Optimal Laser Energy Research Articles

Physical Properties of HfO2 Nano Structures Deposited using PLD

On Quartz substrates, high purity transparent conductive the Di-Oxide of the (HfO2) Nano and micro-structure films were successfully coated. The method of (PLD) Deposition using Pulsed Laser, and the influence of laser energy was investigated. The XRD results revealed two distinct phases, cubic and monoclinic crystal shapes. Peaks in the Fourier-transform infrared (FTIR) spectra showed that HfO2 nanofilm was forming.The findings of the optical characteristics reveal an excellent transparency of nearly 80% (89 percent). As the laser wavelength decreases, the optical energy band gap values for Nanostructure of HfO2 were prepared, with values ranging from 5.24 to 5.53 eV. Also, the EDX results showed the appearance of hafnium peaks and oxygen peaks in varying proportions, which confirms that hafnium oxide is definitely obtained The results of the AFM reveal that when the pulsed laser intensity increases, the average grain diameter values increase from 52.96 to 74.54 nm. With regard to optimum pulsed laser energy, the based on I-V characterization, the generated factor ideality for created diodes was discovered to be decreasing, and the corresponding values of the barrier height grew. The ideality factor of the diode made the optimum pulsed laser energy (1800 mJ) was greater (n=3.1).

Superhydrophobicity induced antibacterial adhesion and durability of laser bidirectionally-textured zirconia surfaces with different inclination angles

Femtosecond laser bidirectional texturing with different laser energy densities and inclination angles was performed on zirconia (ZrO2) surfaces. The laser bidirectional texturing models under different inclination angles were constructed to predict the water contact angles (WCAs), and the superhydrophobicity induced antibacterial adhesion mechanism was analyzed. The results revealed that under the combined effect of the optimal laser energy density (7.0 J/cm2) and inclination angle (90°), the laser-textured ZrO2 surface could obtain a micro-nano dual-scale structure composed of periodic regular micro-cones and nanoparticles. This structure not only promoted the adsorption of carbon-containing hydrophobic groups from the stearic acid and the air to form a superhydrophobic surface with excellent chemical/mechanical durability and anti-fouling/self-cleaning abilities, but also minimized the contact area with the bacterial suspension (solid/liquid contact area ratio of 6 %) to enhance antibacterial ability. The optimal stearic acid-modified laser-textured ZrO2 surface exhibited an extremely low adhesive force (Fadhesive=6.69 μN) to the bacterial suspension, and thus achieved the highest antibacterial ratio of 85.3 %. This study is expected to enrich the application of ZrO2 ceramics in the medical field.

High cycle fatigue behavior and strengthening mechanisms of laser powder bed fusion pure tantalum

The fatigue behavior and strengthening mechanisms of the laser powder bed fusion pure tantalum (LPBF-Ta), coupled with a fatigue life prediction model, were originally explored. The fatigue strength of LPBF-Ta fabricated at the optimal laser energy density (154.16 J/mm3) is 348 MPa (106 cycles), showing a remarkable improvement of about 80 % and 50 % compared with that of the annealed and cold worked commercially pure tantalum, respectively. The microstructural analysis identifies that cellular structures averaging 300 nm in size contribute 438.2 MPa to strengthening, serving as the main contributor to fatigue strength. The breaching of cell walls by dislocations, along with the activation of cross-slip, ensures plasticity and ultimately enhances fatigue strength. Besides, the analysis of the defects reveals that the internal lack of fusion pore can induce the secondary fatigue crack, resulting in a region of brittle crack propagation. Furthermore, a finite life prediction model is established by originally incorporating the size of the crack source defect, and it significantly improves the prediction accuracy of the fatigue life. These results provide guidance for the development of fatigue strengthening strategies for LPBF-Ta.

