Poly Methyl Methacrylate Layer Research Articles

Fabricating thin films with colloidal quantum dots on planar substrates using polymethyl methacrylate

This paper demonstrates the possibilities of a method of depositing uniform layers of colloidal CdSe/CdS/ZnS quantum dots with a hydrophobic shell made from fatty acids and aliphatic amines onto planar substrates. Using centrifugation onto flat substrates, separate thin layers of polymethyl methacrylate and quantum dots are deposited with good adhesion, with the quantum dots being dispersed in the polymethyl methacrylate. The topology of the fabricated layers is investigated by means of atomic-force microscopy and luminescence mapping, and the processes of aggregation and segregation of the quantum dots into a separate phase is studied. The deposited layers can be structured by means of electron-beam lithography in order to create quantum-dot-based nanostructures.

Self-Assembly of Metal Oxide Nanoparticles in Liquid Metal toward Nucleation Control for Graphene Single-Crystal Arrays

Summary We have achieved the spontaneous assembly of alumina nanoparticles on a liquid metal surface and further synthesized a very-large-scale graphene single-crystal array. The effective electrical field established as a result of the electrical charge of the alumina nanoparticles in the liquid metal ensures the ordered self-assembly of the alumina islands and lays the foundation for precise spatial control of graphene nucleation, leading to the formation of graphene single-crystal arrays. In addition, controlling the density of the alumina in the liquid metal can precisely tune the periodicity of the arrays. This simple strategy, which is unlike the usual solid/aqueous solution system, opens up new territory for nanoparticle assembly. Focusing on the origin of the nanoparticle interaction that drives the self-assembly of ordered structure in the liquid metal system is a promising avenue for triggering more interesting applications.

Flexible and Salt Resistant Janus Absorbers by Electrospinning for Stable and Efficient Solar Desalination

AbstractWith recent progress in interfacial solar steam generation, direct solar desalination is considered a promising technology for providing a clean water solution through a cost effective and environmental‐friendly pathway. As a high and stable water production rate is the key to enable widespread applications, salt deposition becomes a critical issue that needs to be addressed. Herein, the authors demonstrate that a flexible Janus absorber fabricated by sequential electrospinning can enable stable and efficient solar desalination. Taking advantage of the unique structure of Janus, two functions of steam generation, solar absorption and water pumping, are decoupled into different layers, with an upper hydrophobic carbon black nanoparticles (CB) coating polymethylmethacrylate (PMMA) layer for light absorption, and a lower hydrophilic polyacrylonitrile (PAN) layer for pumping water. Therefore, salt can only be deposited in the hydrophilic PAN layer and quickly be dissolved because of continuous water pumping. Janus absorber demonstrates high efficiency (72%) and stable water output (1.3 kg m–2 h–1, over 16 days) under 1‐sun, not achieved in most previous absorbers. With a unique structure design achieved by scalable process, this flexible Janus absorber provides an efficient, stable and portable solar steam generator for direct solar desalination.

Enhanced efficiency of hybrid amorphous silicon solar cells based on single-walled carbon nanotubes and polymer composite thin film

We report a simple approach to fabricate hybrid solar cells (HSCs) based on a single-walled carbon nanotube (SWCNT) film and thin film hydrogenated amorphous silicon (a-Si:H). Randomly oriented high-quality SWCNTs with conductivity enhanced by means of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate are used as a window layer and a front electrode. A series of HSCs are fabricated in ambient conditions with varying SWCNT film thicknesses. The polymethylmethacrylate layer drop-casted on fabricated HSCs reduces the reflection fourfold and enhances the short-circuit Jsc, open-circuit Voc, and efficiency by nearly 10%. A state-of-the-art J–V performance is shown for SWCNT/a-Si HSC with an open-circuit voltage of 900 mV and an efficiency of 3.4% under simulated one-sun AM 1.5 G direct illumination.

