Toxic Effects and Biodistribution of Ultrasmall Gold Nanoparticles *
Valerio Voliani in Nanomaterials and Neoplasms, 2021
Another method, characterizing the Au55 core in Au55(PPh3)12Cl6, is to study the relaxation behavior of excited electrons and to compare it with other AuNPs [79]. Femtosecond laser spectroscopy is the corresponding technique. The relaxation time depends on the electron–phonon coupling and on the electron surface collision of electrons. The experimental results concerning the femtosecond laser spectroscopy of AuNPs of different sizes are shown in Fig. 15.13 [79]. Weakening of the electron-phonon coupling dominates in large particles slowing down electronic relaxation (see Fig. 15.13, 15 nm particle). The 1.4 nm Au55 nucleus is characterized by strong surface collisions, making relaxation faster. In the case of the 0.7 nm AuNP (Au13), the extremely slow relaxation behavior arises from the fact that the electrons are strictly located in the Au-Au bonds.
Patterned Sapphire and Chip Separation Technique in InGaN-Based LEDs
Iniewski Krzysztof in Integrated Microsystems, 2017
To study laser scribing, samples was grown on 430-μm-thick 2-in. (0001) sapphire substrates using MOCVD under the same growth conditions [62]. The layer structures for LEDs with a total thickness of about 6 μm consist of undoped GaN/Si-doped n-GaN, five pairs of InGaN/GaN MQW, and Mg-doped p-GaN. Devices of 260 μm × 670 μm dimensions were fabricated by a normal side view LED chip process using ITO transmittance for p-contact and Cr/Au metals for n-contact. After that, the sapphire substrate was thinned to about 80 μm thickness by using backside lapping and polishing. Two lasers, with nanosecond and femtosecond laser pulses, were used to scribe grooves on the back of the thinned sapphire substrates. The nanosecond pulse laser has a wavelength of 355 nm, a repetition rate of 50 kHz, a pulse duration of 30 ns, and an output power of 0.4 W. The corresponding values of the femtosecond pulse laser are 1045 nm, 100 kHz, 150 fs, and 0.45 W. During the laser scan, the wafer chuck moves 18 mm/s for nanosecond laser and 400 mm/s for femtosecond laser, respectively.
Application of Nonlinear Microscopy in Life Sciences
Lingyan Shi, Robert R. Alfano in Deep Imaging in Tissue and Biomedical Materials, 2017
By far the most common multiphoton instrumentation employed for biological imaging is single spot laser scanning configuration based on a confocal laser scanning microscope. It is readily available, and further advances in femtosecond laser sources will make it even more common imaging modality. It is being used extensively in many areas of biological imaging, ranging from subcellular studies to whole organ or whole body imaging in neuroscience, developmental biology and cancer research, to name just a few. While adding fluorescence lifetime measurement capabilities is straightforward and not uncommon, there are only few studies using lifetime-based sensors or FLIM-FRET in the context of deep tissue imaging. On the other hand, FLIM-based quantitative studies of endogenous fluorophores (NADH, FAD) are quickly gaining popularity.
Comparison of Complication Rates between Manual and Femtosecond Laser-Assisted Techniques for Intrastromal Corneal Ring Segments Implantation in Keratoconus
Published in Current Eye Research, 2019
Tiago Monteiro, José F. Alfonso, Rui Freitas, Nuno Franqueira, Fernando Faria-Correira, Renato Ambrósio, David Madrid-Costa
When we analysed the incidence rate of corneal perforation or implant extrusion with femtosecond laser surgery, we had only one eye with a corneal endothelial perforation (0.9%) and no eye with late spontaneous extrusion, corneal melting or ICRS migration. The complication case occurred during the surgeon’s learning curve and was later resolved with a second procedure. Our complication rate with femtosecond laser is very low and similar to other studies. Coskunseven et al.21 have published the largest series of patients describing the incidence of complications during ICRS implantation with femtosecond laser; they have described a 0.6% rate (5 eyes) of endothelial perforations: in 2 cases the ICRS was displaced to the anterior chamber and the other 3 had the surgery repeated later. In the case of segment extrusion or migration, Coskunseven et al.21 described a 1.3% rate; a total of 11 eyes, 4 of which were explanted to avoid corneal melting; 2 eyes (0.2%) had corneal melting and implant extrusion due to superficial implant inside the corneal stroma. Other studies have described similar rates of ICRS complications with femtosecond laser assisted-surgery: Kubaloglu et al.9 1.0% of extrusions and 1.0% perforation; Ertan et. al.22 0.9% extrusion rate. In the past five years, the recent largest series published regarding ICRS implantation with femtosecond laser surgery do not describe any mechanical intra- or postoperative complications.1–4,22,26,27
Small Incision Lenticule Extraction (SMILE): Myths and Realities
Published in Seminars in Ophthalmology, 2021
The introduction of femtosecond lasers for flap creation has made LASIK even safer, with reduced intraoperative flap-related complications compared to the microkeratome for flap creation.3 The femtosecond laser produces tiny pulses of laser light, with pulse widths of around 200 femtoseconds. The laser light produces an intense energy field within the cornea – a plasma is produced which expands rapidly, creating a gas bubble within the tissue. A cleavage plane is created within the cornea, with tiny tissue bridges between the gas bubbles. Nonlinear tissue interactions occur and the effects are limited to a small area. The tissue bridges can then be broken mechanically to completely separate the cleavage plane from the underlying tissue.4
Sealing clear corneal incisions in cataract surgery
Published in Expert Review of Ophthalmology, 2018
Manpreet Kaur, Ankit Tomar, Farin Shaikh, Ruchita Falera, Lalit M. S. Bageshwar, Jeewan S. Titiyal
Hill et al. observed no postoperative wound leak or influx of trypan blue dye into the anterior chamber over a wide range of IOP fluctuations ranging from 5 to 50 mm Hg in sharply demarcated femtosecond laser-assisted incisions [27]. A prospective randomized pilot study observed superior wound sealability of femtosecond laser-assisted CCIs as compared with manual keratome-assisted CCIs [26]. However, the corneal inflammatory response and corneal cell apoptosis is higher than observed with the manual technique [31]. The high cost of femtosecond laser technology may limit its widespread use. Further well-designed randomized controlled trials are necessary to elucidate the wound-sealing properties of femtosecond laser-assisted CCIs.
Related Knowledge Centers
- Optical Coherence Tomography
- Organic Chemistry
- Laser
- Refractive Surgery
- Laser Construction
- Ti-Sapphire Laser
- Optical Cavity
- Beat
- Electro-Optic Modulator
- Prism Compressor