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Nanodiamonds (NDs) have unique optical and mechanical characteristics, surface chemistry, extensive surface area and biocompatibility, and they are nontoxic, rendering them suitable for a diverse range of applications. Recently, NDs have received significant attention in nano-biomedical engineering. This review discusses the recent advancement of NDs’ biomedical engineering, historical background, basic introduction to nanoparticles and development. We summarize NDs’ synthesis technique, properties and applications. Two methodologies are used in ND synthesis: bottom-up and top-down. We cover synthesis methods, including detonation, ball milling, laser ablation, chemical vapor deposition (CVD) and high pressure and high temperature (HPHT); discuss the properties of NDs, such as fluorescence and biocompatibility. Due to these properties, NDs have potential applications in biomedical engineering, including bioimaging, biosensing, drug delivery, tissue engineering and protein mimics. Further, it provides an outlook for future progress, development and application of NDs in biological and biomedical areas.

The WC–Co nanocomposites were synthesized by using a polymer precursor such as polyacrylonitrile, which severs as an in situ carbon source. The WC–Co nanocomposites formed are characterized by X-ray diffraction and electron microscopy. Nearly pure WC–Co nanocomposites with a particle size in the range of 60–80 nm have been obtained. The use of H₂ atmosphere enhanced the carbide formation and in turn reduced the reaction time (at high temperature). The phase purity of the products is strongly influenced by the processing conditions such as the firing temperature, time and atmosphere. This suggests that the process parameters have to be optimized before scaling up the process for commercial production.

We report a novel method to synthesize multiwalled carbon nanotubes (MWNTs) in large scale at 470°C. TEM and Roman spectra analysis show that dominating graphite crystalline coexists with amorphous carbon in MWNTs. XRD and TGA results suggest that fcc cobalt plays a catalytic role in the growth process of MWNTs, which exists and stable inside the carbon layers of MWNTs. The synthesis method is simple and can easily ensure adequate stability and reproducibility. Therefore the method is possibly suited to industrialized synthesizing process of MWNTs due to these advantages.

Single-sided ZnO nanocombs have been synthesized by thermal evaporation of Zn powders at 440°C through a vapor–solid (VS) process. The stem ribbon of the as-synthesized nanocomb takes a growth direction of , and its top/bottom surfaces are . The nanoteeth grow epitaxially out of the stem ribbon along [0001]. Such a low temperature process may be useful in future device fabrication.

The magnetic properties of nanocrystalline powders of Ni_0.5Zn_0.5Fe₂O₄, synthesized at low temperatures, by a combustion method, have been investigated. Different powders containing crystallites of comparable average size, obtained by varying the synthesis conditions, show a large difference in the superparamagnetic blocking temperature due to the wide difference in the size distribution. The ferrite nanoparticles show large Curie temperature enhancement up to ~ 100 K, when compared to that of the bulk.

The present study elucidates the synthesis of magnesium ferrite magnetic nanocrystallites via hydroxylation–condensation reaction followed by an auto-combustion process. Nanocrystallites with diameter of 3–7 nm were successfully formed via this method. The ignition temperature of the redox reaction was apparently improved to 200°C by the modification of the pH of the metal aqueous solution. The crystallite size was altered by varying the hydrolysis parameters. The XRD analysis of the as-synthesized powder confirms the formation of a single-phase MgFe₂O₄ spinel structure. Importantly, the crystalline particles were obtained at low temperature without further calcination. The thermodynamic behavior of the precursor was characterized by DTA-TG. TEM observations showed the morphology and crystal structure of the nanocrystallites.

Nanosized metal hydroxides are synthesized in the presence of Poly(vinyl alcohol). Polymer controls the size and growth of the nanometal hydroxides. PVA-assisted synthesis of metal hydroxides is characterized by FTIR, XRD, TGA, and HRTEM methods. This method of synthesis is an eco-friendly and economically viable method.

