本研究分析吖啶橙吸附於黏土礦物之可見光吸收與螢光光譜，以瞭解吖啶橙初始濃度和吸附量與其分子聚集形態及黏土礦物特性之關係，並獲取可產生強螢光之最佳吸附量，所使用之黏土礦物包含蒙脫石、累托石、伊萊石、高嶺石和禾樂石，半晶胞化學式單位單層負層電荷分別為0.504、0.6、0.84、0.06和0，比表面積為84.34、19.85、19.94、9.47及59.11 m2/g，等溫吸附實驗顯示吖啶橙最大吸附量分別為1.141、0.428、0.092、0.067與0.126 mmol/g。
本研究設定吖啶橙之低初始濃度為1×10-6、5×10-6、1×10-5、2×10-5、4×10-5、8×10-5和1×10-4 M，四種黏土礦物完全吸附後之吸附量均為0.3、1.5、3.0、6.0、12、24和30 μmol/g，高嶺石吸附量則為0.3、1.5、3.0、5.6、10.2、20和25 μmol/g，即每一種黏土礦物皆具有近乎相同的七種吸附量，可見光吸收與螢光光譜分析使用吸附後之乾燥黏土粉末。等吸附量但不同初始濃度之試驗以1次吸附1×10-4 M與重複吸附20次5×10-6 M吖啶橙溶液行之，取得相同的0.03 mmol/g吸附量（高嶺石0.025 mmol/g）。
可見光吸收光譜分析顯示吖啶橙吸附於五種黏土礦物可具有單體、雙聚體和H型與J型多聚體吸收峰特徵，吸收度分析顯示單體與雙聚體比例隨吸附量增加逐漸下降，H型與J型多聚體比例則上升。相較於初始濃度吖啶橙水溶液，吸附於黏土礦物之吖啶橙的單體與雙聚體吸收度明顯較低，H型與J型多聚體則較高，但與各礦物層電荷和比表面積未呈現系統性關聯性或趨勢。
吖啶橙吸附於黏土礦物可呈現波長~545 nm、~613 nm和~580 nm之單體、雙聚體和X螢光峰，在測試濃度範圍內，單體螢光峰強度最顯著，雙聚體與X螢光峰出現於吖啶橙初始濃度高於4×10-5 M（≥ 12 μmol/g吸附量）之黏土礦物樣品。蒙脫石、累托石及伊萊石吸附吖啶橙之單體螢光峰強度較等溫吸附之高初始濃度和高吸附量樣品為低，但單體螢光峰強度比例遠較為高。高嶺石和禾樂石之單體螢光峰強度和強度比例均較高吸附量樣品為高，高嶺石獲致單體螢光峰強度比例最高之吖啶橙初始濃度為1×10-5–4×10-5 M，強度高於等溫吸附高初始濃度樣品之單體螢光峰強度，禾樂石獲致最高單體螢光峰強度之吖啶橙初始濃度為1×10-5–2×10-5 M，強度約為高初始濃度樣品單體螢光峰強度之3–4倍。低初始濃度多次吸附與高初始濃度單次吸附之等吸附量黏土礦物樣品呈現相似之吸收光譜及螢光光譜特性，顯示多次吸附亦會影響分子聚集狀態和光譜性質。
以上結果顯示使用低初始濃度和低載量確可對增加吸附於黏土礦物之吖啶橙單體螢光峰的比例，但僅在吖啶橙吸附於未具層電荷和具有高比表面積禾樂石之情況，可同時顯著增加單體螢光峰強度，具體取得產生最強螢光之最佳初始濃度。

Absorption and fluorescence spectra of acridine orange (AO) adsorbed on montmorillonite (SAz-2), rectorite (REC), illite (IMt-2), kaolinite (KGa-1b), and halloysite nanotubes (HNT) at AO concentrations of 10-6–10-4 M were measured to test for the variations of aggregation state and fluorescence properties of AO molecules. While the proportions of AO monomers were significantly increased with the low AO concentrations, the fluorescence intensities of AO monomers adsorbed on SAz-2, REC, and IMt-2 were lower than those measured on the same clays with high AO loadings. In contrast, the fluorescence intensity of AO monomer reached a maximum upon adsorption on KGa-1b and HNT with initial concentrations of 1–4 × 10-5 M and 1–2 × 10-5 M, respectively. AO adsorbed on HNT utilizing the low concentration yielded fluorescence 3–4 times more intense than that obtained from AO loaded on HNT at its full adsorption capacity. Among all the studied clays, HNT having a high surface area and virtually no layer charge exhibited the best fluorescence performance from adsorbed AO monomers when low initial AO concentrations were used.
INTRODUCTION

Using adsorption spectrum to describe the interaction of dyes and clays has been studied. It showed that dye could formed different aggregation by clay’s improved like monomer, dimer, trimer, H-type aggregate and J-type aggregate. Compared with there were only monomer and dimer of most dye in solution. It reported that the layer charge, initial concentration of dye and reaction time were the major impact factor of dye aggregation. The methylene blue had detailed studied with smectite group clays. But it was still unknown of other group clays of the interaction to dyes. So we used acridine orange and selected three types of clays : montmorillonite, rectorite, illite, kaolinite and halloysite for this issue. We wanted to identified what impact factor in other groups of clay could change the dye aggregation using adsorption spectrum. We chose AO was the reason that it had not only monomer but also dimer fluorescence peak. We also wanted to observed the varity of fluorescence spectrum of the clay sample adsorbed dyes and found the best concentration to obtain the highest fluorescence counts.

MATERIALS AND METHODS

The AO used was in a ZnCl2 form with a molecular weight of 438.1 g/mol. It was purchased from Alfa Aesar. The SAz-2 montmorillointe, IMt-2 illite, KGa-1 kaolinite clay were obtained from the Source Clay Minerals Repository. The rectorite was obtained from Zhongxiang, Hubei, China and the halloysite were purchased from Sigma-Aldrich. SAz-2, Rec, IMt-2, KGa-1, Hal had reported cation exchange capacity (CEC) of 123, 43.7, 13.5, 2, 11 meq/100g. We analyzed the specific surface area (SSA) of 84.34, 19.85, 19.94, 9.47, 59.11 m2/g. The clay had reported layer charge of 0.504, 0.6, 0.84, 0.06 ( per (Si, Al)4O10). Layer charge of Hal had found no report of it.

