The authors want to thank the Secretar&#237;a de Ciencia, Tecnolog&#237;a e Innovaci&#243;n de la Ciudad de M&#233;xico for the resources provided to carry out this work through the funded project SECITI/047/2016, and the National Funds for Scientific and Technological Development Chile (FONDECYT 11170431).

NOTE: Please read all the material safety data sheets (MSDS) before using the chemical reagents. Follow all the safety protocols by wearing a lab coat and gloves. Wear UV protection safety glasses during the photocatalysis tests. Be aware that nanomaterials may present important hazardous effects compared to their precursors.
1. Preparation of the BiOI microspheres
<ol>
	<li>For Solution 1, dissolve 2.9104 g of bismuth nitrate pentahydrate (Bi(NO3)3&#8729;5H2O) in 60 mL of ethylene glycol in a glass beaker. For Solution 2, dissolve 0.9960 g of KI in 60 mL of ethylene glycol in a glass beaker. 
	NOTE: It is important to completely dissolve the inorganic salts in organic solvent; it may take around 60 min. Sonication may be helpful to dissolve both precursors.</li>
	<li>Dropwise, add Solution 2 to Solution 1 (at a flow rate of approximately 1 mL/min). The colorless Solution 2 will change to a yellowish suspension. Sometimes, when Solution 2 is abruptly added, a black color may appear, due to the formation of the BiI4- complex. In such cases, the synthesis must be aborted and started again. 
	NOTE: Laboratory material must be completely dried since the occurrence of water promotes the uncontrolled precipitation of bismuth oxide (Bi2O3).</li>
	<li>Stir the mixture, using a moderate speed for 30 min at room temperature. Then, transfer the mixture to a 150 mL autoclave reactor. Carefully swirl the beaker to remove the remaining suspension from the sidewalls. It is possible to add 1 to 5 mL of ethylene glycol to rinse the beakers. Make sure to tightly close the reactor. 
	NOTE: The autoclave should be filled from 40% to 80% of its capacity in order to achieve the optimal pressure conditions to the formation of the BiOI microspheres. A soft seal of the reactor may result in the loss of pressure, spoiling the synthesis.</li>
	<li>Supply thermal treatment to the reactor in a furnace, from room temperature to 126 &#176;C, using a temperature ramp of 2 &#176;C/min. Maintain the final temperature for 18 h10. Then, cool the autoclave reactor to room temperature. 
	NOTE: Do not preheat the oven or provide a rapid heating since it will spoil the formation of the microspheres. 
	CAUTION: Do not induce cooling by washing the autoclave with cold water, as it may cause the deformation of the autoclave. Do not attempt to open the reactor while it is still hot, as this may result in the release of iodine gas.</li>
</ol>
2. Washing the BiOI microspheres
<ol>
	<li>Separate the solid material by decantation and wash it to remove ethylene glycol as much as possible. Prepare a filtration system consisting of a 0.8 &#956;m filter paper (Grade 5, free of ashes) properly adhered to the walls of a glass funnel. Connect&#160;to an Erlenmeyer flask using a pierced cork stopper. Carry out the filtration step by gravity.
	<ol>
		<li>(Optional) When pouring the suspension from the reactor to the funnel, use deionized water to rinse the autoclave reactor.</li>
	</ol>
	</li>
	<li>Wash the solid product retained in the filter paper&#8212;of an intense orange color&#8212;several times with distilled water and absolute ethanol (technical grade). Alternate the washing solvent until the leachate is colorless. 
	NOTE: Please note that deionized water removes inorganic ions, while absolute ethanol removes the remaining ethylene glycol; thus, both solvents must be used.</li>
	<li>Use deionized water in the two last washing steps to remove any trace of absolute ethanol and dry the intense-orange-colored product at 80 &#176;C for 24 h. Last, store the material in amber glass bottles, in the dark, preferably in a desiccator.</li>
</ol>
3. Characterization of the BiOI microspheres
<ol>
	<li>Perform the X-ray diffraction analysis of the powder material, using a monochromic Cu-K&#945; light source, with &#955; = 1.5406 &#197;, operated at 30 kV and 15 mA.</li>
	<li>Determine the specific surface area by the Brunauer&#8211;Emmett&#8211;Teller (BET) method, via the adsorption of N2.
	<ol>
		<li>Outgas the powder samples (500 mg) at 80&#186;C overnight prior to analysis. Perform the N2 adsorption measurements at -75&#186;C. Calculate the specific surface area and the pore volume from the adsorption isotherms.</li>
	</ol>
	</li>
	<li>Determine the UV-visible diffuse reflectance spectra of the materials using a spectrophotometer with a praying mantis accessory.
	<ol>
		<li>Dry the powder samples, in a laboratory oven, at 105&#186;C overnight. Then, carefully put 30 mg in the sample port of the praying mantis accessory.</li>
		<li>Irradiate the powder samples with a light source within the range of 200 to 800 nm in order to obtain the light absorption spectrum of the material. Calculate the band gap energy (Eg) using the absorption spectrum of the sample.</li>
	</ol>
	</li>
	<li>Determine the secondary size of the BiOI microspheres by scanning electron microscopy.
	<ol>
		<li>Put the powder sample on a carbon tape and then in the microscope stub to perform the observations.</li>
		<li>Determine the chemical composition of the samples by energy dispersive X-ray spectroscopy (EDS) analysis.</li>
	</ol>
	</li>
</ol>
4. Photocatalytic activity test
<ol>
	<li>For the test solution, dissolve 7.5 mg of ciprofloxacin in 250 mL of distilled water, to obtain a 30 ppm solution. Then, transfer the test solution to the glass photocatalytic reactor. Thoroughly stir the solution, with a magnetic stirrer, keeping the temperature at 25 &#176;C. Bubble air to the solution at 100 mL/min in order to maintain air saturation.</li>