A deterministic mechanism for efficient removal of arsenic and lead from wastewater using rapidly synthesized TiO2-(α-Fe2O3) nanoshells

Removal of heavy metals from wastewater using efficient techniques became demanding wherein various nanomaterials with tailored physicochemical traits can be useful. Thus, PLAL approach at an optimum laser energy was used to make TiO2-(α-Fe2O3) nanoshells (TFNSs) by mixing nanoparticles (NPs) suspension of TiO2NPs (TNPs) and α-Fe2O3NPs (FNPs) at 50 to 50 ratio. The produced nanocomposites were customized by targeting Ti that was submerged in deionized water as growth medium and then irradiate using the laser pulses with an optimum laser energy 10.6 J/cm2, spot focused size of 1.2 ± 0.2 mm, frequency of 6 Hz, and laser beam with a pulse duration of 8 ns for 15 minutes. In the course of the ablation process, the solution was agitated to achieve the formation of TNPs, FNPs, and TFNSs by preventing the formation of craters on the target surface. The obtained NSs were characterized to evaluate their structural, morphological, optical absorption and fluorescence characteristics. TEM micrographs of the liquid suspension confirmed the existence of spherical nanocrystallites of TiO2-(α-Fe2O3)NSs with mean diameter ≈12.4 ± 1.31 nm. XRD and FTIR results have been used to identify the samples crystalline nature and high purity. LSPR absorption bands of TFNSs were evidenced at 230 to 300 nm. These NSs showed prominent fluorescence peaks escorted with blue shift. Arsenic and lead removal efficiency of TFNSs from wastewater was better (over 99% at pH = 9) than TNPs and FNPs. The removal of arsenic and lead from wastewater by TNPs, FNPs and TFNSs were explained using a possible mechanism. The obtained results suggest that the proposed NSs can be potential for wastewater treatment, contributing towards sustainable growth.

Optimization of Pulsed Laser Energy Density for the Preparation of MoS2 Film and Its Device by Pulsed Laser Deposition.

This article aims to explore the most optimal pulsed laser energy density when using the pulsed laser deposition (PLD) process to prepare the MoS2 films. We gradually increased the pulsed laser energy density from 70 mJ·cm-2 to 110 mJ·cm-2 and finally determined that 100 mJ·cm-2 was the best-pulsed laser energy density for MoS2 films by PLD. The surface morphology and crystallization of the MoS2 films prepared under this condition are the best. The films consist of a high-crystallized 2H-MoS2 phase with strong (002) preferential orientation, and their direct optical band gap (Eg) is 1.614 eV. At the same time, the Si/MoS2 heterojunction prepared under the optimal pulsed laser energy density shows an opening voltage of 0.61 V and a rectification ratio of 457.0.

The effect of selective laser melting process parameters and remelting scanning strategy on relative density and surface hardness of stainless steel 316L

Selective laser melting (SLM) process is the foremost metal additive manufacturing (AM) technology that precisely generates complex geometries from CAD files. Mechanical behavior of printed parts is greatly affected by printing parameters and defining the optimal values of the process parameters to enhance the mechanical properties of components is highly regarded. In this work, four different SLM parameters including scanning speed, laser power, hatch spacing and scan pattern angle were applied to manufacture SS316L parts. For investigating the effect of each parameter and their interactions on hardness and relative density, Taguchi L16 orthogonal array was employed. The influence of part geometry and remelting is also evaluated in order to optimize the hardness and relative density of components. The results exhibited that the laser scanning speed was the most predominant SLM parameter for investigated mechanical properties. Analyzing the regression formula obtained from the results showed that the optimum laser energy density resulted in a 0.37% and 5.38% increase compared to the lowest relative density and hardness, respectively. High remelting energy associated with low remelting scanning speed, caused an 8.5% and 17.9% rise in hardness of squares and triangles, respectively; however, it led 12.5% reduction in hardness for circles. Remelting caused a 2.32% reduction, 2.1% increase and 5.3% rise on relative density for circles, squares and triangles, respectively.