To each 50 mL centrifuge tube, 0.1 g of clay and 30 mL AO solution were combined for the experiment. For the same adsorbed amount effect experiment the initial concentrations of AO were 1×10-6 M to 1×10-4 M. And the isotherm experiment had the initial concentrations of AO were 5×10-4 M to 5×10-3 M. (For the lager CEC value of SAz-2, the initial concentration changed to 1×10-3 M to 1×10-2 M). For initial concentration effect experiment, we had three samples. First for 1×10-4 M 30 ml AO solution mixed with clay. Second was 5×10-6 M repeat 20 times to reached as the same adsorbed of 1×10-4 M’s experiment. Last was 5×10-6 M 30 ml mixed one time to differ form second sample. The mixtures were shaken on a reciprocal shaker at 150 rpm at room temperature for 24 h. The centrifuge tubes were wrapped with aluminum foils to prevent the photodegradation of AO, if any. After mixing, samples were centrifuged at 5000 rpm for 10 min and the supernatant was passed through 0.45 μm filters being analyzed for equilibrium AO concentrations by a UV-Vis method. The residual solid were collected and dired in room temperature for 1 day avoid sunlight.

The equilibrium AO concentrations were determined via a UV–vis spectrophotometer at the wavelength of 490 nm. Adsorption spectrum using an integrating sphere for resudial solid of adsorption experiment. The wavelength varied from 400 to 700 nm. Fluorescence measurement were made on self-assembly spectrometer with an excitation at 490 nm.

RESULTS AND DISCUSSION

The AO solution adsorption spectrum showed a main monomer adsorption peak at 490nm and a shoulder dimer adsorption peak at 460 nm. For adsorption spectrum of clay after adsorbed AO, it showed that there were four kinds of aggregates like monomer, dimer, H-aggregate and J-aggregate. Absorbance data presented that the proportion of monomer and dimer were decreased as the adsorbed amounts added, while the proportion of H-aggregate and J-aggregate were increased. Compared with the AO solution, the absorbance of monomer and dimer obviously lower for AO adsorbed on clays. And the absorbance of H-aggregate and J-aggregate were higher. But we didn’t find systematic relationship and trend for each clay’s layer charge and specific surface area .

AO adsorbed on clays showed three different fluorescence peak, monomer (~545 nm), dimer (~613 nm) and a unknown peak (X, ~580 nm). At the detected concentration range, the monomer fluorescence was the significant one and the dimer and X fluorescence peak were appeared at the clay sample of initial concentration higher than 4×10-5 M (adsorbed amount ≥ 12 μmol/g). For SAz-2, Rec, IMt-2 sample, the monomer fluorescence counts was lower than isotherm experiment’s high initial concentration and adsorbed sample, but the proportion was higher. Both of the monomer fluorescence and proportion were higher than high adsorebed amount sample for KGa-1 and Hal. The AO concentration range of highest monomer fluorescence proportion were 1×10-5–4×10-5 M for KGa-1. The fluorescence counts were also higher than isotherm sample. For Hal sample, the AO concentration range of highest monomer fluorescence counts were 1×10-5–2×10-5 M. The fluorescence counts were about 3-4 times of the high initial concentration sample. These results also showed at the fluorescence image. No matter under UVA or UVC, the low initial concentration sample’s fluorescence brightness was higher than high initial concentration at the detected concentration range.

Initial concentration effect experiment showed that it didn’t matter about the initial concentration at the same adsorbed amount situtation of high layer charge clays. It had less change of the adsorption and fluorescence spectrum. But the low layer charge clay of KGa-1 and Hal had obvious change. The dimer absorbance declined at the low initial concentration experiment and the dimer fluorescence intensity also decreased. Showed that AO aggregation in aqueous solution effect the AO aggregation type after adsorbed on low layer charge clay.

Conclusion

(1) For adsorption isotherm, five clays all well fitted Langmuir adsorption model and reached the maximum adsorded amount of 1.140、0.427、0.091、0.006、0.126 mmol/g for SAz-2, Rec, IMt-2, KGa-1 and Hal.
(2) For adsorption spectrum, it showed monomer, dimer, H-typed aggregate and J-typed aggregate adsorption peak in all five clay sample. The high aggregation appeared at high adsorbed amount samples.
(3) In fluorescence spectrum we distinguish a new fluorescence peak at the wavelength between monomer and dimer fluorescence peak. The monomer fluorescence proportion was the highest for all clays at low loading samples. The AO concentration range for highest fluorescence were 1×10-5–4×10-5 M for SAz-2, Rec, IMt-2, KGa-1 and were 1×10-5–2×10-5 M for Hal. Similar results showed at fluorescence image under UVA.
(4) Using low initial concentration and low loading could truely improved the monomer fluorescence proportion. But it only for AO adsorbed on Hal, low layer charge and high specific surface area clay.

A. Czímerová, J. Bujdák, A. Gáplovský, The aggregation of thionine and methylene blue dye in smectite dispersion. Colloids and Surfaces A: Physicochem. Eng. Aspects, 2004, 243, 89– 96.
A. Czímerová, L. Jankovič, J. Bujdák, Effect of the exchangeable cations on the spectral properties of methylene blue in clay dispersions. Journal of Colloid and Interface Science, 2004, 274, 126– 132.
A. Czímerová, J. Bujdák, R. Dohrmann, Traditional and novel methods for estimating the layer charge of smectites. Applied Clay Science, 2006, 34, 2– 13.
A. Czímerová, J. Bujdák, N. Iyi, Fluorescence resonance energy transfer between Laser dyes in saponite dispersions. Journal of Photochemistry and Photobiology A: Chemistry, 2007, 187, 160– 166.
A. Czímerová, N. Iyi, J. Bujdák, Fluorescence resonance energy transfer between two cationic laser dyes in presence of the series of reduced- charge montmorillonites: Effect of the layer charge. Journal of Colloid and Interface Science, 2008, 140– 151.
A. Gil, Y. E. Mouzdahir, A. Elmchaouri, M. A. Vicente, S. A. Korili, Equilibrium and thermodynamic investigation of methylene blue adsorption on thermal- and acidactivated clay minerals. Desalination and Water Treatment, 2013, 51, 2881– 2888.
