Visible light-induced catalytic activation of peroxymonosulfate using heterogeneous surface complexes of amino acids on TiO₂

Lim, Jonghun,Kwak, Dong-yeob,Sieland, Fabian,Kim, Chuhyung,Bahnemann, Detlef W.,Choi, Wonyong Elsevier 2018 Applied Catalysis B Vol.225 No.-

<P><B>Abstract</B></P> <P>Peroxymonosulfate (PMS) is being extensively investigated as an eco-friendly oxidant and various activation methods of PMS have been investigated. Here we demonstrated a new method of catalytic PMS activation, which employed amino acids as both a visible light sensitizer and a substrate to be degraded. Although PMS and amino acids do not absorb any visible light, the surface adsorption of amino acids on titania formed charge-transfer complexes that absorb visible light (λ > 420 nm). Serine and histidine were employed as main target amino acids and their surface complexes on TiO<SUB>2</SUB> were characterized by various spectroscopic methods The ligand-to-metal charge transfer between amino acids and TiO<SUB>2</SUB> enabled the absorption of visible light and the subsequent electron transfer catalytically activated PMS with generating sulfate radicals which were detected by electron paramagnetic resonance analysis. Based on various scavenger tests, amino acids seem to be degraded mainly by sulfate radical (radical pathway) and by a non-radical pathway (PMS serving primarily as an electron acceptor) to some extent. Amino acids were degraded with producing ammonium as a sole nitrogenous product in this process, whereas most advanced oxidation processes of amino acid generate not only ammonium but also nitrate and nitrite. The visible light-induced charge transfer characteristics of the amino acid-TiO<SUB>2</SUB> complexes were demonstrated by the photoelectrochemical characterizations and the time-resolved laser spectroscopic analysis.</P> <P><B>Highlights</B></P> <P> <UL> <LI> PMS can be activated by charge transfer between amino acids and TiO<SUB>2</SUB> under visible light. </LI> <LI> Amino acids are employed as both a visible light sensitizer and a target pollutant in PMS-induced oxidation. </LI> <LI> The visible light-induced charge transfer characteristics of the amino acid-TiO<SUB>2</SUB> complexes are spectroscopically demonstrated. </LI> <LI> Ammonium is generated as a sole nitrogenous product from the degradation of amino acids. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

TiO₂ complexed with dopamine-derived polymers and the visible light photocatalytic activities for water pollutants

Kim, Sujeong,Moon, Gun-hee,Kim, Gonu,Kang, Unseock,Park, Hyunwoong,Choi, Wonyong Academic Press 2017 Journal of catalysis Vol.346 No.-

<P><B>Abstract</B></P> <P>Visible light-induced chemical transformation using inexpensive photocatalytic materials has been proposed as an eco-friendly method for energy and environmental applications. In this work, we employed polymers of environmentally benign derivatives of dopamine (DA) as low-cost sensitizers of titania and systematically investigated their properties for the visible light photocatalytic transformation in aquatic environment. DA and its derivatives (norepinephrine and nitrodopamine) were chosen as monomers, and their polymers (pDA, pNE, and pNDA) were synthesized and subsequently complexed with TiO<SUB>2</SUB>. Visible light-induced catalytic transformations were successfully demonstrated for the reduction of Cr(VI) to Cr(III), dechlorination of CCl<SUB>4</SUB>, oxidation of As(III) to As(V), and H<SUB>2</SUB>O<SUB>2</SUB> production via dioxygen reduction using polymer-complexed TiO<SUB>2</SUB>. pDA–TiO<SUB>2</SUB> exhibited the highest activities, much higher than those of DA–TiO<SUB>2</SUB> in all tested cases, which indicates that the polymerized form of DA forms a stronger and more efficient surface complex on the TiO<SUB>2</SUB> surface for visible light sensitization. DA-derived polymers could efficiently transfer electrons to the TiO<SUB>2</SUB> conduction band under visible light to initiate reductive transformations, whereas the oxidative transformation of organic substrates was largely inhibited because the organic polymer layer on TiO<SUB>2</SUB> should scavenge any oxidizing radical species. pDA and pNE exhibited far higher activity than pNDA due to the extensive π electron delocalization induced by the 5,6-dihydroxyindole structure. This was also supported by the higher photon-to-current conversion and lower charge transfer resistance obtained with pDA–TiO<SUB>2</SUB> and pNE–TiO<SUB>2</SUB> (compared with pNDA–TiO<SUB>2</SUB>), which was observed with photoelectrochemical measurements. pDA should be an attractive visible light sensitizer for aquatic transformations.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Dopamine-derived-polymer-coated TiO<SUB>2</SUB> is synthesized through a one-step self-oxidation method. </LI> <LI> The structure of polymers affects the light absorption and consequently the visible-light-induced photocatalytic activity. </LI> <LI> Visible light sensitization through dopamine-derived polymers is highly effective for reductive conversion. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Plasma arc light를 이용한 bracket 부착시의 전단결합강도와 파절양상의 유형