Layer ablation and surface textured of Carbon fiber reinforced plastics by infrared pulsed laser

AbstractFor high‐quality composite bonded repairs, the research utilized a 1064 nm infrared pulsed laser to obtain geometry and texturing surface. The impact of grinding and laser treatment (0.4, 0.7, and 1.5 J/cm2) on the surface features of composite material was investigated, along with the tensile strength and failure modes. Findings demonstrated that laser treatment could significantly enhance surface roughness parameters and wetting properties compared to grinding. Additionally, an optimal laser energy density of 0.7 J/cm2 achieves complete resin removal without fiber damage while creating a laser‐induced periodic surface structure (LIPSS) based on a fiber weaving texture. The research revealed the synergistic bonding mechanism of “submicron mechanical locking” and “micron anchoring.” Laser treatment enhances the tensile strength of repaired specimens to 445 MPa, which was 90% of the original specimens, and substrate fracture was the associated failure mode.Highlights This paper applies laser technology to simultaneously achieve 3D geometry and surface texture on composites bonded repairs. A laser‐induced periodic surface structure was achieved while the resin was completely removed without carbon fiber damage. The tensile recovery rate of the laser‐treated sample was satisfied with the requirements of aircraft maintenance.

Effect of Energy Density on the Microstructure and Wear Resistance of Nickel-Based WC Coatings by Laser Cladding of Preset Zr702 Alloy Plates

This study aimed to evaluate the microstructure and wear resistance of laser cladding coatings with different energy densities in the case of a preset 0.5 mm thick Zr702 alloy plate to determine the specific present form of Zr elements and the optimal laser energy density. Thereby, microscopic characterization and performance tests were carried out by the microhardness tester, X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and tribometer. The results showed that, at different energy densities, the Zr elements in the coating were mainly in the form of ZrC and (Zr,W)C, which are hard particles with high wear resistance, and diffusely distributed in the coating to have second-phase-strengthening effects. Moreover, when the energy density was 28.3 J/mm2, the coating was well fused and had the highest microhardness of 936.4 HV0.2. The wear rate of the coating was the lowest at 90.8 μm3/(m·N). The wear was characterized by hard particle spalling and abrasive wear.

Enhanced Strength and Hardness of AS41 Magnesium Alloy Fabricated by Selective Laser Melting

AS41 magnesium alloy possesses outstanding performance features such as light weight, high strength to toughness ratio and excellent heat resistance due to the addition of Si element, while traditional casting methods are prone to inducing large grain size and coarse Mg2Si phase. In this study, we first reported utilizing the selective laser melting (SLM) technique, fabricating AS41 samples and exploring the effect of laser energy densities on the metallurgical quality by characterizing and investigating the microstructure and mechanical properties. Results showed that the optimal laser energy density range was 60 to 100 J/mm3. Average grain size of only 2.9 μm was obtained with weak texture strength of 1.65 in {0001} orientation. Meanwhile, many dispersed secondary β-Mg17Al12 and Mg2Si phases were distributed inside the α-Mg matrix. It was confirmed that the SLM process introduced more grain recrystallization, inducing giant high-angle grain boundaries (HAGBs) and hindering the movement of dislocations, therefore forming dislocation strengthening while achieving grain refinement strengthening. Finally, three times the ultimate tensile strength of 313.7 MPa and higher microhardness of 96.4 HV than those of the as-cast state were obtained, verifying that the combined effect of grain refinement, solid solution strengthening and precipitation strengthening was responsible for the increased strength. This work provides new insight and a new approach to preparing AS41 magnesium alloy.

