UV Light Illumination Research Articles

Design and fabrication of self-suspending aluminum-plastic/semiconductor photocatalyst devices for solar energy conversion

The design and synthesis of self-suspending photocatalyst device with easy recyclability is important for practical application. Here, this work utilizes aluminum-plastic package waste as raw material to prepare an aluminum-plastic supported TiO2 (AP-TiO2) photocatalyst device through 3D printing design and surface deposition method. A series of characterizations were carried out to explore the structure, morphology and performance of the AP-TiO2 device. Under UV light illumination, the AP-TiO2-50 efficiently degrade 93.6% tetracycline hydrochloride (THC) after 4 hr, which increases by 8.3% compared with that of TiO2 powder suspension system with the same catalyst amount. Based on it, AP-ZnO, AP-CdS, AP-g-C3N4 and AP-Pt-TiO2 are also fabricated, and applied in photocatalytic degradation and hydrogen evolution, which all exhibit higher photoactivities than powder suspension systems. This work provides a new avenue for the fabrication of advanced recyclable photocatalyst device. Moreover, the work offers a novel sight for the high-value utilization of aluminum-plastic package waste, which has positive implications for environmental protection.

Tetraphenylethylene Based Fluorescent Chemosensor for the Selective Detection of Explosive Nitroaromatic Compounds

AbstractHerein, we have reported a tetraphenylethylene (TPE) based fluorescent chemosensor 4,4′,4′′,4′′′‐(ethene‐1,1,2,2‐tetrayl)tetrakis(N,N‐dimethylaniline) (TPE‐DMA) for the selective detection of explosive nitroaromatic compounds (NACs), such as 2, 4, 6‐trinitrophenol also called as picric acid (PA), 2,4‐dinitrophenol (DNP), and p‐nitrophenol (NP) over other NACs in CHCl3. TPE‐DMA is highly selective and sensitive toward PA in presence of various metal ions and anions. The quenching efficiency can be calculated from the Stern‐Volmer equation and was found to be 4.02×104 M−1, 1.82×104 M−1and 3.12×104 M−1 respectively for PA, DNP and NP. The detection limit of TPE‐DMA towards PA, DNP and NP of about 4.088×10−6 M, 5.155×10−6 M and 3.989×10−6 M respectively. Furthermore, to study the practical applicability of TPE‐DMA, visual‐eye detection was performed not only in solid‐state on TLC plates but also in solution state in CHCl3 under visible light as well as UV light illumination.

Effect of Cu/In stoichiometric ratio on the performance of Self-powered Dual-wavelength CuxIn2-xS2/TiO2 photodetectors

Self-powered photodetectors (PDs) play an important role in future optoelectronic devices due to their unique advantages of low energy consumption, independent operation, easy miniaturization and integration. The II-type CuxIn2-xS2/TiO2 heterojunctions (0.8 ≤ x ≤ 1.1) PDs demonstrate self-powered dual-wavelength photoresponse at UV and visible regions. The Cu/In ratio in CuxIn2-xS2 films can regulate the energy band structure, then the optical and electronic properties. With the Cu/In ratio increasing, the optical band-gap narrows and Fermi energy level reduces for CuxIn2-xS2 films, resulting in the increased built-in electric field and the decreased interface transfer resistance for CuxIn2-xS2/TiO2 heterojunctions, which can promote the separation and transmission efficiency of the photogenerated carriers and significantly improved the self-powered PDs performance. The optimized PDs with Cu1.1In0.9S2/TiO2 heterojunctions exhibit the maximum responsivity (R) of 0.79 A/W, detectivity (D*) of 4.6 × 1012, linear dynamic range (LDR) of 88 dB and sensitivity (S) of 2.6 × 104 under UV light illumination and zero bias. The CuxIn2-xS2/TiO2 PDs hold potential prospects in dual-wavelength optoelectronic applications in self-powered systems and processes.

Full-Color Emissive D-D-A Carbazole Luminophores: Red to Near-Infrared Mechanofluorochromism, Aggregation-Induced Near-Infrared Emission, and Photodynamic Therapy Application.