박영철,유형석,오영근,이승연 대한치과교정학회 2001 대한치과교정학회지 Vol.31 No.2

본 연구의 목적은 bracket 부착시 광조사시간을 획기적으로 감소시킬 수 있는 plasma arc licht의 임상적 유용성을 visible light 중합시의 전단결합강도와 접착파절양상과 비교해 봄으로써 평가해 보는데 있다. 사람의 상하악 소구치를 포매하여 만든 레진블럭시편에 광중합 접착제인 TransbondR를 사용하여 수종의 bracket을 각각의 조건에 따라 부착한 후 만능 물성시험기를 이용하여 전단결합강도를 측정하고, 접착파절양상을 stereoscope을 이용하여 관찰하여 다음과 같은 결과를 얻었다. 1.Plasma arc light를 이용한 수종의 bracket 접착시 metal bracket과 ceramic bracket의 전단결합강도는 임상적으로 사용하기에 충분한 값을 나타내었으며, resin bracket의 경우 다른 bracket에 비해 전단결합강도가 현저히 작은 값을 나타내었지만 임상적으로 사용이 가능한 값을 나타내었다. 2.Visible light를 이용한 metal bracket의 광중합시 광조사시 간에 따른 전단결합강도는 광조사 시 간에 따른 유의 한 차이를 보이지 않았으며, 임상적으로 사용하기에 충분한 강도를 나타내었다. 3.Plasma arc light를 이용한 수종의 bracket 접착시 접착제 잔류지수를 통해 접착파절양상을 관찰한 결과, metal bracket과 resin bracket의 경우 bracket기저면에 접착제가 반 이상 남아 있지 않은 경우가 많았으며, ceramic bracket의 경우 bracket기저면에 접착제가 반 이상 남아 있는 경우가 많았다. 4.Metal bracket의 부착시 plasma arc light를 2초간 광조사한 군과 visible light를 10초간 광조사한 군의 전단결합강도와 접착파절양상을 비교시 유의한 차이를 보이지 않았다. 6.Plasma arc light를 이용한 광중합시 광조사 거리에 따른 전단결합강도는 거리가 증가할수록 감소하였다. 이상의 실험 결과는 plasma arc light를 이용한 bracket의 접착시 전단결합강도 저하의 우려 없이 임상적으로 사용 가능함을 시사한다. The puruose of this study was to evaluate the clinical usefulness of plasma arc light which can reduce the curing time dramatically compared by shear bond strengths and failure patters of the brackens bonded with visible light in direct bracket bonding. Some kinds of brackets were bonded with the TransbondR to the human premolars which were embedded in the resin blocks according to the various conditions. After bonding, the shear bond strength was tested by Instron universal testing machine and in addition , the amount of residual adhesive remaining on the tooth after debonding was measured by the stereoscope and assessed with adhesive remnant index(ARI). The results were as follows : 1.When plasma arc light was used for bonding the brackets, the shear bond strength was clinically sufficient in both metal and ceramic brackets, but resin brackets showed significantly lower bond strength but which was clinically useful. 2.When metal brackets were bonded using visible light, there was no significant difference in shear bond strength due to the light-curing time and the bond strength was clinically sufficient. 3.When the adhesive failure patterns of brackets bonded with plasma arc light were observed by using the adhesive remnant index, the bond failure of the metal and resin bracket occurred more frequently at bracket-adhesive interface but the failure of the ceramic bracket occurred more frequently at enamel-adhesive interface. 4.There was no statistically significant difference of the shear bond strength and adhesive failure pattern between metal bracket bonded for 2 seconds by curing with plasma arc light and 10 seconds by curing with visible light. 6.When metal brackets were bonded using plasma arc light, the shear bond strength decreased as the distance from the light source increased. The above results suggest that plasma arc light can be clinically useful for bonding the brackets without fear of the decrease of the shear bond strength.

