Decrease Of PL Intensity Research Articles

Tailoring of Visible to Near-Infrared Active 2D MXene with Defect-Enriched Titania-Based Heterojunction Photocatalyst for Green H2 Generation.

A wide solar light absorption window and its utilization, long-term stability, and improved interfacial charge transfer are the keys to scalable and superior solar photocatalytic performance. Based on this objective, a noble metal-free composite photocatalyst is developed with conducting MXene (Ti3C2) and semiconducting cauliflower-shaped CdS and porous Cu2O. XPS, HRTEM, and ESR analyses of TiOy@Ti3C2 confirm the formation of enough defect-enriched TiOy (where y is < 2) on the surface of Ti3C2 during hydrothermal treatment, thus creating a third semiconducting site with enough oxygen vacancy. The final material, TiOy@Ti3C2/CdS/Cu2O, shows a broad absorption window from 300 to 2000 nm, covering the visible to near-infrared (NIR) range of the solar spectrum. Photocatalytic H2 generation activity is found to be 12.23 and 16.26 mmol g-1 h-1 in the binary (TiOy@Ti3C2/CdS) and tertiary composite (TiOy@Ti3C2/CdS/Cu2O), respectively, with good repeatability under visible-NIR light using lactic acid as the hole scavenger. A clear increase of efficiency by 1.53 mmol g-1 h-1 in the tertiary composite due to NIR light absorption supports the intrinsic upconversion of electrons, which will open a new prospective of solar light utilization. Decreased charge-transfer resistance from the EIS plot and a decrease in PL intensity established the improved interfacial charge separation in the tertiary composite. Compared to pure CdS, H2 generation efficiency is 29.6 times higher on the noble metal-free tertiary composite with an apparent quantum efficiency of 12.34%. Synergistic effect of defect-enriched TiOy formation, creation of proper dual p-n junction on a Ti3C2 sheet as supported by the Mott-Schottky plot, significant NIR light absorption, increased electron mobility, and charge transfer on the conductive Ti3C2 layer facilitate the drastically increased hydrogen evolution rate even after several cycles of repetition. Expectantly, the 2D MXene-based heterostructure with defect-enriched dual p-n junctions of desired interface engineering will facilitate scalable photocatalytic water splitting over a broad range of the solar spectrum.

Fabrication of praseodymium-doped ceria (PDC) films by slurry spin-coating technique and its structural, morphological and optical properties

The current study is on the fabrication of PDC films prepared by slurry spin-coating technique for photoluminescence activity. At lower spin rates (1000 rpm), thicker and uniform PDC films were obtained. The structural evolution of the sintered PDC films on a dense alumina substrate was studied using Grazing Incidence X-ray diffraction (GIXRD) and Raman Spectroscopy. Crystallite size, microstrain, and dislocation density values remain almost the same with the increase in the coating cycles. The A568/A463 ratio for 3, 5, and 10 coating cycles are 0.52, 0.49, and 0.61, respectively. Surface roughness studies of PDC films using a 3D Noncontact Profilometer. The mean surface roughness values are 12.55, 13.74, and 22.25 μm for the 3rd,5th, and 10th coating cycles, respectively. Microstructure observation by Field Emission Scanning Electron Microscope (FE-SEM). The average thickness of the films for the 3rd, 5th, and 10th coating cycles are 50.93, 41.64, and 109.95 μm, respectively. The PDC films obtained on a dense alumina substrate were porous. FE-SEM micrographs showed a particle aggregation of several irregular and smaller grains, indicating the sintering activity of PDC films. Optical properties were studied using ultraviolet-visible (UV–Vis) absorption spectra and photoluminescence spectra (PLS). The band gap values slightly increased with the increase in the coating cycles. A decrease in PL intensity with an increase in the coating cycle is related to higher oxygen vacancy concentration. PDC films fabricated by the slurry spin-coating technique can be successfully used for optoelectronic applications.

Effect of Cr3+ doping on structural and optical properties of Eu3+ doped LaVO4 phosphor.

