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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.

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.

Hollow glass microsphere (HGM)/TiO₂ core-shell structural composites have promising applications in the field of energy efficient solar-reflective paints. In this work, after pretreated with saturated Ca(OH)₂ solutions, litchis-like TiO₂ shells have been successfully synthesized on HGMs via a controllably heterogeneous precipitation method with Titanium (IV) sulfate (Ti(SO${}_4{)}_2)$ and urea as reaction precursors. It is emphasized that the use of urea as the precipitating agent is essential for the heterogeneous nucleation and growth of Ti(OH)₄ on HGMs, while the Ca(OH)₂ pretreatment provides the heterogeneous nucleation sites on HGMs which promotes the nucleation and growth of Ti(OH)₄, and gives rise to large secondary Ti(OH)₄ particles, leading to the formation of litchis-like TiO₂ shells. The resulted core-shell structural HGM/TiO₂ microspheres exhibited highest solar reflectance of $\sim$83%.

The synthesis of aqueous MPA-capped CdTe quantum dots (QDs) via a facile one-pot route was developed. The particle size, optical properties and crystal structure of the as-synthesis QDs were investigated by transmission electron microscopy (TEM), Fourier transform infrared (FTIR), UV-vis absorption and photoluminescence (PL) spectra, respectively. Meanwhile, the effect of reaction conditions, including reaction time, pH and the quantity of sodium citrate (SC) on the growth of CdTe QDs were discussed. Then, the obtained CdTe QDs were successfully used for the detection of trace Cu${}^{2+}$ with high sensitivity and excellent selectivity. The fluorescence intensity of CdTe QDs with Cu${}^{2+}$ concentration showed a linear relationship in the range from $1\times 10^{-7}$ mol/L to $1\times 10^{-6}$mol/L. The correlation coefficient (R) is 0.9980 and limit of detection (LOD) is $1.0\times 10^{-8}$mol/L. Moreover, the concentration of Cu${}^{2+}$ in tap water samples was determined based on this sensing system and the recovery test was satisfactory.

Various metal (iron, copper, zinc, platinum)-based nanostructures were synthesized by a simple, green, and one-pot reaction of respective metal precursor and a cucurbit[7]uril (CB7) in an aqueous alkaline mixture at room temperature. The metal nanostructures (MNS) were obtained without adding any additional traditional reducing or protecting agents and/or external energy sources. Further, we could be able to tune the size and shape of the MNS just by varying the experimental conditions such as reaction concentration. Depending on the metal salts and reaction conditions, we could be able to produce different sizes and shapes of nanostructures. For example, the diameter of the CuO and iron nanoparticles (NP) was observed as $\sim 1$nm (even $<1$nm) which suggests the inclusion mechanism. However, the particle size of zinc and platinum was over 2nm which suggests the capping mechanism for the well-dispersed nanoparticles. It is worth mentioning that the CB7 acts as both reducing and protecting agent for the preparation of various MNS at ambient conditions. This one-pot and green approach for the preparation of MNS in aqueous solution has various advantages due to its mild synthesis condition and no toxic materials were used or produced, which is an important aspect for the exploration of biomedical applications and environmental influence of several metal nanoparticles that are presently prepared in organic solvents.

Graphene nanosheets have attracted immense research interest among the materials science community from electronics to the biomedical field. Being the first member of two-dimensional nanomaterials family, discovered in 2004 followed by the Nobel Prize winning in 2010, it is now readily witnessing global industrial revolutions. The nanomaterial is bestowed with such unprecedented features that can be tangible to a wide spectrum of applications ranging from energy storage devices to sensor application. Enormous flattened surfaces, superior mechanical strength and flexibility, ballistic intrinsic carrier mobility, nearly transparent nature, high thermal conductivity and room-temperature ferromagnetic behavior are few of the extraordinary attributes of the monolayer of carbon nanosheets. In this comprehensive review, an attempt has been put forward to precisely revisit and represent the literature available on the fundamental properties of graphene nanomaterials. Also, the usage of its characteristic features in various applications as well as synthesis process has been briefly discussed.

In this work, the function of 4-nitroimidazole (4-NIm) in the formation of Cr-MIL-101 was confirmed. It was found that 4-NIm is an effective additive in the formation of Cr-MIL-101 synthesized at lower temperature. The investigation of crystallization time showed that 4-NIm can prevent Cr-MIL-101 phase converting into Cr-MIL-53 phase. The effect of concentration of 4-NIm on the morphology and the yield of Cr-MIL-101 may therefore be explained by increasing the nucleation rate. The investigation of crystallization temperature revealed that 4-NIm changes the synthesis temperature range of Cr-MIL-101 into 423–463 K. The assistant function of 4-NIm was played through interaction with H${}^{+}$ and NO${}^{3-}$ in the synthesis system, which may lead to enhancement of the deprotonation of H₂BDC.

