[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Nanotechnology is emerging as an important area of research with its tremendous applications in all fields of science, engineering, medicine, pharmacy, etc. It involves the materials and their applications having one dimension in the range of 1-100nm. Generally, various techniques are used for syntheses of nanoparticles (NPs) viz. laser ablation, chemical reduction, milling, sputtering, etc. These conventional techniques e.g. chemical reduction method, in which various hazardous chemicals are used for the synthesis of NPs later become liable for innumerable health risks due to their toxicity and endangering serious concerns for environment, while other approaches are expensive, need high energy for the synthesis of NPs. However, biogenic synthesis method to produce NPs is eco-friendly and free of chemical contaminants for biological applications where purity is of concerns. In biological method, different biological entities such as extract, enzymes or proteins of a natural product are used to reduce and stabilised formation of NPs. The nature of these biological entities also influence the structure, shape, size and morphology of synthesized NPs. In this review, biogenic synthesis of zinc oxide (ZnO) NPs, procedures of syntheses, mechanism of formation and their various applications have been discussed. Various entities such as proteins, enzymes, phytochemicals, etc. available in the natural reductants are responsible for synthesis of ZnO NPs.

A review on biogenic synthesis of ZnO nanoparticles using plant extracts and microbes: A prospect towards green chemistry.

Extensive calculations based on density functional theory have been carried out to understand the origin of magnetism in undoped ZnO thin films as found in recent experiments. The observed magnetism is confirmed to be due to Zn, instead of O, vacancy. The main source of the magnetic moment, however, arises from the unpaired 2p electrons at O sites surrounding the Zn vacancy with each nearest-neighbor O atom carrying a magnetic moment ranging from 0.490 to 0.740 B. Moreover, the study of vacancy-vacancy interactions indicates that in the ground state, the magnetic moments induced by Zn vacancies prefer to ferromagnetically couple with the antiferromagnetic state lying 44 meV higher in energy. Since this is larger than the thermal energy at room temperature, the ferromagnetic state can be stable against thermal fluctuations. Calculations and discussions are also extended to ZnO nanowires that have larger surface to volume ratio. Here, the Zn vacancies are found to lead to the ferromagnetic state too. The present theoretical study not only demonstrates that ZnO samples can be magnetic even without transition-metal doping but also suggests that introducing Zn vacancy is a natural and an effective way to fabricate magnetic ZnO nanostructures. In addition, vacancy mediated magnetic ZnO nanostructures may have certain advantages over transition-metal doped systems in biomedical applications.

https://absimage.aps.org/image/MAR08/MWS_MAR08-2007-004197.pdf

Zinc Vacancy induced magnetism in ZnO thin films and nanowires

Metallic and metal oxide nanoparticles (NPs), including titanium dioxide NPs, among polymeric NPs, liposomes, micelles, quantum dots, dendrimers, or fullerenes, are becoming more and more important due to their potential use in novel medical therapies. Titanium dioxide (titanium(IV) oxide, titania, TiO2) is an inorganic compound that owes its recent rise in scientific interest to photoactivity. After the illumination in aqueous media with UV light, TiO2 produces an array of reactive oxygen species (ROS). The capability to produce ROS and thus induce cell death has found application in the photodynamic therapy (PDT) for the treatment of a wide range of maladies, from psoriasis to cancer. Titanium dioxide NPs were studied as photosensitizing agents in the treatment of malignant tumors as well as in photodynamic inactivation of antibiotic-resistant bacteria. Both TiO2 NPs themselves, as well as their composites and combinations with other molecules or biomolecules, can be successfully used as photosensitizers in PDT. Moreover, various organic compounds can be grafted on TiO2 nanoparticles, leading to hybrid materials. These nanostructures can reveal increased light absorption, allowing their further use in targeted therapy in medicine. In order to improve efficient anticancer and antimicrobial therapies, many approaches utilizing titanium dioxide were tested. Results of selected studies presenting the scope of potential uses are discussed in this review.

https://www.mdpi.com/2079-4991/10/2/387/pdf

Titanium Dioxide Nanoparticles: Prospects and Applications in Medicine.

This study aims to provide an updated survey of the main synthesis methods of copper oxide (CuO) nanoparticles in order to obtain tailored nanosystems for various biomedical applications. The synthesis approach significantly impacts the properties of such nanoparticles and these properties in turn have a significant impact on their biomedical applications. Although not widely investigated as an efficient drug delivery system, CuO nanoparticles have great biological properties including effective antimicrobial action against a wide range of pathogens and also drug resistant bacteria. These properties have led to the development of various approaches with direct applications to the biomedical field, such as tailored surfaces with antimicrobial effect, wound dressings and modified textiles. It is also believed that these nanosystems could represent efficient alternatives in the development of smart systems utilized both for the detection of pathogens and for the treatment of infections.

https://www.mdpi.com/1424-8247/9/4/75/pdf

Methods of Synthesis, Properties and Biomedical Applications of CuO Nanoparticles.

