity (RH) sensing capability was analyzed by applying a direct current with known intensity between two electrodes and measuring the voltage difference when varying the RH from 0% to 100% in a humid nitrogen atmosphere. While the sensor with CNHox/SnO₂/ZnO/PVP at 1.5/1/1/1 as the sensing layer has the better performance in terms of sensitivity, the structure employing CNHox//SnO₂/ ZnO/PVP at 3/1/1/1 (mass ratio) as the sensing layer has a better performance in terms of linearity. The contribution of each component of the quaternary hybrid nanocomposites to the sensing performance is discussed in relation to their physical and chemical properties. Several alternative sensing mechanisms were taken into consideration and discussed. Based on the measured sensing results, we presume that the impact of the p-type semiconductor behavior of CNHox, in conjunction with the swelling of the hydrophilic polymer, is dominant and leads to the overall increasing resistance of the sensing film. Full article

In this paper, we present the relative humidity (RH) sensing response of a chemiresistive sensor, employing sensing layers based on a ternary nanohybrids comprised of holey carbon nanohorns (CNHox), titanium (IV) oxide, and polyvinylpyrrolidone (PVP) at 1/1/1/(T1), 2/1/1/(T2), and with 3/1/1 (T3) mass ratios. The sensing device is comprised of a silicon-based substrate, a SiO₂ layer, and interdigitated transducer (IDT) electrodes. The sensitive layer was deposited via the drop-casting method on the sensing structure, followed by a two-step annealing process. The structure and composition of the sensing films were investigated through scanning electron microscopy (SEM), Raman spectroscopy, and X-ray diffraction (XRD). The resistance of the ternary nanohybrid-based sensing layer increases when H increases between 0% and 80%. A different behavior of the sensitive layers is registered when the humidity increases from 80% to 100%. Thus, the resistance of the T1 sensor slightly decreases with increasing humidity, while the resistance of sensors T2 and T3 register an increase in resistance with increasing humidity. The T2 and T3 sensors demonstrate a good linearity for the entire (0–100%) RH range, while for T1, the linear behavior is limited to the 0–80% range. Their overall room temperature response is comparable to a commercial humidity sensor, characterized by a good sensitivity, a rapid response, and fast recovery times. The functional role for each of the components of the ternary CNHox/TiO₂/PVP nanohybrid is explained by considering issues such as their electronic properties, affinity for water molecules, and internal pore accessibility. The decreasing number of holes in the carbonaceous component at the interaction with water molecules, with the protonic conduction (Grotthus mechanism), and with swelling were analyzed to evaluate the sensing mechanism. The hard–soft acid-base (HSAB) theory also has proven to be a valuable tool for understanding the complex interaction of the ternary nanohybrid with moisture. Full article

The relative humidity (RH) sensing response of a chemoresistive sensor using a novel ternary hybrid nanocomposite film as a sensing element is presented. The sensitive layer was obtained by employing the drop-casting technique for depositing a thin film of nanocomposite between the electrodes of an interdigitated (IDT) structure. The sensing support structure consists of an IDT dual-comb structure fabricated on a oSi-SiO₂ substrate. The IDT comprises chromium, as an adhesion layer (10 nm thickness), and a gold layer (100 nm thickness). The sensing capability of a novel thin film based on a ternary hybrid made of oxidated carbon nanohorns–titanium dioxide–polyvinylpyrrolidone (CNHox/TiO₂/PVP) nanocomposite was investigated by applying a direct current with known intensity between the two electrodes of the sensing structure, and measuring the resulting voltage difference, while varying the RH from 0% to 100% in a humid nitrogen atmosphere. The ternary hybrid-based thin film’s resistance increased when the sensors were exposed to relative humidity ranging from 0 to 100%. It was found that the performance of the new chemoresistive sensor is consistent with that of the capacitive commercial sensor used as a benchmark. Raman spectroscopy was used to provide information on the composition of the sensing layer and on potential interactions between constituents. Several sensing mechanisms were considered and discussed, based on the interaction of water molecules with each component of the ternary nanohybrid. The sensing results obtained lead to the conclusion that the synergic effect of the p-type semiconductor behavior of the CNHox and the PVP swelling process plays a pivotal role in the overall resistance decrease of the sensitive film. Full article

