Direct laser writing (3D printing) is rapidly emerging as a versatile method for fabricating novel 3D structures that are needed for quantum computing, superconducting devices, selective coatings, and biomedical sensors. Here, we have created 2D patterns with potential for 3D diamond structures by direct laser writing lithography, which are carbonized in an inert Ar atmosphere at 540°C and then used as nucleation sites for diamond growth via hot-filament chemical vapor deposition (HFCVD). An array of 3D structures was fabricated via a two-photon polymerization process using a photo-polymeric resin on Si (100) and sapphire (0001) substrates. These 3D structures carbonized by thermal annealing show approximately 45–55

Herein, we report detailed magnetic characteristics of 10-nm thick Q-carbon films grown over a large area. Following the Bloch spin wave theory, we show that Q-carbon exhibits robust room-temperature ferromagnetism with a surprisingly high Curie temperature of 556 K. The square-root dependence of coercivity on temperature indicates homogeneous magnetic interactions in the sample. Finally, through ferromagnetic resonance spectroscopy measurements, we show that the spin interactions in Q-carbon are strong and intrinsic to the system. We envisage that the intrinsic ferromagnetism in Q-carbon opens a new frontier for carbon-based systems in spintronic devices.

Phase-pure crystalline cubic boron nitride (c-BN) thin films are of immense scientific and technical interest because of their suitable properties for optoelectronic and high-power applications, high thermal conductivity and hardness, chemical inertness to ferrous materials in high-temperature and caustic environments, and high optical transmittance over a broad wavelength range from the ultraviolet (UV) to the visible spectrum. However, the lack of controlled fabrication techniques for high-quality c-BN films significantly affects the reliable practical applications of this material. Recently, phase-pure single-crystal c-BN and a new phase of BN with unique properties, called quenched-BN (Q-BN), have been synthesized using a pulsed laser annealing (PLA) technique to overcome the current impediments in c-BN synthesis. This review paper comprehensively examines the current status of analytical research on the growth, characterization, and properties (optical and electrical) of c-BN films fabricated by different synthesis techniques, with a particular emphasis on the immensely promising PLA technique. In particular, the paper focuses on the processes used to obtain phase-pure c-BN films via epitaxial growth, characterization of defects and interfaces, and control of the structural, electrical, and optical properties of these films by controlling the growth parameters, including the laser–solid interaction for the direct conversion of nanocrystalline hexagonal boron nitride (h-BN) into crystalline c-BN using the PLA technique. The latest developments in c-BN electronics are also discussed, with a focus on producing p-and n-type conductivity using different dopants to achieve dopant concentrations far beyond the retrograde thermodynamic solid solubility limits. Finally, the future prospects and possible applications in emerging areas are discussed, as well as the goals and guidelines for future research of PLA-grown c-BN films. A comprehensive overview of the properties, application, characterization, shortcomings, and future prospects of c-BN

The lack of a standard anode for sodium-ion batteries (SIBs) has greatly hindered their applications. Herein, we show that a novel phase of carbon, namely Q-carbon, is an effective anode material for sodium-ion batteries. The Q-carbon, which is a metastable phase of carbon consisting of about 80% sp3- and 20% sp2-bonded carbon, is synthesized by nonequilibrium pulsed laser annealing and arc-discharge methods. Two types of Q-carbons, Q1 and Q2, were evaluated as anode material for SIBs. Q1 had a slow quench and was used as the control, whereas Q2 was Q-carbon with a rapid quenching. Q1 exhibits a high initial columbic efficiency of 81% and a low-capacity retention of less than 60%, whereas Q2 has a low initial columbic efficiency of 58% and a high-capacity retention of 81%. Q2 exhibits a stable capacity of 168 mAh·g−1 at a cycling rate of C/3 (124 mA·g−1), which is comparable to other hard carbon anodes reported in the literature. This unique synthesis method opens a pathway for the further tuning of Q-carbon with higher trapping/charging of Na+ ions in improved SIBs.

We present atomic structures and nonequilbrium synthesis of new class of materials, where the basic structural unit is a diamond tetrahedron. When units of one, two, and three tetrahedra are randomly packed, we create distinct phases of amorphous Q-carbon. Four tetrahedra in two adjacent layers lead to crystalline diamond lattice, which has four missing tetrahedra alternately. When these four missing tetrahedra are filled, we create subunit cell of crystalline Q-diamond. Theoretical calculations show that superconducting transition temperature (Tc) in 50 atomic % B-doped Q-diamond can reach near room temperature at ambient pressures. This is consistent with our earlier results using low-loss EELS measurements in 50 atomic % B-doped Q-carbon, which had mostly amorphous QB3 phase mixed with some crystalline Q-diamond phase. These EELS results showed that the Tc for these samples was in between 90K and 300K. Theoretical calculations of density of states, Eliashberg function, electron-phonon interaction parameter, and root-mean-square and logarithmic average of frequency in crystalline Q-diamond show Tc in the range of 268K to 300K, which is in a complete agreement with our EELS results in QB3.