Oxalate-TiO₂ complex-mediated oxidation of pharmaceutical pollutants through ligand-to-metal charge transfer under visible light

Park, Jeesu,Moon, Gun-hee,Shin, Kyong-Oh,Kim, Jungwon Elsevier 2018 Chemical Engineering Journal Vol.343 No.-

<P><B>Abstract</B></P> <P>Oxalate-adsorbed TiO<SUB>2</SUB> shows visible activity for the oxidation of ranitidine, although neither oxalate nor pure TiO<SUB>2</SUB> alone absorbs visible light. The formation of an oxalate-TiO<SUB>2</SUB> complex facilitates electron transfer from oxalate to the TiO<SUB>2</SUB> conduction band (CB) (i.e., a ligand-to-metal charge transfer (LMCT)) and generates superoxide/hydroperoxyl radicals (O<SUB>2</SUB> <SUP> −</SUP>/HO<SUB>2</SUB> <SUP> </SUP>), which are primarily responsible for ranitidine oxidation, under visible light. The attenuated total reflection Fourier transform infrared (ATR-FTIR) spectra of oxalate-adsorbed TiO<SUB>2</SUB> indicates that the formation of a LMCT complex between oxalate and TiO<SUB>2</SUB> occurs through bidentate carboxylate linkages. The visible light-induced generation of photocurrent (<I>I</I> <SUB>ph</SUB>) on the TiO<SUB>2</SUB>/FTO electrode in the presence of oxalate confirms the LMCT mechanism in the oxalate-TiO<SUB>2</SUB> complex under visible light. Kinetic studies with varying oxalate concentrations, initial pH values, and TiO<SUB>2</SUB> types demonstrate that the oxidation efficiency increases as the adsorption of oxalate and the molar fraction of O<SUB>2</SUB> <SUP> −</SUP> increase. Not only ranitidine but also other pharmaceutical pollutants, such as cimetidine, propranolol, imidazole, and nizatidine, were oxidized in the pure TiO<SUB>2</SUB>/oxalate/visible light system. The oxidation efficiency of the oxalate-TiO<SUB>2</SUB> complex was higher than that of other organic ligand-TiO<SUB>2</SUB> complexes (i.e., citrate-, EDTA-, malonate-, acetate-, and glucose-TiO<SUB>2</SUB> complexes). In this regard, the pure TiO<SUB>2</SUB>/oxalate/visible light system can be proposed as a practical method for the treatment of pharmaceutical-contaminated water and wastewater.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Oxidation of ranitidine proceeds on pure TiO<SUB>2</SUB> with oxalate under visible light. </LI> <LI> Oxalate-TiO<SUB>2</SUB> complex absorbs visible light and initiates interfacial electron transfer. </LI> <LI> O<SUB>2</SUB> <SUP> −</SUP>/HO<SUB>2</SUB> <SUP> </SUP> is primarily involved in the oxidation of ranitidine among various ROS. </LI> <LI> Various pharmaceuticals are oxidized in the pure TiO<SUB>2</SUB>/oxalate/visible light system. </LI> <LI> Oxalate-TiO<SUB>2</SUB> complex is more efficient than other organic ligand-TiO<SUB>2</SUB> complexes. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Visible light photocatalysis of fullerol-complexed TiO₂ enhanced by Nb doping

Lim, J.,Monllor-Satoca, D.,Jang, J.S.,Lee, S.,Choi, W. Elsevier 2014 Applied Catalysis B Vol.152 No.-