A. Gürses, Ç. Doğar, M. Yalçın, M. Açıkyıldız, R. Bayrak, S. Karaca, The adsorption kinetics of the cationic dye, methylene blue, onto clay. Journal of Hazardous Materials, 2006, 131, 217– 228.
A. H. Gemeay, A. S. El- Sherbiny, A. B. Zaki, Adsorption and kinetic studies of the intercalation of some organic compounds onto Na+- montmorillonite. Journal of Colloid and Interface Science, 2002, 245, 116– 125.
A. H. Gemeay, Adsorption characteristics and the kinetics of the cation exchange of rhodamine- 6G with Na+- montmorillonite. Journal of Colloid and Interface Science, 2002, 251, 235– 241.
A. K. Ghosh, A. Samanta, P. Bandyopadhyay, Anionic micelle- induced fluorescent sensor activity enhancement of acridine orange: Mechanism and pH effect. Chemical Physics Letters, 2011, 507, 162– 167.
A. Landau, A. Zaban, I. Lapides, S. Yariv, Montmorillonite treated with rhodamine- 6G mechanochemically and in aqueous suspensions. Simultaneous DTA-TG study. Journal of Thermal Analysis and Calorimetry, 2002, 70, 103– 113.
A. M. Amado, A. P. Ramos, E. R. Silva, I. E. Borissevitch, Quenching of acridine orange fluorescence by salts in aqueous solutions: Effects of aggregation and charge transfer. Journal ofLuminescence, 2016, 178, 288– 294.
A. M. Wiosetek- Reske, S. Wysocki, Spectral studies of N- nonyl acridine orange in anionic, cationic and neutral surfactants. Spectrochimica Acta Part A, 2006, 64, 1118– 1124.
A. P. P. Cione, M. G. Neumann, F. Gessner, Time-dependent spectrophotometric study of the interaction of basic dyes with clays. Journal of Colloid and Interface Science, 1998, 198, 106– 112.
A. Shil, S. A. Hussain, D. Bhattacharjee, Adsorption of a water soluble cationic dye into a cationic Langmuir monolayer. Journal of Physics and Chemistry of Solids, 2015, 80, 98– 104.
A. U. C. Ferreria, A. L. Poli, F. Gessner, M. G. Neumann, C. C. S. Cavalherio, Interaction of Auramine O with montmorillonite clays. Journal of Luminescence, 2013, 136, 63– 67.
B. A. Fil, M. Korkmaz, C. Özmetin, Application of nonlinear regression analysis for methyl violet (MV) dye adsorption from solutions onto illite clay. Journal of Dispersion Science and Technology, 2016, 37, 991– 1001.
B. Liu, Z. Liu, Z. Cao, Fluorescence resonance energy transfer between acridine orange and rhodamine 6G and analytical application in micelles of dodecyl benzene sodium sulfonate. Journal of Luminescence, 2006, 118, 99– 105.
B. Singh, I. D. R. Mackinnon, Experimental transformation of kaolinite to halloysite. Clays and Clay Minerals, 1996, Vol. 44. No. 6, 825– 834.
B. Valeur, M. N. Berberan-Santos, Molecular Fluorescence: Principles and Applications, Second edition. Wiley-VCH, 2012, 569pp.
C. A. P. Almeida, N. A. Debacher, A. J. Downs, L. Cottet, C. A. D. Mello, Removal of methylene blue from colored effluents by adsorption on montmorillonite clay. Journal of Colloid and Interface Science, 2009, 332, 46– 53.
C. Chakraborty, P. K. Sukul, K. Dana, S. Malik, Suppression of Keto defects and thermal stabilities of polyfluorene− kaolinite clay nanocomposites. Ind. Eng. Chem. Res., 2013, 52, 6722– 6730.
C. Hansda, U. Chakraborty, S. A. Hussain, D. Bhattacharjee, P. K. Paul, Layer-by-layer films and colloidal dispersions of graphene oxide nanosheets for efficient control of the fluorescence and aggregation properties of the cationic dye acridine orange. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2016, 157, 79– 87.
C. H. Yu, S. Q. Newton, M. A. Norman, D. M. Miller, L. Schäfer, B. J. Teppen, Molecular dynamics simulations of the adsorption of methylene blue at clay mineral surfaces. Clays and Clay Minerals, 2000, 48, 6, 665– 681.
C. H. Yu, S. Q. Newton, M. A. Norman, L. Schäfer, D. M. Miller, Molecular dynamics simulations of adsorption of organic compounds at the clay mineral/ aqueous solution interface. Structural Chemistry, 2003, 14, 175– 185.
C. M. Bethke, N. Vergo, S. P. Altaner, Pathways of smectite illitization. Clays and clay minerals, 1986, Vol. 34, 2, 125– 135.
C. Peyratout, E. Donath, L. Daehne, Electrostatic interactions of cationic dyes with negatively charged polyelectrolytes in aqueous solution. Journal of Photochemistry and Photobiology A: Chemistry, 2001, 142, 51– 57.
D. B. Davies, L. N. Djimant, A. N. Veselkov, 1H NMR investigation of self- association of aromatic drug molecules in aqueous solution. J . Chem. SOC., Faraday Trans., 1996, 92, 383– 390.
D. Garfinkel– Shweky, S. Yariv, Metachromasy in clay-dye systems: the adsorption of acridine orange by Na-saponite. Clay Minerals, 1997, 32, 653– 663.
D. Ghosh, K. G. Bhattacharyya, Adsorption of methylene blue on kaolinite. Applied Clay Science, 2002, 20, 295– 300.
D. R. Falcone, N. M. Correa, M. A. Biasutti, J. J. Silber, Acid-base and aggregation processes of acridine orange base in n-heptane/AOT/water reverse micelles. Langmuir, 2002, 18, 2039– 2047.
D. Wu, P. Zheng, P. R. Chang, X. Ma, Preparation and characterization of magnetic rectorite/ iron oxide nanocomposites and its application for the removal of the dyes. Chemical Engineering Journal, 2011, 174, 489– 494.