In this work, the Eu3+, Cr3+ doped and co-doped LaVO4 phosphors have been prepared through a high temperature solid-state reaction method. The powder XRD patterns of phosphors are very sharp and intense, which reflects a highly crystalline nature of phosphors. The XRD data were also refined by a Rietveld refinement method. The particle size of the phosphor samples lies in the sub-micron to micron range. The existence of La, Eu, Cr, V and O elements was verified by EDS spectra. The FTIR spectra show various absorption bands due to different vibrating groups. The optical band gap of the phosphor decreases on increasing concentration of Cr3+ ion. The photoluminescence excitation spectra of Eu3+, Cr3+ co-doped LaVO4 phosphor exhibit bands due to Eu3+ and Cr3+ ions. The Eu3+ doped LaVO4 phosphor exciting at 393 and 316 nm wavelengths gives intense red color at 614 nm due to the 5D0 → 7F2 transition of the Eu3+ ion. When the Cr3+ ion is co-doped in the Eu3+ doped LaVO4 phosphor the emission spectra contain emission bands due to Eu3+ and Cr3+ ions. The emission intensity of Eu3+ doped phosphor reduces due to energy transfer from Eu3+ to Cr3+ ions in presence of Cr3+ ions upon 393 and 386 nm excitations. The lifetime of the 5D0 level of Eu3+ ions decreases in the Eu3+, Cr3+ co-doped LaVO4 phosphor, which also reflects the energy transfer. The Eu3+, Cr3+ co-doped LaVO4 phosphor also produces a large amount of heat upon 980 nm excitation. Thus, the Eu3+, Cr3+ co-doped LaVO4 phosphors may be used for LEDs, solid state lighting and heat generating devices.

High stability and strong luminescence CsPbBr3-Cs4PbBr6 thin films for all-inorganic perovskite light-emitting diodes.

All-inorganic lead halide perovskite, characterized by its exceptional optical and electrical properties, is burgeoning as a potential optoelectronic material. However, the standalone CsPbBr3 component encounters several challenges including small exciton binding energy (≈40 meV) and long charge diffusion length, giving rise to low photo-luminescence quantum-yield (PLQY); ion migration leads to instability in device operation, hindering device operation and potential development. To circumvent these limitations, our research endeavors to construct a novel core-shell structure that transforms the continuous [PbX6]4- octahedron into an isolated octahedral structure. We introduce the Cs4PbBr6 phase with 0D structure to passivate the vacancy defects in CsPbBr3, thereby suppressing ion migration and enhancing the luminescence intensity and stability. Our methodology involves fabricating dense CsPbBr3-Cs4PbBr6 composite films using a co-evaporation method, wherein the molar ratio of CsBr and PbBr2 is precisely adjusted. The films are subsequently rapidly annealed under ambient air conditions, and the effects of different annealing temperatures and annealing times on the CsPbBr3-Cs4PbBr6 films were investigated. Our results demonstrate significantly improved stability of the annealed films, with a mere 15% decrease in PL intensity after 100 days of storage under ambient air conditions at 48% relative humidity (RH). Based on this thin film, we fabricated all-inorganic structure Ag/N-Si/CsPbBr3-Cs4PbBr6/NiO/ITO light emitting diodes (LEDs), the devices have a low turn-on voltage VT ∼3 V and under unencapsulated, ambient air conditions, it can operate continuously for 12 hours under DC drive with only 10% attenuation. The results we obtained open up the possibility of designing and developing air-stable perovskite LEDs.

Remarkable photoluminescence enhancement and tuning in Eu/CdS co-doped chloroborosilicate glass-ceramics

The effect of heat treatment was studied on Eu/CdS co-doped chloroborosilicate glass having a new composition 37.8SiO2–27B2O3–18BaO–3.6K2O–3.6Al2O3–10BaCl2 (mol%) recently developed in our group. The base glass has been proven to be a suitable host for various rare-earth ions and metallic nanoparticles, also upon controlled crystallization, because it has the potential to yield low-phonon energy (350 cm−1) BaCl2 crystals. The glasses were heat treated at 650 °C for several time durations. Transmission electron microscopy (TEM) revealed the presence of CdS quantum dots (QDs) and BaCl2 crystals in the heat-treated glasses. X-ray diffraction studies confirmed the formation of glass-ceramics, with the presence of BaCl2-based phases. When heat-treated, all the Eu/CdS co-doped glasses showed an intense enhancement in Eu3+/Eu2+ emissions up to 30 or 40 h of heat treatment, followed by a gradual decrease. The initial increase is due to the formation of low-phonon energy BaCl2-based crystalline phases as well as the generation and growth of CdS QDs at elevated temperature. The subsequent decrease in PL intensity is attributed to the concentration quenching effect of the QDs. The rate of enhancement was significantly higher when glasses formed opaque glass-ceramics due to the change in environment of the Eu ions and scattering effect. The maximum intensity enhancement due to the CdS co-doping and glass crystallization was observed to be 400 times as compared to the non heat-treated glass containing the same amount of Eu. This enhancement is quite remarkable in rare-earth/semiconductor co-doped glasses and can be useful in various photonic applications.