In this paper, various research works have been performed on synthesis and functionalization after the invention of graphene (Gr) and its spectral properties. The reinforcing of Gr family members into the matrix leads to the development of novel composites. Its characterization in terms of morphological and physicochemical properties is required for the discovery of wide-ranging applications. This paper reviews the various emerging features and future scope for reduced graphene oxide (rGO). The possibilities of composites development through the different matrix are proposed to evaluate application potential, various fabrication techniques for Gr, and its role in improving composite properties. The work initially examines multiple ways to synthesize rGO. Its addition to different materials includes metals, metal oxides, ceramics, polymers, and organic compounds through various composite preparation techniques. Finally, this paper gives an overview of the enhancement in properties obtained due to the addition of rGO, which opens the door for a broad set of applications. This paper concludes with a comparative study that defines a suitable preparation technique according to the required material composites, desired properties, and specific applications. An attempt has been proposed to examine the exceptional feature of rGO/composite for cost-effective functions in manufacturing sectors.

g–C₃N₄ nanosheets were first synthesized by calcining the mixture of hydrochloric acid-pretreated melamine and ammonium chloride. Then, by the aiding of solvothermal method and hydrofluoric acid as morphology modifier, 001-TiO₂/g–C₃N₄ (TCN-X, $X=5$, 3, 2, 1) nanocomposites were synthesized using g–C₃N₄ nanosheets and tetrabutyl titanate, with the mass ratio of g–C₃N₄ to TiO₂ was 5:1, 3:1, 2:1 and 1:1, respectively. The as-synthesized samples were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscopy, Fourier transform infrared spectroscopy, nitrogen adsorption–desorption method, ultraviolet–visible diffuse reflectance spectrum, photoluminescence spectrum, etc. Their photocatalytic properties were evaluated under visible light irradiation with rhodamine B (RhB) as the target pollutant. The results reveal that the TCN-3 composites had a large specific surface area of 67.38m²/g and consisted of g–C₃N₄ nanosheets and anatase TiO₂ crystals about 10–20nm in size. The (001) crystal planes of TiO₂ can be easily observed in TCN-X composites. All TiO₂/g–C₃N₄ composites exhibited excellent photocatalytic activity compared with the pure g–C₃N₄ did. The photocatalytic property of TCN-X samples varied with the mass ratio of g–C₃N₄to TiO₂, and TCN-3 presented the optimum photocatalytic performance. In total, 50mg of TCN-3 completely degraded 50mL and 100mL of RhB solution (10mg/L) in 15min and 40min, respectively. The reaction rate constant of TCN-3 was 6.7 times as large as that of pure g–C₃N₄. TCN-3 also presented outstanding activity for the photocatalytic degradation of the colorless tetracycline solution. The significant improvement in photocatalytic activity of TCN-3 was attributed to the evenly distribution of TiO₂ on g–C₃N₄, the enhanced specific surface area and the construction of 001-TiO₂/g–C₃N₄ heterojunction between the g–C₃N₄ nanosheets and the (001) crystal planes of anatase TiO₂, which greatly reduced the recombination rate of the photo-generated electron and hole.

Natural catalysts used in the synthesis of carbon nanotubes have significant cost advantages due to their huge reserves, but natural minerals often require complicated pretreatments to obtain satisfactory products. In this study, red sandstone was directly used as a catalyst for the synthesis of multi-carbon nanotubes by chemical vapor deposition without complicated pretreatment. The SEM, TEM, Raman and TG characterization of the products at different growth temperatures ($600^{\circ }$C, $700^{\circ }$C and $800^{\circ }$C) showed that $700^{\circ }$C is the optimal condition for the growth of multi-walled carbon nanotubes (MWCNTs) by red sandstone. High-quality multi-wall carbon nanotubes can be obtained with a relatively high yield, and the $I_G∕I_D$ of the product reaches 1.78, which exceeds that of many commercial multi-wall carbon nanotubes. Compared with other natural materials as catalysts for the synthesis of MWCNTs, red sandstone has a huge cost advantage because it can catalyze the synthesis of high-quality MWCNTs at $700^{\circ }$C without complicated pretreatment.

The advanced two-stage synthesis method of the Ni–Co–Cu/carbon magnetic nanocomposite as promising material for electromagnetic wave absorption was proposed. Synthesis condition for consolidated Ni–Co–Cu solid solution nanoparticles with an average size of less than 100nm uniformly distributed in the carbon matrix was discussed. The effect of different pyrolysis temperatures (500–700^∘C) and Cu concentration in the precursor (from 5 to 30wt.%) on the microstructure of Ni–Co–Cu nanocomposite, its particle size and magnetic properties was investigated by of XRD, TEM and magnetic hysteresis.

The saturation magnetization and remanence showed non-monotonic dependences on Cu concentration in samples. The coercive force was varied from 110 to 177Oe depending on Cu content in nanoparticles. The correlation between magnetic properties and microstructure of Ni–Co–Cu/carbon nanocomposites was discussed assuming the transition of nanoparticles to superparamagnetic and single-domain states depending on their sizes.