E. H. Hill, Y. Zhang, D. G. Whitten, Aggregation of cationic ρ- phenylene ethynylenes on laponite clay in aqueous dispersions and solid films. Journal of Colloid and Interface Science, 2015, 449, 347– 356.
E. Joussein, S. Petit, J. Churchman, B. Theng, D. Righi, B. Delvaux, Halloysite clay minerals– a review. Clay Minerals, 2005, 40, 383– 426.
E. R. Johnson, A. Otero- de- la- Roza, Adsorption of organic molecules on kaolinite from the exchange- hole dipole moment dispersion model. J. Chem. Throry Comput., 2012, 8, 5124– 5131.
F. Bessaha, K. Marouf- Khelifa, I. Batonneau- Gener, A. Khelifa, Characterization and application of heat- treated and acid-leached halloysites in the removal of malachite green: adsorption, desorption, and regeneration studies. Desalination and Water Treatment, 2016, 57, 14609– 14621.
F. Gessner, C. C. Schmitt, M. G. Neumann, Time-dependent spectrophotometric study of the interaction of basic dyes with clays. 1. Methylene blue and neutral red on montmorrillonite and hectorite. Langmuir, 1994, 10, 3749– 3753.
F. L. Arbeloa, R. Chaudhuri, T. A. López, I. L. Arbeloa, Aggregation of rhodamine 3B adsorbed in Wyoming montmorillonite aqueous suspensions. Journal of Colloid and Interface Science, 2002, 246, 281– 287.
F. L. Arbeloa, V. M. Martínez, J. B. Prieto, I. L. Arbeloa, Adsorption of rhodamine 3B dye on saponite colloidal particles in aqueous suspensions. Langmuir, 2002, 18, 2658– 2664.
F. L. Arbeloa, V. M. Martínez, Orientation of adsorbed dyes in the interlayer space of clays. 2 Fluorescence polarization of rhodamine 6G in laponite films. Chem. Mater., 2006, 18, 1407– 1416.
F. L. Arbeloa, V. M. Martínez, T. Arbeloa, I. L. Arbeloa, Photoresponse and anisotropy of rhodamine dye intercalated in ordered clay layered films. Journal of Photochemistry and Photobiology C: Photochemistry Reviews, 2007, 8, 85– 108.
F. Wilkinson, D. R. Worrall, Photochemistry on surfaces: fluorescence emission of monomers and dimers and triplet state absorption of acridine orange adsorbed on microcrystalline cellulose. Specmchimica Acta, 1992, 48, 135– 145.
G. Chen, J. Pan, B. Han, H. Yan, Adsorption of methylene blue on montmorillonite. Journal of Dispersion Science and Technology, 1999, 20, 1179– 1187.
G. K. Sarma, S. S. Gupta, K. G. Bhattacharyya, Methylene blue adsorption on natural and modified clays. Separation Science and Technology, 2011, 46, 1602– 1614.
G. K. Sarma, S. S. Gupta, K. G. Bhattacharyya, Adsorption of crystal violet on raw and acid- treated montmorillonite, K10, in aqueous suspension. Journal of Environmental Management, 2016, 171, 1– 10.
G. Lagaly, The "layer charge" of regular interstratified 2:1 clay minerals. Clays and clay minerals, 1979, Vol. 27, 1, 1– 10.
G. Lv, Z. Li, W. T. Jiang, P. H. Chang, J. S. Jean, K. H. Lin, Mechanism of acridine orange removal from water by low- charge swelling clays. Chemical Engineering Journal, 2011, 174, 603– 611.
G. Lv, L. Wu, L. Liao, W. T. Jiang, Z. Li, Intercalation and configurations of organic dye acridine orange in a high-charge montmorillonite as influenced by dye loading. Desalination and Water Treatment, 2014, 52, 7323– 7331.
G. Rytwo, E. R. Hitzky, Enthalpies of adsorption of methylene blue and crystal violet to montmorillonite: Enthalpies of adsorption of dyes to montmorillonite. Journal of Thermal Analysis and Calorimetry, 2003, 71, 751– 759.
G. S. Martynková, L. Kulhánková, P. Malý, P. Čapková, Fluorescence and structure of methyl red- clay nanocomposites. J. Nanosci. Nanotechnol., 2007, 8, 1– 6.
G. V. Henderson, Rectorite and the rectorite– like layer structures. Clays and Clay Minerals, 1970, Vol. 18, 115-119.
H. Awala, E. Leite, L. Saint– Marcel, G. Clet, R. Retoux, I. Naydenova, S. Mintova, Properties of methylene blue in the presence of zeolite nanoparticles. New J. Chem., 2016, 40, 4277– 4284.
H. Freundlich, Über die adsorption in Lösungen, Zeitschrift fr Physikalische Chemie, 1907, 57 A, 385– 470.
H. L. Hong, X. L. Zhang, M. Wan, Y. J. Hou, D. W. Du, Morphological characteristics of (K, Na)-rectorite from Zhongxiang rectorite deposit, Hubei, Central China. Journal of China University of Geosciences, 2008, Vol. 19, 1, 38– 46.
H. L. Hong, W. T. Jiang, X. Zhang, L. Tie, Z. Li, Adsorption of Cr(VI) on STAC- modified rectorite. Applied Clay Science, 2008, 42, 292– 299.
H. S. S. R. Matte, K. S. Subrahmanyam, K. V. Rao, S. J. George, C. N. R. Rao, Quenching of fluorescence of aromatic molecules by graphene due to electron transfer. Chemical Physics Letters, 2011, 506, 260– 264.
H. Yang, L. Weijun, W. Weiqing, F. Qiming, L. Jing, Synthesis of a carbon@Rectorite nanocomposite adsorbent by a hydrothermal carbonization process and their application in the removal of methylene blue and neutral red from aqueous solutions. Desalination and Water Treatment, 2016, 57, 13573– 13585.
I. Feddal, A. Ramdani, S. Taleb, E. M. Gaigneaux, N. Batis, N. Ghaffour, Adsorption capacity of methylene blue, an organic pollutant, by montmorillonite clay. Desalination and Water Treatment, 2014, 52, 2654– 2661.