	<li>Add 62.5 mg of the BiOI photocatalyst to the test solution to achieve a concentration of 0.25 g/L. Immediately, take the first sample (8 mL) using a glass syringe. After 30 min of stirring in the dark, take the second sample and turn the light source on.
	<ol>
		<li>Given that the experiments are performed under UV-A/visible light conditions, use a 70 W lamp in the photocatalysis tests. Locate the light source 5 cm above the photoreactor.</li>
	</ol>
	</li>
	<li>Take liquid samples (8 mL) after 5, 10, 15, 20, 30, 45, 60, 90, 120, 180, 240, and 300 min of irradiation. Filter all the withdrawn samples by passing them through a 0.22 &#181;m nylon membrane, in order to remove any solid particle from the liquid prior to analysis. Store the filtered samples in amber glass vials at 4 &#176;C until analysis.</li>
	<li>Determine the mineralization of ciprofloxacin by analyzing the total organic carbon (TOC) concentration remaining in the liquid samples throughout the photocatalytic process.
	<ol>
		<li>Measure the concentration of total carbon (TC, in mg/L) via wet combustion at 720 &#176;C, in the presence of a Pt catalyst and air atmosphere. Under such conditions, all the carbon is oxidized to CO2 and quantified in an FTIR detector coupled to the TOC device.</li>
		<li>Determine the inorganic carbon concentration (IC, in mg/L) via acidification of&#160;samples with 1 M HCl, leading to the conversion of carbonate and bicarbonate to CO2&#183;H2O, which is quantified in the FTIR detector.</li>
		<li>Calculate the concentration of TOC remaining in water samples by the following equation. 
		<img alt="Equation" src="/files/ftp_upload/59006/59006eq1.jpg" /> 
		&#8203;NOTE: In order to avoid interferences and, thus, incorrect results, it is very important to remove any trace of organic impurities by thoroughly cleaning all the glass material used in the sample preparation. This may be warranted by washing several times with hot water.</li>
		<li>Calculate the mineralization yield via the depletion of total organic carbon throughout the reaction using the equation: 
		<img alt="Equation" src="/files/ftp_upload/59006/59006eq2v2.jpg" /> 
		Here, TOCo is the concentration of total organic carbon at the beginning of the irradiation, while TOC is the concentration of total organic carbon at any time of the photocatalytic reaction.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Yu, C., Zhou, W., Liu, H., Liu, Y., Dionysiou, D. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Design+and+fabrication+of+microsphere+photocatalysts+for+environmental+purification+and+energy+conversion.">Design and fabrication of microsphere photocatalysts for environmental purification and energy conversion.</a> Chemical Engineering Journal. 287, 117-129 (2016).</li><li>Wang, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Semiconductor+heterojunction+photocatalysts:+Design,+construction,+and+photocatalytic+performances.">Semiconductor heterojunction photocatalysts: Design, construction, and photocatalytic performances.</a> Chemical Society Reviews. 43 (15), 5234-5244 (2014).</li><li>Chou, S. Y., Chen, C. C., Dai, Y. M., Lin, J. H., Lee, W. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+synthesis+of+bismuth+oxyiodide/graphitic+carbon+nitride+nanocomposites+with+enhanced+visible-light+photocatalytic+activity.">Novel synthesis of bismuth oxyiodide/graphitic carbon nitride nanocomposites with enhanced visible-light photocatalytic activity.</a> RSC Advances. 6, 33478-33491 (2016).</li><li>Siao, C. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controlled+hydrothermal+synthesis+of+bismuth+oxychloride/bismuth+oxybromide/bismuth+oxyiodide+composites+exhibiting+visible-light+photocatalytic+degradation+of+2-hydroxybenzoic+acid+and+crystal+violet.">Controlled hydrothermal synthesis of bismuth oxychloride/bismuth oxybromide/bismuth oxyiodide composites exhibiting visible-light photocatalytic degradation of 2-hydroxybenzoic acid and crystal violet.</a> Journal of Colloid and Interface Science. 526, 322-336 (2018).</li><li>Meng, X., Zhang, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bismuth-based+photocatalytic+semiconductors:+Introduction,+challenges+and+possible+approaches.">Bismuth-based photocatalytic semiconductors: Introduction, challenges and possible approaches.</a> Journal of Molecular Catalysis A: Chemical. 423, 533-549 (2016).</li><li>Wang, Y., Deng, K., Zhang, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visible+light+photocatalysis+of+BiOI+and+its+photocatalytic+activity+enhancement+by+in+situ+ionic+liquid+modification.">Visible light photocatalysis of BiOI and its photocatalytic activity enhancement by in situ ionic liquid modification.</a> Journal of Physical Chemistry C. 115 (29), 14300-14308 (2011).</li><li>Xiao, X., Zhang, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=De+Facile+synthesis+of+nanostructured+BiOI+microspheres+with+high+visible+light-induced+photocatalytic+activity.">De Facile synthesis of nanostructured BiOI microspheres with high visible light-induced photocatalytic activity.</a> Journal of Materials Chemistry. 20 (28), 5866-5870 (2010).</li><li>Chen, C. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bismuth+oxyfluoride/bismuth+oxyiodide+nanocomposites+enhance+visible-light-driven+photocatalytic+activity.">Bismuth oxyfluoride/bismuth oxyiodide nanocomposites enhance visible-light-driven photocatalytic activity.</a> Journal of Colloid and Interface Science. 532, 375-386 (2018).</li><li>Xia, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Self-assembly+and+enhanced+photocatalytic+properties+of+BiOI+hollow+microspheres+via+a+reactable+ionic+liquid.">Self-assembly and enhanced photocatalytic properties of BiOI hollow microspheres via a reactable ionic liquid.</a> Langmuir. 