The preparation of multi-functionalized luminophores with full-color emission based on an identical core skeleton is a significative but challenging research topic. In this work, eight donor-donor-acceptor (D-D-A) type luminogens based on a central carbazole core bearing a hydrocarbon chain of six carbon atoms are designed by using different kinds of donor and acceptor units on the left and on the right and synthesized in good yields. These D-D-A carbazole derivatives display deep-blue, sky-blue, blue-green, green, yellow-green, yellow, orange and red fluorescence in the solid state, respectively, achieving full-color emission covering the whole visible light range under UV light illumination. Notably, dicyano-functionalized triphenylamine-containing carbazole derivative exhibits rare aggregation-induced near-infrared emission and red to near-infrared mechanofluorochromism with high contrast beyond 100 nm. Furthermore, red emissive luminogen can serve as a potential candidate for cell imaging and photodynamic therapy (PDT). The present work not only provides reference for the construction of full-color emissive systems but also opens a new avenue to the preparation of multi-functionalized luminophores capable of simultaneously applying in near-Infrared mechanical-force sensors and PDT fields.

Naphthalene-based silica nanoparticles as a highly sensitive fluorescent chemosensor for mercury detection in real seawater

Mercury is considered one of the most harmful contaminants threatening human lives and the aquatic environment. Naphthalene and its derivatives have excellent fluorescence properties that can be exploited for mercury (Hg2+) sensing applications. Herein, we covalently attached naphthalene with silica nanoparticles (NSPs) using one-pot multiple steps synthesis approach. The NSPs were characterized by 1H NMR, FTIR, TGA, FESEM, and UV–vis spectroscopy. The fluorescent properties were analyzed in deionized water under normal and UV-light illumination. Finally, the synthesized NSPs were investigated as a chemosensor for Hg2+ ions detection in real seawater samples via photoluminescence (PL) spectroscopy. The results indicate that the fluorescence properties of NSPs (20 ppm) were quenched upon Hg2+ addition in the range from 0 to 50 ppm. The studies demonstrated that NSPs acted as a potential host for Hg2+ ions compared to other interfering ions present in the seawater sample. The NSPs chemosensor provides a linearity range (5 – 1000 ppb) and limit of detection LOD (1 ppb; 5 nM), even below the values suggested by US EPA drinking water safety regulations, which indicates its potential utilization for mercury sensing in seawater environments.

Fabrication of encapsulated and sticky surface-enhanced Raman spectroscopy substrate coupling with thin layer chromatography for determination of pesticide

A sealed and sticky surface-enhanced Raman scattering (SERS) substrate was fabricated by screen-printed technology. The screen-printed ink was prepared by mixing poly(ethylene glycol) diacrylate (PEGDA), Ag nanoparticles (Ag-NPs) and photoinitiator. After printed on Supporting material, PEGDA can polymerize into film under UV light illumination. Ag-NPs were sealed and protected by this film. SERS signal of 10−12 M rhodamine 6G has been recorded on this substrate. The homogeneity of this substrate was examined by mapping experiments, and the relative standard deviation of the signals from 48 points was within 10 %, indicating high uniformity of this substrate. Upon coupling with thin layer chromatography (TLC), this sticky SERS substrate can be in thorough contact with the separated targets on TLC plates and stick to them firmly by pressing a cover, which was effective for improving the detection sensitivity. This coupling technology exhibited good performance for determination of thiabendazole in complex matrix with a detection limit of 0.01 μg/mL.

Light-Driven Dynamic Hierarchical Architecture of Three-Dimensional Self-Assembled Cholesteric Liquid Crystal Droplets.

Cholesteric liquid crystals have attracted much attention in biosensors, in communication systems, security identification, hierarchical materials assembly, and microlasers, due to their complex and interesting structures accompanied by particular optical properties making them low-cost, label-free and sensitive. However, the reports of CLC droplets with stable topological configurations are still very limited, which hinders the fast development and broad application of CLC droplet-based devices. In this paper, we manifest light-driven changes in the topological configuration of cholesteric liquid crystals droplets, examined experimentally. Photoresponsive azo-LC doped CLC droplets were manipulated by irradiation by UV light to form novel topological configurations with stable 3D structures. The phenomenon behind the configuration changes is the light-induced cholesteric-isotropic phase transition that takes place in liquid crystals. Several topological configurations of CLC droplets have been demonstrated such as closed-ring structures with cone-shaped centers and concentric elliptical centers, and open-ring structures formed under unidirectional illumination of UV light. Structures with parallel CLC pitch lines at the center and with a central point singularity are also formed under multidirectional illumination. The competition of the elastic energy and surface energy of the CLC droplets results in the formation of the new topological configurations. All proposed configurations are stable and controllable by light, which enable CLC droplets with novel topological structures with new characteristics and provide a lot of potential applications in biosensors and microlasers.

