near-UV Spectral Region Research Articles

Magnetic Field Information in the Near-ultraviolet Fe ii Lines of the CLASP2 Space Experiment

We investigate theoretically the circular polarization signals induced by the Zeeman effect in the Fe ii lines of the 279.3–280.7 nm spectral range of the CLASP2 space experiment and their suitability to infer solar magnetic fields. To this end, we use a comprehensive Fe ii atomic model to solve the problem of the generation and transfer of polarized radiation in semiempirical models of the solar atmosphere, comparing the region of formation of the Fe ii spectral lines with those of the Mg ii h and k and the Mn i resonance lines. These are present in the same near-ultraviolet (near-UV) spectral region and allowed the mapping of the longitudinal component of the magnetic field (B L) through several layers of the solar chromosphere in an active region plage. We compare our synthetic intensity profiles with observations from the IRIS and CLASP2 missions, proving the suitability of our model atom to characterize these Fe ii spectral lines. The CLASP2 observations show two Fe ii spectral lines at 279.79 and 280.66 nm with significant circular polarization signals. We demonstrate the suitability of the weak-field approximation applied to the Stokes I and V profiles of these Fe ii lines to infer B L in the plage atmosphere. We conclude that the near-UV spectral region of CLASP2 allows us to determine B L from the upper photosphere to the top of the chromosphere of active region plages.

Estimation of chromophoric dissolved organic matter and non-algal particulate absorption coefficients of seawater in the ultraviolet by extrapolation from the visible spectral region.

Extending the capabilities of optical remote sensing and inverse optical algorithms, which have been commonly focused on the visible (VIS) range of the electromagnetic spectrum, to derive the optical properties of seawater in the ultraviolet (UV) range is important to advancing the understanding of various optical, biological, and photochemical processes in the ocean. In particular, existing remote-sensing reflectance models that derive the total spectral absorption coefficient of seawater, a(λ), and absorption partitioning models that partition a(λ) into the component absorption coefficients of phytoplankton, aph(λ), non-algal (depigmented) particles, ad(λ), and chromophoric dissolved organic matter (CDOM), ag(λ), are restricted to the VIS range. We assembled a quality-controlled development dataset of hyperspectral measurements of ag(λ) (N = 1294) and ad(λ) (N = 409) spanning a wide range of values across various ocean basins, and evaluated several extrapolation methods to extend ag(λ), ad(λ), and adg(λ) ≡ ag(λ) + ad(λ) into the near-UV spectral region by examining different sections of the VIS as a basis for extrapolation, different extrapolation functions, and different spectral sampling intervals of input data in the VIS. Our analysis determined the optimal method to estimate ag(λ) and adg(λ) at near-UV wavelengths (350 to 400 nm) which relies on an exponential extrapolation of data from the 400-450 nm range. The initial ad(λ) is obtained as a difference between the extrapolated estimates of adg(λ) and ag(λ). Additional correction functions based on the analysis of differences between the extrapolated and measured values in the near-UV were defined to obtain improved final estimates of ag(λ) and ad(λ) and then the final estimates of adg(λ) as a sum of final ag(λ) and ad(λ). The extrapolation model provides very good agreement between the extrapolated and measured data in the near-UV when the input data in the blue spectral region are available at 1 or 5 nm spectral sampling intervals. There is negligible bias between the modeled and measured values of all three absorption coefficients and the median absolute percent difference (MdAPD) is small, e.g., < 5.2% for ag(λ) and < 10.5% for ad(λ) at all near-UV wavelengths when evaluated with the development dataset. Assessment of the model on an independent dataset of concurrent ag(λ) and ad(λ) measurements (N = 149) yielded similar findings with only slight reduction of performance and MdAPD remaining below 6.7% for ag(λ) and 11% for ad(λ). These results are promising for integration of the extrapolation method with absorption partitioning models operating in the VIS.

