This PDF file contains the front matter associated with SPIE Proceedings Volume 10907, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

In food industry, detection of spoilage yeasts such as W. anomalus and B. bruxellensis and pathogens such as certain Listeria and E. coli species can be laborious and time-consuming. In the present study, a simple and repeatable technique was developed for rapid yeast detection using a combination of patterned gold coated polymer SERS substrates and gold nanoparticles [1−4]. For the first time, a state-of-the-art time-gated Raman detection approach was used as a complementary technique to show the possibility of using 532-nm pulsed laser excitation and avoid the destructive influence of induced fluorescence [3]. Conventional nanoparticles synthesized by colloidal chemistry are typically contaminated by non-biocompatible by-products (surfactants, anions), which can have negative impacts on many live objects under examination (cells, bacteria) and thus decrease the precision of bioidentification. Here, we explore novel ultrapure laser-synthesized Au-based nanomaterials, including Au NPs and Au Si hybrid nanostructures, as mobile SERS probes in tasks of bacteria detection [3]. We demonstrate successful identification of two types of bacteria (L. innocua and E. coli) and yeast (W. anomalus and B. bruxellensis). They showed several differing characteristic peaks making the discrimination of these yeasts possible without the need for chemometric analysis [2]. The use of composite gold-silicon laser-ablated nanoparticles in combination with the SERS substrate gave distinctive spectra for all the detected species. The detection limit of the studied species varied within 104-107 CFU/ml. The obtained results open up opportunities for non-disturbing investigation of biological systems by profiting from excellent non-disturbing nature of laser-synthesized nanomaterials in combination with outstanding optical detection technologies [2, 3]. [1] Uusitalo et al. 2016, http://pubs.rsc.org/en/content/articlehtml/2016/ra/c6ra08313g [2] Uusitalo et al. 2017a, https://www.sciencedirect.com/science/article/pii/S0260877417302054 [3] Kögler et al. 2018, https://onlinelibrary.wiley.com/doi/abs/10.1002/jbio.201700225 [4] Uusitalo et al. 2017b, https://www.spiedigitallibrary.org/journalArticle/Download?fullDOI=10.1117/1.OE.56.3.037102

Silver nanoparticles (AgNPs) have received great attention because of their unique characteristics and applications from basic to applied sciences. Recently, studies have also shown applications as larvicides against Aedes aegypti larvae [1], which generates great interest in public health due to the annual outbreaks Zica virus in Brazil, being associated with the recent cases of infants born with microcephaly. We synthesized AgNP, using polymethacrylic acid (PMAA) as a stabilizing and reducing agent catalyzed by ultraviolet radiation. The synthesis is clean, quick and low cost and average size of 10nm. Their use as nanolarvicide against Aedes aegypti in laboratory and field simulation will be reported. To check efficiency as larvicide the AgNPs were performed pilot bioassays, in which 20 fourth-instar larvae were placed in 100 ml of water with small concentrations of AgNPs (0.02 to 1.1 ppm). It was observed the mortality of the larvae from 6h and maximum expression of 24h exposure. The values LC50 and CL90 are 0.027, 0.044 ppm, respectively were recorded after 24 hours of exposure [2]. For the simulated field test, the initial efficacy, estimated by larval mortality in the first 96 hours after application of the product, was performed using 50 young instar-L1/recipient (20 liters). It was observed 100% mortality of the larvae in L1-instar in 96h of exposure of the nanoparticles. The persistence of mortality of the larvae in the L1-instar was observed up to the present moment by five months of exposure of the nanoparticles. [1]N. Sap-Lam et al., “UV irradiation-induced silver nanoparticles as mosquito larvicides,” in Journal of Applied Sciences 10(23), pp. 3132–3136 (2010) [2]Carvalho et al.; "Exploiting silver nanoparticles with PMAA against aedes aegypti larvae development: potential larvicidal activity" In Colloidal Nanoparticles for Biomedical Applications XIII, SPIE, San Francisco, pp. 23 (2018)

Nowadays there is a growing interest to the natural evolutionary changes and especially those that driven by environmental pollution and climate change. Climate change in combination with human activities largely influences the environment and especially the aquatic ecosystems. We utilize photonics and nanoscale materials for non-invasive screening of stress felt by water organisms due to environmental variations. We present the results of real-time quantitative assessment of internal temperature and pH in aquatic species. The developed technique can be adopted and used for the studies of many other biosystems from terrestrial and aquatic invertebrates to fish.