J. A. Greathouse, D. L. Geatches, D. Q. Pike, H. C. Greenwell, C. T. Johnston, J. Wilcox, R. T. Cygan, Methylene blue adsorption on the basal surfaces of kaolinite: Structure and thermodynamics from quantum and classical molecular simulation. Clays and Clay Minerals, 2015, 63, 185– 198.
J. Bhattacharjee, S.A. Hussain, D. Bhattacharjee, Control of H-dimer formation of acridine orange using nano clay platelets. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2013, 116, 148– 153.
J. Bhattacharjee, S.A. Hussain, D. Bhattacharjee, Effect of nano clay platelets and DNA on controlling the H-dimer of oxazine 4 perchlorate (OX4) in LbL film. Appl. Phys. A, 2014, 116, 1669– 1676.
J. Bujdák, P. Komadel, Interaction of methylene blue with reduced charge Montmorillonite. J. Phys. Chem. B, 1997, 101, 9065– 9068.
J. Bujdák, M. Janek, J. Madejová, P. Komadel, Influence of the layer charge density of smectites on the interaction with methylene blue. J. Chem. Soc., Faraday Trans., 1998, 94, 3487– 3492.
J. Bujdák, M. Janek, J. Madejová, P. Komadel, Methylene blue interactions with reduced- charge smectites. Clays and Clay Minerals, 2001, 49, 244– 254.
J. Bujdák, N. Iyi, T. Fujita, The aggregation of methylene blue in montmorillonite dispersions. Clay Minerals, 2002, 37, 121– 133.
J. Bujdák, N. Iyi, T. Fujita, Aggregation and stability of 1, 1’- diethyl- 4, 4’- cyanine dye on the surface of layered silicates with different charge densities. Colloids and Surfaces A, 2002, 207, 207– 214.
J. Bujdák, N. Iyi, Y. Kaneko, R. Sasai, Molecular orientation of methylene blue cations adsorbed on clay surfaces. Clay Minerals, 2003, 38, 561– 572.
J. Bujdák, N. Iyi, Y. Kaneko, A. Czímerová, R. Sasai, Molecular arrangement of rhodamine 6G cations in the films of layered silicates: the effect of the layer charge. Phys. Chem. Chem. Phys., 2003, 5, 4680– 4685.
J. Bujdák, N. Iyi, R. Sasai, Spectral Properties, Formation of dye molecular aggregates, and reactions in rhodamine 6G/ layered silicate dispersions. J. Phys. Chem. B, 2004, 108, 4470– 4477.
J. Bujdák, N. Iyi, Molecular orientation of rhodamine dyes on surfaces of layered silicates. J. Phys. Chem. B, 2005, 109, 4608– 4615.
J. Bujdák, Effect of layer charge of clay minerals on optical properties of organic dyes. A review. Applied Clay Science, 2006, 34, 58– 73.
J. Bujdák, N. Iyi, Molecular aggregation of rhodamine dyes in dispersions of layered silicates: Influence of dye molecular structure and silicate properties. J. Phys. Chem. B, 2006, 110, 2180– 2186.
J. Bujdák, V. M. Martínez, F. L. Arbeloa, N. Iyi, Spectral properties of rhodamine 3B adsorbed on the surface of montmorillonites with variable layer charge. Langmuir, 2007, 23, 1851– 1859.
J. Bujdák, D. Chorvát, Jr., N. Iyi, Resonance energy transfer between rhodamine molecules adsorbed on layered silicate particles. J. Phys. Chem. C, 2010, 114, 1246– 1252.
J. Bujdák, A. Czímerová, F. L. Arbeloa, Two- step resonance energy transfer between dyes in layered silicate films. Journal of Colloid and Interface Science, 2011, 364, 497– 504.
J. Bujdák, N. Iyi, Highly fluorescent colloids based on rhodamine 6G, modified layered silicate, and organic solvent. Journal of Colloid and Interface Science, 2012, 388, 15– 20.
J. Cenens, R. A. Schoonheydt, Visible spectroscopy of methylene blue on hectorite, laponite b, and barasym in aqueous suspension. Clays and Clay Minerals, 1988, 36, 214– 224.
J. C. Stockert, P. D. Castillo, A. B. Castro, Induction of metachromasia in cationic dyes and fluorochromes using a clay mineral: A potentially valuable model for histochemical studies. Acta Histochemica, 2011, 113, 668– 670.
J. H. Ahn, D. R. Peacor, Transmission electron microscope data for rectorite: implications for the origin and structure of "fundamental particles '1. Clays and Clay Minerals, 1986, Vol. 34, No. 2, 180– 186.
J. H. Kirkman, Possible structure of halloysite disks and cylinders observed in some New Zealand rhyolitic tephras. Clay Minerals, 1977, 12, 199– 216.
J. He, S. Hong, L. Zhang, F. Gan, Y. S. Ho, Equilibrium and thermodynamic parameters of adsorption of methylene blue onto rectorite. Fresenius Environmental Bulletin, 2010, 19, 2651– 2656.
J. N. Ganguli, S. Agarwal, Removal of a basic dye from aqueous solution by a natural kaolinitic clay– adsorption and kinetic studies. Adsorption Science & Technology, 2012, 30, 171− 182.
J. R. Lakowicz, Principles of Fluorescence Spectroscopy, third edition. Springer US, 2006, 954 pp.
J. W. Davis, M. S. Kahl, T. D. Golden, Mechanistic study of cationic dye interactions with clay- polymer dispersions via metachromatic effect, aggregation, and surface charge. J. Appl. Polym. Sci, 2014, 40141.
K. A. Krishnan, K. Ajmal, A. K. Faisal, T. M. Liji, Kinetic and isotherm modeling of methylene blue adsorption onto kaolinite clay at the solid-liquid interface. Separation Science and Technology, 2015, 50, 1147– 1157.
K. Banerjee, P. Dureja,
K. Bergmann, C. T. O’Konski, A spectroscopic study of methylene blue monomer, dimer, and complexes with montmorillonite. J. Phys. Chem., 1963, 67, 10, 2169– 2177.
K. G. Bhattacharyya, S. SenGupta, G. K. Sarma, Interactions of the dye, rhodamine B with kaolinite andmontmorillonite in water. Applied Clay Science, 2014, 99, 7– 17.
K. Y. Jacobs, R. A. Schoonheydt, Spectroscopy of methylene blue– smectite suspensions. Journal of Colloid and Interface Science, 1999, 220, 103– 111.