Molecular Modulation by σ Conjugated Spacer Enables Efficient Ultraviolet/Deep-Blue Emissive Organic Light-Emitting Diodes

Phenanthroimidazole (PI) has great proficiency to design efficient near UV deep blue emitting materials due to its bipolarity behavior. The tuning of N1 and C1 centers of the PI further reveals the improvement of the optical and electronical properties. Thorough investigation is also executed to explore the influence of the alkyl chain on the optical and electroluminescence (EL) properties of these emissive materials. The incorporation of the alkyl chain in the materials can tune the optical properties, leading to better solid state emission and enhancement of the photoluminescence quantum yield (PLQY) of thin film (∼74%) as compared to solution (∼65%). The EL spectra were also exhibited between 395 and 420 nm (in the near-UV spectral region). Furthermore, for boosting of the device efficiency and color purity, the OLED device is fabricated by doping CBP as host matrix. Selectively, CBP is used as a host because of the similar energy level (HOMO and LUMO) of the synthesized emitters which assist efficient charge trapping. Predominantly, the emitters in OLED device blended with 0.5 wt % concentration achieved brilliant device efficiency and luminance properties. Among all the synthesized fluorophores, PIPP (0.5 wt %) doped OLED device showed 4.4% maximum external quantum efficiency (EQEmax), 1202 cd/m2 highest luminance, 2.2 lm/W power efficiency (PE), 2.7 cd/A current efficiency (CE) with Commission International de L’Eclairage (CIE) coordinates x = 0.17, y = 0.10 (nearer the NTSC standard value).

Refractory Plasmonic Hafnium Nitride and Zirconium Nitride Thin Films as Alternatives to Silver for Solar Mirror Applications.

Harnessing solar energy by employing concentrated solar power (CSP) systems requires materials with high electrical conductivity and optical reflectivity. Silver, with its excellent optical reflectance, is traditionally used as a reflective layer in solar mirrors for CSP technologies. However, silver is soft and expensive, quickly tarnishes, and requires a protective layer of glass for practical applications. Moreover, supply-side constraints and high-temperature instability of silver have led to the search for alternative materials that exhibit high solar and infrared reflectance. Transition metal nitrides, such as titanium nitride, have emerged as alternative plasmonic materials to gold starting from a spectral range of ∼500 nm. However, to achieve high solar reflection (∼320-2500 nm), materials with epsilon-near-zero starting from the near-ultraviolet (UV) spectral region are required. Here, we show the development of refractory epitaxial hafnium nitride (HfN) and zirconium nitride (ZrN) thin films as excellent mirrors with a solar reflectivity of ∼90.3% and an infrared reflectivity of ∼95%. Low-loss and high-quality epsilon-near-zero resonance at near-UV (∼340-380 nm) spectral regions are achieved in HfN and ZrN by carefully controlling the stoichiometry, leading to a sharp increase in the reflection edge that is on par with silver. Temperature-dependent reflectivity and dielectric constants are further measured to demonstrate their high-temperature suitability. The development of refractory epitaxial HfN and ZrN thin films with high solar and infrared reflectance makes them excellent alternative plasmonic materials to silver and would pave their applications in CSP, daytime radiative cooling, and others.

Regulating the surface of anion-doped TiO2 nanorods by hydrogen annealing for superior photoelectrochemical water oxidation

Dedications to achieve the highly efficient metal oxide semiconductor for the photoelectrochemical water splitting system have been persisted to utilize the TiO2 as the promising photoanode material. Herein, we report notable progress for nanostructured TiO2 photoanodes using facile sequential one-pot hydrothermal synthesis and annealing in hydrogen. A photocurrent density of 3.04 mA·cm−2 at 1.23 V vs. reversible hydrogen electrode was achieved in TiO2 nanorod arrays annealed in hydrogen ambient, which is approximately 4.25 times higher than that of pristine TiO2 annealed in ambient air. 79.2% of incident photon-to-current efficiency at 380 nm wavelength demonstrates the prominence of the material at the near-UV spectral range region and 100 h chronoamperometric test exhibits the stability of the photoanode. Detailed studies regarding crystallinity, bandgap, and elemental analysis provide the importance of the optimized annealing condition for the TiO2-based photoanodes. Water contact angle measurement displays the effect of hydrogen annealing on the hydrophilicity of the material. This study clearly demonstrates the marked improvement using the optimized hydrogen annealing, providing the promising methodologies for eco-friendly mass production of water splitting photoelectrodes.Graphical

Chiroptical detection of self-aggregating fluorescent rhodamine conjugates: Mistakes and prospects.

