Photoluminescence shift in frustules of two pennate diatoms and nanostructural changes to their pores

The diatom silicified cell wall (frustule) contains pore arrays at the micro‐ to nanometer scale that display efficient luminescence within the visible spectrum. Morphometric analysis of the size and arrangement of pores was conducted to observe whether any correlation exists with the photoluminescence (PL) of two diatom species of different ages. UV‐excited PL displays four clearly defined peaks within the blue‐region spectrum, on top of the broad PL characteristic of synthetic porous silicon dioxide, recorded for reference and where discrete lines are absent. A set of shifted emission lines was observed when diatom cultures reached adulthood. These discrete line shifts correlate with structural changes observed in adult frustules: reduction in pore diameter; appearance of pores within pores, 10 nm in size; an increase in the gap distance between stria; and the deposition of several girdle bands with a concomitant increase in the diatom waist length, as well as the appearance of pores on such bands. Destruction of the pores results in the disappearance of all discrete emission lines. The PL shifts are correlated with a substantial increment of Si–OH groups adsorbed on the frustule surface, as revealed by Fourier transform infrared spectroscopy. Copyright © 2014 John Wiley & Sons, Ltd.     

NANOSTRUCTURE OF THE DIATOM FRUSTULE AS REVEALED BY ATOMIC FORCE AND SCANNING ELECTRON MICROSCOPY

The cell wall (frustule) of the freshwater diatom Pinnularia viridis (Nitzsch) Ehrenberg is composed of an assembly of highly silicified components and associated organic layers. We used atomic force microscopy (AFM) to investigate the nanostructure and relationship between the outermost surface organics and the siliceous frustule components of live diatoms under natural hydrated conditions. Contact mode AFM imaging revealed that the walls were coated in a thick mucilaginous material that was interrupted only in the vicinity of the raphe fissure. Analysis of this mucilage by force mode AFM demonstrated it to be a nonadhesive, soft, and compressible material. Application of greater force to the sample during repeated scanning enabled the mucilage to be swept from the hard underlying siliceous components and piled into columns on either side of the scan area by the scanning action of the tip. The mucilage columns remained intact for several hours without dissolving or settling back onto the cleaned valve surface, thereby revealing a cohesiveness that suggested a degree of cross-linking. The hard silicified surfaces of the diatom frustule appeared to be relatively smooth when living cells were imaged by AFM or when field-emission SEM was used to image chemically cleaned walls. AFM analysis of P. viridis frustules cleaved in cross-section revealed the nanostructure of the valve silica to be composed of a conglomerate of packed silica spheres that were 44.8 ± 0.7 nm in diameter. The silica spheres that comprised the girdle band biosilica were 40.3 ± 0.8 nm in diameter. Analysis of another heavily silicified diatom, Hantzschia amphioxys (Ehrenberg) Grunow, showed that the valve biosilica was composed of packed silica spheres that were 37.1 ± 1.4 nm and that silica particles from the girdle bands were 38.1 ± 0.5 nm. These results showed little variation in the size range of the silica particles within a particular frustule component (valve or girdle band), but there may be differences in particle size between these components within a diatom frustule and significant differences are found between species.     

Cd2+ affects the growth,hierarchical structure and peptide composition of the biosilica of the freshwater diatom Nitzschia palea (Kützing) W. Smith

Biosilica from diatoms is formed at ambient conditions under the control of biological and physicochemical processes. The changes in growth and biosilica formation through uptake of different concentrations of Cd²⁺ by the diatom Nitzschia palea (Kützing) W. Smith was investigated, correlating Cd²⁺ effects to changes in the biosilica nanostructure and the relative content of the encapsulated biomolecules. Diatom growth rates at different Cd²⁺ concentrations (as 1, 2, 3, 4, and 5 × 10^?1 mg L^?1 CdCl₂) were studied in order to determine the concentrations at which sublethal effects were visible, allowing the harvest of sufficient diatom cells for further experiments. We found a clear correlation between the Cd²⁺ concentrations and both the nanostructure of the biosilica and content of encapsulated peptides. Cd²⁺ induced biosilica deformation was assessed by scanning electron microscopy and attenuated total reflectance‐Fourier Transformed Infrared Spectroscopy (FTIR), revealing that micromorphological changes in frustule features (striae, costae, pores) and nanostructural modifications (structure of the silica and conformation of the encapsulated peptides) occurred at applied Cd²⁺ concentrations of 2 and 3 × 10^?1 mg L^?1. In particular the FTIR contribution of peptides decreased at elevated Cd²⁺ concentrations, whereas shifts in wave number of several relevant organic bonds as C = O stretching (1765 cm^?1) and possibly hydrated sulfate (1160, 1110 and 980 cm^?1) were assigned. Additional analysis of the amide I band showed a relative increase in β‐sheet structure (1680–1620 cm^?1) when Cd²⁺ concentration increased. Cadmium uptake clearly affected the molecular ordering of the biosilica in Nitzschia palea, most probably by interfering in biological or physicochemical processes involved in diatom biosilicification.     

