Correction to: A review on nanomaterial-modified optical fiber sensors for gases, vapors and ions.

The published version of this article, unfortunately, contains error. Corrections in Figs. 1, 3 and 5 were incorrectly carried out. Given in this article are the correct figures. The original article has been corrected.

A review on nanomaterial-modified optical fiber sensors for gases, vapors and ions.

The mesmerizing properties of nanomaterials and the features offered by optical fibers can be combined to result in an attractive new platform for chemical sensing. This review (with 230 refs.) summarizes the progress made in the past five years in the field of fiber-optic sensors: The first group comprises metals and metal oxides and their composites, and the second group comprises graphene, graphene oxides and CNTs, and its composites. By combining these nanocomposites with various optical fiber geometries, numerous sensors have been realized. Following an introduction, first section summarizes fiber-optic configuration for chemical sensing (including Fabry-Perot and Mach-Zehnder interferometry, surface plasmon resonance, and optical fiber gratings of the FBG and LPG type). The second section covers typical nanomaterials used in such sensors, with a first subsection on metals, metal oxides, their composites and nanostructured modifications, and a second subsection on graphenes, graphene oxides, carbon nanotubes, and their derivatives. Section 3 summarizes sensors (i) for various gaseous species (NH3, H2, CH4, H2S, CO2, NO2, O2), (ii) for volatile organic compounds (such as ethanol, methanol, acetone, toluene, and formaldehyde), and (iii) for heavy metal ions (such as Hg2+, Pb2+, Mg2+, Cd2+, Ni2+, and Mn2+). The merits and limitations of these nanomaterials and numerous examples for nanomaterial-based sensors are discussed and presented in the form of tables. A concluding section addresses technological challenges and future trends. Graphical Abstract Schematic presentation of an optical fiber modified with various nanomaterials such as metal oxides (MOXs), metals, carbon-nanotubes (CNTs) and graphene. Such sensors are based on several fiber-optic configurations like Fabry-Perot interferometers (FPI), Mach-Zehnder interferometer (MZI) (includes an in-line MZI), surface plasmon resonance (SPR) (includes coating on cladding and unclad part of an optical fiber) and fiber gratings (FGs) (includes fiber Bragg gratings (FBGs) and long-period gratings (LPGs), these are explored for detection of various gases (NH3, H2, H2S, CH4, O2, CO2), vapors (VOCs), and ions.

Microneedles of chitosan-porous carbon nanocomposites: Stimuli (pH and electric field)-initiated drug delivery and toxicological studies.

An array of microneedles (MNs) of chitosan-graphene assembled in porous carbon (CS-GAPC) nanocomposites has been synthesized and evaluated. The safety of the formulated system has been ensured using detailed in vivo toxicological studies and efficacy has been ensured by evaluating the stimuli (pH and electric field) initiated drug delivery properties. Drug cephalexin has been incorporated in these MNs. In vivo toxicological studies of CS-GAPC nanocomposite were performed on Sprague rats, using acute dermal and subacute dermal (ADT& SADT) test, histopathological studies, biochemical studies, and AMES tests. ADT and SADT studies showed that median lethal dose (LD50 ) was found greater than 2000 mg/kg body weight; with no abnormal weight gain and food consumption, during the study period of 28 days. This study showed that administration of CS-GAPC did not cause any substantial alterations in hematological and biochemical parameters of the animals. Histopathological studies showed no significant changes in the control and CS-GAPC administered groups. AMES tests reveal that CS-GAPC nanocomposite is nonmutagenic against the Salmonella thyphimurium strains. No abnormalities were observed in the animal's chromosomal aberrations and clastogenic values when the animals were treated with CS-GAPC. At acidic pH of 4, the encapsulated drug was completely released, indicating that the drug release from the prepared nanocomposite is pH dependent. An electric field of 5 V showed optimum drug release, as a function of applied electric pulses. A biologically safe drug encapsulation model system is hence projected for smart drug delivery (pH dependent and electric field triggered) using the microneedle approach. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1582-1596, 2019.