27 (3), 1200-1206 (2011).</li><li>Mera, A. C., Contreras, D., Escalona, N., Mansilla, H. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=BiOI+microspheres+for+photocatalytic+degradation+of+gallic+acid.">BiOI microspheres for photocatalytic degradation of gallic acid.</a> Journal of Photochemistry and Photobiology A: Chemistry. 318, 71-76 (2016).</li><li>Pan, M., Zhang, H., Gao, G., Liu, L., Chen, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Facet-dependent+catalytic+activity+of+nanosheet-assembled+bismuth+oxyiodide+microspheres+in+degradation+of+bisphenol+A.">Facet-dependent catalytic activity of nanosheet-assembled bismuth oxyiodide microspheres in degradation of bisphenol A.</a> Environmental Science and Technology. 49 (10), 6240-6248 (2015).</li><li>Hu, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Solvents+mediated-synthesis+of+BiOI+photocatalysts+with+tunable+morphologies+and+their+visible-light+driven+photocatalytic+performances+in+removing+of+arsenic+from+water.">Solvents mediated-synthesis of BiOI photocatalysts with tunable morphologies and their visible-light driven photocatalytic performances in removing of arsenic from water.</a> Journal of Hazardous Materials. 264, 293-302 (2014).</li><li>Ye, L., Su, Y., Jin, X., Xie, H., Zhang, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+advances+in+BiOX+(X+=+Cl,+Br+and+I)+photocatalysts:+Synthesis,+modification,+facet+effects+and+mechanisms.">Recent advances in BiOX (X = Cl, Br and I) photocatalysts: Synthesis, modification, facet effects and mechanisms.</a> Environmental Science: Nano. 1 (2), 90-112 (2014).</li><li>Qin, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three+dimensional+BiOX+(X=Cl,+Br+and+I)+hierarchical+architectures:+Facile+ionic+liquid-assisted+solvothermal+synthesis+and+photocatalysis+towards+organic+dye+degradation.">Three dimensional BiOX (X=Cl, Br and I) hierarchical architectures: Facile ionic liquid-assisted solvothermal synthesis and photocatalysis towards organic dye degradation.</a> Materials Letters. 100, 285-288 (2013).</li><li>Chou, S. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+series+of+BiO+x+I+y/GO+photocatalysts:+synthesis,+characterization,+activity,+and+mechanism.">A series of BiO x I y/GO photocatalysts: synthesis, characterization, activity, and mechanism.</a> RSC Advances. 6 (86), 82743-82758 (2016).</li><li>Shi, X., Chen, X., Chen, X., Zhou, S., Lou, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Solvothermal+synthesis+of+BiOI+hierarchical+spheres+with+homogeneous+sizes+and+their+high+photocatalytic+performance.">Solvothermal synthesis of BiOI hierarchical spheres with homogeneous sizes and their high photocatalytic performance.</a> Materials Letters. 68, 296-299 (2012).</li><li>Di, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reactable+ionic+liquid-assisted+rapid+synthesis+of+BiOI+hollow+microspheres+at+room+temperature+with+enhanced+photocatalytic+activity.">Reactable ionic liquid-assisted rapid synthesis of BiOI hollow microspheres at room temperature with enhanced photocatalytic activity.</a> Journal of Materials Chemistry A. 2 (38), 15864-15874 (2014).</li><li>Ren, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controllable+synthesis+of+hollow/flower-like+BiOI+microspheres+and+highly+efficient+adsorption+and+photocatalytic+activity.">Controllable synthesis of hollow/flower-like BiOI microspheres and highly efficient adsorption and photocatalytic activity.</a> CrystEngComm. 14 (13), 4384-4390 (2012).</li><li>Lei, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Room+temperature,+template-free+synthesis+of+BiOI+hierarchical+structures:+Visible-light+photocatalytic+and+electrochemical+hydrogen+storage+properties.">Room temperature, template-free synthesis of BiOI hierarchical structures: Visible-light photocatalytic and electrochemical hydrogen storage properties.</a> Dalton Transactions. 39 (13), 3273-3278 (2010).</li><li>Montoya-Zamora, J. M., Mart&#237;nez-de la Cruz, A., L&#243;pez Cu&#233;llar, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhanced+photocatalytic+activity+of+BiOI+synthesized+in+presence+of+EDTA.">Enhanced photocatalytic activity of BiOI synthesized in presence of EDTA.</a> Journal of the Taiwan Institute of Chemical Engineers. 75, 307-316 (2017).</li><li>He, R., Zhang, J., Yu, J., Cao, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Room-temperature+synthesis+of+BiOI+with+tailorable+(0+0+1)+facets+and+enhanced+photocatalytic+activity.">Room-temperature synthesis of BiOI with tailorable (0 0 1) facets and enhanced photocatalytic activity.</a> Journal of Colloid and Interface Science. 478, 201-208 (2016).</li><li>Song, J. M., Mao, C. J., Niu, H. L., Shen, Y. H., Zhang, S. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hierarchical+structured+bismuth+oxychlorides:+self-assembly+from+nanoplates+to+nanoflowers+via+a+solvothermal+route+and+their+photocatalytic+properties.">Hierarchical structured bismuth oxychlorides: self-assembly from nanoplates to nanoflowers via a solvothermal route and their photocatalytic properties.</a> CrystEngComm. 12, 3875-3881 (2010).</li><li>Mera, A. C., V&#225;ldes, H., Jamett, F. J., Mel&#233;ndrez, M. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=BiOBr+microspheres+for+photocatalytic+degradation+of+an+anionic+dye.">BiOBr microspheres for photocatalytic degradation of an anionic dye.</a> Solid State Science. 65, 15-21 (2017).</li><li>Kong, X. Y., Lee, W. C., Ong, W. J., Chai, S. P., Mohamed, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oxygen-deficient+BiOBr+as+a+highly+stable+photocatalyst+for+efficient+CO2+reduction+into+renewable+carbon-neutral+fuels.">Oxygen-deficient BiOBr as a highly stable photocatalyst for efficient CO2 reduction into renewable carbon-neutral fuels.</a> ChemCatChem. 8, 3074-3081 (2016).</li></ol>

