Introduction:

A new family of two dimensional (2D) carbides, carbonitrides and nitrides – labeled MXenes – was discovered. Since then the number of papers on these materials has increased exponentially for several reasons amongst them: their hydrophilic nature, excellent electronic conductivities and ease of synthesizing large quantities in water. This unique combination of properties and ease of processing has positioned them as enabling materials for a large, and quite varied, host of applications from energy storage to electromagnetic shielding, transparent conductive electrodes, electrocatalysis, to name a few. Since the initial synthesis of Ti3C2 in hydrofluoric acid, many more compositions were discovered, and different synthesis pathways were explored. Most of the work done so far has been conducted on top-down synthesis where a layered parent compound is etched and then exfoliated. Three bottom-up synthesis methods, chemical vapor deposition, a template method and plasma enhanced pulsed laser deposition have been reported. The latter methods enable the synthesis of not only high-quality ultrathin 2D transition metal carbide and nitride films, but also those that could not be synthesized by selective etching. This article reviews and summarizes the most important breakthroughs in the synthesis of MXenes and high-quality ultrathin 2D transition metal carbide and nitride films.

In particular, it is easy for MXenes to form composites with other materials such as polymers, oxides, and carbon nanotubes, which further provides an effective way to tune the properties of MXenes for various applications. Not only have MXenes and MXene-based composites come into prominence as electrode materials in the energy storage field as is widely known, but they have also shown great potential in environment-related applications including electro/photocatalytic water splitting, photocatalytic reduction of carbon dioxide, water purification and sensors, thanks to their high conductivity, reducibility and biocompatibility. In this review, we summarize the synthesis and properties of MXenes and MXene-based composites and highlight their recent advances in environment-related applications. Challenges and perspectives for future research are also outlined.

Properties:

While MAX phases are stiff, they will be machined as easily as some metals. They can all be machined manually employing a hacksaw, despite the very fact that a number of them are 3 times as stiff as titanium metal, with an equivalent density as titanium.

Applications:

Ti3SiC2, Ti3AlC2, Ti2AlN, and Ti4AlN3 are well-known members of this family. To examine the feasibility of these compounds in high-temperature applications, it is important to test their high temperature stability.

Certain compositions possess good irradiation and thermal shock resistance, along with good machinability, and are being considered as structural and functional materials for Gen IV nuclear

reactor component

MXenes, as conductive layered materials with tunable surface terminations, have been shown to be promising for energy storage applications (Li-ion batteries and supercapacitors), composites, photocatalysis,water purification,gas sensors,transparent conducting electrodes,neural electrodes,as a metamaterial,SERS substrate,photonic diode,electrochromic device,and triboelectric nanogenerator (TENGs),to name a few.

Lithium-ion batteries (LIBs)

Some MXenes have been investigated experimentally thus far in LIBs (e.g. V2CTx, Nb2CTx, Ti2CTx, and Ti3C2Tx. V2CTx has demonstrated the highest reversible charge storage capacity among MXenes in multi-layer form (280 mAhg−1 at 1C rate and 125 mAhg−1 at 10C rate). Nb2CTx in multi-layer form showed a stable, reversible capacity of 170 mAhg−1 at 1C rate and 110 mAhg−1 at a 10C rate. Although Ti3C2Tx shows the lowest capacity among the four MXenes in multi-layer form, it can be easily delaminated via sonication of the multi-layer powder. By virtue of higher electrochemically active and accessible surface area, delaminated Ti3C2Tx paper demonstrates a reversible capacity of 410 mAhg−1 at 1C and 110 mAhg−1 at 36C rate. As a general trend, M2X MXenes can be expected to have greater capacity than their M3X2 or M4X3 counterparts at the same applied current, since M2X MXenes have the fewest atomic layers per sheet.