Formation of Bi−Bi Dimers in Heavily Bi -Doped Lead Halide Perovskites: Origin of Carrier Density Saturation

Heterovalent $\mathrm{Bi}$ doping in lead halide perovskites (LHPs) is of particular interest in recent research to improve the electronic and optoelectronic properties. In experiments, the incorporation of $\mathrm{Bi}$ not only converts the conductivity type of crystals from p type to n type, leading to the significant enhancement of charge-carrier concentration, but also results in the appearance of near-infrared photoluminescence (NIR PL) along with the decrease of band-edge PL intensity. However, with a high concentration of $\mathrm{Bi}$ doping, the carrier concentration exhibits a saturated tendency and the intensity of NIR PL decreases abnormally. The origins behind these interesting phenomena are not yet well understood. Herein, based on first-principles calculations, we demonstrate that $\mathrm{Bi}$ dimers form n type and intrinsic LHPs with a high concentration of $\mathrm{Bi}$ doping. They act as effective n-type limiting defects, and hence, cause carrier saturation in experiments. Moreover, the NIR PL arising from the ${\mathrm{Bi}}_{\mathrm{Pb}}$ defect is suppressed due to the density conversion of isolated ${\mathrm{Bi}}_{\mathrm{Pb}}$ defects to $\mathrm{Bi}$ dimers when $\mathrm{Bi}$ is heavily doped. Meanwhile, nonradiative recombination is also promoted due to the deep charge-state transition level introduced by the $\mathrm{Bi}$ dimer. Our work not only reveals the mechanism of highly concentrated $\mathrm{Bi}$ limiting the electronic and optical properties of LHPs, but also suggests the precise control of $\mathrm{Bi}$ doping in electronic and photovoltaic applications.

α-Fe2O3/Cu2O heterostructure: Brief characterization and kinetic aspect of degradation of methylene blue

The α-Fe2O3/Cu2O heterostructure (HS) was prepared via the hydrothermal precipitation method and used in the kinetic study of the methylene blue (MB) photodegradation. The samples were subjected to the photoluminescence spectroscopy (PL) to evaluate the e/h recombination rate and the results showed a significant decrease in PL intensity of the heterostructure with respect to the individual semiconductors. The band gap energy of 2.28 eV for the single Fe2O3 semiconductor was red-shifted to 1.95 eV by introducing Cu2O species. EDX analysis of the heterostructure showed 74.36% (65.66% atomic%) Cu and 22.21% (22.32 atomic%) Fe in weight%. The heterostructure showed an increased photocatalytic activity towards MB molecules with respect to the individual systems. The degradation process obeyed the first order Hinshelwood kinetic model and an apparent first-order rate constant of 0.025 min−1 with a t1/2 value of 27 min was obtained. The degradation extent of MB was confirmed by the chemical oxygen demand (COD) method that of results confirmed about 90% of MB molecules can be removed during the photodegradation process in the applied conditions.

Some radiation effects in II-VI quantum dots

The effect of electron irradiation (E=0.6-1.8 MeV) on the optical characteristics (photoluminescence, PL) of CdTe/ZnTe structures with quantum dots, QDs, was investigated in the temperature range from 4.2 to 250 K. The data on the influence of irradiation on the temperature dependence of PL intensity, energy position and PL line width, W, from QDs were obtained. The narrowing of PL band and the blue shift of the QD peak position are explained by quenching of the low energy component connected with larger QDs. A slight decrease in PL intensity for both QDs and the buffer ZnTe layer as well as a sharp drop in PL intensity for 1 ML CdTe quantum wells, QWs, and fragments accompanied by a change in the activation energy of the PL quenching is explained by the radiation defects localized near the QD interface. The obtained results show that under e-beam irradiation QDs are more stable than QWs, which is in agreement with our previous investigations.