L. Antonov, G. Gergov, V. Petrov, M. Kubista, J. Nygren, UV–Vis spectroscopic and chemometric study on the aggregation of ionic dyes in water. Talanta, 1999, 49, 99– 106.
L. Farzampour, M. Amjadi, Sensitiveturn- on fluorescence assay of methimazole based on the fluorescence resonance energy transfer between acridine orange and silver nanoparticles. Journal of Luminescence, 2014, 155, 226– 230.
L. Lu, R. M. Jones, D. Mcbranch, D. Whitten, Surface-enhanced superquenching of cyanine dyes as J-aggregates on laponite clay nanoparticles. Langmuir, 2002, 18, 7706– 7713.
L. Shi, D. Wei, H. H. Ngo, W. Guo, B. Du, Q. Wei, Application of anaerobic granular sludge for competitive biosorption of methylene blue and Pb(II): Fluorescence and response surface methodology. Bioresource Technology, 2015, 194, 297– 304.
L. Wu, G. Lv, M. Liu, Z. Li, L. Liao, C. Pan, Adjusting the layer charges of host phyllosilicates to prevent luminescence quenching of fluorescence dyes. J. Phys. Chem. C., 2015, 119, 22625− 22631.
L. Zeng, Q. Zhang, Y. Kang, X. Guo, J. Luo, X. Wang, Study on adsorption of methylene blue with organic rectorite. Integrated Ferroelectrics, 2013, 146, 29− 42.
L. Zeng, M. Xie, Q. Zhang, Y. Kang, X. Guo, H. Xiao, Y. Peng, J. Luo, Chitosan/ organic rectorite composite for the magnetic uptake of methylene blue and methyl orange. Carbohydrate Polymers, 2015, 123, 89− 98.
M. E. Lamm, D. M. Neville, Jr., The dimer spectrum of acridine orange hydrochloride. J. Phys. Chem., 1965, 69, 11, 3872– 3877.
M. G. Neumann, F. Gessner, C. C. Schmitt, R. Sartori, Influence of the layer charge and clay particle size on the interactions between the cationic dye methylene blue and clays in an aqueous suspension. Journal of Colloid and Interface Science, 2002, 255, 254– 259.
M. G. Neumann, H. P. M. Oliveira, P. P. Cione, Energy transfer between aromatic hydrocarbons dissolved in a C18-surfactant layer adsorbed on laponite. Adsorption, 2002, 8, 141– 146.
M. Grabolle, M. Starke, U. Resch– Genger, Highly fluorescent dye− nanoclay hybrid materials made from different dye classes. Langmuir, 2016, 32, 3506– 3513.
M. J. Avena, L. E. Valenti, V. Pfaffen, C. P. D. Pauli, Methylene blue dimerization does not interfere in surface- area measurements of kaolinite and soils. Clays and Clay Minerals, 2001, 49, 168– 173.
M. Lofaj, J. Bujdák, Detection of smectites in ppm and sub- ppm concentrations using dye molecule sensors. Phys. Chem. Minerals, 2012, 39, 227– 237.
M. M. Demir, B. Özen, S. Özçelik, Formation of pseudoisocyanine J-aggregates in poly(vinyl alcohol) fibers by electrospinning. J. Phys. Chem. B, 2009, 113, 11568– 11573.
M. Ogawa, R. Takee, Y. Okabe, Y. Seki, Bio- geo hybrid pigment; clay- anthocyanin complex which changes color depending on the atmosphere. Dyes and Pigments, 2017, 139, 561– 565.
M. R. Rostami, M. Kaya, B. Gür, Y. Onganer, K. Meral, Photophysical and adsorption properties of pyronin B in naturalbentonite clay dispersion. Applied Surface Science, 2015, 359, 897– 904.
M. Samuels, O. Mor, G. Rytwo, Metachromasy as an indicator of photostabilization of methylene blue adsorbed to clays and minerals. Journal of Photochemistry and Photobiology B: Biology, 2013, 121, 23– 26.
M. Sayed, B. Krishnamurthy, H. Pal, Unraveling multiple binding modes of acridine orange to DNA using a multispectroscopic approach. Phys.Chem.Chem.Phys., 2016, 18, 24642.
M. Zhao, P. Liu, Adsorption behavior of methylene blue on halloysite nanotubes. Microporous and Mesoporous Materials, 2008, 112, 419– 424.
N. Li, X. Hao, B. H. Kang, N. B. Li, H. Q. Luo, Sensitive and selective turn- on fluorescence method for cetyltrimethylammonium bromide determination based on acridine orange–polystyrene sulfonate complex. Luminescence, 2016, 31, 1025– 1030.
N. Sato, T. Fujimura, T. Shimada, T. Tani, S. Takagi, J-aggregate formation behavior of a cationic cyanine dye on inorganic layered material. Tetrahedron Letters, 2015, 56, 2902– 2905.
P. Boháč, A. Czímerová, J. Bujdák, Enhanced luminescence of 3, 3’- diethyl- 2, 2’- thiacyanine cations adsorbed on saponite particles. Applied Clay Science, 2016, 127– 128, 64– 69.
P. Čapková, P. Malý, M. Pospíšil, Z. Klika, H. Weissmannová, Z. Weiss, Effect of surface and interlayer structure on the fluorescence of rhodamine B– montmorillonite: modeling and experiment. Journal of Colloid and Interface Science, 2004, 277, 128– 137.
P. E. Rosenberg, J. A. Kittrick, S. U. Aja, Mixed– layer illite/smectite: A multiphase model. American Mineralogist, 1990, Vol. 75, l182– 1185.
P. H. B. Aoki, D. Volpati, W. Caetano, C. J. L. Constantino, Study of the interaction between cardiolipin bilayers and methylene blue in polymer-based Layer-by-Layer and Langmuir films applied as membrane mimetic systems. Vibrational Spectroscopy, 2010, 54, 93– 102.
P. Kovář, M. Pospíšil, P. Malý, Z. Klika, P. Čapková, P. Horáková, M. Valášková, Molecular modeling of surface modification of Wyoming and Cheto montmorillonite by methylene blue. J. Mol. Model, 2009, 15, 1391– 1396.