The authors have nothing to disclose.

We consider the mixture of the precursors as the critical step in the solvothermal synthesis of the BiOI microspheres. A very slow dripping of the KI solution into the Bi(NO3)3 solution (at a maximum of 1 mL/min) is crucial to obtain mesoporous microspheres, since it allows the slow formation and self-assembly of the [Bi2O2]+2 slabs, followed by the bonding with the iodide atoms to form the BiOI laminates. The lamellae are the bricks of the microspheres in the solvot...

A plethora of semiconductors has been synthesized so far, aiming for photocatalysts with high activity under visible light irradiation, either to degrade organic compounds or to generate renewable energy in the form of hydrogen1,2. Bismuth oxyhalides BiOX (X = Cl, Br, or I) are candidates for such applications because of their high photocatalytic efficiency under visible light or simulated sunlight irradiation3,4. The band gap energy (Eg) of bismuth oxyhalides decreases with the increase of the atomic number of the halide; thus, BiOI is the material displaying the lowest activation energy (Eg = 1.8 eV)5. Iodide atoms, bonded via Van der Waals force to bismuth atoms, create an electric field that favors the migration of the charge carriers to the semiconductor surface, triggering the photocatalytic process4,6. Moreover, the architecture of the crystallite has a critical role in the separa,tion of the charge carriers. Highly oriented structures in the (001) plane and 3D structures (such as microspheres) facilitate the charge carrier separation upon irradiation, increasing the photocatalytic performance7,8,9,10,11,12. In light of this, it is necessary to develop reliable synthetic methods to obtain structures that boost the photo-activity of the bismuth oxyhalide materials.
The solvothermal method is, by far, the most commonly used and studied route to obtain BiOI microspheres13,14,15,16. Some methodologies using ionic liquids have been also reported17, although the expenses associated with these methodologies can be higher. Microsphere structure is usually obtained using organic solvents such as ethylene glycol, which acts as a coordinating agent to form metallic alkoxides, resulting in a gradual self-assembling of [Bi2O2]2+ species18,19. Using the solvothermal route with ethylene glycol facilitates the formation of different morphologies by changing the key parameters in the reaction, such as temperature and reaction time4,18. There is a wide body of literature on synthetic methods to obtain BiOI microspheres, which shows contrasting information to achieve highly photoactive structures. This detailed protocol is aimed at showing a reliable synthetic method to obtain BiOI microspheres highly functional in the photocatalytic degradation of pollutants in water. We intend to help new researchers to successfully obtain this kind of materials, avoiding the most common pitfalls associated with the synthesis process.