Visible light photocatalysis by TiO<SUB>2</SUB> nanoparticles modified with both fullerol complexation and Nb-doping (fullerol/Nb-TiO<SUB>2</SUB>) demonstrated an enhanced performance. Nb-doped TiO<SUB>2</SUB> (Nb-TiO<SUB>2</SUB>) was firstly prepared by a conventional sol-gel method, and subsequently fullerol was adsorbed on the surface of Nb-TiO<SUB>2</SUB>. The physicochemical and optical properties of as-prepared fullerol/Nb-TiO<SUB>2</SUB> were analyzed by various spectroscopic methods (TEM, EELS, XPS, and DRS). The adsorption of fullerol on Nb-TiO<SUB>2</SUB> surface increased the visible light absorption through a surface-complex charge-transfer (SCCT) mechanism. Nb-doping enhanced the charge transport and induced the Ti cation vacancies that retarded the recombination of photo-generated charge pairs by trapping the electrons injected from the HOMO level of fullerol. Due to the advantage of simultaneous modification of fullerol and Nb-doping, the visible light photoactivity of fullerol/Nb-TiO<SUB>2</SUB> was more enhanced than either Nb-TiO<SUB>2</SUB> or fullerol/TiO<SUB>2</SUB>. The photocatalytic activities of fullerol/Nb-TiO<SUB>2</SUB> for the reduction of chromate (Cr<SUP>VI</SUP>), the oxidation of iodide, and the degradation of 4-chlorophenol were all higher than bare TiO<SUB>2</SUB> and singly modified TiO<SUB>2</SUB> (i.e., Nb-TiO<SUB>2</SUB> and fullerol/TiO<SUB>2</SUB>) under visible light (λ>420nm). A similar result was also confirmed for their photoelectrochemical behavior: the electrode made of fullerol/Nb-TiO<SUB>2</SUB> exhibited an enhanced photocurrent under visible light. On the other hand, the decay of open-circuit potential of the fullerol/Nb-TiO<SUB>2</SUB> electrode after turning off the visible light was markedly slower than either that of Nb-TiO<SUB>2</SUB> or fullerol/TiO<SUB>2</SUB>, which implies the retarded recombination of photo-generated charge pairs on fullerol/Nb-TiO<SUB>2</SUB>. In addition, the electrochemical impedance spectroscopic (EIS) data supported that the charge transfer resistance is lower with the fullerol/Nb-TiO<SUB>2</SUB> than either Nb-TiO<SUB>2</SUB> or fullerol/TiO<SUB>2</SUB>. This specific combination of the bulk (Nb-doping) and surface (fullerol complexation) modifications of titanium dioxide might be extended to other cases of bulk+surface combined modifications.

Visible-light photocatalytic reduction of Cr(VI) via carbon quantum dots-decorated TiO₂ nanocomposites

Choi, Dayeon,Ham, Sooho,Jang, Du-Jeon Elsevier 2018 Journal of environmental chemical engineering Vol.6 No.1