3D printing externally reinforced layers for high-speed railway brake discs: Adaptability of SLM processes for manufacturing gradient materials

In this paper, the quasi-continuous ratio gradient alloy steel for the high-speed railway brake disc is prepared by selective laser melting (SLM). While maintaining the strength of the 24CrNiMo alloy steel at the core, it significantly improves the external wear and corrosion resistance of the material. The composition of the designed gradient alloy steel is x% 24CrNiMo + (1-x)% wear-corrosion resistant stainless steel (x is 100, 65, 35 and 0). Through the 20 groups of processes, the optimal process parameters of each gradient are summarized. Besides, the density, surface roughness and residual stress of the material are systematically characterized. The scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) are used to study the types of defects and formation mechanisms in the SLM process. The results show that the optimal laser energy density (LED) range for gradient alloy steel is 56 J mm−3 to 47.8 J mm−3. With the increase of LED, the density of the alloy first increases then decreases, and the type of defects changes from spheroidization defects to cracking. The sample with the best process parameter has a good metallurgical bonding between the gradients, which lays a good foundation for the subsequent analysis of wear resistance and corrosion resistance.

Evaluation of the Optical Aspects of the Ophthalmic Viscosurgical Device During Femtosecond Laser-Assisted Cataract Surgery.

PurposeIn femtosecond laser-assisted cataract surgery (FLACS), capsulorhexis can be performed with an ophthalmic viscosurgical device (OVD) filled in the anterior chamber. We aimed to investigate changes in the laser properties in various optical aspects, such as focal shifting, reflection, and absorption associated with OVD.MethodsSimulation was achieved by calculating the laser power attenuation due to reflection and spot size change using the Gullstrand eye model. Additionally, we calculated the absorption coefficient by measuring the laser power passing through the OVD with a laser meter and evaluated the effect of absorption by the OVD.ResultsIn our simulation, power attenuation due to reflection was a maximum of 0.07%, and power attenuation was 0.08% even when considering the change according to the incident angle. Power attenuation due to the change of the spot size at the focus was 0.005%. Owing to the absorption of the OVD, a power increase of up to 13.5% was required for an anterior chamber depth of 3.0 mm to obtain the same effect as the aqueous humor.ConclusionsThe main reason for laser power attenuation associated with OVD was laser absorption through the OVD, and could also be caused by laser cavitation bubbles. To complete a safe capsulotomy during FLACS, the laser power should be increased appropriately, considering the absorption by the OVD in the anterior chamber.Translational RelevanceThe study results can be applied to calculate the optimal femtosecond laser energy to achieve complete capsulotomy during FLACS in the presence of anterior chamber OVD.

Effect of laser energy density on microstructural evolution and wear resistance of modified aluminum bronze coatings fabricated by laser cladding

Modified aluminum bronze coating was successfully prepared using laser cladding. This research aimed to clarify the relationship between laser energy density and macrostructure, microstructure, microhardness and wear resistance of modified aluminum bronze coating. According to the experimental results it could be concluded that the reduction of laser energy density effectively improved the formability of the cladding layer surface, but low energy density could not fully melt powder. At the optimum laser energy density of 42.4 J/mm2, the cladding layer had the best combination of good flatness and density. There was no change in the composition phase categoryof samples prepared with varied laser energy densities, but the content of each phase varied. The aluminum bronze coating was mainly composed of α phase, κ phase, β’ phase. The content of α phase and κ phase reduced due to the decrease of laser energy density, and Widmanstatten side plate structure appeared in the case of low energy density. As the laser energy density decreased, the crystal grain size first decreased and then increased. An orthogonal scanning strategy leading to a random orientation of the aluminum bronze coating prepared by laser cladding shown as the EBSD pattern. The Schmidt factor and KAM increased with laser energy density decreased. Laser energy density played an important role in controlling the microhardness and wear resistance of coatings. Under the optimized process parameters, the maximum microhardness could reach 341.72 HV, and the minimum wear was only 4.37 × 10−2 mm3/N m.

