Ni-decorated carbon nanotubes (CNTs) derived from ethanol for electrooxidation of furan derivatives featuring H2 production

This study explores advancements in concurrent biorefinery and hydrogen production using Ni-decorated CNTs derived from bioethanol as electrocatalysts, showing the complete conversion of furan derivatives to the desired products with 95-97% selectivity and a hydrogen production rate of 75 μmol h-1. These findings highlight the simultaneous upgrading of biomass-derived compounds and hydrogen production.

Surface enhanced Raman spectroscopy sensor based on silver nanoparticles/multi wall carbon nanotubes for ultrasensitive detection of cholesterol

Cholesterol is vital for living things because of an important part of cell membranes, as well as one of the basic components of brain and nerve cells. However, cholesterol must be at an optimum level. If it is below or above this level, it is a marker of many various diseases. Therefore, the detection of cholesterol amount is very important. Herein, MWCNTs were synthesized and AgNPs were grown on their surfaces. Thus, AgNP/MWCNT hybrid material was obtained. The AgNP/MWCNTs were used as surface enhancement Raman scattering (SERS) substrate to quantify the cholesterol molecule. High SERS enhancement of AgNP/MWCNT, specific SERS sensing platform and high sensitive SERS substrate were proposed to determine and monitor cholesterol molecule. AgNP/MWCNT substrate was studied in the concentration range of 10-3-10-10 M and the limit of detection (LOD) was calculated as 3.24 × 10-11 M. In addition, the enhancement factor (EF) was determined as 6.21 × 109. As a result, it was reported in this study that cholesterol molecule can be determined with excellent accuracy, precision and sensitive by using AgNP/MWCNT substrate and therefore it can provide great potential in clinical diagnosis and health management.

Anticancer Activity of Au/CNT Nanocomposite Fabricated by Nanosecond Pulsed Laser Ablation Method on Colon and Cervical Cancer

Gold nanoparticles (AuNPs) and carbon nanotubes (CNTs) are increasingly being investigated for cancer management due to their physicochemical properties, low toxicity, and biocompatibility. This study used an eco-friendly technique (laser synthesis) to fabricate AuNP and Au/CNT nanocomposites. AuNPs, Au/CNTs, and CNTs were tested as potential cancer nanotherapeutics on colorectal carcinoma cells (HCT-116) and cervical cancer cells (HeLa) using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. In addition, the non-cancer embryonic kidney cells HEK-293 were taken as a control in the study. The cell viability assay demonstrated a significant reduction in cancer cell population post 48 h treatments of AuNPs, and Au/CNTs. The average cell viabilities of AuNPs, Au/CNTs, and CNTs for HCT-116 cells were 50.62%, 65.88%, 93.55%, and for HeLa cells, the cell viabilities were 50.88%, 66.51%, 91.73%. The cell viabilities for HEK-293 were 50.44%, 65.80%, 93.20%. Both AuNPs and Au/CNTs showed higher cell toxicity and cell death compared with CNT nanomaterials. The treatment of AuNPs and Au/CNTs showed strong inhibitory action on HCT-116 and HeLa cells. However, the treatment of CNTs did not significantly decrease HCT-116 and HeLa cells, and there was only a minor decrease. The treatment of AuNPs, and Au/CNTs, on normal HEK-293 cells also showed a significant decrease in cell viability, but the treatment of CNTs did not produce a significant decrease in the HEK-293 cells. This study shows that a simplified synthesis technique like laser synthesis for the preparation of high-purity nanomaterials has good efficacy for possible future cancer therapy with minimal toxicity.

Advances in Novel Nanomaterial-Based Optical Fiber Biosensors-A Review

This article presents a concise summary of current advancements in novel nanomaterial-based optical fiber biosensors. The beneficial optical and biological properties of nanomaterials, such as nanoparticle size-dependent signal amplification, plasmon resonance, and charge-transfer capabilities, are widely used in biosensing applications. Due to the biocompatibility and bioreceptor combination, the nanomaterials enhance the sensitivity, limit of detection, specificity, and response time of sensing probes, as well as the signal-to-noise ratio of fiber optic biosensing platforms. This has established a practical method for improving the performance of fiber optic biosensors. With the aforementioned outstanding nanomaterial properties, the development of fiber optic biosensors has been efficiently promoted. This paper reviews the application of numerous novel nanomaterials in the field of optical fiber biosensing and provides a brief explanation of the fiber sensing mechanism.