Luminescence study and dosimetry approach of Ce on an α‐Sr2P2O7 phosphor synthesized by a high‐temperature combustion method

We report synthesis of a cerium‐activated strontium pyrophosphate (Sr₂P₂O₇) phosphor using a high‐temperature combustion method. Samples were characterized by X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), photoluminescence (PL) and thermoluminescence (TL). The XRD pattern reveals that Sr₂P₂O₇ has an α‐phase with crystallization in the orthorhombic space group of Pnam. The IR spectrum of α‐Sr₂P₂O₇ displays characteristic bands at 746 and 1190 cm^‐1 corresponding to the absorption of (P₂O₇)^‐4. PL emission spectra exhibit a broad emission band around 376 nm in the near‐UV region due to the allowed 5d–4f transition of cerium and suggest its applications in a UV light‐emitting diode (LED) source. PL also reveals that the emission originates from 5d–4f transition of Ce³⁺ and intensity increases with doping concentration. TL measurements made after X‐ray irradiation, manifest a single intense glow peak at around 192°C, which suggests that this is an outstanding candidate for dosimetry applications. The kinetic parameters, activation energy and frequency factor of the glow curve were calculated using different analysis methods. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and characterization of erbium‐doped YAlO3 phosphor

In the yttrium aluminium system, the YAlO₃ phosphor is a prominent host because of the yttrium aluminium ratio (1:1). Phosphor was synthesized by the solid‐state reaction method at variable concentrations of erbium (0.1–2.5 mol%). This method is suitable for large‐scale production and is a less time‐consuming method when compared with the soft synthesis method. The prepared sample was characterized by X‐ray diffraction technique and the crystallite size was calculated by Scherer's formula. Vibrational and bending analysis of prepared phosphor for optimized concentration of erbium ion is described based on the Fourier transform infrared spectroscopic technique. The photoluminescence (PL) emission spectra of prepared phosphor for variable concentrations of erbium ion were recorded and the excitation spectrum was found to be at 291 nm with three shoulder peaks at 305, 270 and 242 nm. For 291 nm excitation, the emission spectrum was found at 546 nm and 552 nm. PL intensity increased with increasing concentrations of erbium and after 2 mol% emission intensity decreased due to concentration quenching. Spectrophotometric determination of YAlO₃:Er³⁺ is described by CIE co‐ordinates and shows an intense emission in the green region such that the prepared phosphor can act as a single host for green light emission. Thermoluminescence glow curve analysis of the YAlO₃:Er³⁺ phosphor was recorded for different ultraviolet (UV) light exposures and gamma exposure. Different gamma doses 0.5–2 kGy show a linear response. Kinetic parameters were calculated by the peak shape method. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis,characterization, and photoluminescence property of Nd–TUD‐1

Here, five different samples of neodymium (Nd) incorporated 3D‐mesoporous siliceous materials were fabricated using a single‐step hydrothermal technique. Typically, all samples were subjected to several qualitative elemental and quantitative analyses such as X‐ray diffraction, N₂‐adsorption/desorption, scanning electron microscopy, energy dispersive X‐ray, mapping, high resolution transmission electron microscopy, diffuse reflectance ultraviolet–visible, and Raman spectroscopy. The characterization results showed that at small loading of Nd (i.e. Si/Nd < 20), only isolated centres of trivalent neodymium ions were tetrahedrally coordinated in the TUD‐1 matrix. However, with increasing neodymium loading, additional nanoparticles of neodymium oxide with size 10–20 nm were embedded into silica host pores. Detailed photoluminescence (PL) analysis of all samples was carried out by recording the emission profiles at two diverse excitation wavelengths, 333 and 343 nm, to understand the effect of the Nd³⁺ environment on the PL emission spectra with special attention to the area between 400 and 600 nm. Most importantly, different peaks of the emission spectrum of each sample exhibited a distinct shape based on the Nd³⁺ environment. This performance was superior evidence that PL can be applied as a simple and efficient characterization tool to understand the nature of Nd³⁺ ion linkage with a silica matrix.     