Q-carbon, an allotrope of carbon, exhibits exciting functional properties and robust mechanical strength. We propose that the surface of the Q-carbon can be functionalized by doping it with silicon to enhance its performance as a potential implant material. As such, a coating of silicon-doped Q-carbon (Si-Q-carbon) is shown to minimize the formation of biofilm, thus reducing the risk of microbial infection. We report the formation of Si-Q-carbon coatings of varied thicknesses (10nm and 20nm) through the plasma-enhanced chemical vapor deposition technique. The surface composition and the bonding characteristics of the thin films were evaluated by Raman spectroscopy, XPS, and EELS studies, which showed that the thinnest sample (10nm) has a high sp(3) content of similar to 85%. Furthermore, wettability and surface energy calculations were undertaken to investigate the surface characteristics of the coatings. The 10nm sample was found to be more hydrophilic with a water contact angle of 75.3 degrees (+/- 0.6 degrees). The antibacterial activity of Si-Q-carbon coatings was investigated using a Staphylococcus epidermidis agar plating technique, and the adhesion of bacteria was explained in terms of the surface properties of the thin films. We demonstrate that the Si-Q-carbon coating with the highest sp(3) content is hydrophilic and showed a 57% reduction in adhered biofilm relative to a glass control. We envisage the potential application of Q-carbon in arthroplasty devices with enhanced mechanical strength and resistance to periprosthetic joint infections.

Carbon-based nanostructures (CBNs) have attracted immense attention from biomedical researchers due to their unique combination of extraordinary mechanical, thermal, electrical, and optical properties. They can be easily conjugated with several organic and inorganic molecules, enhancing their potential to perform advanced therapeutic actions, which are not possible with existing materials and techniques. As such, the current advances in some of the diagnostic and therapeutic applications of CBNs are discussed in this review. In particular, the applications of carbon nanotubes (CNTs), graphene, and its oxides, as well as diamond-like carbon in tissue engineering, drug delivery, antimicrobial coatings, and medical diagnostics are critically reviewed. Among the several types of CBNs currently in use, it is shown that nanocomposites of functionalized graphene oxide outweigh the mechanical strength of other biomaterials by 110% without compromise to their biocompatibility. Similarly, due to the unique combination of the surface properties of CNTs, such as charge, polarity, and chemistry, these materials are useful for detecting protein molecules at concentrations as low as 5 ng mL−1. Due to its ease of production, robust mechanical strength, and biocompatibility, DLC is effective as an antimicrobial coating for biomedical implants and devices. Further, we provide insight into the biotoxicity and limitations of current CBNs and highlight the need for a novel biomaterial that can outperform the materials that are currently in use. Finally, the future perspective of carbon-based nanostructures in biomedical applications is discussed by introducing Q-carbon, a newly discovered ferromagnetic phase of carbon with interesting structural and functional properties. We describe the structure and multifunctional capabilities of Q-carbon. We envision Q-carbon as an alternative to CBNs for therapeutic applications, diagnostic applications, and as a protective coating for medical devices.

We present a systematic investigation of the detailed structural, optical and magnetic properties of ZnO thin films deposited by pulsed laser deposition as a function of varying Al doping from 0% to 5%. The observed features can be associated with strain introduced into the ZnO lattice by the incorporation of Al. Enhanced optical transmittance values close to 95% were achieved in Al-doped ZnO epitaxial films deposited on sapphire substrates. In addition, these films exhibit robust ferromagnetic properties at room temperature with saturation magnetization that varies from 143 to 63 emu/cm3 for Al dopant concentrations from 0% to 5%. It is demonstrated that the saturation magnetization is related to the strain introduced into the lattice with increased Al doping.