Rapid microwave fabrication of new nanocomposites based on Tb-Co-O nanostructures and their application as photocatalysts under UV/Visible light for removal of organic pollutants in water

Herein, a novel and stable Tb-Co-O nanocomposite photocatalyst is fabricated through a one-pot microwave route for 2 min (600 W, 20 s On, 60 s Off), which is introduced as UV/Visible light active catalysts in wastewater treatment. Employing various combined parameters of Tb:Co ratio, pH adjustment agents, chemical and natural templates, the resulting nanostructures displayed the intrinsic structure nature, narrow size distribution, good optical properties, and excellent photocatalytic efficiency. The formation of Tb-Co-O nanostructures and their features were verified via X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and ultraviolet–visible diffuse reflection spectroscopy (DRS) technologies. Detailed physic-chemical measurements exhibited that all as-prepared nano-photocatalysts possesses both cubic (TbO1.81) and orthorhombic (TbCoO3) crystal structures. Furthermore, optical characterization by DRS developed light-sensitive channelization with band-gap energies at approximately 2.95 and 3.20 eV for Tb-Co-O nanocomposites. Finally, the photocatalytic studies of the resulting nanocomposites were compared by determining the elimination of Erythrosine (EY), Acid Violet 7 (AV7), and Acid Black 1(AB1) under UV and Visble light illumination. As a results, the TbCoO3/TbO1.81 nanocomposties with molar ratio of 1:3 (Tb:Co), valerian distillate as natural directing agent and ethylenediamine (en) as alkaline template yielded the optimum degradation percentage of 88 % for EY dye under the reaction condition of 10 ppm dye concentration in the presence UV light toward other pathways. Also, we proposed a mechanistic insight of photodegradation based on the radical scavengers, which revealed that h+ did the important role, and OH• and •O2− represented an irrelevant role in the degradation of EY. The current study offer an effective way for development of a high-efficiency Tb-Co-O photocatalyst in eliminating dyes from contaminant water.

Photocatalytic Methane Conversion over Pd/ZnO Photocatalysts under Mild Conditions

Here, Pd nanoparticles supported on ZnO were prepared by the alcohol-reduction and the borohydride-reduction methods, and their efficiency towards the photocatalytic conversion of methane under mild conditions were evaluated. The resulting Pd/ZnO photocatalysts were characterized by X-ray fluorescence, X-ray diffraction, X-ray photoelectron spectroscopy, UV–Vis, and transmission electron microscopy. The reactions were performed with the photocatalysts dispersed in water in a bubbling stream of methane under UV-light illumination. The products formed were identified and quantified by gas chromatography (GC-FID/TCD/MSD). The principal products formed were C2H6 and CO2 with minor quantities of C2H4 and CO. No H2 production was observed. The preparation methods influenced the size and dispersion of Pd nanoparticles on the ZnO, affecting the performance of the photocatalysts. The best performance was observed for the photocatalyst prepared by borohydride reduction with 0.5 wt% of Pd, reaching a C2H6 production rate of 686 µmol·h−1·g−1 and a C2H6 selectivity of 46%.

Fermi-level shift, electron separation, and plasmon resonance change in Ag nanoparticle-decorated TiO2 under UV light illumination.