Nanoscopic optical imaging has made prominent progress in recent years, which provides a powerful tool for modern biology science. Superresolution optical imaging allows for the observation of ultra-fine structures of cells, cellular dynamics and cellular functions at nanometer scale or even single molecular level, which greatly promotes the development of life science and many other fields. However, challenges still exist for super-resolution optical imaging for live cells and thick samples in terms of imaging depth, imaging speed as well as biomedical applications. This talk will review the recent progress in superresolution optical microscopy and present our recent work. By combining stimulation emission depletion (STED) microscopy and fluorescence lifetime imaging (FLIM), a STED-FLIM superresolution microscopy was developed to improve the spatial resolution of STED and also perform FLIM imaging at nanometer resolution. A new fluorescent probe with low STED laser power was designed for live cell mitochondria imaging. STED-FLIM imaging of microtubules labeled with ATTO647N inside HeLa cells and the mitosis process was obtained, which provides new insight into the cell structure and functions. In addition, coherent adaptive optical technique (COAT) has been implemented in a stimulated emission depletion microscope to circumvent the scattering and aberration effect for thick sample imaging. Finally, stochastic optical reconstruction microscopy (STORM) superresolution imaging of mitochondrial membrane in live HeLa cells was obtained by the implementation of new fluorescent probes, improved imaging system and optimized single molecule localization algorithm. This provided an important tool and strategy for studying dynamic events and complex functions in living cells.

The presentation will overview our on-going activities on laser ablative synthesis of plasmonic colloidal nanomaterials and their biomedical applications. Our approach is based on ultra-short (fs) laser ablation from a solid target or already formed water-suspended colloids, which makes possible the fabrication of ultrapure bare (ligand-free) nanoparticles having controlled mean size and low size dispersion. The presentation will describe different approaches to achieve appropriate characteristics of nanomaterials (Au-based nanomaterials and alternative structures) and overview their biomedical applications. In particular, we show that Au nanoparticles can efficiently enhance Raman signals from different biological objects. Profiting from the observed enhancement and purity of laser-synthesized nanomaterials, we demonstrate successful identification of 2 types of bacteria (Listeria innocua and Escherichia coli). We also show that bare metal nanoparticles synthesized by laser ablation can provide an order of magnitude better response in glucose oxidation tasks, which promises their use as elecrocatalysts in bioimplantable therapeutic devices. Finally, we overview applications of bare plasmonic nanomaterials in phototherapy and tissue engineering tasks

Nowadays, different types of nano-materials are extensively used as parts or drug carriers that potentially can be developed by red blood cells (RBC). In fact there is a lack of studies of influence of nano-materials of different composition on the RBC and their interaction, especially in regards to hazards to human health. Utilizing conventional use of microscopy, optical tweezers, and scanning electron microscopy (SEM) the interaction of RBC incubated with nano-materials were examined. The results of direct observation of localization of nano-materials on the membranes of RBC show that some nano-materials influence strongly both the cells and mutual RBC interaction, resulting formation of larger cell aggregates.

Nitrogen vacancy (NV) centers have amassed considerable interest as biologically compatible magnetometers. NV centers are point defects consisting of a substituted nitrogen adjacent to a vacancy in diamond’s lattice. These defects exhibit an optically addressable magnetic field response at room temperature, a process known as optically detected magnetic resonance (ODMR). We take advantage of the imbalanced probability of the excited magnetic spin ±1 state to transition to the ground magnetic spin 0 state through an intermediate secondary singlet pathway in NV color centers. This alternative intersystem relaxation response can provide a source of contrast for live-cell imaging with potential nano-scale resolution, as well as for measuring low concentrations of paramagnetic ions. Paramagnetic molecules generate random magnetic field fluctuations which result in a non-zero RMS field. These fluctuations can induce spin relaxation in NVs in the near field of such paramagnetic molecules. This technique is applied at room temperature without microwave control frequencies or induced magnetic fields. The relaxation time for a bulk NV sensor doped with phosphorus was measured, which compared well with referenced values. Phosphorus doping in NV diamond allows the excitation wavelength to be red shifted for a less cytotoxic effect. ODMR spectra were acquired with a helium neon (HeNe) laser.

