What is the difference between nanorod and nanowire

It has a large excitonic binding energy of 60 MeV, which is greater than the thermal energy at room temperature, makes it a promising candidate for applications in blue-UV light emission and room-temperature UV lasing. ZnO posed an excellent chemical and thermal stability and the electrical properties. Single crystal of ZnO exhibit significantly faster electron transport and greater mobility. The faster electron transport is a result of the high electron diffusion coefficients, which will provide significant advantages to device performance [ 28 ].

Since ZnO could emits at the near ultraviolet, has transparent conductivity and piezoelectric properties, thus, ZnO is an interesting material for semiconductor and laser devices, piezoelectric transducers, transparent electronics, surface acoustic wave devices, spin functional devices, and gas sensing.

Overall, ZnO is an excellent material for sensor application attributed by its large surface to volume ratio that leads to the enhancement of it sensitivity, bio-safety and bio-compatibility.

A recent research has demonstrated that creation of highly oriented and ordered array of ZnO nanostructures has greatly stimulate interest in development of novel devices [ 29 ]. The large surface area of nanorods makes ZnO attractive for gas and chemical sensing. Recently, a great deal of attention has been focused on the study of synthesizing the ZnO nanorods via VLS method. In this case, gold Au nanoparticles are used as catalyst in order to promoting the ZnO nanorods formation.

Unfortunately, the are some apparent drawbacks in VLS growth technique. After saturated, Zn precipitates out from the droplet and further oxidized as ZnO nanorods grow. The other drawback from VLS growth method is that at the tips of ZnO nanorods there are always impurity particles that might be undesirable for fabrication. The synthesis temperature used generally mild reaction temperature and high purity of ZnO nanorods could formed. Apparently, the CVD process took place in a horizontal quartz tube placed in a rapid thermal furnace.

Figure 4 a shows a schematic illustration of the CVD furnace including a horizontal quartz tube of 1-in. A high-purity metallic granulated zinc Au nanoparticles are used as catalyst deposited on Chip B and C. The Au catalyst further formed liquid droplet and super saturated with Zn vapor. The nucleation growth of ZnO started with the arrival of oxygen gas. The ZnO will precipitate when the droplet reached a critical radius and continuously growth.

Typically, ZnO synthesis was synthesized follow several steps. Initially, the quartz tube evacuated to 10—2 Torr, follow by purged using Ag gas to maintain a 1 atm ambient. Finally, the oxygen gas O 2 mixed Ag was then flown through quartz tube forcing a precipitate to form.

As shown in Figure 4 c , shows prismatic hexagonal rods of ZnO grown area. The ZnO crystal continuously growth perpendicular from the surface on one single nanowires forming comb structure Figure 4 d.

Thick ZnO needle can be found at the outer edge Figure 4 e. With sufficient oxygen concentration, wires with larger diameter are grown. Schematic illustration of the a CVD system with a horizontal quartz tube placed in a furnace. The ZnO films or nanorods were deposited on p-type silicon with orientation. Mass flow controllers separately controlled the flow of Ar and O 2 gases and the gas flow ratio of Ar to O 2 was in the range of 1—2.

The deposition time was set to 10 min [ 30 ]. Recently, several studies have demonstrates the growth of ZnO nanorods could be achieved molecular beam epitaxy MBE. In MBE, the growth is performed under clean, low pressure condition and the reactants are very pure Zn metal and atomic O from a plasma generator [ 31 ].

In MBE system, the potential contamination is minimized [ 31 ]. The ZnO nanorods of reasonable quality could be deposited forming cored nanorod Figure 5 a and b. This cored nanorods could be produced using Mg-doping during MBE growth.

Similarly, Heo et al. The single ZnO nanorod growth is realized via nucleation on Ag films that are deposited on SiO 2 -terminated Si substrate surface Figure 5 c.

Particularly, chemical precursor solution involves in formation of ZnO nanorods via hydrothermal route is Zn salt and hexamethylenetetramine on Si substrates with a seed layer prepared from zinc acetate solution.