Anatomorradiographic Description of the Capybara´s Teeth (Hydrochoerus hydrochaeris)

Background: The capybara (Hydrochoerus hydrochaeris) is the largest South American rodent species alive, and it preferentially inhabits floodable environments. Currently, capybara populations have been increasing owing to lack of predators and increased availability of food. This favors reemergence of Rocky Mountain spotted fever in the state of São Paulo, as these animals can play host to the Cayenne tick (Amblyomma cajennense), a vector of the bacteria that transmit this disease. The objective of this work was to perform anatomical and radiographic analyses on the teeth of capybaras to broaden knowledge on the morphology of this species, as scientific interest on capybaras has been growing owing to reemergence of Rocky Mountain spotted fever.Materials, Methods & Results: Six capybara carcasses from the state of São Paulo, Brazil, were taken to the Laboratory for Animal Anatomy of the School of Agricultural Sciences and Veterinary Medicine of UNESP - Jaboticabal for obtainment of heads by disarticulation of the cervical region. The heads were frozen at -18°C, and then sectioned medially with a band saw to avoid tissue overlap in radiographs. The head halves were radiographed in the Diagnostic Imaging Section at the Veterinary Hospital of UNESP-Jaboticabal in laterolateral projection. After taking the radiographs, the teeth were extracted from the dental arches using anatomical forceps and pliers, placed in 0.1% thymol, and kept at 4°C for up to 30 days. The teeth were dried using an air jet produced by a compressor, and placed in molds made of aluminum foil. The specimens were embedded in alternating layers of clear polymethylmethacrylate and liquid polymerization catalyst until each tooth was completely covered. After 24 h, the molds were removed, and the blocks were sectioned using a band saw. Transversal and longitudinal calcified tooth sections with a thickness of 1.5 mm were prepared. The sections were sanded using an automotive sander with 80-grit sandpaper, and then sanded by hand until a thickness of 0.12 mm was reached. The tooth fragments were removed from the resin, dehydrated in ethanol, clarified in xylene, and placed in a Petri dish containing glycerin for evaluation using a mesoscope and a negatoscope. Capybaras were found to have one incisor, one premolar, and three molar teeth in each dental hemiarch (superior and inferior). All teeth contained large, open roots. The root of the superior incisor is rostral to the root of the premolar tooth, and the root of the inferior incisor lies between the roots of the premolar and the first molar teeth. The inferior incisors are much larger than their superior counterparts, and their ends are chisel-shaped. The pulp cavity extends from the apical region to up to two-thirds of the longitudinal length of the tooth, and the enamel is arranged in layers. The roots of the four molar teeth are large and resemble several aggregated laminae arranged longitudinally - five laminae in the inferior molars, four laminae in the premolar, first and second molars, and 13 or 14 laminae in the third superior molar.Discussion: The dental formula of capybaras is similar to that of guinea pigs, chinchillas, and pacas, but different from that of agoutis. All teeth are aradicular as in guinea pigs and chinchillas because of the great tooth wear owing to feeding. In chinchillas and guinea pigs, the apex of the mandibular incisor tooth is located between the second and the third molar; in capybaras, it is located between the premolar and the first molar. The premolar and molar teeth of capybaras are similar to their counterparts in the paca and to the molars of elephants because they exhibit parallel internal laminae. The teeth of capybaras are similar to those of guinea pigs in terms of number and type of teeth, and similar to those of pacas and elephants regarding external morphology.

HE11 mode in water-filled hollow core Bragg fiber with a gold layer and dispersive materials

A recent analytical method is used to determine the spectral and amplitude sensitivities for HE11 mode in a hollow core Bragg fiber with or without a gold layer when the dispersion relations for all layers are considered. The fiber without a gold layer is made by a water core, surrounded by periodic reflector layers of polystyrene and polymethyl methacrylate with high and low refractive indices, respectively. The thicknesses of the cladding layers are calculated by using the quarter wave condition for two assumed initial bandgap wavelengths (λ0 = 0.5 μm and λ0 = 0.68 μm). The optical confinement for the HE11 mode in the core, at the minimum-loss wavelength, is increased over four orders (104) of magnitude when a high index material just before the outermost region of a hollow core Bragg fiber is replaced with a gold layer with an optimized thickness. Also, the amplitude sensitivity at the minimum-loss wavelength is increased for an optimized thickness of the gold layer.

ZnO Nanowall Networks for Sensor Devices: From Hydrothermal Synthesis to Device Demonstration

This paper reports the synthesis of ZnO nanowalls (NWLs) on various substrates by low cost and scalable hydrothermal approach targeting for flexible sensor device applications. Prototype flexible piezoelectric sensor devices using the synthesized ZnO NWLs were demonstrated through a transfer process. The roles of precursor chemical concentration and aluminum seed layer thickness in determining the morphology and the growth rate of the as grown ZnO NWLs were investigated. Effects of thermal annealing on the morphology and the crystalline quality of the NWLs were studied. To fabricate the sensor devices, ZnO NWL layers were transferred on to different substrates using thin Polymethyl methacrylate (PMMA) layer. Wafer scale transfer of thermally annealed ZnO NWLs to flexible substrates has been achieved. The demonstrated prototype devices can generate up to 300 mV of output voltage with external applied forces. Simulation model using COMSOL Multiphysics was developed to study the piezoelectric properties of the ZnO NWLs based devices. The simulation results agree well with the experimental data. The demonstrated ZnO NWLs based flexible devices are applicable for wearable nanodevices and motion sensors that will benefit from their large surface areas.