Fluorescent conjugation can be considered as the chromophoric derivatization of the target, and as such, it may provide additional structure-related information available by using circular dichroism (CD) spectroscopy. In this essay, peculiar CD spectroscopic data reported earlier for thyroid hormone-rhodamine conjugates have been re-evaluated. Contrary to the original proposal on the intramolecular folding of the labelled hormone, the bisignate motif observed in the CD spectrum is a clear evidence of dye-dye intermolecular chiral exciton coupling, indicating supramolecular self-association of the conjugates. This anomalous solution behaviour undermines the credibility of experimental results reported with such conjugates still being used in the laboratory practice. The extension of routine far-ultraviolet (UV) CD spectroscopic scans of chiral fluorophore conjugates into the near-UV and visible spectral region is strongly recommended.

Phosphorescence of Liquid Oxygen Excited at Cooperative Transitions in the Visible Spectral Region

Phosphorescence of liquid oxygen under excitation at cooperative transitions of О2–О2 molecular oxygen complexes is studied using direct optical excitation by LED arrays emitting in the near-UV and visible spectral regions at wavelengths partially or completely coinciding with the absorption lines of the molecular complexes.

Al-doped ZnO transparent conducting oxide with appealing electro-optical properties – Realization of indium free transparent conductors from sputtering targets with varying dopant concentrations

The objective of this work is to provide high quality indium free transparent and conducting oxide film in which ZnO is the primary component and Al is the only dopant. A range of Al-doped ZnO (AZO) transparent conductors has been realized from the developed AZO sputtering targets with varying dopant concentrations with content of the dopant material Al2O3 added in the range 0.5–5.0 wt.%. X-ray diffraction, Raman spectroscopy, AFM measurements, and elemental analyses reveal promising material properties. The sheet resistance of 2.3 Ω/sq, visible light transmittance over 90 %, and figure of merit of 75.9 mΩ–1 are the optimal electro-optical characteristics of AZO thin films. The resistivity of AZO films is dependent on the dopant concentrations with the lowest value estimated to be 1.66 × 10–4 Ω cm. A comparison of the figure of merit of AZO films with that of ITO suggests application potential of AZO as transparent conducting oxide. High transparency effect of AZO films in the near-UV spectral region is limited by the strong fundamental absorption. The hypsochromic shift of this onset of band-to-band absorption accentuates beyond 1.0 wt.% of Al2O3, which is primarily ascribed to the Moss-Burstein effect in this degenerate semiconductor. The bulk plasmon frequencies fall in the near infrared region where transmittance curves of AZO films completely differ from that of ZnO. A significantly high free carrier absorption in the near infrared suggests formation of free electron gas upon doping. With abundance of free electrons and low dielectric loss, AZO may serve as a promising infrared plasmonic material.

Eu3+ complex/polymer films for light-emitting diode applications

Eu3+ complexes exhibit potential to be applied as the red emitter component of white-light-emitting LEDs due to their intense absorption in the near-UV spectral region and intense red-light emission. However, the main problem concerning this application is the poor photostability usually displayed by Eu3+ complexes. To overcome such issue, in this study, transparent films of [C26H56N]+[Eu(dbm)4]- (C26H56N+ is the didodecyldimethylammonium cation and dbm− is 1,3-diphenyl-1,3-propanedione anion) dispersed in poly (methyl methacrylate) (PMMA) were used to coat commercial near-UV emitting LEDs in order to fabricate red-light-emitting LED prototypes. This Eu3+ complex was selected due to its high 5D0 state quantum efficiency (51 %) and absence of water molecules in its structure; the polymer, in its turn, had the purpose to protect the complex from photodegradation. Several PMMA films were produced by the addition of different amounts of complex, i.e., 0.1%, 0.25%, 0.5%, and 1% (w/w). All the films feature the usual Eu3+ emission in the red spectral region and the 5D0 state quantum efficiency enhances as the complex amount increases from 0.1% to 0.5%, while for the 1%, a decrease was observed. Thus, the 0.5% film was adhered with a cyanoacrylate glue on the top of a near-UV LED chip and the prototype exhibited the typical Eu3+ red emission with lower blue contribution coming from the UV LED chip, indicating that UV photons are efficiently converted by the film. Finally, the LED prototype performance was monitored over 26 h, and the emission intensity decreased 35% after 17 h, and from then on, it kept constant. A second LED prototype was manufactured using 5% (w/w) of the complex blended only with the cyanoacrylate glue and it displayed an intensity decrease of 50% after 26 h, confirming the role of PMMA in protecting the Eu3+ complex from photodegradation.