P. Luo, Y. Zhao, B. Zhang, J. Liu, Y. Yang, J. Liu, Study on the adsorption of neutral red from aqueous solution onto halloysite nanotubes. Water Research, 2010, 44, 1489– 1497.
P. Luo, B. Zhang, Y. Zhao, J. Wang, H. Zhang, J. Liu, Removal of methylene blue from aqueous solutions by adsorption onto chemically activated halloysite nanotubes. Korean J. Chem. Eng., 2011, 28, 800– 807.
P. Pustková, Z. Klika, J. Preclíková, T. M. Grygar, Enhanced fluorescence of selected cationic dyes adsorbed on reduced-charge montmorillonite. Clay Minerals, 2011, 46, 93– 103.
P. T. Hang, G. W. Brindley, Methylene blue absorption by clay minerals. Determination of surface areas and cation exchange capacities( Clay– Organic studies XVIII). Clays and Clay Minerals, 1970,Vol. 18, 203– 212.
R. A. Schoonheydt, L. Heughebaert, Clay adsorbed dyes: Methylene blue on laponite. Clay Minerals, 1992, 27, 91– 100.
R. Cohen, S, Yariv, Metachromasy in clay minerals. Sorption of acridine orange by montmorillonite. J. Chem. Soc., Faraday Trans. 1, 1984, 80, 1705– 1715.
R. Sasai, N. Iyi, T. Fujita, F. L. Arbeloa, V. M. Martínez, K. Takagi, H. Itoh, Luminescence properties of rhodamine 6G intercalated in surfactant/clay hybrid thin solid films. Langmuir, 2004, 20, 11, 4715– 4719.
R. Shrivastava, B. Jain, K. Das, Spectroscopic investigations on the binding of methylene blue and nile blue to negatively charged gold nanorods. Journal of Molecular Structure, 2012, 1020, 56– 62.
R. Wibulswas, Batch and fixed bed sorption of methylene blue on precursor and QACs modified montmorillonite. Separation and Purification Technology, 2004, 39, 3– 12.
S. A. Hussain, S. Chakraborty, D. Bhattacharjee, R. A. Schoonheydt, Fluorescence resonance energy transfer between organic dyes adsorbed onto nano-clay and Langmuir– Blodgett (LB) films. Spectrochimica Acta Part A, 2010, 75, 664– 670.
S. Brunauer, P. H. Emmett, E. Teller, Adsorption of gases in multimolecular layers. J. Am. Chem. Soc., 1938, 60, 309– 319.
S. E. Jayaraj, M. Umadevi, V. Ramakrishnan, Environmental effect on the laser- excited fluorescence spectra of methylene blue and methylene green dyes. Journal of Inclusion Phenomena and Macrocyclic Chemistry, 2001, 40, 203– 206.
S. E. Rizk, M. M. Hamed, Batch sorption of iron complex dye, naphthol green B, from wastewater on charcoal, kaolinite, and tafla. Desalination and Water Treatment, 2015, 56, 1536– 1546.
S. P. Liu, C. Sa, X. L. Hu, L. Kong, Fluorescence quenching method for the determination of sodium carboxymethyl cellulose with acridine yellow or acridine orange. Spectrochimica Acta Part A, 2006, 64, 817– 822.
S. Riela, M. Massaro, C. G. Colletti, A. Bommarito, C. Giordano, S. Milioto, R. Noto, P. Poma, G. Lazzara, Development and characterization of co- loaded curcumin/ triazole- halloysite systems and evaluation of their potential anticancer activity. International Journal of Pharmaceutics, 2014, 475, 613– 623.
S. R. Valandro, A. L. Poli, M. G. Neumann, C. C. Schmitt, Photophysics of auramine O adsorbed on solid clays. Journal of Luminescence, 2015, 161, 209– 213.
S. R. Valandro, A. L. Poli, T. F. A. Correia, P. C. Lombardo, C. C. Schmitt, Photophysical behavior of isocyanine/ clay hybrids in the solid state. Langmuir, 2017, 33, 891– 899.
S. Sas, M. Danko, V. Bizovská, K. Lang, Highly luminescent hybrid materials based on smectites with polyethylene glycol modified with rhodamine fluorophore. Applied Clay Science, 2017, 138, 25– 33.
T. Endo, N. Nakada, T. Sato, M. Shimada, Fluorescence of clay-intercalated xanthene dyes. J. Phys. Chem. Solids, 1988, 49, 1423– 1428
T. Felbeck, S. Mundinger, M. M. Lezhnina, M. Staniford, U. R. Genger, U. H. Kynast, Multifold fluorescence enhancement in nanoscopic fluorophore– clay hybrids in transparent aqueous media. Chem. Eur. J., 2015, 21, 7582– 7587.
T. Feng, L. Xu, Adsorption of Acid red onto chitosan/ rectorite composites from aqueous solution. RSC Adv., 2013, 3, 21685.
T. Shiragami, Y. Mori, J. Matsumoto, S. Takagi, H. Inoue, M. Yasuda, Non-aggregated adsorption of cationic metalloporphyrin dyes onto nano-clay sheets films. Colloids and Surfaces A: Physicochem. Eng. Aspects, 2006, 284–285, 284– 289.
T. Saito, K. Fukui, Y. Kodera, A. Matsushima, H. Nishimura, Y. Inada, Photostability of biliverdin bound to smectite, clay mineral. Dyes and Pigments, 2005, 65, 21– 24.
T. Tsukamoto, T. Shimada, S. Takagi, Unique photochemical properties of ρ‑ substituted cationic triphenylbenzene derivatives on a clay layer surface. J. Phys. Chem. C, 2013, 117, 2774– 2779.
T. Tsukamoto, T. Shimada, S. Takagi, Photophysical properties and adsorption behaviors of novel tri- cationic boron(III) subporphyrin on anionic clay surface. Appl. Mater. Interfaces, 2016, 8, 7522– 7528.
U. Gupta, D. Mohan, S. K. Ghoshal, V. Nasa, Dual fluorescence of methylene blue encapsulated in silica matrix. Journal of Photochemistry and Photobiology A: Chemistry, 2010, 209, 7– 11.
V. Ambrogi, L. Latterini, M. Nocchetti, C. Pagano, M. Ricci, Montmorillonite as an agent for drug photostability. J. Mater. Chem., 2012, 22, 22743.