Experimental investigation on the ballistic resistance of polymer-aluminum laminated plates

An experimental investigation on four kinds of polymer-aluminum laminated plates impacted by blunt- and ogival-nosed projectiles was carried out. The polycarbonate (PC) layer (2 mm) and the polymethyl methacrylate (PMMA) layer (2 mm) were used to make an array with the AA2024-T4 layer (2 mm), respectively, constituting these double layered polymer-aluminum laminated plates with no adherence. To better understand the strength and ductility difference among these materials, quasi-static tensile tests were conducted for them. The impact tests of pure AA2024-T4 layer (3 mm) which has close areal density with the bi-layered plates were compared in ballistic resistance. In each impact test, the projectile was driven by a gas-powered gun at impact velocities above and below the ballistic limit velocity of the target plates, mainly ranging from 60–150 m/s. And the initial and residual velocities of the projectiles impacting the targets were measured by a Photron FASTCAM SA5 high-speed camera. Based on these results, the ballistic limit velocities of seven kinds of structures (including three kinds of different thickness aluminum layer) impacted by blunt- and ogival-nosed projectiles were obtained. And after the impact tests, the plastic deformation of the aluminum alloy in each bi-layered structure was measured.It is shown that the polymer layer order, nose shape and polymer mechanical behavior affects the performance of the polymer-aluminum laminated plates. The PC is much better than the PMMA in the bi-layer plates in terms of improving the ballistic resistance of the aluminum. Furthermore, the structures with the polymer placed in the impact side performed better than that in the back side for blunt-nosed projectiles, which is opposite to that for ogival-nosed projectiles. And the polymer-aluminum laminated plates with the PC placed in the impact side for blunt-nosed projectiles have advantages comparing with pure aluminum alloy at same mass in this study.

Electron beam induced removal of PMMA layer used for graphene transfer

We demonstrate the development of an effective technique to remove the poly methyl methacrylate (PMMA) layer used for transferring graphene synthesized by a chemical vapor deposition (CVD). This was achieved utilizing electron-beam bombardment and following developing processes, prior to the use of conventional organic solvents. Field-effect transistors were fabricated on the transferred graphene in order to explore their Dirac points and carrier motilities in the ambient condition - the results were then compared with those from the conventional wet chemical treatment. It was found that the Dirac points were located close to the zero gate bias when compared to those from the acetone and the acetic acid treatments. Most significantly, the field-effect mobility reached as high as 6770 cm2/Vs and 7350 cm2/Vs on average for holes and electrons, respectively, which is more than seven times improvement in comparison to conventional acetone treatments for CVD-grown graphene devices.

Patterned synthesis of ZnO nanorod arrays for nanoplasmonic waveguide applications

We report the patterned synthesis of ZnO nanorod arrays of diameters between 50 nm and 130 nm and various spacings. This was achieved by patterning hole arrays in a polymethyl methacrylate layer with electron beam lithography, followed by chemical synthesis of ZnO nanorods in the patterned holes using the hydrothermal method. The fabrication of ZnO nanorod waveguide arrays is also demonstrated by embedding the nanorods in a silver film using the electroplating process. Optical transmission measurement through the nanorod waveguide arrays is performed and strong resonant transmission of visible light is observed. We have found the resonance shifts to a longer wavelength with increasing nanorod diameter. Furthermore, the resonance wavelength is independent of the nanowaveguide array period, indicating the observed resonant transmission is the effect of a single ZnO nanorod waveguide. These nanorod waveguides may be used in single-molecule imaging and sensing as a result of the nanoscopic profile of the light transmitted through the nanorods and the controlled locations of these nanoscale light sources.