The nonlinear photonic behavior of a quasi-hexagonally close packed monolayer composed of gold nanospheres on glass substrate was studied using Z-scan with femtosecond laser pulses (70fs, 1kHz) in two regimes: on-resonance (~800nm) [1] and off-resonance (1500nm) [2]. The gold metasurface were prepared by self-assembly [3]. The third order nonlinear optical response of the gold metasurface revealed enhanced optical nonlinearities for both on and off-resonance. The values of n2 = -7.9x10-13 (-1.05x10-14) m2W-1 at 800nm(1500nm) was inferred for the nonlinear refractive index from closed aperture Z-scan, and 2 -0.9x10-6 (3x10-8) mW-1 at 800nm (1500nm) was inferred for nonlinear absorption from the open aperture data. Time resolved measurements using a Kerr gate setup showed an off-resonance ~2ps response time. We also studied the nonlinear response of the metasurface as a function of wavelength/linear refractive index, and observed that Miller's rule is not valid in this case. The large n2 value is four orders-of-magnitude larger, in modulus, than in silica glass at 1500 nm. The role of the metasurface arrangement as well as the origin of the gold nonlinearity in the short-wave infrared region is discussed. [1] J. Fontana, M. Maldonado, N. Charipar, S. A. Trammell, R. Nita, J. Naciri, A. Pique, B. R. Ratna, and A. S. L. Gomes, “Linear and nonlinear optical characterization of self-assembled, large-area gold nanosphere metasurfaces with sub-nanometer gaps,” Opt. Express 24(24), 27360-27370 (2016). [2] L. S. Menezes, L. H. Acioli, M. Maldonado, J. Naciri, N. Charipar, J. Fontana, D. Rativa, C. B. de Araujo and A. S. L. Gomes, Large third-order nonlinear susceptibility from a gold metasurface far-off the plasmonic ressonance, TO be submitted. [3] J. Fontana, J. Naciri, R. Rendell, and B. R. Ratna, “Macroscopic self- assembly and optical characterization of nanoparticle-ligand metamaterials,” Adv. Opt. Mater. 1(1), 100-106 (2013).

Atomically-thin materials have drawn great interest due to their exotic properties leading to a variety of promising new applications. However, the out-of-equilibrium dynamics of these materials are still not fully understood. Ultrafast electron diffraction (UED) is a powerful technique for the investigation of the transient structural dynamics of monolayers with unprecedented spatiotemporal resolution. The UED results of WSe₂ monolayers are reported and the suppression of the intensity of the Bragg diffraction spots following laser excitation is attributed to electron-phonon and phonon-phonon scattering. A two-temperature model is used to accurately describe these dynamics due to the low thermal conduction of the monolayer. Furthermore, the reported lifetimes are fit using a single-mode relaxation time approximation.

Herein, we numerically investigate terahertz photoconductive antennas (PCAs) based on optimized plasmonic nanostructures and absorption enhancement in nanocylinders. Metallic nanostructures playing an important role in nanophotonic applications are a hot topic nowadays. Such applications are possible due to their capability to focus or intensify electromagnetic fields close to the metal by employing excitation approach of surface plasmon polaritons. Plasmonic behavior in the visible to near-infrared light spectrum is achievable due to the metallic nanostructures employment. Herein, we study the absorption enhancement of silver and transparent-conducting oxides (TCO) nanocylinders with different diameters by means of effective medium approximation. This study also reports on the stronger enhancement in the case of TCO nanocylinders. The results show that resonant absorption amplitude and wavelength are dramatically affected by the thickness of the nanostructure as well as by the distances between nanocylinders. The outputs reported here provide a fertile ground for precise control of the nanowire structures for sensing and other enhanced optical applications. Because of compact structure, simple fabrication and room temperature operation, PCAs provide THz wave generation and detection. Moreover, PCAs are widely used in time domain THz imaging and spectroscopy systems for generating pulsed THz radiation. It is worthwhile noting, that in case of TCO nanocylinders, absorption enhancement for NIR wavelengths, being relevant for present THz generation setup, reaches up to 5-fold leading to 25-fold increase in THz radiation.

Pesticides play a critical role in protecting food crops from insects, fungi, weeds, and other unwanted pests. The increasing use of these pesticides to maintain food production and quality leads to potentially dangerous residues remaining on the food products. A rapid and non-destructive technique for trace level detection of pesticides at parts-permillion (ppm) or parts-per-billion (ppb) is surface enhanced Raman spectroscopy (SERS). A key feature of SERS is that it utilizes noble metal nanostructures to increase the weak Raman signals from analytes. We present a novel SERS substrate involving gold nanoparticles suspended in water that can be used to help identify four different pesticides: thiram, malathion, acetamiprid, and phosmet. To observe the desired Raman spectral signatures of these pesticides, apple skin contaminated with each chemical was swabbed and added to the colloidal gold nanoparticle suspension followed by interrogation with 785 nm laser excitation. This technique can detect each of these pesticides down to 1 part per million, where the pesticide residue tolerances on apples as established by the 2018 Code of Federal Regulations for thiram, malathion, acetamiprid, and phosmet are 5 ppm, 8 ppm, 1 ppm, and 10 ppm, respectively. The results presented here indicate that SERS is a useful tool for identifying pesticide residues on the surface of fruits for food quality and safety control.