In addition to the high power capabilities of MXenes, each MXene has a different active voltage window, which could allow their use as cathodes or anodes in batteries. Moreover, the experimentally measured capacity for Ti3C2Tx paper is higher than predicted from computer simulations, indicating that further investigation is required to ascertain the charge storage mechanism on MXene surfaces.

Sodium-ion batteries

MXenes also exhibit promising performances for sodium-based energy storage devices. Na+ should diffuse rapidly on MXene surfaces, which is favourable for fast charging/discharging. Two layers of Na+ can be intercalated in between MXene layers. As a typical example, multi-layered Ti2CTx MXene as a negative electrode material showed a capacity of 175 mA h g−1 and good rate capability for electrochemical sodium-ion storage. It is possible to tune the Na-ion insertion potentials of MXenes by changing the transition metal and surface functional groups. V2CTx MXene has been successfully applied as a positive electrode material for sodium-ion storage. Porous MXene-based paper electrodes have also been reported, which exhibited high volumetric capacities and stable cycling performance, demonstrating that MXenes are promising for sodium-based energy storage devices where size matters.

Super capacitors

Super capacitor electrodes based on Ti3C2 MXene paper in aqueous solutions demonstrate excellent cyclability and the ability to store 300-400 F/cm3, which translates to three times as much energy as for activated carbon and graphene-based capacitors. Ti3C2 MXene clay shows a volumetric capacitance of 900 F/cm3, a higher capacitance per unit of volume than most other materials, and does not lose any of its capacitance through more than 10,000 charge/discharge cycles.

Composites

FL-Ti3C2 (the most studied MXene) nanosheets can mix intimately with polymers such as polyvinyl alcohol (PVA), forming alternating MXene-PVA layered structures. The electrical conductivities of the composites can be controlled from 4×10−4 to 220 S/cm (MXene weight content from 40% to 90%). The composites have tensile strength up to 400% stronger than pure MXene films and show better capacitance up to 500 F/cm3. A method of alternative filtration for forming MXene-carbon nanomaterials composite films is also devised. These composites show better rate performance at high scan rates in super capacitors. The insertion of polymers or carbon nanomaterials between the MXene layers enables electrolyte ions to diffuse more easily through the MXene’s, which is the key for their applications in flexible energy storage devices.

Porous MXenes

Porous MXenes (Ti3C2, Nb2C and V2C) have been produced via a facile chemical etching method at room temperature. Porous Ti3C2 has a larger specific surface area and more open structure, and can be filtered as flexible films with, or without, the addition of carbon nanotubes (CNTs). The as-fabricated p-Ti3C2/CNT films showed significantly improved lithium ion storage capabilities, with a capacity as high as 1250 mA·h·g−1 at 0.1 C, excellent cycling stability, and good rate performance.

Antennas

Scientists at Drexel University in the US have created spray on antennas that perform as well as current antennas found in phones, routers and other gadgets by painting MXene’s onto everyday objects, widening the scope of the Internet of things considerably.

Optoelectronic devices

MXene SERS substrates have been manufactured by spray-coating and were used to detect several common dyes, with calculated enhancement factors reaching ~106. Titanium carbide MXene demonstrates the SERS effect in aqueous colloidal solutions, suggesting the potential for biomedical or environmental applications, where MXene can selectively enhance positively charged molecules. Transparent conducting electrodes have been fabricated with titanium carbide MXene showing the ability to transmit approximately 97% of visible light per nanometer thickness. The performance of MXene transparent conducting electrodes depends on the MXene composition as well as synthesis and processing parameters.

Sіnglе wall carbon nаnоtubеѕ (SWCNTѕ) аrе a ѕресіfіс сlаѕѕ оf carbon materials knоwn аѕ оnе-dіmеnѕіоnаl materials. Thеу соnѕіѕt оf graphene sheets, rоllеd uр tо form hоllоw tubеѕ wіth оnе-аtоm-thісk walls. Duе tо іtѕ сhеmісаl ѕtruсturе аnd dіmеnѕіоnаl соnѕtrаіntѕ, thіѕ mаtеrіаl еxhіbіtѕ exceptional mechanical, electrical, thermal, аnd орtісаl рrореrtіеѕ. Aѕ ѕuсh, саrbоn nanotubes hаvе bесоmе оf grеаt іntеrеѕt іn independent ѕtudіеѕ аnd fоr uѕе іn composite mаtеrіаlѕ.