Sensitive MnFe2O4-Ag hybrid nanoparticles with photothermal and magnetothermal properties for hyperthermia applications

In this study, we present an experiment showing that designing multifunctional MnFe2O4-Ag nanoparticles to act as a dual hyperthermia agent is an efficient route for enhancing their heating ability. Interestingly, the specific absorption rate of the heteromeric MnFe2O4-Ag nanoparticles increased 2.7 times under simultaneous irradiation of a 100 Oe magnetic field and 0.14 W cm-2 laser compared to the action by the magnetic field alone, and more interestingly, is 30% higher than the sum of the two individual actions. The synergistic benefit of the magneto- and photo-thermal properties of the heteromeric structure can reduce the strengths of the magnetic field and laser intensities as well as their irradiation time to levels lower than those required in their hyperthermia applications individually. In vitro cytotoxicity analysis performed on HepG2 liver cancer and Hela cervical cancer cell lines showed that IC50 values were 83 ± 5.6 μg mL-1 (for HepG2) and 122.6 ± 19.8 μg mL-1 (for Hela cells) after 48 h of incubation, therefore, the nanoparticles are moderately cytotoxic and nontoxic to HepG2 and Hela cells, respectively; which offers the potential of safe therapy.

Single-walled carbon nanotube membranes as non-reflective substrates for nanophotonic applications

We demonstrate that single-walled carbon nanotube (SWCNT) membranes can be successfully utilized as nanometer-thick substrates for enhanced visualization and facilitated study of individual nanoparticles. As model objects, we transfer optically resonant 200 nm silicon nanoparticles onto pristine and ethanol-densified SWCNT membranes by the femtosecond laser printing method. We image nanoparticles by scanning electron and bright-field optical microscopy, and characterize by linear and Raman scattering spectroscopy. The use of a pristine SWCNT membrane allows to achieve an order-of-magnitude enhancement of the optical contrast of the nanoparticle bright field image over the results shown in the case of the glass substrate use. The observed optical contrast enhancement is in agreement with the spectrophotometric measurements showing an extremely low specular reflectance of the pristine membrane (≤0.1%). Owing to the high transparency, negligibly small reflectance and thickness, SWCNT membranes offer a variety of perspective applications in nanophotonics, bioimaging and synchrotron radiation studies.

Hydrothermally Assisted Synthesis of Porous Polyaniline@Carbon Nanotubes-Manganese Dioxide Ternary Composite for Potential Application in Supercapattery

In this study, ternary composites of polyaniline (PANI) with manganese dioxide (MnO₂) nanorods and carbon nanotubes (CNTs) were prepared by employing a hydrothermal methodology and in-situ oxidative polymerization of aniline. The morphological analysis by scanning electron microscopy showed that the MnO₂ possessed nanorod like structures in its pristine form, while in the ternary PANI@CNT/MnO₂ composite, coating of PANI over CNT/MnO₂, rods/tubes were evidently seen. The structural analysis by X-ray diffraction and X-ray photoelectron spectroscopy showed peaks corresponding to MnO₂, PANI and CNT, which suggested efficacy of the synthesis methodology. The electrochemical performance in contrast to individual components revealed the enhanced performance of PANI@CNT/MnO₂ composite due to the synergistic/additional effect of PANI, CNT and MnO₂ compared to pure MnO₂, PANI and PANI@CNT. The PANI@CNT/MnO₂ ternary composite exhibited an excellent specific capacity of 143.26 C g^-1 at a scan rate of 3 mV s^-1. The cyclic stability of the supercapattery (PANI@CNT/MnO₂/activated carbon)-consisting of a battery type electrode-demonstrated a gradual increase in specific capacity with continuous charge-discharge over ~1000 cycles and showed a cyclic stability of 119% compared to its initial value after 3500 cycles.

Carbon-Based Nanomaterials for Plasmonic Sensors: A Review

The surface plasmon resonance (SPR) technique is a remarkable tool, with applications in almost every area of science and technology. Sensing is the foremost and majorly explored application of SPR technique. The last few decades have seen a surge in SPR sensor research related to sensitivity enhancement and innovative target materials for specificity. Nanotechnological advances have augmented the SPR sensor research tremendously by employing nanomaterials in the design of SPR-based sensors, owing to their manifold properties. Carbon-based nanomaterials, like graphene and its derivatives (graphene oxide (GO)), (reduced graphene oxide (rGO)), carbon nanotubes (CNTs), and their nanocomposites, have revolutionized the field of sensing due to their extraordinary properties, such as large surface area, easy synthesis, tunable optical properties, and strong compatible adsorption of biomolecules. In SPR based sensors carbon-based nanomaterials have been used to act as a plasmonic layer, as the sensitivity enhancement material, and to provide the large surface area and compatibility for immobilizing various biomolecules, such as enzymes, DNA, antibodies, and antigens, in the design of the sensing layer. In this review, we report the role of carbon-based nanomaterials in SPR-based sensors, their current developments, and challenges.

Quantitative SERS by electromagnetic enhancement normalization with carbon nanotube as an internal standard

Quantitative surface-enhanced Raman scattering (SERS) in practical applications still remain unresolved, mainly due to low reproducibility relying on the quality of the SERS substrates. In this paper, a carbon nanotube and Ag nanoparticles composite (CNT/AgNPs) is reported, and the carbon nanotube is as an internal standard for the calibration of SERS intensity of analyte molecules. The quantification of analyte molecules rhodamine 6G (R6G) is demonstrated in an aqueous solution with the concentration of 10-9 to 10-7 M. Raman mapping is used to investigate the stability of SERS spectra in a large scanning area, and the corresponding relative standard deviation (RSD) is calculated. SERS mapping reveals that the uniformity of Raman enhancement is improved through the build-in calibration with 2D Raman peak of CNT. Meanwhile, CNT/AgNPs samples are used to detect N2 in natural air, indicating that such self-calibration method can improve the reliability of the SERS analysis.