Effect of cerium doping on optical and scintillation properties of transparent YAG ceramic

Abstract Cerium doped transparent YAG ceramics 0.15–2 at% cerium) were prepared using nano-powder technique and vacuum sintering. The effective solubility limit of cerium in YAG was found to lie between 1.0 and 1.5 at%. The PL intensity increases with the cerium content and attains a maximum for 1.0 at% doping. Lifetime of PL is not very sensitive to cerium content, however, a slight decrease in the life-time from 66 ns to 55 ns was observed with increase in cerium content from 0.15 to 2.0 at%. This decrease in PL intensity and life-time is attributed to concentration quenching for the YAG ceramics with cerium content higher than 1.0 at%. A red-shift in the PL peak position was observed and attributed to the local symmetry distortion in YAG matrix.

Temperature-dependent photoluminescence properties of [HC(NH2)2]PbI3 perovskite nanorods

Organic-inorganic lead iodide perovskite is an ideal candidate material for high performance photovoltaic and optoelectronic devices. In this paper, we synthesize hexagonal formamidinium lead iodide CH(NH2)2PbI3 (δ-FAPbI3) perovskite nanorods by a simple chemical solution method, the δ-FAPbI3 perovskite nanorods are then converted to black α-FAPbI3 with photoluminescence emission. Morphology and crystal structure of the FAPbI3 perovskite nanorods are characterized. Temperature-dependent photoluminescence of the α-FAPbI3 perovskite nanorods shows that near band edge emission blue-shifts when the temperature increases from 10K to 120K, then the emission band demonstrates a sudden redshift near 150K due to phase transition from tetragonal phase to cubic phase, and the emission band blue-shifts again from 150K to room temperature. The PL intensity decrease exponentially with the increase of the temperature. Temperature coefficients of the band gap and thermal activation energies of α-FAPbI3 perovskite nanorods are fitted from the temperature-dependent PL spectra.

Lanthanum ions-induced synthesis of ZnO nanostructures from zinc foil: Morphology change and photocatalytic activity

High-density aligned ZnO nanorod array film was synthesised by hydrothermal oxidation of zinc foil in a mixture including n-butylamine and lanthanum nitrate aqueous solution. The shape of ZnO nanostructure was strongly associated with the amount of lanthanum ions, which provided a valuable way to control the rate of nucleation and growth of ZnO. HRTEM, XRD and XPS analysis confirmed that the La3+ had been doped into ZnO lattice, which led to the red shift of the absorption edges and the decrease of PL intensity. The photocatalytic studies showed that the ZnO nanorod array film exhibited superior photocatalysis for the degradation of both methyl orange and methylene blue solutions due to its exposed crystal plane, density and the defects on the surface.

Combined EPR and ODMR study of Ce3+ optical emitters in yttrium aluminium garnet

Electron paramagnetic resonance (EPR) was detected in the ground state of Ce3+ ions in YAG:Ce single crystals by monitoring the intensity of photoluminescence under nonresonant excitation. The photoluminescence intensity was found to increase strongly in magnetic field at liquid helium temperature. The optically detected magnetic resonance (ODMR) effect was of the order of percents and corresponded to resonance decrease in the luminescence intensity. ODMR correlated with the conventional EPR spectra of Ce3+ ions, which occupy the dodecahedral Y3+ sites in the YAG crystal lattice. The increase of the PL intensity in magnetic field was concluded to be caused by Boltzmann distribution between spin sublevels of the ground state of Ce3+ ions. The ODMR tend to equalize the populations of levels in resonance and results to a decrease of PL intensity. Different types of Ce3+ centres characterized by the presence of nearby antisite defects were observed, which should be taken into account in applications of single ion spectroscopy based applications of YAG:Ce.

Ultrasonic-assisted synthesis of Ce doped cubic–hexagonal ZnTiO3 with highly efficient sonocatalytic activity

Ce doped ZnTiO3 as a novel catalyst with highly efficient and stable sonocatalytic activity was synthesized via an ultrasound-assisted sol–gel method using non-ionic surfactant Pluronic F127 as structure directing agent. Synthesized samples were characterized by using various techniques, such as XRD, TEM, SEM, EDX, ​XRF, BET, DRS, and PL, and their sonocatalytic activity studied toward degradation of p-Nitrophenol as a model organic compound. The synthesized mesoporous Ce/ZnTiO3 had mixed cubic–hexagonal phase with large surface area (118.2 m2 g–1) and narrow pore size distribution (4.9nm). The effects of cerium concentration, calcination temperature, and calcination time on the structure and the sonocatalytic activity of Ce/ZnTiO3 were studied in detail. XRD results were suggested that the relation between the phase structure and the catalytic activity is considerable. Significant decrease in band-gap and PL intensity was observed with increasing the cerium concentration in the ZnTiO3. It became clear that the Ce/ZnTiO3 (0.81mol%) shows high sonocatalytic activity compared with pure ZnTiO3 and other Ce/ZnTiO3 samples as well as commercial TiO2-P25. The possible mechanism for the enhanced sonocatalytic activity of Ce/ZnTiO3 was discussed in details. The electrical energy consumption was also considered during sonocatalytic experiments.