Noble metal nanoparticles are widely used as co-catalysts for storing and separating electrons in semiconductor photocatalysis. Thus, evaluating this ability is important and meaningful to understand the photocatalytic mechanism. Employing Ag nanoparticles, the present study combined in situ photoconductance and theoretical analysis to evaluate the Fermi-level (EF) shift in a UV-illuminated Ag/TiO2 system under gaseous conditions. Based on this, the role of the Ag nanoparticles in storing and separating electrons was discussed. It was found that the EF of Ag/TiO2 is located deeper in the gap and a variation in temperature has less effect on the EF of Ag/TiO2 compared to the undecorated TiO2. The analysis showed that ∼46 electrons can be stored in 10 nm Ag nanoparticles under our experimental conditions, which does not change with temperature. The electron traps in TiO2 can affect the electron distribution in the TiO2 and Ag nanoparticles. It was observed that the localized surface plasmon resonance (LSPR) of the Ag nanoparticles exhibited a blue-shift under UV light illumination, which is generally ascribed to the electron storage in the Ag nanoparticles. However, we showed that the blue-shift is not related to the electron storage in the Ag nanoparticles, and thus it cannot be used as an indicator for evaluating their electron-storage ability. The in situ XPS analysis also does not support that the LSPR blue shift is associated with the reduction in the Ag2O layer and TiO2.

Investigation of conduction mechanism and UV light response of vertically grown ZnO nanorods on an interdigitated electrode substrate.

Vertically aligned zinc oxide nanorod (ZnO-NR) growth was achieved through a wet chemical route over a comb-shaped working area of an interdigitated Ag-Pd alloy signal electrode. Field-emission scanning electron microscopy images confirmed the formation of homogeneous ZnO-NRs grown uniformly over the working area. X-ray diffraction revealed single-phase formation of ZnO-NRs, further confirmed by energy-dispersive X-ray spectroscopy analysis. Temperature-dependent impedance and modulus formalisms showed semiconductor-type behavior of ZnO-NRs. Two electro-active regions i.e., grain and grain boundary, were investigated which have activation energy ∼0.11 eV and ∼0.17 eV, respectively. The conduction mechanism was investigated in both regions using temperature-dependent AC conductivity analysis. In the low-frequency dispersion region, the dominant conduction is due to small polarons, which is attributed to the grain boundary response. At the same time, the correlated barrier hopping mechanism is a possible conduction mechanism in the high dispersion region attributed to the bulk/grain response. Moreover, substantial photoconductivity under UV light illumination was achieved which can be attributed to the high surface-to-volume ratio of zinc oxide nanorods as they provide high density of trap states which causes an increase in the carrier injection and movement leading to persistent photoconductivity. This photoconductivity was also facilitated by the frequency sweep applied to the sample which suggests the investigated ZnO nanorods based IDE devices can be useful for the application of efficient UV detectors. Experimental values of field lowering coefficient (βexp) matched well with the theoretical value of βS which suggests that the possible operating conduction mechanism in ZnO nanorods is Schottky type. I-V characteristics showed that the significantly high photoconductivity of ZnO-NRs as a result of UV light illumination is owing to the increase in number of free charge carriers as a result of generation of electron-hole pairs by absorption of UV light photons.

Highly sensitive UV photodetector based on solution-processed bismuth oxyiodide epitaxial thin films

The as-fabricated photodetector based on high quality bismuth oxyiodide epitaxial thin film exhibited promising optoelectrical performance under UV light illumination and a tunable photoresponse mechanism depending on the film thickness.

Synthesis and characterization of ternary nanocomposites of TiO2/rGO/CdS as an efficient catalyst for photo‐degradation of methyl orange

AbstractNovel ternary composite photocatalysts have been successfully prepared by TiO₂ nanofibers, reduced graphene oxide, and CdS nanoparticles (TiO₂/rGO/CdS) by using electrospinning technique with easy chemical methods. The structures and their properties are examined by X‐ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, X‐ray photoelectron spectroscopy (XPS), and field‐emission scanning electron microscope (FESEM). The structural characterization of the composite reveals that pure TiO₂ NFs and CdS NPs crystalline very well and the reduced graphene oxide is tightly composed with TiO₂ NFs and CdS Nps. The photodegradation of methyl orange (MO) under UV light illumination is significantly enhanced compared with that of bare materials. This ternary composite degrades methyl orange within 75 min. The enhanced photocatalytic degradation performance resulted from effective separation of e–h pairs with rGO sheets and also contributed for high rate degradation efficiency. This novel ternary composite has a potential application of wastewater purification and utilization for energy conversions.