Inherent optical properties and particle characteristics of the sea-surface microlayer

The sea-surface microlayer (SML) is known to have physical, chemical, and biological properties that are distinctly different from the underlying subsurface water (USW). However, only a few studies in the past reported on measurements of the optical properties of the SML and were limited to light absorption. In this study we present results for the main inherent optical properties (IOPs), the spectral absorption coefficients and the volume scattering function, as well as particle size distribution (PSD), from measurements of the SML and USW in contrasting ocean environments with near-surface chlorophyll-a concentration ranging from 0.06 mg m−3 in waters off Hawaiian Islands to 1 mg m−3 in the Santa Barbara Channel. Our observations also included prominent surface slick conditions associated with a dense bloom of Trichodesmium. Significant and highly variable enhancements of the optical properties and particle concentration, including significant changes in the shape of PSD, were observed in the SML compared with USW at all investigated sites. In clear oligotrophic waters the total concentration of particles larger than 0.7 μm in size was enriched in the SML more than 8-fold. In all examined waters the enrichment was consistently higher for larger particles (>10 μm) than smaller particles. The highest enhancement of light absorption coefficients, >100-fold for particulate absorption and >200-fold for phytoplankton absorption in the near-UV and red spectral regions, was observed during the Trichodesmium bloom. In clear oligotrophic waters the particulate absorption coefficient was enhanced by as much as 45-fold in the green spectral region and the non-algal component exhibited consistently higher enhancement than phytoplankton component across the examined spectrum. In contrast to absorption, the volume scattering function was enhanced more in clear oligotrophic waters (>15-fold at scattering angles ψ between about 65° and 80°) than in the situation of Trichodesmium bloom. With the exception of Trichodesmium bloom, we consistently observed significantly lower values of the degree of linear polarization of light scattered by suspended particles and whole seawater samples (by as much as 30% in the vicinity of ψ = 90°) in the SML compared with USW. This result indicates that the SML can have important effect on the state of polarization of downwelling light entering the ocean and upwelling light leaving the ocean across the air-sea interface. The determinations of IOPs in the SML can extend the capabilities for characterizing constituents of microlayer and provide useful information for radiative transfer and remote-sensing related studies.

Ultra-sensitive spectroscopy of OH radical in high-temperature transient reactions.

The hydroxyl (OH) radical is arguably the most important transient radical in high-temperature gas-phase combustion reactions, yet it is very difficult to measure because of its high reactivity and, thus, short lifetime and low concentration. This work reports the development of a novel method for ultra-sensitive, quantitative, and microsecond-resolved detection of OH based on UV frequency-modulation spectroscopy (FMS). To the best of the authors' knowledge, this is the first FMS demonstration in the near-UV spectral region for detection of short-lived radical species. Shot-noise-limited detection was achieved at an optical power of 25mW. A proof-of-concept experiment in a tabletop H2O/He microwave discharge cell has reached a 1σ minimum detectable absorbance (MDA) of less than 2×10-4 over 1MHz measurement bandwidth. High-temperature OH measurement was demonstrated in a 15cm diameter shock tube, where a typical MDA of 3.0×10-4 was achieved at 1330K, 0.38atm, and 1MHz. These preliminary results have outperformed the previous best MDA by more than a factor of 3; further improvement by another order of magnitude is anticipated, following the strategies outlined at the end of this Letter. The current method paves the path to parts per billion (ppb) -level OH detection capability and offers prospects to significantly advance fundamental combustion research by enabling direct observation of OH formation and scavenging kinetics during key stages of fuel oxidation that were inaccessible with previous methods.

Changes in electron and hole traps in GaN-based light emitting diodes from near-UV to green spectral ranges

Deep electron and hole traps were studied by admittance spectroscopy (AS) and deep level transient spectroscopy (DLTS) with electrical and optical (ODLTS) injection for GaN-based multi-quantum-well (MQW) light emitting diodes (LEDs) operating in the near-UV (385–390 nm), blue (445 nm), and green (515 nm) spectral regions. AS spectra were dominated by freezing out of Mg acceptors at temperatures around 150 K, by shallow centers in the MQW region, and, for green LEDs, by deeper electron traps with a level near Ec − 0.27 eV located in the MQW region. DLTS spectra showed electron traps with levels Ec − 0.8 eV (NUV), Ec − 0.5 eV (blue), Ec − 0.6 eV (blue and NUV), and Ec − 0.27(green LEDs). In ODLTS, hole traps near Ev + 0.75 eV (NUV), Ev + 0.65 eV (blue), and Ev + 0.45 eV (green LEDs) originating in the quantum well (QW) region were detected (the QW character was confirmed by using excitation light that generated electron-hole pairs only within the QWs). The levels of the electron and hole traps in LED structures differing in the In composition in the QWs were well aligned with respect to the vacuum level.