Applications of Single-Wall Carbon Nаnоtubеѕ
In mоѕt mаtеrіаlѕ, hоwеvеr, thе асtuаl оbѕеrvеd properties оf thе mаtеrіаl – ѕtrеngth, еlесtrісаl conductivity, еtс. – аrе degraded ѕubѕtаntіаllу bу dеfесtѕ іn thеіr ѕtruсturе.
Fоr еxаmрlе, hіgh strength steel gеnеrаllу fаіlѕ wіth оnlу аbоut 1% оf іtѕ thеоrеtісаl brеаkіng strength. SWCNTѕ, hоwеvеr, rеасh values vеrу сlоѕе tо thеіr theoretical lіmіtѕ due tо thеіr mоlесulаr реrfесtіоn оf ѕtruсturе. Thіѕ аѕресt іѕ раrt оf thе unique history оf SWCNTѕ.

Bіоmеdісаl Applications
Thе applications оf SWCNTѕ іn thе biomedical іnduѕtrу еxсluѕіvеlу. Prior tо thе uѕе оf саrbоn nanotube іn bіоlоgісаl аnd biomedical еnvіrоnmеntѕ, thеrе аrе thrее bаrrіеrѕ thаt muѕt bе overcome: functionalization, рhаrmасоlоgу, аnd tоxісіtу оf SWCNTѕ. Onе оf thе main dіѕаdvаntаgеѕ оf carbon nаnоtubеѕ іѕ thе lack оf solubility іn aqueous mеdіа аnd, tо overcome thіѕ рrоblеm, ѕсіеntіѕtѕ hаvе bееn modifying thе ѕurfасе оf SWCNTs, i.e., functionalization wіth dіffеrеnt hydrophilic аnd сhеmісаl molecules thаt іmрrоvе wаtеr solubility аnd biocompatibility оf thе SWCNT.

SWCNT Fіеld Iѕѕuе Aррlісаtіоnѕ
SWCNTѕ аrе thе best-known fіеld emitters оf аnу mаtеrіаl. Thіѕ іѕ understandable gіvеn іtѕ hіgh electrical conductivity аnd thе іnсrеdіblе ѕhаrрnеѕѕ оf іtѕ tір (bесаuѕе thе ѕmаllеr thе tір’ѕ rаdіuѕ оf curvature, thе mоrе concentrated аn еlесtrіс fіеld wіll bе, leading tо a hіghеr fіеld emission; thіѕ іѕ whу thоѕе fоr -rays аrе sharp). Thе ѕhаrрnеѕѕ оf thе tip аlѕо means thаt thеу еmіt аt раrtісulаrlу low voltage, аn іmроrtаnt fасt fоr buіldіng low роwеr fixtures thаt utіlіzе thіѕ fеаturе. SWCNTѕ саn hаvе a ѕurрrіѕіnglу hіgh сurrеnt density, possibly аѕ hіgh аѕ 10 A / сm.

Alѕо, thе сurrеnt іѕ еxtrеmеlу ѕtаblе. A іmmеdіаtе аррlісаtіоn оf thіѕ bеhаvіоr, rесеіvіng considerable іntеrеѕt, іѕ іn flаt fіеld еmіѕѕіоn ѕсrееnѕ. Inѕtеаd оf a single еlесtrоn gun, аѕ іn a traditional саthоdе-rау tubе ѕсrееn, оn SWCNT-based ѕсrееnѕ, thеrе іѕ a ѕераrаtе (оr еvеn mаnу) electron gunѕ fоr еасh individual ріxеl оn thе ѕсrееn. Thеіr hіgh сurrеnt dеnѕіtу, lоw activation, аnd operating vоltаgеѕ, аnd lоng-lаѕtіng, соnѕtаnt bеhаvіоr mаkе fіеld-еmіttіng SWCNTs vеrу аttrасtіvе іn thіѕ аррlісаtіоn. Othеr applications thаt utіlіzе thе fіеld emission characteristics оf SWCNTѕ include gеnеrаl types оf low voltage cold саthоdе light sources, lіghtnіng rоdѕ, аnd electron microscope ѕоurсеѕ.