High brightness and vibronic luminescent behavior of YAG:Mn4+/Ca2+ red phosphor for preparing phosphor-in-glass in white LED

Left figure shows PL spectra of phosphors with and without Ca2+ ion. The central images present the photos of PiG under illumination of sunlight and UV light. Right figures give EL spectra of LED encapsulated with different phosphors.

Annealing effect on the physical properties of TiO2 thin films deposited by spray pyrolysis.

Titanium dioxide (TiO2) thin films were deposited on glass substrates at 350 °C using the spray pyrolysis technique. As deposited and annealed thin films were characterized by X-ray diffraction, scanning electron microscopy, UV-VIS spectroscopy, and photodetection. Unlike the as deposited samples which were amorphous, annealed samples show an anatase phase. Films were absorbent in the UV region and the band gap energy decreases from 3.78 eV to 3.4 eV with annealing. The photoresponse of TiO2 photodetectors was recorded under UV (λ1 = 365 nm, λ2 = 254 nm) and visible light illumination by reversible switching (ON/OFF) cycles using DC electrical characterization. Photosensitive properties such as reproducible photosensitivity, responsivity, and detectivity were also studied.

Quantifying Strain-Sensing Protein Recruitment During Stress Fiber Repair.

A family of proteins have been identified that recognize damaged, strained actin filaments in stress fibers. These proteins are often referred to as strain- or force-sensing and trigger downstream signaling mechanisms that can facilitate repair at these strain sites. Here we describe a method using high-resolution microscopy to screen and quantify the mechanosensitive recruitment of proteins to these stress fiber strain sites. Strain sites are induced using spatially controlled illumination of UV light to locally damage actin stress fibers. Recruitment of potential strain-sensing proteins can then either be compared to (Blanchoin, Physiol Rev 94, 235-263, 2014) a known control (e.g., zyxin-GFP) or (Hoffman, Mol Biol Cell 23, 1846-1859, 2012) the pre-damaged stress fiber protein distribution. With this method, strain-sensing proteins and their dynamic association with stress fiber strain sites can be reproducibly measured and compared.

Photoconductive Detector Based on Graphene Doping with Silver Nanoparticles

Graphene (Gr) decorated with silver nanoparticles (Ag NPs) were used to fabricate a wideband range photodetector. Silicon (Si) and porous silicon (PS) were used as a substrate to deposit Gr /Ag NPs by drop-casting technique. Silver nanoparticles (Ag NPs) were prepared using the chemical method. As well as the dispersion of silver NPs is achieved by a simple chemistry process on the surface of Gr. The optical, structure and electrical characteristics of AgNPs and Gr decorated with Ag NPs were characterized by ultraviolet-visible spectroscopy (UV-Vis), x-ray diffraction (XRD). The X-ray diffraction (XRD) spectrum of Ag NPs exhibited 2θ values (38.1o, 44.3 o, 64.5 o and 77.7 o) corresponding to the silver nanocrystal, while the XRD pattern of Gr-Ag NPs shows two distinct diffraction peaks at 2 θ = 26.2°and 54.7 which correspond to the (002), and (110). The absorption spectrum of Gr-AgNPs extended from UV to near IR region, surface plasmon resonance (SPR) absorption peak position for the AgNPs at (~320-480) nm. The I-V characteristics for the photoconductive detector on Si were measured with three sources: UV, visible, and IR. The photocurrent increased under the illumination of UV light (10W, 365nm), a Tungsten lamp (250W, 500-800nm), and a laser diode (300mW, 808nm). The I-V characteristics for the photoconductive detector on PS were measured with three sources: UV, Visible, and IR. Furthermore, we coated polyamide-nylon polymer on Gr/Ag NPs samples deposited on a Si and PS layer by the drop-casting method the results show that the photocurrent increased for all samples.

Identification of the Active Sites on Metallic MoO2-x Nano-Sea-Urchin for Atmospheric CO2 Photoreduction Under UV, Visible, and Near-Infrared Light Illumination.