Here, we report single step synthesis of hydrophobic and hydrophilic Fe₃O₄, ZnO, CoO and Y₂O₃:Eu nanoparticles via thermal decomposition of different organometallic complexes in oleylamine (OM) and tri(ethyleneglycol) (TREG) media, respectively. The crystal structure of the as-prepared nanoparticles is identified using X-ray diffraction, Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Morphology of the nanoparticles is determined by transmission electron microscopy (TEM) while the magnetic properties are measured using vibrating sample magnetometer (VSM). Thermolysis of appropriate precursors in OM and TREG medium are very capable of producing the highly dispresed hydrophobic and hydrophilic nanoparticles with diverse morphologies.

Ferromagnetic nanoparticles when dispersed in a dielectric ceramic matrix offer a new series of percolation composites with a metal-semiconductor or insulator interface that tailors the functional properties. In this purview, ZrO₂ of a high dielectric constant (ε_r) is stabilized in a cubic (c) polymorph by incorporating CrO₂ of strongly ferromagnetic nanoparticles. A selective composition 20CrO₂–80ZrO₂ is synthesized after heating a polymer precursor with glycerol at 500°C–800°C in air for 2 h. Broadening of X-ray diffraction peaks reveals Cr⁴⁺:c-ZrO₂ with an average crystallite size 5 nm in the 500°C heated sample and that is grown to 8 nm on increasing the temperature to 800°C. They occur as bundles of thin platelets in electron microscopic images. Both the samples have ferromagnetic hysteresis loops with 794 and 211 Oe of coercivities, respectively. Variations of ε_r-value and the power loss are studied as a function of frequency f (50 Hz–100 kHz range) on cold-pressed pellets at selective temperatures, in the 30°C–500°C range, in describing the effects of the magnetic species.

Nanosized manganese oxide was synthesized with help of ultrasound and its polymer nanocomposite with poly (vinyl alcohol) was prepared. The incorporated nanosized manganese oxide is involved in the surface catalytic effect on PVA matrix. Nanosized manganese oxide and its polymer composite were characterized by FTIR, XRD, DSC, TGA, SEM and HRTEM methods. This PVA-Mn₃O₄ nanocomposite system has improved thermally resistant than pristine PVA.

The Turkevich method is the oldest and most widely employed protocol for the production of colloidal gold. Gold nanoparticles are nontoxic in nature and have potential applications in various biomedical fields including drug delivery and bioimaging. These metallic nanoparticles can be functionalized with drugs, targeting ligands such as tumor necrosis factor and groups (e.g., Poly ethylene glycol) to provide shielding from undesired immune responses. In this study we investigate the influence of process variables on the synthesis of nanoparticles by the reduction of chloroauric acid (HAuCl₄) solution with sodium citrate. A design of experiment (DoE) approach was used to investigate the influence of production volume, temperature, stirring rate and sodium citrate concentration on the physical properties of the nanoparticles namely size, size distribution, zeta potential and UV-Vis characteristics. The study showed that the relative amount of sodium citrate added (Au/citrate mole ratio) had a significant effect on the size, poly dispersity index (PDI), the number of peaks in the size distribution and the position of Lambda max in the UV-Vis spectra. By varying the Au/Citrate ratio it is possible to synthesize particles with average diameters from 20 to 80 nm. However, the use of low amounts of sodium citrate in order to produce particles larger than ~35 nm tends to result in a wide bimodal size distribution.

Copper nanoparticles received much attention due to its high electrical conductivity, high melting point, low electrochemical migration behavior and low cost. Top down (physical methods) and bottom up (chemical and biological) approaches adopted for the synthesis of copper nanoparticles are reported. The property of copper nanoparticles mainly depends on the synthesis route and their process parameters. The influence of process parameters on the morphology, growth and yield of the nanoparticles by adopting various synthesis methods are discussed in detail. From the earlier reports, it is proved that electrochemical and chemical reduction method have received much higher attention due to their simple operation, low cost, faster reaction rate, high yield, environment friendly and low energy consumption. The characterization techniques, advantages and limitations of each synthesis methods are also discussed. The extensive applications of copper nanoparticles in various fields are also highlighted.