<P><B>Abstract</B></P> <P>Carbon quantum dots (CQDs) having sizes of 5–10nm have been prepared facilely by a hydrothermal method and incorporated with TiO<SUB>2</SUB> nanoparticles to produce CQDs-decorated TiO<SUB>2</SUB> (C/TiO<SUB>2</SUB>) nanocomposites with various dosages of CQDs. Under visible-light irradiation, the photocatalytic activities of Cr(VI) reduction via C/TiO<SUB>2</SUB> nanocomposites have been monitored and found to depend highly on the dosage of CQDs. In particular, the photocatalytic rate constant (0.0449min<SUP>−1</SUP>) of C/TiO<SUB>2</SUB> nanocomposites with 3wt% CQDs is 8.6 times higher than that of pure TiO<SUB>2</SUB> nanoparticles. When CQDs are excited by visible light, photo-generated electrons transfer from CQDs into the conduction band of TiO<SUB>2</SUB> on the time scale of 1500ps. Transferred electrons are subsequently captured by Cr(VI) ions, reducing Cr(VI) into Cr(III). Thus, π-conjugated CQDs act as sensitizers to provide visible-light response to the TiO<SUB>2</SUB> nanoparticles of C/TiO<SUB>2</SUB> dyade structures, leading to the highly efficient photocatalytic reduction of Cr(VI). Our as-prepared C/TiO<SUB>2</SUB> nanocomposites are applicable in an inexpensive way to treat wastewater by utilizing solar energy without employing electron donors.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CQDs-decorated TiO<SUB>2</SUB> (C/TiO<SUB>2</SUB>) nanocomposites were prepared by hydrothermal treatment. </LI> <LI> The visible-light photoreduction of Cr(VI) via C/TiO<SUB>2</SUB> depends on dosages of CQDs. </LI> <LI> CQDs act as photosensitizers to provide visible-light response to TiO<SUB>2</SUB>. </LI> <LI> Photo-generated electrons transfer from CQDs to TiO<SUB>2</SUB> on the time scale of 1500ps. </LI> <LI> C/TiO<SUB>2</SUB> nanocomposites may be applied to treat wastewater under visible light. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Visible light-activated degradation of natural organic matter (NOM) using zinc-bismuth oxides-graphitic carbon nitride (ZBO-CN) photocatalyst: Mechanistic insights from EEM-PARAFAC

Truong, Hai Bang,Huy, Bui The,Ly, Quang Viet,Lee, Yong-Ill,Hur, Jin Elsevier 2019 CHEMOSPHERE - Vol.224 No.-

<P><B>Abstract</B></P> <P>In this study, the complex degradation behavior of natural organic matter (NOM) was explored using photocatalytic oxidation systems with a novel catalyst based on a hybrid composite of zinc-bismuth oxides and g-C<SUB>3</SUB>N<SUB>4</SUB> (ZBO-CN). The photooxidation system demonstrated the effective removal of NOM under low-intensity visible light irradiation, presenting removal rates of 53–74% and 65–88% on the basis of dissolved organic carbon (DOC) and the UV absorption coefficient (UV<SUB>254</SUB>), respectively, at 1.5 g/L of the catalyst. The NOM removal showed an increasing trend with a higher ZBO-CN dose. Comparative experiments with the hole and <SUP> </SUP>OH radical scavengers revealed that the direct oxidation occurring on the catalyst's surface might be the governing photocatalytic mechanism. Fluorescence excitation emission matrix-parallel factor analysis (EEM-PARAFAC) revealed the individual removal behavior of the different constituents in bulk NOM. Different tendencies towards preferential adsorption and subsequent oxidative removal were found among dissimilar fluorescent components within a bulk terrestrial NOM, following the order of terrestrial humic-like (C1) > humic-like (C2) > microbial humic-like (C3) components. The result suggests the dominant operation of π-π and/or hydrophobic interactions between the NOM and the catalyst. The discriminative removal behavior was more pronounced in visible light versus UV-activated systems, probably due to the incapability of visible light to excite è - h<SUP>+</SUP> pairs of ZnO and the triplet state of NOM. The high photoactivity and structural stability of ZBO-CN under visible light implies its potential for an effective, low-cost and energy-saving treatment technology to selectively remove large sized humic-like substances from water.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel photocatalyst, ZBO-CN, showed a good performance in NOM removal. </LI> <LI> First study of NOM removal using g-C<SUB>3</SUB>N<SUB>4</SUB>-based photocatalyst under visible light. </LI> <LI> Direct oxidation on the catalyst operates as a dominant removal mechanism. </LI> <LI> Selective removal is more pronounced for visible light vs. UV-activated systems. </LI> <LI> ZBO-CN system can be an effective energy-saving technology for NOM removal. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

졸-겔법으로 제조된 Bismuth ferrite의 가시광 광촉매 특성

박병건 ( Byung-geon Park ),정경환 ( Kyong-hwan Chung ) 한국화학공학회 2020 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.58 No.3