The formation of 3c-SiC is of interest due to potential applications in the semiconductor industry; however, there are difficulties in obtaining 3c-SiC by conventional methods. Being a metastable phase, non-equilibrium growth conditions are favorable in the growth process. This paper reports the formation of nano-sized 3c-SiC by nanosecond laser annealing of Si–Q-carbon layers on the silicon (100), which is confirmed by its characteristic LO and TO peaks in the Raman spectra. We also show that the traditional HFCVD technique results in the 6H-polytype instead, as confirmed by SEM, Raman spectroscopy, and EBSD. Further, we investigate the role of these phases on the nucleation of heteroepitaxial diamond on a Si (100) substrate. We show that these phases as interlayers enhance the diamond growth significantly. The HRSTEM studies were performed to understand the interfacial structure and phase responsible for high diamond nucleation. These findings are significant for 3c-SiC and diamond electronics applications.

Tubular diamond structures with high surface areas are very desirable for various potential electrochemical applications. Here, we report a simple and cost-effective two-step method for the synthesis of a diamond tube with a porous tube wall from carbon nanotube (CNT) hollow fibers via pulsed laser annealing (PLA) and hot filament chemical vapor deposition (HFCVD). These diamond tubes exhibit high double-layer capacitances of 11.65-18.07 mF cm(-2), three orders of magnitudes higher than the equivalent flat diamond films. Scanning electron microscopy (SEM) shows the presence of diamond microspheres composed of both micro- and nanocrystallites on the entire tube after 3-6 h HFCVD. The number density of the diamond, the average size of diamond microspheres, and the nanocrystallite content on the microspheres can be controlled by HFCVD time and laser annealing parameters of CNT hollow fibers. The electron back-scattered diffraction analysis shows the crystallographic orientation of the prepared diamond along the < 101 > plane. Raman spectra show a sharp characteristic/signature diamond peak at similar to 1332 cm(-1), corresponding to an unstrained high-quality diamond. The magnificent electrochemical performances of these CNT-supported diamond tubes are explained by their significantly enhanced electroactive surface area and the presence of a very small fraction (0.73-1.03%) of sp(2) carbon in diamond tubes for electron conduction. The density of states, band gaps, and outmost quantum capacitance (similar to 200 mu F/cm(2) at -2.2 V electrode potential) of the tubular diamond are calculated by the density functional theory calculations, which support our experimental findings and suggest its future potentiality as an efficient supercapacitor electrode material.

We describe a novel excimer laser-based route for the fabrication of crystalline MoS2 nanoneedles. Laser annealing of MoS2 thin films at a low energy density of 0.08 Jcm−2 resulted in a closed-pack structure with low defects and excellent conductivity due to melting and rapid quenching. A further increase in laser annealing energy density resulted in the formation of MoS2 nano-needles. This structure of MoS2 was found to have a remarkable reduction ability for H2O2 at − 0.14 V over a wide linear range; a low detection limit (0.45 nM (S/N = 3)) and sensitivity of 2.38 μA/mM cm−2 were demonstrated.

High-voltage spinel LiNi0.5Mn1.5O4 (LNMO) is a promising next -generation cathode material due to its structural stability, high operation voltage, and low cost. However, the cycle life of LNMO cells is compromised by detrimental electrode-electrolyte reactions, chemical crossover, and rapid anode degradation. Here, we demonstrate that the cycling stability of LNMO can be effectively enhanced by a high-energy laser treatment. Advanced characterizations unveil that the laser treatment induces partial decomposition of the polyvinylidene fluoride binder and formation of a surface LiF phase, which mitigates electrode-electrolyte side reactions and reduces the generation of dissolved transition-metal ions and acidic crossover species. As a result, the solid electrolyte interphase of the graphite counter electrode is thin and is composed of fewer electrolyte decomposition products. This work demonstrates the potential of laser treatment in tuning the surface chemistry of cathode materials for lithium-ion batteries.

The surface chemistry of silicon-incorporated diamond-like carbon (Si-DLC) was tailored utilizing oxygen and fluorine plasma treatments. Successful anchoring of oxygen and fluorine functional groups to the surface of Si-DLC was verified using X-ray photoelectron spectroscopy. The impact of surface modification of Si-DLC on hydrophobicity was correlated with the viability of L929 mouse fibroblasts. The confocal microscopy and viability results indicated that oxygen-treated Si-DLC showed increased cell viability compared to untreated Si-DLC and fluorine-treated Si-DLC samples 5 days after seeding. The increased cell viability was correlated with the conversion of the hydrophobic surface of Si-DLC into a hydrophilic surface by oxygen plasma treatment.