Effect of laser preheat in magnetized liner inertial fusion at OMEGA

Integrated magnetized liner inertial fusion (MagLIF) experiments on the OMEGA laser system are modeled to investigate the effects of laser preheat on implosion performance. In both simulations and experiments, preheating the fuel with a laser enhances the neutron yield, with the maximum yield occurring at an optimal preheat laser energy. Increasing the preheat energy past the optimal value reduces the neutron yield. In simulations, the rate of the drop in neutron yield depends on the inclusion of the Nernst effect. The Nernst effect advects the magnetic field away from the center of the fuel region during the preheat stage of MagLIF on OMEGA and weakens magnetic-flux compression. If the Nernst effect is not included, the simulated drop in yield past the optimal preheat laser energy is more gradual as opposed to the sharper drop seen in experiments. Simulations are able to model trend in measured ion temperatures seen in experiments. A mix model is used to show that including mix from the wall in the simulated fuel region further degrades the yield and lowers the optimal preheat laser energy. Simulations with mix predict that increasing the initial axial magnetic field may still enhance yield performance in integrated implosions.

Formability, microstructure, and thermal crack characteristics of selective laser melting of ZK60 magnesium alloy

ZK60 magnesium alloy was processed by selective laser melting (SLM), and the influences of different process parameters on the quality of the samples were investigated. The microstructures, mechanical properties, and crack characteristics of SLMed ZK60 Mg alloy were analyzed. The results showed that high quality of the SLMed ZK60 Mg alloy was obtained at a laser energy density of 291.6 J/mm3; the relative density of the samples was >99%, and the surface roughness was 17.6 μm. The microstructure comprised an equiaxed zone, a lamellar zone, and a heat-affected zone (HAZ). Sizes of the equiaxed grain and HAZ were 8 μm and 10 μm, respectively. At the boundary of the molten pool, alloy element Zn was segregated, which formed a low melting point eutectic phase, leading to development of thermal cracks. At the optimal laser energy density, the thermal cracks were mainly liquation cracks. Despite the presence of a few liquation cracks in the samples, the fine grains and the nano precipitated phase played a key role in the mechanical properties of the sample. The tensile strength and elongation of the SLMed ZK60 Mg alloy were 246.3 MPa and 15.5%, respectively. Thus, SLM holds great promise for the manufacturing of high-density ZK60 components with a tensile strength comparable to conventional castings.

A cleaner production method for laser transmission welding of two transparent PMMA parts using multi-core copper wire

Transparent plastic products are very common in food packaging, medical packaging and other fields. Absorber is key factor during laser transmission welding of two transparent parts. There exist some problems of low strength, powder pollution and false welding when metal powder and wire are used as absorber. Regarding this issue, the goal of this paper is to propose a high-strength and cleaner production method for laser transmission welding of two transparent PMMA (polymethyl methacrylate) parts using multi-core copper wire. A three-dimensional thermal model is developed to predict the laser energy utilization coefficient of copper wire and the geometric size of the welding joint. Compared to one-core copper wire, multi-core copper wire can increase the laser energy utilization coefficient because of reducing laser reflection, and can obtain the lager welding joint size under the same welding parameters. Experimental data show that the melted PMMA plastic can enter into the multi-core copper wire so as to increase the van der Waals force between copper and PMMA. In addition, the shear strength of weld joint by multi-core copper wire is obviously higher than that by one-core copper wire. The maximum shear force can be up to 1100 N. Moreover, the phenomenon of PMMA substrate fracture occurs under appropriate welding parameters when multi-core copper wire is used. Furthermore, the concept of laser energy per unit of area (Qs, unit: J/mm2) is presented to analyze the relationship between welding parameters and the shear strength of welding joint and to obtain the optimal welding parameters. The optimal laser energy per unit of area (Qs) for high shear strength is 0.59 J/mm2 when multi-core copper wire is used.