<table><tbody><tr><td>Bismuth(III) nitrate pentahydrate</td><td>Sigma Aldrich</td><td>383074</td><td>ACS reagent, &amp;ge;98.0%</td></tr><tr><td>Potassium iodide</td><td>Sigma Aldrich</td><td>746428</td><td>ACS reagent, &amp;ge;98.0%</td></tr><tr><td>Ethylene glycol</td><td>Sigma Aldrich</td><td>324558</td><td>Anhydrous, 99.8%</td></tr><tr><td>Ethanol</td><td>Meyer</td><td>5405</td><td>Technical Grade, 96%</td></tr><tr><td>Ciprofloxacin</td><td>Sigma Aldrich</td><td>17850</td><td>HPLC, &amp;ge;98.0%</td></tr><tr><td>Cary 5000 UV-Vis-NIR spectrophotometer</td><td>Agilent</td><td></td><td>Used for the Band gap determination by the Tauc model.</td></tr><tr><td>JSM-5600 Scanning Electron Microscope</td><td>JOEL</td><td></td><td>Used for the SEM images.</td></tr><tr><td>Autosob-1</td><td>Qantachrome Instruments</td><td></td><td>Used for the determination of surface area and pore diameter.</td></tr><tr><td>TOC-L Total Organic Carbon Analyzer</td><td>Shimadzu</td><td></td><td>Used for determination of total organic carbon in water samples.</td></tr><tr><td>Bruker AXS D8 Advance - X-ray Diffraction</td><td>Bruker</td><td></td><td>Determination of crystal structure and crystallite size</td></tr></tbody></table>

a facile synthetic method to obtain bismuth oxyiodide microspheres highly functional for the photocatalytic processes of water depuration

Bismuth oxyhalide (BiOI) is a promising material for sunlight-driven-environmental photocatalysis. Given that the physical structure of this kind of materials is highly related to its photocatalytic performance, it is necessary to standardize the synthetic methods in order to obtain the most functional architectures and, thus, the highest photocatalytic efficiency. Here, we report a reliable route to obtain BiOI microspheres via the solvothermal process, using Bi(NO3)3 and potassium iodide (KI) as precursors, and ethylene glycol as a template. The synthesis is standardized in a 150 mL autoclave, at 126 &#176;C for 18 h. This results in 2-3 &#181;m-sized mesoporous microspheres, with a relevant specific surface area (61.3 m2/g). Shortening the reaction times in the synthesis results in amorphous structures, while higher temperatures lead to a slight increase in the porosity of the microspheres, with no effect in the photocatalytic performance. The materials are photo-active under UV-A/visible light irradiation for the degradation of the antibiotic ciprofloxacin in water. This method has demonstrated to be effective in interlaboratory tests, obtaining similar BiOI microspheres in Mexican and Chilean research groups.

3D microstructures of BiOI were successfully synthesized by the proposed synthetic method. This was confirmed by the SEM images shown in Figure 1a-c. The microspheres are formed from laminar structures of [Bi2O2]2+, which are bonded by two iodide atoms1. The formation of the microspheres depends on the temperature and time of the solvothermal procedure, as these paramet...

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A Facile Synthetic Method to Obtain Bismuth Oxyiodide Microspheres Highly Functional for the Photocatalytic Processes of Water Depuration

This article describes a synthetic method to obtain bismuth oxyiodide microspheres, which are highly functional to perform the photocatalytic removal of organic pollutants, such as ciprofloxacin, in water under UV-A/visible light irradiation.

Bismuth oxyhalide (BiOI) is a promising material for sunlight-driven-environmental photocatalysis. Given that the physical structure of this kind of ...

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7.6K Views.  Universidad Nacional Autónoma de México. This article describes a synthetic method to obtain bismuth oxyiodide microspheres, which are highly functional to perform the photocatalytic removal of organic pollutants, such as ciprofloxacin, in water under UV-A/visible light irradiation.

Video: A Facile Synthetic Method to Obtain Bismuth Oxyiodide Microspheres Highly Functional for the Photocatalytic Processes of Water Depuration

Photochemical Oxidative Growth of Iridium Oxide Nanoparticles on CdSe@CdS Nanorods

We demonstrate a procedure for the photochemical oxidative growth of iridium oxide catalysts on the surface of seeded cadmium selenide-cadmium sulfide (CdSe@CdS) nanorod photocatalysts. Seeded rods are grown using a colloidal hot-injection method and then moved to an aqueous medium by ligand exchange. CdSe@CdS nanorods, an iridium precursor and other salts are mixed and illuminated. The deposition process is initiated by absorption of photons by the semiconductor particle, which results with formation of charge carriers that are used to promote redox reactions. To insure photochemical oxidative growth we used an electron scavenger. The photogenerated holes oxidize the iridium precursor, apparently in a mediated oxidative pathway. This results in the growth of high quality crystalline iridium oxide particles, ranging from 0.5 nm to about 3 nm, along the surface of the rod. Iridium oxide grown on CdSe@CdS heterostructures was studied by a variety of characterization methods, in order to evaluate its characteristics and quality. We explored means for control over particle size, crystallinity, deposition location on the CdS rod, and composition. Illumination time and excitation wavelength were found to be key parameters for such control. The influence of different growth conditions and the characterization of these heterostructures are described alongside a detailed description of their synthesis. Of significance is the fact that the addition of iridium oxide afforded the rods astounding photochemical stability under prolonged illumination in pure water (alleviating the requirement for hole scavengers).

A protocol for the photochemical oxidative growth of small crystalline iridium oxide nanoparticles on the surface of CdSe@CdS seeded rod nanoparticles is presented.