Copper oxide nanoparticles were successfully prepared by a sol–gel technique. An aqueous solution of copper nitrate Cu(NO3)2 and acetic acid was used as precursor. On addition of sodium hydroxide (NaOH) a precipitate of copper oxide was immediately formed. The copper oxide nanoparticles were characterized by use of x-ray diffractometry (XRD), thermogravimetric analysis (TGA), differential thermal analysis, differential scanning calorimetry, Fourier-transform infrared spectroscopy (FTIR), vibrating sample magnetometry, and scanning electron microscopy (SEM). The XRD pattern contained sharp peaks of copper oxide nanoparticles with mixed cuprite and tenorite phases. Use of the Debye–Scherer equation showed that the crystallite size of the copper oxide nanoparticles increased with increasing annealing temperature. FTIR spectra revealed vibration of the CuO band at 473 cm−1; a band at 624 cm−1 was attributed to Cu2O. Maximum coercivity and saturation magnetization of the nanoparticles were 276 Oe and 0.034 emu/g, respectively. SEM micrographs of the nanoparticles revealed the presence of spherical nanoparticles of the tenorite phase whereas the cuprite phase was in the form of a compact deposit.

Characterization of Copper Oxide Nanoparticles Fabricated by the Sol–Gel Method

ZnO nanoparticles have been synthesized by sol–gel technique using zinc acetate dihydrate and diethanolamine as the precursor materials. The effects of calcination temperatures, i.e., 300, 500, 650, 700, and 750 °C, on the crystallinity, optical properties, and size of fabricated zinc oxide nanoparticles were investigated. X-ray diffraction (XRD) analysis reveals the hexagonal wurtzite structure. Crystallite size estimated by XRD data is about 20 nm and increased by increasing calcination temperature. Particle size was supported by particle size analyzer. Fourier transform infrared spectroscopy was used to classify molecular species through thermal decomposition. Its spectra show the ZnO nanoparticles formation in the wave number range 400–500 cm−1 while bonding was eliminated by heating process. Differential scanning calorimetry–thermal gravimetric analysis/differential thermal analysis curves indicate weight loss by thermal effect. Precursor decomposes at ~250 °C and mass loss took place from 100 to 500 °C. Ultraviolet–visible (UV–Vis) absorption was utilized to analyze the optical properties of samples. It is seen that the band gap value shows only very slight increase with increasing calcination temperature. Best band gap of 3.08 eV was measured for the sample prepared without calcination.

Effect of calcination temperature on the properties of ZnO nanoparticles

Photocatalytic, antibacterial, optical and magnetic properties of Fe-doped ZnO nano-particles prepared by sol-gel

Abstract ZnO thin films were deposited on a glass substrate by dip coating technique using a solution of zinc acetate, ethanol and distilled water. Optical constants, such as refractive index n and extinction coefficient k. were determined from transmittance spectrum in the ultraviolet-visible-near infrared (UV-Vis-NIR) regions using envelope methods. The films were found to exhibit high transmittance, low absorbance and low reflectance in the visible regions. Absorption coefficient α and the thickness of the film t were calculated from interference of transmittance spectra. The direct optical band gap of the films was in the range of 3.98 to 3.54 eV and the thickness of the films was evaluated in the range of 173 to 323 nm, while the refractive index slightly varied in the range of 1.515 to 1.622 with an increase in withdrawal speed from 100 to 250 mm/s. The crystallographic structure of the films was analyzed with X-ray diffractometer. The films were amorphous in nature.

/pdf/fabrication-and-properties-of-zinc-oxide-thin-film-prepared-5f520tewgd.pdf

Fabrication and properties of zinc oxide thin film prepared by sol-gel dip coating method

Fe 2
O
 3
 nanoparticles are synthesized chemically by sol-gel method. The nanoparticles have been characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), thermo gravimetric analysis/differential thermal analysis-differential scanning calorimetry (TGA/DTA-DSC), and vibrating sample magnetometer (VSM). XRD results identify hematite phase of iron oxide nanoparticles. The average crystalline size of the nanoparticles increased from 34 to 36.7 nm when the annealing temperature increased from 400 °C to 1000 °C. FTIR technique also confirmed XRD results. Phase transformation temperatures were determined by DSC-TGA. The exothermic peak at 720.2 °C is attributed to the phase change from y Fe 2
O
 3
 (low temperature phase) to α Fe 2
O
 3
 (high temperature phase). The annealing temperature also affects the optical properties since the measured band gap increased from 2.4 to 2.7 eV when the annealing temperature increased from 400 to 1000 °C.

Zohra Nazir Kayani

Papers

Characterization of Copper Oxide Nanoparticles Fabricated by the Sol–Gel Method

Effect of calcination temperature on the properties of ZnO nanoparticles

Photocatalytic, antibacterial, optical and magnetic properties of Fe-doped ZnO nano-particles prepared by sol-gel

Fabrication and properties of zinc oxide thin film prepared by sol-gel dip coating method

Synthesis of Iron Oxide Nanoparticles by Sol–Gel Technique and Their Characterization