Cellulose acetate-polyurethane film adsorbent with analyte enrichment for in-situ detection and analysis of aqueous Pb using Laser-Induced Breakdown Spectroscopy (LIBS)

In this work, we have investigated the potential application of cellulose acetate-polyurethane (CA-PU) film, as an adsorbent material as well as an enrichment medium for aqueous Pb quantification using Laser-Induced Breakdown Spectroscopy (LIBS). CA-PU was reported to be a good adsorbent for Pb removal from water medium due to its possession of O- and N-containing functional groups. The adsorption was first qualitatively investigated by observing Pb I (405.7 nm) emission line, before and after the adsorption. The study was further carried out using varied laser energies in order to optimize the produced spectra. The optimum laser energy was 54 mJ (gain = 1,500; width = 30 µs). The other aspects this work considered were contact time and pH, where the stable analysis was obtained after 12 h enrichment process and at pH 7. Normalization using C I (247.8 nm) internal standard line could compensate for the errors generated during the analysis. The non-linear regression of the calibration curve achieved correlation as high as R2 = 0.99997 and LOD = 1.02 mg/L. Based on the obtained LOD, this analytical method is suitable for the wastewater control in chemical industries in Indonesia. As an addition, LIBS is a potential technique to measure the binding energy of the adsorbent surface which requires further studies.

Low Fluorine Colorless Polyimide Substrate for Flexible OLED Display

Flexible display has become the main stream for the next innovative display. To build the flexible electronics, polyimide varnish is usually coated on the carrier glass with the thickness of a few micrometer and various devices such as flexible solar cell, flexible display, flexible printed circuit board, flexible terahertz sensor, and smart window [1]. Currently available colorless polyimide varnish is usually made of fluorine contained 6-FDA, which has good characteristics such as high transmittance, low yellow index, excellent solubility, but also has bad characteristics such as low decomposition temperature, high coefficient of thermal expansion, high cost, and environmentally unfriendliness due to fluorine. In this study, we make low fluorine contained polyimide varnish by substituting 6-FDA to BPDA + ODPA.Fig. 1 shows the molecular structure of 6-FDA, BPDA, and ODPA. Low fluorine contained polyimide varnish is composed of 40% 6-FDA, 40% BPDA, 20% ODPA and it showed the excellent characteristics such as the glass transition temperature of 300 deg, the decomposition temperature of 366 deg, the yellow index of 2.2, the coefficient of thermal expansion of 20 ppm/deg, and the transmittance at 550 nm wavelength of 98.1%.Because polyimide substrate made from coating polyimide varnish on carrier glass have to be protected using inorganic barrier material such as SiO2 and Si3N4. Also, transparent electrode is also required to apply voltage to the OLED display. Because the color of the polyimide substrate can be changed with the variation of barrier material thickness and transparent electrode thickness, we used optical simulator, Macleod, to access the transmittance change with the thickness change of SiO2 and Si3N4 as shown in fig. 2. Optimal thickness is selected at SiO2 of 400 nm and Si3N4 of 50 nm. The experimental transmittance is well matched with the simulation transmittance as shown in fig. 3.Fabricated device will be detached using innovative laser lift-off (LLO) that utilized excimer laser which scan the interface between the polyimide substrate and the carrier glass from the backside [2]. Fig, 4 shows the laser irradiation and the detached wrinkle free polyimide substrate. Before the delamination, the polyimide substrate is clear, but shows yellowish color during delamination process. Optimum laser energy for the delamination is compared with the color index as shown in fig. 5.We will make the OLED display on the polyimide substrate. Yi et al., Solar Energy 195, 340 (2020),Bian et al., App. Sur. Sci. 499, 143910 (2020). Figure 1

The Feasibility of Pop-Dusting Using High-Power Laser (2 J × 50 Hz) in Retrograde Intrarenal Surgery for Renal Stones: Retrospective Single-Center Experience.