We report an oxygen vacancy (Vo )-rich metallic MoO2-x nano-sea-urchin with partially occupied band, which exhibits super CO2 (even directly from the air) photoreduction performance under UV, visible and near-infrared (NIR) light illumination. The Vo -rich MoO2-x nano-sea-urchin displays a CH4 evolution rate of 12.2 and 5.8 μmol gcatalyst -1 h-1 under full spectrum and NIR light illumination in concentrated CO2 , which is ca. 7- and 10-fold higher than the Vo -poor MoO2-x , respectively. More interestingly, the as-developed Vo -rich MoO2-x nano-sea-urchin can even reduce CO2 directly from the air with a CO evolution rate of 6.5 μmol gcatalyst -1 h-1 under NIR light illumination. Experiments together with theoretical calculations demonstrate that the oxygen vacancy in MoO2-x can facilitate CO2 adsorption/activation to generate *COOH as well as the subsequent protonation of *CO towards the formation of CH4 because of the formation of a highly stable Mo-C-O-Mo intermediate.

Microwave-assisted Synthesis, Characterization, Photocatalytic Degradation of Antibiotics, and Fluorometric Selective Sensing Activity of g-C3N4 Supported CuO Composites.

Herein, we have designed for the fabrication of a series of g-C3N4/CuO composite by using one-step microwave-assisted synthesis for the degradation of antibiotics and detection of nano-molar range of toxic heavy metal ions. The synthesized g-C3N4/CuO composites were analyzed and characterized to know the structure, phase, surface area, absorption region, bandgap, and size of the composites. From the observation of TEM and XRD measurements, g-C3N4/CuO composites have hexagonal shape with average diameter of the particles is 25 ± 5nm. The observed band gap values from UV-vis DRS for g-C3N4 nanosheets and CuO NPs are 2.64eV and 1.72eV. The synthesized g-C3N4/CuO composite has prodigious specific surface area (32.47 m2/g), which is the evident for superior heterogeneous catalytic applications. Therefore, the synthesized g-C3N4/CuO composites were tested for the degradation of antibiotics such as tetracycline (TC) and ciprofloxacin (CIP) under UV light illumination, it shows 88.02% and 90.01% degradation was observed within 1h due to the matching optical band gap and internal charge transfer of excitons with in the heterojunction surface among g-C3N4 and CuO in the composite than the individual components (g-C3N4 and CuO) due to the high surface area and tiny particles of CuO were randomly deposited on the surface of g-C3N4 nanosheets. The catalytic reduction reaction follows as pseudo-first order equation and reused for 5 consecutive cycles without remarkable loss of catalytic activity. Moreover, the synthesized CuO NPs and g-C3N4/CuO composites were used as a prominent fluorescence sensing probe for the selective detection of Pb2+ in nano-molar range of concentration with Ksv is 1.38 × 104mol- 1dm3. It was observed as a linear relationship based on the change in intensity, the limit of detection was determined to be 0.184 nM.

Photodegradation of Methylene Blue by Nano-Titania developed from Novel Heteroleptic Titanium(IV) Complexes

Three new heteroleptic mononuclear derivatives of titanium(IV) have been synthesised and characterized by physico-chemical techniques. The newly synthesised titanium complexes [C26H21Br2NO5Ti] 1, [C26H21Cl2NO5Ti] 2 and [C26H21F2NO5Ti] 3 were obtained by treating [Ti(OPri)4] with 8-hydroxyquinoline, acetylacetone and corresponding phenol derivatives in 1:1:1:2 stoichiometry while refluxing in benzene as a reaction solvent under anhydrous stringent conditions. The newly synthesised titanium(IV) complexes were established by NMR (1H and 13C), FTIR and HRMS. Derivative 1 was employed as a precursor for the synthesis of nano titania by sol-gel method. The morphology of TiO2 was confirmed by several analytical tools such as FTIR, powder XRD, UV-Vis, RAMAN, SEM and TEM analyses. Further, the nano-structured titanium oxide developed herein was exploited to evaluate the catalytic photodegradation of methylene blue dye in aqueous solution on illumination of UV light that resulted in the extent of decolourization up to 68%, 81% and 94% by taking 20, 30 and 40 mg of catalyst in account respectively.