가시광 LED 빛에 반응하는 페로브스이트형 bismuth ferrite (BFO) 광촉매 제조방법과 가시광 광촉매 반응 특성을 조사하였다. BFO는 졸-겔법에 따라 제조하였다. 제조된 BFO는 주로 BiFeO₃ 구조로 이루어져 있으며 Bi₂₄Fe₂O₃₉ 구조도 포함한 나노 크기의 결정을 이루고 있었다. BFO 나노 결정은 약 600 nm까지 자외선과 가시광선을 흡수하는 것을 UV-visible 확산 반사 스펙트럼으로부터 확인하였다. 확산 반사 스펙트럼으로부터 구한 BFO의 밴드갭은 약 2.2 eV로 나타났다. 포름알데히드는 585 nm와 613 nm 파장의 가시광 LED 램프의 빛과 BFO 광촉매와의 광반응에 의하여 분해되어 제거되었다. BFO의 가시광 LED 빛에서 광촉매 활성은 BFO의 좁은 밴드갭에서 기인하는 것으로 보인다. The method for preparing a perovskite-type bismuth ferrite (BFO) photocatalyst which reacts to visible LED light and the characteristics of visible light photocatalysis were investigated. BFO was prepared according to the sol-gel method. The prepared BFO consisted mainly of BiFeO₃ structure and formed a nano-sized crystal including Bi₂₄Fe₂O₃₉ structure. The BFO nano crystallines were identified from the UV-visible diffuse reflectance spectra to absorb UV and visible light up to about 600 nm. The bandgap of the BFO determined from the diffuse reflectance spectrum was about 2.2 eV. Formaldehyde was decomposed by the photoreaction of BFO photocatalysts with the visible light LED lamps with wavelengths of 585 nm and 613 nm. The narrow bandgap of BFO led to elicit BFO photocatalytic activity in visible LED light.

Modeling green-light fiber amplifiers for visible-light communication systems

Muhammad Hanif Ahmed Khan Khushik,Chun Jiang 한국광학회 2019 Current Optics and Photonics Vol.3 No.2

The visible-light communication (VLC) system is a promising candidate to fulfill the present and future demands for a high-speed, cost-effective, and larger-bandwidth communication system. VLC modulates the visible-light signals from solid-state LEDs to transmit data between transmitter and receiver, but the broadcasting and the line-of-sight propagation nature of visible-light signals make VLC a communication system with a limited operating range. We present a novel architecture to increase the operating range of VLC. In our proposed architecture, we guide the visible-light signals through the fiber and amplify the dissipated signals using visible-light fiber amplifiers (VLFAs), which are the most important and the novel devices needed for the proposed architecture of the VLC. Therefore, we design, analyze, and apply a VLFA to VLC, to overcome the inherent drawbacks of VLC. Numerical results show that under given constant conditions, the VLFA can amplify the signal up to 35.0 dB. We have analyzed the effects of fiber length, active ion concentration, pump power, and input signal power on the gain and the noise figure (NF).

빛에 의한 색채표시에 대한 연구

변수진 ( Byun Su Jin ) 전남대학교 예술연구소 2013 藝術論集 Vol.13 No.-

The color does not exist if there is no light. The light is the kind of the electromagnetic waves caused y sun energy. Human can feel the some light field as a color, which is called ‘visible light’ between the 380nm~780nm of the entire light frequency area. To feel the color, there should have the light of visible ray field, the object which reflect or absorb the light, and the eye which recognize that object. So, we feel the color by looking at the specific color in our eyesight, when the object reflect or absorb visible light selectively by its own choice. When the object is lightened, it gets the specific color according to reflectance of light wavelength. For example, red object absorb the purple~yellow light, and it only reflect the red light, so we can see that object as a red object. The color specification is defined to classify the color quantitatively, and the value of that classification is called as color specification values. Also color system is defined as the system of serial rules and definition for color specification. The color system is consist of color appearance system and color mixing system. The color appearance system is the method that display the color as a mathematical value for the basis of mixing color. CIE color system is typical method of color appearance system. Color mixing system is the method that classify the color by using the psychology of the human perception. The Muncell`s color system by hue, value, and Chroma is the representative method of color mixing system. The humans gather the important part of the information by using the vision. The color is the very important source at information-delivery system of vision. The color goes through the very complicated recognition process, and the light is very important role in that part. In this study, for understanding of the color, we want to organize color specification and color system of light property systemically.