Publisher’s Note: This conference presentation, originally published on 4 March 2019, was withdrawn on 11 March 2019 per author request.

Laser-induced forward transfer (LIFT) has demonstrated its ability for high resolution printing of a large set of materials in solid or liquid phase. The typical dimension of the LIFT-printed structures is of few micrometers. By downscaling the donor film thickness together with the pulse duration and the spot size of the laser, sub-micrometers metal droplets have also been printed. Recently, we have proposed the double pulse LIFT process (DP-LIFT) which relies on the use of two laser beams to transfer metal droplets in liquid phase from a solid donor thin film. First, a quasi-continuous wave laser irradiates the thin metal donor film to locally form a liquid film, then, a second short pulse laser irradiates this area to induce the formation of a liquid jet and the printing of a small droplet on the receiver substrate. We used time-resolved shadowgraphy to investigate the dynamics of high-velocity nanojets generated from solid copper films. These experiments show that this DP-LIFT approach induces the formation of very thin and stable liquid jets that expands over distances of few tens of micrometers for a large range of process conditions. We also demonstrated that the size of the melted metal pool plays an important role in the jet dynamics and allows controlling the size of the printed droplets. This process has been used to print 2D and 3D structures with micro and nano-meter sizes while avoiding the generation of any debris and these results demonstrates the high potential of DP-LIFT as a digital nano-printing process.

We have proposed that germanium-tin (GeSn) particles with high substitutional Sn concentrations can be synthesized by pulsed laser deposition (PLD) in ambient Ar at low pressure (~100 Pa). In this method, a Ge_0.9Sn_0.1 target is ablated by KrF excimer laser irradiation. At low Ar pressure (~100 Pa), the agglomeration of Ge and Sn atoms occurs easily in ambient Ar, and the agglomerated particles are rapidly cooled by collision with Ar atoms. An Si-receiving substrate was placed in front of the target. Various GeSn particles from several 100 nm to approximately 20 μm with spherical, disk, and irregular shapes were deposited on the Si-receiving substrate. In Raman spectra, the Ge-Ge vibration peaks of all the particles were shifted to lower wavenumbers compared with those of the Ge(100) crystal. The Raman peak position reportedly shifts to lower wavenumbers with increased substitutional Sn concentration in crystalline Ge. Thus, GeSn crystal particles with over 10% substituted Sn atoms can be synthesized by low-pressure PLD.

Recently, chiral mass transfer on the surface of plasmonic-active metals appeared upon their ablation with vortex laser pulses was found to be driven by a helical-shape temperature and corresponding surface tension gradients rather than optical angular momentum transfer from the incident beam. Here, we demonstrate that using of perfect optical vortices with different topological charges for direct single-pulse laser ablation of noble-metal films don't allow to change the helicity of produced nanoneedles (also called nanojets). Meanwhile, the chirality of laser-induced nanojets can be tuned in a wide range of parameter by properly designing and tailoring the spiral-shape intensity patterns. Such optimization of the laser intensity profile governing the helical movement of the transiently molten metal allows to produce nanostructures with controlled chirality suited for various nanophotonics and biosensing applications.

Ultra-large scale integrated circuits (ULSIs) have been continually scaled down according to Moore’s law. This can improve their power consumption and operation frequency but not the RC delay of their interconnections; to this end, super low dielectric constant films are required. We propose a novel method to fabricate porous SiO₂ films with a super low dielectric constant by F₂ laser deposition. In this method, a quartz target is evaporated by F₂ laser ablation in vacuum-chamber-controlled Ar partial pressure. The evaporated SiO₂ molecules are agglomerated in the vacuum, and the size of the SiO² nanoparticles are controlled by the Ar partial pressure. Porous SiO₂ films are formed on a Si-receiving substrate, which is placed in front of the quartz target. The pulse duration of the F₂ laser was approximately 20 ns, and the repetition rate of laser shots was 100 Hz. The base pressure of the vacuum chamber was 5 × 10⁻³ Pa. Then, Ar gas was introduced into the vacuum chamber through a mass flow controller to control the Ar partial pressure. The dominant size of the SiO₂ nanoparticles decreased from 1.5–2.0 nm to 1.0–1.5 nm with the Ar partial pressure decreasing from 20 Pa to 4.5 Pa. In addition, the relative dielectric constant k of the porous SiO₂ film formed at an Ar partial pressure of 4.5 Pa was 2.8, which is lower than that of thermal SiO₂ (k = 4.0). In addition, the leakage current of the nanoporous SiO₂ film was almost equal to that of the thermal SiO₂ film. From these results, we conclude that nanoporous SiO₂ films with a super low dielectric constant can be formed by F₂ laser deposition.