Polyethyleneimine was added to the solution to increase the nanorod aspect ratio [ 37 ]. It was discovered that the hexagonal ZnO nanorods formed about 2 mm in length — nm in diameter. This study also found that controlled growth of nanorods ranging from a thinner to a larger diameter can be realized by appropriate choice of the initial precursor concentration and deposition time.

The hexagonal ZnO nanorods formation via hydrothermal method also in agreement with Phromyothin findings Figure 6 d and e [ 38 ]. Similarly, this study also discovered that as the precursor concentration increased, the average diameter of ZnO nanorods will enlarge. It can be suggested that the precursor concentration provides the crucial role on the physical morphology and crystal growth direction of ZnO nanorods.

Last but not least, the ZnO nanorods also could be synthesized via ED method. ED method has many advantages including a low growth temperature, simple and low cost process without the need for vacuum systems for preparing ZnO nanorods with high crystallinity, being suited for scale-up and good electrical contact between the structures and the substrate [ 39 ].

ITO and FTO , electrodes and a previously deposited ZnO seed layer are necessary to precisely control the morphology and aspect ratio of the as-grown ZnO nanostructures. In ED method the ZnO nanorods were electrodeposited from the zinc nitride aqueous solution in an electrode system.

The ZnO nanorods exhibited good vertical alignment, and with significant hexagonal cross section and a relatively uniform size with an average diameter of nm. Much attention has been given recently to gold nanorods Au nanorods , mainly due to their applications in biomedicine. This last one is useful for medical applications because NIR radiation is the one that penetrates the most in living tissues.

The absorbed radiation is converted into heat, thus showing promise for cancer treatment. Also, these nanorods have localized surface plasmon resonances LSPRs that allow for unique scientific and technical applications [ 42 ]. In particular, the synthesis of well-defined size and shapes of Au nanorods has attracted much attention due to its importance in electronic and optical properties of these nanomaterials. The longitudinal bands of Au nanorods can be tuned by changing their aspect ratio, simultaneously make it possible to gain absorption bands at the desired wavelength in the NIR.

Small change in aspect ratio will result in drastic change in the NIR absorption wavelength. The Au nanorods could be synthesized via two general growth approaches, which are bottom-up and top-down methods. For bottom-up methods, Au nanorods are generated through nucleation in aqueous solutions and subsequent overgrowth, where Au salts are usually used to provide the Au source through reduction.

Particularly, bottom-up method including wet-chemical, electrochemical, sonochemical, solvothermal, microwave-assisted and photochemical reduction technique. All of these method involving the use of reduced aqueous solvated Au salts by various reducing agents, such as sodium borohydride, ascorbic acid, and small Au clusters, under different external stimuli triggering the reduction of Au salt.

The length of Au nanorods could be elongated with the use of template, it serves to confine the growth along one direction during the reduction. The electrochemical method was the first technique for developing the Au nanorods.

Briefly, the Au and Pt were used as the anode and cathode, respectively. These electrodes will be immersed in an electrolytic solution containing the cationic surfactant such as hexadecyltrimethylammonium bromide CTAB and co-surfactant.

The length of the nanorods is determined by the presence of a silver plate in the solution. The silver metals react with the Au ions generated by the dissolution of the anode. Based on previous literature for Au nanorods formation via bottom-up method, seed mediated growth has been by far the most efficient and popular approach [ 44 ]. Highly yield monodisperse Au nanorods with greater uniformity could be developed via this method. The seed solution will be mixed with growth solution containing metal salt weak reducing agent such as ascorbic acid and a surfactant-directing agent CTAB.

According to former study, the CTAB will bind to the crystallographic faces of Au existing along the sides of pentahedrally twinned rods, as compared to the faces at the tip. It have been reported that the size and shape of Au nanorods could be tailored by adjusting the growth condition such as the pH of growth solution, composition of surfactant, amount of the reagent, growth temperature and structure of the seed in the seed-mediated growth process.