Soft thermal nanoimprint of PMMA doped with upconverter nanoparticles

Upconversion of low-energy photons into higher energy photons is a non-linear effect that can be strongly enhanced by increasing the intensity of impinging light. Such an enhanced intensity can also be achieved by near-field optical effects in photonic structures. In this paper, we investigate photonic structures in the form of linear gratings with varying periods realised in poly-methyl-methacrylate (PMMA) layers using soft stamps in a thermal nanoimprint process. Master structures were fabricated using e-beam lithography and reactive ion etching in silicon. These master structures were replicated into bi-layer polydimethylsiloxane (PDMS) stamps. PMMA layers with embedded β-NaYF4:25% Er3+ upconverter nanoparticles were applied to glass substrates using spin coating. The PDMS stamps were used to imprint the PMMA layer with very accurate pattern fidelity. The upconversion luminescence around 980nm was enhanced more than three times by the photonic structure under 1523nm laser excitation with 0.43±0.02W/cm2 irradiance, in comparison to a reference sample containing the same amount of upconverter material.

Effect of solvents on the morphology of PMMA films fabricated by spin-coating

Abstract A method to produce thin layer of PMMA (poly (methyl methacrylate) films by spin coating is reported. PMMA is dissolved in xylene, a mixture of MIBK-xylene and chloroform. Varying the PMMA concentration and spin-coating speeds controls the thickness of the PMMA films. Using chloroform as solvent evidenced thickness around 10 μm. This thickness is suitable for core of optical polymeric films. These PMMA films with lower roughness are treated with CHF3 plasma to produce the cladding. The morphology of PMMA films is analyzed by atomic force microscopy and scanning electron microscopy. Profilometry, metricon and contact angle analysis are associated with the effective parameters in roughness and their effect before and after plasma treatment. Gel permeation chromatography (GPC) is used for estimating molecular weights of PMMA.

Experimental and numerical characterization of a mid-infrared plasmonic perfect absorber for dual-band enhanced vibrational spectroscopy

Plasmonic perfect absorbers (PPAs) have promising properties to be utilized in molecular sensing and spectroscopy applications such as surface enhanced infrared absorption (SEIRA) and surface enhanced Raman spectroscopy (SERS). In order to employ these properties and demonstrate the great potential of PPAs, investigation and demonstration of PPA designs and their sensing applications are highly needed. In this context, we present the design, optical characterization, experimental realization and dual-band sensing application of a subwavelength PPA array for infrared detection and surface enhanced spectroscopy applications. We analyze the PPA to investigate the absorption spectra and the fine-tuning mechanism through the parameter sweep simulations and experiments. In order to understand the absorption mechanism, we investigate the charge and current density distribution maps with electric and magnetic field enhancement effects. Additionally, we demonstrate the potential usage and reliability of the proposed PPA by presenting the experimental results of the dual-band detection of a conformal polymethyl methacrylate layer with nanometer-scale thickness atop the PPA. According to the experimental and simulation results of this study, the proposed PPA can be utilized in multiband molecular detection and high sensitive spectroscopy applications.

200-fs mode-locked Erbium-doped fiber laser by using mechanically exfoliated MoS2 saturable absorber onto D-shaped optical fiber.

For the first time, we demonstrated the fabrication of mechanically exfoliated molybdenum disulfide (MoS2) samples deposited onto a D-shaped optical fiber. The MoS2 exfoliated flakes were deposited onto a stacked of 1.2 µm PVA (polyvinyl alcohol) and 300 nm PMMA (polymethyl methacrylate) layers and then transferred directly onto a side polished surface of D-shaped optical fiber with polishing length of 17 mm and no distance from the fiber core. The sample exhibited a high polarization performance as a polarizer with relative polarization extinction ratio of 97.5%. By incorporating the sample as a saturable absorber in the Erbium-doped fiber laser (EDFL), bandwidth of 20.5 nm and pulse duration of 200 fs were generated, which corresponded to the best mode-locking results obtained for all-fiber MoS2 saturable absorber at 1.5 µm wavelength.

Real Time Quantification of Phenolic Compounds in Oil and Gas Wells Produced Wastewater Using a QCM Sensor