Methods of femtosecond laser ablation in deionized water were used to fabricate ultrasmall (< 2 nm), bare (ligand-free) organic luminophore DCEtDCS nanoparticles, which exhibit aggregation enhanced emission in the green range (533 nm) with the quantum yield exceeding 58% and provide no concentration quenching. In contrast to chemically synthesized counterparts, laser-synthesized DCEtDCS nanoparticles do not contain any organic impurities due to their preparation in aqueous medium and do not require surfactants to stabilize colloidal solutions, which makes them highly suitable for intracellular uptake and bioimaging. The highly negative surface charge of these nanoparticles impeded their cellular uptake, but when the surface was coated with chitosan, a cationic polymer, intracellular uptake in microglia was achieved. Using in vitro model, we finally demonstrate the efficient employment of ultrasmall and surfactant free fluorescent organic nanoparticles prepared by laser ablation as markers in bioimaging.

Perovskite nanocrystals (PNCs) have attracted a lot of scientific interest in the recent years due to the extraordinary optical and electronic properties such as compositional and structural versatility, tunable bandgap, high photoluminescence (PL) quantum yield (QY) and facile chemical synthesis. Among them, all inorganic CsnPbXm perovskites have attracted particular attention due to enhanced light emission and photo/thermal stability. Lower dimensionality polymorphs can be formed by manipulation of chemical- synthesis conditions where Cs+ can stabilize 3D [PbX6] framework, resulting in 2D (nanosheet), 1D (nanowire) and 0D (nanodot) internal octahedra arrays within the bulk of the perovskite. The gamut of available experimental approaches are further expanded in colloidal PNCs where both external size quantization and internal 0D structure may combine to achieve “multidimensional” electronic properties that are engineered both on atomic scale and nanoscale. In this work, we explore the photon emission statistics from individual 3D (CsPbBr3) and 0D (Cs4PbBr6) PNCs in order to address the origin of their PL emission. Using time-correlated, time-stamped single photon counting (TCSPC) we obtain PL intensity trajectories and extract PL lifetimes and second–order correlation functions at different excitation levels. Blinking traces show “burst-like” intensity behavior, with large bin-to-bin fluctuations, akin to molecular fluorophores. Recorded single photon emission statistics indicate that some of the measured PNCs are single photon emitters, others contain several emissive centers with very similar lifetimes. Few of the PNCs exhibited effects of photobrightening – superlinear increase of PL emission intensity due to the activation of an additional number of emissive centers within the PNC. Such emission behavior, independent of the confinement effects afforded by quantization in the medium/large sized Cs-based PNCs, supports theoretical framework that points towards Br-vacancy states localized within isolated octahedra.

In this contribution, the synthesis of fluorescent carbon quantum dots (CQDs) by laser fragmentation is reported. To achieve it, an initial suspension of carbon glassy microparticles in polyethylene glycol 200 is irradiated using two different experimental setups, a batch and a flow jet configuration. While the batch configuration is the standard irradiation setup, the flow jet configuration is less extended and it is proposed an implementation with common laboratory material. Besides, this system ensures an improved control over the fluence and the energy delivered to the target, increasing CQDs fabrication rate by 15%. The fluorescence of the generated nanoparticles is measured obtaining an increase of the quantum yield of one order of magnitude. The achieved fluorescence together with their easy cell internalization permits their use as fluorophore. To prove it, the flow jet synthesized CQDs are used for fluorescent imaging of healthy and cancerous human cells. The required incubation time is only 10 minutes and no centrifugation or any other extra processing of the sample is needed. In addition, the fluorescence photostability is measured to be of more than 2 hours in an in vitro application, proving the viability of the generated CQDs even for labeling in applications where long image acquisition times are required.

We developed molecular layer deposition method of atomically thin hybrid polymer film for the first time by developing atomic layer deposition method with sequential surface chemical reactions in order to minimize the effect of the dipole-dipole interaction between the electron spin of alkali metal atoms and the nuclear spin of the atoms in the glass of the cell. We controlled film thickness of polymer thin film precisely and finally aimed at improving the sensitivity of the optically pumped atomic magnetometer. In the presentation, we report on the relaxation time of spin polarization by atomically thin hybrid polymer film with laser pump-probe method.