Objective: Recently, retrograde intrarenal surgery (RIRS) using laser lithotripsy has become popular. However, the optimal laser energy setting for pop-dusting has not been established. In this study, we report our experiences of RIRS using the high-power (up to 100 W) pop-dusting (HPPD) technique. Methods: This study retrospectively assessed 82 cases with RIRS using HPPD. Patients who underwent abdominal CT or mercaptoacetyltriglycine (MAG3) diuretic renal scan at 3 months postoperatively were included in this study. Patient and stone characteristics and perioperative and postoperative outcomes were evaluated. Results: The average number of renal stones was 3.67 ± 4.11, and the average length of the largest stones was 13.30 ± 6.41 mm. The mean Hounsfield units was 959.99 ± 384.73. The operation time was 58.10 ± 26.67 minutes. The mean HPPD time was 11.93 ± 9.48 minutes, with settings of 1.97 ± 0.25 J and 48.78 ± 3.29 Hz. The stone-free rate was 89%. The mean hospital stay was 1.68 ± 1.29 days. Pelvicaliceal and ureter injuries were observed in 9.8% and 32.9% of the study population, respectively. However, there was no transfusion, subcapsular hematoma, persistent urinary leakage, ureteral or infundibular stricture, or renal functional deterioration. There was transient postoperative fever in 12.2% of the study population. Conclusions: HPPD could be performed safely during RIRS for renal stones without significant complications such as collecting system injury or bleeding. High-power laser mode (up to 100 W) can be a safe and effective choice for pop-dusting during RIRS, especially for large and hard stones.

Porosity, Hardness, Friction and Wear Performance Analysis of H13 SLM-Formed Samples

Selective laser melting (SLM), a type of additive manufacturing, is a powder bed process that makes use of a high-power laser beam to completely melt a thin layer of powder on a substrate, layer upon layer to form a solid part. This experimental study confirmed that laser power and scanning speed are indeed SLM’s most significant process parameters that affect porosity as stated in some literature and further studied the influence of laser power and/or laser-based volumetric energy density (VED) on hardness and friction and wear of SLM-formed samples. Full factorial design of experiment was carried out to study the influence of the two parameters on porosity with the help of Minitab 18 statistical software. The results obtained from this experiment were analyzed using analysis of variance. VED and laser power influence on hardness and friction and wear were studied on one factor at a time basis. Optimum laser power and scanning speed, optimum laser energy density values that achieve higher surface microhardness, minimum wear and porosity of H13 steel material were obtained from this experimental study.

Molecular-Scale Nanodiamond with High-Density Color Centers Fabricated from Graphite by Laser Shocking

Nanodiamonds (NDs) with nitrogen vacancy (NV) color centers have the potential for quantum information science and bioimaging due to their stable and non-classical photon emission at room temperature. Large-scale fabrication of molecular-size nanodiamonds with sufficient color centers may economically promote their application in versatile multidisciplinary fields. Here, the manufacture of molecular-size NV center-enriched nanodiamonds from graphite powder is reported. We use an ultrafast laser shocking technique to generate intense plasma, which transforms graphite to nanodiamonds under the confinement layer. Molecular dynamics simulations suggest that the high pressure of 35 GPa and the high temperature of 3,000K result in the metaphase transition of graphite to nanodiamonds within 100 ps. A high concentration of NV centers is observed at the optimal laser energy of 3.82 GW/cm 2 , at which point molecular-size (∼5 nm) nanodiamonds can individually host as many as 100 NV centers. Consecutive melamine annealing following ultrafast laser shocking enriches the number of NV centers >10-fold and enhances the spontaneous decay rate of the NV center by up to 5 times. Our work may enhance the feasibility of nanodiamonds for applications, including quantum information, electromagnetic sensing, bioimaging, and drug delivery. Ultrafast laser shock is used to transform graphite to nanodiamonds at ambient conditions The nanodiamonds can individually host ∼100 NV centers Annealing greatly enriches number of NV centers and enhances spontaneous decay rate Motlag et al. describe an ultrafast laser shocking technique to obtain ultrahigh concentrations of color centers in nanodiamonds (∼5 nm) under ambient conditions. Each nanodiamond can individually host ∼100 NV centers, which is orders of magnitude higher than the state of the art.