Lithium titanate nanorods have been synthesized via the hydrothermal process using lithium acetate, titanium butoxide and ethylenediamine as raw materials. X-ray diffraction (XRD) analysis shows that lithium titanate nanorods are composed of orthorhombic Li₂Ti₃O₇ phase. Scanning electron microscopy (SEM) shows that the diameter and the length of lithium titanate nanorods are about 40–150 nm and 1 μm, respectively. UV-Vis diffuse reflectance spectrum indicates that the bandgap of the lithium titanate nanorods is 3.63 eV. Ethylenediamine plays an essential role in the formation of lithium titanate nanorods. Ethylenediamine-assisted nucleation and crystalline growth process have been proposed to explain the formation and growth of lithium titanate nanorods. Photocatalytic degradation of methylene blue (MB) dye over the lithium titanate nanorods has been investigated under UV-Vis light irradiation. MB solution with the initial concentration of 2.5 mgL^-1 can be degraded totally using 10 mg lithium titanate nanorods in 10 mL MB solution.

This article presents a brief review of the recent research progresses achieved in the field of one-dimensional (1D) aluminum nitride (AlN) nanostructures. It mainly covers three aspects: The first one is to introduce the synthetic strategies for several classic 1D AlN nanostructures (such as nanofibers, nanobelts, nanorods, nanowires, nanotips, etc.) including template-confined reaction, arc discharge, catalyst-assisted growth, and vapor transport and related growth methods. The second is to elaborate some special physical properties, such as field emission and photoluminescence, which associate with the uniqueness of 1D AlN nanostructures. It is revealed that aligned AlN 1D nanostructures have low turn-on and threshold voltages, high emission current and small current fluctuation, and that the photoluminescence of AlN nanobelts are different from those of conventional AlN material. The third is to briefly illustrate the potential application of these 1D AlN nanostructures in composite materials. It is found that AlN nanowire is a good reinforcement for improving the mechanical and thermal properties of metal matrix composites, which can be expected to be utilized as packaging material with high strength and low thermal expansion. Finally, we summarize the major challenges in this field. Among them, a thorough understanding of the growth mechanism of 1D AlN nanostructures is the most important issue, and more precisely controlled growth is required to obtain tailored AlN nanostructures according to device applications.

Nano-Mg(OH)₂ was synthesized by co-precipitation method. Peaks between 500 and 1250 cm^-1 in FTIR spectroscopy confirmed the presence of metal hydroxide stretching. TGA inferred that above 600°C, 50% of residue weight remained. HRTEM of nanocomposite gave an idea about the nonspherical morphology of particles of size 25 nm to 30 nm. SEM inferred that flower-like morphology for pristine Mg(OH)₂ and higher % weight of aniline-intercalated Mg(OH)₂ had agglomerated structure. UV visible spectrum inferred the presence of Mg²⁺ ion at 275 nm and the presence of amino-group-intercalated Mg(OH)₂, which had a sharp peak at 193 nm and the intensity of which increases with the increase in % weight of aniline. PL inferred that aniline-intercalated Mg(OH)₂ showed a lower intensity of which increased with higher wavelength value than the pristine and nanocomposite with PVA.

Cadmium sulphide (CdS) nanocrystallites were prepared by sulphuration route with capping in polyethylene oxide (PEO) polymer matrix. It is found that PEO could provide a confined environment for particle nucleation and growth of CdS nanocrystallites. The scanning electron microscopy (SEM) with energy dispersive analysis by X-ray (EDAX) studies confirms the presence of CdS nanocrystallites in polymer matrix. X-ray diffraction (XRD) studies and transmission electron microscopy (TEM) selected area diffraction (SAD) patterns show that these crystallites have hexagonal structure. The TEM and UV-Visible absorption studies indicate uniform size distribution having size around 2.3 nm and band gap of 2.7 eV. X-ray photoelectron spectroscopy (XPS) studies reveal that core level energy positions of the Cd is shifted towards the lower binding energy and has similar chemical environment to that of bulk CdS.