Effect of etching time and illumination on optical properties of SiNWs elaborated by Metal Assisted Chemical Etching (MACE) for organic photovoltaic applications

Using Ag-assisted chemical etching technique, vertical silicon nanowires (SiNWs) arrays on n-type (001) substrates has been prepared with different conditions such as etching time and illumination condition. A photoluminescence measurement at room temperature has shown a decrease of PL intensity when decreasing etching time. These results are attributed to the decrease of SiNWs density and reduction of laser capture surface. The presence of defect states lead to a non-radiative recombination. Indeed, the blue shift observed when using a low etching time is due to the confinement effect. Using a low etching time, illumination condition does not vary SiNWs density. The optimal experimental condition for photovoltaic application is observed after deposition of Poly (3-hexylthiophene-2,5-diyl) P3HT into the different silicon substrates prepared. An important charges transfer between P3HT and SiNWs is observed for high etching time (120min under illumination). A blue shift is due to the presence of defects and electric field.

PVA assisted low temperature anatase to rutile phase transformation (ART) and properties of titania nanoparticles

Anatase to rutile phase transformation (ART) of titania nanoparticles is observed at very low temperature (180 °C) just by introducing polyvinyl alcohol (PVA) during co-precipitation followed by hydrothermal synthesis. The detailed investigations pertaining to the structural, optical and electrochemical properties of the nanosized titania and titania/PVA nanohybrid has been carried out. The crystallite size and crystal structure is confirmed using X-ray diffraction (XRD). Transmission electron microscopic (TEM) image reveals formation of spherical NPs in both the cases. Identification of functional groups is done using Fourier transform infrared spectroscopy (FTIR). The photoluminescence studies showed that emission slightly shifts towards higher wavelength side with remarkable decrease in intensity for TiO2/PVA nanocomposite (rutile samples). The remarkable decrease in PL intensity in TiO2/PVA nanocomposite (rutile samples) is explained considering the surface passivation during growth process. Ion transportation is monitored via Cyclic voltammetric (CV) and Electrochemical Impedance Spectroscopy (EIS) measurements. A significant enhancement of peak cathodic current in case of nanocomposite modified electrode is observed. It is assumed that TiO2/PVA (rutile) nanoparticles provided the conducting path for the electrons and hence enhanced the electrochemical reaction.

Synthesis and characterization of quantum dot sensitized solar cell based on PMOT@ CdTe @TiO2 core shell nano structures

Semiconductor sensitized solar cell based on poly (3-methoxy thiophene) (PMOT) @CdTe@ TiO2 was designed where TiO2 is in core and CdTe acts as an electronic mediator, which facilitates the transfer of electrons from PMOT to CdTe shells and then to TiO2 core. Effect of annealing and TiO2 content on the optoelectronic properties of PMOT@CdTe@TiO2 core shell was studied. Thermal annealing enhanced the efficiency of PMOT@CdTe@TiO2 from 0.80% to 1.9% because it reduces the distances between the molecules. The optimum TiO2 content and annealing temperature for solar cell efficiency was 20% and 250°C respectively at which the photovoltaic parameters of the cell were Voc=0.88V, Jsc=3.6mA/cm2, FF=0.62 and efficiency=1.97%. The absorption in the visible region was enhanced after sensitization of TiO2 with CdTe which was further enhanced on capsulation the CdTe@TiO2 with PMOT shell. The significant decrease in PL intensity for PMOT@ CdTe @TiO2 core shell with rise in temperature was observed till 250°C, after which the intensity was, increased which confirmed the optimum temperature for charge transfer is 250°C. X-ray diffraction studies confirmed the crystallinity of the composite film was increased with annealing temperature.