Control of chitin nanofiber production by the lipid‐producing diatom Cyclotella Sp. through fed‐batch addition of dissolved silicon and nitrate in a bubble‐column photobioreactor

Diatoms are single‐celled algae that make cell walls of nanopatterned biogenic silica called frustules through metabolic uptake of dissolved silicon and its templated condensation into biosilica. The centric marine diatom Cyclotella sp. also produces intracellular lipids and the valued coproduct chitin, an N‐acetyl glucosamine biopolymer that is extruded from selected frustule pores as pure nanofibers. The goal of this study was to develop a nutrient feeding strategy to control the production of chitin nanofibers from Cyclotella with the coproduction of biofuel lipids. A two‐stage phototrophic cultivation process was developed where Stage I set the cell suspension to a silicon‐starved state under batch operation, and Stage II continuously added silicon and nitrate to the silicon‐starved cells to enable one more cell doubling to 4 × 10⁶ cells mL^?1. The silicon delivery rate was set to enable a silicon‐limited cell division rate under cumulative delivery of 0.8 mM Si and 1.2 mM nitrate (1.5:1 mol N/mol Si) over a 4‐ to 14‐day addition period. In Stage II, both cell number and chitin production were linear with time. Cell number and the specific chitin production rate increased linearly with increasing silicon delivery rate to achieve cumulative product yields of 13 ± 1 mg chitin/10⁹ cells and 33 ± 3 mg lipid/10⁹ cells. Therefore, chitin production is controlled through cell division, which is externally controlled through silicon delivery. Lipid production was not linearly correlated to silicon delivery and occurred primarily during Stage I, just after the complete co‐consumption of both dissolved silicon and nitrate. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:407–415, 2017     

Microwave‐assisted sintering synthesis of greenish‐yellow emitting Sr2SiO4:Eu2+ phosphors

Europium ion (Eu²⁺) doped Sr₂SiO₄ phosphors with greenish‐yellow emission were synthesized using microwave‐assisted sintering. The phase structure and photoluminescence (PL) properties of the obtained phosphor samples were investigated. The PL excitation spectra of the Sr₂SiO₄:Eu²⁺ phosphors exhibited a broad band in the range of 260 nm to 485 nm with a maximum at 361 nm attributed to the 5f‐4d allowed transition of the Eu²⁺ ions. Under an excitation at 361 nm, the Sr₂SiO₄:Eu²⁺ phosphor exhibited a greenish‐yellow emission peak at 541 nm with an International‐Commission‐on‐Illumination (CIE) chromaticity of (0.3064, 0.4772). The results suggest that the microwave‐assisted sintering method is promising for the synthesis of phosphors owing to the decreased sintering time without the use of additional reductive agents.     

Luminescence properties of a nanoporous freshwater diatom

Freshwater diatom frustules show special optical properties. In this paper we observed luminescence properties of the freshwater diatom Cyclotella meneghiniana. To confirm the morphological properties we present scanning electron microscopy (SEM) images. X‐ray diffraction (XRD) studies were carried out to visualize the structural properties of the frustules, confirming that silica present in diatom frustules crystallizes in an α‐quartz structure. Study of the optical properties of the silica frustules of diatoms using ultra‐violet‐visible (UV‐vis) spectroscopy and photoluminescence spectroscopy confirmed that the diatom C. meneghiniana shows luminescence in the blue region of the electromagnetic spectrum when irradiated with UV light. This property of diatoms can be exploited to obtain many applications in day‐to‐day life. Also, using time‐resolved photoluminescence spectroscopy (TRPL) it was confirmed that this species of diatom shows bi‐exponential decay. Copyright © 2011 John Wiley & Sons, Ltd.     