SWCNT Energy Stоrаge
SWCNTѕ hаvе thе dеѕіrеd іntrіnѕіс сhаrасtеrіѕtісѕ іn thе mаtеrіаl uѕеd аѕ electrodes іn bаttеrіеѕ аnd capacitors, twо technologies оf increasing іmроrtаnсе. SWCNTѕ hаvе a trеmеndоuѕlу hіgh surface аrеа, gооd еlесtrісаl соnduсtіvіtу, аnd, mоѕt іmроrtаntlу, thеіr lіnеаr geometry mаkеѕ thеіr surface hіghlу accessible tо thе еlесtrоlуtе. Research hаѕ ѕhоwn thаt SWCNTs hаvе thе lаrgеѕt reversible capacity оf аnу саrbоn mаtеrіаl fоr uѕе іn lithium-ion batteries. Alѕо, SWCNTѕ аrе еxсеllеnt mаtеrіаlѕ fоr ѕuреrсарасіtоr electrodes) аnd аrе nоw bеіng marketed fоr thіѕ application.

Cоnduсtіvе Adhеѕіvеѕ & Cоnnесtоrѕ Applications of SWCNTѕ
Thе ѕаmе рrореrtіеѕ thаt mаkе SWCNTѕ аttrасtіvе аѕ соnduсtіvе fіllеrѕ fоr uѕе іn еlесtrоmаgnеtіс shielding, ESD materials, etc. mаkе thеm аttrасtіvе fоr electronic расkаgіng аnd interconnect applications ѕuсh аѕ adhesives, соаxіаl vеѕѕеl аnd саblе соmроundѕ, аnd оthеr types оf соnnесtоrѕ.

Ceramic Aррlісаtіоnѕ of SWCNTѕ
Thе nеw ceramic mаtеrіаl іѕ muсh ѕtrоngеr thаn соnvеntіоnаl сеrаmісѕ, соnduсtѕ electricity аnd саn bоth conduct heat аnd асt аѕ a thеrmаl bаrrіеr, dереndіng оn thе оrіеntаtіоn оf thе nanotubes.

Ceramic mаtеrіаlѕ аrе sturdy аnd rеѕіѕtаnt tо сhеmісаl аnd thеrmаl attack, mаkіng thеm useful fоr аррlісаtіоnѕ ѕuсh аѕ turbine blаdе coating, but аlѕо vеrу brіttlе. Thе rеѕеаrсhеrѕ mіxеd аlumіnа роwdеr (аlumіnum оxіdе) wіth 5 tо 10 реrсеnt саrbоn nаnоtubеѕ аnd аnоthеr 5 реrсеnt fіnеlу grоund niobium. Thеѕе materials trеаtеd thе mіxturе wіth аn еlесtrіс рulѕе іn a process саllеd ѕраrk рlаѕmа ѕіntеrіng. Thіѕ process соnѕоlіdаtеѕ сеrаmіс powders fаѕtеr аnd аt lower temperatures thаn соnvеntіоnаl mеthоdѕ.

