Designing a suitable photocatalyst which solve both the issues (energy and environment) always remains a challenge. Energy savings and greenhouse-effect mitigation are embryonic due to the limited fossil fuel resources and increasingly stringent requirement for the environmental protection from major greenhouse gases, including carbon dioxide (CO2), The development of an “artificial photosynthetic system” (APS) having both the analogous important structural elements and reaction features of photosynthesis to achieve solar-driven water splitting and CO2 reduction is highly challenging. Here, the visible-light (≥ 420 nm) photoconversion of CO2methane (CH4) and methanol (CH3OH) over CeO2 nanoparticles, Bi2S3 and CdV2O6 nanorods, hollow and mesoporous CdS microspheres, and their nanocomposites (Bi2S3/CeO2 nanocomposites, CdS/CeO2 core shell nanocomposites and CdS- CdV2O6 common cation heterostructure) is reported. Methane and Methanol can further be used as the fuel. It has been demonstrated that owing to the sufficiently negative conduction band (CB) potential of Chalcogenides (Bi2S3 ~ −0.58 V and CdS ~ -0.80V against standard hydrogen electrode (SHE)), Bi2S3 and CdS based photocatalysts can be utilized as efficient APS for the photoreduction of CO2 into CH4 and CH3OH under visible-light irradiation. The as-synthesized photocatalysts have further been characterized through different techniques. The phase, crystal structure, morphology, composition, optical/photoluminescence property and alignment of energy levels of the as-synthesized Chalcogenide based photocatalysts have been thoroughly studied by different techniques, such as powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption-desorption BET, ultraviolet-visible-near infrared diffuse reflectance spectroscopy (UV-Vis-NIR) and Photoluminescence (PL) spectroscopy. The efficiency of the synthesized photocatalysts has been analysed by their application for the reduction of CO2 under visible light in the presence of H2O. Combination of visible light active Bi2S3 and CdS with different metal oxide semiconductors (i.e., CeO2 and CdV2O6) owing to the formation of interface between p-type Chalcogenides and n-type oxides, visibly increases the production of solar fuelsby efficiently promoting the electron transfer from the CB of Chalcogenides (Bi2S3 and CdS) to that of metal oxides (CeO2 and CdV2O6) under visible-light irradiation. As a class of advanced composite material, core/shell structures exhibit unique chemical composition and electro chemical properties. These properties are quite promising not only fundamental but also from the technological point of view as well and improve the interfacial charge transfer process. The high yield of solar fuel (CH4 and CH3OH) is observed in case of CdS/CeO2 coreshell due to formation of close contact in coreshell like morphology.Such composite have hollow structured microspheres coreof CdS with mesoporouschannels that can facilitate efficient adsorption and activation of CO2 for successive photoconversion into CH4 and CH3OH. In addition, the CdS-CdV2O6 hybrid microstructures synthesised by limited chemical conversion rout, CdS acts more like a sensitizer as in dye-sensitized solar cells, and remarkably improves the rate of CH4 production, which is ascribed to the modification of CdS over the CdV2O6 superstructure. Better photocatalytic activity of flower like CdS-CdV2O6 common cationheterostructure than that of single photocatalyst nanocrystals, and other composites isalso attributed to suitable band alignment and common ion which suppresses the electron-hole recombination Moreover, Stability of photocatalyst is also very important along with the photocatalytic efficiency for practical application. The XRD and SEM are recorded after photoreduction and photocatalyst applied for several runs to check the stability of photocatalyst. As synthesized composites show better stability than that of single Chalcogenides. Based on the evidences from the above experiments, chalcogenide/metal oxide composites seem to be promising for the visible-light induced photocatalytic conversion of CO2 into solar fuels.