Influence of bacteria on cell size development and morphology of cultivated diatoms

Vegetative cell division in diatoms often results in a decreased cell size of one of the daughter cells, which during long‐term cultivation may lead to a gradual decrease of the mean cell size of the culture. To restore the initial cell size, sexual reproduction is required, however, in many diatom cultures sexual reproduction does not occur. Such diatom cultures may lose their viability once the average size of the cells falls below a critical size. Cell size reduction therefore seriously restrains the long‐term stability of many diatom cultures. In order to study the bacterial influence on the size diminution process, we observed cell morphology and size distribution of the diatoms Achnanthidium minutissimum, Cymbella affiniformis and Nitzschia palea for more than two years in bacteria‐free conditions (axenic cultures) and in cultures that contain bacteria (xenic cultures). We found considerable morphological aberrations of frustule microstructures in A. minutissimum and C. affiniformis when cultivated under axenic conditions compared to the xenic cultures. These variations comprise significant cell length reduction, simplification and rounding of the frustule contour and deformation of the siliceous cell walls, features that are normally found in older cultures shortly before they die off. In contrast, the xenic cultures were well preserved and showed less cell length diminution. Our results show that bacteria may have a fundamental influence on the stability of long‐term cultures of diatoms.     

Structural and photoluminescence study of Mn2+‐activated CaYAl3O7 blue phosphors

The structural and photoluminescence properties of CaYAl₃O₇ phosphor material doped with varying concentration of Mn²⁺ have been studied. The phosphor material was synthesized by the combustion method at 500 °C and was characterized using X‐ray diffraction, Fourier transform infrared spectroscopy and photoluminescence spectroscopy (PL). X‐ray diffraction showed that the crystallites have average sizes in the range of ~58–70 nm. Corresponding Fourier transform infrared spectroscopy investigations confirm the phase formation and the presence of aluminate group (Al‐O bands) in CaYAl₃O₇:Mn²⁺ phosphor. Under the excitation at 356 nm wavelength, the PL spectra show the occurrence of two emission peaks obtained in the blue region at 389 nm and 412 nm, which is attributed to the 4 T1(G) → 6A1 transition of Mn²⁺ ion. Upon increasing Mn²⁺ concentration, the relative PL intensity shows an initial decrement followed by an increase displaying the effect of concentration quenching. Overall the results suggest the possibility of using this material in white lighting devices and plasma display panels. Copyright © 2013 John Wiley & Sons, Ltd.     

Characterization and luminescence properties of CaMgSi2O6:Eu2+ blue phosphor

A blue CaMgSi₂O₆:Eu²⁺ phosphor was prepared by the solid‐state reaction method and the phosphor characterized in terms of crystal structure, particle size, photoluminescence (PL), thermoluminescence (TL) and mechanoluminescence (ML) properties using X‐ray diffraction (XRD), transmission electron microscopy (TEM), PL spectroscopy, TLD reader and ML impact technique. The XRD result shows that phosphor is formed in a single phase and has a monoclinic structure with the space group C2/c. Furthermore, the PL excitation spectra of Eu²⁺‐doped CaMgSi₂O₆ phosphor showed a strong band peak at 356 nm and the PL emission spectrum has a peak at 450 nm. The depths and frequency factors of trap centers were calculated using the TL glow curve by deconvolution method in which the trap depths were found to be 0.48 and 0.61 eV. The formation of CaMgSi₂O₆:Eu²⁺ phosphor was confirmed by Fourier transform infrared spectroscopy. The ML intensity increased linearly with the impact velocity of the piston used to deform the phosphor. It was shown that the local piezoelectricity‐induced electron bombardment model is responsible for the ML emission. Finally, the optical properties of CaMgSi₂O₆:Eu²⁺ phosphors are discussed. Copyright © 2015 John Wiley & Sons, Ltd.     

A Widely Distributed Thraustochytrid Parasite of Diatoms Isolated from the Arctic Represents a gen. and sp. nov.

A unicellular, heterotrophic, eukaryotic parasite was isolated from nearshore Arctic marine sediment in association with the diatom Pleurosigma sp. The parasite possessed ectoplasmic threads that could penetrate diatom frustules. Healthy and reproducing Pleurosigma cultures would begin to collapse within a week following the introduction of this parasite. The parasite (2–10 μm diameter) could reproduce epibiotically with biflagellate zoospores, as well as binary division inside and outside the diatom host. While the parasite grew, diatom intracellular content disappeared. Evaluation of electron micrographs from co‐cultures revealed the presence of hollow tubular processes and amorphic cells that could transcend the diatom frustule, generally at the girdle band, as well as typical thraustochytrid ultrastructure, such as the presence of bothrosomes. After nucleotide extraction, amplification, and cloning, database queries of DNA revealed closest molecular affinity to environmental thraustochytrid clone sequences. Testing of phylogenetic hypotheses consistently grouped this unknown parasite within the Thraustochytriidae on a distinct branch within the environmental sequence clade Lab19. Reclassification of Arctic high‐throughput sequencing data, with appended reference datasets that included this diatom parasite, indicated that the majority of thraustochytrid sequences, previously binned as unclassifiable stramenopiles, are allied to this new isolate. Based on the combined information acquired from electron microscopy, life history, and phylogenetic testing, this unknown isolate is described as a novel species and genus.     