This paper presents the relative humidity (RH) sensing response of a resistive sensor employing sensing layers based on a ternary nanocomposite comprising graphene oxide-oxidized carbon nanohorns-polyvinylpyrrolidone (GO-CNHox–PVP), at 1/1/1, 1/2/1, and 1/3/1 w/w/w mass ratios. The sensing structure is composed of a silicon substrate, a SiO₂ layer, and interdigitated transducers (IDT) electrodes, on which the sensing layer is deposited via the drop-casting method. The morphology and the composition of the sensing layers are investigated through scanning electron microscopy (SEM) and RAMAN spectroscopy. The RH sensing capability of each carbonaceous nanocomposite-based thin film was analyzed by applying a current between the two electrodes and by measuring the voltage difference when varying the RH from 0% to 100% in humid nitrogen. The sensors have a room temperature response comparable to that of a commercial humidity sensor and are characterized by a rapid response, excellent linearity, good sensitivity, and recovery time. The manufactured sensing devices’ transfer functions were established, and we extracted the response and recovery times. While the structures with GO/CNHox/PVP at 1/1/1 ratio (w/w/w) had the best performance in terms of relative sensibility, response time, and recovery time, the sensors employing the GO/CNHox/PVP nanocomposite at the 1/2/1 ratio (w/w/w) had the best linearity. Moreover, the ternary mixture proved to have much better sensing properties compared to CNHox and CNHox-PVP-based sensing layers in terms of sensitivity and linearity. Each component of the ternary nanocomposites’ functional role is explained based on their physical and chemical properties. We analyzed the potential mechanism associated with the sensors’ response; among these, the effect of the p-type semiconductor behavior of CNHox and GO, correlated with swelling of the PVP, was dominant and led to increased resistance of the sensing layer. Full article

We report the relative humidity (RH) sensing response of a resistive sensor, employing sensing layers, based on a quaternary organic–inorganic hybrid nanocomposite comprising oxidized carbon nanohorns (CNHox), graphene oxide (GO), tin dioxide, and polyvinylpyrrolidone (PVP), at 1/1/1/1 and 0.75/0.75/1/1/1 mass ratios. The sensing structure comprises a silicon substrate, a SiO₂ layer, and interdigitated transducer (IDT) electrodes. The sensing film was deposited via the drop-casting method on the sensing structure. The morphology and the composition of the sensing layers were investigated through Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), and RAMAN spectroscopy. The organic–inorganic quaternary hybrid-based thin film’s resistance increased when the sensors were exposed to relative humidity ranging from 0 to 100%. The manufactured devices show a room temperature response comparable to that of a commercial capacitive humidity sensor and characterized by excellent linearity, rapid response and recovery times, and good sensitivity. While the sensor with CNHox/GO/SnO₂/PVP at 0.75/0.75/1/1 as the sensing layer has the best performance in terms of linearity and recovery time, the structures employing the CNHox/GO/SnO₂/PVP at 1/1/1/1 (mass ratio) have a better performance in terms of relative sensitivity. We explained each constituent of the quaternary hybrid nanocomposites’ sensing role based on their chemical and physical properties, and mutual interactions. Different alternative mechanisms were taken into consideration and discussed. Based on the sensing results, we presume that the effect of the p-type semiconductor behavior of CNHox and GO, correlated with swelling of PVP, dominates and leads to the overall increasing resistance of the sensing layer. The hard–soft acid–base (HSAB) principle also supports this mechanism. Full article

Carbon nanohorns (CNHs) are attractive for various applications, where a high specific surface area and long dispersion stability in water are important. In the present work, we study these parameters of CNHs prepared by arc evaporation of graphite depending on the conditions of the synthesis and subsequent oxidation in air. It is shown that the addition of toluene in the reactor during the arcing allows obtaining CNHs functionalized with −CH_x groups. Heating of CNHs in air at 400 °C leads to substitution of −CH_x groups for oxygen-containing groups. Moreover, the CNH endcaps are opened at 500 °C, and as a result, the specific surface area of CNHs increases 4 times. Aqueous suspensions with a concentration of oxidized CNHs of 100 µg/mL are stable for 8 months. Full article

The results of in vitro studies of single-walled carbon nanohorn (SWCNH) oxidized materials’ cytotoxicity obtained by the cell membrane integrity (Neutral Red Uptake (NRU)) and metabolic activity (by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)) on A549 and human dermal fibroblasts (HDF) cell lines are presented. We also present hemocompatibility studies on human and porcine blood, and an erythrocyte concentrate to prove that the obtained samples will not interfere with blood components. Characterization of the materials is supplemented by ζ-potential measurements, Transmission Electron Microscope (TEM) imaging, and thermogravimetric studies (TG). The presented results show the correlation between the specific surface area of materials and the platelet aggregation, when the I_D/I_G ratio determined from Raman spectra correlates with hemoglobin release from the erythrocytes (in whole blood testing). A plausible mechanism explaining the observed correlations is given. The cytotoxicity and hemocompatibility studies prove that the studied materials are acceptable for use in biomedical applications, especially a sample SWCNH-ox-1.5 with the best application potential. Full article