We demonstrate a procedure for the photochemical oxidative growth of iridium oxide catalysts on the surface of seeded cadmium selenide-cadmium sulfide ...

Synthesis of Cd-free InP/ZnS Quantum Dots Suitable for Biomedical Applications

Fluorescent nanocrystals, specifically quantum dots, have been a useful tool for many biomedical applications. For successful use in biological systems, quantum dots should be highly fluorescent and small/monodisperse in size. While commonly used cadmium-based quantum dots possess these qualities, they are potentially toxic due to the possible release of Cd2+ ions through nanoparticle degradation. Indium-based quantum dots, specifically InP/ZnS, have recently been explored as a viable alternative to cadmium-based quantum dots due to their relatively similar fluorescence characteristics and size. The synthesis presented here uses standard hot-injection techniques for effective nanoparticle growth; however, nanoparticle properties such as size, emission wavelength, and emission intensity can drastically change due to small changes in the reaction conditions. Therefore, reaction conditions such temperature, reaction duration, and precursor concentration should be maintained precisely to yield reproducible products. Because quantum dots are not inherently soluble in aqueous solutions, they must also undergo surface modification to impart solubility in water. In this protocol, an amphiphilic polymer is used to interact with both hydrophobic ligands on the quantum dot surface and bulk solvent water molecules. Here, a detailed protocol is provided for the synthesis of highly fluorescent InP/ZnS quantum dots that are suitable for use in biomedical applications.

In this protocol, the synthesis of Cd-free InP/ZnS quantum dots (QDs) is detailed. InP-based QDs are gaining popularity due to the toxicity of Cd2+ ions that may be released through nanoparticle degradation. After synthesis, QDs are solubilized in water using an amphiphilic polymer for use in biomedical applications.

Fluorescent nanocrystals, specifically quantum dots, have been a useful tool for many biomedical applications. For successful use in biological systems, ...

Facile Synthesis of Worm-like Micelles by Visible Light Mediated Dispersion Polymerization Using Photoredox Catalyst

Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins with the synthesis of a hydrophilic poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) homopolymer using reversible addition-fragmentation chain-transfer (RAFT) polymerization. Under mild visible light irradiation (&#955; = 460 nm, 0.7 mW/cm2), this macro-chain transfer agent (macro-CTA) in the presence of a ruthenium based photoredox catalyst, Ru(bpy)3Cl2 can be chain extended with a second monomer to form a well-defined block copolymer in a process known as Photoinduced Electron Transfer RAFT (PET-RAFT). When PET-RAFT is used to chain extend POEGMA with benzyl methacrylate (BzMA) in ethanol (EtOH), polymeric nanoparticles with different morphologies are formed in situ according to a polymerization-induced self-assembly (PISA) mechanism. Self-assembly into nanoparticles presenting POEGMA chains at the corona and poly(benzyl methacrylate) (PBzMA) chains in the core occurs in situ due to the growing insolubility of the PBzMA block in ethanol. Interestingly, the formation of highly pure worm-like micelles can be readily monitored by observing the onset of a highly viscous gel in situ due to nanoparticle entanglements occurring during the polymerization. This process thereby allows for a more reproducible synthesis of worm-like micelles simply by monitoring the solution viscosity during the course of the polymerization. In addition, the light stimulus can be intermittently applied in an ON/OFF manner demonstrating temporal control over the nanoparticle morphology.

This article describes a process for producing polymeric self-assembled nanoparticles using visible light mediated dispersion polymerization. Using low energy visible light to control the polymerization allows for the reproducible formation of self-assembled worm-like micelles at high solids content.

Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins ...

TiO2-coated Hollow Glass Microspheres with Superhydrophobic and High IR-reflective Properties Synthesized by a Soft-chemistry Method

This manuscript proposes a soft-chemistry method to develop superhydrophobic and highly IR-reflective hollow glass microspheres (HGM). The anatase TiO2 and a superhydrophobic agent were coated on the HGM surface in one step. TBT and PFOTES were selected as the Ti source and the superhydrophobic agent, respectively. They were both coated on the HGM, and after the hydrothermal process, the TBT turned to anatase TiO2. In this way, a PFOTES/TiO2-coated HGM (MCHGM) was prepared. For comparison, PFOTES single-coated HGM (F-SCHGM) and TiO2 single-coated HGM (Ti-SCHGM) were synthesized as well. The PFOTES and TiO2 coatings on the HGM surface were demonstrated through X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive detector (EDS) characterizations. The MCHGM showed a higher contact angle (153&#176;) but a lower sliding angle (16&#176;) than F-SCHGM, with a contact angle of 141.2&#176; and a sliding angle of 67&#176;. In addition, both Ti-SCHGM and MCHGM displayed similar IR reflectivity values, which were about 5.8% higher than the original HGM and F-SCHGM. Also, the PFOTES coating barely changed the thermal conductivity. Therefore, F-SCHGM, with a thermal conductivity of 0.0479 W/(m&#183;K), was quite like the original HGM, which was 0.0475 W/(m&#183;K). MCHGM and Ti-SCHGM were also similar. Their thermal conductivity values were 0.0543 W/(m&#183;K) and 0.0543 W/(m&#183;K), respectively. The TiO2 coating slightly increased the thermal conductivity, but with the increase in reflectivity, the overall heat-insulation property was enhanced. Finally, since the IR-reflecting property is provided by the HGM coating, if the coating is fouled, the reflectivity decreases. Therefore, with the superhydrophobic coating, the surface is protected from fouling, and its lifetime is also prolonged.