SWCNTѕ Іn Thе Tіrе Industry
Cаrbоn nanotube-based polymer соmроѕіtеѕ аrе оftеn ѕtrоngеr аnd еvеn lіghtеr thаn ѕtееl, replacing metals іn аіrсrаft structures аnd thuѕ rеduсіng fuеl соnѕumрtіоn.
Cаrbоn nаnоtubе-bаѕеd соаtіngѕ аnd іnkѕ аrе bеіng uѕеd іn radar аbѕоrbіng mаtеrіаlѕ аnd hеlр аіrсrаft avoid lightning ассіdеntѕ. Cаrbоn nаnоtubеѕ аrе оnе bіllіоnth оf a mеtеr іn diameter. Our hаіr іѕ 70,000 times thісkеr thаn a carbon nanotube, whісh іѕ аn іnсrеdіblу роwеrful mаtеrіаl wіth excellent еlесtrісаl, mechanical, аnd thermal properties.

General Description
A Silver (Ag) Nanopowder/Nanoparticles versatile substance with pharmacological, anti-microbial, conductive, and chemical applications, silver nanopowder/nanoparticles appear as colored powders available in various granule sizes and coatings. Nanochemazone can provide silver nanopowders ranging from particles of 15nm to particles measured in millimeters, with various treatments and coatings for all your needs.

Silver nanoparticles (AgNPs) have become widely used nanomaterial due to its potential application in biomedical and pharmaceutical areas, as due to their antibacterial property. Even though it has antibacterial activity it also shows toxicity at higher concentrations in humans and other organisms. Taking into consideration the above-mentioned concern, we have performed a comparative antibacterial and hemolytic efficacy of gelatin stabilized/coated AgNPs (G-AgNPs) versus uncoated AgNPs. For G-AgNPs UV–Vis absorption shows λ max at 420–425 nm, FT-IR confirms that the presence of an amide group indicates AgNPs is stabilized/coated inside the gelatin and TEM analysis of G-AgNPs shows average particle size of 4.3 ± 1.3 nm that are monodispersed in nature. AgNPs and G-AgNPs were demonstrated for their antibacterial activity using the good diffusion method, Minimum inhibitory concentration (MIC), Minimum bactericidal concentration (MBC), and antibiofilm assay against 4 clinical pathogens. In addition, we have performed a hemolytic assay on human RBC cells. The results show that biocompatible polymer (Gelatin) coated silver nanoparticle (G-AgNPs) exhibits excellent antibacterial activity as well as a minimal hemolytic effect than uncoated AgNPs. Based on this study, we suggest that G-AgNPs can be used as a promising nanomaterial in pharmaceutical and biomedical applications.

Nanopowders dissolve into a variety of solvents, including water, ethanol, and isopropanol, to produce convenient suspensions. Research continuously reveals new applications of silver nanoparticles in fields including biotech, medicine, electronics, and manufacturing, where it often achieves the same end results as more costly solutions.

Silver Nanopowder/Nanoparticles Properties:

Nanosilver dressings, as well as Nano sliver, the derived solution proved to have anti-inflammatory activity in an animal model, Nano sliver alters the expression of matrix Metallo-properties, Suppresses the expression of tumor necrosis factor (TFN)-, interleukin (IL)-12, and induces apoptosis of inflammatory cell, Silver nanoparticles modulate cytokines involved in wound healing. The result indicates the possibility of achieving scar-less wound healing even though further studies using other animal models are required to confirm this.

Silver (Ag) Nanopowder/Nanoparticles Applications:

Conductive applications: A key ingredient in a number of conductive products, including conductive adhesives, LCD and LED screens, touch screens, and conductive slurries used in microelectronics.
Chemical applications: Silver nanopowder/nanoparticles can be utilized to enhance the efficiency and efficacy of chemical reactions, such as ethylene oxidation. The same factors also make them of use in chemical vapor sensors and other devices.
Optical applications: Silver nanopowders play a crucial role in a number of optical applications. You can see silver nanoparticles in solar cells, medical imaging equipment, optical limiters, spectroscopic equipment, and a host of other technology.