Highly Sensitive Ethanol Chemical Sensor Based on Novel Ag-Doped Mesoporous α-Fe2O3 Prepared by Modified Sol-Gel Process

Mesoporous α-Fe₂O₃ has been synthesized via a simple sol-gel procedure in the presence of Pluronic (F-127) triblock copolymer as structure directing agent. Silver (Ag) nanoparticles were deposited onto α-Fe₂O₃ matrix by the photochemical reduction approach. Morphological analysis revealed the formation of Ag nanoparticles with small sizes < 20 nm onto the mesoporous structure of α-Fe₂O₃ possessing < 50 nm semi-spherical shape. The XRD, FTIR, Raman, UV-vis, PL, and N₂ sorption isotherm studies confirmed the high crystallinity, mesoporosity, and optical characteristics of the synthesized product. The electrochemical sensing toward liquid ethanol has been performed using the current devolved Ag/α-Fe₂O₃-modified glassy carbon electrode (GCE) by cyclic voltammetry (CV) and current potential (I-V) techniques, and the obtained results were compared with bare GCE or pure α-Fe₂O₃. Mesoporous Ag/α-Fe₂O₃ was found to largely enhance the sensor sensitivity and it exhibited excellent sensing characteristics during the precision detection of low concentrations of ethanol. High and reproducible sensitivity of 41.27 μAmM^- 1 cm^- 2 at lower ethanol concentration region (0.05 to 0.8 mM) and 2.93 μAmM^- 1 cm^- 2 at higher concentration zone (0.8 to 15 mM), with a limit of detection (LOD) of 15.4 μM have been achieved. Investigation on reaction kinetics revealed a characteristic behavior of mixed surface and diffusion-controlled processes. Detailed sensing studies revealed also that the sensitivity toward ethanol was higher than that of methanol or isopropanol. With further effort in developing the synthesis and fabrication approaches, a proper utility for the current proposed protocol for fabricating a better sensor device performance is possible.

Origin of enhancement in Raman scattering from Ag-dressed carbon-nanotube antennas: experiment and modelling

The D- and G-band Raman signals from random arrays of vertically aligned, multi-walled carbon nanotubes are significantly enhanced (up to ∼14×) while the signal from the underlying Si substrate is simultaneously attenuated (up to ∼6×) when the nanotubes are dressed, either capped or coated, with Ag. These Ag-induced counter-changes originate with the difference in geometry of the nanotubes and planar Si substrate and contrast in the Ag depositions on the substrate (essentially thin film) and the nanotube (nano-particulate). The surface integral equation technique is used to perform detailed modelling of the electromagnetic response of the system in a computationally efficient manner. Within the modelling the overall antenna response of the Ag-dressed nanotubes is shown to underpin the main contribution to enhancement of the nanotube Raman signal with hot-spots between the Ag nanoparticles making a subsidiary contribution on account of their relatively weak penetration into the nanotube walls. Although additional hot-spot activity likely accounts for a shortfall in modelling relative to experiment it is nonetheless the case that the significant antenna-driven enhancement stands in marked contrast to the hot-spot dominated enhancement of the Raman spectra from molecules adsorbed on the same Ag-dressed structures. The Ag-dressing procedure for amplifying the nanotube Raman output not only allows for ready characterisation of individual nanotubes, but also evidences a small peak at ∼1150 cm^-1 (not visible for the bare, undressed nanotube) which is suggested to be due to the presence of trans-polyacetylene in the structures.

Microcapsules from diverse polyfunctional materials: synergistic interactions for a sharp response to pH changes

Responsive microcapsules with strong synergistic interactions were prepared using a copolymer, silver nanoparticles and carbon nanotubes.

Characterization, uniformity and photo-catalytic properties of graphene/TiO2 nanocomposites via Raman mapping

Three types of anatase TiO₂, graphene-TiO₂, TiO₂-graphene composites (G/TiO₂) were developed, synthesized via a combination of simple sol-gel self-assembly method and additional thermal annealing process. Their structures and properties are determined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), atomic force microscopy (AFM) and Raman spectrum analysis. In addition, Raman spectra of TiO₂ and graphene, the band shift and intensity of G and 2D band were analyzed, in order to verify the mutual coupling between TiO₂ and graphene. Combined Raman mapping with AFM analysis, the agglomeration effect of TiO₂ nanoparticles was figured out by quantitative analysis. Finally, the photo-catalytic properties of three kinds of composites were experimentally studied via Raman mapping measurements. The results reveal that graphene with high electron mobility, as an acceptor through interfacial interactions, was certificated to enhance the photo-catalytic effect of TiO₂.