Characterizations of nonlinear optical properties on GaN crystals in polar, nonpolar, and semipolar orientations

We report the basic nonlinear optical properties, namely, two-photon absorption coefficient (β), three-photon absorption coefficient (γ), and Kerr nonlinear refractive index (nkerr), of GaN crystals in polar c-plane, nonpolar m-plane, and semipolar (2021¯) plane orientations. A typical Z-scan technique was used for the measurement with a femtosecond Ti:S laser from wavelengths of 724 nm to 840 nm. For the two-photon absorption coefficient (β), similar values were obtained for polar, nonpolar, and semipolar samples, which are characterized to be ∼0.90 cm/GW at 724 nm and ∼0.65 cm/GW at 730 nm for all the three samples. For the Kerr nonlinear refractive index (nkerr), self-focusing features were observed in this work, which is different from previous reports where self-defocusing features were observed on GaN in the visible and near-UV spectral regions. At 724 nm, nkerr was measured to be ∼2.5 0×10−14 cm2/W for all three samples. Three-photon absorption coefficients (γ) were also determined, which were found to be consistent with previous reports. This study provides valuable information on the basic nonlinear optical properties of III-nitride semiconductors, which are vital for a wide range of applications such as integrated photonics and quantum photonics.

Highly Efficient Green-Emitting Phosphors Ba2Y5B5O17 with Low Thermal Quenching Due to Fast Energy Transfer from Ce3+ to Tb3.

This paper demonstrates a highly thermally stable and efficient green-emitting Ba2Y5B5O17:Ce3+, Tb3+ phosphor prepared by high-temperature solid-state reaction. The phosphor exhibits a blue emission band of Ce3+ and green emission lines of Tb3+ upon Ce3+ excitation in the near-UV spectral region. The effect of Ce3+ to Tb3+ energy transfer on blue to green emission color tuning and on luminescence thermal stability is studied in the samples codoped with 1% Ce3+ and various concentrations (0-40%) of Tb3+. The green emission of Tb3+ upon Ce3+ excitation at 150 °C can keep, on average, 92% of its intensity at room temperature, with the best one showing no intensity decreasing up to 210 °C for 30% Tb3+. Meanwhile, Ce3+ emission intensity only keeps 42% on average at 150 °C. The high thermal stability of the green emission is attributed to suppression of Ce3+ thermal de-excitation through fast energy transfer to Tb3+, which in the green-emitting excited states is highly thermally stable such that no lifetime shortening is observed with raising temperature to 210 °C. The predominant green emission is observed for Tb3+ concentration of at least 10% due to efficient energy transfer with the transfer efficiency approaching 100% for 40% Tb3+. The internal and external quantum yield of the sample with Tb3+ concentration of 20% can be as high as 76% and 55%, respectively. The green phosphor, thus, shows attractive performance for near-UV-based white-light-emitting diodes applications.

2D Arrays of Hexagonal Plasmonic Necklaces for Enhanced Second Harmonic Generation.

Hexagonal plasmonic necklaces of silver nanoparticles organized in 2D superlattices on functional ferroelectric templates are fabricated in large-scale spatial regions by using a surfactant-free photo-deposition process. The plasmonic necklaces support broad radiative plasmonic resonances allowing the enhancement of second harmonic generation (SHG) at the ferroelectric domain boundaries. A 400-fold SHG enhancement is achieved at the near-UV spectral region with subsequent interest for technological applications.

Zinc oxide films prepared via the lateral growth of aligned nanorod arrays

Continuous polycrystalline zinc oxide films 5 to 15 μm in thickness have been produced on both single-crystal silicon and transparent amorphous glass substrates via the growth of aligned nanorod arrays by chemical vapor deposition followed by lateral growth of the nanorods. The growth of the lateral faces of the nanorods was carried out under specially adjusted conditions in the same reactor as was used to grow the nanorods. The resultant films consisted of intergrown columnar crystals oriented along the c axis of the ZnO lattice (perpendicular to the substrate surface). The cathodoluminescence spectrum of the films was dominated by excitonic emission in the near-UV spectral region. The films had high electrical conductivity (ρ = 0.45 Ω cm), due to excess zinc. Prolonged annealing in air increased the resistivity of the films by five orders of magnitude (to ρ = 6 × 104 Ω cm). According to X-ray diffraction and Raman spectroscopy data, the films had good structural perfection, comparable to that of zinc oxide nanorods.