Phenols (phenol, m-cresol, o-cresol and p-cresol) are contaminant compounds and due to its toxicity and persistence in the environment are listed in the Environmental Protection Agency as dangerous substances [1]; its presence in the environment is widely associated with wastewater effluents as is the produced water generated by oil and gas production. One of the systems that has been gaining importance to measure phenols in real time is the Quartz Crystal Microbalance (QCM). This technique comprises a thin quartz crystal sandwiched between two metal electrodes and senses the changes in frequency that suffers the quartz crystal when a certain amount of mass is deposited on its surface [3]. In order to improve the sensibility of compounds to measurement using a QCM have been used coatings on quartz crystal electrode surface, for example for phenols determination polymethylmethacrylate (PMMA) is used. The main objective of this research is to determine in real time and in continuous flow the concentration of phenolic compounds in produced water using the technique QCM with PMMA as coating on quartz crystal electrode surface. This work is conducted in three stages mainly: 1. Determination of a suitable layer of PMMA to use as coating, 2. Evaluation of the effect of the concentration of phenols, pH and flow rate in the measurements by QCM, 3. Comparison of sensitivity and time response obtained in the technique QCM with standard method by colorimetry.Results have shown that the PMMA films are more uniform when is used dichloroethane as solvent instead of chloroform and the stability and sensitivity in the measurements improve due to the vapor pressure of solvent that allows more dispersion of the polymer during spin coating, which is consistent with other authors [2]. Increase in the concentration of phenolic compounds, the flow rate and the pH increases the changes in frequency of the quartz crystal. Keywords : Quartz crystal microbalance, PMMA, phenols, produced water, real time. Mirmosheni, A., Oladegaragoze, A. Application of the quartz crystal microbalance for determination of phenol in solution. 2003. Sensors and Actuators, B: Chemical, Vol.98 (1), p. 28-36.Mohajerani, E. Morphological and thickness analysis for PMMA spin coated films. 2007. Journal of optoelectronics and advanced materials, Vol. 9 (12), p. 3901-3906.Reddy, S. Detection of phenol in aqueous solution using an AT-cut quartz thickness shear mode sensor. 2000. Materials Science and Engineering C, Vol. 12 (1), p. 23-28.

Real Time Quantification of Phenol in Aqueous Solutions Using a Quartz Crystal Microbalance

Phenol (C6H5OH) is an organic compound which is widely used in the industrial production of plastics, paints, rubber, paper, and soaps; However, due to its characteristics of toxicity and persistence in the environment is registered in the list of hazardous substances of the Environmental Protection Agency (EPA) [1,3]. One of the main effluents in which phenol is found are industrial wastewater by which the permissible limits established by the competent environmental authorities are reached, which causes serious problems in the health of people living in places nearby the points of water dump. There are several techniques and methods for determining phenol concentration in water. Conventional techniques include visible ultraviolet spectrophotometry (UV-VIS), High Performance Liquid Chromatography (HPLC), and Gas Chromatography coupled with Mass Spectrometry (GC-MS). These techniques, although characterized by their precision, require a sample pretreatment, high cost equipment and consumed long analysis times [1,3], which makes it difficult to obtain results in real time that allow the control in the concentration of phenol in water before of being poured. One of the systems that has gained importance for measuring organic compounds in water and in real time is the Quartz Crystal Microbalance (QCM). This technique comprises a thin quartz crystal sandwiched between two metal electrodes and senses the changes in frequency that suffers the quartz crystal when a certain amount of mass is deposited on its surface [1,3]. In order to improve the sensitivity of the QCM, there have been used coatings on quartz crystal electrode surface, for example for phenols determination polymethylmethacrylate (PMMA) is used. The main objective of this research is to determine in real time and in continuous flow the concentration of phenol in water using the technique QCM with PMMA as coating on quartz crystal electrode surface. This work is conducted in two stages mainly:1. Determination of a suitable layer of PMMA to use as coating on quartz crystal electrode surface, and 2. Determination of the concentration of phenol using the coating of PMMA prepared in the stage 1.Results have shown that the PMMA films are more uniform when is used dichloroethane as solvent instead of chloroform, and the stability and sensitivity in the measurements are improved due to its vapor pressure that allows more dispersion of the polymer during spin coating, which is consistent with other authors [2]. The coating of 0.2% w/v of PMMA/dicloroethane allowed the shortest response time with adequate sensitivity. Finally, increase in the concentration of phenol increases the changes in frequency of the quartz crystal in a linear way as shown in Figure 1, which is consistent with other authors [1]. Figure 1. Change of frequency changing concentration of phenol Keywords : Quartz crystal microbalance, PMMA, phenol, water, real time. Mirmosheni, A., Oladegaragoze, A. Application of the quartz crystal microbalance for determination of phenol in solution. 2003. Sensors and Actuators, B: Chemical, Vol.98 (1), p. 28-36.Mohajerani, E. Morphological and thickness analysis for PMMA spin coated films. 2007. Journal of optoelectronics and advanced materials, Vol. 9 (12), p. 3901-3906.Reddy, S. Detection of phenol in aqueous solution using an AT-cut quartz thickness shear mode sensor. 2000. Materials Science and Engineering C, Vol. 12 (1), p. 23-28. Figure 1