Nanosecond pulsed laser annealing significantly improves cyclability and current carrying capacity of lithium-ion batteries (LIBs). This improvement is achieved by engineering of microstructure and defect contents present in graphite in a controlled way by using pulsed laser annealing (PLA) to increase the number density of Li+ ion trapping sites. The PLA treatment causes the following changes: (1) creates surface steps and grooves between the grains to improve Li+ ion charging and intercalation rates; (2) removes inactive polyvinylidene difluoride (PVDF) binder from the top of graphite grains and between the grains which otherwise tends to block the Li+ migration; and (3) produces carbon vacancies in (0001) planes which can provide Li+ charging sites. From X-ray diffraction data, we find upshift in diffraction peak or reduction in planar spacing, from which vacancy concentration was estimated to be about 1.0%, which is higher than the thermodynamic equilibrium concentration of vacancies. The laser treatment creates single and multiple C vacancies which provide sites for Li+ ions, and it also produces steps and grooves for Li+ ions to enter the intercalating sites. It is envisaged that the formation of these sites enhances Li+ ion absorption during charge and discharge cycles. The current capacity increases from an average 360 mAh/g to 430 mAh/g, and C–V shows significant reduction in SEI layer formation after the laser treatment. If the vacancy concentration is too high and charge-discharge cycles are long, then trapping of electrons by Li+ may occur, which can lead to Li0 formation and Li plating causing reduction in current capacity.

Improved performance of lithium-ion batteries (LIBs) plays a critical role in the future of next- generation battery applications. Nickel-rich layered oxides such as LiNi0.8Mn0.1Co0.1O2 (NMC 811), are popular cathodes due to their high energy densities. However, they suffer from high surface reactivity, which results in the formation of Li2CO3 passive layer. Herein, we show the role of nanosecond pulsed laser annealing (PLA) in improving the current capacity and cycling stability of LIBs by reducing the carbonate layer, in addition to forming a protective LiF layer and manipulating the NMC 811 microstructures. We use high-power nanosecond laser pulses in a controlled way to create nanostructured surface topography which has a positive impact on the capacity retention and current capacity by providing an increased active surface area, which influences the diffusion kinetics of lithium-ions in the electrode materials during the battery cycling process. Advanced characterizations show that the PLA treatment results in the thinning of the passive Li2CO3 layer, which is formed on as-received NMC811 samples, along with the decomposition of excess polyvinylidene fluoride (PVDF) binder. The high-power laser interacts with the decomposed binder and surface Li+ to form LiF phase, which acts as a protective layer to prevent surface reactive sites from initiating parasitic reactions. As a result, the laser treated cathodes show relative increase of the current capacity of up to 50%, which is consistent with electrochemical measurements of LiB cells.

The synthesis of diamonds with different microstructures is important for various applications including nanoelectronic devices where diamonds can be implemented as heat spreaders. Here we report the synthesis of functional diamond microstructures and coatings, including diamond microfibers, microspheres, tubes, and large-area thin film, using amorphous and graphitic carbon precursors by hot filament chemical vapor deposition. The characteristics of microstructures depend upon initial carbon precursors and their laser annealing pretreatments. Low-cost and abundant carbon precursors act as diamond nucleation sites and accelerate diamond growth, while laser annealing can further promote the nucleation and growth of diamond. As a result, carbon microfibers are converted to diamond microfibers, while large diamond microspheres are formed from multipulse laser-annealed carbon microfibers. Both of the diamond structures consist of 5-fold twinned microcrystallites. Highly dense and phase-pure diamond films are observed using porous carbon seed, and individual diamond tubes with porous walls are obtained by using carbon nanotube hollow fibers. The electron backscatter diffraction analysis confirms the diamond cubic lattice structure, while sharp diamond peaks (1331-1333 cm-1) in Raman spectra demonstrate the excellent diamond quality of prepared diamond microstructures.

We report the discovery of Q-silicon with an atomic density of 60% higher than crystalline silicon while keeping the bonding characteristics the same as normal silicon. Distinct amorphous phases are created, when one, two, or three tetrahedra are randomly packed, and a crystalline phase of Q silicon is formed when subunit cells are arranged along < 110 > directions with alternate holes. Nanosecond laser melting of amorphous silicon in an undercooled state and quenching have created Q-silicon with robust ferromagnetism compared to the diamagnetism of silicon. The blocking temperature of Q-silicon is estimated to be over 400 K, thus opening a new frontier for spin-based computing and atomic-level storage.