Spectral properties of copper halide nanocrystals in glasses of fluorine-phosphate matrix

The absorption spectra of glasses of fluorine-phosphate matrix in the near-UV spectral region have been investigated in the temperature range from 20 to 420°C. It is shown that the absorption bands in this spectral region are exciton absorption bands of copper chloride(I) nanocrystals. Results of X-ray diffraction analysis of the glasses are presented. It is shown that the temperature dependences of the exciton absorption bands of CuCl nanocrystals, obtained upon heating and cooling samples, have a a form of hysteresis.

Novel rare-earth-free yellow Ca5Zn3.92In0.08(V0.99Ta0.01O4)6 phosphors for dazzling white light-emitting diodes.

White light-emitting diode (WLED) products currently available on the market are based on the blue LED combined with yellow phosphor approach. However, these WLEDs are still insufficient for general illumination and flat panel display (FPD) applications because of their low color-rendering index (CRI < 75) and high correlated color temperature (CCT = 6000 K). Although near-ultraviolet (UV) LED chips provide more efficient excitation than blue chips, YAG:Ce3+ phosphors have very weak excitation in the near-UV spectral region. Hence, there is an increasing demand for novel yellow phosphor materials with excitation in the near-UV region. In this work, we report novel self-activated yellow Ca5Zn3.92In0.08(V0.99Ta0.01O4)6 (CZIVT) phosphors that efficiently convert near-UV excitation light into yellow luminescence. The crystal structure and lattice parameters of these CZIVT phosphors are elucidated through Rietveld refinement. Through doping with In3+ and Ta5+ ions, the emission intensity is enhanced in the red region, and the Stokes shift is controlled to obtain good color rendition. When a near-UV LED chip is coated with a combination of CZIVT and commercial blue Ba0.9Eu0.1MgAl10O17 phosphors, a pleasant WLED with a high CRI of 82.51 and a low CCT of 5231 K, which are essential for indoor illumination and FPDs, is achieved.

Characterization of Excited State Etheno-Fad: A Probe of the Role of Adenine in DNA Photolyase

Using femtosecond transient absorption spectroscopy, we have characterized flavin 1,N6 - ethenoadenine dinucleotide (e-FAD), an analog of flavin adenine dinucleotide (FAD), to understand the role of adenine in the photoinduced electron transfer (PET) reaction between reduced FAD (∗FADH-) and thymine dimers during its repair in DNA photolyase. The adenine in FAD may serve as a virtual or real intermediate in the PET reaction. e-FAD was used to modify the driving force between the adenine and its partners, providing data on parameters and processes that dictate the kinetics and pathways of electron transport. The neutral oxidized and the fully reduced anionic states of e-FAD, FAD, and flavin mononucleotide (FMN) in free solution exhibited multi-exponential decay kinetics that reflect their excited state quenching pathways and possible conformational heterogeneity. Generally, the introduction of the e-Ade group leads to much faster excited state decay in the reduced state. To investigate this further, the evolution of the excited state was probed in the visible, near-UV, and UVB spectral regions to determine whether PET was responsible for the short-lived excited state. The significance of these results to the role of the FAD adenine in DNA photolyase are discussed.

Depolarisation of light scattered by disperse systems of low-dimensional potassium polytitanate nanoparticles in the fundamental absorption band

The results of experimental studies of depolarising properties of disperse systems on the basis of potassium polytitanate nanoplatelets and nanoribbons in the visible and near-UV spectral regions are presented. It is shown that in the fundamental absorption band of the nanoparticle material the increase in the depolarisation factor takes place for the radiation scattered perpendicularly to the direction of the probing beam. For nanoribbons a pronounced peak of depolarisation is observed, which is caused by the essential anisotropy of the particles shape and the peculiarities of the behaviour of the material dielectric function. The empirical data are compared with the theoretical results for ‘nanodiscs’ and ‘nanoneedles’ with the model dielectric function, corresponding to that obtained from optical constants of the titanium dioxide dielectric function.