Mechanistic understanding of the sensing process by analyzing response curves of TiO2 based humidity sensors

Sensors function by interacting with an appropriate stimulus, undergo a change in property, which is then diagnosed by making some measurements. For any sensor, the type of interaction between analyte and sensor surface determines its overall performance. This article explores the philosophy in which primary measurements like response curves can hold information on the “type” of interaction occurring between analyte and sensing material. As case study, titanium oxide (TiO2) pellet sensors fabricated by sol-gel growth of TiO2 nanoparticles (as-grown and annealed) are investigated for humidity sensing at room temperature. The sensors display a very fast response in the 0%–30% relative humidity (%RH) range and return to their initial state without applying any external heat treatment. The response curves are analysed in view of adsorption processes guided by Langmuir isotherms. Correlation between sensor microstructure, adsorption processes and response curve is used to build the mechanistic understanding of the sensing process. The results bring out a unique correlation between sensor microstructure, interaction of analyte with sensing material and profile of response curves. Further, the synthesised sensors exhibit a linear response in the 0%–30% RH range making them suitable for low humidity environments like food packaging industry.

Stealth doxorubicin conjugated bimetallic selenium/silver nanoparticles for targeted cervical cancer therapy

Bimetallic nanosized delivery systems are attracting a lot of research interest as alternatives to monometallic delivery systems. This study evaluated the ability of bimetallic selenium silver chitosan pegylated folic acid targeted nanoparticles (SeAgChPEGFA NPs) to deliver doxorubicin (DOX) in cervical cancer cells. Comparison studies using monometallic selenium chitosan pegylated folic acid (SeChPEGFA NPs) targeted NPs and free DOX were also conducted. The prepared NPs and their drug nanocomplexes were characterised morphologically and physico-chemically. Drug binding and releasing studies were conducted under a simulated environment in vitro. The cytotoxicity and apoptosis studies were studied using the 3-[(4, 5-dimethylthiazol-2-yl)−2, 5-diphenyl tetrazolium bromide] (MTT) assay and the dual dye staining. The findings revealed that the bimetallic SeAgChPEGFA NPs displayed better colloidal stability, superior physico-chemical qualities, and higher binding abilities in comparison with monometallic SeChPEGFA NPs. In addition, the SeAgChPEGFA NPs showed the pH-triggered controlled drug release and cell-specific cytotoxicity. These findings suggest that the bimetallic NPs are superior delivery systems when compared to their monometallic NPs and free drug counterparts, thus, setting a platform for further in vivo examination.

Biological synthesis, physico-chemical characterization of undoped and Co doped α-Fe2O3 nanoparticles using Tribulus terrestris leaf extract and its antidiabetic, antimicrobial applications

Hematite (α-Fe2O3) nanoparticles (NPs) were chemically and thermodynamically more stable among iron oxide nanoparticles. Doping of Co2+ metal ion in α-Fe2O3 can modify the structural, optical and magnetic properties of NPs and also enhances the potential of the biomedical applications. In the current study, undoped and Co doped hematite nanoparticles were synthesised by co-precipitation method using Tribulus terrestris L. leaf extract as bio-reductant. The magnetic, optical and structural investigations were studied with the help of Ultraviolet-visible (UV-Vis), Fourier Transform Infrared (FTIR), Scanning Electron Microscopy equipped with Energy Dispersive X-ray (SEM-EDX) Spectroscopy, Vibrating Sample Magnetometer (VSM) and X-ray Diffraction (XRD) Spectroscopy. XRD analysis shows that synthesized nanoparticles were in hematite phase, rhombohedral in structure. XRD spectral pattern clearly evidenced that prepared α-Fe2O3 and Co-Fe2O3 NPs were highly crystalline with no impurity peaks. Using VSM spectra, the M-H curve indicates that saturation magnetisation (Ms) value increases for Co-Fe2O3 NPs than undoped α-Fe2O3 NPs, it can be clearly seen that doping largely affects the magnetic nature of nanoparticles. In the UV-Vis spectra, absorption maxima increases and band gap value decreases for cobalt doped hematite nanoparticles indicating the substitution of Fe2+ ions by Co2+ ions in α-Fe2O3 lattice sites. Antidiabetic and antimicrobial activity of the synthesized undoped and Co doped hematite NPs were tested by alpha-amylase inhibitory and disc diffusion method. The Co-Fe2O3 NPs have greatly inhibited the digestive enzyme and microbial strains as compared to undoped α-Fe2O3 NPs.

Facile green synthesis of ZnO–CuO nanocomposites using areca catechu leaves and their in vitro antidiabetic and cytotoxicity studies

The fabrication and diverse applications of mixed oxides have received immense interest due to numerous prospects for better functional performance in tuning their properties compared to the basic metal oxides. Herein, we report synthesis of ZnO-CuO nanocomposites (NCs) using a simple and green route solution combustion method. The as-prepared ZnO-CuO NCs have been characterised through x-ray diffraction (XRD), energy dispersive x-ray (EDX) with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The results revealed that as-prepared ZnO-CuO NCs have spherical and rod-shaped structures with an average size between 10 and 30 nm. Further, ZnO-CuO NCs were tested for antidiabetic and anticancer properties. Amylase inhibition and MTT assays were carried out with different concentrations of NCs. The biological results depicted that the as-prepared nanocomposites exhibited significant cytotoxic effects with IC50 value of 13.29 μg mg−1. These observations further showed that the newly synthesised ZnO–CuO NCs are interesting and promising nanomaterials in pharmaceutical and healthcare sector.