The yttria-stabilized zirconia (YSZ) nanocrystals with uniform size, high purity, and high degree of crystallinity, were prepared by ultrasonic–microwave-assisted method. The structure, optical properties and morphologies of YSZ nanocrystals were characterized by X-ray powder diffraction (XRD), Raman spectroscopy, UV–vis absorption, scanning electron microscope (SEM) and transmission electron microscopy (TEM). The SEM and TEM images of the YSZ nanocrystals indicate that the product is a mono-dispersion structure with an average particle size of about 25 nm.

Lithium fluoride (LiF) nanopowders were prepared by trifluoroacetate-based sol–gel processing. In this work, lithium acetate dehydrate (LiAc ⋅ 2H₂O) and trifluoroacetic acid (TFA) was used as lithium and fluorine sources. The thermal behavior of initial gel was examined using differential thermal analysis (DTA). Effects of solvent (glacial acetic acid, absolute ethanol, and ethylene glycol), Li⁺ concentration (0.5, 1, and 2 mol/l) and decomposition temperature (200, 250, and 300°C) on synthesis of LiF nanopowders by sol–gel method were investigated. The results of LPSA, FE-SEM, and XRD showed that the growth of particles and aggregation can be controlled by changing above parameters. However, it is indicated that optimum conditions are; solvent as ethanol, Li ion concentration (0.5 mol/l), and decomposition temperature (300°C), respectively. Also, the addition of oleic acid as an organic additive made the final LiF particles finer and about 70–90 nm.

Various methods for the synthesis of copper nanoparticles employing chemical, physical and biological techniques considering bottom-up and top-down methods synthesis have been studied. The properties of copper nanoparticles depend largely on their synthesis procedures. The results from various investigations performed by different scientists using these methods have been summarized. The applications, characterization techniques, advantages and disadvantages of each synthesis method are also the point of discussion. A detailed study of the results reveals that chemical reduction methods are most suitable for the synthesis of copper nanoparticles. Chemical reduction of copper salts using ascorbic acid (Vitamin C) is a new and green approach in which ascorbic acid is used both as the reduction and capping agent. This approach is the most effective and is also economical. Wide applications have been reported in various fields, including heat transfer, catalyst production, electronics and medicine at a commercial scale. This process is nontoxic, environment-friendly and economical. The applications, characterization techniques, advantages and disadvantages of each synthesis method have been presented.

In this work manganese dioxide (Ramsdellite-MnO₂) was synthesized at room temperature using a facile electrochemical method. X-ray diffraction (XRD) was used to identify the type and the size of the crystal particle, while field emission scanning electron microscopy (FESEM) and energy filtered transmission electron microscopy (EFTEM) were used to show and identify the morphology of the particles and changes of their morphologies with the increase of reaction times. Fourier transform infrared (FTIR) spectroscopy confirmed the Mn–O bond. Results from XRD showed that optimum time for synthesis Ramsdellite-MnO₂ was 9 h. The results of EFTEM showed a mixture of nanospheres and nanorods after 9 h reaction time while a homogenous morphology of nanospheres was detected at 12 h reaction time. Results confirmed on the existence of a correlation between the reaction time and the resulting nanostructures. Moreover, the EFTEM result showed that average particle size for 12 h was (25 ± 7 nm). The variation of calculated specific capacitance (F/g) versus the different scan rate has indicated that the efficiency of synthesized Ramsdellite-MnO₂ nanostructures in 12 h reaction time was superior to 9 h.