Absorption enhancement in graphene with an efficient resonator

Graphene can be utilized in designing tunable terahertz (THz) devices due to its tunability of sheet conductivity, suffering however with weak light-graphene interactions. In this paper, an absorption enhancement in graphene using a Fabry–Perot resonator is presented, and its performance has been numerically investigated using finite element method. The Fabry–Perot resonator consists of a continuous layer of graphene film sandwiched between the polymethyl methacrylate and silicon layers on an Au substrate which is covered by periodic gold ribbons. Numerical results show that the absorption performance is significantly enhanced by use of the Fabry–Perot resonator and a narrow band perfect absorption is achieved in THz regime. The influence of structural parameters on the absorption performance is further analyzed, and the absorption peak frequency can be flexibly controlled by adjusting the chemical potential of graphene which could be conveniently achieved by applying a bias voltage. The proposed structure here has a promising potential for developing advanced THz optics-electronics devices.

Multiplexed holograms in phenanthrenequinone–polymethylmethacrylate composite for microscopic applications

The conditions of multiplexed hologram recording in the layers of polymethylmethacrylate (PMMA) with a high content of photosensitive components, phenanthrenequinone (PQ), were analyzed theoretically and experimentally. The sequential record of up to 10 holograms onto a single photosensitive layer with a possibility of angular selection of holograms by their reconstruction was realized experimentally. The process of the alignment of values of the diffraction efficiency by selecting of exposing dose at each sequential hologram record was shown. The possibility to use multiplex holograms based on PQ-PMMA layers in application to 3D-microscopy was demonstrated.

Effect of stopping-layer-assisted boron-ion implantation on the electrical properties of graphene: Interplay between strain and charge doping

We report a new method of ion implantation for hole doping of graphene in which a layer of polymethyl methacrylate (PMMA) is used as a stopping layer to control the B-ion distribution in the graphene layer. This method is very useful for graphene doping in many aspects because it employs the ion energy comparable to what is commercially used in the semiconductor processes and strongly enhances the doping effect in contrast to the previous studies, resulting from B-ions-induced gating effect. PMMA/graphene/Cu-foil stacks were implanted with 35 keV B− ions to nominal fluences (ϕB) of 0.5–50 × 1010 cm−2 at room temperature. The electron/hole mobilities are sharply reduced by doping at ϕB = 0.5 × 1010 cm−2, but above this, they increase with increasing ϕB, as estimated from the Dirac curves. The Raman data and theoretical considerations suggest that the electrical properties of the B-doped graphene are governed by strain effect at low ϕB, but by charge-doping effect at high ϕB.

Nonlinear imaging microscopy for assessing structural and photochemical modifications upon laser removal of dammar varnish on photosensitive substrates.

The nonlinear optical microscopy (NLM) modalities of Multi-Photon Excited Fluorescence (MPEF) and Third Harmonic Generation (THG) have been combined in this work to characterize as a function of depth with micrometric resolution the type and extent of morphological and photochemical modifications that take place upon ultraviolet (UV) pulsed laser removal of a dammar varnish layer applied on a photosensitive substrate. The latter consists on a layer of the synthetic polymer poly-methyl methacrylate doped with a photosensitizer, the aromatic compound 1,4-di[2-(5-phenyloxazolyl)] benzene, that strongly fluoresces upon UV light illumination. A number of laser conditions for partial or total elimination of the varnish coating were explored, namely different wavelengths (266, 248 and 213 nm) and pulse durations, in the nanosecond, picosecond and femtosecond ranges. Changes in the MPEF signals upon laser ablation of the outermost varnish layer successfully signpost photochemical modifications of the varnish or of the photosensitive under-layer, and their dependence with the laser ablation parameters, i.e., wavelength and pulse duration. In turn, THG signals mark the presence of layer boundaries and the reduction by laser ablation of the thickness of the varnish coating. The obtained MPEF and THG data are complemented by morphological observation by optical microscopy and measurements of laser induced fluorescence and micro-Raman spectra of the samples before and after laser ablation at the selected laser irradiation conditions. The results acquired through these non-destructive NLM imaging techniques serve to understand the phenomena that are induced upon laser ablation and to determine the best operating conditions that ensure controlled removal of the varnish with minimal morphological and chemical modifications to the under-layers. This research is of direct application to the UV pulsed laser cleaning of paintings and demonstrates the potential of NLM as a novel assessment tool for non-destructive, on line monitoring of the laser cleaning process.