Potential of nanoparticles and nanopolymers in treatment of age-associated diseases

Aging is an inevitable process caused by the accumulation of degenerative destructions, which ultimately leads to organism death. As the aging process occurs at the molecular, cellular, and tissue levels, understanding the whole details of age-related disorders is the prerequisite for the development of anti-aging therapy. More than 300 compounds of different sources have been reported with an anti-aging activity that controls age-related diseases through regulating single or multiple signalling pathways. Recent innovations in nanotechniques could lead to the development of nanomaterials having effects on age-associated malfunctions or acting as nanocarrier systems and distributers of anti-aging drugs. In this review, we summarised the molecular mechanisms of longevity and the prospect of developing anti-aging nanomaterials targeting aging pathways.

Helium isotope separation by bi-layer membranes of g-C3N4

The problem of helium isotope separation via bi-layer membranes of graphitic carbon nitride g-C3N4 has been studied. The probability of passing isotopes through the membrane is derived from solving the Schrödinger integral equation using Hermite polynomials. The potential energy of the membrane is calculated based on modified Lennard-Johnes potential. The separation degree of the 3He/4He reaches the value of 1045 due to the resonant effect.

Andrographis paniculata absorbed ZnO nanofibers as a potential antimicrobial agent for biomedical applications

The present study focuses on developing antimicrobial nanofibers with superhydrophobicity and insect repellent properties for wound dressing and biomedical applications. For the first time, Andrographis paniculata leaf extract was prepared and incorporated into ZnO nanofibers (AP-ZnO). The antifungal and antibacterial activities of AP-ZnO were tested using the agar plate method. Amid the bacteria and fungus strain tested, the prepared sample exhibited a greater efficiency against Staphylococcus aureus and Trichophyton rubrum respectively. AP-ZnO showed the highest larvicidal activity (100 ± 0.2) against Aedes aegypti, proving its insect repellent characteristics. The in vivo toxicity studies of AP-ZnO (100 μg ml−1) tested on Danio rerio ensure the biocompatibility of the prepared sample with maximum toxicity of 21.1% after 72 h, which is lower than commercial Prallethrin. Moreover, AP-ZnO-chitosan coated cotton fabric showed higher durability with contact angle (θ ∼ 151°) and was suggested to be used for self-cleaning applications in the biomedical sector. The examined results confirmed that AP-ZnO possesses different medicinal characteristics suitable for biomedical and pharmaceutical applications.

Dual-function of the ZnO nano-sheets as light absorber scaffold and electron transport material in perovskite solar cells

Recent advances in the development of perovskite solar cells using CH3NH3PbI3 as the absorber material have reached over 18.7% in power conversion efficiency. The best performance perovskite-based cells required support of a mesoporous charge collector. In this work we present a new process for preparing perovskite solar cells with the structure of AZO/Au/AZO(AAA)/ZnO-sheets/CH3NH3PbI3/HTM/Au. Herein, ZnO nanosheets layer was prepared by electrochemical deposition method using zinc nitrate hexahydrate as nutrient solution, then annealed at 150 °C in ambient air. The results show that high crystal ZnO sheets assembled simply from AZO top layer could act as electron transporter and scaffold for perovskite layer. The presentation of ZnO scaffold was exploited to improve 19% in power conversion efficiency, offering great promise for further improvement of the low-temperature, low-cost processing solar technology.

Structural, optical, and potential broad-spectrum antibacterial properties of CuO-Ag nanoparticles biosynthesized using the extract of Diospyros discolor Willd

The development of new material properties for antimicrobial agents to address the problem of antibiotic resistance is currently being explored. Silver and copper exhibit oligodynamic properties, which inhibit the growth of microorganisms. These properties are stronger at the nanoscale than the macroscale, especially for bimetallic nanoparticles (NPs). In this study, we synthesized bimetallic CuO and Ag NPs using Diospyros discolor Willd. (Velvet apple) leaf extract with three different ratios of Cu and Ag precursors: 1:0.01, 1:0.1, and 1:1 (v/v). In addition, the optical properties of these NPs were characterised using UV-Vis spectrophotometer, which showed the typical absorbance peak in the range of 300–400 nm. The size and shape of the CuO and Ag nanoparticles were analysed using a scanning electron microscope (SEM) and transmission electron microscope (TEM) images. The SEM and TEM images showed leaf-shaped CuO nanoplates and spherical AgNPs. Furthermore, the crystalline properties were analysed using x-ray diffraction (XRD). This study produced CuO-Ag nanoclusters with a particular morphology, size, and composition. The antibacterial assay showed potential broad-spectrum activity for Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) as well as Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa).

Post-synthesis treatment of graphene oxide/silica particles nanocomposite with piranha acid for functionalization

The discovery of 2D materials has led researchers to a broad material platform. Their excellent physical, chemical and electrical properties along with the layered structure have found applications in various fields. However, these materials also have limitations and functionalisation is one of the mechanisms that improves their properties. In our previous work, we observed surface-enhanced Raman spectroscopy (SERS) after covalent attachment of protein to the graphene nanocomposite where piranha acid was used to generate the functional groups. The current work describes the synthesis and characterisation of a graphene oxide-silica particle nanocomposite after piranha acid treatment at different time intervals. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy were performed to indicate structural changes which facilitated the protein attachment. The SEM and TEM results indicated that the sample which was piranha acid activated for 3 min displayed better arrangement of silica particles on the graphene sheets with exposition of the highest net surface area in the graphene sheet, compared to the other samples and determined to be the best functionalised nanocomposite for further applications. Morphological instability of the graphene sheets and clustering of silica particles were observed in the samples treated for more than 3 min. Interestingly, the same degree of graphitisation was observed in all the samples when I D /I G ratios {(≤0.99) ≠ 0} were determined by Raman spectroscopy.