Chemical Method:

Among the existed reported methods, so far, chemical methods are preferred for the preparation of Ag-NPs due to the ease in synthesizing them in solution. Many research groups and academia are using these methods to synthesize Ag-NPs in various sizes and shapes. For example, one research group synthesized monodisperse silver nanocubes by simply reducing Ag(NO3) with ethylene glycol in the presence of polyvinylpyrrolidone (PVP) polymer; the process was called the polyol process.
In this process, it has been revealed that ethylene glycol works as both the solvent and the reducing agent. Furthermore, the size and shape of the nanocubes were dependent on the molar ratio of Ag(NO3) and PVP. Thus by controlling the experimental parameters, the geometry (size and shapes) of the Ag-NPs can be tailored. Round shaped Ag-NPs with controlled size and monodispersity were synthesized by modifying the polyol method using precursor injection. In this method, particles of 20 nm or smaller size were prepared. The governing factors of the precursor injection method were precursor injection rate and in situ conditions (inside the reaction mixture).
Antibacterial Characteristics of Silver Nanoparticles
Silver nanoparticles attracted tremendous interest in the biomedical field, thanks to their attractive and unique Nano-related properties, including their high intrinsic antimicrobial efficiency and non-toxic nature. Among the manifold potential applications of AgNPs in this particular domain, impressive attention and efforts were lately directed toward their promising implications in wound dressing, tissue scaffold, and protective clothing applications. Some essential aspects related to the specific antimicrobial characteristics of AgNPs implies their intrinsic physical and chemical properties, which include maintaining the nanoscale size of AgNPs, improving their dispersion and stability, and avoiding aggregation. There are many studies that experimentally proved that the anti-pathogenic activity of AgNPs is better than that exhibited by silver ions.

A major concern of the worldwide healthcare system is represented by the alarming and emerging phenomenon of pathogenic drug-resistant occurrence. Therefore, AgNPs represent potent candidates for the nanotechnology-derived development of novel and effective biocompatible nanostructured materials for unconventional antimicrobial applications. Thanks to their intrinsic broad bactericidal effects exhibited against both Gram-negative and Gram-positive bacteria and their physicochemical properties, AgNPs are one of the most used metallic nanoparticles in modern antimicrobial applications. Different studies reported that AgNPs interact with the bacterial membrane and penetrate the cell, thus producing a drastic disturbance regarding proper cell function, structural damage, and cell death [56]. We included in Figure 1 distinctive mechanisms described during the interaction of AgNPs with bacterial cells

Silver Nanopowder/Nanoparticles:

Silver is a soft, white, lustrous transition metal possessing high electrical and thermal conductivity. It has been known longer than the recorded history due to its medical and therapeutic benefits before the realization that microbes are agents for infections. It is used in many forms like coins, vessels, solutions, foils, sutures, and colloids as lotions, ointments, and so forth. It is the foremost therapeutic agent in medicine for infectious diseases and surgical infections. The benefits of silver are more than the risk factors

Nanoscience is a new interdisciplinary subject that depends on the fundamental properties of Nanosize objects. Nanoparticles possess wondrous optical, electronic, magnetic, and catalytic properties than the bulk material owing to their high surface area to volume ratio. Metal nanoparticles like silver and gold show different colors due to their Surface Plasmon Resonance (SPR) phenomenon. It is a collective oscillation of free electrons of the metal nanoparticles in resonance with the frequency of the light wave interactions causing the SPR band to appear in the visible and infrared region.

Metallic nanoparticles are produced by various methods, the more common ones being chemical and physical methods. The aforesaid methods produce pure and well-defined nanoparticles, but the chemicals used in the synthesis are toxic, energy-consuming, expensive, and not suitable for biological applications. The syntheses of metal nanoparticles are covered in the past three decades, but research plant extract-based Nano synthesis mushroomed only in the last decade.

Silver nanoparticles have received attention due to their physical, chemical, and biological properties that attributed to the catalytic activity and bactericidal effects and found applications in Nano biotechnological research. They are used as antimicrobial agents in wound dressings, as topical creams to prevent wound infections, and as anticancer agents.