Interestingly, recent study demonstrated high yield and greater uniformity of Au nanorods could be obtained via seed-mediated growth through the use of aromatic additive to CTAB [ 45 ]. Figure 7 a and c showed TEM images of Au nanorods synthesized with 0. The nanorods obtained have an average diameter of On the other hand, slightly longer nanorods are made when 0. Eventhough the bottom-up method results in excellent monodisperse Au nanorods with small diameter and high uniformity, yet them suffer some drawback where typically, selective placement of Au nanorods at desired locations on substrates by the bottom-up methods has been very difficult owing to the random nature of the reduction of Au ions and the deposition of Au atoms in reaction solutions.

Moreover, the shape and size of Au nanorods also varied from different synthesis batches. This will affect their optical and catalytic properties and applications. Last but not least, bottom-up method suffers in placing Au nanorods into large-area, ordered arrays. Due to these reasons, top-down approaches gained interest.

It is well-established that top-down method could promote high production homogeneous Au nanorods with controlled particle geometries and regular inter-particle arrangements, which is valuable for quantitative characterization as well as device applications. In top-down methods, Au nanorods are obtained through a combination of different physical lithography processes and Au deposition [ 42 ].

Particularly, there are two technique used for top-down method in synthesizing the Au nanorods. First method is through the removal of Au from predeposited Au films using ion beam or etching techniques. Second method is by employing the lithography techniques to create mask.

Au layer then deposited on the substrate which is covered by the mask via physical method: thermal, electron-beam evaporation or sputtering. The synthesized Au nanorods further obtained from lift-off process. Generally, the size of Au nanorods obtained via top-down method is limited by the resolution of lithography method. Nanorods are thicker in comparison to nanowires. Nanowires have diameters which are much smaller than their lengths. They can be considered one dimensional structures. Nanorods have much shorter length than nanowires and their diameters are greater than the wires.

So, they can not be always considered one dimensional structures as the nanowires. I already successfully synthesized the gold nanorods with AR L:D between 2. In order to create the nanowire with the similar method, what should I improve? Thanks Abdelhalim abdelnaby Zekry Anupma Thakur. Dear Immanuel Paulraj for more information about the difference between nanowires and nanorods please see this useful article entitled. The following article about ZnO nanowires and nanorods is freely available as public full text on RG:.

Can you explain more how how you build your nanowires and how could they destructed after long time? This means that after certain time a reverse reaction begins to dissolve the nanorods. So, either you have to take out the rods out of the solution and refresh it which means that you increase the concentration of the materials bearing the gold atoms and then bring them again to complete the deposition process.

In nanotechnology, nanorods are one morphology of nanoscale objects. Each of their dimensions range from 1— nm. They may be synthesized from metals or semiconducting materials. Standard aspect ratios length divided by width are Nanorods are produced by direct chemical synthesis. A combination of ligands act as shape control agents and bond to different facets of the nanorod with different strengths. This allows different faces of the nanorod to grow at different rates, producing an elongated object.

It can also be defined as the ratio of the length to width being greater than Alternatively, nanowires can be defined as structures that have a thickness or diameter constrained to tens of nanometers or less and an unconstrained length. At these scales, quantum mechanical effects are important — which coined the term "quantum wires". Many different types of nanowires exist, including superconducting e. YBCO , metallic e. Ni, Pt, Au.

Dear Dr. Abdelhalim Zekry, Thanks you for actively responding my question. Thank you. The discussion may feed the parents a way to manage and guide the children in a right direction. I have a protein that got recently diffracted at 1.

I am unable to do molecular replacement since my template model is from P3 spacegroup. I found this a weird phenomenon. Enter keywords to search for news articles: Submit.

Browse By. Explained: Nanowires and nanotubes. Tiny filaments and cylinders are studied for possible uses in energy, electronics, optics and other fields. David L.

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