Scintillation properties of Ce3+ doped SiO2-Al2O3-Gd2O3 glass

Scintillation glass is an attractive material due to its many advantages including low-cost and easy-manufacturing compared with single crystal. However the low density of glass scintillator restricts its applications. The introduction of heavy components such as PbO and Bi2O3 allows the density of the glass to be easily increased to more than 6.0 g/cm3 which is desirable for most applications. However, it is usually accompanied with a dramatic decrease in the luminescence response of Ce3+ ions. Although Gd2O3 based glass has a relatively high light yield, it is far below the high silica glass. In order to explain why the luminescent efficiency of Ce3+ doped glass with low density is high while that with high density is low, a glass-forming region of SiO2-Al2O3-Gd2O3 ternary system is achieved by high-temperature melt-quenching method. Ce3+doped SiO2-Al2O3-Gd2O3 and SiO2-Al2O3-Gd2O3-Ln2O3 (Ln=Y, La, Lu) scintillation glasses are prepared at reducing atmosphere. Their optical and scintillation properties are investigated. The results show that the content of Gd2O3 can reach as high as 30% mol without phase separation. In addition, the UV cut-off position is red-shifted, PL intensity decreases and decay time reduces from 70 to 37.6 ns with increasing the Gd2O3 concentration. After Lu2O3, La2O3, Y2O3 are added in the glass, the UV cut-off position is red-shifted and PL intensity decreases. Moreover the UV cut-off position is in the order of La&gt;Y&gt;Lu and the decay time is in the order of La2O3 is more than 10% mol, X-ray excited luminescence light emission intensity reduces from 61% of BGO to 13% of BGO. With the UV cut-off position red-shifted, the bandgap of glass becomes narrow, resulting in the 5 d level of Ce3+ ions gradually approaching to the conduction band and the 5 d electrons easily combining with the holes in the glass through the conduction band. Namely, charge transferring quenching occurs. This is the reason why the PL intensity and decay time both decrease. It can also explain why the luminescent efficiency of Ce3+ doped glass with low density is high while that with high density is low.

Photoluminescence quenching of Zirconia nanoparticle by surface modification

Zirconia nanoparticles (ZrO2-NPs) of size ∼10nm have been synthesized using hydrothermal method. ZrO2-NPs annealed at high temperature (400–850°C) exhibits a better crystallinity along with phase transformation. The PL intensity of ZrO2-NPs found to be annealing temperature dependent due to the change in crystallinity and surface defects. The ZrO2-NPs have also been synthesized in the presence of surfactants i.e. sodium dodecyl sulfate (SDS). The presence and interaction of ZrO2-NPs with surfactant has been verified using FTIR study. Optical studies showed significant reduction in PL intensity of ZrO2-NPs on surface modification. The decrease in PL intensity has been attributed to the passivation of ZrO2-NPs surface defects by surfactant molecules. The outcomes of the study pave the way to explore these ZrO2-NPs for optical sensors.

Influence of Preliminary Plasma Processing on Luminescent Properties of Porous Silicon

Measurements of radiative properties of porous silicon after compression plasma treatment have been carried out. Significant increase of photoluminescence intensity and blue shift of spectra have been observed on studied samples in comparison with porous layers formed on monocrystalline silicon without preliminary plasma treatment. An influence of long storage of plasma modified porous silicon layer on the intensity and spectral composition of photoluminescence has been checked. A rise of PL intensity during first moth of storage and following decrease of PL intensity in the next three months has been observed. Mechanisms of changes in a spectral composition of PL and alterations of PL intensity during storage have been discussed.

Surface modification of Makrofol-DE induced by α-particles

In the present work, Makrofol DE samples were irradiated with different doses of alpha particles. The optical and mechanical modifications in the alpha-irradiated Makrofol samples as a function of alpha irradiation time have been investigated. Different characterization techniques, UV–vis spectroscopy, photoluminescence spectroscopy and Vickers micro hardness tester have been used. UV–vis spectra of bombarded samples reveal that the optical absorption increases with increasing the irradiation time. The direct and indirect optical band gap was found to decrease from 3.4 and 2.81 eV for pristine sample to 3.1 and 2.35 eV for that bombarded with alpha particles at the highest irradiation time (15 h), respectively. The number of carbon atoms per conjugated length (N) and the number of carbon atoms per cluster (M) have been estimated. An increase in both N and M with increasing the irradiation time was noticed. A remarkable decrease in PL intensity with increasing the alpha irradiation time was observed. This decrease is attributed to ion beam-induced change in molecular structure and/or defects in the modified layer. The surface hardness for unmodified and modified polymeric material has been studied.