This study demonstrates a novel laser processing technique for the direct conversion of amorphous boron nitride (a-BN) into phase-pure cubic boron nitride (c-BN) nanoneedles. c-BN is a promising material for power electronics due to its unique properties, including hardness, chemical durability, and thermal resistance. However, the production of phase-pure c-BN nanodots and thin films under ambient conditions has been hindered by significant challenges. This study shows that nanosecond laser irradiation induces the melting of BN, resulting in the formation of an undercooled molten BN phase. At a threshold energy density of 0.3 J/cm 2 , a first-order phase change from a-BN to phase-pure single-crystalline c-BN is observed. Detailed analysis employing high-resolution scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), high-resolution Raman spectroscopy, and photoluminescence investigations confirms the formation of c-BN nanoneedles. Ab initio molecular dynamics simulations of pulsed laser melting and quenching further elucidate the direct conversion of molten BN into c-BN. Laser-irradiated c-BN crystallites exhibit sharp emission lines at approximately 1.97 eV and 2.15 eV, corresponding to the radiation-cubic (RC) centers and consistent with photoluminescence from inherent vibrionic defects connected to nitrogen-vacancy defects. This innovative laser processing technique offers a scalable and cost-effective method for producing nano- and microcrystalline c-BN thin films, thereby opening avenues for applications in nanophotonics, quantum computing, and high-power and radio frequency (RF) electronics.

We report the formation of Q-carbon nanolayers, Q-carbon nanoballs, nanodiamonds, microdiamonds, and their composites by controlling laser and substrate variables. The choice of these parameters is guided by the SLIM (simulation of laser interactions with materials) computer modeling. For a constant film thickness and initial sp(3) content, we obtain different microstructures with increasing pulse energy density as a result of different quenching rate and undercooling. This is related to decreasing undercooling with increasing pulse energy density. The structure of thin film Q-carbon evolves into Q-carbon nanoballs with the increase in laser annealing energy density. These Q-carbon nanoballs interestingly self-organize in the form of rings with embedded nanodiamonds to form Q-carbon nanoballs/diamond composites. We form high quality, epitaxial nano, and micro diamond films at a higher energy density and discuss a model showing undercooling and quenching rate generating a pressure pulse, which may play a critical role in a direct conversion of amorphous carbon into Q-carbon or diamond or their composites. This ability to selectively tune between diamond or Q-carbon or their composites on a single substrate is highly desirable for a variety of applications ranging from protective coatings to nanosensing and field emission to targeted drug delivery. Furthermore, Q-carbon nanoballs and nanodiamonds are utilized as seeds to grow microdiamond films by HFCVD. It is observed that the Q-carbon nanoballs contain diamond nuclei of critical size, which provide available nucleation sites for diamond growth, leading to stress-free, adherent, and denser films, which are needed for a variety of coating applications.

Heart failure resulting from acute myocardial infarction (AMI) is an important global health problem. Treatments of heart failure and AMI have improved significantly over the past two decades; however, the available diagnostic tests only give limited insights into these heterogeneous conditions at a reversible stage and are not precise enough to evaluate the status of the tissue at high risk. Innovative diagnostic tools for more accurate, more reliable, and early diagnosis of AMI are urgently needed. A promising solution is the timely identification of prognostic biomarkers, which is crucial for patients with AMI, as myocardial dysfunction and infarction lead to more severe and irreversible changes in the cardiovascular system over time. The currently available biomarkers for AMI detection include cardiac troponin I (cTnI), cardiac troponin T (cTnT), myoglobin, lactate dehydrogenase, C-reactive protein, and creatine kinase and myoglobin. Most recently, electrochemical biosensing technologies coupled with graphene quantum dots (GQDs) have emerged as a promising platform for the identification of troponin and myoglobin. The results suggest that GQDs-integrated electrochemical biosensors can provide useful prognostic information about AMI at an early, reversible, and potentially curable stage. GQDs offer several advantages over other nanomaterials that are used for the electrochemical detection of AMI such as strong interactions between cTnI and GQDs, low biomarker consumption, and reusability of the electrode; graphene-modified electrodes demonstrate excellent electrochemical responses due to the conductive nature of graphene and other features of GQDs (e.g., high specific surface area, π–π interactions with the analyte, facile electron-transfer mechanisms, size-dependent optical features, interplay between bandgap and photoluminescence, electrochemical luminescence emission capability, biocompatibility, and ease of functionalization). Other advantages include the presence of functional groups such as hydroxyl, carboxyl, carbonyl, and epoxide groups, which enhance the solubility and dispersibility of GQDs in a wide variety of solvents and biological media. In this perspective article, we consider the emerging knowledge regarding the early detection of AMI using GQDs-based electrochemical sensors and address the potential role of this sensing technology which might lead to more efficient care of patients with AMI.