کچھ یادیں کچھ باتیں یہ اُن دنوں کی بات ہے جب میں رسمی تعلیم کے ایک مرحلے کی تکمیل کے بعد عملی زندگی میں قدم رکھنے کی جستجو میں تھا کہ میری ملاقات ایک ایسے شخص سے ہوئی جس نے زندگی میں درپیش مسائل سے نبردآزما ہونے میں بہت مدد کی اوراب بھی تادمِ تحریر اِن کے علمی و ادبی فیض سے استفادہ جاری ہے۔ جون ۱۹۹۲ئ کی بات ہے کہ خالد بھٹی (مرحوم) نے اپنے حاوی کالج میں طلباء کی خوشنویسی کی تربیت کے لیے بطور خوش نویس معلم مجھے خدمات سر انجام دینے کے لیے آمادہ کیا اور اسی سلسلہ میں ایک اشتہار ’’حاوی کالج کی فخریہ پیشکش‘‘ تدریس ِ خطاطی کی باقاعدہ کلاس کی کتابت کے لیے خالد بھٹی کے ہمراہ اِن کی رہائش گاہ پر حاضر ہوا تو دیکھا کہ ایک تیس بتیس سالہ خوش شکل، خوش رنگ ، خوش لباس ، دبلا پتلا ، باریش شخص سامان کتابت کے ساتھ اپنی مسندِ خاص پر برا جمان ہے اور جلد ہی یہ احساس بھی ہوا کہ وہ خوش اخلاق اور مہمان نواز بھی ہے۔ ازاں بعد ملاقاتوں کا سلسلہ جاری رہا۔ رب کریم کی مجھ پر کرم نوازی ہوئی کہ مارچ ۱۹۹۳ئ میں میں اُن کارفیق کا ر بن گیا اور ہم گورنمنٹ مڈل سکول نمبر ۲ میں اکٹھے رہے ۔ اُن سے رفاقت کا سلسلہ جیسے طول پکڑ تاگیا۔ اُن کی شخصیت کے ہر پہلو سے مجھے آشنائی ہوتی گئی ۔ ۱۹۶۲ئ میں عارف والا کے مضافاتی شہر چک نمبر ۳۷/ ای۔بی میں جنم لینے والا محمد اکرم جس نے ابتدائی تعلیم اپنے والدِ محترم سے حاصل کی اور محض چھ سال کی عمر میں والد کا سایہ سر سے اُٹھ گیا ۔ پھر یتیمی کی ستم ظریفی اور غریب الوطنی کی پُرخار راہوں سے گزرتے ہوئے میٹرک کا...
The Proper approach to the Quran can be described in three stages: first, receive the message of the Quran by hearing or reading it Second: understanding the message of the Quran by reflecting upon it and studying its meaning third: apply the message of the Quran by ordering your personal life as well as the life of Society according to its message. The branch of Knowledge called "Ulum al Quran" my be used as a means for the accomplishment of the second stage, understanding the message of the Quran by understanding its setting and circumstances, Muslims have from earliest times, applied themselves not only to the message from Allah. The Quran, but also to its setting and framework, and the preoccupation with these ultimately developed into the "Knowledge" about the Quran. In this paper, there are a number of matters related to the study of the Quran to which / have drawn special attention, and also highlighted
Compression of data has become a worldwide phenomenon during the past few decades for rea- son of achieving savings in band-width (BW) and hence makes it cost effective. The widespread practice of encryption of data has generated interest for many decades and it mainly aims at pro- tection of data. Combining these two apparently contrary processes (in terms of BW) is quite challenging. Whereas the research on concurrent data compression and data protection (encryp- tion) is still on, the methodology adopted by the author is unique and quite new. The most impor- tant aim of data compression technique is the need for curtailing the data storage and communi- cation expenses. The source message (long) is converted to a codeword (small). The key objec- tive of data encryption is to guard the integrity of data if it is intercepted by an eavesdropper. The plaintext is transformed in to ciphertext using an encryption key or keys. Combining the processes of compression and encryption together must be done in this order, that is, compres- sion followed by encryption because all compression techniques heavily rely on the redundancies inherently part of a regular text or speech. The speech compression has been achieved using Lempel-Ziv 78 algorithm and a new algorithm for encryption/decryption, named ―The Random- One, abbreviated as TR-1‖ is developed during this study and is thoroughly tested. The results obtained are quite encouraging. Firstly, contrary to the use of conventional methods the algo- rithm developed in this study does not use exclusive-OR (XOR) operation in Permutation (P) and Distribution (D) boxes for producing ciphertext from the plaintext. In this scheme pseudo ran- dom number (PRN) is used only to deceive the intruder by adding more confusion (meaning compared to the confusion due to the use of some tested algorithms used in this research). In fact only the sender of information and the intended recipient (not intruders) should be aware of the 44 bit positions filled by the PRN in a 128 word. The intended recipient discards these during deciphering process at the right time (these are disposed of before performing the inverse map- ping in the P-Box). Secondly, protection against attacks is further ensured by using two supple- mentary keys, one for the P-Box, and another for the D-box. In addition the routine key-set of the N selected algorithms further enhances the security. In a small set-up, the distribution of key-set can be mutually agreed upon by the users; but in a large set-up, the distribution of these sets can be accomplished using standard key distribution techniques. Moreover, the proposed algorithm- - also differs from the other methods currently in use due to deployment of a ―sentinel marker”; which is not adopted by other algorithms and this proposal is purely the brain child of the author. The sentinel marker is part of the secret key which is pre-decided and predetermined by the sender and the intended recipient of the information. Twenty bits (out of a total of 128) are used for the sentinel marker which amounts to 2^20 = 1,048,576 possibilities combined with 2^44 = 17.6 trillion possibilities of the ciphertext produced by the PRN. The job for the cryptanalyst to break this cipher becomes formidable and a fool-proof security of data is ensured.