Synthesis and luminescent properties of a novel bluish‐white afterglow phosphor,b‐Zn3(PO4)2:Hf4+

A new bluish‐white long‐lasting phosphorescent material, Hf⁴⁺‐doped b‐Zn₃(PO₄)₂, was prepared by the conventional high‐temperature solid‐state method. The photoluminescence (PL) spectrum reveals that it exhibits a strong blue emission band centred at 470 nm, with asymmetry on the long wavelength side; this material emits bluish‐white light and shows strong afterglow phosphorescence after it is excited with a 254 nm UV lamp. The phosphorescence lasts nearly 40 min in the light perception of the dark‐adapted human eye (0.32 mcd/m²). The possible phosphorescence mechanism is also analysed. Copyright © 2008 John Wiley & Sons, Ltd.     

Luminescent properties of a novel fluorene organic material

The photo‐physical properties of 6,6′‐(9H‐fluoren‐9,9‐diyl)bis(2,3‐bis(9,9‐dihexyl‐9H‐fluoren‐2‐yl)quinoxaline) (BFLBBFLYQ) and its blend doped with N′‐biphenyl‐N,N′‐bis‐(3‐methylphenyl)‐1,1′‐biphenyl‐4,4′‐diamine (TPD) were investigated. The absorption, photoluminescence (PL) and electroluminescence (EL) properties of pristine BFLBBFLYQ and blend in solution and spin‐coated film are outlined, including a discussion of charge‐transfer (CT) exciplex emission of BFLBBFLYQ:TPD blend in the solid state. The luminescent properties of BFLBBFLYQ films using different deposition processes were studied. It was found that the low‐energy emission bands at 530–570 nm appeared in the PL spectra of BFLBBFLYQ evaporated films in ultra‐high vacuum. Also, the low‐energy band was the exclusive emission in the EL spectra of BFLBBFLYQ films. Copyright © 2008 John Wiley & Sons, Ltd.     

The Diatom Staurosirella pinnata for Photoactive Material Production

A native isolate of the colonial benthic diatom Staurosirella pinnata was cultivated for biosilica production. The silicified cell walls (frustules) were used as a source of homogeneous and structurally predictable porous biosilica for dye trapping and random laser applications. This was coupled with the extraction of lipids from biomass showing potential to fabricate photoactive composite materials sustainably. The strain was selected for its ease of growth in culture and harvesting. Biosilica and lipids were obtained at the end of growth in indoor photobioreactors. Frustules were structurally characterized microscopically and their chemistry analyzed with Fourier Transform Infrared Spectroscopy. Frustule capacity of binding laser dyes was evaluated on a set of frustules/Rhodamine B (Rho B) solutions and with respect to silicon dioxide and diatomite by Fluorescence Spectroscopy demonstrating a high affinity for the organic dye. The effect of dye trapping property in conveying Rho B emission to frustules, with enhancement of scattering events, was analyzed on Rho B doped polyacrylamide gels filled or not with frustules. Amplified spontaneous emission was recorded at increasing pump power indicating the onset of a random laser effect in frustule filled gels at lower power threshold compared to unfilled matrices.     

Synthesis and novel emission properties of Bi3+-doped Ca2BO3Cl phosphor for plant cultivation

In the present work, a series of Bi³⁺-activated Ca₂BO₃Cl phosphors was synthesized using the conventional high-temperature solid-state reaction method. The crystal structure of the prepared sample was determined to be monoclinic with space group P21/c. Scanning electron microscopy (SEM) analysis demonstrated the surface morphology with aggregated particles and sizes in the nano range. The presence of vibrational features and their luminescence characteristics were studied using Fourier transform infrared spectroscopy and photoluminescence (PL) techniques, respectively. At the 486 nm excitation wavelength, the PL spectrum revealed a sharp emission centred at 732 nm that was attributed to the ³P₁→¹S₀ transition of Bi³⁺. The emission spectra exhibited the highest emission intensity at 0.5 mol% Bi³⁺ ion concentration, beyond this the emission intensity decreased due to the concentration quenching phenomenon attributed to multipolar interaction. The Commission Internationale de l'éclairage coordinates located at (0.7347, 0.2653) confirmed emission in the deep-red region with a colour purity of 99.98%. The obtained outcomes suggested that the reported material may be a promising candidate as a red-emitting phosphor for w-LEDs and plant growth applications.     