V. G. Bregadze, Z. G. Melikishvili, T. G. Giorgadze, I. G. Khutsishvili, T. B. Khuskivadze, Z. V. Jaliashvili, K. I. Sigua, Laser- induced fluorescence resonance energy transfer for analysis of the quality of a DNA double helix. Laser Phys. Lett., 2016, 13, 115601.
V. M. Martínez, F. L. Arbeloa, J. B. Prieto, I. L. Arbeloa, Characterization of rhodamine 6G aggregates intercalated in solid thin films of laponite clay. 1 Absorption spectroscopy. J. Phys. Chem. B, 2004, 108, 20030– 20037.
V. M. Martínez, F. L. Arbeloa, J. B. Prieto, I. L. Arbeloa, Characterization of rhodamine 6G aggregates intercalated in solid thin films of laponite clay. 2 Fluorescence spectroscopy. J. Phys. Chem. B, 2005, 109, 7443– 7450.
W. Gao, S. Zhao, H. Wu, W. Deligeer, S. Asuha, Direct acid activation of kaolinite and its effects on the adsorption of methylene blue. Applied Clay Science, 2016, 126, 98– 106.
W. T. Jiang, P. H. Chang, Y. Tsai, Z. Li, Halloysite nanotubes as a carrier for the uptake of selected pharmaceuticals. Microporous and Mesoporous Materials, 2016, 220, 298– 307.
W. Zhu, C. Xuan, G. Liu, Z. Chen, W. Wang, A label- free fluorescent biosensor for determination of bovine serumalbumin and calf thymus DNA based on gold nanorods coated withacridine orange- loaded mesoporous silica. Sensors and Actuators B, 2015, 220, 302– 308.
X. F. Wang, L. P. Xiang, Y. S. Wang, J. H. Xue, Y. F. Zhu, Y. Q. Huang, S. H. Chen, X. Tang, A “turn-on” fluorescence assay for lead(II) based on the suppression of the surface energy transfer between acridine orange and gold nanoparticles. Microchim Acta, 2016, 183, 1333– 1339.
X. L. Xiong, N. Zhao, X. M. Wang, Interaction between tryptophan-Sm(III) complex and DNA with the use of a acridine orange dye fluorophor probe. Luminescence, 2016, 31, 210– 216.
Y. Du, P. Zheng, Adsorption and photodegradation of methylene blue on TiO2- halloysite adsorbents. Korean J. Chem. Eng., 2014, 31, 2051– 2056.
Y. Guo, Y. Liu, Adsorption properties of methylene blue from aqueous solution onto thermal modified rectorite. Journal of Dispersion Science and Technology, 2014, 35, 1351– 1359.
Y. Li, Y. Zhang, S. Sun, A. Zhang, Y. Liu, Binding investigation on the interaction between methylene blue (MB)/TiO2 nanocomposites and bovine serum albumin by resonance light-scattering (RLS) technique and fluorescence spectroscopy. Journal of Photochemistry and Photobiology B: Biology, 2013, 128, 12– 19.
Y. Liu, W. Wang, A. Wang, Removal of congo red from aqueous solution by sorption on organified rectorite. Clean – Soil, Air, Water, 2010, 38, 670– 677.
Y. L. Ma, Z. R. Xu, T. Guo, P. You, Adsorption of methylene blue on Cu（II）- exchanged montmorillonite. Journal of Colloid and Interface Science, 2004, 280, 283– 288.
Y. Ishida, T. Shimada, H. Tachibana, H. Inoue, S. Takagi, Regulation of the collisional self-quenching of fluorescence in clay/porphyrin complex by strong host−guest interaction. J. Phys. Chem. A, 2012, 116, 12065– 12072.
Y. Kohno, R. Kinoshita, S. Ikoma, K. Yoda, M. Shibata, R. Matsushima,Y. Tomita, Y. Maeda, K. Kobayashi, Stabilization of natural anthocyanin by intercalation into montmorillonite. Applied Clay Science, 2009, 42, 519– 523.
Y. Miao, Y. Li, Z. Zhang, G. Yan, Y. Bi, “Turn off– on’’ phosphorescent biosensors for detection of DNA based on quantum dots/ acridine orange. Analytical Biochemistry, 2015, 475, 32– 39.
Y. Xie, D. Qian, D. Wu, X. Ma, Magnetic halloysite nanotubes/ iron oxide composites for the adsorption of dyes. Chemical Engineering Journal, 2011, 168, 959– 963.
Y. Zhang, J. Pan, G. Zhang, X. Zhou, Intercalation of herbicide propyzamide into DNA using acridine orange as a fluorescence probe. Sensors and Actuators B, 2015, 206, 630– 639.
Z. Gaoke, L. Guanfeng, G. Yadan, Adsorption of methylene blue from aqueous solution onto hydrochloric acid- modifi ed rectorite. Journal of Wuhan University of Technology- Mater. Sci. Ed., 2011, 817– 822.
Z. Klika, H. Weissmannová, P. Capková, M. Pospíšil, The rhodamine B intercalation of montmorillonite. Journal of Colloid and Interface Science, 2004, 275, 243– 250.
Z. Klika, P. Capková, P. Horáková, M. Valášková, P. Malý, R. Machán, M. Pospíšil, Composition, structure, and luminescence of montmorillonites saturated with different aggregates of methylene blue. Journal of Colloid and Interface Science, 2007, 311, 14– 23.
Z. Klika, P. Pustková, P. Praus, P. Kovár, M. Pospíšil, P. Malý, T. Grygar, L. Kulhánková, P.Capková, Fluorescence of reduced charge montmorillonite complexes with methylene blue: Experiments and molecular modeling. Journal of Colloid and Interface Science, 2009, 339, 416– 423.
Z. Li, C. J. Wang, W. T. Jiang, Intercalation of methylene blue in a high- charge calcium montmorillonite– An indication of surface charge determination. Adsorption Science & Technology, 2010, 28, 297– 312.
Z. Li, P. H. Chang, W. T. Jiang, J. S. Jean, H. Hong, Mechanism of methylene blue removal from water by swelling clays. Chemical Engineering Journal, 2011, 168, 1193– 1200.