TiO2-coated Hollow Glass Microspheres with Superhydrophobic and High IR-reflective Properties Synthesized by a Soft-chemistry Method

This manuscript proposes a soft-chemistry method to synthesize superhydrophobic, TiO2-coated hollow glass microspheres (HGM) with high IR-reflective properties.

This manuscript proposes a soft-chemistry method to develop superhydrophobic and highly IR-reflective hollow glass microspheres (HGM). The anatase TiO2 ...

Fabrication of Polymer Microspheres for Optical Resonator and Laser Applications

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, interface precipitation, and mini-emulsion. In all methods, well-defined, micrometer-sized spheres are obtained from a self-assembling process in solution. The vapor diffusion method can result in spheres with the highest sphericity and surface smoothness, yet the types of the polymers able to form these spheres are limited. On the other hand, in the mini-emulsion method, microspheres can be made from various types of polymers, even from highly crystalline polymers with coplanar, &#960;-conjugated backbones. The photoluminescent (PL) properties from single isolated microspheres are unusual: the PL is confined inside the spheres, propagates at the circumference of the spheres via the total internal reflection at the polymer/air interface, and self-interferes to show sharp and periodic resonant PL lines. These resonating modes are so-called "whispering gallery modes" (WGMs). This work demonstrates how to measure WGM PL from single isolated spheres using the micro-photoluminescence (&#181;-PL) technique. In this technique, a focused laser beam irradiates a single microsphere, and the luminescence is detected by a spectrometer. A micromanipulation technique is then used to connect the microspheres one by one and to demonstrate the intersphere PL propagation and color conversion from coupled microspheres upon excitation at the perimeter of one sphere and detection of PL from the other microsphere. These techniques, &#181;-PL and micromanipulation, are useful for experiments on micro-optic application using polymer materials.

Protocols for the synthesis of microspheres from polymers, the manipulation of microspheres, and micro-photoluminescence measurements are presented.

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, ...

Engineering

Synthesizing Sodium Tungstate and Sodium Molybdate Microcapsules via Bacterial Mineral Excretion

We present a method, the bacterial mineral excretion (BME), for synthesizing two kinds of microcapsules, sodium tungstate and sodium molybdate, and the two metal oxides&#39; corresponding nanoparticles&#8212;the former being as small as 22 nm and the latter 15 nm. We fed two strains of bacteria, Shewanella algae and Pandoraea sp., with various concentrations of tungstate or molybdate ions. The concentrations of tungstate and molybdate were adjusted to make microcapsules of different length-to-diameter ratios. We found that the higher the concentration the smaller the nanoparticles were. The nanoparticles came in with three length-to-diameter ratios: 10:1, 3:1 and 1:1, which were achieved by feeding the bacteria respectively with a low concentration, a medium concentration, and a high concentration. The images of the hollow microcapsules were taken via the scanning electron microsphere (SEM). Their crystal structures were verified by X-ray diffraction (XRD)&#8212;the crystal structure of molybdate microcapsules is Na2MoO4 and that of tungstate microcapsules is Na2WO4 with Na2W2O7. These syntheses all were accomplished under a near ambient condition.

This work presents a protocol for manufacture sodium tungstate and sodium molybdate microcapsules via bacteria and their corresponding nanoparticles.

We present a method, the bacterial mineral excretion (BME), for synthesizing two kinds of microcapsules, sodium tungstate and sodium molybdate, and the ...

A Complete Method for Evaluating the Performance of Photocatalysts for the Degradation of Antibiotics in Environmental Remediation

Various antibiotics such as tetracycline, aureomycin, amoxicillin, and levofloxacin are found in large quantities in groundwater and soil systems, potentially leading to the development of resistant and multi-drug resistant bacteria, posing a threat to humans, animals, and environmental systems. Photocatalytic technology has attracted keen interest due to its rapid and stable treatment and direct use of solar energy. However, most studies evaluating the performance of semiconductor catalysts for the photocatalytic degradation of organic pollutants in water are currently incomplete. In this paper, a complete experimental protocol is designed to comprehensively evaluate the photocatalytic performance of semiconductor catalysts. Herein, rhombic dodecahedral silver phosphate was prepared by a simple solvent phase synthesis method at room temperature and atmospheric pressure. BrSubphthalocyanine/Ag3PO4 heterojunction materials were prepared by the solvothermal method. The catalytic performance of as-prepared materials for the degradation of tetracycline was evaluated by studying different influencing factors such as catalyst dosage, temperature, pH, and anions at atmospheric pressure using a 300 W xenon lamp as a simulated solar light source and a light intensity of 350 mW/cm2. Compared with the first cycle, the constructed BrSubphthalocyanine/Ag3PO4 maintained 82.0% of the original photocatalytic activity after five photocatalytic cycles, while the pristine Ag3PO4 maintained only 28.6%. The stability of silver phosphate samples was further tested by a five-cycle experiment. This paper provides a complete process for evaluating the catalytic performance of semiconductor catalysts in the laboratory for the development of semiconductor catalysts with potential for practical applications.