Sprayed zinc oxide films: Ultra-violet light-induced reversible surface wettability and platinum-sensitization-assisted improved liquefied petroleum gas response.

We report the rapid (superhydrophobic to superhydrophilic) transition property and improvement in the liquefied petroleum gas (LPG) sensing response of zinc oxide (ZnO) nanorods (NRs) on UV-irradiation and platinum (Pt) surface sensitization, respectively. The morphological evolution of ZnO NRs is evidenced from the field emission scanning electron microscope and atomic force microscope digital images and for the structural elucidation X-ray diffraction pattern is used. Elemental survey mapping is obtained from energy dispersive X-ray analysis spectrum. The optical properties have been studied by UV-Visible and photoluminescence spectroscopy measurements. The rapid (120sec) conversion of superhydrophobic (154°) ZnO NRs film to superhydrophilic (7°) is obtained under UV light illumination and the superhydrophobicity is regained by storing sample in dark. The mechanism for switching wettability behavior of ZnO NRs has thoroughly been discussed. In second phase, Pt-sensitized ZnO NRs film has demonstrated considerable gas sensitivity at 260ppm concentration of LPG. At 623K operating temperature, the maximum LPG response of 58% and the response time of 49sec for 1040ppm LPG concentration of Pt- sensitized ZnO NRs film are obtained. This higher LPG response of Pt-sensitized ZnO NRs film over pristine is primarily due to electronic effect and catalytic effect (spill-over effect) caused by an additional of Pt on ZnO NRs film surface.

Characterization of biocompatible NiCo2O4 nanoparticles for applications in hyperthermia and drug delivery.

Monodispersed, superparamagnetic nickel cobaltite (NCO) nanoparticles were functionalized using mercaptopropionic acid (MPA). MPA conjugates with NCO forming a metal-carboxylate linkage, with the MPA-MPA interaction occurring via formation of disulfide bonds, leaving another carboxyl end free for additional conjugation. The cytotoxicity studies on NCO-MPA show cell viability of ∼100% up to a dosage of 40 µg/mL on SiHa, MCF7, and B16F10 cell lines, and on mouse primary fibroblasts. Time-dependent cell viability studies done for a duration of 72 hours showed the cell lines' viability up to 80% for dosages as high as 80 µg/mL. Negligible leaching (<5 ppm) of ionic Co or Ni was noted into the delivery medium. Upon subjecting the NCO-MPA dispersion (0.1 mg/mL) to radiofrequency absorption, the nanoparticles were heated to 75°C within 2 minutes, suggesting its promise as a magnetic hyperthermia agent. Furthermore, the amino acid lysine and the drug cephalexin were successfully adducted to the NCO system, suggesting its potential for drug delivery. FROM THE CLINICAL EDITOR: NCO-MPA nanopartciles were found to be promising magnetic hyperthermia agents, suggesting potential future clinical applications.

Cerium doping and stoichiometry control for biomedical use of La0.7Sr0.3MnO3 nanoparticles: microwave absorption and cytotoxicity study.

La0.7Sr0.3MnO3 nanoparticles doped with cerium (La0.7-xCe(x)Sr0.3MnO3 where 0 < or = x < or = 0.7) as well as the La(1-y)Sr(y)MnO3 nanoparticles with different values of y (La/Sr ratio) are evaluated for cytotoxicity and heating application. Considering hyperthermia as one of the possible application domains of such materials, the cytotoxicity studies were done on human skin carcinoma and human fibrosarcoma cell lines. All the samples showed the desired heating effect when subjected to high-frequency exposure at 2.45 GHz. Cytotoxicity studies revealed extremely low cytotoxicity in Ce-doped samples as well as in samples with a reduced La/Sr ratio. A maximum percentage cell viability on exposure to these nanoparticles was 95% and 85% for the two groups of samples, respectively, with a dose of 20 microg/mL for the x = 0.4 sample. The issues of dopant solubility and nonstoichiometry are discussed.