OBSERVATIONS OF A TUBE-DWELLING DIATOM: NAVICULA HAMULIFERA (BACILLARIOPHYCEAE)1

Colonies of the tube-dwelling diatom Navicula hamulifera Grunow living on mangrove prop roots in Indian River. Florida and at La Parguera, Puerto Rico, were studied using light and electron microscopy. Observations of the tube morphology and cell structure of this diatom from fresh samples and cultures are described, as well as the ultrastructural morphology of its frustule. The formation of tubes by this diatom is reported for the first time. Comparisons are made with the closest species; Navicula delognei V.H. and Navicula pseudocomoides Hendey.     

Synthesis and luminescent properties of novel BaGd2O4:Eu3+ scintillating phosphor

BaGd_2‐xO₄:xEu³⁺ and Ba_1‐yGd_1.79‐2yEu_0.21Na_3yO₄ phosphors were synthesized at 1300°C in air by conventional solid‐state reaction method. Phosphors were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence excitation (PLE) spectra, photoluminescence (PL) spectra and thermoluminescence (TL) spectra. Optimal PL intensity for BaGd_2‐xO₄:xEu³⁺ and Ba_1‐yGd_1.79‐2yEu_0.21Na_3yO₄ phosphors at 276 nm excitation were found to be x = 0.24 and y = 0.125, respectively. The PL intensity of Eu³⁺ emission could only be enhanced by 1.3 times with incorporation of Na⁺ into the BaGd₂O₄ host. Enhanced luminescence was attributed to the flux effect of Na⁺ ions. However, when BaGd₂O₄:Eu³⁺ phosphors were codoped with Na⁺ ions, the induced defects confirmed by TL spectra impaired the emission intensity of Eu³⁺ ions. Copyright © 2012 John Wiley & Sons, Ltd.     

Enhancement of photosynthesis in Sorghum bicolor by ultraviolet radiation

We assessed the influence of ultraviolet radiation (UV) on net photosynthetic CO₂ assimilation rate (P_n) in Sorghum bicolor, with particular attention to examining whether UV can enhance P_n via direct absorption of UV and absorption of UV‐induced blue fluorescence by photosynthetic pigments. A polychromatic UV response spectrum of leaves was constructed by measuring P_n under different UV supplements using filters that had sharp transmission cut‐offs from 280 to 382 nm, against a background of non‐saturating visible light. When the abaxial surface was irradiated, P_n averaged 4.6% higher with the UV supplement that cut‐off UV at 311 nm, compared to lower and higher UV wavelength supplements. This former supplement differed from higher wavelength supplements by primarily providing more UV between 320 and 350 nm. To assess the possibility of direct absorption of UV by photosynthetic pigments, we measured the absorbance of extracted chlorophylls. Chlorophyll a had absorbance peaks at 340 and 389 nm that were 49 and 72% of that at the sorét peak. Chlorophyll b had absorbance peaks at 315 and 346 nm that were both 35% of that at the sorét peak. Since the epidermis transmits some UV, the strong UV absorbance of chlorophyll implies a potential role for irradiance beyond the bounds of the conventionally defined photosynthetically active radiation waveband (400–700 nm). To assess the role of absorption of UV‐induced blue fluorescence, we measured the UV‐induced fluorescence excitation and emission spectra of leaves. Abaxial excitation peaked at 328 nm, while emission peaked at 446 nm. In this analysis, we used our abaxial fluorescence excitation spectrum and the UV photosynthetic inhibition spectrum of Caldwell et al. (1986) to weight the UV irradiance with each cut‐off filter, thereby estimating the potential contribution of UV‐induced blue fluorescence to photosynthesis and the inhibitory effects of UV irradiance on photosynthesis, respectively. With a non‐saturating visible background, we estimate that the absorption of UV‐induced blue fluorescence and the direct absorption of UV by photosynthetic pigments maximally enhanced photosynthesis by about 1% each with the UV supplement that cut‐off UV at 311 nm. We suggest that a portion of the incident UV on the S. bicolor leaves was used to drive photosynthesis.