Presented here is a protocol to explore a universal set of experimental procedures for comprehensive laboratory evaluation of photocatalysts in the field of environmental purification, using the example of photocatalytic removal of antibiotic organic pollutant molecules from water by phthalocyanine sensitized silver phosphate composites.

Various antibiotics such as tetracycline, aureomycin, amoxicillin, and levofloxacin are found in large quantities in groundwater and soil systems, ...

Environment

A Continuous-flow Photocatalytic Reactor for the Precisely Controlled Deposition of Metallic Nanoparticles

In this work, a novel photocatalytic reactor for the pulsed and controlled excitation of the photocatalyst and the precise deposition of metallic nanoparticles is developed. Guidelines for the replication of the reactor and its operation are provided in detail. Three different composite systems (Pt/graphene, Pt/TiO2, and Au/TiO2) with monodisperse and uniformly distributed particles are produced by this reactor, and the photodeposition mechanism, as well as the synthesis optimization strategy, are discussed. The synthesis methods and their technical aspects are described comprehensively. The role of the ultraviolet (UV) dose (in each excitation pulse) on the photodeposition process is investigated and the optimum values for each composite system are provided.

For a continuous and scalable synthesis of noble-metal-based nanocomposites, a novel photocatalytic reactor is developed and its structure, operation principles, and product quality optimization strategies are described.

In this work, a novel photocatalytic reactor for the pulsed and controlled excitation of the photocatalyst and the precise deposition of metallic ...

Developing Photosensitizer-Cobaloxime Hybrids for Solar-Driven H2 Production in Aqueous Aerobic Conditions

Developing photocatalytic H2 production devices is the one of the key steps for constructing a global H2-based renewable energy infrastructure. A number of photoactive assemblies have emerged where a photosensitizer and cobaloxime-based H2 production catalysts work in tandem to convert light energy into the H-H chemical bonds. However, the long-term instability of these assemblies and the need for hazardous proton sources have limited their usage. Here, in this work, we have integrated a stilbene-based organic dye into the periphery of a cobaloxime core via a distinct axial pyridine linkage. This strategy allowed us to develop a photosensitizer-catalyst hybrid structure with the same molecular framework. In this article, we have explained the detailed procedure of the synthesis of this hybrid molecule in addition to its comprehensive chemical characterization. The structural and optical studies have exhibited an intense electronic interaction between the cobaloxime core and the organic photosensitizer. The cobaloxime was active for H2 production even in the presence of water as the proton source. Here, we have developed a simple airtight system connected with an online H2 detector for the investigation of the photocatalytic activity by this hybrid complex. This photosensitizer-catalyst dyad present in the experimental setup continuously produced H2 once it was exposed in the natural sunlight. This photocatalytic H2 production by the hybrid complex was observed in aqueous/organic mixture media in the presence of a sacrificial electron donor under complete aerobic conditions. Thus, this photocatalysis measurement system along with the photosensitizer-catalyst dyad provide valuable insight for the development of next generation photocatalytic H2 production devices.

Developing Photosensitizer-Cobaloxime Hybrids for Solar-Driven H2 Production in Aqueous Aerobic Conditions

We have directly incorporated a stilbene-based organic dye into a cobaloxime core to generate a photosensitizer-catalyst dyad for photocatalytic H2 production. We have also developed a simple experimental setup for evaluating the light-driven H2 production by photocatalytic assemblies.

Developing photocatalytic H2 production devices is the one of the key steps for constructing a global H2-based renewable energy infrastructure. A number ...

Metal Oxide Heterojunction for Photocatalytic Activities

There is a significant global demand for improvements in synthesis techniques and their optimal characteristics, especially for industrial-scale applications. Sol-gel-based solution combustion synthesis (SG-SCS) is a simple method to produce ordered porous materials. In this regard, Pearson&#39;s hard and soft acids and bases theory assists in selecting host-dopant reactivity to form a proper heterojunction.
The formation of a heterojunction also changes the essential properties of the materials, improving photocatalysis via charge transfer or synergistic activities. A calcination temperature of 500 &#176;C is ideal for this process based on the results of the stability assessment via a differential thermogravimetry ratio analysis (DTG).
The nanoscale dimensions of the nanoparticles (NPs) and nanocomposites (NCs) generated were validated using X-ray diffraction and high-resolution transmission electron microscopy (HRTEM). Furthermore, the scanning electron microscopy micrographs and BET analyses confirmed the porosity nature of the materials. HRTEM, X-ray photoelectron spectroscopy, and energy-dispersive X-ray investigations established the materials composition. The study found that NCs degraded the acid orange 8 (AO8) color more efficiently than bare ZnO.

The development of a heterojunction boosts the photocatalytic activities of solution combustion synthesis, which is a time-/energy-efficient process. Advanced analytical characterization techniques were used in this protocol to evaluate the materials&#39; characteristics, and nanocomposites demonstrated improved acid orange-8 dye degradation.

A Facile Synthetic Method to Obtain Bismuth Oxyiodide Microspheres Highly Functional for the Photocatalytic Processes of Water Depuration

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